[Emc-developers] EDM gap control

Anybody familiar with EDM who could tell me how to adjust the feed rate for EDM operations?

Nicklas Karlsson

Marius Liebenberg

2016-02-26 09:03:31 UTC

Not a very trivial task but it can be done. There is a youtube video
showing and EDM running on linuxcnc. Do a search. The problem comes in
when you have to backup as some EDM machines do.

There is a yahoo group for edm as well and they have a lot of info
there. Let me know if you dont come right I will try and send some
links.

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed rate
for EDM operations?
Nicklas Karlsson
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Nicklas Karlsson

2016-02-26 10:07:20 UTC

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed rate
for EDM operations?

Not a very trivial task but it can be done. There is a youtube video
showing and EDM running on linuxcnc. Do a search. The problem comes in
when you have to backup as some EDM machines do.

Programming I could solve. Then controlling speed and backup what do they try to achieve: A certain average gap voltage? Ignition voltage? Power in each pulse?

Nicklas Karlsson

Gene Heskett

2016-02-26 12:22:35 UTC

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed
rate for EDM operations?

Not a very trivial task but it can be done. There is a youtube video
showing and EDM running on linuxcnc. Do a search. The problem comes
in when you have to backup as some EDM machines do.

Programming I could solve. Then controlling speed and backup what do
they try to achieve: A certain average gap voltage? Ignition voltage?
Power in each pulse?

I have only used edm 3 times, in each case in blind holes. The first time
I drove it by hand from the arrow keys, but found the blind holes lack
of the electrolite fluid circulation to be a major problem as the juice
in the hole would gradually get conductive & short it out. I did get the
first broken tap removed but it was an all day job. I found also that
if the electrode was rotating at 50 to 100 revs, that induced
circulation seems to help. So I wrote a loop that drove it to a fixed
very small increment farther each time, doing g0 moves so the
electrolite was somewhat pumped in and out of the hole, and the second
busted tap was cut out in about 1/3rd of the time. But I felt the power
supply was a bit puny, so the next time I traded the 2uf capacitor out
for a 10 uf (both oil filled paper caps) and doubled the voltage to
around 75 volts while reducing the resistor from 50 ohms to 25, lots
more power per pulse.

Later, needing mounting holes in a 10" carbide tipped saw blade so I
could mount it on a rotary table to sharpen it, I used hollow brass
tubing as the electrode, rotating in the mills chuck to help circulate
the juice. With more power it was faster, but even with 29db shooting
earmuffs on, the noise was still in the 130 db area and a bit painfull.
That saw blade made a great sounding board and I expect it could be
easily heard 3 to 6 blocks away. It also drilled the cleanest holes I
have ever seen in that hard chrome plated steel.

So the importance of being able to circulate the juice to keep the
metalic debris flushed from the working area is at last as important as
the height control. As for active height control, one might be able to
use one of the thc modules for that but I've not tried it.

With very short, heavy leads between the capacitor and the workface, a
diode to rectify the peak voltage reached at the capcitor would seem to
be the measurement method of choice, but that, even with very short
leads, might need some r/c filtering because the discharge IS going to
induce some resonant ringing, likely sufficient to cause micro-arcing in
a common bulk carbon resistor, which will manifest itself as an initial
lowering of the filtering resistors measured resistance, and a drift in
the desired operating voltage until the resistor is destroyed. For the
same reason, the diode needs to be a very fast recovery diode and rated
at least to 1 kilovolt.

Not hugely helpfull Nicklas, but that is what I learned based on 65+
years of making electrons do useful work.

Post by Nicklas Karlsson
Nicklas Karlsson
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Cheers, Gene Heskett

--
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soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

Nicklas Karlsson

2016-02-26 13:10:04 UTC

I understand flushing is important but nothing about how ot adapt speed.

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed
rate for EDM operations?

Not a very trivial task but it can be done. There is a youtube video
showing and EDM running on linuxcnc. Do a search. The problem comes
in when you have to backup as some EDM machines do.

Programming I could solve. Then controlling speed and backup what do
they try to achieve: A certain average gap voltage? Ignition voltage?
Power in each pulse?

I have only used edm 3 times, in each case in blind holes. The first time
I drove it by hand from the arrow keys, but found the blind holes lack
of the electrolite fluid circulation to be a major problem as the juice
in the hole would gradually get conductive & short it out. I did get the
first broken tap removed but it was an all day job. I found also that
if the electrode was rotating at 50 to 100 revs, that induced
circulation seems to help. So I wrote a loop that drove it to a fixed
very small increment farther each time, doing g0 moves so the
electrolite was somewhat pumped in and out of the hole, and the second
busted tap was cut out in about 1/3rd of the time. But I felt the power
supply was a bit puny, so the next time I traded the 2uf capacitor out
for a 10 uf (both oil filled paper caps) and doubled the voltage to
around 75 volts while reducing the resistor from 50 ohms to 25, lots
more power per pulse.
Later, needing mounting holes in a 10" carbide tipped saw blade so I
could mount it on a rotary table to sharpen it, I used hollow brass
tubing as the electrode, rotating in the mills chuck to help circulate
the juice. With more power it was faster, but even with 29db shooting
earmuffs on, the noise was still in the 130 db area and a bit painfull.
That saw blade made a great sounding board and I expect it could be
easily heard 3 to 6 blocks away. It also drilled the cleanest holes I
have ever seen in that hard chrome plated steel.
So the importance of being able to circulate the juice to keep the
metalic debris flushed from the working area is at last as important as
the height control. As for active height control, one might be able to
use one of the thc modules for that but I've not tried it.
With very short, heavy leads between the capacitor and the workface, a
diode to rectify the peak voltage reached at the capcitor would seem to
be the measurement method of choice, but that, even with very short
leads, might need some r/c filtering because the discharge IS going to
induce some resonant ringing, likely sufficient to cause micro-arcing in
a common bulk carbon resistor, which will manifest itself as an initial
lowering of the filtering resistors measured resistance, and a drift in
the desired operating voltage until the resistor is destroyed. For the
same reason, the diode needs to be a very fast recovery diode and rated
at least to 1 kilovolt.
Not hugely helpfull Nicklas, but that is what I learned based on 65+
years of making electrons do useful work.

Cheers, Gene Heskett
--
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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Pete_Gruendeman

2016-02-26 14:06:19 UTC

Hi:Pete Gruendeman, long time EDM operator here. I have also written EDM software which went forward, backward and escaped sideways off the program path.
EDM motion is based on either:Positioning, at whatever rate you program though it's typically rather slow;or
Erosion, with no feedrate what so ever. Sparks radiate from the wire or carbon/copper electrode in all directions, eroding the workpiece where those sparks make contact. Motion forward in the programmed path is all about maintaining erosion gap voltage, and possibly current, within limits which is controlled entirely by movement of the electrode. Don't call it a feedrate because It's not a feedrate.
Read the gap voltage;If/ gap voltage > 3/4 Voc, move ahead;If/ gap voltage > 3/4 Voc && < 2/3 Voc, stay put;If/ gap voltage < 2/3 Voc, backup;repeat
All of this start, stop, backup motion will result in an average rate of travel that is on the order of inches per hour. It's not fast. Though the positioning rate for forward and reverse motion can be inches per minute.
What's really needed for useful EDM control is all of the above plus backing up on or escaping off the programmed path at timed intervals or based on erosion conditions. It's not that hard to write as I have already done it in four axis moves, linear interpolation only, no wire diameter compensation. Code or ideas sent upon request.
Pete Gruendeman

On Friday, February 26, 2016 7:10 AM, Nicklas Karlsson <***@gmail.com> wrote:

I understand flushing is important but nothing about how ot adapt speed.

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed
rate for EDM operations?

Not a very trivial task but it can be done. There is a youtube video
showing and EDM running on linuxcnc. Do a search. The problem comes
in when you have to backup as some EDM machines do.

Programming I could solve. Then controlling speed and backup what do
they try to achieve: A certain average gap voltage? Ignition voltage?
Power in each pulse?

I have only used edm 3 times, in each case in blind holes. The first time
I drove it by hand from the arrow keys, but found the blind holes lack
of the electrolite fluid circulation to be a major problem as the juice
in the hole would gradually get conductive & short it out. I did get the
first broken tap removed but it was an all day job. I found also that
if the electrode was rotating at 50 to 100 revs, that induced
circulation seems to help. So I wrote a loop that drove it to a fixed
very small increment farther each time, doing g0 moves so the
electrolite was somewhat pumped in and out of the hole, and the second
busted tap was cut out in about 1/3rd of the time. But I felt the power
supply was a bit puny, so the next time I traded the 2uf capacitor out
for a 10 uf (both oil filled paper caps) and doubled the voltage to
around 75 volts while reducing the resistor from 50 ohms to 25, lots
more power per pulse.
Later, needing mounting holes in a 10" carbide tipped saw blade so I
could mount it on a rotary table to sharpen it, I used hollow brass
tubing as the electrode, rotating in the mills chuck to help circulate
the juice. With more power it was faster, but even with 29db shooting
earmuffs on, the noise was still in the 130 db area and a bit painfull.
That saw blade made a great sounding board and I expect it could be
easily heard 3 to 6 blocks away. It also drilled the cleanest holes I
have ever seen in that hard chrome plated steel.
So the importance of being able to circulate the juice to keep the
metalic debris flushed from the working area is at last as important as
the height control. As for active height control, one might be able to
use one of the thc modules for that but I've not tried it.
With very short, heavy leads between the capacitor and the workface, a
diode to rectify the peak voltage reached at the capcitor would seem to
be the measurement method of choice, but that, even with very short
leads, might need some r/c filtering because the discharge IS going to
induce some resonant ringing, likely sufficient to cause micro-arcing in
a common bulk carbon resistor, which will manifest itself as an initial
lowering of the filtering resistors measured resistance, and a drift in
the desired operating voltage until the resistor is destroyed. For the
same reason, the diode needs to be a very fast recovery diode and rated
at least to 1 kilovolt.
Not hugely helpfull Nicklas, but that is what I learned based on 65+
years of making electrons do useful work.

Nicklas Karlsson

2016-02-26 14:59:37 UTC

Thanks.

I start with Z-motion only and try to control distance to keep discharge voltage at 29 volt. Then this work it is time for optimal paramers and other directions.

Regards Nicklas Karlsson

On Fri, 26 Feb 2016 14:06:19 +0000 (UTC)

Post by Pete_Gruendeman
Hi:Pete Gruendeman, long time EDM operator here. I have also written EDM software which went forward, backward and escaped sideways off the program path.
EDM motion is based on either:Positioning, at whatever rate you program though it's typically rather slow;or
Erosion, with no feedrate what so ever. Sparks radiate from the wire or carbon/copper electrode in all directions, eroding the workpiece where those sparks make contact. Motion forward in the programmed path is all about maintaining erosion gap voltage, and possibly current, within limits which is controlled entirely by movement of the electrode. Don't call it a feedrate because It's not a feedrate.
Read the gap voltage;If/ gap voltage > 3/4 Voc, move ahead;If/ gap voltage > 3/4 Voc && < 2/3 Voc, stay put;If/ gap voltage < 2/3 Voc, backup;repeat
All of this start, stop, backup motion will result in an average rate of travel that is on the order of inches per hour. It's not fast. Though the positioning rate for forward and reverse motion can be inches per minute.
What's really needed for useful EDM control is all of the above plus backing up on or escaping off the programmed path at timed intervals or based on erosion conditions. It's not that hard to write as I have already done it in four axis moves, linear interpolation only, no wire diameter compensation. Code or ideas sent upon request.
Pete Gruendeman
I understand flushing is important but nothing about how ot adapt speed.

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed
rate for EDM operations?

Not a very trivial task but it can be done. There is a youtube video
showing and EDM running on linuxcnc. Do a search. The problem comes
in when you have to backup as some EDM machines do.

Programming I could solve. Then controlling speed and backup what do
they try to achieve: A certain average gap voltage? Ignition voltage?
Power in each pulse?

I have only used edm 3 times, in each case in blind holes. The first time
I drove it by hand from the arrow keys, but found the blind holes lack
of the electrolite fluid circulation to be a major problem as the juice
in the hole would gradually get conductive & short it out. I did get the
first broken tap removed but it was an all day job. I found also that
if the electrode was rotating at 50 to 100 revs, that induced
circulation seems to help. So I wrote a loop that drove it to a fixed
very small increment farther each time, doing g0 moves so the
electrolite was somewhat pumped in and out of the hole, and the second
busted tap was cut out in about 1/3rd of the time. But I felt the power
supply was a bit puny, so the next time I traded the 2uf capacitor out
for a 10 uf (both oil filled paper caps) and doubled the voltage to
around 75 volts while reducing the resistor from 50 ohms to 25, lots
more power per pulse.
Later, needing mounting holes in a 10" carbide tipped saw blade so I
could mount it on a rotary table to sharpen it, I used hollow brass
tubing as the electrode, rotating in the mills chuck to help circulate
the juice. With more power it was faster, but even with 29db shooting
earmuffs on, the noise was still in the 130 db area and a bit painfull.
That saw blade made a great sounding board and I expect it could be
easily heard 3 to 6 blocks away. It also drilled the cleanest holes I
have ever seen in that hard chrome plated steel.
So the importance of being able to circulate the juice to keep the
metalic debris flushed from the working area is at last as important as
the height control. As for active height control, one might be able to
use one of the thc modules for that but I've not tried it.
With very short, heavy leads between the capacitor and the workface, a
diode to rectify the peak voltage reached at the capcitor would seem to
be the measurement method of choice, but that, even with very short
leads, might need some r/c filtering because the discharge IS going to
induce some resonant ringing, likely sufficient to cause micro-arcing in
a common bulk carbon resistor, which will manifest itself as an initial
lowering of the filtering resistors measured resistance, and a drift in
the desired operating voltage until the resistor is destroyed. For the
same reason, the diode needs to be a very fast recovery diode and rated
at least to 1 kilovolt.
Not hugely helpfull Nicklas, but that is what I learned based on 65+
years of making electrons do useful work.

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TJoseph Powderly

2016-02-26 15:15:38 UTC

good going nicklaus!
many experienced operator never see the relation of setpoint and 'smooth'
but beware, too smooth is sluggish, so jab a screwdriver in the gap
during tests
to make sure the system immediately retracts.

the setpoint for graphite to steel for positive polarity is
29 to 32 volts ( 29 for large average currents, 32 for tiny )
its different for copper to steel
copper to wolfram
steel to steel
the german reseach call this 'paarung'
the anode & cathode pairing determines the setpoint

please look at the ISEM and JSEM journals for info

it is handy to use 2 scope traces
1 on the process variable
1 on the velocity command to the single axis ( your case)

they should track each other tightly

tomp

Post by Nicklas Karlsson
Thanks.
I start with Z-motion only and try to control distance to keep discharge voltage at 29 volt. Then this work it is time for optimal paramers and other directions.
Regards Nicklas Karlsson
On Fri, 26 Feb 2016 14:06:19 +0000 (UTC)

Hi:Pete Gruendeman, long time EDM operator here. I have also written EDM software which went forward, backward and escaped sideways off the program path.
EDM motion is based on either:Positioning, at whatever rate you program though it's typically rather slow;or
Erosion, with no feedrate what so ever. Sparks radiate from the wire or carbon/copper electrode in all directions, eroding the workpiece where those sparks make contact. Motion forward in the programmed path is all about maintaining erosion gap voltage, and possibly current, within limits which is controlled entirely by movement of the electrode. Don't call it a feedrate because It's not a feedrate.
Read the gap voltage;If/ gap voltage > 3/4 Voc, move ahead;If/ gap voltage > 3/4 Voc && < 2/3 Voc, stay put;If/ gap voltage < 2/3 Voc, backup;repeat
All of this start, stop, backup motion will result in an average rate of travel that is on the order of inches per hour. It's not fast. Though the positioning rate for forward and reverse motion can be inches per minute.
What's really needed for useful EDM control is all of the above plus backing up on or escaping off the programmed path at timed intervals or based on erosion conditions. It's not that hard to write as I have already done it in four axis moves, linear interpolation only, no wire diameter compensation. Code or ideas sent upon request.
Pete Gruendeman
I understand flushing is important but nothing about how ot adapt speed.

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed
rate for EDM operations?

Not a very trivial task but it can be done. There is a youtube video
showing and EDM running on linuxcnc. Do a search. The problem comes
in when you have to backup as some EDM machines do.

Programming I could solve. Then controlling speed and backup what do
they try to achieve: A certain average gap voltage? Ignition voltage?
Power in each pulse?

I have only used edm 3 times, in each case in blind holes. The first time
I drove it by hand from the arrow keys, but found the blind holes lack
of the electrolite fluid circulation to be a major problem as the juice
in the hole would gradually get conductive & short it out. I did get the
first broken tap removed but it was an all day job. I found also that
if the electrode was rotating at 50 to 100 revs, that induced
circulation seems to help. So I wrote a loop that drove it to a fixed
very small increment farther each time, doing g0 moves so the
electrolite was somewhat pumped in and out of the hole, and the second
busted tap was cut out in about 1/3rd of the time. But I felt the power
supply was a bit puny, so the next time I traded the 2uf capacitor out
for a 10 uf (both oil filled paper caps) and doubled the voltage to
around 75 volts while reducing the resistor from 50 ohms to 25, lots
more power per pulse.
Later, needing mounting holes in a 10" carbide tipped saw blade so I
could mount it on a rotary table to sharpen it, I used hollow brass
tubing as the electrode, rotating in the mills chuck to help circulate
the juice. With more power it was faster, but even with 29db shooting
earmuffs on, the noise was still in the 130 db area and a bit painfull.
That saw blade made a great sounding board and I expect it could be
easily heard 3 to 6 blocks away. It also drilled the cleanest holes I
have ever seen in that hard chrome plated steel.
So the importance of being able to circulate the juice to keep the
metalic debris flushed from the working area is at last as important as
the height control. As for active height control, one might be able to
use one of the thc modules for that but I've not tried it.
With very short, heavy leads between the capacitor and the workface, a
diode to rectify the peak voltage reached at the capcitor would seem to
be the measurement method of choice, but that, even with very short
leads, might need some r/c filtering because the discharge IS going to
induce some resonant ringing, likely sufficient to cause micro-arcing in
a common bulk carbon resistor, which will manifest itself as an initial
lowering of the filtering resistors measured resistance, and a drift in
the desired operating voltage until the resistor is destroyed. For the
same reason, the diode needs to be a very fast recovery diode and rated
at least to 1 kilovolt.
Not hugely helpfull Nicklas, but that is what I learned based on 65+
years of making electrons do useful work.

Nicklas Karlsson

2016-03-02 10:12:02 UTC

Post by Pete_Gruendeman
...
All of this start, stop, backup motion will result in an average rate of travel that is on the order of inches per hour. It's not fast. Though the positioning rate for forward and reverse motion can be inches per minute.
...

TJoseph Powderly

2016-03-02 15:29:10 UTC

Nicklaus hello
even tho the average velocity is low
it is important to move to the correct position as soon as possible
if the tool is too close
it will cause thousands of bad discharges per second
and damage the stock
( velocity is NOT important, position IS important)
if the tool is too far away
then many pulses will not occur
wasting time in a process that is already slow
too close is -1 or 2 microns
too far is + 1 or 2 microns
more positional error is just bad control

MRR is metal removal rate
measured in grains per minute or grains per hour

the finer the finish the slower the MRR
MRR is higher with rougher surface, lower with finer
Vw is VerschleissWerkstuffe or loss of workpeice
Ve is VerschleissElekgtrode or loss of tool

Vw is high for roughing (schruppen) and Ve is low for roughing
Ve is high for finishing ( schlicten) and Vw is low for finishing

there is a point where it is advantageous to reverse the polarity to get
better Vw an Ve
This point is related mostly to on time and D%, not current ( tho this
point is usually at low currents)

back to your post...
yes the velocity is slow
no the position update should not be slow

run the position update as fast as you can
even use hardware to update the motor amplifier and only let Linuxcnc
monitor postion
just to make the position loop as fast as possible

tomp

...
All of this start, stop, backup motion will result in an average rate of travel that is on the order of inches per hour. It's not fast. Though the positioning rate for forward and reverse motion can be inches per minute.
...

Then it is so slow as at maximum inches per minute there is no point with position/velocity loop faster than once each millisecond?
For Z-axis there would be no problem with 40kHz servo loop if needed.
Regards Nicklas Karlsson
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TJoseph Powderly

2016-02-26 14:53:35 UTC

traditional edm gap control as developed by the Lazerenko's is based of
maintaining a gap voltage.

* non-traditional ( in the niche of EDM ) can be ignition delay based,
current exchange
* or a hybrid ( see JSEM journals the japanese journals or ISEM for
the rest of the EDM world

or google 'gap control' to see other forms of cnc not based on 'be at
predicted position at specific time'

( linuxcnc is position based on time&velocity,
edm is position based on THE chosen process feedback
you can choose the process variable you like to use )

to truly use a process control scheme in linuxcnc requires a huge
re-write imo
to hack some motion that follows the process variable is not difficult,
but (imop) lies in HAL not in the linuxcnc motion module.

edm Anybody familiar with EDM who could tell me how to adjust the feed rate
for EDM operations?

Not a very trivial task but it can be done. There is a youtube video
showing and EDM running on linuxcnc. Do a search. The problem comes in
when you have to backup as some EDM machines do.

Programming I could solve. Then controlling speed and backup what do they try to achieve: A certain average gap voltage? Ignition voltage? Power in each pulse?
Nicklas Karlsson
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andy pugh

2016-02-26 09:56:47 UTC

On 26 February 2016 at 07:34, Nicklas Karlsson

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed rate for EDM operations?

There is a motion.adaptive-feed pin that can control the feed-rate
according to an input to HAL. You would use this.

You might want to look at the experimental reverse-run branch, which
allows negative values in the adaptive feed and in that case runs
backwards through the G-code.

--
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

EBo

2016-02-26 13:06:15 UTC

Post by andy pugh
On 26 February 2016 at 07:34, Nicklas Karlsson

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed
rate for EDM operations?

There is a motion.adaptive-feed pin that can control the feed-rate
according to an input to HAL. You would use this.
You might want to look at the experimental reverse-run branch, which
allows negative values in the adaptive feed and in that case runs
backwards through the G-code.

Can the reverse feed traverse more than a single G-code, or just to the
begining of the current (no pun intended)?

EBo --

s***@empirescreen.com

2016-02-26 13:23:53 UTC

I think it is 100 lines.

On Fri, 26 Feb 2016 06:06:15 -0700

Post by andy pugh
On 26 February 2016 at 07:34, Nicklas Karlsson

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed
rate for EDM operations?

There is a motion.adaptive-feed pin that can control the feed-rate
according to an input to HAL. You would use this.
You might want to look at the experimental reverse-run branch, which
allows negative values in the adaptive feed and in that case runs
backwards through the G-code.

Can the reverse feed traverse more than a single G-code, or just to the
begining of the current (no pun intended)?
EBo --
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Sarah Armstrong

2016-02-26 13:48:16 UTC

any example hal files,showing how to set up etc ,
i'd like to try this

Post by s***@empirescreen.com
http://youtu.be/3aYaHxT6ZnQ
I think it is 100 lines.
On Fri, 26 Feb 2016 06:06:15 -0700

Post by andy pugh
On 26 February 2016 at 07:34, Nicklas Karlsson

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed
rate for EDM operations?

There is a motion.adaptive-feed pin that can control the feed-rate
according to an input to HAL. You would use this.
You might want to look at the experimental reverse-run branch, which
allows negative values in the adaptive feed and in that case runs
backwards through the G-code.

Can the reverse feed traverse more than a single G-code, or just to the
begining of the current (no pun intended)?
EBo --

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Post by EBo
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TJoseph Powderly

2016-02-26 15:06:18 UTC

adaptive feed slows down till the velocity does not overshoot the
removal rate
that aint edm, thats following the slow truck in the slow lane

reversal aint what edm is about unless things are near fatally bad.

the normal motion in edm is a jiggly motion that on-the-average moves
towards a destination.

its jiggly because the correct position varies constantly,
the correct position is forward and backward of the present position
on a micro or miliisecond basis.

path reversal is in seconds not fractions.

path reversal is what you do when things are WRONG
path reversal is not how you move to the correct position.

path reversal is like air bags in a car,
so path reversal is not about good motion control
its fire prevention,
no its the fire department.
it's way after the control system failed.

tomp

Post by andy pugh
On 26 February 2016 at 07:34, Nicklas Karlsson

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed rate for EDM operations?

There is a motion.adaptive-feed pin that can control the feed-rate
according to an input to HAL. You would use this.
You might want to look at the experimental reverse-run branch, which
allows negative values in the adaptive feed and in that case runs
backwards through the G-code.

Pete_Gruendeman

2016-02-26 15:25:34 UTC

Hi Tom:> path reversal is what you do when things are WRONG

path reversal is not how you move to the correct position. These statements are true for wire EDM but not for sinker. There are many reasons to back out with sinker, including timed retraction before the erosion gap is contaminated or forced retraction after the gap is contaminated. That retraction can be along the programmed path but is more often escaping toward a fixed point or in a specified direction. Escaping off the program path is the essential part, not just backup up and dragging the electrode through the contamination bits.

I repeat: This is for sinker, Not wire.
Pete Gruendeman

On Friday, February 26, 2016 9:06 AM, TJoseph Powderly <***@gmail.com> wrote:

adaptive feed slows down till the velocity does not overshoot the
removal rate
that aint edm, thats following the slow truck in the slow lane

reversal aint what edm is about unless things are near fatally bad.

the normal motion in edm is a jiggly motion that on-the-average moves
towards a destination.

its jiggly because the correct position varies constantly,
the correct position is forward and backward of the present position
on a micro or miliisecond basis.

path reversal is in seconds not fractions.

path reversal is what you do when things are WRONG
path reversal is not how you move to the correct position.

path reversal is like air bags in a car,
so path reversal is not about good motion control
its fire prevention,
no its the fire department.
it's way after the control system failed.

tomp

On 26 February 2016 at 07:34, Nicklas Karlsson

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed rate for EDM operations?

There is a motion.adaptive-feed pin that can control the feed-rate
according to an input to HAL. You would use this.
You might want to look at the experimental reverse-run branch, which
allows negative values in the adaptive feed and in that case runs
backwards through the G-code.

TJoseph Powderly

2016-02-26 15:37:03 UTC

hi pete i wasnt adressing your comments
yeah i agree sink edm 'escapes' not 'reverses'

imo:
hole poppers reverse toward the start point
sinkers escape to a safe point
wedm reverses along the previous path ( usually )
edm grinding , well, i never saw it reverse really not on AGie nor Elox
edm grinders
thats my experience
tomp

Post by Pete_Gruendeman
Hi Tom:> path reversal is what you do when things are WRONG

I repeat: This is for sinker, Not wire.
Pete Gruendeman
adaptive feed slows down till the velocity does not overshoot the
removal rate
that aint edm, thats following the slow truck in the slow lane
reversal aint what edm is about unless things are near fatally bad.
the normal motion in edm is a jiggly motion that on-the-average moves
towards a destination.
its jiggly because the correct position varies constantly,
the correct position is forward and backward of the present position
on a micro or miliisecond basis.
path reversal is in seconds not fractions.
path reversal is what you do when things are WRONG
path reversal is not how you move to the correct position.
path reversal is like air bags in a car,
so path reversal is not about good motion control
its fire prevention,
no its the fire department.
it's way after the control system failed.
tomp

On 26 February 2016 at 07:34, Nicklas Karlsson

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed rate for EDM operations?

There is a motion.adaptive-feed pin that can control the feed-rate
according to an input to HAL. You would use this.
You might want to look at the experimental reverse-run branch, which
allows negative values in the adaptive feed and in that case runs
backwards through the G-code.

andy pugh

2016-02-26 16:02:57 UTC

Post by TJoseph Powderly
the normal motion in edm is a jiggly motion that on-the-average moves
towards a destination.

Yes, but with bidirectional adaptive feed based on a process variable,
that it what you will get.

--
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

TJoseph Powderly

2016-02-27 00:40:22 UTC

i didnt know the linuxcnc adaptive feed rate was bidirectional
mydynac's tests were just slow down, ditto for ray henry
my bad
thanks andy
tomp

Post by TJoseph Powderly
the normal motion in edm is a jiggly motion that on-the-average moves
towards a destination.

Yes, but with bidirectional adaptive feed based on a process variable,
that it what you will get.

andy pugh

2016-02-27 00:45:07 UTC

Post by TJoseph Powderly
i didnt know the linuxcnc adaptive feed rate was bidirectional

It isn't in the released versions, but there is a demo branch with
bidirectional adaptive feed.

--
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

TJoseph Powderly

2016-02-27 00:51:10 UTC

wow! thanks andy will look for it. really a big thing for me.
+++many beers for andy

Post by TJoseph Powderly
i didnt know the linuxcnc adaptive feed rate was bidirectional

It isn't in the released versions, but there is a demo branch with
bidirectional adaptive feed.

EBo

2016-02-27 03:33:46 UTC

Post by TJoseph Powderly
i didnt know the linuxcnc adaptive feed rate was bidirectional

It isn't in the released versions, but there is a demo branch with
bidirectional adaptive feed.

cool! I/we may need to make sure that we know which repositories.
This is rather cool! As a note, I have a use that has nothing to do
with EDM's...

Thanks again,

EBo --

andy pugh

2016-02-27 03:44:19 UTC

Post by EBo
cool! I/we may need to make sure that we know which repositories.

http://git.linuxcnc.org/gitweb?p=linuxcnc.git;a=shortlog;h=refs/heads/feature/reverse-run-master2

Nothing at all to do with me, all Rob Elllenberg's work. I just saw
him announce it.

--
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

Marius Liebenberg

2016-02-26 14:33:01 UTC

Karl
Speed control is normally a direct function of a current setpoint in the
PWM controller. EDM power supplies look at every single pulse to
determine if the current and voltage is within a specified range. The
quality of the cut is partly a function of the speed and the energy in
every pulse.
So the control of the speed is integrated with the power management or
power supply controller.

------ Original Message ------
From: "Nicklas Karlsson" <***@gmail.com>
To: "EMC developers" <emc-***@lists.sourceforge.net>
Sent: 2016-02-26 15:10:04
Subject: Re: [Emc-developers] EDM gap control (Control parameters)

Post by Nicklas Karlsson
I understand flushing is important but nothing about how ot adapt
speed.

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the

feed

Post by Nicklas Karlsson
rate for EDM operations?

Not a very trivial task but it can be done. There is a youtube

video

Post by Marius Liebenberg
showing and EDM running on linuxcnc. Do a search. The problem

comes

Post by Marius Liebenberg
in when you have to backup as some EDM machines do.

Programming I could solve. Then controlling speed and backup what

Post by Nicklas Karlsson
they try to achieve: A certain average gap voltage? Ignition

voltage?

Post by Nicklas Karlsson
Power in each pulse?

I have only used edm 3 times, in each case in blind holes. The first
time
I drove it by hand from the arrow keys, but found the blind holes
lack
of the electrolite fluid circulation to be a major problem as the
juice
in the hole would gradually get conductive & short it out. I did get
the
first broken tap removed but it was an all day job. I found also
that
if the electrode was rotating at 50 to 100 revs, that induced
circulation seems to help. So I wrote a loop that drove it to a
fixed
very small increment farther each time, doing g0 moves so the
electrolite was somewhat pumped in and out of the hole, and the
second
busted tap was cut out in about 1/3rd of the time. But I felt the
power
supply was a bit puny, so the next time I traded the 2uf capacitor
out
for a 10 uf (both oil filled paper caps) and doubled the voltage to
around 75 volts while reducing the resistor from 50 ohms to 25, lots
more power per pulse.
Later, needing mounting holes in a 10" carbide tipped saw blade so I
could mount it on a rotary table to sharpen it, I used hollow brass
tubing as the electrode, rotating in the mills chuck to help
circulate
the juice. With more power it was faster, but even with 29db
shooting
earmuffs on, the noise was still in the 130 db area and a bit
painfull.
That saw blade made a great sounding board and I expect it could be
easily heard 3 to 6 blocks away. It also drilled the cleanest holes
I
have ever seen in that hard chrome plated steel.
So the importance of being able to circulate the juice to keep the
metalic debris flushed from the working area is at last as important
as
the height control. As for active height control, one might be able
to
use one of the thc modules for that but I've not tried it.
With very short, heavy leads between the capacitor and the workface,
a
diode to rectify the peak voltage reached at the capcitor would seem
to
be the measurement method of choice, but that, even with very short
leads, might need some r/c filtering because the discharge IS going
to
induce some resonant ringing, likely sufficient to cause micro-arcing
in
a common bulk carbon resistor, which will manifest itself as an
initial
lowering of the filtering resistors measured resistance, and a drift
in
the desired operating voltage until the resistor is destroyed. For
the
same reason, the diode needs to be a very fast recovery diode and
rated
at least to 1 kilovolt.
Not hugely helpfull Nicklas, but that is what I learned based on 65+
years of making electrons do useful work.

Post by Nicklas Karlsson
Nicklas Karlsson

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TJoseph Powderly

2016-02-26 14:38:13 UTC

nicklaus
there is NO feedrate for edm
period!
the process determines the correct position
the control system should move to the correct position as fast as possible
the correct position should be close if the control system is at all
adequate for edm

there is NO feedrate for edm

tomp
40+ years in EDM design repair and modification

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed rate for EDM operations?
Nicklas Karlsson
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EBo

2016-02-26 15:29:21 UTC

Thanks for the info. Out of curiosity, when starting a new cut, how
does the conventional EDM move onto the part? The equivalent of a G0
might be fast enough that by the time it senses that it has touched the
part, you could be moving fast enough to break the tool or wire. So, do
you do a slow G1 onto the part, and then G1 fast, or G0 through the
part? Just curious. I have never run a commercial EDM before.

Post by TJoseph Powderly
nicklaus
there is NO feedrate for edm
period!
the process determines the correct position
the control system should move to the correct position as fast as possible
the correct position should be close if the control system is at all
adequate for edm
there is NO feedrate for edm
tomp
40+ years in EDM design repair and modification

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed
rate for EDM operations?
Nicklas Karlsson
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Pete_Gruendeman

2016-02-26 15:40:40 UTC

At the start of a cut the machine moves at a positioning rate, reading the gap voltage, and possibly current, watching for when the signal indicates that it is close enough to the workpiece to stop moving. This is the same algorithm whether the electrode is 5cm away or 0.002mm away. It's all about keeping the erosion conditions within the specified range, regardless of how far away the workpiece is. While the voltage is > high limit, the keep moving.
Agie used to (and likely still does) support a rapid traverse mode where it moved at X-speed without monitoring the gap conditions. They called it motion with crash detection turned off. The only time I ever moved with crash detection turned off was when retracting from a cavity. Otherwise every move was in erosion mode, regardless of distance. It always works if you're not already stuck in a cavity.
Pete

On Friday, February 26, 2016 9:29 AM, EBo <***@users.sourceforge.net> wrote:

Thanks for the info. Out of curiosity, when starting a new cut, how
does the conventional EDM move onto the part? The equivalent of a G0
might be fast enough that by the time it senses that it has touched the
part, you could be moving fast enough to break the tool or wire. So, do
you do a slow G1 onto the part, and then G1 fast, or G0 through the
part? Just curious. I have never run a commercial EDM before.

Post by Nicklas Karlsson
Anybody familiar with EDM who could tell me how to adjust the feed
rate for EDM operations?
Nicklas Karlsson
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Robert - Innovative-RC

2016-02-27 13:19:32 UTC

If Any one is in the UK and wants to see how EDM works first hand...
i would be willing to show them and also give them a good run down on
the process.

we have Manual and CNC EDM so can show how both work etc.

on CNC to exscape we have to program a escape profile.. so no clearver
backup process etc
im not so sure how newer machines escape but id guess the same kind of way.
only when doing undercuts and gates you need to scape in a set path.

we mainly use our EDM for mold making with Copper to steel but have
charts for for everything.

we do not have Wire so sorry cant show that

rob

Pete_Gruendeman

2016-03-02 14:05:05 UTC

Hi Nicklas:
Correct that looping once per millisecond is definitely fast enough. On my machine, 40,000 encoder counts = 1 inch. Spark lengths, even for finishing operations are 0.001" or longer, or 40 encoder counts to go from first spark to the electrode making physical contact and that's in 1/25th of a second. That's not a problem if the machine is moving at 2- 4 inches per minute. At 4 IPM, coming to a stop in 0.001 inches requires an acceleration of -0.01852 feet per second squared or -0.00058 g's of acceleration. No problem.

The other axes would be the same in that gap voltage/current measurement at 1,000 times per second is plenty fast enough. In fact, the program I wrote upon detection of gap voltage too low waits on location for 10 milliseconds and then checks again as often the situation of the electrode being too close clears itself in that much time. I didn't differentiate between gap voltage being too low and it being zero (physical contact). If I did, then the signal to back out should have been given without any delay.

Pete Gruendeman

--------------------------------------------
On Wed, 3/2/16, Nicklas Karlsson <***@gmail.com> wrote:

Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: "Pete_Gruendeman" <***@att.net>, "EMC developers" <emc-***@lists.sourceforge.net>
Date: Wednesday, March 2, 2016, 4:12 AM

Post by Pete_Gruendeman
...
All of this start, stop, backup motion

will result in an average rate of travel that is on the
order of inches per hour. It's not fast. Though the
positioning rate for forward and reverse motion can be
inches per minute.

TJoseph Powderly

2016-03-03 04:53:36 UTC

sorry Pete
I disagree, any time spent in the wrong position is time spent making
bad discharges
which can damage surface by overheating
or
spend time throwing snowballs that fall short of hitting the target
imo, update postion as fast as possible
the average velocity ( a RESULT) will be low
but the process will be more stabile and the surface will not be hard
and crusty
abd the time will be lower
oops power fail in ChiangMai
ttyl8r
tomp

Post by Pete_Gruendeman
Correct that looping once per millisecond is definitely fast enough. On my machine, 40,000 encoder counts = 1 inch. Spark lengths, even for finishing operations are 0.001" or longer, or 40 encoder counts to go from first spark to the electrode making physical contact and that's in 1/25th of a second. That's not a problem if the machine is moving at 2- 4 inches per minute. At 4 IPM, coming to a stop in 0.001 inches requires an acceleration of -0.01852 feet per second squared or -0.00058 g's of acceleration. No problem.
The other axes would be the same in that gap voltage/current measurement at 1,000 times per second is plenty fast enough. In fact, the program I wrote upon detection of gap voltage too low waits on location for 10 milliseconds and then checks again as often the situation of the electrode being too close clears itself in that much time. I didn't differentiate between gap voltage being too low and it being zero (physical contact). If I did, then the signal to back out should have been given without any delay.
Pete Gruendeman
--------------------------------------------
Subject: Re: [Emc-developers] EDM gap control (Control parameters)
Date: Wednesday, March 2, 2016, 4:12 AM

Post by Pete_Gruendeman
...
All of this start, stop, backup motion

will result in an average rate of travel that is on the
order of inches per hour. It's not fast. Though the
positioning rate for forward and reverse motion can be
inches per minute.

Then it is so slow as at
maximum inches per minute there is no point with
position/velocity loop faster than once each millisecond?
For Z-axis there would be no
problem with 40kHz servo loop if needed.
Regards Nicklas Karlsson
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Gene Heskett

2016-03-03 05:38:06 UTC

Post by TJoseph Powderly
sorry Pete
I disagree, any time spent in the wrong position is time spent making
bad discharges
which can damage surface by overheating
or
spend time throwing snowballs that fall short of hitting the target
imo, update postion as fast as possible
the average velocity ( a RESULT) will be low
but the process will be more stabile and the surface will not be hard
and crusty
abd the time will be lower
oops power fail in ChiangMai
ttyl8r
tomp

One thing I have always felt needed to be asked, but don't recall seeing
it discussed, is when doing a sinker edm to imprint a carbon mold like
I've seen pix of, like engraving a relieved signature, is there an
optimum current per square, either in cm2 or in2 to design the process
to so it functions best?

And in terms of wear on the shaped carbon electrode, is there a best
current per square in terms of the metal removed vs the carbon wasted
that will prolong the electrode life vs metal removed? I've seen other
processes where optimizing one is not optimizing the other.

Or is there a better material to make the electrode from?

Post by TJoseph Powderly

Post by Pete_Gruendeman
Correct that looping once per millisecond is definitely fast
enough. On my machine, 40,000 encoder counts = 1 inch. Spark
lengths, even for finishing operations are 0.001" or longer, or 40
encoder counts to go from first spark to the electrode making
physical contact and that's in 1/25th of a second. That's not a
problem if the machine is moving at 2- 4 inches per minute. At 4
IPM, coming to a stop in 0.001 inches requires an acceleration of
-0.01852 feet per second squared or -0.00058 g's of acceleration.
No problem.
The other axes would be the same in that gap voltage/current
measurement at 1,000 times per second is plenty fast enough. In
fact, the program I wrote upon detection of gap voltage too low
waits on location for 10 milliseconds and then checks again as often
the situation of the electrode being too close clears itself in that
much time. I didn't differentiate between gap voltage being too low
and it being zero (physical contact). If I did, then the signal to
back out should have been given without any delay.
Pete Gruendeman
--------------------------------------------
Subject: Re: [Emc-developers] EDM gap control (Control parameters)
2016, 4:12 AM

Post by Pete_Gruendeman
...
All of this start, stop, backup motion

will result in an average rate of travel that is on the
order of inches per hour. It's not fast. Though the
positioning rate for forward and reverse motion can be
inches per minute.

Then it is so slow as at
maximum inches per minute there is no point with
position/velocity loop faster than once each millisecond?
For Z-axis there would be no
problem with 40kHz servo loop if needed.
Regards Nicklas Karlsson
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TJoseph Powderly

2016-03-03 06:47:27 UTC

50A/in^2
very crude rule fro Gr/St ( graphite to steel )

the 'current density' is NOT linear
maximum is near 400amperes even if area is yds^2
becasue the process is not controllable at extreme currents
and is seemingly high at very low areas 50 amps supplied to 1mm dia
bras tube
and 12 amps 'draw' seen on meter

and that rule is only for roughing ( creating net form )
not for finishing

during roughing the 'frontal area (Fp) is the governing factor
in finishing, the Peak to valley of the craters is the governing factor
for engraving graphite or copper is commonly used
the choice is oftern determined by experience

experience of... do i want a dirty shop and cheap electrodes ( graphite)
or a clean shop and expensive electrodes ( copper)

hth
tomp

Post by Gene Heskett
One thing I have always felt needed to be asked, but don't recall
seeing it discussed, is when doing a sinker edm to imprint a carbon
mold like I've seen pix of, like engraving a relieved signature, is
there an optimum current per square, either in cm2 or in2 to design
the process to so it functions best? And in terms of wear on the
shaped carbon electrode, is there a best current per square in terms
of the metal removed vs the carbon wasted that will prolong the
electrode life vs metal removed? I've seen other processes where
optimizing one is not optimizing the other. Or is there a better
material to make the electrode from?

Gene Heskett

2016-03-03 07:22:58 UTC

Post by TJoseph Powderly
50A/in^2
very crude rule fro Gr/St ( graphite to steel )

Surprisingly high, but I've very little experience.

Post by TJoseph Powderly
the 'current density' is NOT linear
maximum is near 400amperes even if area is yds^2
becasue the process is not controllable at extreme currents
and is seemingly high at very low areas 50 amps supplied to 1mm dia
bras tube
and 12 amps 'draw' seen on meter

I've not approached that.

Worst case, 75 volts dc, 25 ohms limit R, and a 10 uf oil filled cap.

Using a 1/4" od brass tube in the drill chuck, working in a clay dam
holding 1/8" deep puddle of k2 around the hole, it was painfully noisy
even with 29db rated muffs on my ears, and it cut a 1/4" diameter hole
in the center web area of a 10" circular saw blade, in perhaps 5 or 6
minutes. Beautiful holes, never ever drilled anything that cleanly
before. I had the spindle turning about 100 revs to help circulate the
k2. Spark rep rate seemed to match our 60 hz power, or 120 pps.

No clue what I was doing but it sure drilled nice holes in steel the best
drill bit would not make a mark on.

Post by TJoseph Powderly
and that rule is only for roughing ( creating net form )
not for finishing
during roughing the 'frontal area (Fp) is the governing factor
in finishing, the Peak to valley of the craters is the governing
factor for engraving graphite or copper is commonly used
the choice is oftern determined by experience
experience of... do i want a dirty shop and cheap electrodes (
graphite) or a clean shop and expensive electrodes ( copper)

Chuckle, OTOH I'd have to say the level of dirt is relative. That k2
turned into black, conductive mud & had to be changed about every 1 or 2
minutes as I'm not rigged to pump it.

Post by TJoseph Powderly
hth

Yes, its good guidance.

Post by TJoseph Powderly
tomp

Thanks TomP.>

Cheers, Gene Heskett

--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

Nicklas Karlsson

2016-03-03 07:07:16 UTC

I assume gap distance is 1µm, electrode is moved 1µm per servo period and servo period i 1kHz. In one second electrode is moved 1mm and in 60 seconds 6cm.

I assume electrode gap divided by 10 is maximum allowed movement in each servo period to get enough position accuracy. In such case maximum machining speed would be 6mm per minute but I guess it is slower in reality?

Regards Nicklas Karlsson

On Thu, 3 Mar 2016 12:53:36 +0800

Post by Pete_Gruendeman
...
All of this start, stop, backup motion

will result in an average rate of travel that is on the
order of inches per hour. It's not fast. Though the
positioning rate for forward and reverse motion can be
inches per minute.

Then it is so slow as at
maximum inches per minute there is no point with
position/velocity loop faster than once each millisecond?
For Z-axis there would be no
problem with 40kHz servo loop if needed.
Regards Nicklas Karlsson
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Pete_Gruendeman

2016-03-02 19:00:58 UTC

Hi Nicklaus and TJ:
It's true that too close is 1-2 microns for a finish burn and too far is the same. My machine resolves 40,000 encoder counts per inch so 1-2 microns works out to 1.6 to 3.2 encoder counts, which you will travel over in 1.6- 3.2 thousands of a second, fast enough I would think. Pulse rates are upwards of a few thousand per second so we're really talking about 2- 5 pulses, less on a roughing burn which has less pulses per second and longer sparks so electrode positioning is not as critical. Any machine can produce acceptable roughing burns. Only a well tuned and properly working machine can produce the finest finishes.

It's also true what TJ said about electrode wear, that it's greatest during a finish burn and lowest during a roughing burn. Negative polarity on the electrode causes greater electrode wear (other settings being the same) but that extra wear is often allowed to get acceptable erosion during difficult conditions, or when metal removal rates are more important than reducing electrode wear. Hole poppers would be an example of this -- I think, though I have not run one myself. Polarity and electrode wear are important to the EDM operator but are meaningless to the motion control software.

Pete Gruendeman

--------------------------------------------
On Wed, 3/2/16, TJoseph Powderly <***@gmail.com> wrote:

Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: "EMC developers" <emc-***@lists.sourceforge.net>
Date: Wednesday, March 2, 2016, 9:29 AM

Nicklaus hello
even tho the average velocity is low
it is important to move to the correct position
as soon as possible
if the tool is too
close
it will cause thousands of bad
discharges per second
and damage the
stock
( velocity is NOT important, position
IS important)
if the tool is too far away
then many pulses will not occur
wasting time in a process that is already
slow
too close is -1 or 2 microns
too far is + 1 or 2 microns
more positional error is just bad control

MRR is metal removal rate
measured in grains per minute or grains per
hour

the finer the finish
the slower the MRR
MRR is higher with
rougher surface, lower with finer
Vw is
VerschleissWerkstuffe or loss of workpeice
Ve is VerschleissElekgtrode or loss of
tool

Vw is high for
roughing (schruppen) and Ve is low for roughing
Ve is high for finishing ( schlicten) and Vw is
low for finishing

there is
a point where it is advantageous to reverse the polarity to
get
better Vw an Ve
This
point is related mostly to on time and D%, not current ( tho
this
point is usually at low currents)

back to your post...
yes the velocity is slow
no the
position update should not be slow

run the position update as fast as you can
even use hardware to update the motor amplifier
and only let Linuxcnc
monitor postion
just to make the position loop as fast as
possible

tomp

On 03/02/2016 06:12 PM, Nicklas Karlsson

...

All of this start, stop, backup motion will result in an
average rate of travel that is on the order of inches per
hour. It's not fast. Though the positioning rate for
forward and reverse motion can be inches per minute.

...

Then it is so

slow as at maximum inches per minute there is no point with
position/velocity loop faster than once each millisecond?

Post by Nicklas Karlsson
For Z-axis there

would be no problem with 40kHz servo loop if needed.

Post by Nicklas Karlsson
Regards Nicklas

Karlsson
------------------------------------------------------------------------------

Post by Nicklas Karlsson
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TJoseph Powderly

2016-03-03 04:56:04 UTC

re wear and polarity
sorry i tend to rant and ramble when EDM is mentioned
;-)

Post by Pete_Gruendeman
It's true that too close is 1-2 microns for a finish burn and too far is the same. My machine resolves 40,000 encoder counts per inch so 1-2 microns works out to 1.6 to 3.2 encoder counts, which you will travel over in 1.6- 3.2 thousands of a second, fast enough I would think. Pulse rates are upwards of a few thousand per second so we're really talking about 2- 5 pulses, less on a roughing burn which has less pulses per second and longer sparks so electrode positioning is not as critical. Any machine can produce acceptable roughing burns. Only a well tuned and properly working machine can produce the finest finishes.
It's also true what TJ said about electrode wear, that it's greatest during a finish burn and lowest during a roughing burn. Negative polarity on the electrode causes greater electrode wear (other settings being the same) but that extra wear is often allowed to get acceptable erosion during difficult conditions, or when metal removal rates are more important than reducing electrode wear. Hole poppers would be an example of this -- I think, though I have not run one myself. Polarity and electrode wear are important to the EDM operator but are meaningless to the motion control software.
Pete Gruendeman
--------------------------------------------
Subject: Re: [Emc-developers] EDM gap control (Control parameters)
Date: Wednesday, March 2, 2016, 9:29 AM
Nicklaus hello
even tho the average velocity is low
it is important to move to the correct position
as soon as possible
if the tool is too
close
it will cause thousands of bad
discharges per second
and damage the
stock
( velocity is NOT important, position
IS important)
if the tool is too far away
then many pulses will not occur
wasting time in a process that is already
slow
too close is -1 or 2 microns
too far is + 1 or 2 microns
more positional error is just bad control
MRR is metal removal rate
measured in grains per minute or grains per
hour
the finer the finish
the slower the MRR
MRR is higher with
rougher surface, lower with finer
Vw is
VerschleissWerkstuffe or loss of workpeice
Ve is VerschleissElekgtrode or loss of
tool
Vw is high for
roughing (schruppen) and Ve is low for roughing
Ve is high for finishing ( schlicten) and Vw is
low for finishing
there is
a point where it is advantageous to reverse the polarity to
get
better Vw an Ve
This
point is related mostly to on time and D%, not current ( tho
this
point is usually at low currents)
back to your post...
yes the velocity is slow
no the
position update should not be slow
run the position update as fast as you can
even use hardware to update the motor amplifier
and only let Linuxcnc
monitor postion
just to make the position loop as fast as
possible
tomp
On 03/02/2016 06:12 PM, Nicklas Karlsson

...

...

Then it is so

slow as at maximum inches per minute there is no point with
position/velocity loop faster than once each millisecond?

Post by Nicklas Karlsson
For Z-axis there

would be no problem with 40kHz servo loop if needed.

Post by Nicklas Karlsson
Regards Nicklas

Karlsson
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Pete_Gruendeman

2016-03-03 13:40:29 UTC

Hi:
Besides any rules of thumb for estimating current, one is always looking for the highest current that still allows stable erosion without exceeding the carrying capacity of the fluid that is carrying away the debris from the site of the erosion. If one exceeds that, then the gap gets contaminated and sparks jump from electrode to debris and then make a deeper spot in the mold cavity. And there are conditions where what amounts to re-cast can occur on the face of the electrode, building up points and other unwanted features on the electrode. I have seen this plenty of times on carbon electrodes. So-called graphite electrodes are a mixture of carbon and copper (90/10 ranging up to 50/50) sintered to make a solid. One popular trade name is Poco.

Only on rare occasions did I work with copper electrodes. They are more expensive and are somewhat of a pain to machine as copper is gummy. Poor surface finishes can be improved by polishing copper electrodes but it needs to be done carefully without imbedding non-conductive abrasives in the copper. At one time the Europeans and Japanese preferred copper electrodes and the Americans preferred carbon. Machining carbon IS messy if you are messy. If you are tidy then it's only somewhat messy.

I am seeing questions and suppositions posted here from people who seem to have never run an EDM. Questions are good but knowledge provided by others is not a substitute for the experience of running one. This is a different art form than many people in metal working are familiar with. When you can, go run an EDM; hang out with the people who do run them. With many metal cutting operations, there are lessons from one machine that transfer to another. There are commonalities between a bandsaw and a milling machine i.e. surface feet per minute of the cutting tool and chip loading. Not so with EDM. This is a different kind of animal.

Pete Gruendeman

--------------------------------------------
On Thu, 3/3/16, TJoseph Powderly <***@gmail.com> wrote:

Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: "EMC developers" <emc-***@lists.sourceforge.net>
Date: Thursday, March 3, 2016, 12:47 AM

50A/in^2
very crude rule fro Gr/St ( graphite to steel
)

the 'current
density' is NOT linear
maximum is near
400amperes even if area is yds^2
becasue the
process is not controllable at extreme currents
and is seemingly high at very low areas 50
amps supplied to 1mm dia
bras tube
and 12 amps 'draw' seen on meter

and that rule is only for
roughing ( creating net form )
not for
finishing

during roughing
the 'frontal area (Fp) is the governing factor
in finishing, the Peak to valley of the craters
is the governing factor
for engraving
graphite or copper is commonly used
the
choice is oftern determined by experience

experience of... do i want a
dirty shop and cheap electrodes ( graphite)
or a clean shop and expensive electrodes (
copper)

hth
tomp

On

Post by Gene Heskett
One thing I have always felt needed to be

asked, but don't recall

Post by Gene Heskett
seeing it

discussed, is when doing a sinker edm to imprint a carbon

Post by Gene Heskett
mold like I've seen pix of, like

engraving a relieved signature, is
there an optimum current per square, either in cm2 or in2 to
design

Post by Gene Heskett
the process to so it functions

best? And in terms of wear on the
shaped carbon electrode, is there a best current per square
in terms

Post by Gene Heskett
of the metal removed vs the

carbon wasted that will prolong the
electrode life vs metal removed? I've seen other
processes where

Post by Gene Heskett
optimizing one is not

optimizing the other. Or is there a better

Post by Gene Heskett
material to make the electrode from?

Pete_Gruendeman

2016-03-03 15:45:47 UTC

Hi again:
My comments on people getting experience with running an EDM is Not directed at any one person. It's just that this art form is so different from what most people have experienced in machine shops. Go play with one and many of these mysteries will become clearer.

Post by Gene Heskett
Or is there a better material to make the electrode from?

You'll be rich when you figure that out. Find a way to 3-D print an electrode and you'll set the world on fire. Or 3-D print the heat-treated steel mold cavity directly!
Many writers (not me because I don't know) state that electrode wear occurs at the initiation of the spark and that the wear is due to heat at the electrode surface that isn't conducted away fast enough. For those who haven't seen it, that is likely why finish electrodes/ burns have such high wear rates. They endure so very many more sparks than a roughing burn which has sparks of higher power but longer duration so there are far less of them.

Question:
Does anybody know the typical frequency or pulses per second for finishing burns? I think it's on the order of 3-5kHz but will look into it of someone doesn't already know. 40kHz servo response is very responsive but not necessary if the spark frequency is less than that.

Pete Gruendeman

--------------------------------------------
On Wed, 3/2/16, Gene Heskett <***@wdtv.com> wrote:

Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: emc-***@lists.sourceforge.net
Date: Wednesday, March 2, 2016, 11:38 PM

On Wednesday 02 March

Post by Gene Heskett
sorry Pete
I

disagree, any time spent in the wrong position is time spent
making

Post by Gene Heskett
bad discharges
which can damage surface by overheating
or
spend time

throwing snowballs that fall short of hitting the target

Post by Gene Heskett
imo, update postion as fast as possible
the average velocity ( a RESULT) will be

low

Post by Gene Heskett
but the process will be more

stabile and the surface will not be hard

Post by Gene Heskett
and crusty
abd the

time will be lower

Post by Gene Heskett
oops power fail in

ChiangMai

Post by Gene Heskett
ttyl8r

tomp

One thing I have
always felt needed to be asked, but don't recall seeing

it discussed, is when doing a sinker edm to
imprint a carbon mold like
I've seen
pix of, like engraving a relieved signature, is there an
optimum current per square, either in cm2 or
in2 to design the process
to so it
functions best?

And in
terms of wear on the shaped carbon electrode, is there a
best
current per square in terms of the
metal removed vs the carbon wasted
that
will prolong the electrode life vs metal removed? I've
seen other
processes where optimizing one
is not optimizing the other.

Or is there a better material to make the
electrode from?

Post by Gene Heskett
On
Correct that looping once per millisecond is

definitely fast
enough. On my machine, 40,000 encoder counts =
1 inch. Spark

Post by Pete_Gruendeman
lengths, even for

finishing operations are 0.001" or longer, or 40

Post by Pete_Gruendeman
encoder counts to go from first spark

to the electrode making

Post by Pete_Gruendeman
physical

contact and that's in 1/25th of a second. That's
not a

Post by Pete_Gruendeman
problem if the machine is

moving at 2- 4 inches per minute. At 4

Post by Pete_Gruendeman
IPM, coming to a stop in 0.001 inches

requires an acceleration of
-0.01852 feet per second squared or -0.00058 g's of
acceleration.

Post by Pete_Gruendeman
No problem.
The

other axes would be the same in that gap voltage/current

Post by Pete_Gruendeman
measurement at 1,000 times per second

is plenty fast enough. In

Post by Pete_Gruendeman
fact,

the program I wrote upon detection of gap voltage too low

Post by Pete_Gruendeman
waits on location for 10 milliseconds

and then checks again as often

Post by Pete_Gruendeman
the

situation of the electrode being too close clears itself in
that

Post by Pete_Gruendeman
much time. I didn't

differentiate between gap voltage being too low

Post by Pete_Gruendeman
and it being zero (physical

contact). If I did, then the signal to

Post by Pete_Gruendeman
back out should have been given

without any delay.

Post by Pete_Gruendeman
Pete Gruendeman

--------------------------------------------

Post by Pete_Gruendeman
On Wed, 3/2/16, Nicklas Karlsson

[Emc-developers] EDM gap control (Control parameters)
"Pete_Gruendeman" <***@att.net>,
"EMC developers"
Date: Wednesday, March 2,

Post by Pete_Gruendeman
2016,

4:12 AM

Post by Gene Heskett
> ...
> All of this start, stop, backup

motion

Post by Gene Heskett
will result in an average rate of travel

that is on the

Post by Pete_Gruendeman
order

of inches per hour. It's not fast. Though the

Post by Pete_Gruendeman
positioning rate for

forward and reverse motion can be

Post by Gene Heskett
inches per minute.

Post by Pete_Gruendeman
> ...

Then it is so slow as at

Post by Pete_Gruendeman
maximum inches per

minute there is no point with

Post by Gene Heskett
position/velocity loop faster than once

each millisecond?

Post by Pete_Gruendeman
For Z-axis there would

be no

Post by Pete_Gruendeman
problem with

40kHz servo loop if needed.

Post by Pete_Gruendeman
Regards Nicklas

Karlsson
--------------------------------------------------------------------

Post by Pete_Gruendeman
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Deep Visibility into Application
Performance APM + Mobile APM + RUM: Monitor 3 App instances
at just

Post by Pete_Gruendeman
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improve end-user experience.
Signup Now!

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Visibility into Application

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Performance

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Cheers, Gene
Heskett
--
"There are
four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in
that order."
-Ed Howdershelt
(Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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EBo

2016-03-03 17:20:39 UTC

Post by Pete_Gruendeman
My comments on people getting experience with running an EDM is
Not directed at any one person. It's just that this art form is so
different from what most people have experienced in machine shops.
Go
play with one and many of these mysteries will become clearer.

always good advice. Do you know one where we can go and play with one
;-)

Post by Pete_Gruendeman

Post by Gene Heskett
Or is there a better material to make the electrode from?

You'll be rich when you figure that out. Find a way to 3-D print an
electrode and you'll set the world on fire.

There are quite a number of printable conductive materials, so this
should be doable. The question is if the finish would be sufficient, or
durable. It would take me some digging, but I could probably come up
with the guys that 3D print silicon carbide. Would that work as an
electrode? How about stainless steel, copper, silver, aluminium, gold,
...

Post by Pete_Gruendeman
Or 3-D print the
heat-treated steel mold cavity directly!

EBo --

TJoseph Powderly

2016-03-04 05:27:57 UTC

e edm
base is sable2015 from taiwan
stepper
position loop control with HAL
positioning between different cuts by linuxcncse gen
real pulse generator with on off peak current
115Vdc open voltage
blah blahblah
just so you can see real edm in diy environment
https://videobin.org/+8ku/bfq.html
http://videobin.org/+6cw/786.html
http://videobin.org/+6cj/77s.html
https://videobin.org/+86p/azg.html
https://videobin.org/+8v4/brq.html
tomp
someone on this list from _posted an invite to see real edm

_

always good advice. Do you know one where we can go and play with one
;-)

Post by Pete_Gruendeman

Post by Gene Heskett
Or is there a better material to make the electrode from?

You'll be rich when you figure that out. Find a way to 3-D print an
electrode and you'll set the world on fire.

Post by Pete_Gruendeman
Or 3-D print the
heat-treated steel mold cavity directly!

I have seen, and held, 3D printed parts made from H13 tool steel, as
well as many other materials. With post processing you can get some
very good surface finishes, so this is not as crazy as it sounds.
might be fun to try some of these ideas. Anyone have an EDM that is
better than the tap burner I cobbled together out of a hotwired solenoid
and old battery -- suggested by Circuit Girl
http://youtu.be/uUN4_-xp1Wc
EBo --
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Nicklas Karlsson

2016-03-03 18:01:51 UTC

... 40kHz servo response is very responsive but not necessary if the spark frequency is less than that.
Pete Gruendeman

I have a choice between 40kHz servo thread inside driver or linuxcnc 1kHz servo thread. For z motion only choice is simple but for motion of several axis/joints for example wire EDM?

Nicklas Karlsson

Pete_Gruendeman

2016-03-03 18:31:26 UTC

Hi Nicklaus:
Someone more knowledgeable that I will need to tell us about the pulse generator frequencies that are used under various burn conditions. I am of the opinion that the servo response does not need to be faster than that pulse frequency.

Can you tell us what costs are of servo control at 1kHz and 40 kHz? Hardware or processor time costs?; proprietary versus public domain software?

While sinker EDM primarily uses Z motion, it is by no means exclusively Z motion. Many projects use the other axes, either part of the time or all of the time. The motion control for all the axes needs to be equally responsive as long as one or more users operate on more than the Z axis. AFIK Z-axis only motion is appropriate for hole popping EDMs.

Pete Gruendeman

--------------------------------------------
On Thu, 3/3/16, Nicklas Karlsson <***@gmail.com> wrote:

Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: "Pete_Gruendeman" <***@att.net>, "EMC developers" <emc-***@lists.sourceforge.net>
Date: Thursday, March 3, 2016, 12:01 PM

... 40kHz servo

response is very responsive but not necessary if the spark
frequency is less than that.

Pete

Pete_Gruendeman

2016-03-06 18:13:42 UTC

Hi Nicklas:
I am not seeing any response on this forum regarding the erosion pulse frequency.

Several hundred thousand sparks occur per second...

and in Ben Fleming's book on pulse type EDM, he shows frequencies that range from 2.5kHz up to 40kHz for finishing burns.

It's not yet clear to me that the servo response needs to be fast enough to respond to every spark. It might be helpful here if I described some of the basics of the process, based on personal experience and more so based on others' info, sources unknown.
The EDM process removes metal by superheating it with electrical sparks, and the collapse of said spark which per some authors blows out part of the metal.
The rapidly cooled workpiece surface becomes very hard and the surface finish is not particularly integral. This is commonly called a re-cast layer.
The sparks while underway have very little resistance as measured in ohms.
The electrical supply must be stopped periodically (square wave or other) so the present arc extinguishes and the next spark initiates at the next closest point between electrode and workpiece. That spark path could include bits of metal (called swarf) that have been blown out previously, resulting in a longer arc path and unstable erosion. Flushing is important to minimize or eliminate these alternate spark paths.
The electrode advances (sinks) in a manner that is nearly the same as a bridge support caisson being sunk into a riverbed. The workers remove whatever is in the way to allow the caisson to descend through the mud, gravel and boulders down to and into the bedrock. See:
https://en.wikipedia.org/wiki/Caisson_(engineering)
<end of process particulars>

Each spark or pulse will vary from the one following and the one preceding it. My experience suggests that a little averaging is not a bad thing, in order to keep the process from hunting constantly. This could be mathematical averaging of erosion gap voltages or it might be a lower servo response frequency or other solution. Also backlash and machine elasticity needs to be considered. Even with a 40kHz servo response, the electrode to workpiece gap is not likely to change at 40kHz.
TJ pointed reminded us that EDM is a very slow process. Whether it is 99% of optimal or 99.99% of optimal won't change the burn times by much. If the cost of 40kHz servo response on four axes is excessive and 1kHz servo response is reasonable then I say we start with 1kHz on all four axes and let experience inform us on how right or wrong that choice was. It's possible that someone with hole popper work could run at 1 and 40kHz and report if there is a noticeable benefit at 40kHz.

--------------------------------------------
On Thu, 3/3/16, Nicklas Karlsson <***@gmail.com> wrote:

Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: "Pete_Gruendeman" <***@att.net>, "EMC developers" <emc-***@lists.sourceforge.net>
Date: Thursday, March 3, 2016, 12:01 PM

... 40kHz servo

response is very responsive but not necessary if the spark
frequency is less than that.

Pete

TJoseph Powderly

2016-03-07 02:23:31 UTC

sorry pete niklas
grab the POCO EDM MANUAL from internet
it shows fequencies ( or on&off times so you calculate )
off time is really dpendant on flushing conditions
on time causes rougher finer surface finish
so there is frequency but frequency is a result not a determinate parameter
examples
roughing Gr/St Positive Polarity 108uS on 12uS off
finishing----------------------------------8uS on 12uS off
you can calc the freq, i stopped thinking F when we still used TAU (
inverse of D% ;-)
thinking on and off is as simple as thinking cutter flukes and space
between flukes

tomp tjtr33

http://edmtechman.com/about.cfm
www.oelheld.com/products/metalworking-fluids/dielectric.html
scialert.net/fulltext/?doi=jas.2007.1608.1613&org=11
but just google 'electrical discharge machining frequency' and choose
images for more info than you can read in a year!

Post by Pete_Gruendeman
I am not seeing any response on this forum regarding the erosion pulse frequency.

Several hundred thousand sparks occur per second...

and in Ben Fleming's book on pulse type EDM, he shows frequencies that range from 2.5kHz up to 40kHz for finishing burns.
It's not yet clear to me that the servo response needs to be fast enough to respond to every spark. It might be helpful here if I described some of the basics of the process, based on personal experience and more so based on others' info, sources unknown.
The EDM process removes metal by superheating it with electrical sparks, and the collapse of said spark which per some authors blows out part of the metal.
The rapidly cooled workpiece surface becomes very hard and the surface finish is not particularly integral. This is commonly called a re-cast layer.
The sparks while underway have very little resistance as measured in ohms.
The electrical supply must be stopped periodically (square wave or other) so the present arc extinguishes and the next spark initiates at the next closest point between electrode and workpiece. That spark path could include bits of metal (called swarf) that have been blown out previously, resulting in a longer arc path and unstable erosion. Flushing is important to minimize or eliminate these alternate spark paths.
https://en.wikipedia.org/wiki/Caisson_(engineering)
<end of process particulars>
Each spark or pulse will vary from the one following and the one preceding it. My experience suggests that a little averaging is not a bad thing, in order to keep the process from hunting constantly. This could be mathematical averaging of erosion gap voltages or it might be a lower servo response frequency or other solution. Also backlash and machine elasticity needs to be considered. Even with a 40kHz servo response, the electrode to workpiece gap is not likely to change at 40kHz.
TJ pointed reminded us that EDM is a very slow process. Whether it is 99% of optimal or 99.99% of optimal won't change the burn times by much. If the cost of 40kHz servo response on four axes is excessive and 1kHz servo response is reasonable then I say we start with 1kHz on all four axes and let experience inform us on how right or wrong that choice was. It's possible that someone with hole popper work could run at 1 and 40kHz and report if there is a noticeable benefit at 40kHz.
--------------------------------------------
Subject: Re: [Emc-developers] EDM gap control (Control parameters)
Date: Thursday, March 3, 2016, 12:01 PM

... 40kHz servo

response is very responsive but not necessary if the spark
frequency is less than that.

Pete

Gruendeman
I have a choice
between 40kHz servo thread inside driver or linuxcnc 1kHz
servo thread. For z motion only choice is simple but for
motion of several axis/joints for example wire EDM?
Nicklas Karlsson
------------------------------------------------------------------------------
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Emc-developers mailing list
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Nicklas Karlsson

2016-03-07 04:22:59 UTC

On Mon, 7 Mar 2016 10:23:31 +0800

Post by TJoseph Powderly
off time is really dpendant on flushing conditions
on time causes rougher finer surface finish

I guess this explain it all and it also make perfect sense. More powder behind remove more material and longer time in between leave more time for debri to remove debri.

Regards Nicklas Karlsson

TJoseph Powderly

2016-03-07 09:30:41 UTC

i teach this way...
on & off is like a band saw blade
the teeth per inch is speed (F)
the width of tooth is roughness (On)
the space between is chip clearance (Off)
the height of tooth is bite size, suited to size of work (Ipeak)
the dirt and shape influence offtime (D%)

i agree that some of edm is art, well craft-sy anyway
but very little art is needed to get started

and the good student builds his/her picture of how & why it works
and continually tests that picture every cut.
the student teaches himself by being sensitive to the process
the teacher is the process, not me
START A NOTEBOOK NOW!
;-)
tomp

on 03/07/2016 12:22 Nicklas Karlsson wrote:nk On Mon, 7 Mar 2016

Post by TJoseph Powderly
off time is really dpendant on flushing conditions
on time causes rougher finer surface finish

I guess this explain it all and it also make perfect sense. More powder behind remove more material and longer time in between leave more time for debri to remove debri.
Regards Nicklas Karlsson
------------------------------------------------------------------------------
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EBo

2016-03-07 10:27:47 UTC

Nice explanation!

Post by TJoseph Powderly
i teach this way...
on & off is like a band saw blade
the teeth per inch is speed (F)
the width of tooth is roughness (On)
the space between is chip clearance (Off)
the height of tooth is bite size, suited to size of work (Ipeak)
the dirt and shape influence offtime (D%)
i agree that some of edm is art, well craft-sy anyway
but very little art is needed to get started
and the good student builds his/her picture of how & why it works
and continually tests that picture every cut.
the student teaches himself by being sensitive to the process
the teacher is the process, not me
START A NOTEBOOK NOW!
;-)
tomp
on 03/07/2016 12:22 Nicklas Karlsson wrote:nk On Mon, 7 Mar 2016

Post by TJoseph Powderly
off time is really dpendant on flushing conditions
on time causes rougher finer surface finish

I guess this explain it all and it also make perfect sense. More
powder behind remove more material and longer time in between leave
more time for debri to remove debri.
Regards Nicklas Karlsson
------------------------------------------------------------------------------
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Accelerate data analysis in your applications with
Intel Data Analytics Acceleration Library.
Click to learn more.
http://makebettercode.com/inteldaal-eval
_______________________________________________
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------------------------------------------------------------------------------
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TJoseph Powderly

2016-03-07 02:25:11 UTC

Post by Pete_Gruendeman
I am not seeing any response on this forum regarding the erosion pulse frequency.

Several hundred thousand sparks occur per second...

respond to every spark? no, not the servo, maybe the anti arc
fast as you can... yes ;-) gotta run ttul8r

Post by Pete_Gruendeman
The EDM process removes metal by superheating it with electrical sparks, and the collapse of said spark which per some authors blows out part of the metal.
The rapidly cooled workpiece surface becomes very hard and the surface finish is not particularly integral. This is commonly called a re-cast layer.
The sparks while underway have very little resistance as measured in ohms.
The electrical supply must be stopped periodically (square wave or other) so the present arc extinguishes and the next spark initiates at the next closest point between electrode and workpiece. That spark path could include bits of metal (called swarf) that have been blown out previously, resulting in a longer arc path and unstable erosion. Flushing is important to minimize or eliminate these alternate spark paths.
https://en.wikipedia.org/wiki/Caisson_(engineering)
<end of process particulars>
Each spark or pulse will vary from the one following and the one preceding it. My experience suggests that a little averaging is not a bad thing, in order to keep the process from hunting constantly. This could be mathematical averaging of erosion gap voltages or it might be a lower servo response frequency or other solution. Also backlash and machine elasticity needs to be considered. Even with a 40kHz servo response, the electrode to workpiece gap is not likely to change at 40kHz.
TJ pointed reminded us that EDM is a very slow process. Whether it is 99% of optimal or 99.99% of optimal won't change the burn times by much. If the cost of 40kHz servo response on four axes is excessive and 1kHz servo response is reasonable then I say we start with 1kHz on all four axes and let experience inform us on how right or wrong that choice was. It's possible that someone with hole popper work could run at 1 and 40kHz and report if there is a noticeable benefit at 40kHz.
--------------------------------------------
Subject: Re: [Emc-developers] EDM gap control (Control parameters)
Date: Thursday, March 3, 2016, 12:01 PM

... 40kHz servo

response is very responsive but not necessary if the spark
frequency is less than that.

Pete

Gruendeman
I have a choice
between 40kHz servo thread inside driver or linuxcnc 1kHz
servo thread. For z motion only choice is simple but for
motion of several axis/joints for example wire EDM?
Nicklas Karlsson
------------------------------------------------------------------------------
_______________________________________________
Emc-developers mailing list
https://lists.sourceforge.net/lists/listinfo/emc-developers

Pete_Gruendeman

2016-03-07 03:23:47 UTC

Hi:
TomP presented on-time and off-time values from the Poco manual which point to a range of 8.3 kHz to 50kHz, or cycles per second. It's still not clear how responsive the servo motion control needs to be. As far as arc detection and shutdown, I suspect that can be accomplished outside the motion loop, so it can respond much more quickly than the motion control.

Question: Are arcs detected by the same circuit as erosion gap voltage monitoring or by another means? For readers who haven't seen a DC arc in the tank, they are as bright as staring at the Sun. Poor or no flushing is what caused these arcs for me. Once detected, one could shut down the power supply for some fixed amount of time with an off-time of a second or two, whatever it takes to be sure the arc is cold and won't re-initiate in the same spot.

Speculation: Once an arc is detected the pulse generating code can increase the off-time by 20% (a guess) to make sure arcing doesn't continue to be a problem and then after X minutes of no arcing, progressively scale back to the starting off-time value.

Pete Gruendeman
--------------------------------------------
On Sun, 3/6/16, TJoseph Powderly <***@gmail.com> wrote:

Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: "Pete_Gruendeman" <***@att.net>, "EMC developers" <emc-***@lists.sourceforge.net>
Date: Sunday, March 6, 2016, 8:25 PM

On 03/07/2016 02:13 AM, Pete_Gruendeman wrotry

I am not seeing any response on

this forum regarding the erosion pulse frequency.

Wikipedia mentions on their

Several hundred thousand sparks occur

per second...

and in Ben Fleming's

book on pulse type EDM, he shows frequencies that range from
2.5kHz up to 40kHz for finishing burns.

It's not yet clear to me that the servo
response needs to be fast enough to respond to every
spark. It might be helpful here if I described
some of the basics of the process, based on personal
experience and more so based on others' info, sources
unknown.
respond to every spark? no, not the
servo, maybe the anti arc
fast as you can...
yes ;-) gotta run ttul8r

The EDM process

removes metal by superheating it with electrical sparks, and
the collapse of said spark which per some authors blows out
part of the metal.

The rapidly cooled

workpiece surface becomes very hard and the surface finish
is not particularly integral. This is commonly called a
re-cast layer.

The sparks while

underway have very little resistance as measured in ohms.

The electrical supply must be stopped

periodically (square wave or other) so the present arc
extinguishes and the next spark initiates at the next
closest point between electrode and workpiece. That spark
path could include bits of metal (called swarf) that have
been blown out previously, resulting in a longer arc path
and unstable erosion. Flushing is important to minimize or
eliminate these alternate spark paths.
The electrode advances (sinks) in a manner that is nearly
the same as a bridge support caisson being sunk into a
riverbed. The workers remove whatever is in the way to
allow the caisson to descend through the mud, gravel and

https://en.wikipedia.org/wiki/Caisson_(engineering)
<end of process particulars>
Each spark or

pulse will vary from the one following and the one preceding
it. My experience suggests that a little averaging is not
a bad thing, in order to keep the process from hunting
constantly. This could be mathematical averaging of
erosion gap voltages or it might be a lower servo response
frequency or other solution. Also backlash and machine
elasticity needs to be considered. Even with a 40kHz servo
response, the electrode to workpiece gap is not likely to
change at 40kHz.

pointed reminded us that EDM is a very slow process.
Whether it is 99% of optimal or 99.99% of optimal won't
change the burn times by much. If the cost of 40kHz servo
response on four axes is excessive and 1kHz servo response
is reasonable then I say we start with 1kHz on all four axes
and let experience inform us on how right or wrong that
choice was. It's possible that someone with
hole popper work could run at 1 and 40kHz and report if
there is a noticeable benefit at 40kHz.

--------------------------------------------

Subject: Re: [Emc-developers]

EDM gap control (Control parameters)

Date: Thursday, March 3,

2016, 12:01 PM

   > ... 40kHz servo
   response is very responsive

but not necessary if the spark

frequency is less than

that.

   > Pete
   Gruendeman

   I have a choice
   between 40kHz servo thread

inside driver or linuxcnc 1kHz

servo thread. For z motion

only choice is simple but for

motion of several axis/joints

for example wire EDM?

   Nicklas Karlsson

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Pete_Gruendeman

2016-03-08 16:47:42 UTC

Hi Nicklas:
I am writing with a request for what might be speculation on your part. Given what others have said about pulse frequency, and what is written in the Poco tech manuals (frequencies of approximately 8.33- 50kHz, derived from varying on and off times), would it be reasonable to produce the pulse timing from and at the same time that the PC is directing motion control? Erosion pulse generation could be treated as another axis-- maybe? I am concerned that the standard parport provides rather coarse granularity (increments) between one size and another size of pulse, especially as the pulse durations get down to 10 micro seconds on a finishing burn. The Mesa 5i20 will create about 200kHz pulses with L-cnc input and maybe one of the two parports on it could be repurposed as a pulse generator? Maybe it's unrealistic to generate pulses from the motion control PC because computing power isn't sufficient? Your thoughts?

Pete Gruendeman

--------------------------------------------
On Sun, 3/6/16, Nicklas Karlsson <***@gmail.com> wrote:

Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: "EMC developers" <emc-***@lists.sourceforge.net>
Date: Sunday, March 6, 2016, 10:22 PM

On Mon, 7 Mar 2016
10:23:31 +0800

Post by TJoseph Powderly
off time is

Nicklas Karlsson

2016-03-08 17:59:58 UTC

A microcontroller with suitable peripherals for power conversion is cheap and do the work much better. I know about: stm32f334, Infineon xmc4xxx something, maybe texas instruments and Microchip.

I am working with stm32f334. It have a high resolution timer equal to about 4GHz clock frequency with a lot of triggering options, DAC, fast comparators and cost maybe a few dollars. There are also cheap development boards available.

I guess spindle off/on signal may be useful to turn off/on generator and some m-code is useful for the parameters?

Regards Nicklas Karlsson

On Tue, 8 Mar 2016 16:47:42 +0000 (UTC)

Post by Pete_Gruendeman
I am writing with a request for what might be speculation on your part. Given what others have said about pulse frequency, and what is written in the Poco tech manuals (frequencies of approximately 8.33- 50kHz, derived from varying on and off times), would it be reasonable to produce the pulse timing from and at the same time that the PC is directing motion control? Erosion pulse generation could be treated as another axis-- maybe? I am concerned that the standard parport provides rather coarse granularity (increments) between one size and another size of pulse, especially as the pulse durations get down to 10 micro seconds on a finishing burn. The Mesa 5i20 will create about 200kHz pulses with L-cnc input and maybe one of the two parports on it could be repurposed as a pulse generator? Maybe it's unrealistic to generate pulses from the motion control PC because computing power isn't sufficient? Your thoughts?
Pete Gruendeman
--------------------------------------------
Subject: Re: [Emc-developers] EDM gap control (Control parameters)
Date: Sunday, March 6, 2016, 10:22 PM
On Mon, 7 Mar 2016
10:23:31 +0800

Post by TJoseph Powderly
off time is

really dpendant on flushing conditions
on time causes rougher finer surface finish
I guess this explain it all
and it also make perfect sense. More powder behind remove
more material and longer time in between leave more time for
debri to remove debri.
Regards Nicklas Karlsson
------------------------------------------------------------------------------
Transform Data into Opportunity.
Accelerate data analysis in your applications
with
Intel Data Analytics Acceleration
Library.
Click to learn more.
http://makebettercode.com/inteldaal-eval
_______________________________________________
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https://lists.sourceforge.net/lists/listinfo/emc-developers
------------------------------------------------------------------------------
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TJoseph Powderly

2016-03-09 06:10:03 UTC

Niklas Pete,
if you want ISOPULS ( isoenergetic pulses that have uniform craters )
then all the worry about frequency is useless

if you dont need uniforn surface finish, then ignore this comment

if you DO want uniform surface finish, then you do not use repetitive
pulse grnerator
instead, you wait for ionization ( a kind of indetermonate latency of
conduction)
THEN start decrementing the ontime. This was the joules delivered are
equal ( the energy is equal )
Once the ontime is finished, the current is turned off and the off time
is waited
THEN you turn on a tiny exciting voltage and wait for another ionization
( and voltage drop ) before starting the next ontime current flow.

some pix:
http://www.edm-products.com/Dielectrics/ifase/ifase_1.htm
look at figure 3
if you wait for the ionization (wait for the voltage to drop)
and then deliver current for the duraction of 'ontime',
the energy delivered will be uniform, and the surface crater will be uniform
if not, the energy per pulse in non-uniform, to the extreme that some
pulses deliver nearly no energy!
see figure 4,
when the strategy is isoenergetic, the current waveform will be uniform
and the leading edge of the voltage will vary.
if not isoenergetic, the leading edge is static on the scope,
but the current wave form will vary.

Post by Nicklas Karlsson
A microcontroller with suitable peripherals for power conversion is cheap and do the work much better. I know about: stm32f334, Infineon xmc4xxx something, maybe texas instruments and Microchip.
I am working with stm32f334. It have a high resolution timer equal to about 4GHz clock frequency with a lot of triggering options, DAC, fast comparators and cost maybe a few dollars. There are also cheap development boards available.
I guess spindle off/on signal may be useful to turn off/on generator and some m-code is useful for the parameters?
Regards Nicklas Karlsson
On Tue, 8 Mar 2016 16:47:42 +0000 (UTC)

Post by TJoseph Powderly
off time is

Nicklas Karlsson

2016-03-09 07:07:55 UTC

The high resolution timer together with the comparators should be able to do exactly what you say if properly configured. I got square wave out yesterday and expect to spend a few hours before it's correctly configured for EDM.

These micro controllers have only been available for a few years at most, they are really good and available from maybe a few dollars each.

Regards Nicklas Karlsson

On Wed, 9 Mar 2016 14:10:03 +0800

Post by TJoseph Powderly
Niklas Pete,
if you want ISOPULS ( isoenergetic pulses that have uniform craters )
then all the worry about frequency is useless
if you dont need uniforn surface finish, then ignore this comment
if you DO want uniform surface finish, then you do not use repetitive
pulse grnerator
instead, you wait for ionization ( a kind of indetermonate latency of
conduction)
THEN start decrementing the ontime. This was the joules delivered are
equal ( the energy is equal )
Once the ontime is finished, the current is turned off and the off time
is waited
THEN you turn on a tiny exciting voltage and wait for another ionization
( and voltage drop ) before starting the next ontime current flow.
http://www.edm-products.com/Dielectrics/ifase/ifase_1.htm
look at figure 3
if you wait for the ionization (wait for the voltage to drop)
and then deliver current for the duraction of 'ontime',
the energy delivered will be uniform, and the surface crater will be uniform
if not, the energy per pulse in non-uniform, to the extreme that some
pulses deliver nearly no energy!
see figure 4,
when the strategy is isoenergetic, the current waveform will be uniform
and the leading edge of the voltage will vary.
if not isoenergetic, the leading edge is static on the scope,
but the current wave form will vary.

Post by TJoseph Powderly
off time is

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TJoseph Powderly

2016-03-09 08:21:51 UTC

hmm nicklas, its a oneshot not a multivibrator for isopuls.

its a retriggerable if _not_ isopuls

make sense?

yes a hi-rez timer could be used for one shot, but needs voltage drop
detector to trigger it

tomp

Post by Nicklas Karlsson
The high resolution timer together with the comparators should be able to do exactly what you say if properly configured. I got square wave out yesterday and expect to spend a few hours before it's correctly configured for EDM.
These micro controllers have only been available for a few years at most, they are really good and available from maybe a few dollars each.
Regards Nicklas Karlsson
On Wed, 9 Mar 2016 14:10:03 +0800

Post by TJoseph Powderly
off time is

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Nicklas Karlsson

2016-03-09 09:08:18 UTC

Timer could be configured for: one shot, re-trigger, continuous.

Micro controller have built in comparators and I should use one for sparc detection and the other for start of ionization. Comparator outputs may be connected internally to high resolution timer and there quite many different triggering options. One of the comparator inputs are connected via a resistor divider network to detect gap voltage and the other to DAC inside micro controller.

I guess this very high resolution timer is not needed and ordinary timer would do but if micro controller suitable for power conversion is chosen this is what you get from around a few dollars. Micro controller also have several communication peripherals and I guess UART is the most suitable, I intend to use over an isolation barrier.

Regards Nicklas Karlsson

On Wed, 9 Mar 2016 16:21:51 +0800

Post by TJoseph Powderly
hmm nicklas, its a oneshot not a multivibrator for isopuls.
its a retriggerable if _not_ isopuls
make sense?
yes a hi-rez timer could be used for one shot, but needs voltage drop
detector to trigger it
tomp

Post by TJoseph Powderly
off time is

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TJoseph Powderly

2016-03-09 15:14:21 UTC

Nicklas,

Post by Nicklas Karlsson
Timer could be configured for: one shot, re-trigger, continuous.

sounds great,

Post by Nicklas Karlsson
Micro controller have built in comparators and I should use one for sparc detection and the other for start of ionization. Comparator outputs may be connected internally to high resolution timer and there quite many different triggering options. One of the comparator inputs are connected via a resistor divider network to detect gap voltage and the other to DAC inside micro controller.

yep, maybe allow for programmable levels to window comparator
iirc ours had several resistor divider values chosen thru a peel ( teeny
logic device maybe 256 gates )

Post by Nicklas Karlsson
I guess this very high resolution timer is not needed and ordinary timer would do but if micro controller suitable for power conversion is chosen this is what you get from around a few dollars. Micro controller also have several communication peripherals and I guess UART is the most suitable, I intend to use over an isolation barrier.

i used a pic 16f886 and could get 1uS rez in assembler and crude loops.
but used 4uS rez in practice ( was good enough for production surface
finish tho not good enough for molds )

Post by Nicklas Karlsson
Regards Nicklas Karlsson

thanks for working on this, I will get back to the etables ;-)
tomp

Pete_Gruendeman

2016-03-09 14:59:15 UTC

TJ:
Slightly off-topic: Your explanation of isopulse technology explains at least partially why RC based EDMs produce pretty darn good finishes-- because the energy per pulse is mostly constant. The capacitors dump their energy, the arc goes out and that's it. The short pulse durations do cause greater electrode wear, even with positive polarity on the electrode.

I ran a Charmilles D-10 and a D-20. The D-10 was an Isopulse machine and I think the D-20 was also. I also programed and ran an Agie AT-50, which was later re-branded as the U-100. I don't remember the name of the pulse technology it used. Electrode wear was remarkably low on the Agie.

Pete Gruendeman

--------------------------------------------
On Wed, 3/9/16, TJoseph Powderly <***@gmail.com> wrote:

Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: "EMC developers" <emc-***@lists.sourceforge.net>
Date: Wednesday, March 9, 2016, 12:10 AM

Niklas Pete,
if you want ISOPULS ( isoenergetic pulses that
have uniform craters )
then all the worry
about frequency is useless

if you dont need uniforn surface finish, then
ignore this comment

if you
DO want uniform surface finish, then you do not use
repetitive
pulse grnerator
instead, you wait for ionization ( a kind of
indetermonate latency of
conduction)
THEN start decrementing the ontime. This was
the joules delivered are
equal ( the energy
is equal )
Once the ontime is finished, the
current is turned off and the off time
is
waited
THEN you turn on a tiny exciting
voltage and wait for another ionization
(
and voltage drop ) before starting the next ontime current
flow.

some pix:
http://www.edm-products.com/Dielectrics/ifase/ifase_1.htm
look at figure 3
if you wait
for the ionization (wait for the voltage to drop)
and then deliver current for the duraction of
'ontime',
the energy delivered will
be uniform, and the surface crater will be uniform
if not, the energy per pulse in non-uniform, to
the extreme that some
pulses deliver nearly
no energy!
see figure 4,
when the strategy is isoenergetic, the current
waveform will be uniform
and the leading
edge of the voltage will vary.
if not
isoenergetic, the leading edge is static on the scope,
but the current wave form will vary.

On 03/09/2016 01:59 AM,

Post by Nicklas Karlsson
A

microcontroller with suitable peripherals for power
conversion is cheap and do the work much better. I know
about: stm32f334, Infineon xmc4xxx something, maybe texas
instruments and Microchip.

Post by Nicklas Karlsson
I am working with stm32f334. It have a

high resolution timer equal to about 4GHz clock frequency
with a lot of triggering options, DAC, fast comparators and
cost maybe a few dollars. There are also cheap development
boards available.
I guess spindle off/on signal may be useful to turn off/on
generator and some m-code is useful for the parameters?

Post by Nicklas Karlsson
Regards Nicklas

Karlsson

TJoseph Powderly

2016-03-09 15:27:38 UTC

Hi Pete
i think it was AGie BiPuls
2 power supplies
1 for ignition (selectable 100 150 200 270V) about 750mA
1 for guts power 60 amp increments
big TO3 power transistors
the finefinish supply was separate only 5A iirc
The Charmilles D10 was sweet could cut in mud and never arc and still
gave good finishes
big inductor in guts dc power supply looked like a trafo
D-10 killed off the AGie ABs which ruled the small insert/spinnerete world
D-10 with a P25 isopuls is still a wanted item

the RC supplies triggered when the gap was ready
the early transistor supplies fired at a given frequency
later isolpuls mimiced the RC/RCL supplies by waiting for the gap to be
ready

i was AGie sinker service in 70-90s ;-)

tomp

Slightly off-topic: Your explanation of isopulse technology explains at least partially why RC based EDMss produce pretty darn good finishes-- because the energy per pulse is mostly constant. The capacitors dump their energy, the arc goes out and that's it. The short pulse durations do cause greater electrode wear, even with positive polarity on the electrode.
I ran a Charmilles D-10 and a D-20. The D-10 was an Isopulse machine and I think the D-20 was also. I also programed and ran an Agie AT-50, which was later re-branded as the U-100. I don't remember the name of the pulse technology it used. Electrode wear was remarkably low on the Agie.
Pete Gruendeman
--------------------------------------------
Subject: Re: [Emc-developers] EDM gap control (Control parameters)
Date: Wednesday, March 9, 2016, 12:10 AM
Niklas Pete,
if you want ISOPULS ( isoenergetic pulses that
have uniform craters )
then all the worry
about frequency is useless
if you dont need uniforn surface finish, then
ignore this comment
if you
DO want uniform surface finish, then you do not use
repetitive
pulse grnerator
instead, you wait for ionization ( a kind of
indetermonate latency of
conduction)
THEN start decrementing the ontime. This was
the joules delivered are
equal ( the energy
is equal )
Once the ontime is finished, the
current is turned off and the off time
is
waited
THEN you turn on a tiny exciting
voltage and wait for another ionization
(
and voltage drop ) before starting the next ontime current
flow.
http://www.edm-products.com/Dielectrics/ifase/ifase_1.htm
look at figure 3
if you wait
for the ionization (wait for the voltage to drop)
and then deliver current for the duraction of
'ontime',
the energy delivered will
be uniform, and the surface crater will be uniform
if not, the energy per pulse in non-uniform, to
the extreme that some
pulses deliver nearly
no energy!
see figure 4,
when the strategy is isoenergetic, the current
waveform will be uniform
and the leading
edge of the voltage will vary.
if not
isoenergetic, the leading edge is static on the scope,
but the current wave form will vary.
On 03/09/2016 01:59 AM,

Post by Nicklas Karlsson
A

microcontroller with suitable peripherals for power
conversion is cheap and do the work much better. I know
about: stm32f334, Infineon xmc4xxx something, maybe texas
instruments and Microchip.

Post by Nicklas Karlsson
I am working with stm32f334. It have a

Post by Nicklas Karlsson
Regards Nicklas

Karlsson
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Pete_Gruendeman

2016-03-09 16:22:33 UTC

Hi Nicklas:
Before it became clear that modern EDM technology is pretty darn complex,
was your intention more along the lines of motion control software for EDM or
are you in for the whole adventure? This seems like a much bigger project than I was expecting. I'd accept some kind of approximate solution in favor of getting something running. That's why my first NC EDM was an RC type and I used a Bridgeport milling machine as the motion platform. Don't laugh. I can post pix of work completed on it.
I work in research and we always have to concede perfection for "done" as "done" at least presents a path forward, sometimes including a revenue stream. The search for perfection sometimes results in a lot of knowledge but nothing to present to the world. Just my 2 cents.

What are Your goals for this project?

Pete Gruendeman

--------------------------------------------
On Wed, 3/9/16, Nicklas Karlsson <***@gmail.com> wrote:

Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: "EMC developers" <emc-***@lists.sourceforge.net>
Date: Wednesday, March 9, 2016, 3:08 AM

Timer could be configured
for: one shot, re-trigger, continuous.

Micro controller have built in comparators and
I should use one for sparc detection and the other for start
of ionization. Comparator outputs may be connected
internally to high resolution timer and there quite many
different triggering options. One of the comparator inputs
are connected via a resistor divider network to detect gap
voltage and the other to DAC inside micro controller.

I guess this very high
resolution timer is not needed and ordinary timer would do
but if micro controller suitable for power conversion is
chosen this is what you get from around a few dollars. Micro
controller also have several communication peripherals and I
guess UART is the most suitable, I intend to use over an
isolation barrier.

Regards
Nicklas Karlsson

Nicklas Karlsson

2016-03-09 16:42:37 UTC

Post by Pete_Gruendeman
Before it became clear that modern EDM technology is pretty darn complex,
was your intention more along the lines of motion control software for EDM or
are you in for the whole adventure?

TJoseph Powderly

2016-03-09 17:14:41 UTC

nicklas hello
kerosene may sound scary but it is good if the sparks are 20mm below
surface of kerosene
i used it for fine finishes instead of 'real edm fluid'

if you can find 'white spirits' or slightly heavier parafinic it is better
quite simply the oils suitefd to sink edm are in a narrow range when in
the cracking tower

edm fluid is hard to find in small quantities

possibly, contact local OelHeld office for a litre or two as free sample
tell them your intention

read the OelHeld literature to see common names for oils suited to EDM

btw:
water works well too. i ran stock sinkers with plastic tubs inside work
tank to test for GE titanium turbines
at 150 amp ruffing ( messy grey foam but it worked ;-) not even DI water!
tomp

Hole adventure but it does not have to be a good EDM machine with todays standard. Then it come to machine dynamics I will however spend more time.
As is now motion control work and hopefully there will be most software which is rather small before I could machine my first piece of scrap. The thing that worry me most is the fluid, I read it is kerosene, there are high currents and pumps with not to low pressure so what could possible go wrong?
Regards Nicklas Karlsson
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andy pugh

2016-03-09 17:31:55 UTC

Post by TJoseph Powderly
kerosene may sound scary but it is good if the sparks are 20mm below
surface of kerosene
i used it for fine finishes instead of 'real edm fluid'

We used paraffin (kerosene) for a specimen prep EDM at Leeds. One of
the technicians had worked somewhere else where the exact same machine
had been left unattended and the level had dropped too low. Apparently
it wasn't all that badly damaged, but the amount of soot that filled
the room was immense.

--
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

Pete_Gruendeman

2016-03-09 17:34:41 UTC

The thing that worry me most is the fluid, I read it is kerosene,...

No worries there. Ace Hardware in the US and other DIY/ hardware stores around the world sell a light oil for kerosine lamps. Kerosine is called Paraffin in the British speaking world. It very much resembles Commonwealth EDM-244 oil, typically sold in 55 gallon drums in the US. The lamp oil is sold in 1 quart and 1 gallon plastic bottles. You'll need a gallon, if only to make sure your erosion zone is 1inch or 25mm or more below the surface of the oil. As long as you do that the hot sparks and vaporized oil have no access to oxygen and there is no risk of fire. Fire= Heat + flammable + oxygen. Take away any one of them and you'll be safe.

I used:
Lamplight (brand)
Ultra-Pure
99% Pure Liquid Paraffin Candle and Lamp Liquid

This product on the Ace Hardware web site looks to be the same but it does not look like a gallon bottle. For $18USD it should be one gallon.
http://www.acehardware.com/product/index.jsp?productId=1275451
I bought six gallons pretty cheap because that was a whole case and I paid cash before he ordered it. I think they took 20% off for that. $18.00 for one quart is way too expensive.

Your first burn should be with a Poco electrode or copper or brass. Electric motor brushes work poorly-- or so I have read. The others are good. A decent practise burn can be done with 2-5 amps at 40-80 volts. High power is not needed to get started.

Pete Gruendeman

--------------------------------------------
On Wed, 3/9/16, Nicklas Karlsson <***@gmail.com> wrote:

Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: "Pete_Gruendeman" <***@att.net>, "EMC developers" <emc-***@lists.sourceforge.net>
Date: Wednesday, March 9, 2016, 10:42 AM

Before it became clear that modern

EDM technology is pretty darn complex,
was your intention more along the lines of motion control
software for EDM or

are you in for the

whole adventure?

Hole
adventure but it does not have to be a good EDM machine with
todays standard. Then it come to machine dynamics I will
however spend more time.

As
is now motion control work and hopefully there will be most
software which is rather small before I could machine my
first piece of scrap. The thing that worry me most is the
fluid, I read it is kerosene, there are high currents and
pumps with not to low pressure so what could possible go
wrong?

Regards Nicklas Karlsson

andy pugh

2016-03-09 17:51:36 UTC

Post by Pete_Gruendeman
No worries there. Ace Hardware in the US and other DIY/ hardware stores around the world sell a light oil for kerosine lamps. Kerosine is called Paraffin in the British speaking world.

Lamp Oil, Paraffin (Kerosene) and White Spirit (Stoddard Solvent) are
all acceptable fluids for fire-breathing, so will probably all work
the same for spark erosion.

EBo

2016-03-09 18:22:23 UTC

Post by Pete_Gruendeman
No worries there. Ace Hardware in the US and other DIY/ hardware
stores around the world sell a light oil for kerosine lamps. Kerosine
is called Paraffin in the British speaking world.

Lamp Oil, Paraffin (Kerosene) and White Spirit (Stoddard Solvent) are
all acceptable fluids for fire-breathing, so will probably all work
the same for spark erosion.

I did not know that Kerosene is also known as Paraffin in many places.
I always thought of Paraffin as just Paraffin Wax. Hmmm... learned
something new today for sure. Have to rethink an old project while I am
at it...

THanks!

EBo --

tjtr33

2016-03-05 02:24:33 UTC

Google garden of edm
Google groups diy edm
Tomp tjtr33

always good advice. Do you know one where we can go and play with one
;-)

Post by Pete_Gruendeman

Post by Gene Heskett
Or is there a better material to make the electrode from?

You'll be rich when you figure that out. Find a way to 3-D print an
electrode and you'll set the world on fire.

Post by Pete_Gruendeman
Or 3-D print the
heat-treated steel mold cavity directly!

tjtr33

2016-03-05 02:31:33 UTC

Some say lower wear is caused by fast on and off edges of pulse delivered. Not just at board but at gap. Loads of high tech literature to wade thru because its is plasma not standard I=e/r electric rules. But in practice... The new fet generators with good cables and low system inductance wear less than tube and r/c gnr8rs. I have moved the final power modules to the head and ran the base DC there to get the last bit of inductance/ resistance out.
Oops rambling...

Post by Pete_Gruendeman
My comments on people getting experience with running an EDM is Not directed at any one person. It's just that this art form is so different from what most people have experienced in machine shops. Go play with one and many of these mysteries will become clearer.

Post by Gene Heskett
Or is there a better material to make the electrode from?

You'll be rich when you figure that out. Find a way to 3-D print an electrode and you'll set the world on fire. Or 3-D print the heat-treated steel mold cavity directly!
Many writers (not me because I don't know) state that electrode wear occurs at the initiation of the spark and that the wear is due to heat at the electrode surface that isn't conducted away fast enough. For those who haven't seen it, that is likely why finish electrodes/ burns have such high wear rates. They endure so very many more sparks than a roughing burn which has sparks of higher power but longer duration so there are far less of them.
Does anybody know the typical frequency or pulses per second for finishing burns? I think it's on the order of 3-5kHz but will look into it of someone doesn't already know. 40kHz servo response is very responsive but not necessary if the spark frequency is less than that.
Pete Gruendeman
--------------------------------------------
Subject: Re: [Emc-developers] EDM gap control (Control parameters)
Date: Wednesday, March 2, 2016, 11:38 PM
On Wednesday 02 March

Post by Gene Heskett
sorry Pete
I

disagree, any time spent in the wrong position is time spent
making

Post by Gene Heskett
bad discharges
which can damage surface by overheating
or
spend time

throwing snowballs that fall short of hitting the target

Post by Gene Heskett
imo, update postion as fast as possible
the average velocity ( a RESULT) will be

low

Post by Gene Heskett
but the process will be more

stabile and the surface will not be hard

Post by Gene Heskett
and crusty
abd the

time will be lower

Post by Gene Heskett
oops power fail in

ChiangMai

Post by Gene Heskett
ttyl8r

tomp
One thing I have
always felt needed to be asked, but don't recall seeing
it discussed, is when doing a sinker edm to
imprint a carbon mold like
I've seen
pix of, like engraving a relieved signature, is there an
optimum current per square, either in cm2 or
in2 to design the process
to so it
functions best?
And in
terms of wear on the shaped carbon electrode, is there a
best
current per square in terms of the
metal removed vs the carbon wasted
that
will prolong the electrode life vs metal removed? I've
seen other
processes where optimizing one
is not optimizing the other.
Or is there a better material to make the
electrode from?

Post by Gene Heskett
On
Correct that looping once per millisecond is

definitely fast
enough. On my machine, 40,000 encoder counts =
1 inch. Spark

Post by Pete_Gruendeman
lengths, even for

finishing operations are 0.001" or longer, or 40

Post by Pete_Gruendeman
encoder counts to go from first spark

to the electrode making

Post by Pete_Gruendeman
physical

contact and that's in 1/25th of a second. That's
not a

Post by Pete_Gruendeman
problem if the machine is

moving at 2- 4 inches per minute. At 4

Post by Pete_Gruendeman
IPM, coming to a stop in 0.001 inches

requires an acceleration of
-0.01852 feet per second squared or -0.00058 g's of
acceleration.

Post by Pete_Gruendeman
No problem.
The

other axes would be the same in that gap voltage/current

Post by Pete_Gruendeman
measurement at 1,000 times per second

is plenty fast enough. In

Post by Pete_Gruendeman
fact,

the program I wrote upon detection of gap voltage too low

Post by Pete_Gruendeman
waits on location for 10 milliseconds

and then checks again as often

tjtr33

2016-03-05 02:22:04 UTC

Sent from my BLU smartphone device

Pete_Gruendeman <***@att.net> wrote:

Hi Nicklaus:
Someone more knowledgeable that I will need to tell us about the pulse generator frequencies that are used under various burn conditions. I am of the opinion that the servo response does not need to be faster than that pulse frequency.

Pete I have tables I developed for gr/st using 3 grades of graphite. Tables are sequences of on off peak selected by contact area. You choose by area. Then end the sequence at the desired finish. These belong to me. Not proprietary. Will be PD if license is good for community. Else I just give away
I have a scheme in linuxcnc to open the table file then select the next power stage and set the hardware . its simple mcode using python.
I will post tables and mcodes soon.

Can you tell us what costs are of servo control at 1kHz and 40 kHz? Hardware or processor time costs?; proprietary versus public domain software?

While sinker EDM primarily uses Z motion, it is by no means exclusively Z motion. Many projects use the other axes, either part of the time or all of the time. The motion control for all the axes needs to be equally responsive as long as one or more users operate on more than the Z axis. AFIK Z-axis only motion is appropriate for hole popping EDMs.

My macros for heidenhain asked operator for the tool axis and reference position . operator supplied distance from ref to move over clamps then how close when power on and final cavity depth. This allows cuts in xyz in plus and minus :-)
I will try to convert to canned orbiting cycles for linuxcnc if I ever get the sine cosine gen to play nice with edm gap control. We COULD. have circular spherical and rectangular orbits automated thru the tables. I don't have these motions Good yet but expect it is possible in HAL

Pete Gruendeman

Tomp tjtr33
--------------------------------------------
On Thu, 3/3/16, Nicklas Karlsson <***@gmail.com> wrote:

Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: "Pete_Gruendeman" <***@att.net>, "EMC developers" <emc-***@lists.sourceforge.net>
Date: Thursday, March 3, 2016, 12:01 PM

... 40kHz servo

response is very responsive but not necessary if the spark
frequency is less than that.

Pete

Gruendeman

I have a choice
between 40kHz servo thread inside driver or linuxcnc 1kHz
servo thread. For z motion only choice is simple but for
motion of several axis/joints for example wire EDM?

Nicklas Karlsson

Be aware of the cubed rate...
When 2 axis move at same time they have higher speed. Ditto for 3d moves! Old stepper edms did not take care and were not stable

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Nicklas Karlsson

2016-03-10 07:10:47 UTC

Post by Pete_Gruendeman
Can you tell us what costs are of servo control at 1kHz and 40 kHz? Hardware or processor time costs?; proprietary versus public domain software?

It is a choice between coordinated movement and speed. I put gap control in motor controller and gain speed but loose coordinated movement, at least within 1ms period.

It would obviously be possible to get both but not that easy. 1kHz is what linuxcnc servo control loop do and 40kHz is what motor control servo loop do.

Nicklas Karlsson

Pete_Gruendeman

2016-03-10 14:43:03 UTC