Wanted to pick all your brains on Wire EDMing graphite. Cutting on a Robocut with AI settings and do not have presets for graphite. Normally use tool steel setting(A2) and tweak the on/off, speed and SV. Get a lot of wire breaks even if I soak the graphite over night. Any suggestions on power settings or setup techniques. Mainly cut smaller thickness from 1/2" to 1".
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Cutting Graphite Wire EDM
- Thread starter KennyBoi
- Start date
- Replies 11
- Views 9,385
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi KennyBoi:
Cutting graphite will always be a pain; it's full of pores, it's dirty, it's brittle, it's conductive but not all THAT conductive and it sublimates at high temperature.
Having said all that I've had better success with POCO Angstrofine than with any other plain graphite grade.
I've also had decent success with copper graphite.
Using aluminum settings is not a bad starting place because both materials run dirty; I find I need to tweak a big servo gap, and a long off time to have much of a chance of success even if I start with those aluminum settings.
I hate it' it's a royal nuisance every time, so I avoid it when I can, and cut my sinker trodes from copper or copper tungsten.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
www.vancouverwireedm.com
Cutting graphite will always be a pain; it's full of pores, it's dirty, it's brittle, it's conductive but not all THAT conductive and it sublimates at high temperature.
Having said all that I've had better success with POCO Angstrofine than with any other plain graphite grade.
I've also had decent success with copper graphite.
Using aluminum settings is not a bad starting place because both materials run dirty; I find I need to tweak a big servo gap, and a long off time to have much of a chance of success even if I start with those aluminum settings.
I hate it' it's a royal nuisance every time, so I avoid it when I can, and cut my sinker trodes from copper or copper tungsten.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
www.vancouverwireedm.com
Thanks for the input Marcus. We have ordered various grades from POCO but have not tried the Angstrofine grade. Tried burning the copper infused and it did not go well. I will have to play with the aluminum settings to see if that will work out for us. How is sinking with graphite vs copper electrodes(pros/cons)?
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi again KennyBoi:
The most common grade used is Tellurium copper usually abbreviated to "Telco"
This grade is popular because it's very easy to machine so it's nice to make electrodes from.
It is said to be inferior in burning performance to C101 oxygen free copper, but I can't say I've noticed a difference and I've tried both.
There are two things about copper trodes:
1) Machining them leaves them lousy with burrs, so it can be a real nightmare deburring them if they're complex.
2) There is a certain power range in which they're happy...they wear too much with high amperage burns, and they make burn berries on my machine at super low amperage burns, so they're best for trodes you can comfortably hold between two fingers.
Copper trodes do well with some generators and seemingly not so well with others.
Asian machines apparently suit copper very well, and I read somewhere that copper was the GO TO material for Japanese machines in the past, so it kind of makes sense.
On the other hand, I run an All-American (Hansvedt) machine and I have no problems.
One of the toolrooms I worked in back in the day used copper for picking out fine details on a Charmilles and were happy too.
Copper wears more than graphite in general, but it's not as dirty in the cut.
I use copper mostly to avoid the mess of machining graphite, not for any superior performance or anything like that.
For tiny trodes I like to use copper tungsten, but it's EXPENSIVE!!!
I find it to be intermediate in wear performance between copper and graphite but I seem to be able to do better with it than any other trode material on the really tiny stuff.
Going back to Angstrofine graphite...be sitting down when you get prices, and don't plan on making car bumper mold trodes from it.
It's still graphite and still shitty to burn, but I've had better success with it than with other POCO grades because it is so uniform and the particle size is very small so it's mostly graphite and not so much coal tar binder.
Copper is a gazillion times easier to wire cut, and copper tungsten is very close to copper for wire cutting.
So in summary: If I was choosing material that was mostly going to be wire cut or was a simple, open, easy-to-mill shape I'd pick Telco because it's clean to machine and simple to wire.
If it was going to be lots of fussy little milling or grinding I'd choose graphite to avoid the burrs.
If it was going to be a big trode (bigger than a fist) it'd be graphite (copper's HEAVY and many modern servo rams can't handle a lot of weight).
It's also easy to buy in big blocks.
If it was super tiny I'd choose copper tungsten or Angstrofine graphite.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
www.vancouverwireedm.com
The most common grade used is Tellurium copper usually abbreviated to "Telco"
This grade is popular because it's very easy to machine so it's nice to make electrodes from.
It is said to be inferior in burning performance to C101 oxygen free copper, but I can't say I've noticed a difference and I've tried both.
There are two things about copper trodes:
1) Machining them leaves them lousy with burrs, so it can be a real nightmare deburring them if they're complex.
2) There is a certain power range in which they're happy...they wear too much with high amperage burns, and they make burn berries on my machine at super low amperage burns, so they're best for trodes you can comfortably hold between two fingers.
Copper trodes do well with some generators and seemingly not so well with others.
Asian machines apparently suit copper very well, and I read somewhere that copper was the GO TO material for Japanese machines in the past, so it kind of makes sense.
On the other hand, I run an All-American (Hansvedt) machine and I have no problems.
One of the toolrooms I worked in back in the day used copper for picking out fine details on a Charmilles and were happy too.
Copper wears more than graphite in general, but it's not as dirty in the cut.
I use copper mostly to avoid the mess of machining graphite, not for any superior performance or anything like that.
For tiny trodes I like to use copper tungsten, but it's EXPENSIVE!!!
I find it to be intermediate in wear performance between copper and graphite but I seem to be able to do better with it than any other trode material on the really tiny stuff.
Going back to Angstrofine graphite...be sitting down when you get prices, and don't plan on making car bumper mold trodes from it.
It's still graphite and still shitty to burn, but I've had better success with it than with other POCO grades because it is so uniform and the particle size is very small so it's mostly graphite and not so much coal tar binder.
Copper is a gazillion times easier to wire cut, and copper tungsten is very close to copper for wire cutting.
So in summary: If I was choosing material that was mostly going to be wire cut or was a simple, open, easy-to-mill shape I'd pick Telco because it's clean to machine and simple to wire.
If it was going to be lots of fussy little milling or grinding I'd choose graphite to avoid the burrs.
If it was going to be a big trode (bigger than a fist) it'd be graphite (copper's HEAVY and many modern servo rams can't handle a lot of weight).
It's also easy to buy in big blocks.
If it was super tiny I'd choose copper tungsten or Angstrofine graphite.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
www.vancouverwireedm.com
bob
Titanium
- Joined
- Aug 12, 2002
- Location
- Regina, Canada
Hey, I was browsing for some information on cutting graphite on the wire and came across this thread and have a question to add, hoping you guys can help me out.
When cutting graphite on the wire, is it common to only take one pass or is multiple passes still achievable? I'm sure there are many things to consider, but I'm not sure what the best practice is.
I've never cut graphite and unfortunately I have a 12in tall piece of POCO 3 I need to wire a form in with a .002 unilateral profile tolerance, and I'm very hesitant about it.
Thank you, it's much appreciated!
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi JZ:
One of the main reasons to skim cut is to correct the distortion that comes from stress release after roughing.
Graphite does not behave that way.
So theoretically...
But the reality is you also have all kinds of geometry errors from wire resonating, wire lag, flushing pressure etc etc.
So to correct those errors, skimming is still useful.
Moving on to your task:
All I can say is "Holy Shit!"
A twelve inch tall lump of graphite...this is going to be a cast iron bitch to cut!
I say this because graphite is both dirty in the cut and not very conductive compared to metals.
You will fight wire breaks.
You will fight wire shorts
I don't envy you this task...I've always had trouble wire cutting graphite, so this tall a block is going to give you serious bragging rights if you can pull it off uneventfully.
I will pray to the EDM Gods for your success.
I recommend going up to 0.012" wire if you can, and opening up the servo gap as much as you can.
Long off times may also help you and a modest nominal feedrate too.
Perfect sealed flushing too...new flush cups, a surface ground block that's dead nuts parallel, and a flush cup gap of no more than 0.005".
Submerged machining, and the most flushing pressure you can provide.
You may have better luck with a stratified wire too, but you may not.
They entrain water better, but they're not as resistant to wire breaks, at least not in my experience.
If you can find some Agie Cobracut B that might help...it sure does on tall aluminum workpieces, compared to plain hard brass wire.
Prayers are always good, curse words are sometimes necessary too, and a skeptical attitude toward the boss who handed you this flaming football also.
Be sure to under-promise, make a lot of noise about the genius level of luck you will require, and set the expectations of everyone properly, before you clamp the block to the table.
That should give everyone the correct attitude before you begin!
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
One of the main reasons to skim cut is to correct the distortion that comes from stress release after roughing.
Graphite does not behave that way.
So theoretically...
But the reality is you also have all kinds of geometry errors from wire resonating, wire lag, flushing pressure etc etc.
So to correct those errors, skimming is still useful.
Moving on to your task:
All I can say is "Holy Shit!"
A twelve inch tall lump of graphite...this is going to be a cast iron bitch to cut!
I say this because graphite is both dirty in the cut and not very conductive compared to metals.
You will fight wire breaks.
You will fight wire shorts
I don't envy you this task...I've always had trouble wire cutting graphite, so this tall a block is going to give you serious bragging rights if you can pull it off uneventfully.
I will pray to the EDM Gods for your success.
I recommend going up to 0.012" wire if you can, and opening up the servo gap as much as you can.
Long off times may also help you and a modest nominal feedrate too.
Perfect sealed flushing too...new flush cups, a surface ground block that's dead nuts parallel, and a flush cup gap of no more than 0.005".
Submerged machining, and the most flushing pressure you can provide.
You may have better luck with a stratified wire too, but you may not.
They entrain water better, but they're not as resistant to wire breaks, at least not in my experience.
If you can find some Agie Cobracut B that might help...it sure does on tall aluminum workpieces, compared to plain hard brass wire.
Prayers are always good, curse words are sometimes necessary too, and a skeptical attitude toward the boss who handed you this flaming football also.
Be sure to under-promise, make a lot of noise about the genius level of luck you will require, and set the expectations of everyone properly, before you clamp the block to the table.
That should give everyone the correct attitude before you begin!
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
Last edited:
Bud Guitrau
Aluminum
- Joined
- May 8, 2006
- Location
- SoCal
Everything Marcus wrote is accurate.
To cut 12' thick graphite (of any grade on any machine) you'd be better off band-sawing it rough and milling it to size.
Even when using a "D" wire, ANY coating, however thick, would be cooked off long before exiting a 12' part and would be a waste of money yielding EXPENSIVE poor-performance.
For this cut, if you absolutely must do this (still a loser, IMO), I'd use .012" hard-brass yielding only a more ECONOMICAL poor-performance.
Makino touts .016" wire technology. I'd ask them your hard questions about WEDM'ing graphite.
To cut 12' thick graphite (of any grade on any machine) you'd be better off band-sawing it rough and milling it to size.
Even when using a "D" wire, ANY coating, however thick, would be cooked off long before exiting a 12' part and would be a waste of money yielding EXPENSIVE poor-performance.
For this cut, if you absolutely must do this (still a loser, IMO), I'd use .012" hard-brass yielding only a more ECONOMICAL poor-performance.
Makino touts .016" wire technology. I'd ask them your hard questions about WEDM'ing graphite.
Thank you much guys I really appreciate it!
I was able to get a test part set -up and ready to rock late last week. It was quite the journey to get going on the burn, as my Graphite settings on my machine are only for up to 6in. so there was some playing around with conditions to get what I thought seemed like a good burn.
As far as the wire went, I talked to a guy at SST for some options, and I run a .010 PC HB wire and he actually recommended that over a coated wire. I could have and still can go to a .012 wire, I just have the .010 here and I wanted to get this test cut going.
I mounted this part on my 3R, then attached that to an angle plate so I could get it out into the tank and I am able to have CLOSED conditions for my flush cups, I've got the top set with no more than a .004-.005 gap. I even put my fancy shield on the upper head in an effort to keep the flushing more consistent and no rooster tails.
Wire breaks.....ohh ya, I have quite a few at the beginning, and boy was that annoying! I have to drain the tank,hand thread it, then fill the tank just so it would break again over and over a again until I got the cut stable. I was able to keep my patience and just reminded myself it was going to be a slow process regardless.
As far as the burn went, it took a very very long time. It drove me crazy with how slow it was cutting, but it was working and I just had to let it be. Since I had a test piece I programmed it just as I plan to cut the actual part. Its a 1inx3inx12in chunk and I have my profile nested into the stock where I can burn in from the side cut the profile and go out the other to get the main slug off. The actual electrode I need to burn it approx .375 x 2.625 x 12in, so I have it centered in the block in the X axis but I left myself some room in the Y incase I need to move back and cut another one.
Funny part here...I think this whole part should be done on the CNC Mill and I have no idea why we aren't trying that but whatever. My boss thinks I am going to tab this and cut it off...then blend it somehow...I think I'm going to make a fixture then take it to the CNC for the blend job...at least I hope because, I tried a small as possible tab like .050 wide and .100 long and it started to break down when I came down the second side of the tab. Luckily it held on and I was able to get the main slug off. If there are any suggestions there I am open to all!
I took the advice and went for a one pass cut. At first when I was experiencing the most wire breaks I was cruising a whopping .005-.006 per min, flushing was almost maxed out, but I could hear the cut sputtering every now and then, and it would start to short out in some spots. I ended up dropping my ON time a couple and raised my OFF time plus a larger SV and it took my cut down to .003 per min. This was the sweet spot though, and I was thrilled to get there. I didn't have anymore wire breaks or short circuits throughout the rest of the cut.
I am actually quite happy with the first attempt. The finish I got off of one pass is waaay better than I expected. If I lay the part down and indicate it, I see about .002 taper end to end and I'd say .0005 little dip in the middle. Completely surprised me to be honest, I also had added .002 to my offset and over all the part is close to dim all round. At the lowest point I measure it at .3735, so i'll have to run it on the CMM to truly see where I'm at and if it will be acceptable.
I'll be sure to post an update when I get the final part finished.
Thanks again!
Here's a photo of my test cut. Don't mind the junk on the left side, it is where I ran into some of the pre existing mill cut and had to break a piece off.
I was able to get a test part set -up and ready to rock late last week. It was quite the journey to get going on the burn, as my Graphite settings on my machine are only for up to 6in. so there was some playing around with conditions to get what I thought seemed like a good burn.
As far as the wire went, I talked to a guy at SST for some options, and I run a .010 PC HB wire and he actually recommended that over a coated wire. I could have and still can go to a .012 wire, I just have the .010 here and I wanted to get this test cut going.
I mounted this part on my 3R, then attached that to an angle plate so I could get it out into the tank and I am able to have CLOSED conditions for my flush cups, I've got the top set with no more than a .004-.005 gap. I even put my fancy shield on the upper head in an effort to keep the flushing more consistent and no rooster tails.
Wire breaks.....ohh ya, I have quite a few at the beginning, and boy was that annoying! I have to drain the tank,hand thread it, then fill the tank just so it would break again over and over a again until I got the cut stable. I was able to keep my patience and just reminded myself it was going to be a slow process regardless.
As far as the burn went, it took a very very long time. It drove me crazy with how slow it was cutting, but it was working and I just had to let it be. Since I had a test piece I programmed it just as I plan to cut the actual part. Its a 1inx3inx12in chunk and I have my profile nested into the stock where I can burn in from the side cut the profile and go out the other to get the main slug off. The actual electrode I need to burn it approx .375 x 2.625 x 12in, so I have it centered in the block in the X axis but I left myself some room in the Y incase I need to move back and cut another one.
Funny part here...I think this whole part should be done on the CNC Mill and I have no idea why we aren't trying that but whatever. My boss thinks I am going to tab this and cut it off...then blend it somehow...I think I'm going to make a fixture then take it to the CNC for the blend job...at least I hope because, I tried a small as possible tab like .050 wide and .100 long and it started to break down when I came down the second side of the tab. Luckily it held on and I was able to get the main slug off. If there are any suggestions there I am open to all!
I took the advice and went for a one pass cut. At first when I was experiencing the most wire breaks I was cruising a whopping .005-.006 per min, flushing was almost maxed out, but I could hear the cut sputtering every now and then, and it would start to short out in some spots. I ended up dropping my ON time a couple and raised my OFF time plus a larger SV and it took my cut down to .003 per min. This was the sweet spot though, and I was thrilled to get there. I didn't have anymore wire breaks or short circuits throughout the rest of the cut.
I am actually quite happy with the first attempt. The finish I got off of one pass is waaay better than I expected. If I lay the part down and indicate it, I see about .002 taper end to end and I'd say .0005 little dip in the middle. Completely surprised me to be honest, I also had added .002 to my offset and over all the part is close to dim all round. At the lowest point I measure it at .3735, so i'll have to run it on the CMM to truly see where I'm at and if it will be acceptable.
I'll be sure to post an update when I get the final part finished.
Thanks again!
Here's a photo of my test cut. Don't mind the junk on the left side, it is where I ran into some of the pre existing mill cut and had to break a piece off.
Attachments
Last edited:
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi again JZ:
You sir, have earned those bragging rights.
You are now officially an EDM Guru.
So stick out your tits and be PROUD.
Oh yeah...while you're basking in the warm afterglow, go demand a nice raise from your boss.
Seriously though...fine job well done.
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
You sir, have earned those bragging rights.
You are now officially an EDM Guru.
So stick out your tits and be PROUD.
Oh yeah...while you're basking in the warm afterglow, go demand a nice raise from your boss.
Seriously though...fine job well done.
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
Bud Guitrau
Aluminum
- Joined
- May 8, 2006
- Location
- SoCal
Totally agree with Marcus. Amazing job (and patience)!Hi again JZ:
You sir, have earned those bragging rights.
You are now officially an EDM Guru.
So stick out your tits and be PROUD.
Oh yeah...while you're basking in the warm afterglow, go demand a nice raise from your boss.
Seriously though...fine job well done.
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
Bud
Appreciate the compliment! Honestly, without getting on here and digging thru some threads, plus your guys input, I didn't have a clue where to begin or much confidence, so thank you again.
As far as a raise, I'd love one, we all would but I don't want to push my luck!
Hope to be burning on the actual part sometime this week, all goes well, maybe I'll have a better chance at that raise.
As far as a raise, I'd love one, we all would
but I don't want to push my luck!Hope to be burning on the actual part sometime this week, all goes well, maybe I'll have a better chance at that raise.
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