Wire EDM Power Settings
I have a Hansvedt DS-2 wire EDM and need some tips on power settings. I recently replaced the wire
contactors (not the guides) which has made a huge performance difference. I ran the machine for 15 hours and have not had a wire break and of course we are all happy when the wire does not break. More flushing has also made a huge difference. The Hansvedt DS=2 uses above water flushing.
For the most part I have learned to use the Hansvedt by reading the owners manual and lots of trial and error. Now that I have made progress with reducing wire breakage I'm wondering if someone could tell me
how and where to tweek the power settings for reducing cut time. I'm using .012 dia wire and cutting through 1/4"
A-2. These are all roughing cuts no skims.
Power settings are:
% ON 2.5
FEED RATE 8
Wire speed 4
How can I change these settings for a faster cut rate? Seems like % ON and AMPS has the greatest effect on cut rate and wire breakage
Wire EDM power supply settings are a bit of a tricky bastard to try to set up from first principles.
On most (probably virtually all) machines they are put together as a packaged set that you can choose from depending on the material type, the material thickness, and the quality of surface finish you need.
Once you define these variables you can either look the manufacturers settings up in a table, or on more modern machines, you call them up when you input the 3 variables I described above. (there are other variables you can select for too, but they're mere details.)
Once you start cutting, you can modify the settings on the fly, to enhance the performance or overcome flushing constraints or mitigate wire breaks, but when you do so, you start to make the process less predictable, and one of the things that suffers is the size of the slot you produce, which, of course affects accuracy.
Every machine and every work condition is unique, so a strategy that works brilliantly on one machine may not work at all on another, but here's my (limited) experience:
On my old Sodick, opening up the servo gap was the most reliable way to solve a persistent wire break problem, but it slowed down the cut considerably.
On my new Chmer, the servo gap is far less influential, and I tend to start by dropping ON time a notch.
Sometimes increasing OFF time is better, sometimes an AN or AFF adjustment works better, and the decision which to try usually reverts to my instincts about the flushing conditions the job is constrained by, but there's always a good dose of empirical farting about involved.
Improving cut speed is the obverse of that coin.
When you think about how the cut actually happens, your strategic fiddles become a bit more understandable:
You're trying to keep a clean slot while creating as much cut debris as possible per second; the two goals are obviously mutually contradictory.
Opening up the servo gap creates a bigger slot, easier to flush and therefore kinder on the wire but at the expense of the wire having to burn all that extra material which slows the cut down (kind of counterintuitive I know, when I just said you want to make as much cut debris as possible per second but it's the stuff you remove from the cut path that counts for cut speed, not all the stuff you remove from the sides of the slot).
Turning up the ON time allows you to use more of the pulse to actually make a spark and speeds you up while turning up the OFF time gives the dielectric a bigger recovery time and allows more time within a pulse to flush out the crap you've just made but slows you down.
The gap sensitivity settings (AN and AFF on the Chmer) work similarly, but respond to the voltage across the gap and will advance or retard the cut by feedback to the ballscrews that drive the motion, rather than just making a more or less aggressive spark.
So, depending on the machine, you have a bunch of settings you can play with, all of which perform similar functions.
Something the Hansvedt has, that is not adjustable so far as I know on either of the machines I've used, is the amperage and the pulse frequency.
On both my wires, these are part of the basic cutting conditions I select from my cutting table, and cannot be modified on the fly.
On a last note, as you've discovered by changing the power contacts, the condition of the machine plays a huge role in how fast it cuts.
You can look to other things too, beyond the power contacts.
Discharge cable conductivity, flushing nozzle setup and condition, and water quality are big influencers, and an often overlooked one; wire diameter.
Bigger wire means bigger slot means more work to progress a given distance, but bigger wire also means more power can be poured into the cut making more cut debris (of the kind you wanted), but more crap to flush and on and on.
I recommend buying Bud Guitrau's book on EDM; it lays all this out far more clearly than I've done, and is a worthwhile read.
Implant Mechanix – Design & Innovation - home
Vancouver Wire EDM -- Wire EDM Machining
Thanks for the informative reply. I retired from my day job five years and one of the things I miss is
coffee brake. I would take coffee brake with old friends and someone always had a new computer or working with some new piece of equipment the company purchased. I miss those conversations because this is when I learned what was new in state-of-art. Communication with people like you is so very helpful since I no longer have a coffee brake group.
I really like my Hansvedt DS-2 even though it is not the latest technology. I enjoy the machine and it brings work into my shop that I would not otherwise receive. I have gone 20 hours now without a wire break. My problem is I like to fiddle with things to make them run better or faster. Then I'm mad when the wire breaks.
One thing for sure, cranking up the flushing preasure and new wire contactors have made the machine more productive. I keep a notebook on every piece I EDM. I record all the cut times and document power settings.
I did purchase BobCAD V23 and used it to program the last two jobs. Takes time and patience to learn
BobCAD but I think it is great now. I have a little notebook for BobCAD as well to refresh my memory in between uses. With BobCAD there is a sequence of operations to get a Solidworks CAD drawing to machine code. Miss a step and it will not work. I'll be using the notebook for a while. BobCAD tech support is top notch.
A V-block tool I made a while back. First posting I think.
More pics and tooling
I had a look at the tooling you've built, all looks very nice!
With regard to power settings; does Hansvedt publish the settings for various materials and thicknesses in a table, or are they stored on the machine control?
You should be able to set up a scrap block and try out various settings to see what happens.
Try to get some cut times that you can express as square inches of cut per hour and compare the effects of the settings on your cut speed.
Go with 1" thick material so the calculation is easy.
If you're getting somewhere around 15 square inches per hour you're doing pretty good for that vintage of machine.
If you're getting below 10 square inches per hour, you might well be getting to be in need of some maintenance; if you're down below 5 square inches per hour, there's something wrong.
This is for a typical tool steel; the standard for North America seems to be D2, for Asia it's something called SKD 11.
The above is a very crude rule of thumb, but it's about what my Sodick was rated to do with 0.010" plain brass wire; it was a 1996 machine.
On thinner material you might be able to go a bit faster.
Regarding wire breaks; if you have an auto threader you can tolerate more breaks than you can without, but they're not supposed to be a big deal if you get one once in a while; it simply means you're at the edge of the envelope for the cutting conditions and flushing for that part of the job.
If you never get one, you're probably wasting wire by cutting more slowly than the machine is capable of; if they're happening frequently, you're pushing too hard or there's something wrong with the machine.
But don't get too upset at wire breaks, they're part of the turf with wire EDM.
Implant Mechanix – Design & Innovation - home
Vancouver Wire EDM -- Wire EDM Machining
I'm glad you posted that info. I'm depressed tonight because a customer complained about how long
a wire EDM job took. I have already done what you describe in the way of test cuts in 1" thick material. The best rate I could come up with is 1.7" /hour. There must be something wrong. This is exactly why
I made this post. I have no experience with wire EDM other than the Hansvedt I own. I thought 1/7"/hour
was normal for a machine like this one. I spoke today with a friend that has newer wire machines that can cut 12"/hour.
I'm going to call the Hansvedt technician tomorrow and see what he says about cutting rates.
Well, the Hansvedt technician was already in my area so I askied him to stop by and check out my wire EDM and give me some pointers to optimize the machine. My problem has been "Operator Error". The technician explained how the flushing nozzels should be set a couple of thousanths from the workpiece. Where did I have them, the upper nozzle was 1/2" away. I knew flushing was important in all EDM work but I assumed as long as the wire was not breaking off the machine was optimized. WRONG.
The owners manual for the Hansvedt DS-2 says it rated for 14 sq in/hour
Last edited by JimGlass; 06-12-2012 at 07:46 PM.