Sodick wire EDM taper issues

M. Roberts · Nov 12, 2021

Guys,

I am having issues cutting a straight hole. I am attempting to wire some 0.1582" +/- 0.0002" holes in a 0.210" thick plate; they appear to be tapered by about 0.0005" per pin gauge. All of the guides are less than a month old, so I don't think that is an issue. And, the carbides are fresh, and the head has been aligned; I just re aligned it, and made some test cuts; I'm not satisfied with the results. One rough cut, and two finish cuts...that should do (and has done) the trick....I don't understand...flushing is adequate; sealed on the bottom; upper nozzle is about 0.75" off of the part due to clamping....any suggestions??

Thanks,
Mark

implmex · Nov 12, 2021

Hi Mark:
If the hole is tapered and not angled, the alignment of the upper guide relative to the lower guide cannot be the issue.
Remember, the upper and lower guides do not move relative to one another (without a taper command), so if they are misaligned they will make an angled hole, not a tapered one.

There are only a couple of ways to get the result you're seeing and you need to find out which is the most likely problem.

Making a taper normally requires a taper command...are you SURE the upper head never moves when you walk around the bore?
If you've eliminated that, the only thing that remains is that your erosion is uneven across the thickness of the part.

If your control settings are not correct, you can influence how the part will be cut and whether you get a taper that's large on the top, small on the top and whether your cut is straight, hourglassed (small in the middle) or barreled (big in the middle).

The Chinglish instruction manual for my machine describes which settings to alter (on MY control) when you encounter this problem.
So for a bigger bore on top, my manual says to increase OFF time and AFF (auxiliary OFF time).

For a bigger bore on the bottom my manual says to increase SV (the servo voltage) and reduce the FR (feedrate).

It does work...I've used it to correct tapers due to uneven erosion, but I don't know if your machine will behave the same.
I have a CHMER machine vintage 2011.

Another thing you can try is to jack up the wire speed and do more skims.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

JZ. · Nov 12, 2021

M. Roberts said:
Guys,

I am having issues cutting a straight hole. I am attempting to wire some 0.1582" +/- 0.0002" holes in a 0.210" thick plate; they appear to be tapered by about 0.0005" per pin gauge. All of the guides are less than a month old, so I don't think that is an issue. And, the carbides are fresh, and the head has been aligned; I just re aligned it, and made some test cuts; I'm not satisfied with the results. One rough cut, and two finish cuts...that should do (and has done) the trick....I don't understand...flushing is adequate; sealed on the bottom; upper nozzle is about 0.75" off of the part due to clamping....any suggestions??

Thanks,
Mark

Mark,
Do you see it "hunching" in either of you skim passes? If you are confident in your offsets, you can adjust your SV by .5-1.0 at a time on your second pass if its struggling to cut.

If you are tight at the bottom that is not totally uncommon. implmex gave some good advice on what can cause this.

How is the flushing out of the bottom head? Usually set to just shoot out over the flush cup.
I typically adjust my SV and V in my 2nd and 3rd passes if I am snug in the bottom. You can adjust your V by .5-1.0 at a time.

Are you using PIKA settings?
From my experience you shouldn't really have to adjust any conditions on the final pass but I typically do a 1 rough and 3 skim passes.

plastikdreams · Nov 12, 2021

implmex said:
Hi Mark:
If the hole is tapered and not angled, the alignment of the upper guide relative to the lower guide cannot be the issue.
Remember, the upper and lower guides do not move relative to one another (without a taper command), so if they are misaligned they will make an angled hole, not a tapered one.

There are only a couple of ways to get the result you're seeing and you need to find out which is the most likely problem.

Making a taper normally requires a taper command...are you SURE the upper head never moves when you walk around the bore?
If you've eliminated that, the only thing that remains is that your erosion is uneven across the thickness of the part.

If your control settings are not correct, you can influence how the part will be cut and whether you get a taper that's large on the top, small on the top and whether your cut is straight, hourglassed (small in the middle) or barreled (big in the middle).

The Chinglish instruction manual for my machine describes which settings to alter (on MY control) when you encounter this problem.
So for a bigger bore on top, my manual says to increase OFF time and AFF (auxiliary OFF time).

For a bigger bore on the bottom my manual says to increase SV (the servo voltage) and reduce the FR (feedrate).

It does work...I've used it to correct tapers due to uneven erosion, but I don't know if your machine will behave the same.
I have a CHMER machine vintage 2011.

Another thing you can try is to jack up the wire speed and do more skims.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Wouldn't a taper be an angle? Please school me on this one lol.

Not sure if your alignment tool is the same type as mits but check the carbide contactors, ours are out of alignment by a thou. It's doesn't really cause much of an issue, but if I was doing under a few tenths I'd be concerned. But really, check your checker. I don't even know how they got out of alignment...but whatever.

007Rob · Nov 12, 2021

plastikdreams said:
Wouldn't a taper be an angle? Please school me on this one lol.

I think what he's saying is that if the wire alignment was out but the hole was cutting "straight", you would end up with a hole where the top and bottom are the same diameter, and a gage pin slides thru nicely but the centerline isn't perpendicular to the workpiece.

Since the top and bottom are different sizes it makes it seem more likely to be an issue with cutting conditions/settings.

Of course if you programmed a hole to cut with a taper that's a bit different since the machine will cut a taper all around the perimeter

plastikdreams · Nov 12, 2021

Ah I get it not like this / \ like this //

Shane030173 · Nov 15, 2021

Are you using BSA or taper offsets? If so, are you sure your table to next and table to program are correct?

M. Roberts · Nov 16, 2021

Guys,

I did make some changes that apparently was detrimental to the quality of the holes; I slowed down the wire feed in an effort to conserve (go green, right?) and I upped the on time.

On the suggestion of Implmex, I did increase my off time, and sped up the wire...it did help; I am at about 0.00015" per side taper, measured via the tenth pins. I ordered replacement C and C1 guides; they were not replaced when I changed out the upper and lower guides.

No, I have no taper call out in my program, its not that easy...

Mark

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