Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: sillycon on April 09, 2013, 12:25:15 AM
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I'm running into a very perplexing (for me) issue when running the code generated by the text engraving wizard on mach3.
I've tried both Helvetica and IsoCp and both seem to have problems for me. If I recall correctly, Helvectica is the selected font for "TEST TEST". "Trust" was done with IsoCp, but note that the "S" characters are wildly misshapen in both. Also, the vertical portion of the "T" is not centered on the horizontal portion. The "O" character is also quite misshapen (it's square rather than round or oval), along with the middle "half" lines on E's and F's smushed into the top or bottom line on smaller characters.
I've tried character heights of .0625" (not shown), .125 ("TRUST"), and .500 ("TEST"). Spacing is 100%, DOC is .005", I'm using a .010" single-flute carbide cutter at 4500rpm. I'm doing test cuts on 3003 AL stock. The "TEST TEST" engravings are rough due to having been done too fast (8IPM). I'm now going at 2IPM ("TRUST").
This is on a converted HF mini-mill (X2-size) utilizing a G540, 380oz stepper motors, 48v power supply, and a CNCFusion kit (incl. re-packed ball nuts and screws). There's a total of about 30-mins run time on the machine (it was converted before ever being powered up). 25,000hz, and the driver tests always come up excellent (sits at 25,000hz occasionally "blipping" to 24,999 or 25,001hz).
Up to this point I've only done simple "linear" sorts of jobs where I was widening a slot by .030" or other such "simple" operations however I'd like to be able to start using the machine more completely.
I re-trammed the X axis today (it's about .007" off at the moment. I'm going to redo it after doing the "bolt" mod to make the adjustments more precise and easily obtainable). I haven't come up with a good way to tram the Y yet. Even still, that doesn't explain the square O's and such.
Where should I start to look to resolve this issue? Slow down the acceleration and max speed on the motors? Does this seem like an issue with dropped/skipped pulses, or do I need to look elsewhere?
I've been fussing with this on and off for a couple weeks and I'm sending up the white flag.
Thanks in advance!
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Do you have backlash compensation turned on or off? If on, is it accurately set to the actual value for your screws? You could try an alternative engraving package to see if that gives the same problem - F-Engrave is free, and I have used it successfully to engrave text. It has the nice feature that it deals with multiple lines. It generates g-code that you can then import into Mach to run, this will check if the problem is in the Mach wizard or your setup.
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I never entered into the backlash compensation window that I can recall, so it's likely whatever the default for Mach3 would be (I would assume "off", so perhaps my assumption that it's "off" is my problem right there?).
I'll give F-engrave a shot as well to sanity check. Thanks for the suggestion.
Though, frankly, I have to think that the issue is in my setup because I can't imagine something like this sliding for so long past 10k+ users.
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Does the engrave text display correctly in the toolpath display ?
(;-) TP
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Yes, display text appears to be very nice, smooth, and symmetrical (yet another reason I expect the problem is in an unknown place in my setup).
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Then the problem is in your machine, Probably in motor tuning setting too aggressive and you are loosing steps.
(;-) TP
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Alright, thanks for confirming my suspicion. I'll go back to square one on the motor tuning and see where that takes me.
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It might just be worth checking that backlash compensation is indeed turned off....and could your problem be caused by uncorrected backlash in the screws?
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I'll also verify that the backlash compensation is off, thanks; and I'll double check the backlash on the machine as well.
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Looks like a purely mechanical engineering problem to me. Backlash on the Y axis maybe.
Cheers
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Hey all. Just to update, I had backlash issues on both the X and Y -- the X ballnut had come loose from the saddle, and the two jam nuts on the Y axis leadscrew had also come loose allowing the screw to move. I was finally able to identify the issue(s) when I slowed the motors down to see if it was a motor tuning issue.
After tightening both up properly, the engraving has cleaned up quite a bit. I still have a bit of an issue, but it's *FAR* better than it was. I'm going to have another go at the machine to figure out where I still have some slop later this week or this coming weekend.
Thank you all for the nudges/pointers in the right direction; it's been a HUGE help.