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Z and A axis problems
« on: April 08, 2008, 01:51:05 PM »
I am having a problem with Mach3, version 2.0.060. Attached is the gcode of the file I am running. Runs with no errors or anything.

The code creates a simple diamond with a line in it, around a shaft.

What happens is that is as A is turning into position, Z is descending. It should get into X,A position over a diamond point, and then plunge down to Z-.005. What is happening is that A is not in the right position yet before Z starts to plunge down. It is so bad sometimes that Z is at -.005 and X has started to move before A gets to where it needs to be, so there is a big gouge approaching the diamond.

I attached a photo of the problem. The diamonds on the left are correct, and the diamonds on the right show the problem.

The problem seems to get worse as the program goes on. The last few diamonds in the program are the worst, although the code is the same. Nowhere in the gcode is there any line with A and Z on the same line, but there are times that both are moving concurrently.

Any suggestions/ideas? I have used this machine/controller with no problems before, just recently it started having these problems.  I didn't make any config changes (that I recall anyway).

Thanks
Scott

Offline jimpinder

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Re: Z and A axis problems
« Reply #1 on: April 08, 2008, 03:02:32 PM »
It is possibly something to dowith CV - constant velocity. This is where, towards the end of a move, as one axis decelerates, the axis for the next move accelerates.

Try knocking off CV and use Absolute Stop instead, where one axis must stop before the next moves.

See Config/General Config/column two - Constabt Velocity/Absolute stop.
Not me driving the engine - I'm better looking.

Offline Hood

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Re: Z and A axis problems
« Reply #2 on: April 08, 2008, 03:05:15 PM »
can you post your xml.
Hood
Re: Z and A axis problems
« Reply #3 on: April 09, 2008, 11:43:19 AM »
XML is attached.

I don't think it has to do with constant velocity. I thought so too initially. I am using a new CAM program (Rhino) that automatically puts in a G61. I switched back and forth between 61 and 64, took it entirely out of the program with no change. The last time I run I used the attached XML, and exact stop is selected, and there is no G61/64 in the program. I was having problems with this before, so the CAM program is not the source.

I am having another issue that may be related. I can manually jog around, go into MDI mode, and enter g0 x0y0, and I should get back to my X0Y0. Sometimes I do, and sometimes I don't. It sometimes stops at (AFAIK an arbitrary) position on the way back to 0. The display doesn't say 0 (it displays an accurate position other than 0) and entering G0X0Y0 in MDI doesn't do anything. I flip back and forth between program run and MDI modes, maybe jog a bit, and go back into MDI and then it will go to X0Y0. Hasn't been a huge problem, just a bit frustrating. I don't know if this problem started concurrently with the gouging problem or not.

Thanks!
Re: Z and A axis problems
« Reply #4 on: April 09, 2008, 05:11:50 PM »
I did some more playing. The problem is in the XML someplace. I am uploading a backup of the XML, and that seems to be working fine.

There are 16 differences between the 2 files. Some of them obviously are unrelated to the problem, and some mean nothing to me.

Now, when I make a A movement, it moves in angular movements. In general config, I have A is angular unchecked.

For the part that I gotta get out tomorrow, angular is fine (even better actually). How do I get A back to linear movement?

I'm getting closer. :)