Axis changes direction randomly

Hey all,

I've recently installed LinuxCNC to run my DIY 3-axis router through a HobbyCNC EZ Driver board. I use CamBam to generate G code for 2.5D sheet cutting, and have run into a problem while executing G codes. Occasionally (once or twice in a 500 line G code) the router will start to move for a short distance in the opposite direction to that specified in the G code and then correct itself. The problem happens randomly (at different places when the same G code is run sevral times) and sometimes doesn't happen at all.

The problem crops up when executing different G codes, and I've looked at the G code produced by CamBam and there's nothing I can see in it that would cause the issue. Since the problem occurs randomly and independently of the G code (I think), I think it's a runtime issue, which would point to something going awry in either LinuxCNC or maybe in the HobbyCNC board.

Has anyone experienced this before? Is it a latency issue or something in the way I've configured LinuxCNC?

Steve

Hey John,

Thanks for the response. I'll check for loose wires, but all three axes have experienced the problem so it's perhaps more likely a configuration error. I haven't run the stepper test but will try it on each axis to see what I get. I'll post the results for future reference.

Steve

Most likely the issue is on your drivers box. Maybe some reference point that is making a bad contact and it is common to all axis (when you say that the issue happens on all 3 axis, it happens at the same time?)

I really do not think a configuration can make that happen random.

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Obrigado, emcPT.

I think I found the cause of the problem. Earlier, the latency test for my computer suggested my max jitter was about 11000, but today I connected the computer to the internet and was able to perform a much more stressful latency test that resulted in a max jitter figure of over 500000. Clearly, my hardware is unsuited to run LinuxCNC reliably, so it's time to find a better linux box...

Thanks again for the suggestions!

Steve