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Messages - henryjm

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General Mach Discussion / Re: Stepper motors loosing postion.
« on: September 24, 2008, 01:15:03 PM »
I had a similar problem with Z axis couple of months ago. After milling some parts the Z-axis ended up higher then when started. The difference depended on the lenght of the G-code and on it's complexity. I tried everything starting from disassembling the machine (Joe's CNC), checking the HW etc. Finally I localized the problem to be in the SW, i.e. PC, not sure if it was XP or Mach. I tried to minimize the possible area of the problem. One of the last things I did was that I was making single microsteps with Z-Axis motor (jogging). I have realized that when turning 1 step right and then one step left everything was OK, but when turning 1 step left and then 1 step right, the motor actualy made the "right" step to the left and only a second right step turned the motor right. That explained why the Z axis shifted slowly up during the milling. Basically, during each change of rotation from left to right the position shifted by 1 microstep (or actually 2 microsteps, because the second microstep turned it to the previous position). It seemed to be a Mach problem. I checked the Mach setup and tried everything like you playing with an acceleration etc. Finaly, I realised (and I'm sorry I don't remember it exactly because it was couple of months ago) that in Config->Ports&Pins->Motor Output (or Output signals, not sure) I had some pins which I used for the motor control (step, dir) toggled on other positions as well. Those positions were NOT (!) enabled so I thought it doesn't matter, nevertheless removing the pin numbers from these positions fixed the problem. I can't guarantee you've got the same problem but it would be worth to check it.

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