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Topics - Backlash

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General Mach Discussion / Backlash control on Y axis is bad
« on: February 28, 2007, 02:37:38 PM »
Hi,

The backlash on the Y axis does not work properly.
When the backlash option is turned on (only 20% of Max) the Y axis step will output a high rate of pulses,(only in certain parts of the G-code) causing the motor to loose steps. I hooked a logic analyzer to the direction and step pins to verify the it was not noise. I found the the signals were clean, and captured the waveform when the problem happens. When the problem happens, the Y steps pulses are 38.6 us appart. This is about 25.7 KHz, which is my pulse frequency-- Hmmm.. This causes the motor to miss steps.

Note: This does not happen in Jog mode. The backlash function works perfect in the Jog mode. It only happens when running G-code.
Turning the backlash function off fixes the problem, but now I have backlash issues. I tried 5% and 100% of max values, but it makes no difference.

I noticed that someone else posted this exacted problem. This maybe the reason for a lot of posts of "ugly circles" posts.
I could send you the captured waveforms from my logic analyzer if you need them.

Thanks,
Robert



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