Encoder issues

[EetuKuikka]

Hello Tom,

We purchased a Morbidelli author 502 cnc machine which had been converted to run on mach3 with Kflop and Kanalog control boards. The machine worked fine for months until it started misbehaving. Every time we powered the machine on it would run all the axes to their endstops and stop working. We figured the control board might have been fried doe to a thunderstorm so we swapped the Kanalog board to a new one. This seemed to solve that issue. The machine now starts up and everything works ok.

Our current problem has something to do with the servo rotary encoders. When we try to run a program, it looks like everything works, but the axises gradually develop a position error while running the code. The machine finishes the program, but in the end the G54 0,0 position of all axises has shifted a few centimeters. The amount it shifts is not constant but the direction seems to be the same every time. We can make the error happen if we run a command like G0 X1000 and then physically grab the z servo encoder and try to shake it with my hand. Then Z servo starts spinning but so does Y and X loses its accuracy. Sometimes the error does not happen at all. Mach3 seems to think everything is ok. Vibrations definitely make the issue worse.

We have not tried changing any parameters in the Kmotion configuration. Is it possible some settings got lost when we swapped the board?

Regards,
Eetu

[TomKerekes]

Hi Eetu,

If you return to the same encoder position and the axis is not in the same physical position then the encoders have some problem.

Possibly a grounding problem, noise problem, cable problem, or encoder alignment problem. Sometimes when an encoder cable is constantly flexed it can fail so that in specific positions wires open and the encoder miscounts.

But this is usually in one axis only. It seems your problem is common with all axes. I can't think of a mechanical problem that would cause problems will all axes.

Sorry for no simple solution.