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Limit Axis resolution

03 Jul 2018 09:02 #113302 by Ralf
Limit Axis resolution was created by Ralf
TLDR: Is it possible to set a a lower limit for the axis resolution, e.g. 0.01mm?

I have got my hands on a Roland PNC-3000 CNC Mill, which I have modified to make it usable with LinuxCNC.

The mill has a build in XYZ display, which works by monitoring step and direction lines to the stepper drivers, so it updates even if it isn't the native controller that moves things around.

Problem is that the display gets out of sync with the coordinates in LinuxCNC, and I suspect a rounding error in the mill's counter logic, as the display is only 0.01mm resolution, but the hardware is 0.005mm.

The build in controller always pulses the steppers twice, which could be a way around a bug in the counter, I have seen others suggesting this as well, the suspicion is further strengthened by the fact that I can move the mill around all day with G0, using non decimal coordinates, but as soon as I run actual gcode or jog the mill around, the display looses sync.

So if I could limit the resolution in LinuxCNC, this would be a quick way to confirm this issue.
06 Jul 2018 10:49 #113554 by andypugh
Replied by andypugh on topic Limit Axis resolution
What do you mean by "resolution"?

The position commands out of the motion controller are double-precision, so have about 15 significant figures.

The step generator will convert this to steps, the resolution there is set by the microstep size.

If you switch your LinuxCNC display to show "actual" rather than "commanded" then you will see the position rounded to steps. (probably, I am making assumptions about your hardware setup)
07 Jul 2018 06:26 #113638 by Ralf
Replied by Ralf on topic Limit Axis resolution
I was thinking of doing the same double step hack that Roland does in their firmware, but that was mostly to confirm the issue with the counter logic in the mill.

In the meanwhile I found another way to confirm that it is the display in the mill that is off, and not the mill itself or LinuxCNC.
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