[JerryBurks]

I have the MK3/4 (latest software/firmware) and use the wireless MPG. Everything works just fine, except when I push the "return to zero x/y" buttonon the MPG, the machine almost goes there. The y-position is usually zero, but the x-position often is like 0.233 mm or 0.203 mm. Not a showstopper but kind of annoying....

JB

[awerby]

Is it relying on a switch to tell it when it's arrived? There's often some inaccuracy in home/limit switches, especially the mechanical type. This can be minimized by careful adjustment, or replacement with an optical switch which is more accurate.

[PlanetCNC]

Button on MPG just triggers command "Machine/Move/Axis To Zero/XY". This command is just "G00 X0 Y0" g-code.

[awerby]

It might be lost steps. Does the error increase with time - if you've run a program and tell it to return to zero (using the command line, not the MPG), is the error always the same, or does it get worse the longer it's run?

[JerryBurks]

Button on MPG just triggers command "Machine/Move/Axis To Zero/XY". This command is just "G00 X0 Y0" g-code.

Admittedly I did not try using the same command from the screen button. It may or may not do the same as with the MPG and I will try. This effect is not new to the latest version. It has been doing that for a long time, maybe since I am using the MK3. I was just too lazy to post the question since it is not such a big problem.

One thing I do know is the machine reliably returns exactly to zero x / zero y when the G0 X0 Y0 command is executed from the gcode program.

Maybe I should take a video clip sometimes to show what is happening.

[JerryBurks]

Thanks...I know it is not lost steps because the controller would not even know if there are lost steps. What happens is when starting with an x/y position is somewhere out there at the machine, usually because I get the bit out of the way for change or changing material. Then I push the "go to x0/y0" button on the MPG to get the spindle back to the local zero and the machine does that. But often the x and y position display on the MPG as well as the PC screen end up not as zero x and zero y, but e.g. x=0.203mm or x=0,233 mm or similar small distance.

I never noticed that when the loaded g-code program tells the machine to go back to x=0 y=0 at the end of the program.

[ScorpionTDL]

what are your steps / mm settings?
Depending on the way you set your 0 position the machine might not be able to reach the position based on your settings. Therefore it goes to the nearest position its able to reach.

[CNCMAN172]

You could have some backlash in your axis, so it would not return exactly to zero

[ScorpionTDL]

You could have some backlash in your axis, so it would not return exactly to zero

You would not see the backlash in the gui. Only on the machine

[JerryBurks]

what are your steps / mm settings?
Depending on the way you set your 0 position the machine might not be able to reach the position based on your settings. Therefore it goes to the nearest position its able to reach.

133 steps/mm - or one step is 0.0075mm. The return error is usually way bigger than that.
Also, like I mentioned before, when there is a G0 X0 Y0 at the end of the gcode, then the machine will always return EXACTLY to X=0 Y=0.

When there is a residual small value for X, it does not help pushing the MPG button another time or clicking the screen button for "return to x=0 / y=0". The number will stay the same (on the MPG and on the screen) and the machine does not move. When I get to it, I will take a video of this effect.

[PlanetCNC]

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