Question about G31

fcwilt

Hi,

What does the Z parameter of the G31 command do?

Does it affect the values computed by the G32 command?

After making the needed preparations I ran G32 and then G29. The resulting height map was good.

However something changed the H value in M665 and at X=0 the nozzle was 0.4 above the bed.

What happened?

Thanks.

Frederick

dc42

The Z parameter of the G31 command tells the firmware how high above the bed the nozzle is when the Z probe triggers. See https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe#Section_Calibrate_the_Z_probe_trigger_height.

fcwilt

@dc42 said in Question about G31:

The Z parameter of the G31 command tells the firmware how high above the bed the nozzle is when the Z probe triggers. See https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe#Section_Calibrate_the_Z_probe_trigger_height.

I was not clear. I understand what it is doing in G31 - what I don't understand is where it is ultimately used.

For example does it play a role in the values computed by G32?

Or to put it another way if the Z value is wrong in G31 what will malfunction as a result?

Thanks.

Frederick

dc42

@fcwilt said in Question about G31:

Or to put it another way if the Z value is wrong in G31 what will malfunction as a result?

If you use the incorrect Z value in G31, and you use the Z probe to home Z, or to do delta calibration, bed levelling or mesh bed compensation, then the Z=0 position will not correspond to the nozzle just touching the bed. When you print, the nozzle will be too close to the bed or too far away from it.

fcwilt

@dc42 said in Question about G31:

@fcwilt said in Question about G31:

Or to put it another way if the Z value is wrong in G31 what will malfunction as a result?

If you use the incorrect Z value in G31, and you use the Z probe to home Z, or to do delta calibration, bed levelling or mesh bed compensation, then the Z=0 position will not correspond to the nozzle just touching the bed. When you print, the nozzle will be too close to the bed or too far away from it.

Thank you - that is very helpful.

Frederick