Homing vs. Printing height difference

fcwilt

@1d1 said in Homing vs. Printing height difference:

@fcwilt That is what the indicated Z height is when the probe triggers. When I then check the distance to the bed, it requires an additional -4.9mm for the nozzle to reach printing height. Yeah, the distance the printer attempts to print is likely 4.9mm above the bed. This where I'm confused, exactly.

The indicated height is simply the value you entered into the G31 command. It is "telling" the firmware that the nozzle is 15.3 mm above the bed when the probe triggers.

If it is actually 15.3 + 4.9 use that value instead.

Frederick

1d1

When I do that (for the 10th time) I get a probe not triggered response when running a G32. I know the probe triggers when pushed because the LED on the board goes off. If I increase that trigger value, it still doesn't work because the probe remains too high. If I decrease the trigger height value to 15.22 I get a calibrated mean deviation response after G32. All Good. I then enter an M500 to save it. And when I go to print, The extruder prints in midair about 4.9mm above the bed.

jay_s_uk

How did you measure the trigger height?

1d1

I take the indicated difference from the point at which the probe triggers, remove the probe, and then lower the extruder until the nozzle touches the bed. The total distance is appx. 20mm (15.3 + 4.9). When using that value, the probe doesn't trigger when G32 is used. If I lower the trigger height value to 15.4, the probe triggers. Then I get a mean deviation report, hit M500, and go to print... 4.9 mm above the bed... again. Pretty frustrated here.

fcwilt

@1d1

If you home the printer and then move to Z=0 where does the nozzle end up, height wise?

Frederick

1d1

4.53mm above the bed

jay_s_uk

@1d1 have you read this?https://duet3d.dozuki.com/Wiki/Calibrating_a_delta_printer#Section_Measuring_the_trigger_height

fcwilt

@1d1 said in Homing vs. Printing height difference:

4.53mm above the bed

Do you have a line like this in your config-override.g file?

M665 R106.35 L215 B180.8 H224.5 ;Set delta radius, diagonal rod length, printable radius and homed height

If you do change the H parameter to H229.4

If not change that line in your config.g file.

Then re-boot, home and move to Z=0 and see what happens.

Frederick

1d1

@jay_s_uk Many times.

1d1

@fcwilt I'll try that. Though I have already in the past, maybe we're closer to the solution...

jay_s_uk

Well you're doing to z probe offset the wrong way.

Heat the bed
Heat the nozzle
Take the nozzle down until it's touching the bed (using paper to determine when they're touching)
G92 Z0
G1 Z30 (to move the nozzle away from the bed)
Fit the probe
G30 S-1

And the offset will be spat out

fcwilt

@jay_s_uk

That is certainly one way but it is not the only way.

Frederick

1d1

OK. Adding 5mm to my overall homing height didn't alter results, but I left it that way and did the G92 Z0 process again and we have ignition. A number was spat, changes were splatted and results regurgitated. PETG flows properly once again. Thank you both (all?) for your help.

fcwilt

@1d1 said in Homing vs. Printing height difference:

OK. Adding 5mm to my overall homing height didn't alter results, but I left it that way and did the G92 Z0 process again and we have ignition. A number was spat, changes were splatted and results regurgitated. PETG flows properly once again. Thank you both (all?) for your help.

Adding the 5, reboot, home and still Z=0 came out at 4.9? Very odd.

Well, anyway, don't leave us in suspense - what number was "spat"?

Frederick

jay_s_uk

@fcwilt thats what it says to do on the wiki

fcwilt

@jay_s_uk said in Homing vs. Printing height difference:

@fcwilt thats what it says to do on the wiki

I understand and it is a perfectly fine solution.

Frederick

1d1

Sorry - had to step away. The homing height in M558 is locked at 229.4 and the number spat is 19.43. Still needs a teensy bit of fine tuning, but the grand picture includes printing again.