Z axis wont stop

brian

I was able to control the z axis to stop and set the offset. But now after updating firmware i can no longer stop the z axis. I used G92 Z0 when bed is at the right distance from nozzle and the ir sensor is lit, but it doesnt do anything, again. Is there some other code that needs to go with this?

dc42

@brian said in Z axis wont stop:

I was able to control the z axis to stop and set the offset. But now after updating firmware i can no longer stop the z axis. I used G92 Z0 when bed is at the right distance from nozzle and the ir sensor is lit, but it doesnt do anything, again. Is there some other code that needs to go with this?

If you are using a Z probe such as the IR sensor for Z homing, then you shouldn't be using G92. Instead you need to set the G31 Z parameter to the sensor trigger height. See https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwareCartesianPrinter#Section_Homing_Z.

brian

@dc42 Ok i managed to get the bed to stop before hitting the nozzle, but now it doesnt adjust the height as in the second G31 command. And there seems to be some eroneous code after homing that moves the bed up and down and the x and y axis move around for no reason, which never occurred before updating firmware. Is there some start up code in the firmware or what could be causing it, at one point it pushes past the x endstop and clatters before continuing. I've commented a few things out to see if they are the culprits.

; Endstops
M574 X1 Y1 Z1 S1 ; Define active high microswitches
M558 P1 X0 Y0 Z1 H-1.0 F200 T5000 R0 ; smart IR Z probe, used for homing Z axis only, dive height 3mm, probe speed 200mm/min, travel speed 5000mm/min, no recovery time

;M558 P1 X0 Y0 Z1 H5 F320 T6000 ; Set Z probe type to unmodulated, the axes for which it is used and the probe + travel speeds --uncommented june 25
G31 P500 X-11.0 Y-0.5 Z-1 ; set threshold and offsets jun 21 changed to negative values to see what happensno change
G31 P500 X0 Y0 Z3.0; Set Z probe trigger value, offset and trigger height higher numbers moves bed closer to nozzle --uncommented june 25
;M557 X25:175 Y25:175 S25 ; Define mesh grid

dc42

Check whether you also have a config-override.g file with a G31 command in it.

brian

@dc42 No, dont have that file.

dc42

Please confirm that you are using a G30 command to home Z as described in the wiki secotin that I linked to, not a G1 S1 Z command.

brian

@dc42 This is my homez.g file; however it doesnt work from panel due, never has, i just use homex and homey and leave the z where ever it is at the time, most often i move it 50mm away from nozzle. Does the firmware call these files before each print?

G91 ; relative mode
G1 Z4 F200 ; raise head 4mm to ensure it is above the Z probe trigger height
G90 ; back to absolute mode
G1 X100 Y100 F2000 ; put head over the centre of the bed, or wherever you want to probe
G30 ; lower head, stop when probe triggered and set Z to trigger height

dc42

Your homez.g looks OK to me. You will need to home X and Y before you can home Z.

The firmware doesn't home the printer when you start a print, but your slicer start script may do that, or you can do it in the start.g file.

brian

@dc42 I didn't really think the firmware would run any kind of startup code. I checked my slicer's, s3d, start code and it runs G28, so i ran G28 from panel due console and it is making the weird start up sequence, which wasn't weird before updating firmware. I guess i should delete that from the slicer start code and see what happens.

brian

Its still doing weird things. If i run G28 or G30 it runs code that just isnt there. The bed goes up and down twice and the x and y move around.

dc42

If you have upgraded across several versions of firmware, you may have old deployprobe.g and retractprobe.g files that need to be deleted from /sys on the SD card.

brian

@dc42 Ok i did have both files, have deleted. Will advise if changed.

brian

Yes deleting those two files seems to have solved the erroneous movements. Thanks!

brian

@brian However now if wont move the bed close to the nozzle, no matter what settings is use. It doesnt seem to understand negative values or simply converts them to positive. I need the bed to move up to the nozzle but it will not, always wants to move down or away from nozzle. Very frustrating.

dc42

Have you set the Z probe trigger height correctly in the G31 command in config.g?

brian

@dc42 Yes the bed now rises to the correct height then drops down. I've reset the height with G31 at both positive and negative values, which doesnt seem to have an effect. I have also tried both pos and neg values with M558 H value. Both these command seem to convert neg values to pos. I've also set the Z value in S3D with doesnt do anything either. I've moved the G31 before and after the M558. I've commented out one or the other, still no effect at raising the bed to correct position.

M558 P1 X0 Y0 Z1 H0.0 F320 T5000 R0 ; smart IR Z probe, used for homing Z axis only, dive height 3mm, probe speed 200mm/min, travel speed 5000mm/min, no recovery time
;M557 X25:175 Y25:175 S25 ; Define mesh grid

G31 P500 X0 Y0 Z-5.0; Set Z probe trigger value, offset and trigger height

dc42

The M558 H parameter sets the height at which probing starts for most types of Z probing move. Negative values make no sense. The default is 5mm but higher values are useful sometimes especially when performing initial calibration of a delta printer.

The G31 H parameter is the height of the nozzle above the bed when the Z probe triggers. It should be positive for most types of Z probe, but slightly negative for a nozzle contact probe.

If you send G30 to probe the bed at the current XY position, when the probe triggers and the movement stops, the Z reading in DWC or PanelDue or returned by M114 should be that G31 Z value.

HTH David

brian

Ok thx, so dive height means the height that probing starts, I can understand that but not sure why it matters and i'm ok with that.

Using T3P3Tony's suggested endstop settings, (which is the first time homeall from panel due actually works);

So i homeall via panel due, ran G30 from console and then M114 and got Z3, entered that in config.g for G31 z value. I started a print from where the nozzle was (not homed) and that didnt work, just air printed. So i homed all then started print and that did work. Still printing.

T3P3Tony

@brian I think you are missing some steps lets continue the conversation on the other thread:

https://forum.duet3d.com/topic/5858/z-axis-will-not-move-close-enough-to-nozzle-to-print/7