Unreliable Z height calibration on V-Core 3 w/BLtouch & Mini 5+

fcwilt

I have noticed something odd.

I gave you a very simple, edited version of the homeall.g file you first posted.

I did not cancel baby-stepping in the code I posted for you.

Homing does not cancel baby-stepping unless the homing code has the command to do that.

In your example print file you have this:

G1 X250 Y250           ; move to the XY reference point for G30
G30                    ; set the Z-0 Datum
M290 R0 S0.09          ; set baby-stepping

So the first print after power up sets baby-stepping (from 0.00 to 0.09) but it does so after the G30.

For the next print I am thinking baby-stepping is still in effect (it remains at 0.09) which changes the results of G30 and the nozzle ends up farther away from the bed on the next print(s).

And that is consistent with what you are reporting.

Normally you don't want to set baby-stepping in a print file. To fix first layer Z issues you would adjust the Z Trigger Height parameter in G31 which would cause the G30 to set things so the Z position is correct for printing the first layer.

Remove the M290 from your print code and adjust the Z Trigger Height parameter in G31 to get the Z height correct.

If I had put M290 R0 S0 in the homeall code I posted you wouldn't be seeing this issue - my bad - all attempts to print would have been too close to the bed.

Frederick

fcwilt

@juliann

Add these two lines at the beginning of your homeALL.g file and your homeZ.g file:

G29 S2                           ; cancel mesh bed compensation
M290 R0 S0                       ; cancel baby stepping

Frederick

juliann

@fcwilt

Hi Frederick! @fcwilt

Very good news, you found the solution!
I applied your suggestions and now the issue is totally fixed!

Thank you so much for all the help provided.

Julián.

fcwilt

@juliann said in Unreliable Z height calibration on V-Core 3 w/BLtouch & Mini 5+:

@fcwilt

Hi Frederick! @fcwilt

Very good news, you found the solution!
I applied your suggestions and now the issue is totally fixed!

Thank you so much for all the help provided.

Julián.

Glad we were able to sort things out.

Frederick

dc42

@fcwilt said in Unreliable Z height calibration on V-Core 3 w/BLtouch & Mini 5+:

For the next print I am thinking baby-stepping is still in effect (it remains at 0.09) which changes the results of G30 and the nozzle ends up farther away from the bed on the next print(s).

Thanks for identifying this. It sounds as though babystepping is affecting the behaviour of G29 and G30 probing, and I think it would be better if it didn't. I will add this to the work list.

dc42

Looks like G30 is working correctly after all. If I run G30 to establish Z=0, send M290 Z1 and then G1 Z0, the nozzle sits 1mm above the bed. If I then run G30 again and then again send G1 Z0, the nozzle is still 1mm above the bed.

fcwilt

@dc42 said in Unreliable Z height calibration on V-Core 3 w/BLtouch & Mini 5+:

Looks like G30 is working correctly after all. If I run G30 to establish Z=0, send M290 Z1 and then G1 Z0, the nozzle sits 1mm above the bed. If I then run G30 again and then again send G1 Z0, the nozzle is still 1mm above the bed.

Well it seems my understanding of the interaction of M290 and G30 was wrong.

But it seemed to explain what the OP was seeing and the suggested changes did fix the problem.

Which then leaves the original question as to why the first print never worked but subsequent ones did.

Frederick

PCR

@dc42 Same here. Babystepping and G30 works.

Nurgelrot

@juliann Just a note about your config unrelated to the Z problem. Don't you have your current too high for the motor on the LGX extruder? Max current should only be 0.7A. Building the same printer as you (using a SuperPINDA vs BLtouch) and comparing configs

juliann

Hi

@nurgelrot!
Good catch! yes, that was wrong for sure. Thank you very much!

@dc42 @fcwilt @PCR
Thank you very much for the additional tests, clearly I had something wrong in my original config, everything is still working fine by the moment.

Julián.

sinned6915

@juliann sorry i have been afk.. a couple of other suggestions-

you might want to consider seperating homing/leveling out from you print file.
make a seperate macro and use that at the start of a print 'session'

that way if you have to cancel and restart a print, you are not going through the whole procedure of homing/leveling.

you mentioned trying to print with PETG- i suspect you came across some old posts about how hard and finnicky it can be. most of that advice is just rubbish. dont get intimidated.

petg wants slower and no cooling. I use the same filament profile for PETG as PLA only temps are 235 and cooling 0. I may have bumped retract/destring a hair.