Nozzle gets smashed against the bed

MJCT

I now realise that Z in the machine control dashboard, should be pointing 0.03 in the first case and 0.02 in the second, not 0.3 and 0.2

Still need your help

droftarts

@MJCT said in Nozzle gets smashed against the bed:

G31 P25 X25 Y0 Z0.213 ; set Z probe trigger value, offset and trigger height

You've gone from a probe trigger height of 3.2mm to 0.213mm, which seems very close. Did you follow the guide here to set the probe offset? https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe#Section_Calibrate_the_Z_probe_trigger_height

Jog the nozzle down until it is just touching the bed or just gripping a sheet of paper. If the firmware doesn't let you jog it down far enough, send M564 S0 to disable axis limits.
Once you have the nozzle touching the bed, send command G92 Z0 to tell the firmware that the head is at Z=0
Jog the head up by 5 to 10mm
Send command G30 S-1 to report probe offset.

The first two points set the nozzle at Z=0. The second two determine the probe offset.

Ian

MJCT

@droftarts
0.213 was the value reported by G30 S-1 command twice in three attempts. Should I cut one decimal and impute 2.13 at G31?

And yes, I followed the wiki guide. I always do. The problem is that the guides usually don’t help me much. In this case the guide doesn’t provide any real example, neither it states the units in which the information is provided by the G30 or the units you must input at G31.

That’s why I am so thankful to this community. You have been fantastic. I´m not lazy, is just that WIKI guides suck big time.

fcwilt

Hi,

If the reported value was 0.213 that is what you use.

But that value is only valid if the Z position is correct, meaning Z=0 has the nozzle just touching the bed.

Frederick

MJCT

Tried “G31 P25 X25 Y0 Z2.13” instead of “G31 P25 X25 Y0 Z0.213” ... no surprises, it smashed the bed again!

MJCT

@fcwilt
Yes I understand that.

droftarts

@MJCT All units are millimetres. You can change to inches with G20, but this is supposed to be used only in gcode files, not for machine calibration.

Can you check that, after homing, if you send a command like G1 X100 Y100 Z0, the nozzle is not slamming into the bed? Or that the reported position of the nozzle is sensible. If that's the case, it's a problem with the gcode file. Check you haven't set any Z offset in Cura. Post you gcode file so we can check it.

Ian

fcwilt

@MJCT said in Nozzle gets smashed against the bed:

Tried “G31 P25 X25 Y0 Z2.13” instead of “G31 P25 X25 Y0 Z0.213” ... no surprises, it smashed the bed again!

Is the pin dropping when you issue a G30 command? The probe has to touch the bed and retract for the motion to be halted.

Frederick

MJCT

@droftarts Yes I understand that we are using SI units, supposedly mm, but I not sure of anything right now

@droftarts said in Nozzle gets smashed against the bed:

Can you check that, after homing, if you send a command like G1 X100 Y100 Z0, the nozzle is not slamming into the bed?

Funny (not really), yes it did slammed into the bed. But I did everything by the book (or not). Nozzle at the centre of the bed, just barely touching the bed (paper can still slide under), sent G92 Z0, pull bed down 15mm, sent G30 S-1, changed G31, sent M999.

The only thing I didn’t do is the "config-override.g " thing, because I just can’t find that file any ware

MJCT

@fcwilt

@fcwilt said in Nozzle gets smashed against the bed:

Is the pin dropping when you issue a G30 command? The probe has to touch the bed and retract for the motion to be halted.
Frederick

Yes, sent G30 command, the probe deplyed, bed moved up until it touched the probe than stoped.

fcwilt

@MJCT said in [Nozzle gets smashed against

Yes, sent G30 command, the probe deplyed, bed moved up until it touched the probe than stoped.

OK then at point what is the displayed Z position? Does it appear to be accurate?

Frederick

MJCT

Where do I find "config-override.g " file, maybe is because of that. Maybe it always overrides my new imputes.

fcwilt

@MJCT said in Nozzle gets smashed against the bed:

Where do I find "config-override.g " file, maybe is because of that. Maybe it always overrides my new imputes.

If it exists it is right there next to config.g.

Frederick

MJCT

@fcwilt

@fcwilt said in Nozzle gets smashed against the bed:

If it exists it is right there next to config.g.

Well, to me, it never existed. Still it appears at the wiki

“9. Open config-override.g and check that there are no G31 commands in it. If you find any, delete those lines and save the file.”

And it’s not the first time that I see the wiki page referring to it, and that’s why I don’t trust wiki

droftarts

@MJCT said in Nozzle gets smashed against the bed:

Where do I find "config-override.g " file, maybe is because of that. Maybe it always overrides my new imputes.

You don't have M501 (read stored parameters) in your config.g, so it won't be loading config-override.g (which is usually in the sys folder, where config.g is). You'll only have a config-override.g if you have sent an M500 to store

How old is your BL Touch? I have heard that after a while they can get 'sticky', with the pin not deploying fully, and giving variable results. I believe you can take them apart and give them a clean.

Ian

MJCT

I think I found the reason why I never see a config-override file...

*****“dc42 ADMINISTRATORS 10 Jun 2017, 23:18

If you created your config.g file using configtool, you will have selected whether or not config-override.g is processed.”*****

When I did my config with the config toll I didn’t select the “Read config-override.g file at end of startup process” box at “General”.
One doubt less, but still doesn’t solve my problem

fcwilt

@MJCT

The file config-override is created if you have executed a M500 command.

I don't have one as created it to have access to the two line of code that were generated by heater tuning.

I copied those lines into config.g and deleted config-override.g

Frederick

MJCT

My BL is new. Version 3.1, the pin deploys fully and the results are consistent.

The problem seems to be that the values that I impute are not taken in to account and the real distance from the nozzle to the bed doesn’t correspond to the distance displayed at the Dashboard for the Z (dashboard always displays a positive value, say 2mm, when the nozzle is already touching the bed).

fcwilt

Hi,

After you do a single G30 does the reported value seem to be correct? Does the gap between nozzle and bed seem to match the reported value?

Frederick

MJCT

@fcwilt ~

Nop, last 2 times that that I sent G30 the nozzle smashed the bed