Nozzle offset with bltouch?

tonyp

Soo... I've just got round to configuring my duet coming over from marlin. I'm struggling with my bltouch and nozzle offset. Basically the nozzle is scraping the bed. I've set the prop trigger height but as my bltouch mount is printed I suspect I need an offset from the bed to the nozzle? so it goes X below the triggered height? Can you advise on how I determine this and the correct G-Codes to set it?

PaulHew

Hi,

Have you seen this document?
https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe

Helped me loads

HTH Paul.

tonyp

Thanks Paul, I have and I’ve set the trigger height. No difference, driving me a little mad . I just want to be able to print!

Someone has suggested changing the trigger height to offset the nozzle, but this doesn’t seem natural to me

JamesM

When I set up and calibrate my BL-touch I use a certain piece of paper between the nozzle and the print bed when setting my zero Z-height....basically building in a nozzle offset. Then I do the z-probe tests and set the BL-Touch trigger height in the config. Then it's just a few test prints, usually just on a skirt around a print to fine tune the bl-touch trigger height that last few .05 mm.

Phaedrux

@tonyp Can you post your config files and homing files? It's hard to suggest anything without seeing what's actually going on.

tonyp

Sure, see attached
0_1559344561723_bed.g
0_1559344569108_config.g
0_1559344590705_homeall.g
0_1559344604658_homez.g

Any suggestions welcome, still getting my head around G-Codes.

Phaedrux

G31 P25 X42 Y-4 Z0.321

Your trigger height seems abnormally low for the BLTouch. When installed correctly it should be closer to 2mm. The BLTouch instructions say that it should be installed so that the base of the probe body should be 8mm above the nozzle tip.

M558 P9 H2.5 F60 T6000

The dive height of 2.5mm is a little low. Start with 5mm to start with.

G1 X-47.5 Y14 F6000    ; go to first bed probe point and home Z
G30    ; home Z by probing the bed

The coordinates of your probe point seem a little odd. You should try to place the probe in the center of the bed for best results.

tonyp

Thanks, I had just went through the doc https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe zeroed the probe, then set the trigger height of 0.140 as tested 5 times I had done it previously without the zeroing :|. I am thinking of offsetting the trigger height to a middle ground of 0.250 as a test since with 0.140 the nozzle is way to far of the bed now.

I've measured by putting the tip onto the bed, then using verniers measure the distance between the bed and the flat base of the BLTouch and that is 8.32 (docs say 8-8.5).

Can you explain the Dive height a little more sorry

They sure are odd, I've converted an Ender 3 into a duet/titan areo direct extruder as per attached photo of the head setup

Phaedrux

@tonyp said in Nozzle offset with bltouch?:

I had just went through the doc https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe zeroed the probe,

Question: When you are testing the trigger height, are you moving the probe to over the same XY coordinate as where the nozzle tip was when you zero it?

@tonyp said in Nozzle offset with bltouch?:

Can you explain the Dive height

Dive height refers to the z height that the print head will move to before a probing move. It needs to be high enough to allow the BLTouch pin to drop down and settle completely before making contact with the bed.