Z-offset calibration

Max Arnold · 30 Sept 2017, 20:00

Hello DC42,

we met at the TCT Show and it was a pleasure talking to you.
We talked about a automatic z-offset calibration method, when one has 2 or more Hotends.
Would it be possible to integrate a automatic z-offset calibration, when using a direct contact probe into the firmware?
So I have 4 Hotends and I would like to have command where the same position is probed by all four Hotends and such the z-offset is determined.

Thank you in advance for your reply.

Kind Regards

Max

dc42 · 30 Sept 2017, 20:21

I think we could make G30 S-2 probe the bed and adjust the Z offset of the current tool by the difference between the configured trigger height and the recorded height when the probe triggers. Would that meet your requirement?

Max Arnold · 1 Oct 2017, 07:26

Hello DC42,

yes that would meet my requirements. Is it then possible to to store that z-offset value in G10 in the config.g file ?
Thanks again for your fast response.

Max Arnold · 16 Dec 2017, 14:18

I am not sure how or where the Z-offset is stored, but it is only stored temporarily. This means after a restart, the values are lost, so my guess is that the offset is stored in the flash memory. Would it be possible to store the value permanently in the G10 command in the config file?

dc42 · 16 Dec 2017, 15:06

In firmware 1.20 any tool offsets that were found by probing are written to config-override.g when you run M500.

Max Arnold · 16 Dec 2017, 16:35

Thank you. This solved my problem

stephenc · 16 Dec 2017, 17:57

Hi max I'm curious how your printer setup with 4 different heads. can you share your build?

Thanks
Stephen

stephenc · 16 Dec 2017, 20:02

Id like to see wiki covering this feature.

So if those z offsets is then saved in G10 does that mean probing all 4 hotends can only by done once and your routine for every print would be to probe only yiur primary hotend?

Thanks
Stephen

Max Arnold · 17 Apr 2018, 00:25

Hello StephenC,

I am very sorry for the late reply. Concering your last post, yes exactly that is true. I will share my build soon. Currently ironing out some issues.

Meanwhile DC42 I found a flaw with the z-offset of two nozzles or more. When swichting between the hotends the z-offset does not take affect until the next move which means that the when the printhead moves the z-offset is gradually adjusted. Is it possible to have to have some kind of command that would trigger the z-offset adjustment earlier,so that i can implement it in the tpost script?

Thanks.

Max

Max Arnold · 17 Apr 2018, 00:34

Well I found a work around. One can lower the bed using relative positioning (G91) and the when the printhead moves the z-height is adjusted again with the z-offset.

dc42 · 17 Apr 2018, 09:05

@max-arnold said in Z-offset calibration:

Well I found a work around. One can lower the bed using relative positioning (G91) and the when the printhead moves the z-height is adjusted again with the z-offset.

That is exactly what I would suggest. Even a no-motion command such as G1 Z0 (after G91) should suffice.