Duet homing changes!

[A Former User]

config-overide.g and bed.g?

[Veti]

just checking. you swapped the motors for 0.9 degree motors?

[CTR]

Yes, changed motors and some mechanical parts too to reduce noise etc.

[CTR]

Deleted Config-overid.g as I am trying to produce an accurate calibration. All this started with a scaling problem where the accuracy was out by as much as 4% on the Y axis compared to X depending where on the bed the print was done!

[droftarts]

@ctr said in Duet homing changes!:

G29 S1 ; load previously saved bed calibration file

It's got to be your bed calibration as this is the last line of the homedelta.g. Perhaps it was done when probe height was set incorrectly, so it's offset from where Z is homing to. Try commenting this line out of your homedelta.g, and run homing a couple of times, then see if it moves down the 7mm. Then redo your bed calibration.

Ian

[CTR]

Cheers Ian, that cured it.
Can you please elaborate on the bed calibration file? Where is it and what is it called?

What is the precise procedure for auto Delta calibration? I'm not having much luck with it as the scaling is not correct after running it.
I enter M500 after calib' which I understand writes the results so each time the Duet boots up, it reads the corrections. Is this correct?

Thanks again for those who replied.

[CTR]

BTW. The mechanics and geometry of the machine are very accurate. I'm good at mechanics, but lacking in software/ firmware skills!

[droftarts]

What firmware version are you using? If it's 2.03, you need to update to 2.04RC1 as:

Bug fixes:
When auto delta calibration adjusted the delta radius and/or the diagonal rod length, it made an incorrect adjustment to the homed height
https://github.com/dc42/RepRapFirmware/blob/dev/WHATS_NEW.md

Probably best to follow the guide: https://duet3d.dozuki.com/Wiki/Calibrating_a_delta_printer and come back with any questions. This covers delta calibration and bed mesh compensation, the latter of which is activated by G29 S1. You should be able to see the bed map by clicking on the 'Machine Control > Height Map' option in the Duet Web Control. The file should be heightmap.csv in your sys folder on the SD card.

There's a couple of things to check in your config.g. Usually, if either delta radius or diagonal rod length incorrect, you get rounded movement of the nozzle, and parts are either concave or convex.

M665 R134.311 L266.6 B120 H298 ; Set delta radius, diagonal rod length, printable radius and homed height - rod was 267

Generally, you should be able to accurately measure rod length (joint centre to joint centre) so it's unlikely this needs adjusting. It's harder to measure the delta radius accurately, so unless you know it is correct (from CAD drawing) using the 6- or 8-factor delta calibration works best, usually; see https://duet3d.dozuki.com/Wiki/Calibrating_a_delta_printer#Section_Setting_up_the_bed_g_file

However, it's also possible that your steps per mm on the belts is incorrect - there's a note in there, which doesn't make much sense to me! This might cause the scaling issue.

M92 X160 Y160 Z160 E110 ; Set steps per mm (was 160 on 02/04/19) 156=whole steps for 0.3-0.15-0.075 layer heights

What type of belt and pulley size are you using? You can use the 'Steps per millimeter - belt driven systems' calculator here to check: https://blog.prusaprinters.org/calculator/

Ian

[CTR]

Hi Ian,
Appreciate the reply.
The note was for my interest only! it related to thoughts on layer height relative to whole stepper steps (only relevant on Cartesian machines) .
Firmware is 2.0(RTOS) (2018-06-05b3) - always worried about updating firmware in case something gets screwed up! Should I upgrade? Is it foolproof?
Thanks for the thought about belt and pulley steps/mm etc. I'm well versed in this area and written a very thorough Excel file for calculations for belt motion systems including ratios, belt lengths, pulley centres etc. Excluding belt stretch, I can confirm that the values are correct.
Neil

[Veti]

@ctr said in Duet homing changes!:

always worried about updating firmware in case something gets screwed up! Should I upgrade? Is it foolproof?

you can go back to a previous version.
chris riley just did a video about updating. its step by step.
https://www.youtube.com/watch?v=gYxAxz7AwfE

[CTR]

Hi Veti
Thanks for the link. Looks super easy until you look at the revision Ian mentioned; this doesn't have a zip file, so which files do I need to upload? Is it all the files and do each one individually?

As I said: I'm lacking in firmware/software confidence.

[Veti]

here is a more detailed guide.
https://duet3d.dozuki.com/Wiki/Installing_and_Updating_Firmware

use the Duet2CombinedFirmware.bin in that case.