delta Z motor goes clunk, regardless of motor or driver

achrn

It occurred to me to check some other input shapinng:

M593 P"zvd" F37 clunks more softly and at different movements: in the 1200 acceleration case (which clunks under zvddd other than 12-26) it clunks for movements above xval=22

M593 P"zvdd" F37 clunks intermediately loudly, but at different movements: in the 1200 acceleration case (which clunks under zvddd other than 12-26) it clunks other than xval=8-24

So I also tried varying teh frequency

M593 P"zvddd" F74 and M593 P"zvddd" F18 both clunk and not-clunks differently to F37

droftarts

@achrn Thanks. I've raised an issue for this on Github: https://github.com/Duet3D/RepRapFirmware/issues/1015

Ian

droftarts created this issue in Duet3D/RepRapFirmware

open Input shaping on linear delta causes Z motor clunking at specific bed locations #1015

SPAX

Hello. I have a duet2Wifi Delta. Have the same problem after update on 3.5.2, 3.5.3 Release Candidate 1 problem too. When I switch off input shaping M593 P"none" all axis moving without clunk.
Do you have solve for this bug?

dc42

@SPAX thanks for your report.

TBH although it appears that there is a bug in this area, we might not fix it for the following reasons:

Input shaping has been completely reimplemented 3.6 than in 3.5 and works much better. We have no reports of a similar bug in 3.6.
It's likely that tracking this bug down would require substantial effort, which ultimately would be wasted because the 3.6 code is completely different.
Delta printers typically have little or no need for input shaping because their resonant frequencies tend to be higher.

Of course, if anyone else tracks this down and supplies a fix that we can validate, we will gladly include it in a future 3.5.x release.

If you are brave enough then I suggest you try RRF 3.6.0-alpha.5 on your machine. Or you can wait for 3.6.0-beta.1 which I estimate is 2 weeks away.