delta Z motor goes clunk, regardless of motor or driver

droftarts

@achrn Okay, I set up a bench test with a 6HC on 3.5.1 with 3 large NEMA stepper motors, running standalone. I ran the clunking test from your post here https://forum.duet3d.com/post/340420
I get the rough/clunking Z move on the 4th and 8th move of that macro, just like your video. I noticed you were running input shaping, and the clunk disappears as soon as I turn this off with M593 P"none" and rerun the test. So looks like an input shaping issue. I didn't try any other changes to your config.g. I'll report it to @dc42 for investigation.

Ian

achrn

@droftarts Aha! Excellent, thank you. I was just about to figure out how to try it standalone, following @Phaedrux 's request. I confirm that if I run mine SBC mode without input shaping I have no clunks. Since the cause has been narrowed this far and repeated by someone else, I'm not inclined to work back through old firmware versions, unless really likely to make teh difference between solving it and never resolving it, but I could try some older versions if it will make a big difference to tracking down the problem - please let me know.

Input shaping as the 'cause' stacks up because I only relatively recently put on a toolboard, and it's only when I got the toolboard (with the accelerometer) that I enabled input shaping. So although I hadn't made the connection that that's when clunks started, with hindsight it's very credible it was at about that time. I don't run it fast enough to really need input shaping anyway - the quality enhancement is debatable, and it's more a case of enabling it because it's there, so disabling it is not a hardship.

Thanks everyone for input, I'm now clunk free (though I also have a printer in pieces, so I need to spend some time re-assembling).

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

closed 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.

SPAX

@dc42 Hello!
I updated firmware to 3.5.4 and have same problem still...

droftarts

@SPAX Please try RRF 3.6.0-beta.2: https://github.com/Duet3D/RepRapFirmware/releases/tag/3.6.0-beta.2

Ian

T3P3Tony

@achrn @SPAX

Please try 3.6Beta3 to confirm if the issues is resolved or not

https://forum.duet3d.com/topic/37289/software-version-3-6-0-beta-3-now-available

droftarts

@achrn @SPAX I've gone back and tested this 'Delta clunking' issue. I set up a 6HC with 3.5.3 and reproduced the clunking, updated to 3.6.0-beta.4 and reran, no clunking. I don't think we're planning on fixing this in 3.5.x, as IS has been rewritten in 3.6.

If you're facing this issue in 3.5.x, it can be resolved by turning off input shaping.

Ian

achrn

@T3P3Tony said in delta Z motor goes clunk, regardless of motor or driver:

@achrn @SPAX

Please try 3.6Beta3 to confirm if the issues is resolved or not

https://forum.duet3d.com/topic/37289/software-version-3-6-0-beta-3-now-available

Apologies for the long delay to get back to this. I didn't try any of the betas, but I've done some multiple test cases now with 3.6.0-rc.1 and no clunks for any case. I've only tried ZVDDD input shaping (that's what I was using that clunked), but I have tried varying the other things that seemed to influence it and not triggered anything untoward.

Thanks.

apak

@achrn I can confirm that I have also ZVDDD configured on a 3.5.4 delta, and also have some clunks issues.

Will update this afternoon to 3.6 RC and test