Duet 2 Wi-Fi Delta Sporadic Skewed Prints

bkdfkup

Hi forum members

Hoping for some assistance with an odd problem that has me chasing my tail. I have a Tevo Little Monster delta printer that is controlled by a Duet3D 2 Wi-Fi board.

The problem I'm facing is that some prints are drastically skewed, and some prints are near enough to perfect. I can re-slice and re-print the models that skew and get the same skewed outcome, yet the test models that print perfectly ALWAYS print perfectly, even if re-sliced. All models are being sliced using the same slicer (Cura version 5.7.1) and same settings

I've been through the dimensional measurements and the 6-point auto calibration multiple times and everything I can see checks out.

For the fact it can (when it feels like it) output a dimensionally accurate print, I feel the dimension config is correct, and this also seems to indicate the hardware is doing what it should (or at least what it's told) with no broken/loose belts or missed steps. The motors also do not appear to be overheating as has been a suggestion on other forum posts, and are only luke warn to the touch.

Attached are a few photos to illustrate the issue. One model that skews (a functional part that is a rectangular case that is 142mm wide, 62mm deep, and 34mm high, with 2.4mm walls), and the other (a 100mm x 50mm tube with 1.5mm walls) that prints as intended. I have also tried a 100mm x 50mm square tube to see if repeated acceleration / deceleration was the cause, but it also printed well.

So I'm at a loss as to where to look next, and would be grateful for any guidance. In the interim I'm trying to narrow down ways to replicate the issue with test prints by adjusting height, width, wall thickness etc.

Thanks in advance.

dc42

@bkdfkup firmware version?

bkdfkup

@dc42 good point sorry. Versions are:

Duet 2 WiFI 3.5.0-rc.1
Duet WiFi Server 2.1beta4
Duet Web Control 3.5.0-rc.1

To add to the above, i have increased the wall thickness of the test tube from 1.5mm to 2.4mm resulting in an extremely skewed print. The primary difference i can see is infill. With only walls making up thickness the model it prints correctly, with infill it skews.

jay_s_uk

@bkdfkup I would updated to 3.5.4 and see if it's still an issue

dc42

@bkdfkup yes please do that. We don't support RC versions of firmware once the stable release is out. In fact the release notes for 3.5.0-rc.4 at https://github.com/Duet3D/RepRapFirmware/wiki/Changelog-RRF-3.x-RC#reprapfirmware-350-rc4-changes-since-rc3 list layer shifts as one of the bugs fixed.

bkdfkup

Thanks. @jay_s_uk and @dc42 I have just applied the latest FW and am printing another test print. Will let you know how it goes.

Revisions are now:
Duet 2 WiFi 3.5.4
Duet WiFi Server 2.2.0
Duet Web Control 3.5.4

bkdfkup

First print after updating firmware went well using the same gcode as the last skewed print. No more skews, just some over-extrusion on the seam that needs some tweaking.

Hopefully the RC firmware was the issue. I'm running a second test now, and can hopefully call this one resolved.