Geometric patterns on sidewalls of prints

Hi all,

I use a custom dagoma discovery 200 with marlin firmware 1.0 (I should try to upgrade) and PrusaSlicer 2.0.
My prints are really good in size / shape / strength. Everything is calibrated, extrusion appears to be perfect in flow and width.
There's only one strange detail : some geometric patterns appear on the sidewalls (all the sidewalls) as you can see on the picture. These are slightly raised, just noticeable under the fingers.

I thought at first it may come from the perimeters / infill junction, but they don't match the infill pattern + I tried to print with only one perimeter and no infill -> same result.
I also tried to rotate the part 45°, thinking it could be a linear bearing issue -> same result
I tried to change the printing speed (50 or 70 mm/s) -> same result
I tried to disable the auto cooling settings since it changes the printing speed based on layer time (really not convinced about this one but ok, let's try) -> same result

It seems like when the printer goes from A to B, the extrusion is split into segments, but it doesn't seem to be random. The pattern is "too geometric", and always the same on 2 prints of the same part.

I didn't make all possible tests yet. I'm thinking about disabling linear advance for example. But I was wondering if someone already experienced this issue.

Thanks for your help

It's most likely a mechanical problem:
[all3dp.com]

---

http://www.marinusdebeer.nl/

DRV8825 driver chips?

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Thanks for your replies.

I don't think it's a mechanical issue since the pattern position does not depend on the part position or rotation on the print bed + it's too "perfect" to be a resonance issue or something.
You can see on the picture attached that it looks like ellipses drawn at regular intervals.

The board is a Melzi 2.0 with A4982 drivers

Okay then it might be something called 'salmon skin'. I am not familiar with the drivers but google the term and see how it compares

---

http://www.marinusdebeer.nl/

Ah ! Thanks for giving a name to this issue !
A quick search tells me to add smoothers between the drivers and the motors.

I'll check that and give a feedback

Hi all, it's been a while.

It did was salmon skin. I added smoothers to my printer and the quality is much better now.
I upload a picture to show the difference.

Thank you very much for your help !

Quote
alvinflumox
Hi all, it's been a while.

It did was salmon skin. I added smoothers to my printer and the quality is much better now.
I upload a picture to show the difference.

Thank you very much for your help !

Hi, thanks for getting back! It's nice to see there is some improvement, but it looks as if there is still something showing.

Which TL smoothers did you buy? I'm curious as the ones I once bought didn't have any effect on my printing quality so yours already seem to work better.

---

http://www.marinusdebeer.nl/

Hi Ohmarinus,

Yes, there's still something visible depending on the lighting but it's barely noticeable under the fingers.
I bought makerbase smoothers, I found them here makerbase TL-smoothers