How do these surface artifacts appear when 3d printing this onshape part?

kees_bijker

Hello Onshape community,

I did look around for existing questions on this matter, but did not find any, so apologies if I missed it.

I created a part in Onshape, very simple in fact. It has a flat surface without any features at all except 2 ribs growing towards an angled second plane. Fully confined model, no blue lines anywhere. I exported it as STL and printed it.

I use Prusa slicer 2.5 and never have a problem.

This model however shows weird paths on the top surface, resulting in what looks like artifacts that should not be there. In all my years of modeling in Openscad, and now a few weeks in Onshape, I have never seen this ever! Please see the pictures.

I kind of think I did something wrong, since I am only working with Onshape for some weeks, but not sure. Maybe the ribs "grew" into the object rather then to its closes surface. This could have caused an internal feature causing the slicer to interpret is as something other than infill, but again not sure. It does not show anything on the base of this flat part.

By the way the model is totally functional so it has not resulted in a failure. It just looks really bad and if you were to make something that has to look ok on the top surfaces, this would be a failure.

1) screenshot of the slicer showing the artifacts. 2) part in Onshape 3) the print as it happened.

MichaelPascoe

Hi @kees_bijker, Nice project!

I haven't had this happen with my prints. Please share a link to your document so we can take a closer look.

_anton

For science, you could try to scale up by 1%. If that removes the weirdness, this is an artifact of how the slicer handles that particular surface. Slicers aren't perfect; I've seen Cura silently miss whole layers. 

Besides that, +1 to Michael's post.

S1mon

I would look at the STL file. I'm betting that the weird artifact curves are along vertices of the tessellation. Without seeing the files I can't tell, but it looks like there's some rounding error because the coordinates are on a sloped surface in the CAD, but rotated flat for the build.

kees_bijker

hi @MichaelPascoe

Thanks for having a look.

When you ask to share the project, you mean simply in the document itself press share? Do I have to link something to here?

kees_bijker

Ok I think I musunderstood.

https://cad.onshape.com/documents/1f55960c596fe3f64461824c/w/a2b6fa3953eb686c3a7684f2/e/edb7a766c83c534961d2864d

The document is already public so this should be enough.

The artifacts happen in the stl  generated from version 1. In version 2 I modified the base by extending the front and making a cutout in the rear section. That time the artifacts do not appear.

I hope I am clear with this explanation.

MichaelPascoe

Strange, the Onshape model looks fine and the STL export seems to be in good condition for my printer software (CHITU Box). You could try exporting it as a Parasolid, then using a 3rd party site to convert it to STL to see if that gives you different results.

kees_bijker

Ok I think I musunderstood.

https://cad.onshape.com/documents/1f55960c596fe3f64461824c/w/a2b6fa3953eb686c3a7684f2/e/edb7a766c83c534961d2864d

The document is already public so this should be enough.

The artifacts happen in the stl  generated from version 1. In version 2 I modified the base by extending the front and making a cutout in the rear section. That time the artifacts do not appear.

I hope I am clear with this explanation.

MichaelPascoe said:

Strange, the Onshape model looks fine and the STL export seems to be in good condition for my printer software (CHITU Box). You could try exporting it as a Parasolid, then using a 3rd party site to convert it to STL to see if that gives you different results.

Hi Michael,

Thank you for your time again.

You showed the Version V2, this is modified and does not have the artifacts. I think that the rectangular hole removed them.

For the artifacts you need to look at V1.

This model V2 does not show artifacts on my slicer also.

kees_bijker

Ok I think I musunderstood.

https://cad.onshape.com/documents/1f55960c596fe3f64461824c/w/a2b6fa3953eb686c3a7684f2/e/edb7a766c83c534961d2864d

The document is already public so this should be enough.

The artifacts happen in the stl  generated from version 1. In version 2 I modified the base by extending the front and making a cutout in the rear section. That time the artifacts do not appear.

I hope I am clear with this explanation.

MichaelPascoe said:

Strange, the Onshape model looks fine and the STL export seems to be in good condition for my printer software (CHITU Box). You could try exporting it as a Parasolid, then using a 3rd party site to convert it to STL to see if that gives you different results.

Hi Michael,

Thank you for your time again.

You showed the Version V2, this is modified and does not have the artifacts. I think that the rectangular hole removed them.

For the artifacts you need to look at V1.

This model V2 does not show artifacts on my slicer also.

S1mon said:

I would look at the STL file. I'm betting that the weird artifact curves are along vertices of the tessellation. Without seeing the files I can't tell, but it looks like there's some rounding error because the coordinates are on a sloped surface in the CAD, but rotated flat for the build.

Hi S1mon,

I have turned models very often in the past, with all sorts of different files and never seen this happen before. Also, I made a V2 now, where the base is longer and a rectangular hole is in the part where the artifacts used to be. Now none of these artifacts are visible, even though the model has been turned the same way and the area where the artifacts used to be is still partly exposed. To me this indicates something with the model that generated this behaviour, not me turning the model in the slicer.

Still, I could be wrong, just pointing out my findings so far.