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prusa3d
Bad/messy/inconsistent slicing in PS with "merged" multi-color entity
Description of the bug
update: See https://github.com/prusa3d/PrusaSlicer/issues/11607#issuecomment-1797037153
I don't really know how to describe this bug other than it creates an incredibly messy layer, like the whole thing is 100% infill instead of recognizing perimeters. The Z position of the messy layer changes (along with the angle of the "mess") if you move the part around on the build plate, and seems to go away completely if you rotate the part 180°. The bad layer in the provided project file is 15 (4.4mm).
Project file & How to reproduce
updated per https://github.com/prusa3d/PrusaSlicer/issues/11607#issuecomment-1797037153
- Download this file with
Mergedobject, see details in the description above about a corrupt layer15. - Change the model so both parts print with a single color/extruder, and re-slice. Notice that the layers are now fine.
- Revert back to 2 colors and split
Mergedback into separate objects and re-slice, to see that everything slices correctly using either 1 or 2 colors. - Merge the two objects back together and re-slice in 2 colors to see that the problem layer has returned (though probably at a different Z height)
This appears to be a problem with how "merge" is handled. However, even if this was an issue with a corrupt non-manifold model, PrusaSlicer normally detects these and either auto-repairs or at least notifies that there is a problem with the model. No such notification shows up.
Checklist of files included above
- [X] Project file
- [X] Screenshot
Version of PrusaSlicer
- 2.7.0-alpha1
- 2.6.1 (added after updated description above)
Operating system
MacOS
Printer model
Prusa XL 2-tool
There are some errors in the model. It is sliced correctly after repairing the model. I am attaching repaired model.
fixed_messy_slice_layer_15.zip
Out of curiousity what was wrong with it and how did you fix it? I didn't get any warnings when importing the original model from Onshape, nor when opening this one. In the interest of checking whether this is a problem with Onshape's 3mf export or a bug with the "merge" functionality in PrusaSlicer, I've attached the raw export from OnShape:
I generated the "messy" one by importing this 2-part model (requires pressing undo because PS auto-arranges the 2 parts into different places … thankfully undo puts them back), and then selecting both parts from the list and then merge from the right-click menu.
FWIW, upstream info about this model (I'm the author) is at https://www.printables.com/model/620175-honeycomb-storage-wall-onshape-customizer (though if you want the specific part in question, it's the left+middle panel from this break-out model with the measurements for my wall)
I just repaired it using built-in windows repair service (it is based on Netfabb).
I just repaired it using built-in windows repair service (it is based on Netfabb).
Interesting. Does it flag the same kind of errors in the hsw_350x310_fat-left.3mf.zip file I attached above? If so, then this is something with Onshape. If not, I'll edit the description here and re-classify it as a bug in PrusaSlicer's "merge" function.
Even stranger, I created a new PS project with the new 3mf export I did today, and it slices fine. I'll close this and just keep an eye on things in case it's some issue with PS, but I know Onshape has had issues in the past with 3mf export compatibility so it seems this is more likely something on their end.
Reopening after a bit more testing. This definitely seems to be a problem with how PS handles merged multi-color objects (but prints them fine when they're split). I've also confirmed that it happens in 2.6.1 (Mac), not just the 2.7 alpha.
Replication steps:
If you take the original file I uploaded and split the Merged part back up into separate objects, everything slices fine. It also seems to slice properly if you set both parts to print with the same extruder. However, if you re-merge the parts, the bad layers return (though at different layer heights).
Still happening in the latest 2.7.4. Here's a new file that shows "no errors detected" and yet still exhibits the problems. You can see the bad layer at/around 4.0mm. However, the errors go away if you rotate the part 180° and re-slice. As with earlier issues the problem also goes away if you merge the two colors into a single part.
Unlike earlier examples, this model was loaded into PrusaSlicer from a .step instead of 3mf/stl. Included here for further examination (needs to be rotated ±30° after import to fit on the print bed).
bad-slicing-layer-bug.step.zip