Intermittent Slicer problem: portion of flat/co-planar object output as floating above build-plate
Hi- Have been using Prusa slicer for 2+ years, and consider it to be superior to all others I've tried. This is the first real issue I've encountered for some time.
I recently downloaded, sliced, and printed a 3D object that failed to print properly. It is a Pangolin, and the back 3/4 portion of the tail failed utterly because the slicer output gcode making this large portion float above the build-plate by several layers. The preview legend showed the floating layers in dark blue, and depending upon layer thickness, they were placed 1 or 2 layers above the build-plate.
https://makerworld.com/en/models/1090887?from=search#profileId-1084361
I reloaded both the .3mf and .stl forms of the object several times, reslicing several times, and the problem persisted. I even exited, then re-started Prusa Slicer several times, and the problem persisted. For reality-check comparison, I loaded the object into Creality/Cura slicer, and it did not exhibit the problem.
I then restarted Prusa Slicer again and resliced the object just now to provide information and screen-shots for this bug-report, but suddenly the slice-output does not demonstrate the problem. ( !!! )
So I can't make the issue occur again...
SW: Prusa Slicer 2.9.0 running windoze 10.
I'll just consider this a "be on the lookout for this issue" report unless/until I can make it happen again.
Thanks-
ron
RE: Intermittent Slicer problem: portion of flat/co-planar object output as floating above build-plate
It is a Pangolin, and the back 3/4 portion of the tail failed utterly because the slicer output gcode making this large portion float above the build-plate by several layers. The preview legend showed the floating layers in dark blue, and depending upon layer thickness, they were placed 1 or 2 layers above the build-plate.
Doesn't sound like a bug. Your model was simply not flat on the build plate. There is a button/feature on the leftside of the platter called "Place on face" to fix these situations.
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RE:
Interestingly, upon recent attempts I was able to reproduce the issue, but the results are still inconsistent.
If I simply slice the object as-is immediately after loading into the slicer, it works fine, laying the entire model correctly and flat, directly on the build-plate.
But, If I load the model and use the "Place on face [F]" function, selecting the bottom face, it present a very different result, where only the first 2/3 of the object is on the build-plate. (images shown below).
Yes, I agree, the model must have some non-planar issue (feels like a floating-point rounding-error), but the inconsistent behavior of the slicer reported above is also curious. I would have expected opposite results.
I'll report this to the person who posted the (very intricate) object.
Thanks.
ron
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I downloaded the stl to take a look.
The bottom of the model is not flat, it cannot be placed flat without one end or the other floating.
I am not going to test-print but here are two possible tactics:
Break to objects *might* allow everything to drop to the build sheet without disrupting the structure.
Or, more likely to work but it may slightly distort the end shape, use the cut tool to shave 0.4mm from the bottom so planing the surface flat.
Cheerio,