Slicing bodies modeled as separate but contacting...
Hi all -- new PrusaSlicer user here driving a 5-tool XL. I make professional quality electric violins using HTPLA which is then annealed after printing. However, for the violin bodies, this requires printing an external rib structure that holds the body in shape during annealing and is then removed.
How this rib structure attaches, or doesn't attach, to the main body is very important. It must contact slightly, but not leave a significant blemish after removal. I have this dialed on my Makergear M2 (slicing with Simplify3D) and I am unable to get it set up right in PrusaSlicer.
I want to print with a single material, but I want the ribs to NOT join with the main body. The perimeters should not cross. This is done correctly if I make the ribs a second material. Here is the part:
Now here is what that looks like sliced, zooming in a bit:
It's hard to tell, but if you look carefully, you can see that the rib and body are printed separately -- the perimeters are NEVER combined.
Now if we make the ribs and the body the same extruder, this changes. I have circled a few areas where you can see that the perimeters are combined between the rib and the body.
I have done my best to find the right setting to toggle or adjust so that they don't do this, but I haven't been able to figure it out.
Thank you in advance for any tips, tricks, and suggestions!
-David
Best Answer by Neophyl:
Normally you would change the slice gap closing radius to stop Prusa slicer merging close by geometry. Unfortunately that will never work in this case as its not just close by geometry, its actual interpenetrating geometry. I exported your model as an stl to examine a tool that allows cross sectioning (3d-Tool) and you can clearly see where your ribs don't just touch, they go inside the main body. PS will ALWAYS slice like its doing when its the same body and extruder. See this image of just one place where it intersects.
When you have different extruders its trimming the overlap away where they intersect. You need to fix your model to make the ribs have a tiny gap all over with NO overlap at all, and then you can set the slice gap closing radius to something like 0.000001 to stop it merging anything.
RE: Slicing bodies modeled as separate but contacting...
Here is a zipped 3mf of the project:
RE:
Wow, the violin looks awesome! I’d love to see a finished product. Do you sell them online?
Maybe as a workaround, you could try using identical filament spools on two different extruders? It would involve tool changes so it wouldn’t be as fast but it could work? I’d be interested to see if you find any solution.
MK4S/MMU3
RE: Slicing bodies modeled as separate but contacting...
Normally you would change the slice gap closing radius to stop Prusa slicer merging close by geometry. Unfortunately that will never work in this case as its not just close by geometry, its actual interpenetrating geometry. I exported your model as an stl to examine a tool that allows cross sectioning (3d-Tool) and you can clearly see where your ribs don't just touch, they go inside the main body. PS will ALWAYS slice like its doing when its the same body and extruder. See this image of just one place where it intersects.
When you have different extruders its trimming the overlap away where they intersect. You need to fix your model to make the ribs have a tiny gap all over with NO overlap at all, and then you can set the slice gap closing radius to something like 0.000001 to stop it merging anything.
RE: Slicing bodies modeled as separate but contacting...
Thank you!!! This also explains why the setting that addresses this issue in Simplify3D is related to mesh healing -- it's the overlapping meshes that cause the issue!
I moved the ribs away 0.01mm, but then still had the issue.
So I adjusted the mesh resolution (to high in Fusion 360) so that the surface deviation is 0.006. There is still possibly overlap if two faces are off by this amount, but it is much less likely.
Following these steps, it is actually not necessary to adjust the slice gap closing radius, which I left at 0.049. My guess is that because the bodies are separate the slicer is not viewing them as a crack that should be closed, because they definitely are closer than 0.049.
Now I have nice separate bodies with no perimeters crossing -- exactly what I want! Thank you.
RE: Slicing bodies modeled as separate but contacting...
Thank you! And yes, using the same material in a different tool would totally work.
Yes, I sell them online and through the brick and mortar Electric Violin Shop in Durham, NC. You can see my work on Instagram as well. Thanks for your interest! They are super fun to make and I never imagined I could achieve this kind of violin quality. Just goes to show what's possible when you simply make something over and over and over and over and over and try stuff...
The project is open source as well -- you can find the basic 4-string violin files on Printables and I publish all of my different variations on Patreon.