How do you import a multi-part object into PrusaSlicer without losing the position of the parts? For example, I want to print a two-material interlocking structure like this:

Two-part object with interlocking dovetails

I've tried exporting this from my CAD software (OnShape) as a mesh (STL or OBJ) but when I import it into PrusaSlicer (v2.7.0) the result is either a single object with no internal walls:

Screenshot of PrusaSlicer 2.7.0 showing a single featureless cube model

or (3MF) two objects placed on the build plate individually, so they no longer interlock:

Screenshot of PrusaSlicer 2.7.0 where the two parts have been placed onto the build plate individually

If I use a STEP file it at least preserves the position of the parts within a single object, and there are some internal walls, but no internal top and bottom layers which I want for structural reasons (in this case the dovetail will simply crush in the XY plane if the part is tensioned in the Z axis):

Screenshot of PrusaSlicer showing a sliced preview of a single object with two parts

What's a good way to import multiple parts and have them "print in place", like they were in the original design?


2 Answers 2


I've found a way to do this, which I'll document here in case it helps someone else in the future.

  • Export your parts as a single STEP file
  • Import that STEP file into PrusaSlicer
  • Set Print Settings > Multiple Extruders > Advanced > Interface shells
    • (You need to be in Expert mode to see this option)

Screenshot of PrusaSlicer 2.7.0 showing the Interface Shells option

The STEP file adds the internal walls, and this interface shells option adds the internal top and bottom layers I was missing:

Screenshot of PrusaSlicer 2.7.0 showing sliced preview of a two-part print where interior layers / floors can be seen


Despite how featureless the STL mesh looks when imported, all the data is there and you can split it to parts using the right click menu. I feel silly for now having spotted this before 🤦.

PrusaSlicer 2.7.1 showing a featureless cube with a right click menu where "Split > To Parts" has been selected

The result is exactly as I had hoped:

PrusaSlicer 2.7.1 sliced view showing a two colour print and an object with two parts in the object list

My take away is that PrusaSlicer does not always prompt you to split your important mesh into multiple parts; so its always worth attempting to split to parts using the menu after import.


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