Full Color Un-Manufacturable Part

This print-in-place impossible screw has two interlocking pieces that twist freely but cannot come apart! A great example of an object that can be made with layer-by-layer 3D printing, but not with traditional manufacturing methods.

The model is a remix of TheKre8Group’s elegantly mind-bending Un-Manufacturable Part. We increased the clearance between the two parts, elongated the interior part with an extra twist, and added color to the inside twist for printing on full color 3D printers. We printed ours on the new XYZ da Vinci Color 3D printer, which you can read more about at our previous Hacktastic post about Full Color Desktop 3D Printing. The downloadable files also include models to use with dual-extrusion 3D printers and regular single-extrusion printers.

You can download the model from Thingiverse at this link: https://www.thingiverse.com/thing:2623645

Modifying models to print in color has turned out be difficult with a capital D. For the full color model we used Meshmixer to “paint” the colors onto each vertex with the Sculpt tool. This sounds simple, except that the model started out with an overly sparse mesh on the top flat faces, which made the colors blend poorly and also act strangely when printed. After a lot of trial and error, including attempts at re-meshing with MakePrintable and MeshLab, we finally discovered that we could use “Make Solid” in Meshmixer to get a very nice overall homogenous new mesh around the object.

Here’s a quick overview of the workflow we used to remix this model:

  • Thingiverse:  Start with the Un-Manufacturable Part model from TheKre8Group
  • Meshmixer:  Separate the two pieces into different files
  • Blender:  Use displacement modifier to increase clearance on both pieces
  • Tinkercad:  Cut out the center of the interior piece (so we can color just the top)
  • Meshmixer:  Remesh using Make Solid, paint with Sculpt tool
  • XYZ:  Slice so that interior piece prints with 50% infill, exterior with 20%
  • da Vinci Color printer:  Print in one piece, with color added to each layer by the printer

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