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
We made these color cubes to test the new XYZ da Vinci Color 3D printer. The cubes were colored as they were printed, with each extrusion layer “painted” by CMYK ink cartridges inside the printer. Like most really great ideas, the idea of combining FFF with ink jet color is so elegant and obvious that we can’t believe we didn’t think of it earlier, but we’re glad that XYZ did! The cubes are designed to ben impossible to print in color simply by swapping filament at different layer heights; it’s fun to hand these cubes to someone familiar with typical desktop 3D printing and watch them try to figure out how they could have been made.
Although adding color to 3D models can sometimes be a challenge, in this case it was very easy. We simply built the model in Tinkercad and assigned colors there before exporting in OBJ format with an MTL texture file. You can play with the Tinkercad file yourself if you want to remix the cube for your own color tests.
Full disclaimer: XYZprinting provided us with a beta version of their da Vinci Color printer for testing, and that’s why we designed this model. To tell you the truth, before it arrived we really didn’t expect it to work at all, since we had never thought a full-color filament printer would be possible. But we were wrong; the printer really does work, and it really does print in color!