Magic Portal Desk Toy

Demo (Apologies for the sound. It's not that loud in person.)

This is a neat little illusion desk toy I designed. As you slide the black slider in the middle up and down, the strange ribbon appears to slide up and down, its ends vanishing into the void.

This print requires two standard skateboard bearings, but everything else is printed, and shouldn't require gluing.

Update: I designed this fast print-in-place bearing which works great for this project.  

Printing

I recommend printing this at 0.12mm. You can certainly get away with larger layers everywhere but the screw, nut, and endcap. I wouldn't cheat on those.

There should be enough slop in the design for everything to fit together, but you might want to add XY compensation on the nut to loosen the hole a little bit. Otherwise, you may have to work it back and forth a bit to loosen it up.

I recommend going for four or five vertical walls on the base to make sure the poles are strong. You can definitely get away with less, but it snaps together pretty tight, so you might snap something when working it in.

I recommend black for the base and a contrasting color for the screw (using a filament swap). The black will help to hide where the screw "disappears" into the base. The effect should still look nice in all black though.

Assembly

You'll need two skateboard bearings; one for the top, one for the base. They should press in easily.

Other than the bearings, the CAD file has everything arranged in its final position. Most of the assembly isn't particularly order dependent, but these steps should work:

1. Snap the bearings into the top and the base
2. Push the inner bearing insert (the short dowel with a rim on it) into the base bearing. The long side goes into the bearing.
3. Screw the nut onto the screw. You may need to work it back and forth a bit to get it on, depending on print defects. Be careful on this step not to break the screw (reprint the nut with -0.1 mm XY compensation if it's not working out)
4. Screw the end cap onto the end of the screw. (Again, XY compensation if it won't go on)
5. Push the screw assembly down onto the coupling dowel in the base bearing
6. Carefully line up the top so that the sockets line up with the poles, and the bearing lines up with the end cap. This may take a little oomph. Take it a little bit at a time and get it snapped down tight.

Update: If you have a small printer and want to scale this down, you can use this print-in-place bearing and scale it proportionally. I’ve tried them on the full size version, and they work great. Remember to do some test prints on the pieces that fit together though, and check if you need to add negative XY compensation.