This is a clever illusion desk toy I designed. By sliding the black slider in the center up and down, a peculiar ribbon seems to move up and down, with its ends disappearing into the void.

The build requires two standard skateboard bearings, while everything else can be 3D printed. No glue is needed for assembly.

Notes
The design allows enough tolerance for the parts to fit together smoothly, but you may need to use XY compensation on the nut to slightly loosen the fit. Otherwise, you might have to work the nut back and forth to get it to fit properly.

For added strength, I recommend printing the base with four or five vertical walls to ensure the poles are sturdy. While fewer walls might work, there’s a risk of snapping parts when snapping them into place.

You can use larger layer heights for most parts except for the screw, nut, and end cap—those require finer layers for proper functionality.

For the best effect, I suggest printing the base in black and using a contrasting color for the screw. A black base will help conceal where the screw "disappears" into it. However, an all-black design will still look great.

Post-Printing Instructions
You’ll need two skateboard bearings: one for the top and one for the base. These should press into place without trouble.

Follow these steps to assemble:

1. Snap the bearings into the top and base.
2. Insert the short dowel (with a rim) into the base bearing. Ensure the longer end of the dowel goes into the bearing.
3. Screw the nut onto the screw. If it’s tight, work it back and forth gently. Be cautious not to break the screw; if needed, reprint the nut with -0.1 mm XY compensation for a looser fit.
4. Screw the end cap onto the screw’s end. Use XY compensation if it won’t thread properly.
5. Attach the screw assembly to the coupling dowel in the base bearing.
6. Align the top carefully so the sockets match the poles and the bearing fits into the end cap. Snap it together step by step, applying slight pressure until everything is securely in place.