Impossible Passthrough

A twisted star tube with windows down its sides, and twisted cones, balls and teardrops that only get through it by screwing along the twist. Everything prints standing up with no supports.

Customise it in your browser, then download a print-ready STL, or a multi-colour 3MF. No CAD skills needed.

About the Impossible Passthrough

An impossible passthrough: a twisted star tube with windows down its sides, and twisted cones, balls and teardrops that only get through it by screwing along the twist. Everything prints standing up with no supports.

Impossible Passthrough: a customisable 3D print, shown at its starting settings

What you can change

Twists: to the right and to the left.
Pieces: A mix, cones, balls and teardrops.
Pick the tube and piece colours.
Adjust tube length, piece width, star points and twist, and more.
Turn on or off: open windows in the tube.

Size

About 3.6 × 3.6 × 15 cm (width × depth × height), one piece at the starting settings.

What you download

An STL for any slicer, and a 3MF with each colour as its own part, ready for an AMS or a filament change.

Printing it

About 38 g of PLA and about 2 hours 20 minutes to print, one piece at the starting settings (15% infill, 2 walls, 0.2 mm layers, on a Bambu Lab A1). Your slicer gives the exact figures for your printer and settings.

Print the tube and the pieces standing up, with no supports. A piece only goes through by turning with the twist: start it in the star at one end and let it screw its way along.

Ideas for using it

A desk puzzle that starts conversations.
A fidget for people who like to turn things in their hands.
A demonstration of how tolerances work in 3D printing.
A stocking filler for curious minds.

Questions

What size is it?

About 3.6 × 3.6 × 15 cm (width × depth × height), one piece at the starting settings. Every size is a setting, so make it as big or small as you need.

Do I need a multi-colour printer?

No. Print it in one colour, or in colours with a filament change: the Colours line under the 3D view says at which height to change. With an AMS or another multi-colour printer, the 3MF prints it in one go.

Which printers and slicers does it work with?

Any FDM printer. The STL opens in every slicer; the 3MF keeps the colours as separate parts in Bambu Studio, Orca Slicer, PrusaSlicer and Cura. Pick your printer in the designer to check it fits the plate.

Can I sell what I make?

On Pro and Ultimate you can sell the prints you make, for example on Etsy or at craft fairs. On Free and Maker, print it for yourself or give it as a gift. The STL and 3MF files themselves are never for sharing or selling.