Magnetic zipper tear-strip fidget keychain

Have you ever felt the satisfaction of pulling a cardboard zipper tear strip (ZTS) when opening a box or package, only to be disappointed when you reach the end?  Now with this tear-strip fidget you can relive that satisfied feeling over and over again! This toy was inspired by the Bandai Mugen Peri Peri toy from 2008 - I had one but lost it years ago :( so I was inspired to recreate it for the Built To Flex contest. 

You will need 10x D5mm x 3mm disc magnets, and a split ring keychain or similar to complete this part. You can find the Maker's Supply parts below.

The model uses less than 13g of filament, assembles quickly (less than a minute!) and can't come apart once you put a split ring or keyring through the tab piece.

Printing notes

The default layer height is 0.2mm, however I have added a Height range Modifier to decrease the layer height to 0.12mm between 4.2mm and 4.68mm. This ensures there are 3 layers of filament retaining the magnets in both the body and strap parts, while keeping the distance between the magnets as small as possible. I found if it was only 2 layers there would be some holes in the layers because the first layer “bridges” over the magnets. 

The first 0.12mm layer is to add clearance to the holes for the magnets. A pause has been added after this layer (layer 22 - i.e. the pause is before layer 23) for inserting the magnets. MAKE SURE YOU GET THE POLARITY CORRECT when inserting the magnets. You want to put all north poles facing up in one part, and all south poles facing up in the other to ensure they are attracted to each other.

Also, general TPU advice - dry your filament to avoid stringing! 

The part in my photos was printed using Polymaker Polyflex TPU 95A. I have found it sticks too well to the Smooth PEI and Textured plates, but using 3M blue painters tape provides the perfect amount of adhesion, and leaves a nice, slightly textured, matte finish. I alwas run bed levelling if I do this.

Assembly instructions

Watch this super-quick video, otherwise text instructions are below.

1. Take the strip and push the “legs” (large end) into the hole in the body from the top. The fit is quite tight, so use some force if necessary.
2. From the underside, poke the hole end of the tab between the legs of the strip until it is poking through the hole of the body as well.
3. Push the rear of the tab down. Again, use some force if required. It should be flush with the body.
4. Put a split ring or other keyring/loop of cord, etc through the hole in the tab and bend it closed.
5. Enjoy the satisfaction of infinite tearing!