Square Mag Keychain

I use a Square mag reader for credit card sales when I sell items at local markets. I wanted a case that I can attach to a keychain to protect it and have easy access to it. I started out by measuring the dimensions the device with a caliper and designing case around that. The first one I designed and 3D printed had problems, but was also my very first 3D design. It took a few iterations to get the dimensions just right. Now it is easy to snap in and it stays in and I'm happy with the results. I had no previous experience with 3D modeling, but I was able to create what I imagined quickly with Tinkercad. Your welcome to copy the Tinkercad design or just print the STL file.

In Tinkercad, I started with a box and then started to remove shapes to fit the Square reader. The main part of the Square device is 27mm x 27mm x 8mm and extends to 40mm to the Lighting plug. You could duplicate this yourself with the following instructions. Create a 34.6mm x 50x12.8 box. After put a 6mm diameter cylinder (hole) 15mm tall center in the corner for the key ring. Then a 20 mm cylinder (hole) 15mm tall, align to center, this is the finger hole. After that make a box (hole) that is 27.2x27.5x12 centered with align tool and 2.5mm from back edge and 2 mm above the Workplane. This is to fit the body of the Square reader. Next it needs a space to insert the Lighting plug. Make a hole to subtract 9.9mm x 15mm x 12mm box, 5mm from front edge and 2mm above the Workplane Then another 4mm x 3 mm box (hole) that is 2mm from front edge and also 2mm above the Workplane. Select all the shapes and group together. Create 27.3x1x1.9 roof shape, align this new shape to back side of the main box hole. Duplicate this shape, rotate the twin 180 degrees. and group with twin. Place this new shape 9mm above the Workplane. Then group all shapes together. You can see how it works or customize your own copy at Tinkercad

I just got my first 3D printer last month, it's a Ender 3 V2. I used the following Cura settings: 3 wall line count, no build plate or supports and 20% Zig Zag Infill. It's an easy print, I've got consistent prints on multiple units. It should print well on just about every 3D printer.