It is a print in place model, where you have to pause your printer to put the magnets and the balls in.
Additional hardware:
3 x 4mm steel balls (can be found in 608 bearings)
3 x 6x3mm magnets
Printing:
Load the top and bottom part into the slicer and confirm that it is one part. Depending on your printer you can choose between the loose or the tight fit. If your printer is not accurate eneough or your extrusion settings are too high, it can happen that the parts fuse together.
Slice the parts (0.2mm layerheight) and add in a PAUSE at Layer 19 (3.8mm) and a PAUSE at Layer 44 (8.8mm)
on the first PAUSE insert the magnets. Make sure that they are aligned all with the same polarity.
On the second PAUSE put in the 4mm steel balls. because of the magnets the should be held in place
After the print has finnished carefully seperate the two parts with a sharp utility