A simple magnet puncher with polarity.

BOM: 

4x2mm round magnets - 2pcs

super glue

INSTRUCTIONS:

There are 2 versions. A multi-colour version and a single-colour version. You will require an AMS for the multi-colour version. I have set it to print in Bambu Lab petg-HF. You can also print it in PLA, but will need to change the X-Y hole compensation from 0 to 0.05. This is because PLA might shrink a little which will make inserting the magnets difficult. 

Print the parts out following the setting on the build plate and press-fit the magnet with the corresponding polarity into the puncher. If you are printing the puncher in PLA,  use a bit of super glue to keep the magnet in place. 

HOW TO Determine NORTH and SOUTH

If you do not have a labelled magnet or a compass to check the polarity of the magnet, there is a simple way. Hang the magnets on a thin string in mid-air. Once it stabilizes, the magnets will align themselves to the poles. North (-) and South (+). You can check the north and south directions with the compass app on your mobile phone. Do this test in the open where there is no metal, magnets or heavy wiring close to it.