For the injection molding to work, I need to have molds. Yesterday I started with my first ever try at milling aluminum in my homebuilt CNC-machine. It started off quite okay, but then suddenly the z-axis dropped and buried its nose deep in the aluminium stock. The code and everything seems okay, so I am wondering if it was the stepper motor going crazy thanks to excessive heat. 

Today I have put a heatsink and a fan on the motor, hopefully that will do the trick. Otherwise my next experiment will be to make molds in a somewhat softer material like polyurethane or polyester, because aluminium is both tricky, hard and expensive.