Designed this fold roller (I know it looks like a pizza cutter ^^) to make clean folds on cardboards. I use a section of brass cylinder (external diameter : 5mm, internal diameter : ~4mm) to act as a bearing and prevent the wheel to wear out too fast on the screw. Designed for M4 nuts and screws (it requires 3 of each), I used a nilock nut on the wheel one to be able to lock it without tightening it too much. It allows the wheel to roll freely.

When using it in the same direction as the cardboard 'grooves' don't press it too hard or it could cut into the cardboard. After a few test I realised you don't have to press it really hard in any direction to make a proper fold, even on thick cardboard.

Printing: I printed it with PETG for longevity but I guess it should work fine with PLA Printed with a 0.3mm layer height without supports.

No post processing needed except fastening the 3 parts together with nuts and screws.

Let me know how it works for you :)