I tend to agree with Cornelius, but it would be interesting to find out for certain. One of the weaker aspects of an FDM part is the bonding between layers. If you were to print the pulley flat it would be prone to separation with a vee belt, and I think heat from the friction of a running belt would cause trouble as well. If I were going to do it, I would use ABS at a minimum, but I think a nylon-based filament and a toothed (timing belt) system would be your best option.?
