I designed this a couple of weeks ago. The pulleys look good when printed, but at least when using a standard .5mm nozzle, the teeth are not "sharp" enough and the timer belt slips too easy.

When MakerGear published their z pulleys ( http://www.thingiverse.com/thing:1081 ) I asked how they managed to avoid the slipping. Well, they use a .4mm nozzle...

Since MakerGear asked for my design: Here it is.

Again: These pulleys print nicely and also kind of work. The only thing is, that the timer belt doesn't get enough grip on its teeth at .5mm printing.

The gcode file contains the object, processed for .5mm nozzles!

• Print the pulley (you might want to create your own .4 or .3mm gcode file :)
• Insert a M3 nut and a M3 set screw