Replacement for the original wooden extruder gear. Works with the Ultimaker Original and the Ultimaker Original +.
I was not very happy with the existing designs as their teeth profiles didn't match the motor gear or they were non-symmetrical or it wasn't possible to fasten the stepper screws with the wheel mounted...

So I decided to start from scratch and build a new one.

Features:

• Very good fitting to the stepper pinion. It has involute teeth, matching the distance of the axes and the numbers of teeth.

• You can use this wheel with only one washer between the bearing and the gear to get maximum tooth contact area. (However opening the extruder clamp can be a bit tricky if you assembled it to close...)

• Fastening of stepper screws possible

• The backlash is very small if the stepper motor is aligned properly (might increase retraction quality)

• M8 Nut should fit in nicely.

• Design makes it a very rigid structure (even @20% infill)

• Prints without support material

UPDATES:
10.05.2013: Now with thicker teeth. Can be printed without support material and no need for second variant. Thanks to Noctis for the hint!
Note: photos are outdated (they show version 1)
29.04.2013: Added second stl file for use with two washers. This one is easily printable without support material and has no clearance grooves.