I had some trouble with the original design of the drive gear. First of all the screw the square nut did not fit. The plastic around broke away. May be it was a problem with my print. The second problem was, that the original part was not long enough for me, because I changeged the contruction somehow. I will publish the complete design on my blog sturm.selfhost.eu. The thing is based on the original design (filasstruder.com) with the addition of the cone with screw fixing.Print in ABS 80% fill, 0,35mm layer height. Print very slow !!