This is a design of a lego compartible toothed rack.
It is full parametric because the accuracies of lego are not achievable with a DIY 3D-printer.
With these settings it gets printed on my reprap mendel to a fitting brick.
If you change one value only by 0.1 mm it wouldn't fit anymore.
So try yourselves and have fun.
Read more about this on: www.ifeelbeta.de
Greetings from the lake of constance
Print it and build a lego CNC robot...