MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
I've made some modifications to this Karl's excellent design in order to support a steel recoil spring from a chainsaw (<$10 on Amazon).
Run time is approx 20 minutes. A remix will follow shortly if there is interest.
Sorry about the long winding but I wanted to show the number of coils.