Changes I've made while building my Cerberus deltabot 3D printer
Many thanks to Steve Graber for the Cerberus design, and to Printrbot for making my first 3D printer and for being such a cool company.
12/16/14 Magnetic Joints: I had this idea early on while building my Cerberus, and I've followed it down a bit of a rabbit hole. I'm really happy with the joints. They have no lash whatsoever, are dry, and the fabrication of the joints themselves is highly repeatable.
The idea of a virtual socket design formed by the 3 points of contact was something I couldn't let go of. The downside is the strength of the joint to resist forces imparted by the Bowden tubes and wire harness to the end effector. It took me a few revisions to get to this configuration. But with the 1/4" X 1/4" magnets, the joints are plenty strong for my setup and some pretty impressive printing speed. In order to reduce the forces involved, I designed a flying extruder set up, which is still a work-in-progress. I am having great success running dual extruders, one 3 mm and the other 1.75 mm.
One benefit of the socket design is that in a crash of the end effector to the build surface, the joints just let go instead of damaging anything. The Teflon bearing surfaces are durable, but might prove to be consumable over the long term. But hey, it's just tape.