QU-BD MBE Spring Tension Arm

###Tension Arm w/ 608 Bearing

This is a tension arm for the _QU-BD MBE Extruder_. It works with a _608 bearing_ that is commonly used for skates, roller blades and other similar things. The bearing can be inexpensive, since this is a low speed operation you don't need high ABEC ratings.

This will work with the standard raptor gear in i'ts normal position using the groove. The clearance is tight but it works. The head of the feed tube screw hits the bearing with no filament but once the filament it is in it clears fine and runs smoothly. I started getting my best prints once I put this in place.

This arm is stronger than some of the others that I have seen, printed and tried to use. Especially if you are going to print this with PLA. I found other designs to warp easily from the heat of the extruder and bed rising up.

This design is inspired by the spring tensioner from Barton Dring.
http://www.thingiverse.com/thing:38281