This rethink of the original model incorporates sensor support for pre and post extruder, I made it to try and take advantage of the new auto-calibration features in Happy Hare.

Uses 5mm ball bearings, some PFTE tubing, microswitches 

The sensor base uses a cut PFTE tube, 5-6mm section removed (in a sort of “U” shape) to allow the ball bearing to interact with the filament as it comes through 

This has been tested to work with my set up now however it did take multiple iterations of where to put the sensors/how to cut the tube. 

EDIT I have recently found XOL metrix filament cutter and toolhead sensor adaptation to the XOL extruder block. I find it to be a better design than this. 

https://github.com/SouthAsh1/Xol-metrix