Bondtech BMG Volcano dual drive toolhead for Taz 5 etc.

This is a remix of jaln's BMG toolhead for Taz 3,4,5,6. It was reworked for printability and material/weight savings, and the vertical distance was lengthened to accommodate the extra height of the E3D Volcano hotend. The goal is to have maximum throughput on a Taz - max melt rate and max drive speed without stripping, in order to experiment with very low print completion times.