Dual Extruder concept featured in this Reddit post. Mk1 is the version seen in the video. Mk2 is an untested concept with an improved Z axis and normal IDEX kinematics. The frame is based on MakerBeam XL Extrusions. Note: the concept still has flaws to work out. Getting the two tools to be at the same height is only possible by shimming and will take time. Slicer support for collaboratively working on a single part also isn't really there yet. Feel free to use as is, or use this design as a base for your project!
