I am continuing to develop a moderate size, four extruder delta machine based on the E3D Kraken. I have worked for years at home with a six-axis Stewart platform router/mill, so I'm familiar with the difficulties of calibrating it, further exacerbated by the constraints of multi-head 3D printing.
To keep the non-printing nozzles out of the way, I've added two degrees-of-freedom to the three degrees-of-freedom delta mechanism by incorporating a rocker mechanism in the head which will present one nozzle to the work at a time, while backing the other three nozzles some distance from the work. In particular, they are backed away enough to accommodate the tilt error as the head moves through the build plane.
I'm still working on this, having taken a side-trip into making (and not quite succeeding) a good bed position sensor. Comments are welcome -- as are constructive suggestions.
I've reserved and modified some G and M codes, all I believe plainly marked. I am building this based on the DC42 variant of the RepRapPro firmware. My initials are cmm, so I have marked some items as being present in the DC42-cmm version.
When complete, or when someone cares, I will commit the code to git. When the time comes, I may need some help getting it right, and not destroying the repository.
-- Carl Mikkelsen -- alias cmm -- alias Foxkid (it comes, according to my Danish grandmother, from a bad, impromptu translation of Mikkelsen)