innkeeper wrote:the challenge for me when running printers in general with 2 heads is the second head going across the surface of the freshly printed surface of the first one, leaving the color behind due too oozing or the head actually torching the print.
Yeah, well, welcome to the dual-extruder club. This has been discussed before, and the general consensus is that yes, oozing is an awful problem, and the wipe towers and ooze shields can only do so much. I think that ultimately the dual extruder needs to be redesigned to allow the inactive extruder to be "parked", resting on a wipe plate. Some dual extruder machines have two extruder assemblies running independently on the X axis. That would be hard to do with the existing M2 frame without severely reducing the X dimension of the build area. Some time ago, I was trying to design a rocking extruder assembly that would allow the inactive extruder to swing up out of the way (and onto a plate) while the other swings down into position. I almost got it to a working design, but it must be rock-solid, and I don't have a machine shop to make the pieces out of steel or aluminum. That concept has been done before (not with the M2, that I know of), sometimes using additional motors and controller boards.
Otherwise, the usual solutions are (1) know which of your filaments ooze the least, and stick with those; (2) use ooze shields and wipe towers, and (3) redesign parts to keep them from having the kind of geometry that undermines the whole ooze shield thing, which happens if one extruder is printing while the other is positioned directly over the border and dripping on it. The ooze shield works in most cases because the inactive extruder spends most of its time either outside of the ooze shield, or over the interior of the object, where it usually doesn't matter if stuff is dripping.
A third consideration, depending on your choice of slicer, is problems from software---Simplify3D's most recent version had a lot of useful updates for dual printing but screwed up the basic hand-off between the extruders, leaving the 2nd extruder inactive but
not retracted at the beginning of a print. I worked out a solution to that, which is in another post somewhere on the forum.