bruce356 wrote:One question about the X axis end stop, how is this supposed to function in operation and in homing.
Is the end stop meant to trigger at the same time as the left extruder comes in contact with the left parking or just before.
Being a mechanical switch there is also a limit to the distance of further travel after triggering.
Yes, there's not any way I can think of to get around the fact that the switch must trigger when the left extruder is in the fully parked position. That means that the switch triggers at X < 0 and so the home position is not at X = 0 like it usually is on the M2. Fortunately the firmware is able to handle that; it just needs to know the offset between the trigger point and X = 0. And that's all a relative measurement, anyway. Getting it exactly on means that X = 0 is defined as exactly at the edge of the bed plate, but unless you're printing something that goes to the exact edge of the plate, that's not going to matter much. But with the dual independent extruder setup, some of the tolerances do become more important, because there are a few places where a couple of millimeters is the difference between latching onto a magnet and crashing into something. But the magnets are pretty strong and they do attract from a couple of millimeters away, so working out all the head positions to a few millimeters tolerance is pretty easy for a finely-tuned piece of machinery like the M2.
It's somewhat tedious to write the startup script, keeping in mind where all the coordinates are and remembering that each extruder has its own coordinate system. Obviously the left extruder's coordinate system is defined by its parking position, which is where the X stop switch triggers. But unlike the standard dual extruder, you can't figure out what the coordinate system of the right extruder by measuring the distance between it and the left extruder to get a rough estimate. To get a rough estimate, you have to attach the left extruder, put it somewhere in the middle of its travel, and mark the position; then attach the right extruder, and figure out how far you have to move it to get the nozzle to the same point. However, for the design files I posted, the offset between the extruders is approximately 20.6mm, so that can be used as a ballpark estimate; and in any case, you will end up running a calibration test to refine that value. I guess the main difference is that the MakerGear dual extruder has the offset distance defined by the holes drilled into the mount plate, which is precision-machined, so if you put the default value into firmware, there's almost no point in running a calibration test. The independent dual extruder setup has multiple contributors to the offset value, so the offset calibration is definitely needed, and can easily be off by a millimeter in both X and Y. Once dialed in, though, it should be good as long as you don't unscrew the mount plate from the rail carriages.