Thanks for the feedback. Yeah, I didnt' think about that issue.. hmm.. Well that's the type of feedback I needed! I guess a flex tube will have the same problem no matter where the stepper is mounted. It could be mitigated slightly by centering the stepper vertically above the X/Y envelope but that would only spread the errors out. Hmm... Bummer
Edit:
Well... on second thought.. if you keep the axis of the tube rotation parallel to the Z plane then the X/Y movements shouldn't cause additional rotations. It also eliminates the need for the right-angle gear box... however, I'm not sure that a flex tube can bend that sharply.... I'll have to play around with the idea some more.
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thedudevt 0
Assuming you mounted the motor in the back right corner (where the current motor is) with the shaft up, then transiting the head from X0 Y0 to X200 Y0 would rotate the flex shaft inside the flex shaft housing ~10-15 degrees. So, the normal XY motion of the gantry would have a extrusion/retraction effect on the filament which, I think, might be a lot of work to back out in software. You might be able to do it with an inverse kinematic model, but that would add a lot to the slicing overhead.
I think there are mechanical ways to cancel it out, differentials come to mind. It would be interesting to design a printable version- lots of gears and aluminum torque tubes. The torque tube designs of some RC helicopter tail shafts might be a good place to get inspiration.
Kyle
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