Hi all
So technically this is not a reprap question since I'm not printing anything, but it's close enough I think... I built a 3D positioning system for an imaging device using RAMPS1.4 drivers and Marlin, and I wanted to use the extruder driver to control a motor for device rotation. So essentially I want the extruder channel (Marlin E0) to be a fourth, fully independent position controller, with endstops and everything (I won't be able to get full 360deg rotation due to setup contstraints).

I know the extruder motor is already independent, but if I use say slic3r to create g-code for a path I want the device to trace, the motor will rotate continually as if it's extruding. So maybe half of the answer is in adjusting slic3r settings, setting the extrusion rate to 0? But then I might want periodic rotations, so I need to include those instructions...

I'm pretty novice with Arduino and coding in general, so does anyone have advice (of the dumbed down and step-by-step kind) for how to achieve all this in Marlin? Maybe you heard of someone else doing something similar and can send me a link? The hardware end is already taken care of, using pins 32 and 47 for the rotation endstops.

many thanks

I think you have to simply try. Marlin makes the assumption to work on a printer in some places, so you have to find how well it works. One distinction between the E and the other axes is, E isn't taken into account for feedrate calculations. Except if it's an E-only movement.

Teacup firmware is currently in progress for supporting an arbitrary number of axes. Will require additional hacking in its current state, though.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Hm, yeah much hacking will be needed either way, just thought maybe someone knows someone who already did much of the hacking already...

I'll check out teacup, thanks for the tip