Replacing Extruder G-Code Commands with Pump On/Off

Hi,

I am building a 3D printer that uses a pressurized pump instead of a stepper extruder to print material. Consequently I have no need of the fourth-axis A G-Code commands as there is no filament nor stepper-based extruder. Instead I need a switch-like on/off command when the printhead is either printing or moving to a new location. Basically I just need to turn the pump on and off. I would like to use the M7 and M8 commands (traditionally for the coolant pump) within the G-code to control this, but I'm not sure where or how to begin modifying Slic3r (or any other useful slicing program) to output M7/M8 instead of the stepper commands on the A axis. Basically this is what the code should look like:

M7 (turns pump on)
(X and Y movements for perimeter and infill until 1st layer is finished)
M8 (turns pump off)
(Printhead moves to new location for the start for 2nd layer)
M7 (pump on)
(2nd layer)

etc.

Any ideas?

Hi,

I am Bala, doing my Master's in Industrial Engineering (Pennstate). I am exactly working on the same project and trying to convert an existing cnc mill into a 3d printer.

Interestingly I have started off with the same concept.

Have you completed this project?

Regards,
Bala

RepRapFirmware supports command M571 for exactly this purpose, see [reprap.org]. It outputs a defined PWM signal on the fan output whenever the standard 3D printer gcode indicates that extrusion should be taking place, and turns it off during non-extruding moves. It's been used to control paste extruders and laser engravers.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].