How to mount a stepper controlled pen in place of extruder for testing?

3D Printing
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How to mount a stepper controlled pen in place of extruder for testing?

I want to test the X Y Axis of the 3D Printer I am building before I invest in an extruder and a hot end/filament. My plan is to put a stepper controlled pen in place of the extruder. The stepper will raise/lower the pen a few MM – enough that I can see that it has left a mark (as if extruding) or not (as if extruder is off). Then I can calibrate the table, experiment with GCODE and make pretty drawings.

So basically, I want the hardware to behave like a pen plotter but I want the software to think it’s a full 3D printer.

I have an idea of how to take care of the mechanical part - attaching a pen to a stepper so that the pen travels up/down. I can then plug that stepper into the E Extruder channel on the 3D Controller Where I am stuck is how to set the 3D Controller so that when it gets an EXTRUDE ON command it simply executes a pen down by moving a few steps. (It must stop after a few steps) Then, when it gets an Extrude OFF command, I want it to reverse a few steps. That’s it no continuous rotation.

I imagine there must be a way to trick Marlin firmware or Repetier host to accomplish this but I’m not sure know where to start.

Does anyone have feedback on how I should go about this?

Are you aware of anyone that has done this? I’m sure someone has done this already. I’m looking for links to software and/or the hardware ideas.

Thanks.

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Pen plotting 3D printers are mostly using servos afaik. You’d probably have to modify the firmware and make an “extruder ON / OFF” function if you want to use a stepper like you describe.

If you’re going to mount an extruder on it anyway, I’d rather just use stock firmware and duck tape a pen to the x carriage. Use Z lift between moves (in Slic3r - Printer Settings - Extruder1 - Lift Z) and it can make pretty pictures and calibrate the machine properly.

Just occurred to me you might be able to make a hack in Slic3er if you set extrusion multiplier to 0 (filament settings), and use 1mm retraction and 1mm “extra length on restart” (Extruder1).

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Thank you Peter, that’s precisely the kind of direction I was hoping for. I want the machine to behave as much like a live machine (except with no heat). Having the extrude and retract functions move the pen in contact with the paper and back will do that. I have much to learn but I now have a direction to explore. Thanks again. - Eric

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Have you had any luck with this Eric? I am trying to do the same thing and would be interested in hearing about how you set it up.