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Is there a way to change the use of an extruder port on a 3D printer motherboard to move stepper motors (on y axis) on a 3D printer?

This is for a school project, and we have replaced the extruder with a laser for cutting material.

We were tasked with converting a 3D printer into LOM 3D printer, the laser is set using the fan port, however we still need two stepper motors to move material from one side of the printer to the other after each layer of material is cut.

Diagram

The mother board we are using is WitBot MKS Gen L V1.0 Controller Board Integrated mainboard Compatible Ramps1.4/Mega2560 R3 with A4988 Motor Driver for 3D.

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  • $\begingroup$ Welcome to 3DPrinting.SE! $\endgroup$ – Pᴀᴜʟsᴛᴇʀ2 Apr 12 '19 at 20:05
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    $\begingroup$ What firmware are you using? $\endgroup$ – Perplexed Dipole Apr 13 '19 at 0:39
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    $\begingroup$ I'm not sure I understand: converting a 3DP to a LASER engraver implies switching the hot-end for the diode driver and the Z axis becomes less valuable. Why are you messing around with the Y axis?!? $\endgroup$ – Roberto Lo Giacco Apr 13 '19 at 0:58
  • $\begingroup$ If you're doing a laser you can use the fan PWM output to control the laser. $\endgroup$ – user77232 Apr 13 '19 at 1:57
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    $\begingroup$ This is a huge addition that actually explains a lot. As LOM is rare, you should update your question with the additions and how it works and which motor you set up for which. In this case I would put the extruder to control 1 & 8, use X for moving 2, and Y for 4. Z is 7. $\endgroup$ – Trish Apr 13 '19 at 22:21
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If you are planning to use the printer via GCode entirely, then I don't believe it would be too complicated. For example, Marlin treats the extruder as another axis and uses absolute values for it (if absolute mode is on, of course). Since you want to have two steppers, you would have to connect them in either series or parallel (usually the Z motors are wired in parallel on RAMPS type boards, but many people are going for series since it has some benefits, one of them being that the torque will be much more similar between the two motors). Of course lower the stepper driver current to the minimum before connecting, then adjust it to whatever value you need. I don't think it will work too well if it has to keep the roll tight - in that case, you could be better off by using only one stepper and some kind of force to hold it tight... maybe a small DC motor at low currents?

You can modify your printer firmware and set your own pin assignments for everything, for example in Marlin you have the pins.h file where every pin from the Mega is mapped to different headers and drivers. I don't know if there is any LOM slicer or firmware available, but you could just use GRBL.

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With the picture shown, the LOM printer could be almost controlled entirely with a standard printer's hardware and almost no changes to the firmware:

  • Z controls stay the same, they control 7
  • X & Y will be used for the laser mirror 4 needs to be controlled by 2 motors to follow 2D Contours. I would not use a swiveling one but a steady laser that targets a 90° mirror mounted so it moves with one of the axis that reflects it to the second 90° mirror that aims it down on the workpiece and is mounted on the second axis. This would be pretty much a Core-XY setup.
  • Turning the laser on and off can - as said - easily be done with the part cooling fan control
  • The E0 signal could be used to turn the material feed on both sides, though I would use only one motor. This stepper should for speed consistency be mounted springloaded and use a roller to transfer movement to the film coil 8, best on an area that is off-limits for the laser to cut in. As a result, I would let 1 spin on itself against some resistance like a spring-loaded bar keeping the film tightened, keeping electronic complexity to a minimum.
  • Powering the heater can be done via the heater out of the board.
  • To actually move the heater, I would use the E1 signal on a long axle, pulling the mounting for it from both sides.

This would create a simple order of operations:

  1. T0 # Choose the material Feed
  2. E100 F100 # Pull 100 mm of new material via the roller 8 from 1
  3. Do XY movements with cut
  4. T1 to choose the heater movement
  5. E100 F100
  6. E-100 F100 # Fuse the film with an E1 movement back and forth (or alternate between these two lines to rest the heater on either side, speeding up the process)
  7. GOTO 1
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