What possibilities are there to add a third and fourth extruder to GT2560 rev A? The board by default contains connections for two sets of extruder drivers and steppers and has no obvious way to connect more, or some kind of shield/extender.

I was thinking about few possibilities:

  1. find 3 unused pins to control another driver - I think bltouch and pwm fan might be easily available. Not sure if MAX endstops (which are free now) can be used.
  2. some kind of drivers multiplexing - what if I shared STEP and DIR pins between multiple drivers and used E1_STEP and E1_DIR as E2_ENABLE and E3_ENABLE? I do not want color mixing so only one active extruder at a time might be enough?
  3. remove both extruder drivers and use these 6 pins as an interface for some kind of extender?

I am a SW developer and my experience with electronics is very limited so no idea if any of these makes sense.

Photos with layout and captions:

Pinout: https://reprap.org/wiki/Geeetech_GT2560

  • $\begingroup$ Have you found a commercial mount which supports four hotends? Just wondering how you are planning to use these additional output drivers. $\endgroup$ Feb 8, 2019 at 15:06
  • $\begingroup$ @CarlWitthoft I was thinking about something similar to Prusa MMUv1 - 4-way junction, or the 5in1 diamond hotend. There is the Kraken too but that is worth more than my current printer :) $\endgroup$
    – jkavalik
    Feb 8, 2019 at 15:16


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