PrintShift 3.0 Build Series: Step 4

This chapter includes both how to power AND how to control your PrintShift ejector! For this build, the control system is moving the Z axis to the top and activating a microswitch to turn on the ejector motor.

I’ll post an alternative control later - using a relay activated by the raspberry pi.

Previous Step:

Motorize the PrintShift Conveyor Belt

Next Step:

PrintShift Gcode: Ejecting Parts

Materials Needed

  1. Prusa Mini, assembled, printing, with the conveyor belt bed and ejector motor already attached.
  2. Parts Printed in Step 1, from the Small Parts stl
  3. Parts from the Parts Kit
    • 3 - M3 screw, 12mm long
    • 3 - post-instert 3030 T-Nut, m3 tapped
    • 1 - ring terminal
    • 1 - microswitch
    • various lengths of wire
    • 3 - wire nuts
    • 1 - 24v->5v buck converter (optional, only needed if you want to add a pi later (hint: you do))
    • 4 - heat shrink solder tubes
    • 4 - zip ties

Tools Needed

  1. 2.5mm allen key
  2. wire cutter/stripper
  3. heat gun


  1. First the microswitch, since we need to wire it up before installing.
    • There are three pins on the microswitch
      • C - Common, at the root of the lever
      • NO - Normally Open, in the middle
      • NC - Normally Closed, at the roller or end of the lever
    • We’re going to connect C and NO; that means that, normally the switch is off, but when we press the lever it will turn the motor on.
    • First cut 2 of the heat shrink solder tubes so that there’s only a little heatshrink past the solder
    • then thread both onto the same (at least) 40” or 1 meter length of red wire, long sides together.
      • Later we’ll cut this wire - one side goes to the motor, the other goes to the HOT junction
      • for now, though, it’s easier to leave it long
    • Strip the ends of the wire, and thread one end through the C terminal, and the other through the NO terminal
    • Slide the heat shrink solder tubes into place, and heat til the solder melts onto the wire + terminal
  2. The microswitch then gets mounted to the top front of the Z axis
    • Insert the loop of wire first, and then the microswitch into the microswitch mount. The lever end should point AWAY from the mounting hole!
      • Use a small zip tie to secure the microswitch
    • Take one 12mm M3 screw and one post-insert T-Nut and mount the limit switch mount to the front, top of the Z axis
    • The bottom of the microswitch mount’s should be just above the top of the Z axis extrusion - but we can fine-adjust it later.
  3. Mount the buck converter
    • Using two 12mm M3 screws and two post-insert T-Nuts, mount the microswitch on the bottom of the right side of the Z extrusion
      • Make sure the wires are facing the rear - it looks nicer.
  4. Wire up the Motor
    • Run the wire from the microswitch (still un cut) over to the motor. I like to zip tie it to the Y motor cable to help keep it out of the way.
    • We’re going to connect it to the + terminal on the motor
    • Cut the wire a bit longer than you need to reach the motor and strip the end
    • Thread the wire onto the motor’s + terminal, and using another heat shrink solder tube melt it into place.
    • Get your other wire, and similarly attach one end of it to the motor.
    • You can run it back parallel to the red wire
  5. Next we’re going to wire up the microswitch
    • Power from the mini goes into a wire nut, and from there goes to the microswitch and the buck converter
    • Neutral from the mini goes into a wire nut, and from there goes to the motor and the buck converter
      • If you wired the motor backwards, you can switch the motor and the microswitch to the opposite wire nuts :-)
    • The wire nuts can slot right into the 3030 extrusion and provide good wire management
    • So cut off some of the non-motor red wire from the microswitch (again leaving a bit extra) such that it’ll reach the bottom of the Z extrusion.
      • Strip all three ends
      • In the wire nut, put the red microswitch wire, the red buck converter wire, and one end of the red wire you just cut off
      • You might need to strip the buck converter wire to get a good connection
      • Just leave the end for now
  6. Next, wire up the buck converter
    • The converter got half-wired in the previous step
    • Cut the end off of the not-red wire from the motor such that it easily reaches the bottom of the Z extrusion
      • Strip all three ends again
      • In the wire nut, put the not-red motor wire, the black buck converter wire, and one end of the not-red wire you just cut off
  7. CHECK your wiring!
    • You should have two stripped, unconnected wire ends - red and not-red - and no other unconnected wire.
    • Red goes to a wire nut, which then goes to the buck converter and the the microswitch.
      • The microswitch has one wire coming in from the wire nut, and one running over to the motor.
    • Not-red goes to a wire nut, then to the buck converter and then to the motor.
  8. UNPLUG the Prusa Mini!!!
    • I mean, it should’ve been unplugged this whole time…
  9. Open up the electronics case
    • The RED wire is powered from the power switch - either the always-on leg, or the switched leg.
      • Either way is fine - mainly depends on if you want the Pi on when the printer is off.
      • Slide one of the switch connectors off, put the stripped red wire through the hole in the terminal, and slide the connector back on
    • The other wire needs a ring terminal crimped onto it - this can be done with pliers, but most wire strippers will have a pokey crimp lug.
      • Once the wire is crimped, we need a 2.5mm hex driver to remove one of the Buddy Boards screws - right by the power inlet.
      • The screw goes through the ring terminal and right back - it’s connected to the ground plane of the buddy board.
  10. DONE! I know it’s a lot of fiddling, but the wiring’s not too bad.

Video Walkthrough