DIY Ultimaker 2+ Dual Extrusion - Switching principle (UM2s)


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Time to upgrade my UM2 to dual extrusion printer. I got this switching mechanism idea already a year ago, but never took time to realize. Since the first tests seems to be promising, it's time to share this upgrade.
It's working with a simple cam-plate, which is moving both nozzles at the same time. The cam-plate is bi-stable, by using the existing springs which also hold the teflon isolator in place.

Benefits of this modification, besides enabling 2 material prints:
  • Simple modification on the existing hardware
  • Switching is done above bed clips, so no loss of additional print space
  • Modification works both on UM2 and UM2+

  • Of course you will need a second extrusion train. Besides that, the good news is, the most important parts to be modified are already in your UM2. Basically you need to cut the bottom-plate in half, creating 2 levers. Modify them, so they could rotate. Bolt a bearing (W 627/3-2Z) on the front side of the top plate, used for the switch plate. The only part left is the cam-plate.

    In my case it's a laser cuted PS plate. It surprisingly surveys already multiple days, none stop printing with 240 degrees nozzles & 70 degrees heated build plate.

    Then on both sides of the printer, you need a 'switching-block'. Just a simple printed part should do the job. An other interesting working solution: use the UM side bearings as switching location. Then you only need a 'X' movement to do the switching action. But I leave this to your own imagination.


  • DXF cam-plate
  • I didn't use 2D drawings. So for the other modifications, look carflully to the 3D pictures. All 3 bolt holes are nicely centered.
  • The back side (shaft) needs some more modifications. I you have a more easy solution, please let me know.

  • The most important thing in the firmware, is tell your UM2(+) to use a second nozzle. There are basically 2 options:
  • DIY: so download the right Marlin firmware from Github and change the number of extruders. If you don't know how to do this, search the UM forum for more info.
  • There might be a second option, using the Mark2 firmware & software. This community is quite active, so I guess you could get support from them.

  • For the first trial I'm using the 'old' Cura 15.04 version and created a VBA-program (Excel) to modify all 'T0' and 'T1' commands, adding the right switching movements. Now all updates & modifications are done, it's time to start the first dual print.

    Still going strong, during this longer test: Dragons egg.
    Print: 0.1mm layer height; PET white and PLA gold; buildplate 70 degrees.
    Slicer: Cura 2.4.
    I did update cura, with some UM2s machine settings. So all the slicing is done within cura. When for instance the switching locations or nozzle offset needs to be changed a bit, it's now simply changable in the extruder-definition files.

    Now the dual color printer is ready, it's time to print something... So I designed some duplo compatible characters and printed the name of my new born son.
    Printing took about 7 days none stop printing (0.1mm layer height), w/o any switching problems.
    Uploaded most characters to