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.
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.
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 youmagine.com.