A modified print head top part if you want to run dual filament diameters in your UM2, and use a 4mm OD/2mm ID pfte tube for the 1.75mm filament.
It ...is a pretty straight-forward install, even if it requires you to disassemble the whole printhead :-)
3d model print parameters
- 3DSolex 1.75mm Olsson Block
- 4mm bowden coupling (search for "Bowden Coupling 4mm" on Aliexpress and you will find)
- Original bowden coupling
-... Printed 4mm bowden clip (you can find it amongst my other designs)
- 4mm OD/2mm ID bowden tube