Dagnall Y Extruder

This is a simple Y extruder, building on the excellent work from others.
I liked the PTFE sleeved design of the flux capacitor, but found it very difficult to make the 8mm PTFE parts with accurately drilled 2mm holes. The un-sleeved designs, I thought, might suffer from wear.
So this design relies only on easily available 4mm diameter by 2mm id Teflon tube, as used in most bowden systems.
The Y part uses a split part of tube to gently feed the filament into the combined hole.
The Cut-away photo shows how it works.

After I saw Gimle's nice version http://www.thingiverse.com/thing:2326087 I have been re-designing this and have added a Printable M10 bowden connector.
This fits the M10 version of my Y, and also the inlet of the E3D extruder (at least those with M10 threads!).
The big advantage of this is that the 4mm PTFE tubing goes right through the connector and you can use a single piece right from the Y coupling down into the Extruder. This means that there are less places for the filament to be trapped or stick. I have sketched a section of an extruder with the Y to illustrate this.

I have included a tool to hold a common knife blade to make the special split, although I recommend actually having the blade in a knife holder rather than having the blade alone as in the photo!.

I am working on files to make this work with Cura 2.4 (on) for Delta printers and these are available at:
https://github.com/dagnall53/JSONS-for-Cura2_3
These files look after changing the filaments.

The penultimate photo shows a transparent /black print halfway through. There is lots of stringing going to the ooze tower. However, when finished, the transparency of the "transparent" PLA was significantly less than when it is printed by itself. Obviously this is a very severe test of the two filament - one nozzle concept. The final photo shows the finished indicator compared to a version made of transparent PLA and then painted black. Both have the same bulbs, but you can see the two colour print one (the lower example in the photo) has significantly dimmer illumination, due to the transparent filament printing slightly grey despite a large (~20mm square) ooze and changeover tower.

To give confidence that the tubing is being held securely, I recommend making a small mark on the tubing as it enters the bowden coupling, so you can see if it moves during printing.