Titan adaptor for using 3mm ID reverse-Bowden tube

This is a small adaptor meant primarily for using 4mm OD/3mm ID PTFE tubing for a reverse bowden tube at the input of a Titan extruder. I use a reverse-bowden arrangement to eliminate issues with filament spilling off a nearly-full spool and to get cleaner prints by preventing irregular jerking of filament from the spool due to nozzle movement (see included diagram). The usual 4mm OD/2mm ID PTFE tube will work for that, but using a 3mm ID tube makes threading the filament through a long tube easier and reduces frictional drag during printing. But a 3mm ID tube doesn't control the feed position of the filament into the Titan extruder gear very well, which can sometimes cause drive problems. This adaptor has a ~2mm opening for keeping the filament centered into the gear.

The PTFE tubing gets inserted into the adaptor, which can then be optionally locked in with a narrow 4" nylon cable tie around it. The other end of the adaptor gets inserted into the Titan extruder where a PTFE tube would usually go to feed into the drive gear.

The adaptor end is tapered, which also makes it easier to insert or remove from the Titan (simplifies loading filament and also makes doing "atomic pull" nozzle cleaning much easier). The adaptor could, of course, be used with a normal 2mm ID PTFE tube at its input if only those benefits are wanted.

Print with 0.4mm nozzle and 0.2mm layer height to minimize inside friction. It takes only about 10 minutes to print, being such a small part.

There are two STL files provided, one that is straight and one that has a 25 degree bend in it -- use the one which best suits how your PTFE tube runs.