Print with ABS or PETG with brim and without support. Cut bowden properly at 90 degrees and insert fully (15mm, using a rag and some force; the bowden inputs are slightly conical). It will hold very well.
If you have problems, you could reprint the splitter slightly smaller, say at 98% or so.
Follow the filament's natural path for both AMS and external spool. The filament path in all available Y-Splitter designs is optimal only for the AMS. For the external spool, however, the splitter usually turns in an up direction, which can cause the filament to get snag when inserting it.
I have been using this Y-Splitter for over a week and can confirm it works beautifully. The AMS colour changes work effortlessly, and I am able to start a print with the external spool in a matter of seconds.
Print Settings I highly recommend printing from the official profile included above to ensure this performs correctly. If you want to slice it yourself though, here's the core settings:
Chamomile_3D
