This Fitting Insert is inserted into the threaded end of the “Y” Adapter PC4-M10 PTFE Connector to reduce the chances of the filament getting stuck as the filament exits the “Y” Adapter and goes to the printer.

I printed @EdJohnson's “Bambu AMS No-Catch Y-Splitter PC4-M10”, which is a beautiful design, using PC4-M10 PTFE connectors.  Ed's design allows you to install filament from an external spool without having to disconnect the PTFE tubing from the AMS to the Bambu Lab printer.

Since the PC4-M10 PTFE connectors have machining marks and a shallow taper on the ID, I was having filaments getting stuck at the connector.

When I installed my “Fitting Insert” it helped guide the filament to the center of the PC4-M10 fitting and eliminated filaments from getting stuck.

NOTE: This was designed for the Bambu Lab PTFE tubing: 4mm OD/2.5 mm ID.  If you use smaller ID PTFE tubing you may need to modify the insert ID accordingly.

I printed the Insert using ABS at a a 0.16 mm Layer Height to minimize layer lines.

Post Processing:

Even printing at the 0.16 mm layer height, I still needed to gently sand (320 grit wrapped around a Q-tip) the inside diameter of the insert to eliminate the layer lines so that the filament didn't get caught .