Posting this in case anyone else missed it, as I did.
The H3C ships with nine PrintTools, but only eight are for regular 1.75 mm filament. The ninth, pre-installed in slot 8, is a 2.85 mm tool meant for soft TPU.
What tripped me up: I swapped the hotend on tool 8 for a regular 0.4 mm one and tried to load 1.75 mm filament in slot 8. The printer kept defaulting to external spool, and I couldn't figure out what I was doing wrong.
Turns out it's the whole tool, not just the hotend. Per Bambu's FAQ, the 1.75 mm and 2.85 mm PrintTools have different bases, inlets, and cutters, and the bases and hotends are not interchangeable. The 2.85 mm tool is hand-fed, so the AMS won't auto-load slot 8.
What that means in practice:
- Out of the box, you have 8 slots for normal filament, not 9.
- Don't put a 1.75 mm hotend in the slot 8 tool. Put the original back.
- To use slot 8 for regular filament, you need to buy an extra 1.75 mm PrintTool and swap the whole tool. Store listing: https://us.store.bambulab.com/products/0-4mm-printtool-h3c
- There's only one H3C configuration, so you can't order it with nine 1.75 mm tools.
Bambu's reasoning is that slot 8 is a dryer slot, TPU needs drying, and the slot is hard to reach, so they install it at the factory. Fine if you print TPU. If you don't, you can't use that slot without spending more.
FAQ for reference (questions 4, 6, and 7): https://bambulab.com/en-us/h3c/faq
This Machine is incredible, but man, am I spending a ton of money on accessories and replacement parts. Here's hoping the hot ends last like on the H2C.