Filament spool brake

No

No

0.2 or 0.3 (according to preference)

15% (or according to preference)

This device limits the rotation of a filament spool when the extruder is stopping and starting, to prevent over-run and subsequent loose filament tangles. I had fitted a spool holder with bearings, and it didn't take much to start the spool spinning on a busy print!

It is designed for printers constructed with 20x20 extrusions, and should be adjusted so that the blade just touches the spool rim - just enough to cause a slight drag.

Additional components:
50mm M4 hexagonal-head machine screw.
M4 T-nut
M4 washer

Other information:

1. This thing is made using PLA+ and TPU, but the TPU is optional - there's plenty of scope for ingenuity!
2. TPU is used to make the blade, and the filament needs to be really dry to stand a fighting chance of printing it successfully. I stuck it to the body using 3M double-sided tape, but CA would work.
3. The blade isn't strictly necessary, as for several years I'd used a piece of draft-excluder sticky-backed foam (the really cheap stuff that's easy to flatten); this worked really well, but I wasn't going to buy a whole new roll of the stuff just to get a 43mm length!
4. The blade was designed in FreeCAD as it was easier to get the curved edges and fillets that I wanted.