This clamp prevents the filament from undesired unwinding and from falling off the spools. If used while printing, no locking screws should be used, so the clamp can freely slide over the edge of the spool. The clamp then prevents the filament from falling off the spool sideways, which could cause it to get mangled up. This clamp also makes it much easier to manually unwind a bit of filament, and straighten it, to prevent underextrusion on UM2 printers. Lastly, this clamp can be used to fix the filament while in storage, so it does not unwind, fall off, or get stuck under itself.
The sliding action around the edge of the spool only works for colorFabb and identical spools. Ultimaker and ICE spools do have diagonal spokes that prevent the clamp from sliding. The clamping-function while in storage however, also works for Ultimaker (non-NFC) and ICE spools.
Test the sliding function carefully before use, to make sure it does not get locked-up at some points around the edge!
The zip-file contains the original RSDOC-designs, STL-files to print, several JPG-images, and a text-file with more info. The design is published under a CC BY-SA license.
File: anti_unwind_clamp.zip (ZIP-file - 2.6MB)