MMU2S Selector - Large Bore, With Magnet, 18mm round cutter

This is a remix of the various MMU2S selectors out there, though the specific one I modified is not listed on thingiverse.

It includes the larger bore tapered filament path to reduce jams, which is a fairly common feature in most of the alternate selectors

It also has a magnet mount for the filament sensor steel ball, which improves sensor reliability. I did enlarge the magnet pocket about as far as I felt comfortable, as the ones I'd previously tried weren't able to fit the magnets that came with my Mk3/Mk3S/MMU2S kits. it's still a very snug fit, but I am now able to get the magnet installed. There is a hole present to press the magnet out again.

The big change I included is converting this to accept an 18mm round cutting blade, commonly used in fabric cutters. This so far has proven to eliminate jams from the stock style cutting blade. While the cutting blade is not currently being utilized in the software on the MMU2/MMU2S, this will give some ability to keep any stringing under control. The cutting wheels have a slightly larger inner diameter, but I kept the screw and nut sizing so you can still use the spares/originals that came with your printer kit. The redesigned cap will keep it clamped in place.

Testing is so far going well, PETG is highly recommended, as the FINDA mount will crack if you use PLA.