The window is a nice touch.  Did you size the box to match your drill?

Yes.  When open it is just tall enough so the shaft matches the drill sitting on it's battery.

Nice variation on the design.  I like it !!!!

1) recycle bad/short filament

I've had some trouble extruding long enough lengths of black filament that doesn't snap during winding (due to moisture and other problems) so the filament chopper lets me give that filament another go through the filastruder, as well as any leftovers I have lying around.

2) diluting masterbatch percentage

I had been using 2% masterbatch, which seems to be too high.  After chopping up all the bad filament, I plan to dry it all in the oven dilute it down 2:1 with more natural abs to improve its strength.

3) better mixing masterbatch for improved strength

The masterbatch I use also comes in fairly big pellets, and even with a lower percentage I occasionally get weak spots that break when winding, presumably because a masterbatch pellet has made it through without enough mixing.

4) better mixing masterbatch for more even colors

I've had problems getting colors to be even in the first pass without increasing the masterbatch percentage so high that the filament is brittle.  Instead, it tends to "pulse" a bright color whenever a masterbatch pellets comes through and fade to white in-between.  Chopping up the filament and extruding a second time should fix this and also allow subtle color mixes that wouldn't possible otherwise.

So what do you use the chopped filament for?

That's a really nice setup. Any more photos?

That's all I have at the moment. I'm thinking of adding a filament feed drive to it, if I do I'll take pics of the guts while I have it opened up.

It's actually quite simple, some Actibotics parts to link the drive motor to the end mill while holding all the bits in proper alignment, the rest of it is parts I rendered in Sketchup and Solidworks then printed with filament made in a Filastruder, some of it having been reprocessed through the much larger and clunkier V1 version.

Strictly a manual feed at the moment, not a problem unless I want to do a entire roll, the short leftovers go through pretty quick just feeding by hand. The small end mill is spinning fast enough that the size is pretty uniform regardless of how fast or slow the filament goes in.

Ian was doing one as well, but not sure that I ever saw plans for it.

I was checking out that wood chipper at Harbor Freight as well, I think it would be interesting to try. I have access to a bandsaw, so I could easily hack up parts small enough to fit in there. Being able to recycle a little would be nice, if I can avoid dumping in a landfill for a little extra effort, it's worth it. The $300 hand powered one was a bit much, but $100 for a motorized setup is doable.

The slot-style opening takes 1.5" max, so I try to make my smallest dimension just under that.  You can buy a drawstring laundry bag at Walmart for $4 to tie to the bottom to catch the plastic.  My first attempt was with a Rubbermaid container but the airflow blew plastic everywhere.