A little EZstruder adapter...

[DonaldJ]

This could easily be modified to work on any carriage assembly.

I tried 3mm filament with my beefy stepper but the filament stripped. It's either not enough spring pressure or drive roller teeth that are not quite sharp enough. Probably both.

A very neat feature of the EZstruder is the access port on the right side to clean the teeth.

http://www.thingiverse.com/thing:177550

[flickerfly]

I'm also a big fan of the little cleaning port on the side. I'll blow in it sometimes. I also have a little baby bottle cleaner of the right size to jam in and clean it out.