This "Spring Enhancer" increases the amount of force your existing spring will apply onto the filament, allowing for more consistent filament feeding. It's a simple add-on to your existing "Minimalistic MK8 Replacement" by emmett.
In the original design, Thingiverse members suggested to buy the compression spring from McMaster-Carr (part # 9657K311): http://www.mcmaster.com/#9657k331/=v4n93e .
However, I could tell the spring wasn't applying enough force, and a lot of force was getting wasted in the "bend" the spring was making due to the angle with which it connected to the arm.
Since the force a spring applies is directly proportional to the distance it is being compressed, I created this little add-on that accomplishes two things:
1) Shortens the distance between the base and arm of the Minimalistic MK8 replacement, thereby compressing the spring more.
2) Aligns the spring much better with the lever arm, so the spring does not bend.
I printed this using MakerWare's PLA STANDARD RESOLUTION preset:
Layer Height: 0.20mm
I always print at 230C with a 40C build plate temperature, but you can print however you prefer. You will need to turn on supports because there is an overhang.
For Replicator Dual: I recommend you print my replacement Extruder Block which allows the Minimalistic MK8 extruder arms to move freely without being obstructed by the Extruder Block Top Plate: http://www.thingiverse.com/thing:607712