About this 3D model

After hours of work I had problem with the new extruder from Makerbot. THe spring was not strong as at the beginning --> PLA was not always taken by the extruder. So I made an adjustable extruder to solve this problem. You just need a M4 bolt, a M4 nut and a little spring. All the rest is like "Replicator 2 Drive Block"