Engineering Projects/MakerBot Improvement/printhead improvement

Problem
Printhead is knocking over tall objects, is clipping small pieces shooting them out of the makerbot. This is with rafts and support.

Here are three video's showing the printhead moving, did not capture any clicking noises. video1, video2,video 3

Implement
A Spring Loaded, constant pressure on the PLA may improve the printing. Need a hardware kit.

Theory of Operation
Looks like the stepper motor has plenty of pulling power, and that this device actually creates more friction, makes the stepper motor pull even harder, but the result is a constant tension above the stepper motor, which should lead to more constant pressure pushing the PLA through the heated nozzle.