I have been involved into 3D printing for the last 2 years and one of the biggest problems are related to the material feeding. Todays extruders that uses one driven wheel with a spring loaded bearing that pushes the filament against the drive wheel. This method has some disadvantages as- Low pushing force- Risk of grinding the filament that leads to a failed print- Slipping that leads to underextrusion- Deforming the filament that leads to increased friction in the bowden tube.The new Bondtech extruder uses 2 drive wheels that are equipped with sharp teeths that grab the filament on both sides wich gives a lot of advantages over the standard extruders. Some of the most important ones are the following.- Huge pushing power that elliminates the risk of under extrusion, tests have   verified that it is over 9 kg with a 1.75 mm filament.- Minimal risk for filament grinding- Possible to go high speed due to the big the pushing power, tests have been   made with 250 mm/s printing with 0.4 mm nozzle and with no filament grinds.- Possible to go with small nozzles - High torque Nema17 stepper with a high precison planetary gearbox gives   high resolution and fast retracts.- Adjustable secondary drive wheel to optimize grip.- Easy access to drive wheels for cleaning A walkthrough of the design by Eric Lien: http://youtu.be/18dc96ZMd2I?list=FLCB1vETRBsx4WjMZ8_xiOyg The extruder in action: https://plus.google.com/109092260040411784841/posts/gnn6rmyWWC6 In a few weeks time I will be able to provide kits with the metal parts and also professional 3D printed SLS parts for the housing components. The current version supports only 1.75 mm filament but a 3.0 mm version are in development.