Differential Extruder

thingiverse

Differential Extruder combines the advantages of a Bowden extruder and Direct Drive extruder. It gives you a light print head which has an extruder wheel close to the hotend. Differential extruder uses two "loop" timing belts to move the print head and to turn the extruder wheel. The print head contains a timing pulley which is connected to the extruder wheel. The two "loop" timing belts engage the pulley from two opposite sides. When both belts pull in the same direction, they pull the timing pulley in the print head equally on both sides. This means that the timing pulley in the print head can't spin. It also means that since both belts are pulling in the same direction, they pull the print head along. When the same two "loop" timing belts turn in opposite directions to each other, they rotate the pulley (and the extrusion wheel) whilst the print head remains stationary. Differential Extruder requires just two stepper motors, which is the same to what current 3d printers have for i3 geometry. However, the firmware for this extruder should be programmed so that the steppers' combined spins deliver desired axis movements and extruder wheel rotations. Please check out the videos I uploaded to GitHub: https://github.com/vedransi/Differential-Extruder (NOTE: I will soon upload a translation mechanism that will enable you to retrofit this extruder onto existing i3-style printers, i.e. you won't have to re-program the firmware.) The only STL uploaded here is intended to get you familiar with this new concept. Please print it and follow the photos to assemble the print head carriage. The last photo shows all parts I used for it. The photo before the last one shows how the belts are engaged by the driving mechanism. The uploaded STL is just a demonstrative example. Please feel free to modify it and adjust it in any way that would suit your 3d printer. Please also feel free to apply it to other printer geometries and kinematics. I think that this kind of extruder would be very applicable to CoreXY and H-bot kinematics.