MK5-6 STEPSTRUDER NEMA 23 DIRECT DRIVE PIVOTING FILAMENT PUSHER

thingiverse

This direct-drive extruder mechanism fits perfectly with MK5-6 hotends and dinos. The creator initially considered moving to a stepper drive extruder but was hesitant to wait for MakerBot's new NEMA 17. They also faced issues with the Delrin plunger. Influenced by Wade's design, they incorporated a ball bearing to provide pressure between the filament and drive wheel. However, they disliked the four bolts required to adjust filament change in Wade's design. Their primary goals were maintaining accessibility and providing mechanical advantage where necessary. The worm grove of the drive gear is positioned close to the motor face for better efficiency. The teflon guide tube was extended to a point below the drive wheel. The pivoting arm applies filament pressure using just one screw and spring pair, unlike Wade's design that required four. This configuration offers a mechanical advantage of approximately 2:1 in terms of filament pinch strength versus spring force. Additionally, the arm can be rotated out of the way by backing off the screw completely, ensuring ease of access without removal. The extruder includes a sponge-filled hat to remove dust from the filament during feeding. This hat is also pivotable for simpler filament insertion. The design features imperial measurements, but other versions can be provided upon request. Detailed build instructions are given, with special emphasis on using a NEMA 23 motor rated at 144oz-in at 3 amps. Temperature concerns are mentioned, but no issues have been encountered yet. Tensioner arm assembly requires specific drilling and tapping of aluminum faceplates for NEMA 23 motors. The main body may need holes chased based on fastener size and printer calibration. The MK5 teflon tubing length should be checked, as additional teflon tubing might be required. A smaller teflon tube (1/4" OD x 1/16" ID) is also mentioned for compatibility with 1.75mm filament, though testing with 1.8mm abs was unsuccessful. Ball bearings should fit the 1/4" ID and 5/8" OD dimensions but may need adjustments in the model. The drive gear is drilled to accommodate the 1/4" shaft of NEMA 23 motors, which can be done with a lathe, drill press, or hand drill.