VM Extruder

thingiverse

After using a Gregfrost extruder for some time, I decided to make modifications to its basic design. Firstly, I replaced the hobbed bolt with a large-diameter filament driver that requires no machining. Secondly, I added a spring-loaded over-center latch on the idler arm, allowing it to open without unscrewing anything. Lastly, I modified the idler arm to open flat, providing better access for inspecting and cleaning the filament drive. After assembling these changes and running several test parts, I utilized this extruder in building parts for Sublime's printed lathe, clocking in at around 45 hours of runtime with a longest single build lasting 14 hours without any hiccups. I even pushed it to run at up to 100mm/s, which it handled smoothly. The extruder body also has mounting provisions for the Makergear hotend. A Zip file containing Solidworks 2011 source files is available for download. If you have a Gregfrost extruder, you can reuse all parts except the body, idler arm, and connecting hardware. Print the extruder body in ABS, as no support should be required with built-in removable supports. The rest of the parts can be printed in either ABS or PLA. To create the filament driver drum, you can use a McMaster-Carr aluminum spacer (P/N 92510A797) or machine your own with provided dimensions. Tap two 6-32 holes in the drum, install 6-32 x 3/16 setscrews, and clamp it into the hobbing jig with 2 8-32 bearings and an M8 bolt & nut. Assemble the drum into the hobbing jig, insert a tap/crank with screws in each bearing hole, and spin until the groove is about half filament diameter deep. For the latch link, use an R/C airplane steel wire pushrod. Bend it to fit the drawing and attach it to the pivot block using leftover pushrod wire. Attach two short pieces of filament as pins on the tabs on the body. Insert the threaded end of the wire link through the pivot block, add an idler spring and 4-40 locknut. To assemble, install main bearings, big gear, bolt, driver drum, and locknut. Adjust the driver drum position for alignment with the filament path. Install the idler bearing and pin into the arm, attach it to the body using a 6-32 screw. Assemble the extruder, hot end, motor, etc., ensuring the length of the mounting screw by the idler doesn't interfere with its operation.