RepRap: Blog

I've done an alternative to the polymer extruder design that allows the 3mm diameter input filament to run straight down the drive screw without bending. This should allow us to use more brittle and stiffer materials in addition to CAPA. It should also make it easier to drop short lengths of filament down it from an automatic magazine at the side of the machine, for materials that can't be put on a long roll.

I drilled a 5mm-deep 3mm hole in the top of the M5 drive screw and soldered in a length of 3mm steel hawser that I bought at the local hardware shop. I had to grind/file down the hawser end a bit to get it to fit; I also added a little solder flux to get good surface wetting. It was important to be parsimonious with the solder, lest it soak up the wire and make it go rigid. On the other end I soldered another short piece of M5 studding, then soldered an M5 nut onto that.

I modified the motor mount to move it back from the line of travel of the filament being extruded, and made a small drive with an M5-nut-shaped hole.

Rather convieniently the predominant drive direction (anti-clockwise) tends to tighten the hawser coils, though the thing does drive perfectly well in both directions.

There's a video of the first mechanical test on the RepRap videos page.

Labels: new extruder design, stiff brittle extrudate