Friday, July 20, 2007
Designing the next generation Mk 2 AEM
That said, I've been thinking about what the next generation extruder ought to look like. Adrian's Mk II was designed to extrude polycaprolactone (CAPA). While CAPA is a tough plastic you can cut into it with the metal thread of 1/4 inch studding relatively easily. That means that the springs that clamp the polymer pump to the filament guide can be lightweight and the torque requirement on the studding pump aren't huge.
HDPE is a tougher plastic than CAPA. It didn't take me long to realise that the #4 springs that worked well with CAPA were not quite adequate for HDPE. I sized those up to the toughest #6 springs that I could find and have since been able to do production extrusion in HDPE. Mounting #6 springs on #4 studding isn't a happy sort of thing to do, but it can be made to work.
The Solarbotics GM3 gearmotor handles both CAPA and HDPE fairly well.
It's safety clutch is set to 60 oz-in of torque. This is way more than you need for CAPA and maybe about 10-15% more than you need for pumping HDPE at the rates that I currently use. I've been able to barely pump HPP (homopolypropylene) at production rates with the GM3. ABS, however, is out of the question.
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