Sunday, August 09, 2009
Success with Simple Pinch-Wheel Extruder
I thought I'd take a second to post some exciting success with our new pinch-wheel extruder. My first post (a few months ago) is here.
Our pinch-wheel extruder is extremely simple, and has gone through a few design iteratations. We have tried both some random DC gear motors as well as some steppers that we had laying about, before finally replacing the motor with the very torquey Kysan DC gearmotor motor used in the Makerbot plastruder. The other motors that we tried usually didn't have enough torque, and in the case of the stepper, didn't produce a constant flow of plastic (the flow would be quick immediately after a step, then slow down considerably).
We changed the toothed gear from one with very small teeth to one more similar to the Makerbot plastruder, with very large teeth. The remarkable thing we found is how tight the gap has to be between the toothed gear and idler wheel -- our initial designs had a much larger gap, and didn't extrude very well. Last night we reduced the gap to the point where we have to taper the plastic filament to get it to initially feed, and it's actually *crushing* the filament quite a bit, but it has a wonderful extrude rate -- the plastic POURS out of it. We're still tinkering with feed rates and speeds, and aren't running at maximum speed just yet, so I don't have any numbers.
Since last time we've replaced our dsPIC controller with a full set of Makerbot Gen3 electronics, and we've switched from HDPE (which we didn't have much luck with) to ABS.
Here are our first prints (we found random interesting things on Thingiverse):
We are using a piece of dense cardboard (from a binder) as a build platform, with some double-sided tape on the spot where we print.
thanks for reading :)
How about some more details. Got any construction pictures of your extruder. How about info about the cnc. What plans did you use, size etc.
Also could we get a parts list and some rough dimensions and/or pics of your extruder. I'd like to put one together just for fun.
Why I am interested is that it looks like this extruder, unlike most, could be put together from scratch without printed parts without a lot of precision metal pieces. That's a powerful advantage.
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