Friday, February 20, 2009


Stepper pinch-wheel extruder building

RepRap stepper extruder working from Adrian Bowyer on Vimeo.

Here's the prototype stepper pinch-wheel extruder building the coat hook. As Nophead has always rightly maintained, good control of the polymer flow gives the best quality results. This one came out as good as the ones he makes on Hydraraptor. And the slow-running-stepper lights are pretty...

It may also be possible to use a pinch-wheel extruder to drive a syringe - simply put a plastic-coated metal shaft through it, and use that to push/pull the plunger. But because of the large diameter of any useful syringe, the stepper may have to be running so slowly that the output would be a bit jerky. Microstepping may solve that, of course.

Very nice! I can't tell which controller board you're using from the clip. Can you tell me about how many amps you're pumping into that stepper?

Is Darwin really being that loud, Adrian, or is you mike's gain way up? I know when I try to capture videoclips of things the mike on the digital camera magnifies enormously whatever sound is available.

I've got to put some multicoloured LED's on T2's controller board so that I can have some nice twinklies, too! :-D
Well cool.

Have you got a comparative build time to see how much faster it will go ??
It looks great have you released the files yet for the two component parts?
These parts look much easier to fabricate out of plywood for a repstrap machine.
So far I have the Alu block with Welding tip as per Nopheads new extruder concept. I also have an original extruder head neither with any means of drive system. this new design is posible for the average hobyist to build with limited machine tools.
I have full electronics & motors on two repstraps machines & a Repstrap Darwin half built the bigest stummbling point has been an easy to build extruder mechanism. This looks like the ideal solution. For the Average SW/Firmware/hardware enginner with a kitchen and utillity room in his partners house to build stuff in. She is amother Archetect/SW enginner so I get away with it. Anoyingly she knows a little more Gcode than I do./both of us are very egar to get extruding thou..Nopheads blogs are great motivator.
a Dyslexic Enginner, Blogger needs a spell checker for the inflicte.
Word verification another dyslexic nightmare.
Can it move PLA filament?

Vik :v)
I'm using Zach's latest stepper board. I haven't measured the current, but from the position of the controlling pot I'd guess about 500mA. The noise is the silly camera mike - in reality you don't notice the noise if you're holding a conversation next to it for example.

Again, I haven't timed it (and nor have I cranked it up as fast as it'll go), but I guess it's already about 0.6 the build time.

This is the prototype. I hope to do a proper design this weekend that'll use standard parts. It really is simple; you could probably make a wooden one in about half an hour with drills, chisels, a trepanning cutter, and some care...

Zach's lasercut equivalent works fine with PLA - he and I tried it in Madrid. So I see no reason why this one won't too. In fact, I'll use this prototype to build the new design in ABS, then use that to run PLA so I have one for each material.
Is that roughly 500ma number the absolute minimum setting you are able to extrude with?
No - I backed it down till it started to miss steps, then wound it back up a bit.
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