Double-worm gear extruder?
Mike
I've been impressed with nophead's "no compromise extruder" and
wondered about making an extruder with two driven hobbed wheels to
grab both sides of the filament.
I'm sure the pulling power woudn't double, but it seems to me that it
should outperform a single-sided friction drive?
I've mocked up the idea in Lego Digital Designer - file uploaded as
'DoubleWormExtruder.jpg'
Cheers
Mike
rbisping
it but so far havent realy had success with making the pinch
mechanism.
It needs some rather precise machining and so far i havent bothered to
make a third set (first two failed me horibly)
Zach 'Hoeken' Smith
The idea was to use two counter-rotating threaded screws to push the filament. The original MK1/MK2 extruders from RepRap used a single screw to drive the filament. This worked okay, but the filament also slowly rotated with the screw causing major tangling problems. The MK3/MK4 extruders solved that with a pinch drive. Threaded rods do provide a ton of grip, so I wanted to solve that with two screws rotating in opposite directions to negate the force. Of course this involved using left and right handed threads and a bunch of custom machined stuff.
Long story short it is a viable idea, but the tolerance and stuff to make it work are really difficult to achieve in the price range that we have put ourselves in. If we wanted to build a $300 super extruder, this is the route I'd choose.
If anyone wants to see the dev work I did on this, check out the svn repo (i think totem-pole.dxf is the main layout file): http://svn.makerbot.com/users/hoeken/plastruder-twindrive/
We are in the process of testing the final prototype drive gear based on nopheads design which will be a drop-in replacement for the aluminum drive gear currently used. Currently it looks to give about 30% more grip. Pretty rad.
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RyanP
part as opposed to a "next gen" feature!
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Zach 'Hoeken' Smith
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Ethan Dicks
> yup.. it will be a drop in replacement.
Sounds great!
Since I have a local friend with a small lathe (he makes table-top
steam engines from scratch), I'm wondering where to pick up tools to
make it possible for us to make extruder parts. So far, I have been
entirely unsuccessful in finding metric tools locally (Ohio). Where
do people in the U.S. go for 3mm drill bits and M3 taps? Wrenches,
sockets, and allen wrenches? Sure. You need those to fix modern
cars, and they are available at any store. Metric machine tools,
though, are not needed by Joe Sixpack the Shade Tree Mechanic, so are
not as widely available.
Suggestions?
-ethan
Zach 'Hoeken' Smith
Mike
The intent was to drive one piece of M8 studding that's parallel to
the build platform (and the X axis), geared 1:1 to another piece of
studding in the same plane.
Those counter-rotating studs act as worm screws to drive hobbed gears
underneath them in opposite directions, these are on axles oriented
parallel to the Y axis.
The pinch wheels are then on the end of those axles (represented by
the wheels on the front of my Lego model). I expect to hob the pinch
wheels M3 and will have to allow one to move a little against a
spring.
So the final result should be one stepper driving two pinch wheels,
both hobbed for extra grip and with forces balanced nicely.
Mike
Zach 'Hoeken' Smith
Mike
Mike
but we'll see who knocks the kinks out of it in practice.
Jerry Isdale
I've seen it in action and he gets VERY reliable prints with it. He
has been selling parts he makes and needs reliability - he's paid for
his makerbot already with parts sold.
On Feb 9, 5:41 pm, Mike <micht...@gmail.com> wrote: