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goaran

remote extruder with flexible drive shaft

by goaran Feb 23, 2011

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There are some existing designs out there now for about $100 each (INSANE!!!).
I'm hoping to try my hand at this too and publish it for free, because viva la OpenSource.
From what I've seen the other solutions use a nylon worm gear with 1:30 or 1:40 ratios. They don't seem to have any backlash issues from the reading I've done, but that'd be my prime concern too.
We'll see ;)

I am working on a very similar idea, I to am using a worm drive to compensate for the 15 degree give in the flexible axle. Was this idea ever explored?

I am working on a very similar idea, I to am using a worm drive to compensate for the 15 degree give in the flexible axle. Was this idea ever explored?

I am working on a very similar idea, I to am using a worm drive to compensate for the 15 degree give in the flexible axle. Was this idea ever explored?

I am working on a very similar idea, I to am using a worm drive to compensate for the 15 degree give in the flexible axle. Was this idea ever explored?

I am working on a very similar idea, I to am using a worm drive to compensate for the 15 degree give in the flexible axle. Was this idea ever explored?

Great idea ! I hope there's not too much backlash. Definitely worth trying.

I liked this idea, and while I was at the hardware store I noticed an 11" flex shaft for a drill, not a dremel. It has absolutely no play between force applied on one end and force out the other, so seems absolutely suitable from that perspective. Unfortunately, one end is a hex socket like for a screwdriver bit, and the other a hex shaft, with a brilliant little gouge cut out for hobbing. But I can't figure out how I'd mount a gear on it or anything...

Check out S.S. White Technologies for the flexible shafts. http://www.sswhite.netwww.sswhite.net.

I have a spare off-brand dremel flex shaft I've been meaning to play around with, but I'm wondering about accuracy. I've noticed there is a hysteresis there too (not a term I would have thought to apply, but certainly appropriate). Specifically I've noticed that with the dremel spinning quickly the shaft end does not stop instantly with the dremel.

I'm interested in how this works out in practice. I was looking into the dremel flexible shafts for this purpose a couple weeks ago. What do you mean by "maybe a bit disproportional?"

the dremel ones are made to transmitt quite a bit of torque and are therefore not as felxible as the speedo ones are. The torque before the reduction should not be very high so there is no need for high torque shafts like the dremel ones are. THis is just what i think, did not test it jet..

Very interesting!

I wonder if we can print worm gear worms, or if the layer bumps will cause too much friction?

Maybe we need to design a planetary or harmonic gear speed reducer.

For your flexible shaft, beware: some are designed to transmit torque in only (or mainly) one direction (the other direction can unsplice the wires). I'd expect speedo cables to be in this category.
Thankfully though, reversing the filament to stop extrusion shouldn't require much torque.
Bicycle
brake cable might be enough with a very high reduction at the extruder.

Best of luck!

i thought of the direction problem of the speedo kable as well, theyr probabely only good for one direction.Good idea with the bicycle breaks, i think i will give them a try as well.

Whats nice about the worm-gear is that the axis between the gears are turned 90
° so the direction of the cable is to the top which would not be so with a planetary or a harmonic one. A big bevel gear probably would work as well.

flexible shaft driving the filament. Very interesting. What this setup, you could move the motor out of the makerbot, and have room for several extruders instead.

I thought of trying this myself but was concerned of backlash screwing with the accuracy of the motor.

For other people to get it, you might want to change the title to flexible drive shaft.

ok, changed it...

im not native english speaker which has some negativ effect on finding technicaly correct terms ;)

i just orderd a shaft for a speedo.. think i will give it a try...

That concept is well known by the name "Bowden Extruder" and is used by the MiniMendel for quite a while already.

its no bowden cable, its a flexible shaft. With this design the hobbed bolt which drives the filament is stimm located near the toolhead which should make the feeding more acurate