Slugstruder 1.0 - lightweight flexible shaft extruder

by goaran, published

Slugstruder 1.0 - lightweight flexible shaft extruder by goaran Jan 4, 2012
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This is a lightweight flexible shaft extruder, that i designed for highspeed printing.
The idea was to keep the stepper away from the moving parts so not too much mass has to be accelerated without the disadvantages of a bowden-extruder. (i posted a early idea of ot here http://www.thingiverse.com/thing:6653)
Another idea was to replace the passive idler bearing with a active second hobbed-thing as well as using gears with a bigger diameter to garanty better grip when extruding at high speed. Also the distance between the gears and the nozzle is relativel short for more direct drive.
The extreuder consists of two parts, each of which can rotate around the worm-axis. this way the distance between the worm and the gears always stays the same, but the pressure for driving the filament can be adjusted.
The name slugstruder is because of two reasons. in germany we call wormgears something like snail-gears (Schneckengetriebe) and slugs are something like snails as well. Another reason is that i like brainslugs ;)

The flex-shaft i will use is one from a motorbike - speedo. These have one prefered direction to rotatet, so be sure to pick one that has the same rotation as the worm gear that u're using. If the torque for thsi one is not enough i will try a dremel like one later.

This is a work in progress.
The parts i added are only to take a look at the design and do not work till now (the spring tensioner thing and some holes are still missing)
also the connection to the flexshaft is missing..
The gears are some standard parts that should be available everywhere.
The bigger holes are teardrop shaped to improve printability, but i could also supply some files with round holes.

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Over the past six weeks I have been sketching a very similar design. Bought some tools and parts that turned out to be unsuitable. Have you built one yet?

hi there! looks great!

i made a dual weel extuder some time ago... instead of gears, i used cutter blades for the actual transport... did work nicely but on one point i lost my inducement since the regular ultimaker extuder got fixed and uses less material:)

for the snaledrive i used a grub skrew for wood...

there's the doku with a pdf if you wanna have a look... :http://luzern.fablab.ch/new-ultimaker-extruderhttp://luzern.fablab.ch/new-ul...

i would add some light round groove in the filament driving wheels. this way it stay centered in the mechanism.

you may also have to shrink the distance where the filament travels with no guidance.. maybe adding PFA tube pieces with tapered holes that go up and down right next to the driving wheels.

More! More! I'm quite excited to see this design come to life as I expect it could very well be the future with the advantages of a bowden without the problems most likely.

Any thoughts on including a rotary encoder to be able to reduce the effects of hysteresis in the cable?

I'd suggest there's value even when using a stepper motor (although the encoder would also open up the possibility of using other motors for the extruder pump)

the encoder is a good idea, maybee ill try that if there is a problem with the hysteresis.. , what would be even better than an encoder on the gear is an encoder that is on a passiv idle. this one would even measuere correctly if there is some slippage and it could be used to detect extruder-jams and do some emergency shoutdown whatever.

Not shutdown but a proper pause (raise the head, cool down, resume on button press)

this is my design. The rotary encoder detects stalls like with a blocked nozzle,... and allows the operator to intervene without loosing the print.

I could be wrong, but adding an idler to the 'dual hobbed' setup starts to undermine the weight benefits of this design. That said... being able to measure filament motion directly would, in theory, allow feedstock jams to be recoverable without having to restart a print. A huge plus for larger prints

Its funny how all designs seem to be the same. Your new machine your making look more or less the same as mine http://www.thingiverse.com/thing:15442http://www.thingiverse.com/thi....

So this design is very interesting indeed. Especially if the Drive cable can be decoupled with a solenoid or something so that it can drive multiple heads.

Doombot of DOOM!

indeed my new bot looks kind of yours, and i've seen some more of those as well. I am also thinking about how to add multiple extruders to the machine in some elegenat way. the easiest is to mount op to 4 of them around the moving thing where the axis cross. here eighter 4 flexshafts or some switchable gear could work. but then there would still be all those wormgears that dont do anything most of the time. there has to be something better.... ;)

I'm working on a triple bowden type extruder with a single orifice hot end; my goal is to produce on-the-fly color changes and mixing. I'll set up a thingiverse page when I have more stuff done.

I had a similar idea but had a more complex gear train:


The advantage of running the worm drive axis horizontally is you can adjust the gap between the pinch wheels without trouble, over a relatively wide range.

Double Pinch Extruder idea

I love the twin-hobbed-thing idea :-D

In fact, it's something I've thinking about myself (from time to time) but never put it out of just thoughts yet O:-)

In order to prevent ooze you will need to reverse the direction of the feed. Your flex shaft will not have to work so hard to reverse, but it should be able to handle quite a bit of reversing...

i already tried the reverseing withe the speedoshaft and a wade extruder, and it worked there. A wade has about 5mm filament extrusion / turn, here it is about 2.5 or something so the torque is lower and it should work even better. but i think i will have to test the shaft for long term damage as well..

What bot and hot-end are you designing this for?

As you talk about a moving toolhead, I guess I would be Reprap Mendel, Darwin,, Huxley or a Repman but not a ToM or Cupcake CNC.

the printer i have at the moment is my cnc mill : http://robotik.dyyyh.de/reprap/rr3.JPGhttp://robotik.dyyyh.de/reprap...

more infor here: http://robotik.dyyyh.de/http://robotik.dyyyh.de/

the problem with that one is that it is really slow and loud.

that is why i started to build a new one http://robotik.dyyyh.de/reprap/frame_01.jpghttp://robotik.dyyyh.de/reprap... (will be published when it is finished) and the extruder is for that one, but it should work with a mendel or whatever too, when you adjust the mounting interface. The hotend will be a wade one with 10mm peek insulator fist, but i think ill replace that later as well..