Rollerstruder: filament feeder / driver / extruder

by MoonCactus, published

Rollerstruder: filament feeder / driver / extruder by MoonCactus Apr 12, 2013
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This is the filament driver I used (together with my hobbed bolt) sucessfully on my Ultimaker for the last 10 months (and this is PLA!)
It was designed originally for 3 mm but it would work alike with 1.75 mm as it boils down to how to the hobbed bolt (I ran it successfully with ~2 mm trimmer line filament)
This thing is in progress, though it is currently revision 5.3: I just should stop spending days on it since it is extremely reliable (much more than what I had stock).
It is written with openscad and it is fully parametric (incuding height, average thickness, bearing diameters...). It also prints quickly (2-3 hours), and almost in one piece (2mm walls and 30% infill is enough as it features internal dedicated structures).
People may be interested in the unusual features I think it has. Check my blog for the details.


Update: scad file 5.3b fixes the main body height that was 2mm too small for the hinge screw (and idler M8 screw).
Update the "simpleclamp_xxx" files are useful in case you want to use a blind rivet nut (recommended) or a push fit to hold your bowden tube, check the appropriate file name (else unneeded).
Check the detailed instructions on my blog here http://betterprinter.blogspot.fr/2013/04/rollerstruder-filament-feeder-driver.html
The bowden tube clamp derives from the ingenious Owen's design, which itself uses Aubenc's Knurled surface finish and screw libraries. Expect these to be dropped in the next revision though, because I will favor a simpler and more compact bowden clamp thing.
Crappy and useless video here with 3mm wood filament: http://www.youtube.com/watch?v=oWVvKtcfUrI and 2.4mm crappy trimmer line http://www.youtube.com/watch?v=VQk3jsIkmz0

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How to you keep the nut on the hobbed bolt from unscrewing? I'm thinking of either thread locker or a second nut tightened down on the first.

Most extruder designs have the gear turning right so it screws into the hobbed bolt, similar to how a left hand thread on a circular saw works.

Actually, no extruder wants anything to tighten or loosen with time anyway... so yes, use a counter screw :)
I use the big black 3-petal one show here http://www.thingiverse.com/thing:70494

Oh nooo, another customizable thumb wheel / knob / screw / whatever :D

Yup, slapping another nut over the existing one did the trick, though I didn't bother printing a thumb wheel for it, I just used a normal wrench.

I've been using a Wade style cold end for a while, and I have to say, using the head of the bolt works so much better than the shaft. Now my issue is the 1.75mm filament buckling in the cold end when I push it too far haha. No more filament grinding for me.

I did find it easier to go with the traditional tap thread hobbing method. I tried your method too, but I found that it just didn't get the filament to drive at a totally consistent rate, and no matter what I do, I can't get the threaded bolt to grind filament anyway.

I also added herringbone gears. I find they're quieter, they auto-center themselves, and they put less axial thrust on the motor shaft.

Thanks for making a great design!

Looks like a really nice design. Do you have a list of hardware you used for this? I couldn't find it on your instructions. I'm planning on using 2 or 3 (depending on the diamond hotend is released) of them on a printer I'm designing, and it would make ordering parts much easier. Thanks!

Easily the best change I made to my Ultimaker was this feeder. The bolt took some time to make and a printed jig, but totally worth IMO to do this. My printer is actually reliable for the first time ever

Wow nice feedback, thanks! :) I think that the hobbed bolt + bearing does it all in fact, I have tried variations of the extruder but got same results (=useless variants). Now the other design I really enjoy at each print is the Z adjuster http://www.thingiverse.com/thing:126716 !

YAZA - yet another Z switch adjuster (Ultimaker)

Nice feeder. I'm trying to set it up on my printer with 1.75mm filament but i can't keep the bowden tubing fixed while retracting... neither am i able ti adjust the .scad files -> no top level geometry :(

If you are using rollerclamp.scad, make sure to uncomment the proper lines in the "DRAW PARTS" section (around line 53). Just uncomment them one by one to generate the different parts of the system.

And of course you will have to change the value of "bowdenplug_bowden_diam" to your proper dimensions.
(now, you probably will have to play a bit with other settings (conicity etc), as I never checked 1.75mm).

I think I just found another solution, using your ultimaker customizable replacement (http://www.thingiverse.com/thing:25636) and I scaled the clamp bodey to 95% in x and y direction.
Will give your advice a try now.
Edit: Yeah it works now ;)

Owen's Bowden clamp: tightening cone improvement (parametric + inner rings)

Great design! Is there a way to modify it to use on Prusa i2 (no bowden)?

Well, the mount would have to be re-designed at least, but otherwise probably.
Sadly, I do not know the geometrical constraints of a prusa to tell reliably.
You could just use a 2-3 cm piece of bowden at the top of the feeder as a guide.

Just had this printed on a UM2 and none of the parts fit right at all. Like the screw part doesn't screw into each other, That part doesn't even slide into main body and none of the nuts fit into there correct places! :( Checked the size printed and the size it should be and its all correct The printer is fine and calibrated. I know theres some tweeking and fiddling to do but this is waaaay over the top. Just spent over 3 hours trying to get the quick change to fit. Still doesn't fit and I don't see any way of making the screw part fit together! Sizing is all off. :(

huh looks like you have some real issues. Weird b/c a few people made some and never reported all this. I cannot tell much because it always was fine with me (well, the stepper positioning side screws are a bit messy). Are you sure you are at 100% size when printing? not over-extruding? If I understand well, the "screw part" is the bowden attachment base, right? You may have to sand a bit but it certainly fits the negative shape as it is just programmed with some tolerance (I mean, no way I could have it made bigger than its slot, the sizes are shared between the files if I remember well). Also check you are not overheating. What kind of filament are you using?

Everything seems fine. No over extruding as the support material came off very easily. Just plain old black PLA was used. Really not sure what the issues are. I'm going to work on getting them to fit Its just odd that some bits are a bit wonky! I love the design and the idea so really want to get it to work! :)

What size filament is this designed for?

The picture shows a hobbed bolts made for 3 mm filament, but I think it would run well with smaller filament also.
At worst, the hobbed bolt would have to be made more carefully. I ran the above with ~2 mm nylon trimmer line without no issue.

Would it be possible for you to make a version of this which uses the Pneumatic fittings?
The body could simply have a 9.5mm hole in place of the cone/holder/slot, you just screw the fitting in.
If only I could use Openscad... :(

Hi! Check the "simpleclamp_pneufit_9p5.stl" file that I just uploaded! :)
Actually a long time ago I secured the bowden with a blind rivet nut, it is more efficient than anything else (ie. http://www.tridimake.com/2012/10/robust-bowden-attachment-with-blind.html)http://www.tridimake.com/2012/.... I should add some pictures later! That's why there is another version of the small square clamp for a nlind rivet (and a thrid one to be drilled at will).

Cool thanks, ill check it out!

I have to say I am a bit frustrated at the moment, I have just printed the main body and while it looks great, it is unusable.
I printed in Taulman Nylon but the design is not rigid enough.
As soon as any forces are applied the body flexes near the stepper motor, and the gears become misaligned.
My feeling is that you should make the entire thing less intricate, and more solid.
The body lacks strength at the point between the stepper and the big gear/idler section. This is where it needs the most reinforcement because any flex results in gear problems.
I also find the idler hinge problematic. Because one side holds the idle, and the other holds nothing, it wants to twist.
Good to hear your thoughts on this. :)

Ouch, better avoid Nylon at all for the body as it is too flexible indeed (I will update the doc!). I used PLA and recommend it! Actually, my design was also to reduce the overall printing time, so I removed most of the useless material. Nylon may be good only for the gears (esp. the small gear). Same issue with the hinge: even in PLA it twists a bit and I need to address in a revision indeed (even though it was not an issue for me, I d'ont like it)

Haha sorry, I hope that didn't sound like a completely negative attack..
The concept is cool, but as you say, Nylon is not the right material. :)
I think I will try and reinforce this one with some Aluminium, just to save printing it again.
The hobbed bolt and grooved idler were both very easy to make, and I already had a spare set of Herringbone Gears, so its all good!

No, no, no problem :) There are really great forces in play in the feeder, so flex will happen if it can!
By printing the feeder with PLA I was able to use a low infill also (less material and less time), but I had to add the funny heat barrier made of PTFE tubing. For a while I even pushed the stepper power so much (to try and print at fast as I could) that I had to add a small fan on the stepper... And now that it is there I keep it :p
Keep in touch & post pics when you are done :)

Will this extruder be for 1.75 or for 3mm filament? I am at the moment going to switch to 1.75mm and am looking for a suitable extruder.

I do think it would work with 1.75mm (I tried a ~2 mm trimmer line as is)
I would recommend either to print a conic clamp suited to your smaller bowden (easy + standalone change in the openscad diameters in the source code), or to insert a smaller inner PTFE tube within the existing 3mm tube.
In any case, I think that the feeder itself requires no changes.

Ok, I printed it twice now, here are my comments so far:

  1. Using 0.2mm layer height it is printable. I still needed a scalpel to separate the idler from the extruder. I don't understand why want to print it assembled!? It doesn't make anything easier and it makes it impossible for most of us printing a simple replacement part because the idler broke.
    On the other side of the part you used this wonderful and fully functional method of using thin walls to build the support structure for these mounting ribs. Why not using it on the idler as well? It would make the process much much easier! Please separate the two parts - I'll happily print it again.

  2. The idler is mounted using three ribs. I'd like to suggest using one big one in the middle on the extruder side and two strong ones on the idler. That should reduce the torsion of the idler when tightening it.

  3. You didn't mention the gears you are using. I'm assuming you are using the standard prusa extruder gears - they seem to fit.
  4. I'd also like to suggest to use more tolerances everywhere. For example, the screws barely fit. And the rollercap-nut needs a lot of torque because there is no good way of reshaping a printed screw. Also, the socket of the rollercap-body is too wide. It should be reduced in size.

Thanks for reading, great idea! But I'm looking forward to an updated and easier to print version!
Best regards and: MOST INTERESTING BLOG!

here you go. separated. hope this helps.
I personally printed the whole thing from the original moon's file, then broke the arm. Separated the arm, and printed it. Then cleaned both parts with scalpel and merged them together. This first print is currently on my printer.
You can try to print those two parts separated, but i'm not quite sure if the loops will come out fine. In any case you can treat the errors with scalpel or sandpaper.

Rollerstruder: filament feeder by MoonCactus ( Separated )

Thanks for taking the time to upload & help others ! :)

First of all, thanks a lot for your feedback, that's a pleasure :)

1) did you try the trick of inserting the idler axis screw, and then force it open with a large screwdriver as I mention in my blog? I printed at least 5 or 6 versions of the rollerstruder but never got issues wit h"too" sticky idler (ie. never broke something, even though it was hard a few time to break the bonds)... still I agree this is probably the weakest point in the design. At the time I designed it, it was also a proof of concept for me, as I wanted to try if I could design a one-in-all driver (movable parts printed altogether)... You are right that it defeats the purpose because if it breaks it ruins the whole thing :( I am not sure I really like the thin walls to support the jaws for the other side, b/c it then depends partly on the slicer... cura hate(d) too thin walls and discarded them. An dtoo thick walls are just a pain to remove afterwards. But it makes the print possible anyhow, so...

2) I tried what you said, but found out it was more robust with many small ribs than with 3... can't really explain why though... Anyhow the idle sucks and would better be redesigned with, eg. a lever to release it more easily as it happens on other driver designs

3) yes, these are the stock gears of the stock ultimaker, you can check and find replacements in my other designs on thingiverse if you need

4) actually I had hard times with the stepper tuning screws indeed. The nuts were really hard to put in place, and heating is never a good practice (I melted too much of plastic on one of them)... I wanted a very tight hole for the idler roller bearing, and you can either tap the thread with an appropriate tool if you have it, or play forth/backwards quickly while screwing to benefit from friction heat. Once in place there is really no need to remove this screw anyway.

All in all to agree that I need to upgrade of this design, and also to redo the idler arms completely I think... I have quite a few ideas already but it was no easy so far to get the motivation given that my version behaved really well for the last 6 months! Hope you'll get the same results, and yes, I will try to upgrade this thing soon :)

thanks again for this in-depth review!

Jeremie, what retraction settings you use?

Do you mean the value I used to print this part or the value I set using this extruder later on?

I don't remember and it is not really dependent on the extruder. I have a bigger bowden tube (check my blog) which adds some freeplay, so I should be using bigger values. Also some material (eg. Nylon) require a bigger retraction.
In fact I use something like 3.5 mm at 28 mm/s, which is on the ow side... The thing is it also depends on the hot end (a highly colled all-metal hot end does not like long retractions as it "freezes" the filament within, which may cause issue when resuming...)

Kind of a non-answer, sorry ;)

Try not to over-extrude in any case, this is the major thing for this thing! I must design and post an update since more people get interested in the rollerstruder and I should make it easier (and I have some more ideas since...)

thanks for the answer:)

Hm, using 0.25mm there is no seperation between the last flange of the idler and the extruder. IMHO 0.1mm-0.2mm layer is rather optimistic. But I really like the design, so I'm trying to print it at the moment and seperate the layers using a cutter knife and force...

Thanks! If you screw the 3 mm hinge bolt as I show on my blog you should be able to apply a pretty high force. It should break on the weakest point... Sorry for the inconvenience and keep an eye on the derivative as I will probably tackle this one day or another!

Strange how whenever i am looking for an ultimaker upgrade I end up staring at a solution by MoonCactus.
I was always wondering if it would make sense to add a second extruder bolt to get more contact area and therefore more grip on the filament (i imagine a grinding bolt like a wheel during burning out).

This design features a second drive bolt but is really complex and difficult to assemble (also work in progress):

Yours looks way simpler and less bulky. Congrats....

non-grinding feeder for Ultimaker
by jalr

Thank you! Such comments let me feel I am not spending too much time designing them ;)
The driver you mention easily wins in the steampunk category though !

Unfortunately this model appears full of mesh errors to KISSlicer. Is there any way to have openSCAD generate better meshes?

Oh I never had one single issue with Cura for 1.5 years and hundred of revisions -- and I always take great caution to generate proper manifold CSG geometries for added epsilons so that the primitive do overlap a tiny bit. Now, I believe this is still possible. May be you'd better run it through netfabb cloud service? Sorry for the issues :s

Apparently there are a lot of zero-area triangles and degenerate edges which is what openscad puts in and KISSlicer does not like. Netfabb does nothing to fix it unfortunately. It's not your fault, it's just openscad being silly.
That said I have printed the object (out of abs!) and besides some stray filament in places it looks fine. Haven't had a chance to test it out yet, still working on making your drive bolt and bearing.

I printed your design and parts not divided. give to part separately.

Do you mean the hinge is locked/welded? You may have to force a bit to "un-weld" the idler arm hinge (see http://www.tridimake.com/2013/04/rollerstruder-filament-feeder-driver.html)http://www.tridimake.com/2013/.... Don't forget the screw before you force it open!
Now, 0.2mm layer thickness should be OK, but make sure not to over-extrude else it will be harder to unlock. You could print down a bit, say 0.18mm.
If all this fails, you may tweak the openscad source code increase the gap, though you'd get a less robust part at the end. The variable is "print_layer_th" at the beginning of the scad source code: you may set it to 0.3 for example, but double check how it looks (still, it would probably not impact something elsewhere).
It would be difficult to print separately given how the hinge is made (interlaced), but not impossible. Actuallty I made it this way so that it is more robust and a single-part print ;)
Hope it helps

In your first video, I see you are printing nylon. Is that a sheet of MDF on the print bed? How well does it work? (I'd rather not chase after Garolite LE in the right size)

Yep, trimming line: you'll find a detailed explanation on my blog here: http://www.tridimake.com/2013/04/3D-printing-with-cheap-trimmer-line.htmlhttp://www.tridimake.com/2013/...

It is called masonite/isorel according to the country (a kind of hardboard or fiberboard). Nylon like cellulose fibers more than what I could try so far (including MDF)

Thanks, I'm now reading your blog!

Looks awesome. I may try this on my future rostock.