Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

Gunstruder : Belt friction extruder Cold-end

by andreasL, published

Gunstruder : Belt friction extruder Cold-end by andreasL Jan 6, 2016
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This is my own vision of the Vaeder extruder

More comming soon !!! This is a work in progress, sorry for the lack of documentation

udp 09/03/2016
changed almost every parts.
works now with 18mm height pulleys ( muche common one)
aded a 8mm version of the drive pulley -> better use 8mm axis to get the best pullex allignment. you can find some 20th gt2 pulleys with 8mm bore anywhere on the internet.
this version works fine on 3 prototypes I've made.
Let me know if you have any question or difficulty making this thing work !

(Zapperke ( http://www.thingiverse.com/Zapperke/about ) made a 3mm version, you shall be able to use it in the next release if he gives us his files :)

I've also aded a new motor support whitch fits more motors and printers

udp 08/01/2016

  • Replaced "chassis2" part, witch was an older version. sorry about that.
  • Replaces "outlet" part, same reason. Added 3 version to adapt the pressfit you already have ( M5 / M6 / M8 )

Use std skateboard bearings
std 20th gt2 pulley
200 mm / 100 teeth gt2 belts

M3 x50 screws 5
M3 x15 screws
M3 8 headless screws 2
M3 nuts * 7

bearing x4

nema 17 motor

"Bearing spools" must be printed at about 102% to fit on the bearings.

First prototype is working well, this is an upgraded version.
bug may occure, please let me know.

Since every printer is different, you may have trouble with tensionning the belt.
If the belt is to loose, lightly scale up the " quicklock" part !

BOM and french forum : http://talk.smartfri.odns.fr/index.php?topic=794.0


Holes should be re-drilled. Use your drill turning backward, so you just melt the plastic instead off scraping it off.

Be carefull when re-drilling the inlet part.

Be carefull to reduce the curant on your pollolu, so the motor doesn't heat to much. If the motor gets to hot, the chassis part will bend because of the primary belt tension. -> baaaaad (see picture)

stp/mm are around 425.

How I Designed This

Sources are solidworks files, I'll share it if asked.

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2 years of use: the best extruder ever. Zero problem, no maintenance, a f***ing strong torque, no grinding filament, no noise.

I don't understand why this type of coldend are not more common.

Not the only one using belts and same remarks as for the others. Far too complex, heavy, fragile and as usual, no specification.

It's by far the best extruder design I've tried.
Thanks for sharing @andreasL.

Love the design, but still no assembly instructions?


Well, with the images and the orignal files ( see comment below) you should be able to do the job. This is not a final design, but it works fine as it is.
If yon don't feel confident enouth with DIY project, you might encounter some difficulties making this design work.
Give it a try, and don't get discouraged ;) i'll try to answer any question if you get some troubles.

I think that this is a great idea, if you would please senda link to the source code that would be very helpful. I think that the walls of the idler should be thicker and taller I also think that there should be a more stable holder of the main wheel that has teh channel in it. I love the idea of a belt driven extruder the torque and quietness are very important to me. I think it is possible that there are too many parts and the assembly is not easy to take apart and put back together. This idea has legs, if we can just manipulate the files. Do you have a github link or something?

Hi, have my Gunstruder up and running and first observation is a much more consistent extrusion compared to my current extruder. What doesn't work is that the inner belt runs of the pullies after some time. Therefore I had to revert to my original hobbed bolt based extruder.
Does someone recognize this behaviour and how did you handle it?

This happened to me too, i made gunstruder and it was faster and cleaner and no "noise" in the prints and then I printed and it went all berserk. I am reprinting a copy in pet plus, I think that it is possible that you have to make sure you assemble it tightly, I think that I messed up the assembly of the main gear to the pulley gear inside as well. I think that I bent that assembly. I think that I would blame myself for the user error, but this is a good design I think over all, far superior production I do not like not being able to see the filament enter the neck of the bowden coupler. Going to make another in petG and I think that will add ot the overall rigidity and will add to the robustness of the finished product.

I really like this extruder, so quiet no grinding etc...
But I can't get it to work properly! It doesn't extruder the filament consitantly and sometimes it bends the filament and comes out the sides of the pulleys etc...
The belts are pretty tight.

I see you have a smartrapcore as well! ^^
What spool holder is that you're using in the photo?

I've finally managed to print all the parts for this and assemble it - and let me just say wow ... I am really impressed by the design. The pictures really don't do this extruder justice, there's some really nice work gone into it. I've figured out how it fits together but it really needs some more detailed step-by-step instructions.

I'm still waiting on the remaining parts from AE, and am really looking forward to putting it all to a real test. The one problem I see immediately is that there is absolutely no mounting options on the frame - this really needs to be fixed for me, so I'll undoubtedly be remixing it with something suitable for my Kossel XL once I figure out the best way to mount it. Thanks for the design @andreasL, love your original work on innovating the V-Struder, and I really look forward to seeing what you next come up with in the future.

I've finally managed to get my first working gunstruder up and running - and as I expected, it is so far working brilliantly.

Some initial feedback:

  1. My feed belt was way too loose. I had to resize the outside diameter of the "608 bearing spool" up by about 2.5mm in order to get enough tension on the belt to hold the filament in place, since there is no other way to adjust the tension. I still don't think it's tight enough, so I may tweak it (or the main drive gear) some more.

  2. I really don't like the included mounting plate (on the stepper) and it's no use on a 2020 beam system anyway. I'm currently tweaking the frame to add some more suitable mounting points - as there is literally nowhere else to mount it from. At the moment it's cable tied to my spool holder (and my filament is on the floor).

  3. This thing is gnarly ... with belts out in the open like that and two young children around, I'm eventually going to have to add some finger protection in somehow.

  4. The side plates are thick ... really thick ... at 8mm, seem far more meaty than they need to be, and requiring much longer bolts than necessary. Since I'm still waiting for the longer bolts, I tweaked the frame to countersink the bolt heads and nuts. This allowed the use of 40mm M3 screws instead of 50mm.

  5. I used at 16-tooth pulley on my stepper, for a bit more drive force, just because I had both lying around. I ended up with 545 steps/mm @ 1/32.

Once I can fix these issues, I know I'm going to completely love this extruder. Thanks again.

Incidentally I would be interested in how much pull strength people have managed to get - including in particular @andreasL. Knowing what sort of pull strength it should have will give me a good idea how much tension I should be aiming for on the primary drive pulley. At the moment I'm just guessing.

Hello , thank you very much for your feedback and perseverance !
I haven't measured the pull strength.

Have some nice prints ;)

Please share your modifications !

Thanks a lot for the files! I can read and handle them. I will replace some M3 axis by 8 mm. rods. As soon as I have them ready I will upload them for you. wkr Henk

Does it have to be exactly 100 teeth belt? I have one that's 101 teeth (lol...). Will it be too loose?

it will probably be to loose... but try it aniway ? It doen't cost that much to buy one in china if it doen't fit... ;)

i got a question:
What kind of belt did you use?
Since there is very little friction for me between the Filament and the belt. It Slips through if the cold end has to push hard. (starting at about 1 kg pushing force or something)
Any ideas on that?
Thanks in advance :)

I use some standard rubbet gt2 belt from a chinese suplyer (see "BOM" link in description)
Maybe the beld isn't tensioned enouth ? (sounds like)
If it is that, you can try to reprint the lever scaled at 101% (only in its lenght) or more, depending on how much your belt is loose now.

Thanks for sharing this extruder. I already bought 3 Vaeder-extruders but I had already different problems and I don't like the way of mounting it.
Can you please share the Solid Works files, so I can adjust the mounting.
Thanks in advance.

has someone printed the herringbone gears for thisone ?:)

Why would you use some noisy gears when you can enjoy the silence of a belt ? :)

i only have one belt and im inpacient ;)

Please be patient, it will be worth it!
I dont know why this extruder isn't way more popular...
Retraction is great without grinding filament!

As Zapperke said, be patient :)

"I dont know why this extruder isn't way more popular.."
Probably because I didn't do my job... and didn't exposed it on reprap forums.... feel free to talk about it everywhere if you like my extruder ! :) :)

How many steps does the extruder motor need to be adjusted to in the MArlin/Arduino image?

Dependibg on your motor
0.9 °/spt about 430 step /mm
1.9°/stp about 215 step / mm

Precisely adjust by itarations to get best results .


any plans on making a version for 3mm filament?

I'm testing with 3mm... Only changed 2 parts. It seems to work well with abs. Also printed with hips, and got nice results. I was affraid the filament would crack, but it doesn't. With pla i used a filament oiler , but think that won't be a good idea with belt driven extruders. To be continued!

not sure the 3mm filament will be flexible enouth.

Well, I think it's fair to say that a Ultimaker is a good printer , and it originaly uses, like it comes out of the box, 2,85 mm filament with a bowden system ( see here https://ultimaker.com/en/products/ultimaker-2-plus/specifications at "materials" ) , so .....why not trying it?
I already have it running with a wade extruder, but I wanted to try this extruder if it is so much better...

this is some really great news ! Would you mind explaining what you changed ? ( which parts ? )
I may then release a 3mm version !

Thancks again for experimenting !

Love this extruder.
No more grinding the filament.
I used M5 all thread for the axle, but gonna change this to normal rod because the pulley came loose .
Gonna keep experimenting with this design.

I m glad it works ans you like it !

Let me know if you have any suggestion !

Thanks for the design! I gave it a test build, and have a few comments:

  1. The pulleys I have with 8mm bore do not fit with the belt path centered -- the body needs to be slightly wider.
  2. Would be good to put a inset arrow on the side to show the filament direction. Had to track down a photo somewhere else to figure it out.
  3. I'm not sure how the filament is supposed to thread to the output tube (it's inaccessible), and which exact connector you used that allows the PFTE through? I have used 1/8" NPT that allow 4mm PFTE through, but not any with ~M6.
  4. The belt is slack with the 5mm bore pulley I have on hand. I suspect your drive pulley is slightly higher tooth count than mine -- would be good to post the specs (and the source). The idler farthest away from the motor could be printed slightly larger to compensate, but not much. Maybe include a second hole for a slightly longer total belt path (if the standoff pieces were separate)?

A quick test on a filament I have handy (Afinia PLA/PC) is that it doesn't have the holding power of a mk7 drive gear, but I suspect it works better for flexi filament. Some experimentation will be required to figure out which gets eaten first if there's a jam -- the filament or the belt.

hello, thanks for giving it a try !

1 : sorry about that, my pulleys are 16mm long and standards one sounds to be 18mm. You can download the Lyscanthropes zip file witch contain the part for 18mm pulleys.

2 : ok, sorry about it. i was thincking that naming parts "inlet" and "outlet was enouth. I'll add this feature in the next release.

3 : The ptfe doent go through, I have a litle piece of tube under de connector. I will add a 1/8" NPT outlet part if needed ?
But as said, it doesn't need to go through

4 : I'm using 20th pulleys ( it shoult be written somewhere i thinck)
again, your tensioning probleme younld have been resolved in the zip file, as i have moved the holes you are mensioning.

If your belt isn't realy well tensioned it won't work fine. but once you get it working, it got a loooot of friction :)

Bravo, c'est in design vraiment interessant !

Comments deleted.

Nice idea to use a second belt for the drive from the motor, very compact. Almost looks like it could be used for direct drive.

The belt drive also make it realy quiet, compared to any gear drived extruder.

Direct drive is possible ( from what i've tested un the cad ) but would make it les compact.

I would love a direct-drive version, especially with a 16-tooth pulley. Any plans to release the models for that?

Not for now, sorry , but remind me un one or 2 weeks ! ( exams month right now... )

Very interesting design! Could you post somes pictures of the one you build? Could you also post a step file of the assembled extruder?

Thks, Yeah I'm uploadingit right now ;)

looks awesome ! I can't wait to test it !
Still have to get the parts ....

When you'll get the parts, the design should be stable :)