J-Max_Bowden Belt Extruder (feeder) V1.0

by J-Max May 22, 2016
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i really like your method of belt tensioning. BUT since it's printed. how well does it hold up after a while of running. does it slowly slip back out of tension?

I bought some 160mm belts and have extras if someone wants they can message me. I had to order 10.

Hi J-Max,
Thank you for sharing your extruder design. I have been using it for over a year and I am very pleased with it. It is a very clever design and obviously well thought out. I couldn't find the MK7 gear that met your specifications. The ones I could find had a smaller inner diameter for the groove of only 10 to 10.2 mm and were 13 mm tall. Because of the smaller diameter, the springs did not provide enough clamping pressure to keep the filament from slipping. I modified the idler clamp to replace the springs with a screw mechanism that provides adjustable tension on the filament. I also put a 'groove' in the body to accept the taller MK7 gear.

I also found that the crank did not have enough purchase for me to crank easily. I designed a crank extension that has a longer lever arm and provides twice the purchase. It mounts easily on the existing pulley by using a slightly longer M5 bolt.

I would like to share my designs with others that might find them useful, but it doesn't appear that your license permits it.

I found some MK7 gears that have a 10.54mm inner diameter and meet all the other specs. reprap.me has them.

Thanks, that is good to know. Meanwhile, J-Max has generously added my redesigned clamp that allow the extruder to work with the smaller inner diameter MK7 gear and provides positive clamping pressure. He has also include the crank extension.

Hi Philip,

I'm very glad you enjoyed that extruder. I think you did a great job with the upgrades and you're right, it might be interesting for someone. I believe there's a lot of junk on thingiverse and finding versions and remixes can be tricky. To find all about a design in a single main page is a good thing. If you agree, I can post your upgrades here, in the main page for the extruder. Of course, I will credit you in the instructions and on the pictures and I will write something about your version specifications. Message me and I will give you my email.


Sorry could you redesign body for 200mm belt? And 13x4x5 bearing instead MF105. Thank you.
Or if you`ll give me file in Solid or Fusion I may made it myself.

Hi again Denis. Unfortunately, I don't own the right software to make changes any more. This is an old file. I was working on the V2, but as you can find a Tevo copy of the E3D's Titan extruder for about 10 bucks, there's no need actually to design and print a custom extruder. The Tevo Titan is just perfect and inexpensive. That's what I recommend nowadays.


Do you think the Titan is better or equal to your design.

I made a remix but your licence have no derivatives. If you change it i`ll add body remix for 200mm belt

Thank you Denis for your work. Your body version is published and you are credited in the description. :)

No problem, send the files and I will add those here while crediting you for the remix.

Hi. I see equal parts in archive what the difference?

Hi Denis. Except the body part with the 2020 slot into it, it's pretty the same. Some parts have some visible marking, and some the making is hidden. Choose the one you like most.

Hello J-Max,
first of all thank you for developing that nice extruder!
May i ask you what's the source for the right mk7 gear in europe, i'm having trouble finding it.
Thank you,

If you are still interested in this check reprap.me for their MK7 Gear.

Hi Andrea,

I used to buy mine in China. But I believe you may trust reprapworld.com.
They sale a pretty good filament under their brand called REAL, if you want to compensate shipping costs.


Hi J-Max.

I got handy a 200mm (100teeth) closed loop belts. What big pulley size I should use to make it working in your extruder body?


Well, I'm afraid this would not work because of the shaft distance. The middle tensioning distance between the shaft is +-37mm on my extruder body. You should need a too big pulley which will collision with the 16T pulley. Through, you won't have enough teeth in mesh and the belt will jump over teeth under the torque. You should make a remix of my extruder body with the same pulleys and a medium shaft distance of +-58mm.

Yeah. This is what I thought. I also find that I don't have the flanged bearings. So it will end up in redesign to suit my own hardware :)

No problem mate !

Yup - I did it. I set the pulleys 58mm apart as proposed. In general the body is 10mm longer and 10mm taller comparing to your slender design. And I also made the body a little bit wider due to bigger 625 bearings. It can also accept the longer MK7 gear. Because of this the clamp had to be widened as well. The clearance around the filament openings is made very tight - so you may even try to use flexible filament w/o the risk for escaping to the sides. The only original part I left is your pulley - that I left with the original marking for recognition of your original design.

I must admit it prints very well with small amount of support.
I also find that if I print it in ABS the long floor tends to break. I glued it back with acetone.
The only thing I may consider changing is the 64t pulley - I bet it can be designed to be printed with no support - the belt holding flanges could be made 45 deg. Right now they are impossible to print in ABS w/o support. I will load it when I get home. I will also add the print in place M10 thread because currently I am having trouble inserting the bowden fitting.

Nice work !

Hi J-Max!
Wow. C'est magnifique ! (and, no, I didn't pay attention in French class as a kid. I often joke my only French is to say croissant at Dunkin' Donuts...) But it is a beautiful language!

What an amazing piece of art / engineering!

I spent hours looking for the right replacement extruder for my Monoprice Select v2.1 upgrade to bowden / E3D clone setup.

The moment I saw yours I shouted EUREKA! I knew instantly that a real engineer had built it. Please excuse the fanboy gushing, but I was looking at all of these half baked, hackneyed, poorly designed and / or executed solutions and was disparaging of finding a properly designed (AND tested!) one. Seeing yours was like finding fresh air at that point.

I'm looking forward to building this, ordering the parts today. I'm not looking forward to setting up the proper extrusion rate, I'm not sure how much of a pain this Monoprice will be flashing the new values, I'm off to watch Tom's video.

One quick question - Any suggestions on the plastic to use? I have some nylon, but my current hotend can't handle the temp.
PETG? I figure I want to use a more slippery plastic, no?

All the Best, and thanks again,

Hi Bob,

Many thanks for your comment. I'm not graduated in mechanical studies. This is just testing/redo process, with the help of few friends for the benchmarking.

I dunno if Nylon would fit because the extruder needs to be stiff and Nylon uses to be soft. I believe any regular plastic will suit : PLA, ABS, PETG... Mine are mostly PLA and ABS. I use ABS when the extruder stands into an enclosure. If your enclosure can raise near 60°C, you'd rather using ABS or any thermal resistant thermoplastic. Otherwise, PLA and PETG works great. Don't worry about slippery, because the infeed tube is 2.4mm and the outfeed tube is 2mm and is pretty short.

If you notice any resistance into the outfeed tube, it's probably about stringing or printer calibration. But don't worry, use a 2mm drill bit (5/64" or 3/32" will be ok) and drill through the out in reverse mode. Reverse mode is always a god idea when drilling plastic, because it works, it do not dig too fast, it won't overheat the plastic, and the diameter will be more accurate. ;)

Happy printing !

Drill plastic backward ... I KNEW that but forgot it, thanks! My "plastics" trick is: I worked in a place where we had to screw together and apart assemblies with sharp steel screws into plastic bosses. Sometimes 10 times! As you can guess they stripped a lot ...! We learned to always run the screws slowly backwards in an already threaded hole, feel it "click" at the start of the threads, then go forward slowly. If tight, STOP and try again, if smooth, you're in the original thread pattern! I do it without thought now.

Extruder : Printed in PETG, but got real dimensional problems, what I printed wasn't what was on the PC. Plus, I was having other issues with the machine so it was a major fight. I didn't have the right screws, on and on.

I ordered and got two 80T belts, and they vanished somehow, so I had to use an 82T I had, but that, of course was too loose, so I had to make an idler mounted on one of the motor screws ,,, real Rube Goldberg stuff, you'd love it. THEN I had to sand down the door since it was not allowing the bearing to put enough pressure on the filament.

Oh- I ordered some MK7 drive gears, as you had on the list, but they were too tall for the opening (gears were 13mm) so I had to rework the thing in Fusion 360, which I'm a n00b at. Oh- the nut holes for the two screws that spring load the door are M4 in the housing but the screws are M3, I fixed that in Fusion (took me three days LOL! Learning experience!!). Then the print had slicing errors (my fault in Fusion I know now what to do).

The MK7 gear would NOT grip, I used the gear that came with my Monoprice Maker Select (MK8??) which has much sharper teeth. The motor shaft was too short, I had to use a coupler I had from a Z axis upgrade and an aluminum shaft.. On & on.

It's working now, but I'm limping along on a far from ideal print since the "fixed in Fusion" one wouldn't print right.

Now, the GOOD news ... I LOVE IT!! It is working fairly well, and the problems are few, all related to the lousy print. I'm going to start over in Fusion 360, I need to change the mounting, re-fix the 4mm holes, and re-enlarge the hole for the gear for the 13MM gears I have (which includes thickening the bottom plate) and re-print it now that I have the machine dialed in. I'm going to try it in colorFabb nGen which is strong as hell and prints pretty easily (if a bit stringy).

The thumbwheel is awesome, so easy to get filament down the tube. I smile every time I use it. This is my 1st Bowden, and I'm really liking the upgrade. Getting all the mass of the extruder off the carriage is great too. Thanks again!

BTW - if you would be willing to share the CAD file, it would be great, if not I'll live with the mesh.
All the Best, PuterPro


Wow, that's a real adventure you're telling here ! I'm happy it finally worked right for you. I'm sorry, I can't post the CAD files because I don't own the software any more. I'm working on a V2 actually on another software, which I believe will be better and maintenance free.

My two cents about problems you encountered. You probably had over extrusion on your first print. The door and the parts must fit just right, we did a lot of prototypes and testings to get it right. The MK7 gear you get is probably a fake one. I warn about it in the description section, as there's a lot of fake MK7 on the market with hazardous dimensions. The MK8 is much smaller and would probably won't be usable at all. The pressure problems you had should comes also from the wrong hobbed gear. It's a known problem, and probably the main one with that extruder : you need the good parts. That's a point that can't be fixed. You could eventually use shorter belts (78t and maybe 76t) but larger ones are too long I'm afraid, event with a 20T motor pulley.

As it's your first bowden extruder, try to cut the bowden tube as short as possible. Happy printing !

Well, it IS a hobby for me, so frustrating as it may be, it's fun overcoming the obstacles! Keeps my brain flexible. No problem on the CAD files.

Thanks for the tip on the gears, yes it was definitely over extrusion, my E Steps were way off from the factory, I'm calibrated in now, the X & Y were over stepping too, a "perfect storm". I saw what you mean when I searched for a MK7, the dimensions, if you could find them, were all over the map. Don't know for sure what came with my Monoprice "MK8" was a guess. It's 40 straight sharp deep teeth. Have you a source for a genuine MK7?

I'll find the 80T belts, if not, order some more. Any advantage to the shorter ones, besides the obvious "it's tighter"? I'm sorta proud of my idler, it was such a pain in the a** to get going, but works very well now, LOL.

Managed to keep my Bowden to ~45cm, pretty short, although, I hoped to used a filament feed from a airtight box similar to https://www.thingiverse.com/thing:1371130. That's not the exact one, but the concepts the same, multiple rolls with interchangeable Bowden tubes. Do you think there'll be a torque issue, or grinding from the increased friction of the tubes?

Very much looking forward to V2, any guesses on ETA, are you 5% or 80%? Officially reporting as a Volunteer Beta tester, Sir! LOL!
Thanks for the fast reply, have a great week, and HURRY UP on v2, LOL!!! {Wink} Feel free to PM me.

Airtight Filament Box Part
by marimba

I don't have any dead line for the V2 and it's not easy to announce a release date. I guess it's hurry vs quality. Even when you're into beta test phase, problems can take time to find a right solution. Thank you for beta tester proposal. I will surely contact you in time.

To me, no problem of torque with a airtight box. The main problem does not comes from friction but from spool weight/resistance. Make sure the spool can roll freely (bearings ?).

To me 45cm is pretty long for a bowden. You can probably install your extruder in another area to maintain the bowden tube to a 25cm or less distance. The good spot depends of your printer type. On a Prusa i3 alike you can mount it on the middle top of the frame, on a Tarantula, you can mount it directly on the X rail.

In the description I described the good dimensions/features of the genuine MK7 : "/!\ Pay attention to buy a proper MK7 hobbed gear for 1.75mm filaments. The universal MK7 for both 1.75 and 3mm filament may not suit perfectly. The perfect dimensions are : 5mm bore ; 11mm tall ; 12mm (or 1/2") in diameter ; a 3mm wide hobbed groove centered at 3mm from the top, with an inner diameter of the grove of 11mm (10.5mm is still acceptable). Some cheap MK7 measures 12mm in height but you still can file or grind it a few to make it suit."

There's no advantage to use a shorter belt. You will have a shorter tensioning area. Otherwise, as long as the belt fits, there's no difference on the settings.


OK! Keep me in mind for beta.

Spools: i plan on four 608 bearings per spool like this: https://www.thingiverse.com/thing:2047554 should be pretty low friction, I'm concerned about friction in tube from box to inlet of extruder ...BTW: Suggestion - might consider 4mm push in fitting on inlet as option ... See why you can't predict v2?

Extruder: I considered top mid-frame mount, but went to side mound on top of control box. On the Monoprice Maker Select they top mount the spool, I wanted to reduce the sway that caused on rhythmic prints, and there are mounting holes for the holder on the control box. The filament travels only three inches straight into the extruder, but a bit longer to the hotend (the 46mm). Spool is setup to be super low fiction with a hack. I'll ponder a shorter path, this one was no drilling ...

Mk7: Mine was 13mm clone, no grinding possible, I considered it. I was hoping you had a good source for the right one.
RTFM. OK. LOL!! I've got the damn thing on the desk in front of me ... :-) Now you want me to READ it? A bit unreasonable don't you think?

Belt: Thought so, thx. Current one is nicely tensioned: no slipping, but not stressing the bearings either.

TUSH - The Ultimate Spool Holder

The V2 development is surrounded by other projects and real life responsibilities. Otherwise there's a lot of principles to try out, and Ican't get right at first attempts. The V1 took a study of 5 months plus a long beta process with various solutions to try out. The overall realization time was more than a year. When you will be into the beta phase with us, you will probably have a better idea of the hazardous time required.

I take in consideration the 4mm inlet for external PTFE tube in possible option. We did not implement it on the V1 because the small distance between the spool and the extruder was not considered as a factor, even if you use a dry box. The filament can't get moisture in a so short distance, and also because it's running. On the other hand, if your spool (or dry box) is placed in an appropriate place you probably don't need any incoming bowden tube. Anyways, if you want an incoming tube, PTFE is low friction. There's at least a 0.25mm clearance within the bowden tube, you don't have to be afraid of any issue. The Tush spool support uses a very low friction principle, it will be ok. We use the same kind of spool holders, which can be loaded/unloaded in no time.

I got good sources for the MK7 here in europe. I'm affraid shipping costs will be huge.

RTFM : well, makers write documentation to duck the issue risk as low as possible. I consider you're safer Reading That Fancy Manual ;)

"other projects and real life responsibilities" - Yeah, know you mean, there was NO attempt at pressure, just idle curiosity. I see a lot of me in you from the little contact we've had, a similar view on things.I certainly know the design process, have done many Betas over the years.

PTFE inlet: Just a thought, I think you have a point about the short exposure, I'm sure straight to the extruder from the box is something I can work out, simplicity is usually a good thing.
MK7 - Yeah, gear $5US, shipping $40US, seen that one before! I'll chase one down here. Thx.
RTFM - Smartass. Love it. When my Wife heard I'D been told to RTFM she couldn't stop laughing. We have a FIRM rule in this house that if a new item is brought in, the manual MUST be read cover to cover before you get to play with it! Have had that rule for 37 years! Been a long time since someone said it to me, LOL!
I'll stop bugging you for now, stay in touch, my new Friend!

No problem mate, see you on V2 Beta process !

the remix-ed 2020-mounted body in the file collection is mirrored and does not fit with the provided clamp and idler!

You're right. It's an add-on to the original design. You need to mirror both the clamp and idler. I write a warning about that in the instructions.

Grate work j-max!
sorry to see the trolls in the remix version
keep up the good work!

Oh, thank you jens !
Don't worry, whatever the haters do, I sleep well and I keep on going ;)

I posted this on my make, but I'll post it here to make sure you see it.

In order to make this easy for me to use with my D-bot, I remixed the body to have a convenient mount for attaching to 2020 aluminum v-slot rail. If you are interested in either allowing this to go up as a remix, or using it yourself in some way, just let me know.

Having the 2020 rail mount on this extruder will likely make it usable by quite a few more people who build printers with this kind of aluminum rails.



Actually, this extruder was meant to be mounted on 2020 (or 3030) profiles using the two holes located on the motor plate. Of course it works on the vertical stiles of a frame. Your mount is interesting if you want to mount it on a horizontal rail. Nice work !

Hi. I was about to post my remix of this with the 2020 extrusion mount, when I noticed that you have this under the Creative Commons No Derivatives license.

I will respect that and not post my remix, unless you wish to allow it. Or, if you are interested, I can send you my STL file for the remixed extruder body and let you do with it what you will. Let me know your wishes.

Hi. The day I posted that extruder a (well known) hater posted in minutes a remix just with my name out of it, without any mention about the source. Sadly I decided to move this one into no derivative to avoid further hater bashing... You know, It would be much smarter to ask for a "hidden name" version, which I did later anyways. On another hand, in my humble opinion, Thingiverse is a real mess and It's probably a good idea to minimize the location of the sources. Expecially because there's so much wrong versions of good things. Anything I post is tested so you can print it with confidence. I will be proud to print yours to check if it prints with no issue (this would work) and post it here with mention of your name as a fair contributor.

Hi Seth, I printed your remix version of the body. It fits tight to the OpenBuilds 2020 profiles. Otherhand, it don't fit to 2020 module 6 (Mitsumi alike) or module 5 (Motedis alike). I added your great remix to the thing's folder. Your photos shows pretty well the differences and the mounting options. Thanks a lot for your kindness and your work. :)

Thanks! I did have to use a file and do a little fitting of the 2020 slots to make them go on easily, but I decided it was better to need a small amount of work and then fit really well than be too loose and not have a solid mounting. Also, remixing using only the STL file wasn't easy, so once I had the mounts printed and fitted to my 2020 rails, I didn't want to go back to tweak it.

I've done a handful of prints now with the extruders mounted to my D-bot, and so far it's working great.

One comment: the way I've got my extruders mounted, I can't see the small hole where I feed the filament into it while changing filaments. I'll probably end up having to drill a 4mm hole there and fit a small piece of ptfe tube so it's easy for me to feed in new filament. Maybe you could raise up that little cone a little around the hole to make it easy to find the hole just feeling it with the fingertips.

Hi Seth,

It's good to ear these extruders works great for you. I add a word about possible file work on the OpenBuild 2020 body part.

I keep in mind for the V2.0 an extended insert hole that can fits a 4mm PTFE tube. But I must wait for a major improvement to release the next version.

Merci pour ce partage.
J'ai commencé à le construire. J'attends des pièces pour le terminer.
Il ira sur une imprimante D-Bot avec une carte de contrôle MKS SBase.

Très bon choix la MKS Sbase ! Si tu ne connais pas encore, tu verras, c'est une super carte ;)

Il a l'air vraiment bien, de plus un des gros atout c'est la rapidité pour enlever/remettre du filament, beau boulot !

Merci l'ami ! Tes encouragements font vraiment plaisir :D

I liked your design so much I would have bought you a cup of coffee if your account had been set up to accept tips. I have already printed the parts and am just waiting for bearings, belt, mk7 gear and the push connector. Thanks for sharing.

Thank you Howard, your comment was greatly appreciated.
Pay attention to buy a real MK7 for 1.75mm filament.
Universal MK7 for 3mm and 1.75mm filament may not be perfectly suitable.
I post this precision on the BOM.
You guy have a great day ;)

Yeah. I thought I had a mk7 gear. It turned out to be a mk8 gear. So I ordered a couple of mk7 gears for 1.75 filament. I have a itty bitty belted extruder on my Makerfarm I3v that works awesomely. This extruder you designed will be going on my hypercube that I am in the process of building.

That's a cool printer ! My extruder is probably a good choice for this purpose. I wish you will love it as much as you love your Itty Bitty's (which is a good one too). Don't forget to keep the bowden tube as short as possible because you don't want a long retraction.

I just asked this on the instructables site, but I'll ask it here too: is it really necessary to use a minimum 37mm stepper motor? I bought two 20mm short steppers for the two extruders I'm building. These were steppers that were recommended as usable for the E3D Titan extruder, which is a geared extruder. The reduction from the gearing reduces how much torque is required.

I'll order new steppers if you say you've tested shorter steppers and they just don't have enough torque even with the 4:1 reduction from the pulleys, but if these will be fine, I'd rather have the compact steppers in my setup.

Hi Rexipus, it's good to see you there too.

Well, I can't say about the E3D's, but we may consider the Titan is a light weight extruder, so it should be interesting in direct drive applications. In this purpose, the motor should be light weight too. Through, I don't know if the Titan's small gears can stand a lot of torque.

With smaller motors, we (the beta testers and I) experienced unconsistency of filament deposit on faster printers or low melting temperature filaments. Filaments with fibers also need extra torque. We did not wanted a setup at minimal, so a comfortable security margin was applied to print properly and cover any possible issue. With at last a 37mm long motor you can be confident, whatever your setup or settings : silent motor drivers (which provide less torque), overheating on long prints, hard core delta printer's speed, and so on. Just like we did : install it and forget it :)

Probably you can make it work with 20mm motors, but stay in reasonable expectations because you won't have extra torque to stand any situation. Stick to 16 microsteps, and don't print fast with exotic filaments. As I told you on Instructable : on my setups, I use 17HS8401 motors (48mm). There's no huge difference on the price tag and the motor will never be to blame.

Thanks again! I ended up getting two 40mm steppers for the two extruders I'm building. I'd be done with the extruders, actually, but I discovered that the two toothed gears I had on hand were actually mk7 types, and were too wide to fit into the holes. So the extruders won't be finished until I get the mk8 gears on Monday.

I can hardly wait to use these extruders that you've designed. I really like the simple design that still seems well thought out and complete. I also am quite looking forward to the 4:1 gear ratio, and glad that it's using belts rather than directly through gears.

Hi Rexipus,

Thank you ! With 40mm steppers, you can be confident. The 4:1 ratio makes it pretty powerful to push some 1.75mm filament (you can't stop it by hand). The belt system have 3 interesting points : 1. it's more precise than gears. 2. you can adjust the tension easily. 3. It's really quiet, you just ear the motor, and with silent drivers (TMC2100 ; LV8729) you won't ear anything but fans.

MK8 gear's diameter is too small for my extruder (9mm instead of 11mm). That's why I mentioned you need a proper MK7 gear for 1.75mm filament. The perfect dimensions are : 5mm bore ; 11mm tall ; 12mm (or 1/2") in diameter ; a 3mm wide hobbed groove centered at 3mm from the top, with an inner diameter of the grove of 11mm (10.5mm is still acceptable). I upgrade the description with this dimensions. Some cheap MK7 measures 12mm in height but you still can file or grind it a bit to make it suit.

Wow, ok, I was wrong completely about the gear. My mk7 gears were 13mm long. I just spent like two hours with a file and my dremel tool grinding around 2mm of steel off. I had to grind at both ends of each gear in order for the tooth slot to line up with where the filament goes through that space. What a pain in the butt!

It's done now, and I'm finishing up building these two extruders. I'm hoping to have my D-bot more or less complete this evening.

Hi Rexipus,

Ok, you get rid of that bad MK7. Lot of work (sorry about that), but it's all done now. I saw actually about 20 extruder built, and there were only one issue, and it was about another wrong MK7. The next of the build should be a breeze. Good luck !

I finished the two extruders I was making, except for the belt. It turns out I'd ordered the wrong belts, so it'll be a few days till these have the correct belts.

I'm thinking of printing out a new extruder that is mirrored so I can put two of them together, head to head, and keep the filament tubes very close to each other. Thanks again for this design!

Hi Rexipus,

You're welcome mate ! I've seen your build, it's a nice work, especially for the one with the nylon pulley. It's good to know a 100t belt is way too long, even with the tensioning range. Printing a mirrored body for one of the extruders is a good idea, I must do this for my dual extrusion printer. Thank you very much for your feedback.

What are your steps per mm for the one in the video?

Hi Thomas,

Well, if I give you my settings, it may not be suitable for your printer. Extruder settings needs always first a calculation, followed by a proper calibration. The basic formula for e_steps_per_mm is = (motor_steps_per_rev x driver_microstep) x (big_gear_teeth / small_gear_teeth) / (hob_effective_diameter x pi)
As you can see the parameters may vary depending of your hardware and your driver settings.
If you're not confident with this procedure, you can follow Thomas Sanladerer's excellent guide : https://www.youtube.com/watch?v=YUPfBJz3I6Y

How well does this work for extruding flexibles? I know most people say to avoid flexibles in bowden extruders, but I'm one of those crazy ones! ;)

Hi kmenigoz,
The filament is guided just out of the hobbed gear, it's not going anywhere.
I managed to print flexible filaments with it. You should consider these three points :

  • keep the bowden tubing as short as possible
  • set the printing speed very slow
  • set the retractation speed low too.

Oh this won't be my first time using flexibles with bowden. Just love this extruder design, wondered if it would work! Thanks for your quick response!

Thank you mate, your comment is greatly appreciated ;)

Can you tell me what your settings were in Marlin for flow rate and steps


Hi teime. Well, there's no definitive steps per unit, because the exact settings depends of the diameter of the hobbed gear you own. Otherhand, your whole hardware may change the settings (angle of motor, microstepping, etc.) You need to refine yours steps per unit anyways. I recommend to follow a tutorial if you're not aware with the procedure. Thomas Salanderer's video tutorial cover the whole procedure : https://www.youtube.com/watch?v=YUPfBJz3I6Y

The result should be close of that formula : [(MotorStepsPerRevolutionDriverMicrosteping)(MotorPulley#Teeth/OutputPulley#Teeth]/(HobDiameter*Pi())

That Bowden belt extruder uses a 16 teeth for motor pulley, and a 64 teeth as output pulley. A perfect MK7 gear's diameter is 11mm.

I wish you a merry calibration time ;)

Hi J-Max!
Just a quick comment .. "A perfect MK7 gear's diameter is 11mm."
You might consider adding that to the BOM as a suggestion.

It wasn't in there, and I read this and said "OH!" LOL!

Also, the bore of 5mm for the standard NEMA stepper isn't specified for the 16 tooth pulley, might add it as a default value for us noobs. :-)

Bonjour, you've listed "1x 3/8" 4mm push in fitting (for bowden 4mm teflon tube)" but it actually needs a 1/8" BSP thread connector.

A 3/8" connector has a 16.8mm outside diameter.
A 1/8" connector has a 9.7mm outside diameter.

The hole for the connector in your model is approximately 9.5mm diameter.


Oh, sorry ! Thank you so much to reveal that mistake. As a metric guy, I've got some trouble with imperial measures, especially fractions. I change the BOM immediately. Thanks again !

Hey no problem! I'm a metric guy too so would have preferred it if it was an M6 size connector (PC4-M6). Much easier!

I ordered a 3/8" connector (PC4-03) and only realised it would be too big after printing out the part yesterday!

I'm so sorry about that ! I'll have a look to the PC4-M6, thank you for the part#

Petite critique objective, une petite traduction en français des détails seraient la bienvenue sachant que tu pratiques la langue de molière nativement.
Car pour les non anglophone ou anglophobe ton extrudeur peut être le meilleur du monde, il peut passer à coté d'utilisateurs potentiellement intéressés (dont moi évidement).
Sinon ça à l'air vraiment sympa good job!

Vous ici ? ;)

Au XXIe siècle, même les vieux comme moi parlent anglais. Attends, on m'appelle. Ah bon ? On m'aurait menti ? Bon, toutes mes excuses, il parait que non. Bon, je plaisante, je plaisante, mais j'ai bien pris note de ta judicieuse remarque. J'ai posté ça dans l'urgence, vu que j'avais annoncé sur le forum que je le publierai ce fameux week end, et j'ai tenu parole.

Toutefois, je n'ai pas oublié mes amis francophones car la vidéo Youtube est sous-titrée en français, et tu trouveras sur mon blog un petit article en bon français de chez nous : http://www.j-max.fr/?p=632

Il me reste pas mal de choses à compléter comme faire le film sur le montage. En attendant, je vais aussi rajouter le lien vers le Blog au début du descriptif.

A bientôt sur le forum.