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J-Struder : 1.75mm Bowden Extruder For NEMA 17 Motor

by junaling Sep 8, 2018
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Nice design! May I suggest a description of the individual parts. With several versions and variants of some of the parts it it not always obvious which ones to use.

Yes for sure what do you have in mind, describing and naming these parts are a challenge to me, I just pick the first thing that comes to mind, also english is my second language, thanks :)

The names are fine I think but it would be helpful with a summarized list of the parts describing their function and what alternative/version to use in what situation. It's such a nice design and I think I've grasped it pretty well now as I have printed two sets but I felt I had to read through the comments and check the stls closely to figure out which parts I should use.

This is no show stopper. Just a suggestion to make it easier for newcomers :-)

Thanks for all your work!

Thanks for the feedback

Firstly I wanted to say well done on the design, it's beautiful and fits like a glove. I'll never put the stock assembly back on since this one looks great and puts some serious bite onto my filament.

One word of caution to anyone building this is be careful with your pneumatic fitting for the Bowden tube. I was careful with threading it in, it was fine for most of one print then it pushed the fitting right out. So what I did was machined my self a little steel insert, heated it up and pushed it into my part so my fitting is threaded into steel.
A captive nut would be another good idea.

Just my thoughts. Like I said, wonderful design! I've been chatting this up with other creality users already.

Thanks for the feedback, I'm working on the next version of this thing which will eliminate the need for the pneumatic fitting, just waiting for some parts to arrive, stay tuned !

Threading a metric M4 hex nut directly onto the PTFE tube seem mighty strong.

Just published the guide using bowden collet, no more screwing ! I've got more than 20 hours printing with them and and they're holding on just fine.


Can you post the .STEP of the latest version?

v3 guide step files uploaded

Thanks a lot !

Can you also post the base? I want to make a remix

base v2 step files uploaded


Printed guide_bowden_adj_v3_fixed in PLA 0.16 layer height but the hole for PC4-M6 coupler is too large.
The coupler came out so easily.
Can you make one with lower tolerances ?


The file for your part are buggy.
You did the STL wrong with intercepting geometry.
I've attached the tensionner.
You can clearly see the problem.
When i slice it in simplify3D it give me a weak part because of this.

for people who have problem when slicing on simplify 3D.
Just check the box "Merge all outline into a single solid model" in advanced tab of your Simplify3D settings.

Thanks, no problem for me on freebie slicers (cura, ideamaker, slic3r pe etc.), glad you find a way to get to work it in simplify 3d I don't have one so not able to test

THIS. clap IS. clap SO. clap FUCING. clap GOOD. thank you.

I love this extruder but I have a problem with the guides (only with the new ones with threads for the adj. screw).
2 parts are missing (sliced with simplify3d 4.1)
Could you please check the files.
The error is also shown in the preview on thingiverse.(Please have a look at the 2 pictures I have added).
I prefer simplify3d because I have profiles which I have tuned for my printer in a heated enclosure during the last year.
Thank you very much...

I've fixed the problem by checking "Merge all outline into a single solid model" in advanced tab

Checkout the latest files ending in _fixed, fixed them via netfabb. The old files slice fine for me in cura, slic3r pe and ideamaker, I don't have simplify3d but it seems very picky and maybe does not have a built in stl repair functionality.

Hope it works for you. Cheers

Question about the hardware parts listed, can you use the stock Ender 3 extruder hardware for this? i.e. screws, gears, spring etc...

You can reuse the gear, bearing, spring and (maybe) 2 of the m3 10mm screws, the rest you have to source separately.

Gotcha, thanks! :)

Months later and I'm here to let you know it's still going strong on my printer, though I need a reprint on a part because I cracked it (my fault). People should be doing this in PLA, I don't get why some are having so many issues with the print. EDIT: You added a tensioner screw to the spring? Nice Engineering, but I honestly am OK with the original, seems to work great, but nice job regardless.

Thanks for the update, mines also still going strong as well, I print mostly ABS so mine has always been ABS

My only issue is that when loading filament it doesn't always go straight into the inner hole (the second hole after the wheel, check the pic) and I have to poke around until I can get it all the way down into the hotend. I ended up using a needle-nose file to enlarge it a bit. Maybe if that insert was cone shaped to better guide the filament, but I'm nitpicking, perhaps keep it in mind if you're ever to tweak the design.

I've always had this problem with all the extruders I've used, including this one. What works for me is to cut/trim the tip of the filament at an angle, as steep as possible, then ensure that the filament is as straight as possible before loading. I've heard some people use sharpeners to make the filament tip pointed, I've never tried this technique before and what kind of sharpener they use :)

I think I'll design the world's most over engineered sharpener :)

LOL, i'll stick to my snips.

guide bowden adj v3 seems to be broken

Edit: Added pictures

What slicer ?

Edit: added pictures as sliced in cura and slicer pe

It doesn't slice correctly for me in simplify 3d

  • Posted with 3D Geeks Thingiverse Browser App

What is the minimum height of the stepper shaft to fit this?

See here for NEMA 17 stepper motor specs : https://reprap.org/wiki/NEMA_17_Stepper_motor

Shaft length seems to be standard at 24mm

I know the specs for the standard NEMA 17, but if not all the 24mm is required for this then I will make at order on shorter shaft with the company I'm talking with...

Best extruder i have tried so far. Good job.

The latest version of this with the adjustable tension is brilliant. Printed in PLA and it is working great. The only issue I have had so far is the PC4-M6 coupler came out of the threads. I've used some thread locker and it's holding so far. The option to use a captive nut (assuming M6 size?) would be great if the thread length would allow?

  • Posted with 3D Geeks Thingiverse Browser App

You get what you pay for with this thing. So much wasted time and filament I can't get back.

What do you want to say with this? :-D Is this good or bad? xD

Hi, awesome Model but I'm struggling with it. whenever I try to screw in the Bowden coupler, the plastic cracks before it is fully screwed in. Printed at 100% infill in PETG at 0.15m layer height. Am I doing something wrong? Thx in advance!

You can use a tap to help with the threading beforehand or just heat the connector or an m6 bolt and use it to thread the hole

Another person was previously encountering the same problem as you, solution is somewhere in the comments.

But anyway, PETG can become brittle if you have the fan/blower on when printing, try again with the fan off.

Thx! I'll try and get back to you!

Which version will the best to run TPU and other without changing for stock?

base is at version 1 and guides at version 2, so there's just one version right now which should also work for flexible filaments.

I put this together and installed it on my Ender 3 PRO this evening, it's chugging away flawlessly on a 8 hour print at the moment. Thanks for the excellent design, I'll post up a pic tomorrow. Managed to use some of my stock hardware but unfortunately socket head caps were not available locally, went to a Philips head and it worked out. I have zero slippage compared to the stock feeder.

So I assume I should print for stock guide Bowden or guide fitting or guide direct what's is a difference?

print the base, then choose what guide you want, for bowden you can cut a piece of the bowden tube and insert it on the feed end, see pictures as example, for fitting you can have fittings at both end to attach the tubes, for direct you feed the filament directly.

The run is so small it doesn't make much difference, I used a small piece on the feeder side just to keep it from bending at a weird angle (I'm using a direct feeder, filament comes from a vertical path.)

Hi! Any advise to insert the spring in the extruder? I can't insert my sprig of my ender 3 :(
Another question, what is the purpose of the 6mm bolt? After put it, I don't notice any difference.

Just press it against one side until you can push it in. The 6mm bolt is to lock the guide in place, there's a total of about ~0.4 mm gap that may or may not be significant to affect your retraction. Try it out without using the bolt if you feel there's no effect you can ignore it

I absolutely love this. It worked for me perfectly right off the printer with most of my stock hardware. One thing I am not a fan of is screwing threads into plastic. I have a design that I'm developing to replace brass push connectors and I would like to make a version attached to this extruder. I've tried making the mesh a solid but it is fighting me. Would you be willing to share a step file or the source file if it is Fusion 360. i understand if that is not something you are wanting to do.

step files for guides uploaded

Thank you thank you!

theshort, any progress on your brass connect version?

Slow, but I think it is going to work well. I am going to create a version with an M6 thread as well if people want it to replace screw in push connectors.

Here is what I've got. It takes three 3/16 x 5/16 rubber o rings and clamps down on the Bowden tube. I want to try rubber hose as well to see how well it clamps.


theshort. looking good so far. looking forward to the final version.

I had no luck printing with TPU 20D. IMO space around the gear and near holes for filament should be smaller.

Comments deleted.

Im having problem that I dont have enough tension on the tensioner. ANy idea how to fix?
Tried longer and stronger spring, not working because there is stopper on the tensioner thingy.
Notice that I print over 100mm/s
With stock parts, no problems at all.
With this, I dont even hear the motor skipping because it does not skip, just grinds the filament because not enough tension.

Make sure you remove the knob after inserting the filament also don't tighten the lock bolt until you remove the knob. Do you have any pictures ?

attached a picture. in the picture the knob is still in place. but ofc when I loaded filament, I removed it.

Remove the knob and take a picture top view. Also what's the diameter of your gear ?

Looks good to me, just that the spring looks like it's not properly seated

Its longer spring than stock. I tried also stock spring. Still stops feeding filament and starts grinding it. I manually push 1mm and it starts feesing it again for some time. With stock parts no problems . Just wanted something cooler looking

For the longer spring, probably there's to much tension that it's crushing your filament try guide_bowden_v2_plus4mm it's 4mm longer, as for the stock mine works fine

There is not enoguh tension. It wont even bite the filament.

Hi! Would this fit also the Ender 3 Extruder?

It should, see this make : https://www.thingiverse.com/make:569222

J-Struder : 1.75mm Bowden Extruder For NEMA 17 Motor

Thank you for your quick reply.

Does anyone has problem when change the filament , i cannot take it off , and i unlock the tube for that

I think I would add spring tension regulation. Something like that

Thanks for that.

Finally I do not hear this worrying skipping mottor noise.

I hated that.

Will be trying flex material as well.

Also. I printed with pla (no enclosure for me :D) and threaded my nut to a plastic. I am a bit suspicious about strenght of that thread, especially because it got a bit sqewed (but its not binding a material). Do you think it might be an issue?

As long as there's no crack it should be pretty strong, you can try to further screw the fitting in a bit at a time to straighten it, but before doing that print an extra just in case :)

I printed 2 copies at once, but dont worry I have at least 2 extra extruders lying around anyway so yeah :D

BTW, can I get .step files for all parts? Best in one file. I know you put out a step file for a guide part but would be nice to have all of it.

Comments deleted.

Hello. I broke guide_bowden 3 times when screw fitting. May be you will little increase gap for fitting?
p/s Sorry for my English.

Please post picture, also what material are you using ?

PETG. Infill 50%, 80%, 100%. Layer height - 0.1 mm

Try at thicker layer height at 0.12 or 0.16mm also lower your fan speed to 50 percent or turn it off petg becomes brittle with too much cooling for me I use abs at 0.16mm layer height 80 percent infill

Thanks! 0.16mm, 80% infill, no cooolng is OK!
But I think that is to much extruder gear pressure to the filament.

So no more cracking?

yes, no more cracking.

That's good, I don't think 0.16mm at 80% infill will be an issue with the extruder. Also set your layer height to multiples of 0.04mm, 0.1 is 2.5 steps that could cause missed micro steps (the 0.5 portion of it)

it's not a program (S3D) settings problem. I think in that model construction is too much gear pressure to filament. In that case my extruder motor start working loud. In the original extruder is OK (not to loud).
In picture some question.

Ok I see what you mean, so you feel that the spring is compressing the filament too much and that the motor is working much harder. I don't have such issue on mine. What's the diameter of your gear, could it be that it's rubbing against the guide?

Yeah the tube will touch the rod, I don't have any issues with it, I use a longer tube and bend it out a bit

I think the problem is that I turned the extruder motor on 90 deg. (but not sure). Gear is stock. Dia is about 11.1 mm. Gear is not touching the guide.
I will try turn back extruder motor later (after 8 h) and let you know.

Here's how it look like on mine

Not a big difference... May be in future you'll make a little lower spring compressing?

I've uploaded guide_bowden_v2_plus4mm.stl, this is 4mm longer than the original which in effect will compress the spring less, please try and let me know if it works better, cheers.

Hello. Tested some time guide_bowden_v2_plus4mm. Have to say that not enougth spring compression for good printing.
Better use original guide!

good to know, yeah better have more than less otherwise the gear won't bite into the filament and will cause the filament to slip :)

I printed and used new version of guide. Working well.
But guide dimension need to match spring length.

Sorry I don't get what you mean, is it still tight or loose? The spring should still have some compression otherwise the gear won't bite into the filament.

I have 2 types of springs: 1st - small and 2nd - long. For the long version of guide with small spring don't get normal compression but with long spring is all OK.

Ah ok, I hope the original guide works for your small spring, obviously the fixed nature of the guides will not fit all spring lenght

Comments deleted.

I do have a question, how necessary is it to lock that locking bolt when loading/unloading filament, have you found that the spring pressure is not sufficient?

It might not be necessary but I still use it. There's about a 0.2mm gap on either side and during retractions you will see the guide move which may or may not affect the flow rate after retraction. The original design did not have the stabilizer, the lock bolt is carried over from it

Thanks for the reply and insight...

So great and simple design, thanks for the stl !
It is almost perfect also to print flex filament, but the main gear diameter is too large for my 10.5mm gear.
A version with a smaller diameter for the gear would fit it even better, leaving no exit area for the flex.

Thanks for the feedback, I designed this for my existing 11.15mm diameter gear. I'll see if I can still further optimize the gaps or maybe create a separate version for smaller gears

May be you are ok to share your source design file, or PM me ? I could adapt "guide_bowden_v1" to my own gear..

I've attached the step file for guide_bowden_v1

Thanks for the file ! I made a version for my 11mm gear, will test it soon.


This should work pretty neatly :D

J-struder flex mod