Ninjaflex Geared Ultimaker 2 Feeder

This feeder is based on this work: present stage is the next planned concept of the feeder developed exchanging messages with the original designer.

3D printer parts and enhancements

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Although not as simple as other solutions, this feeder is not overcomplicated and is really reliable after you get the parts working right.

The principle is simple: you increase the contact surface with the filament, using rubber wheels to pinch the filament without crushing or bitting it, and alongside the use of gears guarantees that the parts always move in tandem.

As the name implies, you got to print two rubber-zigzag wheels on ninjaflex or similar rubberlike material, as they grip just right and fit tightly over the main gears.

The 2 main gears get 2 bearings each, and the 3rd gear gets one bearing. I've tried with less bearings but the gears tilted and didn't work so well. I've included cheap sources for the bearings.

The only mod you have to do to get this working is to set the steps per E setting of the UM2 to 237 using Pronterface or your software of choice (M92 E237 on Pronterface). You could skip drilling the holes for the two uppermost screws, but I'd strongly recommend you to drill because that extra contact point improves the reliability quite a bit.

I've also included the flipped body and cover, which is what you see in the pictures, but that involves cutting part of the left side body acrylic of the printer and also uploading new firmware to invert the extruder stepper motor direction (#define INVERT_E1_DIR true on Marlin's Configuration.h file)

I can remodel the body to use the stock bowden adapter if someone shows interest.

It is based in this design:

09-01-2015 - UPDATE: Added 3_body_bowden.stl model, so if you don't want to use the 1/8" fitting print this one. Haven't got a chance to test it, so please let me know thru the comments how it works.

Materials and methods

- 2g of Ninjaflex filament
- 4x M3 25mm Screws
- 7x M3 16mm Screws
- 4x M3 1.6mm Low-Profile Nuts
- 5x 3x8x4mm Bearings
- 1x 1/8" Straight Push PTFE tube In Pneumatic one-touch fitting
- 1x 1/8" tap drill bit
- 1x 5x16x8mm Metal Bearing (688-2RS, comes with original extruder)
- 1x 16x8mm Spring (comes with original extruder)

Bearings sources:



Issues are used to track todos, bugs or requests. To get started, you could create an issue.


Mini jeanjamesJeanJames added this to the swdesad collection ago
C64c1622c82244af69fb42ca56471696?default=blank&size=40Justin Otherguy added this to the Ulti collection ago
Mini sany0007calinb added this to the UM2 collection ago
Mini sany0007calinb commented ago

I just realized that I have some Polymaker Flex filament in my inventory that I've never even tried to print. It might be less slippery than my Makergeeks Flex filament, but I'm sure I'll still need to "chase" any flexible filament through my UMO Bowden tube with some stiff PLA. If the Polyflex doesn't have a slippery surface, it might be a good alternative to Ninjaflex for the wheels.

I definitely think I need this Ninjaflexwheel feeder for my UMO but I might make a new mod to my UMO first anyway--just to see how much it helps with flexible filament. I can drill the Bowden tube path much closer to the knurled drive bolt and push the Bowden deeper for less gap. On the other hand, it might not help much, because that path in the UMO feeder is already supporting the filament with a Delrin pressure foot on the back and a square channel in the wood frame on the other three sides, which fit the filament quite well. I even sprayed the wood path with Teflon dry lube, but I think my Maker Flex filament still hangs-up and kinks a little there.

I actually have two feeders for my UMO, because UM updated my original (OUMO? ;)) feeder to the Bertho (roller bearing) style shortly after I bought my UMO so UM sent the upgraded feeder with my kit at no charge. I also turned my own hobbed brass bolt in a fixture I made for my lathe. The hobbed brass actually grips a little better than the knurled UM design but, when the hobbed bolt grinds the filament all, the teeth immediately clog and it loses grip. On the other hand, the UM knurled design tends to be self-clearing when it slips. My Maker Flex doesn't tend to clog my hobbed bolt when it slips so I think a hobbed brass bolt works better than the UM knurling.

I found this discussion on the UM Google group about the UM2 stepper. Apparently UM shipped it with a 400 step (0.9 degree) motor:!topic/ultimaker/qCBoH9TX6z4

Joergen's link to an aftermarket replacement still works:

So it might be a U.S. sourced 400 step alternative to the motor you used, Diego (which is spec'ed as 1.8 degrees / 200 steps). On the other hand, I hope a 400 step motor can be driven by my old UMO hardware, requiring only a Marlin configuration change and re-build perhaps.

Factory UM2 parts (like the knurled sleeve that I'll need) are also available here in the U.S.:

I might also make a UMO adapter plate for this design and use the UMO gearing, which also affords me a manual method of advancing filament via the UMO "big wheel" (large gear). It would be easier to make the mods, if I had a .stp or .igs file, however, which my Geomagic 3D modelling software can read. (It can't read the latest Solidworks format). Lathe-turning a drive shaft that's 5mm on the end to replace the original UMO drive bolt/stud is not problem for me. The 5mm end would then drive the UM2 knurled sleeve. Other UMO modders might like to retain the UMO feeder stepper too.

19d39ad2524f70f581a4616d1469d58a?default=blank&size=40dmols commented ago

Hey Calinb,

So yes, the first gap from down up (knurled sleeve to the wheels) is failproof, never had a problem there in 1000+ hours of printing. The upper one needs improvements like I said, I just lack the time to do it atm.

I couldn't find your message, sorry, but you can mail me at mrdmolina at gmail dot com.



Mini sany0007calinb commented ago

Thanks for your prompt reply and information, Diego. Also thanks for the offer of the Ninjaflex wheels. I'd like to offer you something in trade for them, however. They will save me the trouble of a tricky print with my UMO feeder!

Yes--I noticed that gap you filled with a small piece of Bowden tube and wondered about it. I also pondered the gap between the knurled sleeve and the Ninjaflex wheels. I guess the gap between these two feeder "stages" is of no concern, because the Ninjaflex wheels pull the filament away from the knurled sleeve and keep it from kinking in the gap.

I sent you an email via the Youmagine site. Please let me know if that email doesn't work for you.



19d39ad2524f70f581a4616d1469d58a?default=blank&size=40dmols commented ago


I´ve built another UM2, and I´ve used these motors:

You´re right, the bearing needed is a 688-2RS (the one you indicated). I´ll correct the description above.

I never use retraction when printing with flexible filaments, have not gotten any consistency with retraction, doesn´t matter the feeder or filament. This extruder works well for flexible filaments, but can be modified to be excellent with a little piece of bowden tube (aprox. 8mm of it) from where the filament exits the gears and enters the connection to the bowden tube. I needed to print a 24 hours job with ninjaflex and the filament kept running out thru this space, and now with the bowden tube I make long prints with ninjaflex consistently.

I have spare ninjaflex wheels to spare, maybe we can arrange that I send you some, idk.

Let me know how it turns out.

All the best,


Mini sany0007calinb commented ago

I'd like to install this feeder on my UMO. I assume that this feeder works well for feeding flexible filament. I think I can print the flex gears in Ninjaflex on my UMO, but I'll have to print them by "chasing" the Ninjaflex down my Bowden tube with some nice and stiff PLA (and no retraction, of course). According to Cura,, a single flex gear requires only 16 cm of filament. My Bowden tube is much longer than 16 cm so it should work. (At least this method has worked for me with small Maker Flex (TPE) printed parts, but Maker Flex parts have a too much of a slippery surface to work well for a drive gear, I think).

I will need to buy a UM2 stepper motor, because I've heard the UMO motor does not have sufficient step resolution for a direct drive feeder setup. I'd like to find a stepper motor with a longer shaft so I can mount a hand wheel on the end of it too.

I will also need to buy a UM2 feed pressure bearing and knurled sleeve and setscrew. I think the spring from my UMO will work. The parts list here calls for a 8x5x3mm Metal Bearing but 8x5x3mm doesn't make sense. Can someone please confirm that the bearing is actually 8x16x5mm? According to the UM2 BOM on GItHub,, it is a 1021_Ball_Bearing_688-2RS:

and it is 8x16x5mm

A 8x16x5mm bearing should fit the bearing yoke and arm parts here.

Thanks for the help and I'll upload any additional parts that I design for a UMO application.

19d39ad2524f70f581a4616d1469d58a?default=blank&size=40dmols commented ago


Sure, I can run an export to another file format, do you have any preferences?

D Molina



82dbad8594d50472a2f7dfb82e6b972b?default=blank&size=40Andreas Strömberg commented ago


Could you please share the parts in an other format than STL?

I want to integrate an gearbox and printed push-fittings and to the parts that I have laying around. Converting STL just generated an headache for the computer and thus myself.

0713fc717563d0668167c27ade52f10c?default=blank&size=40Roy Prawira added this to the 3D Printer collection ago
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A5c0f84d51eb49dc910dd074c2b19dff?default=blank&size=40ChrissyP commented ago

best feeder I ever had. Thank you

A360349de7c1ca8052a0d98bbac72775?default=blank&size=40Marko Kukovec added this to the To Make collection ago
B58f03a2d2c73ca5ce3607b1a9064d22?default=blank&size=40cENz0R added this to the UM2 collection ago
5f381aaba20f4e9770b6b6cb88ba6d24?default=blank&size=40feuerwolf printed this ago
Carousel thumb 2016 10 18 09.52.47
Printed on:
Ultimaker 2
works very good
Fcb3469695c95a5e23c2429eaae67447?default=blank&size=40Adam Rękosiewicz added this to the mods collection ago
F6f223db729f67167a8b7499dcd7b4a1?default=blank&size=40Myp added this to the 1 collection ago
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8dd7c9def6c7f5fca5c4a2b768a83e59?default=blank&size=40Marrut commented ago


Is it possible to have the ipt, stl or igs files?



F0885862d8ed1feb3dff8107d22c879e?default=blank&size=40Garra commented ago

@dmols - Nevermind (prob printing in ABS would be fine) I'll adjust gears' inner diameter using sketchup. I think we can delete all the spammy comments below.

In essence my problem is that inner diameter of gears is too big and it causes a bit of backlash.

People be aware of that.

Also I used Ultimaker Flex-PLA which does not have much grip (like NinjaFlex) so I advise others to do not even try if You do not have soft and grippy filament.

19d39ad2524f70f581a4616d1469d58a?default=blank&size=40dmols commented ago

@Talon - I didn´t design the gears, that was inherited from another design (the link is at the top of this page), I made no mods to it, so can´t help you out on this one. Maybe your printer is not printing to spec? Or you could try printing in ABS? The moment you start to resize gears you need to mess with the whole design, which is doable but undesirable if you don´t wanna spend much time around it.

F0885862d8ed1feb3dff8107d22c879e?default=blank&size=40Garra commented ago

Sorry for spamming this one, but I tried assembling resized feeder onto my UM2 and there is too much space between motor shaft gear and other gear.

@dmols could You please post gears' source files, so I (and maybe others) could resize their IDs.

F0885862d8ed1feb3dff8107d22c879e?default=blank&size=40Garra commented ago

@dmols - I printed everything on 0.985 scale in PLA and now everything fits about right. Motor mounting is a bit difficult but I guess I'll be fine.

19d39ad2524f70f581a4616d1469d58a?default=blank&size=40dmols commented ago

@talon - I tried printing the gears with ABS, the problem was it expands near the bottom and the gears become uneven. Lately I've been using Carbon Fiber PLA, printing really slow, like 10 mm/s, and they print really nice, flawless I'd say.

8dd7c9def6c7f5fca5c4a2b768a83e59?default=blank&size=40Marrut added this to the feeder collection ago
F0885862d8ed1feb3dff8107d22c879e?default=blank&size=40Garra commented ago

@dmols. Problem is that the PLA gears Inner Diameter is a bit too big (8.2 instead of 8). So there is some free space around bearings, which (when combined 3 gears) allows backlash. Thanks for advice about PTFE lubricants (btw. PTFE = Teflon) Do you print gears with ABS or Nylon?

19d39ad2524f70f581a4616d1469d58a?default=blank&size=40dmols commented ago

@Talon - I haven't tried PLA, but it might be that the size got a little smaller somehow. You shouldn't get backlash between the gears when you switch from going forward to backwards, because than you'd have problems with the retraction... Maybe before you reprint you can put everything together and test, no harm there I think... Anyway, from what you describe you might need to reprint the gears, print it slowly to get a good result. I use dry lubricants to get things moving smoothly (PTFE or Teflon works the same).

F0885862d8ed1feb3dff8107d22c879e?default=blank&size=40Garra commented ago

@dmols - I printed in PLA (not the best quality, but pretty good one). I assembled it on spare motor - everything fits tight, except there is some freedom with bearings (as I've mentioned 8mm bearing in 8.1-8.2 holes). As a result there is some small wobbling (back and forth) with gears (because of larger ID) , I'm not really sure if it will be a problem while printing.

Did You oil gears (light mineral oil or synthetic grease?) to reduce friction or no?

19d39ad2524f70f581a4616d1469d58a?default=blank&size=40dmols commented ago

@Talon: What material have you printed the gears with? Everything should fit perfectly, without any play when mounted completely. Put all parts together and check please.

@ChrissyP: It seems that the power needs to be balanced, otherwise you end up chewing material or clogging the nozzle, so the present design seems to avoid those issues nicely. Maybe a design with a planetary gearbox would work best with more power, be my guest to try! ;)

A5c0f84d51eb49dc910dd074c2b19dff?default=blank&size=40ChrissyP commented ago

The groove I made is in the original gear!

A5c0f84d51eb49dc910dd074c2b19dff?default=blank&size=40ChrissyP commented ago

I made no changes and the print is working well. Once I would love to have more power, because sometimes the stepper is rewinding....

Uuupps I forgot. I have made a small groove. It works better when I print smooth materials.

F0885862d8ed1feb3dff8107d22c879e?default=blank&size=40Garra commented ago

Hi there,

I have printed whole assembly, but for gears, I get 8.1-8.25 ID, when not completely assembled it feels that it has some free movement. However the body seems to fit spare motor nicely. Should I reprint my gears with -1% scale or should I just assemble it and hope that it will be nice and snug.

F0885862d8ed1feb3dff8107d22c879e?default=blank&size=40Garra added this to the UT2 upgrades collection ago
A5c0f84d51eb49dc910dd074c2b19dff?default=blank&size=40ChrissyP commented ago

Sorry double posted, what should I say... Tablett :-)

A5c0f84d51eb49dc910dd074c2b19dff?default=blank&size=40ChrissyP printed this ago
Carousel thumb 20160217 185737
Printed on:
ultimaker 2
Obsolete fabulous. It works with all kind of filament, include wood. BEST FEEDER DESIGN AT ALL. THANK YOU VERY MUCH FOR SHARING.
Great work, I would add a Gearbox, because the grip is good for more pressure. Thanks
A5c0f84d51eb49dc910dd074c2b19dff?default=blank&size=40ChrissyP printed this ago
Carousel thumb 20160217 185737
Printed on:
ultimaker 2
Obsolete fabulous. It works with all kind of filament, include wood. BEST FEEDER DESIGN AT ALL. THANK YOU VERY MUCH FOR SHARING.
Great work, I would add a Gearbox, because the grip is good for more pressure. Thanks
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1c6c5611fa6c18810820316036960bbb?default=blank&size=40whismer commented ago

Hi dintid.

I'm like you. I have some 3x10x4 bearing with me and I have enlarged the inner of the gear and holes on the body and cover.

Easy fix with Blender. Printed the parts and works a charm.

I will try to post them.

76652674c3ddbb662044858c1baa3c79?default=blank&size=40dintid commented ago

Managed to get the ninja-flex parts on :) I'll post a remix once I get everything in working order with the slightly larger bearings.

Having issues with the lid/cover not being completely level though, but I'll figure something out.

Thanks for the work again :)

76652674c3ddbb662044858c1baa3c79?default=blank&size=40dintid commented ago


I'll working on conversion while waiting the 2-3 weeks to get the cheap bearings. The cost like £10 in the EU + freight :)

Need to enlarge the holes a bit in any case to make them 0,2 larger :) making them ,2 og 2,2 isn't much difference.

Do you have any tricks to get the Ninja flex parts over the big gears (the right end of course).. am afraid of breaking something.

19d39ad2524f70f581a4616d1469d58a?default=blank&size=40dmols commented ago

Hey, so about the bearing, the ones you got won't fit. There is little room for increasing the gears inside diameter, so to make them work you would have to resize the gears, wheels, body, everything. I wouldn't go that way for some cheap bearings you can get easily, the tuning part is the most troublesome work of designing something like this. The 2 part yoke was inherited from the previous work, I didn´t touch them. Again, if you make just one part you will have to adjust the arm, but why fix what isn't broken? :)

76652674c3ddbb662044858c1baa3c79?default=blank&size=40dintid commented ago

Hello. hehe, by the ok'ish I meant they were a bit tight, but it is really not by much, and it Works fine when it comes to gripping and realeasing the bowden tube (using 6,4mm from E3D).

Any reason why you use a 2-part yoke instead of just some middle-piece to fit into the bearing (the baring for the bearing arm - I assume it is where the 2-part yoke goes?)?

76652674c3ddbb662044858c1baa3c79?default=blank&size=40dintid commented ago

Hehe, yes, i meant the Ok'ish as the holes was a bit tight, but they seem to work.

I havn't recieved my Ninja-flex parts yet, so havn't been able to test it. Just realized my I don't have any 3,8,4 bearings but only 3,10,4 bearings, so I'll see if I can make them fit - I'll get back to you, once I've tried it out.

19d39ad2524f70f581a4616d1469d58a?default=blank&size=40dmols commented ago

Hello dintid,

Glad you could test it. I'd like to clarify the ok'ish (lol) part of the fitting: you mean an increase in the diameter of the hole for the clamp would make for a better fit?

It is indeed a shortened down version as you say, but I remodeled it from scratch after my messed up STL editing started to give printing problems. So on this one the topology is clean :)

76652674c3ddbb662044858c1baa3c79?default=blank&size=40dintid commented ago

Thanks dmols.

I just tested the Bowden version.

I even mirrored the bowden on the "output" end to the "input" end, as I like to have some bowden tubing as an inlet. Seems to fit ok'ish. The bowden clamp-holes seems a bit tight compared to "Alternate um2 feeder v2", but the tube is getting grabbed and hold.

I'll make a version where I can feed the bowden tube right into the respective gears in either en - just a wideing of the holes really :)

Am I right that your "body" is simply just a shortened down version of the body from "Belt Driven Ultimaker 2 Extruder"? Asking as it seems identical but seems like it has been edited directly in STL format (I do that a lot myself, but it can end up with some corarser corners etc)?

19d39ad2524f70f581a4616d1469d58a?default=blank&size=40dmols commented ago

Ok, bowden tube version available! ;)

filename: 3_body_bowden.stl

19d39ad2524f70f581a4616d1469d58a?default=blank&size=40dmols commented ago

Hey dintid, will get around to make the one with bowden clamp as soon as I can, check back in a couple of days! I´d definety recommend 100% infill, you need everything included as hard as you can! I think you can get a fine working version with ABS, in my experience I got the gears in carbon fiber PLA, the body I have versions in both materials, they both work fine.

76652674c3ddbb662044858c1baa3c79?default=blank&size=40dintid commented ago

I would love to have a model for use with stock um bowden clamp as well :)

Do you recommend printing it in ABS or definently not ABS (due to particles) or doesn't matter?

100% infill or just 20, or?.. seems youmagine objects always recommend very low infill like 10-20, but it just seems wrong to me ;)

19d39ad2524f70f581a4616d1469d58a?default=blank&size=40dmols published this design ago