Dual hobbed extruder I was wondering about my pantograph printer ( [url=https://reprap.org/forum/read.php?152,839120]topic here[/url] ) when I have think about this thing why not use a gear of this kind (I have seen many kind of extruder drive but no kind like that): [attachment 108509 faceA.png] [attachment 108510 faceB.png] It's like of some push pull drive and the both side of the filament are be drive (the pics are just sketchs) animate pic: [url=https://www.dropbox.com/s/lbhb42bb5lltub4/anim.gif?dl=0]video[/url] (better if you download the file and open it with your browser) https://reprap.org/forum/read.php?1,840705,840705#msg-840705 Tue, 14 Apr 2026 02:48:41 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,840705,849909#msg-849909 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,849909#msg-849909 [attachment 110678 arm2.png]

extruder calibration, look here:
https://mattshub.com/2017/04/19/extruder-calibration/

the scad files:

https://www.dropbox.com/s/rb4mzyhejuzd62a/armMk2.tar.gz?dl=0


try dual extrusion with single nozzle, but doesn't really work:

https://reprap.org/forum/read.php?70,849907,849907#msg-849907]]> herve robert General Sun, 24 Mar 2019 07:53:36 -0400 https://reprap.org/forum/read.php?1,840705,846553#msg-846553 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,846553#msg-846553
I made an archive with stl and scad files and pictures..

[www.dropbox.com]


I'll try a dual extrusion with one nozzle with this new version.]]> herve robert General Sat, 09 Feb 2019 08:00:19 -0500 https://reprap.org/forum/read.php?1,840705,843060#msg-843060 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,843060#msg-843060
If one is looking for alternative/interesting solutions--I would consider running the second extruder before the PTFE--acting as a pre-feed. If a second driver (for example, E1 on RAMPS) with which to mirror the primary extruder is not available, wire the second extruder parallel to the primary. Or, one could design a powered spool holder, either synchronized with the extruder, or triggered by filament tension.]]> jefbed General Tue, 01 Jan 2019 09:02:22 -0500 https://reprap.org/forum/read.php?1,840705,842555#msg-842555 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,842555#msg-842555
[reprap.org]

The belt solution, which drives
filament using belts. This allows for great torque on your filament, without
slipping or damaging the filament. The geared solution gives enormous torque
from even a simple stepper motor.

:S]]> cozmicray General Thu, 27 Dec 2018 18:06:23 -0500 https://reprap.org/forum/read.php?1,840705,842388#msg-842388 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,842388#msg-842388
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jamesdanielv
good luck!

few chances, fun anyway...]]> herve robert General Wed, 26 Dec 2018 07:16:19 -0500 https://reprap.org/forum/read.php?1,840705,842377#msg-842377 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,842377#msg-842377
[attachment 108940 exAlpha.png]]]> herve robert General Wed, 26 Dec 2018 05:13:11 -0500 https://reprap.org/forum/read.php?1,840705,842077#msg-842077 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,842077#msg-842077
please post results fail or successful. it improves everyones understanding of what works or needs improvements.

if people say something doesn't work, look into why or what they did that failed and work from there. good luck!

also watch out for people just trying to keep you busy. decide in advance what you are willing and not willing to work on for this to work.]]> jamesdanielv General Fri, 21 Dec 2018 09:26:52 -0500 https://reprap.org/forum/read.php?1,840705,841183#msg-841183 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,841183#msg-841183
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o_lampe
Just a wild thought:


One of these on each side: More bite/less pinch and better guidance...

Indeed, here the diam is infinite, all good then, too bad the movement is not continuous. Belts then ? Already done but too bulky, not worth it.
]]> MKSA General Wed, 12 Dec 2018 13:48:04 -0500 https://reprap.org/forum/read.php?1,840705,841182#msg-841182 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,841182#msg-841182

One of these on each side: More bite/less pinch and better guidance...
]]> o_lampe General Wed, 12 Dec 2018 13:37:42 -0500 https://reprap.org/forum/read.php?1,840705,841109#msg-841109 Re: Dual drive extruder https://reprap.org/forum/read.php?1,840705,841109#msg-841109
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dc42
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MKSA
Most current extruders are non geared....

Really??? Have you any evidence for that assertion? I've come across more geared extruders than non-geared ones.

What I see being sold/ installed/copied are mainly the cheap MK8.

Anyway, the key point I wanted to raise is the small hobbed gear diam, required to get the push from these, that are used even with geared extruder.

OK, my assertion can be removed. May be wrong from a market perspective and is irrelevant to the technical discussion that follows.

I started with a MK8, poor hoobed gear, made my own, had to go for 8.5mm diam then designed a compact, light geared one using a NEMA14, a bigger hobbed gear (12mm, case hardened steel, bites like a shark) at the same time.]]> MKSA General Wed, 12 Dec 2018 01:15:31 -0500 https://reprap.org/forum/read.php?1,840705,841088#msg-841088 Re: Dual drive extruder https://reprap.org/forum/read.php?1,840705,841088#msg-841088
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MKSA
Most current extruders are non geared....

Really??? Have you any evidence for that assertion? I've come across more geared extruders than non-geared ones.]]> dc42 General Tue, 11 Dec 2018 16:21:53 -0500 https://reprap.org/forum/read.php?1,840705,841024#msg-841024 Re: Dual drive extruder https://reprap.org/forum/read.php?1,840705,841024#msg-841024
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o_lampe
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Deckingman
On my machine, I needed 5mm of retraction on the Titans but only need 3.5mm on the BMGs. I suspect this is due to the spring tensioner causing some wear of the filament during the retract so it needs higher un-retract due to the reduced filament diameter. I didn't get around to playing with different retract / un-retract distances but that may have been a cure.

I believe the Titan deforms filament more and therefor needs to push harder to overcome Bowden tube friction. That also has an effect on retraction length IMHO.
There's simply more zigzag-filament in the same Bowden length.

Hobbed gear diam is too small. Most current extruders are non geared, therefore the usual hobbed gear effective diam is around 8.5mm. I make my own, diam 12mm (14mm planned eventually), better grip as more teeth are engaged and less filament deformation due to the bigger diam.
Bondtech also use a bigger diam and goes one step further, two of them. So far didn't feel the need to go that extra step.]]> MKSA General Tue, 11 Dec 2018 06:02:52 -0500 https://reprap.org/forum/read.php?1,840705,840989#msg-840989 Re: Dual drive extruder https://reprap.org/forum/read.php?1,840705,840989#msg-840989
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Deckingman
On my machine, I needed 5mm of retraction on the Titans but only need 3.5mm on the BMGs. I suspect this is due to the spring tensioner causing some wear of the filament during the retract so it needs higher un-retract due to the reduced filament diameter. I didn't get around to playing with different retract / un-retract distances but that may have been a cure.

I believe the Titan deforms filament more and therefor needs to push harder to overcome Bowden tube friction. That also has an effect on retraction length IMHO.
There's simply more zigzag-filament in the same Bowden length.]]> o_lampe General Mon, 10 Dec 2018 23:10:31 -0500 https://reprap.org/forum/read.php?1,840705,840950#msg-840950 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840950#msg-840950
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MKSA
-As shown however, idlers will interact and one may prevent proper push of the other against its hobbed gear.

in other words, if there is to much pressure in one side there less pressure in the other side...
good or bad ?]]> herve robert General Mon, 10 Dec 2018 14:50:14 -0500 https://reprap.org/forum/read.php?1,840705,840943#msg-840943 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840943#msg-840943 Here's something I was working on about 5 years ago- very smooth extrusion...
More here: [vimeo.com] and here: [www.thingiverse.com]
My design used counter rotating #6-32 nuts to drive 3mm filament. It had very strong grip and push force, but didn't work well when retracting.

And I see that someone at MIT recently used a similar technique to drive the filament: [3dprinting.com]
MIT's extruder uses a single nut to drive the filament and some anti-twist rollers instead of a counter-rotating nut.]]> the_digital_dentist General Mon, 10 Dec 2018 12:56:49 -0500 https://reprap.org/forum/read.php?1,840705,840937#msg-840937 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840937#msg-840937
-As shown however, idlers will interact and one may prevent proper push of the other against its hobbed gear.

I recommend pursuing the first approach. Competiton to the Bontech may lead to cheaper ones for people who really need the extra force and likely to put a stop to all these clumsy extruders popping out regularly.]]> MKSA General Mon, 10 Dec 2018 11:24:22 -0500 https://reprap.org/forum/read.php?1,840705,840932#msg-840932 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840932#msg-840932
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MKSA
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herve robert

triple hobbed:

[attachment 108576 frame00015.png]

Just wondering why the "idlers" are set that way, on the same articulated arm ?


"idler" wheels can be set on individual independant mechanisms.
but for each arm you need a push spring.

another purpose is:

to build an automatic or semi-automatic filament loading.

on the video the sequence isn't exact.

first, the unloading:

step (B ), the "orange" filament go back.

then the arm is moving (C).
but in the same time the filament is hold by the arm and it's get motionless.

second, the loading:

reverse mode with the "blue" filament...(C,B,A).



(utopic work not in real life. must make for talking more about it)

[attachment 108590 arm.png]]]> herve robert General Mon, 10 Dec 2018 10:31:47 -0500 https://reprap.org/forum/read.php?1,840705,840907#msg-840907 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840907#msg-840907
Really, since the TMC2660 drivers proved to be weak while depending on someone else's config apparently with smaller motors (damn I wish smoothie was more thoroughly documented!!!) I had to play to get it running at all.
At the least I've been having fun doing something I've not seen before, but I really do think that since I now have full powered drivers on it, the dual extruder drive would pull Chicago closer if given the chance (I'm in Michigan). :)
I would like to mess around with a belt driven 2:1 though. I still can see marks in my prints that look almost like the MK tooth imprints, but faint and shallow. Perhaps decoupling can solve that on it's own without the need for large gear ratios...I'll see.]]> Diggrr General Mon, 10 Dec 2018 05:24:50 -0500 https://reprap.org/forum/read.php?1,840705,840901#msg-840901 Re: Dual drive extruder https://reprap.org/forum/read.php?1,840705,840901#msg-840901
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dc42
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Srek
For me a reason to not do it is that it is unnecessary. I have thought about filament transportation with multiple points of contact, but in the end they did not offer any advantage. A well designed classic direct drive will develop enough force for well over 100mm/s. Another issue is size, such a setup will be larger than a single point of contact drive.

You might find [somei3deas.wordpress.com] interesting. Summary: in the particular case of using a mixing hot end, where the same piece of filament may get moved back and forth many times, the Bondtech (dual drive) extruder performed much better than the Titan (single drive) extruder. This doesn't prove that the dual vs. single aspect is solely responsible for the difference (the shape of the teeth on the hobbed shaft may have been different too), but it seems likely that it was the major factor.

For my particular usage case which is linked to above, I'm inclined to think that the reason the Bondtech performed better than the Titan is that there is no appreciable spring tension on the Bondtech. What seems to happen is that, with a sprung loaded extruder, multiple retract and un-retract cycles over the same piece of filament cause the filament to wear which reduces the diameter. The spring tension then pushes the hobbed bolt against this reduced diameter which causes it to wear even more until eventually (several thousand cycles), it grinds right though the filament. Whereas with the Bondtech using a fixed distance between the two hobbed bolts, what seems to happen is that the teeth cut grooves in the filament but because there is no spring, these grooves don't get any deeper. So it acts like a rack and pinion gear (with the filament being the rack and the hobbed bolts the gear).

I've used both Titans and BMGs on my printer and found that both will handle 4Kg reels and at print speeds up to 300mm/sec. Both are about the same size and cost. Having said that, I prefer the BMGs because they are much much easier to fit and maintain. Also retraction is more consistent, especially when doing lots of small moves with retraction between them. On my machine, I needed 5mm of retraction on the Titans but only need 3.5mm on the BMGs. I suspect this is due to the spring tensioner causing some wear of the filament during the retract so it needs higher un-retract due to the reduced filament diameter. I didn't get around to playing with different retract / un-retract distances but that may have been a cure.]]> deckingman General Mon, 10 Dec 2018 04:48:12 -0500 https://reprap.org/forum/read.php?1,840705,840884#msg-840884 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840884#msg-840884 The rollers span the width of the spools so the filament can't jump off the flanges and tie itself into knots.

I have a Titan in my corexy machine and have been able to run it as high at 200mm/sec with 10k acceleration (not how I normally run it, but the 3:1 gear reduction doesn't prevent running at that speed).]]> the_digital_dentist General Sun, 09 Dec 2018 21:36:37 -0500 https://reprap.org/forum/read.php?1,840705,840883#msg-840883 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840883#msg-840883 Perhaps my first and last large spool though, it's been a PITA from the start. I spent more than the bulk discount on drivers. Oy.

Interesting info about the waves in the prints. That I do see sometimes. Perhaps willing to try a 2:1 belt drive, just to see if it's a decoupling that's needed. 5:1, likely not.

Thanks for the info!]]> Diggrr General Sun, 09 Dec 2018 20:56:56 -0500 https://reprap.org/forum/read.php?1,840705,840881#msg-840881 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840881#msg-840881
If you're having trouble pulling filament from the spool because of the spool's mass, maybe the design of the spool holder could use some improvement.]]> the_digital_dentist General Sun, 09 Dec 2018 19:01:33 -0500 https://reprap.org/forum/read.php?1,840705,840872#msg-840872 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840872#msg-840872
The fact remains that the little motor has to travel 5.18 times further, and 5.18 times faster for each move it makes, to be equivalent to a direct drive.

@Arnold, cool!]]> Diggrr General Sun, 09 Dec 2018 15:52:13 -0500 https://reprap.org/forum/read.php?1,840705,840870#msg-840870 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840870#msg-840870
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herve robert

triple hobbed:

[attachment 108576 frame00015.png]

Just wondering why the "idlers" are set that way, on the same articulated arm ?]]> MKSA General Sun, 09 Dec 2018 15:34:03 -0500 https://reprap.org/forum/read.php?1,840705,840869#msg-840869 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840869#msg-840869
So I designed a larger single drive wheel with soft flexible flanges that envelope the filament ever so gently. As far as pulling power it can easily tackle a 4 kg spool, I just tested the latest reiteration and reached 11 kg's of pulling power (which seems to be the breaking strain of 1.75 PLA) using a RUMBA control and 4988 stepper driver. The 3 mm test was conducted with a higher power stepper driver @ 24v and achieved even more.

vid of demo here]]> Arnold Lane 1000 General Sun, 09 Dec 2018 15:30:10 -0500 https://reprap.org/forum/read.php?1,840705,840867#msg-840867 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840867#msg-840867 I am pretty sure that with a proper filament guide from spool to extruder, with built in elasticity a unique good geared extruder would work with these 4kg spool.
My filament guide is just a piece of PTFE tube attached with a rubber band to the frame, simple.

Geared extruders work, the ratio is not strange, not an integer is normal (Good Engineers thought that !). Anyway, you will never get an integer "step rate" due to the hobbed gear.]]> MKSA General Sun, 09 Dec 2018 15:20:06 -0500 https://reprap.org/forum/read.php?1,840705,840863#msg-840863 Re: Dual drive extruder https://reprap.org/forum/read.php?1,840705,840863#msg-840863
I still may build a NEMA23 extruder, and uncomplicate my setup though. I have a nice one on hand, and a 3A driver to push it with.

...all this mess for trying a giant roll of filament instead of having multiple rolls laying about. LOL]]> Diggrr General Sun, 09 Dec 2018 15:00:50 -0500 https://reprap.org/forum/read.php?1,840705,840862#msg-840862 Re: Dual hobbed extruder https://reprap.org/forum/read.php?1,840705,840862#msg-840862 WesBrooks General Sun, 09 Dec 2018 14:48:04 -0500 https://reprap.org/forum/read.php?1,840705,840860#msg-840860 Re: Dual drive extruder https://reprap.org/forum/read.php?1,840705,840860#msg-840860 For me the two most important things to maximize extruder strength and speed are exact guidance of the filament, no kinks around the hobbed idler or similar, and a hotend that requires minimal pressure.]]> Srek General Sun, 09 Dec 2018 14:39:24 -0500 https://reprap.org/forum/read.php?1,840705,840856#msg-840856 Re: Dual drive extruder https://reprap.org/forum/read.php?1,840705,840856#msg-840856
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MKSA

What kind of hotend/filament (1.75mm) requires that much force ?

Anyway, the key factor is the hobbed gear/idler. With a good one, it is possible to pull 40N using a geared Nema17 42mm. To push is an other story. You better have a well guided and short path between extruder and hotend.

The MK7 hobbed gears quality can be shitty. So to put two bad extruders in series is a complex, heavy, costly solution.

The Bondtech is based on a good design used for more than a century in the steel industry notably. You get the extra force and in addition it lessens the damage to the filament, comes handy when there is a lot of retraction.

In silent mode, the TMC drivers were not able to pull a 4 kilogram roll of filament, even with the rated 2A to the motor.
I had another identical setup on the shelf, so I used it inline. It still skipped steps occasionally, unless I kept the line slack by hand for a whole 5 hour print.
I've since changed drivers, but really see no reason to remove my experiment. Now I can't make it skip, it pulls the filament through my fingers. I have the fittings drilled and the PTFE trimmed and extending to the gears, so there's no other place for filament to go but up the Bowden tube--the single one would print flex filament just fine, fast enough to keep a volcano fed at speed.

Bondtech extruders are popular, but I've never seen the value, TBH.
$190 for a plastic extruder with a $36 geared stepper, seems a little over the top.
5.18:1 planetary gearbox? Who thought that up? I've never seen a gearbox without backlash (effects are negligable, but still..).
I do not like non-integer step rates (492.45 per mm). I'd rather have the controller rounding corners than rounding math.
4.3mH is getting higher than I like, it limits RPM for a motor that really needs it to retract at useful speed (like 5.18 times faster).

I don't judge, people use what they use. Personally I can afford a QR, but I won't do it.

BTW, the hobbed MK7 drive gears on RobotDigg are of excellent quality and finish. Much much better than eBay specials that are really made for 3mm filament, but claim to be usable for both...that's rubbish.]]> Diggrr General Sun, 09 Dec 2018 13:58:54 -0500