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Yet another extruder filament drive

by jag, published

Yet another extruder filament drive by jag Mar 18, 2011

Description

The delrin plunger, while an elegantly simple idea, bothers me a little because of the added drag on the filament. Even more so with the stepper driven mk6 extruder since for me at least there seems to be a pretty fine line between having it tight enough and too tight such that you are losing steps.
Like jstkatz and his thingiverse.com/thing:7037 I didn't like having the 4 screws and springs. I wanted something a little little simpler and could more easily pivot out of the way.
jstkatz's design definitely came out a little more elegant but functionally I think they are pretty similar (except mine uses the mk6 nema 17 motor).

Recent Comments

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Can I use this with a Mendel? And mount a J-head hot end? What carriage does it need?
Bot 4037 just took this one on too, very nice.
This is amazing! I was tired of the stock extruder skipping steps. I still don't test this (I need to buy another bearing) but until now, it looks great! I printed both pieces as is in the file and for some reason (maybe my mk6 felt I was going to replace him :P) the print quality was outstanding.

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License

Public Domain
Yet another extruder filament drive by jag is licensed under the Public Domain license.

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Instructions

Print the two parts. You shouldn't need support, I added some into the files already.

There is now a quick release lever for this extruder ( thingiverse.com/thing:7449 )
I seem to be having good success with the lever and no spring at all. It looks like an M4x40 bolt would be the right one for use with the lever.

Cut the support off the pivot location on the main body (on the lower right).
Cut the support material out of the pivot arm where the bearing mounts.
Clean up as necessary. It may help to run an appropriately sized drill through all of the holes.
Mount the bearing to the pivot arm with an M6 bolt & Nut (or you can print out thingiverse.com/thing:11424 )
Mount the pivot arm to the body with an M3 bolt & nut on the bottom and an M4 bolt, nut, washer and spring on the top.
You may need to cut out a little material to fit the M4 nut in there. I'll make slot a little bigger for the next version.

Insert the 4 M3 nuts into the provided slots. The one by the idler pivot can be a little fiddly to get in there.
Bolt to the extruder support with 4 M3x12 Bolts.

Bolt the stepper, cork gasket & fan mount with 4 M3x12 Bolts.

Let me know if I missed anything!

Change Log (started on 5/8/11)
5/8/11 Uploaded new idler arm (stl and alibre part) that works with 1.75mm filament (and 3mm)
6/28/11 Scaled the body part so that it doesn't need to be scaled before printing (inches->mm)
Can I use this with a Mendel? And mount a J-head hot end? What carriage does it need?
This is amazing! I was tired of the stock extruder skipping steps. I still don't test this (I need to buy another bearing) but until now, it looks great! I printed both pieces as is in the file and for some reason (maybe my mk6 felt I was going to replace him :P) the print quality was outstanding.
Did anyone else have the problem of the idler arm breaking loose because the front half of it's axis mounting in the main body is too weak?
Designing a stringer arm after it broke 2 times during assembly.
http://marcuswolschon.blogspot.de/2012/11/improving-gaerisls-extruder.html
I designed it to be printed on it's side because, as you found out, it's not strong enough if you print it on it's back. :)
 I printed my stronger one on it's back and it works just fine.
In fact it's much stronger then the main body now.
OK, OK...so this is the singlest, most amazingest, extruder upradingest, printastic thing in the known Thingiverse! Seriously what took me so long to upgrade!! Bot 4406 is loving it!! :-D
Glad you like it!

I might argue that the mk7/8 is an even better upgrade but I guess you can't just print that.

Thanks!
Bot 4037 just took this one on too, very nice.
I've been using this design for a few months now and just LOVE it. It is so much better than the stock design.
If anyone else has found themselves lacking an M6 Bolt + nut, I've created a printable pin to do the job: thingiverse.com/thing:11424
Nice, I added it to the instructions.
One issues I've found with using this and the 1.75mm plastic is the tendency to jam and spool excess plastic around the bearing on the idler arm. I think the problem is the 1.75mm has to be bent fairly sharply to hit the motor, and then bent back to get through the hole. Has anyone else seen this problem?

The long term solution is a redesign to move the motor shaft ~1-2mm closer to the hole so that the plastic is inline the whole way - short term I'm going to try carving out the mounting holes and shifting the motor over. I'll reply back if it works...
I've never had it wrap around the idler bearing, I have had it crumple up in the hole leading down to the hot end (because it's too large). I've also had it snap when there is a lot of reversals but I don' think thats related to this design, I just think the 1.75mm can't handle it.

I was planning on uploading a version with a bigger filament hole that I can fit a ptfe tube that goes all the way down the hot end to the nozzle.

I've been resisting making it necessary to have two different versions, I kind of wanted it to be able to be used with 1.75mm or 3mm.
jag - in reply to Guest
oops, I wasn't logged in :)
jahg - in reply to jag
Yeah, I like the idea of having only one design - maybe slotting the holes mounting the motor? Slide it one way for 3mm, the other for 1.75... I'll have to play with it a bit more I think.
jahg - in reply to jahg
Actually, now I have the thing in pieces in front of me it is pretty much in line already. Time to see if I have excess ptfe tube!
About to print one of these myself (the bearings should arrive today.) What infill settings are people using? I want to be sure it's strong enough to hold. (Also, the slot in the lever where the bearing is bolted in place prints poorly if you use extra shells, due to a Skeinforge bug- it won't have any infill.)
I printed mine with pretty high infill. Maybe 75%. I tend to avoid 100% as it doesn't allow for any extra plastic if your calibration isn't perfect (or the filament changes diameter).
Thank you. Got it up and running- I can't believe how much better it works than the original filament drive.
Great! It does seem to handle reversal a lot better and it's a lot less drag on the filament.

Glad you like it!

It's pretty cool to see so many people using something I designed all over the world...
Just printed one just in case my MK6 conks out on me. A beautiful design, especially with the quick release!

Two nits to pick, which I offer with all the humility of a newb who may be missing something:
1. My M6 nut does not fit between the lever and the body. I would need a slimmer nut with less engagement, and to be honest the M6x16 doesn't really stick out enough to fully engage the nut anyway.
2. In
the instructions, when you say that it looks like an M3x40 bolt would work well with the quick release in the absence of a spring, I think you may mean an M4x40. No?

Other than that, while I hope never to need it, I will sleep more soundly knowing it is standing by.

Thanks for the design!
jag - in reply to syvwlch
I'm glad you like it.

No worries about nit picking, isn't that what thingiverse is for?

My M6 nut just barely fit. Maybe yours is a tiny bit bigger? It was a tight fit but I didn't want to eliminate all of the material behind the arm for some reason. You could maybe put a bolt in from the back (probably not a socket head though unless it's a button head) and then it wouldn't matte
r how long the bolt was. A little ugly though...

I'll fix the M3 vs M4 error, I must have just spaced that.

It is good to have a backup!
Thanks for the input!
syvwlch - in reply to jag
Yeah, I only have socket head bolts in that size. The threads are nice and tight in the plastic, so it's not going anywhere just now, even without a nut. I can probably use it as is for a few days while I source a different bolt, should I ever need it.

Thanks again, a beautiful part. :-)
I added a M3x16 adapter to use with the 606 bearing. the ones that come with the kit fit really nice.

thingiverse.com/thing:11157
I notice spome have springs and other do not. Is the current version the one with springs?

Scott
jag - in reply to Scooter
You can use it with springs, or without. I use it with no spring and the quick release:

thingiverse.com/thing:7449

It works great.
Turns out that the original design didn't work with 1.75mm filament because the idler arm interfered with the motor shaft bearing (unless you left it out).

I've uploaded a new idler arm that doesn't have quite as much plastic around the bolt hole so it shouldn't interfere now. Still a bit of a pain to feed the 1.75mm in because the hole in the body is oversized. I think I'm going to get a piece of ptfe tubing to slip in there for when I'm running 1.75mm. I will upload a 1.75mm specific version of the body soon that has a smaller hole.
heronog - in reply to jag
sliping a little of the small PTFE tubing in the extruder works really well. I'm printing 1.75mm now :D
What stepper motors are people using with this unit, and where are you purchasing them from. I am trying to get my grocery list together.
It's set up for the Mk6 Nema 17 stepper though you can use it with this: thingiverse.com/thing:5795 which would allow you to use a stepper with less torque. I may make a version of this with an adapter plate built into it for use with geared stepper setups but I haven't gotten around to it yet.
Would you be interested in adding this to the MakerbotUnited design contest? thingiverse.com/thing:7612
jag - in reply to carmiac
Sure. I'd say this was very much a collaborative work.
Is this for 3mm filament only or for 1.75mm also?
jag - in reply to Guest
It's currently set up for 3mm but should work for 1.75. The idler should be able to contact the drive wheel so as long as the hobbed groove in the wheel is less than 1.75mm deep it should be able to drive it. The filament will be able to flex to the side a bit because the filament hole is 3mm but I'm not sure if that will matter much. I should be getting some 1.75 soon so I can test it out on mine. I can make a version with a smaller hole if necessary.
jag - in reply to jag
Just a heads up. I ran some 1.75mm filament in my extruder. Thre is a bit of a clearance issue between the idler arm and the motor shaft end bearing. It could probably be solved with a bit of sanding. I'll hopefully upload a new version soon. It's also a little tricky getting the 1.75 mm filament loaded in there with the 3mm hole. I'm going to look into making a swappable piece that contains the filament guide hole so that I can easily swap between 3mm and 1.75mm.
I have a probably dumb question - why is the object so small when I open it in replicatorg?
jag - in reply to sssidney
I forgot to scale the stl to millimeters before uploading it. I figured I would do it for the next version rather than re-uploading it. You can do it quite easily in replicatorg.

I usually open it in replicatorg and scale it and center it before uploading but this time I forgot...
sssidney - in reply to jag
I should have read all the comments first. Thanks!!
Making and using the quick release. Really looks good!

Taking the spring out and using the flex of the ABS - brilliant!
jag - in reply to bstott
Thanks! I'm loving it! It's working great for me!
if i see correctly, there is a missing 606 bearing in dreameredeemer'S photo. the one right on top of the motor.

I was adapting this extruder to fit the makerbot dc motor and the mk4 hotend but i find myself without the extra 606 bearing needed to make the full conversion. witch brings me to this question: is the bearing on top of the gear really necessary? If not it would mean that i wouldn't have to modify
the design more to use a 608 bearing that i'll soon have in stock. :)
I had to order one in and was impatient. I think the extra support for the axle is probably a good thing.
jag - in reply to Robbob
So you are drilling it for the bolt pattern for the DC motor?

That DC motor has pretty wimpy bearings (bushings I think. I seem to remember that there is only one on the output shaft. That would probably wreck the motor pretty quick to not have an outboard bearing on it. I hadn't really intended the design to work with the DC motor. I guess I could look into adding the appropriate bolt pattern.
Robbob - in reply to jag
I'm working on the bolt pattern so far so good i printed my updated version but i still have some adjustments to make. Think i should post a WIP about it... later tonight *DONT_KNOW*
definitely dig the new quick release

I was wondering if a the long lever arm could be fashioned to provide the spring force needed, great to see it working so simply. I'd be interested to hear if there are any issues with the plastic creeping over time, you can always just tighten the quick release one more turn however. The end of l
ife would only come when it was bet over to far and started hitting the rest of the work, then you just have to print another. Keep us posted on its longevity? The arm is ABS right? I wonder if the rigidity of PLA would be a problem.
jag - in reply to jstkatz
Thanks, I'm glad you like it. I kind of figured that a lot of spring isn't really necessary. I think the idler could be rigidly set to be a little less than 3mm from the drive wheel (the knurled part) and it would be fine. The plastic would just bite into the drive wheel to make up the difference. Considering how little travel there is in the quick release, there isn't much bending of the arm going on. I'm guessing it will last a good long time. But, it is nice that it's only a 15 or 20 minute print if I ever want to replace it.

I could scale the quick release up for your drive (or you could if you have alibre). What size bolt are you using for the tensioner?
I've added this to my big list of ToM upgrades at thingiverse.com/thing:6443
brilliant! love the simplicity of your design. if you do it for a mendel i would be very happy :)
jag - in reply to hexitex
I'll have to look at the mendel mounting setup. Would you want it to connect to the mendel hot end?
Do you have a paypal account? I think you deserve some money for such a beautiful design. I'm using the previous version and the only issue I've had is some slipping--despite thinking that the spring I picked out might impart too much force, it ended up needing to be almost completely compressed. Now I'm getting some amazing prints, I passed the reversal towers test for the first time!
Thanks! I don't need money for the design. The occasional flattr is more than enough!

I mostly spent all the time designing this because I wanted it for my makerbot and it was a nice learning exercise.

I'm glad it's working for you!
jag - in reply to jag
It's also remarkably cool that I can design something on my computer and then people can make it all over the world. It's always pretty exciting when I get the "someone made your design email". That's payment enough for me :)
Ok, I just uploaded a new version. Unfortunately, I forgot to scale them to be metric so you will have to do that in replicatorg.

I've made a few of the changes as suggested by carmiac.

The idler are now sticks out a bit above the tensioner bolt to give you something to grab to release the filament.
The lower mount for the idler arm has been extended out a bit so that the hole isn't so close to the edge.
There is now a bit of a chamfer on the filament hole below the drive wheel/i
dler to hopefully guide the filament in there a bit better for filament changes.
On the idler arm, the top of the bearing mount part has been extended most of the length of the arm to help resist delamination.
I've changed my support method for the lower idler mount to be the same as the idler suppo
rt.

I think that's it...
carmiac - in reply to jag
I've printed out the new idler arm, it's nice!
jag - in reply to carmiac
Now you'll have to print out the quick release lever...
jag - in reply to carmiac
Great!
And... I've finished building and testing. It works great, and the stepper adapter plate fits perfectly.

This has become my favorite drive, thanks!

OF course, I've got a few notes and nits.

Idler Arm:
1) I used an M6x12 to mount the bearing with no nut, but an x15 or x18 would have been better. I'm not certain there is clearance to put a nut on this, nor that it is needed. Maybe make the hole a
smidge smaller so that it screws in tighter?

2) I'm still a bit paranoid about delamination, so I'd like to see the top bearing arm beefed up a bit.

3) Extending the length of the arm past the M4 mounting hole would make it easier to pull open against a spring. This is probably the biggest thing
I'd like to see done to the idler arm, with #2 right behind it.

4) I used a spare M4x50, a 1/4 by 7/8 inch compression spring and 7mm worth of washers for the idler arm tensioner. An M4x45 probably wouldn't need the washers.

5) I put a thingiverse.com/thing:5704 (printed using this dri
ve!) on the end of the M4 to make it easier to adjust.

Extruder Body:
1) The holes for the NEMA17 mounting nuts are round, not hexes. I was able to smash them in place, but it was a bit tighter than I would like.

2) The idler arm fit in the mounting slot was tight enough I had to do a bit of sa
nding. I also had a bit of warping there on my print, so it just may have been that.

3) The idler arm pivot supports seem a bit small, particularly the top one. Making them come down straight, or even flare out would make me less worried.

4) Changing filament mid-print can be a bit difficult. T
he problem is that the filament bends around the idler bearing a bit, pushing it out of alignment with the lower feed hole. Adding a small 'V' on the right side, like there is on the left would probably solve this. This is the only issue on here that I would go to the bother of re-printing and ass
embling the body for.

Again, this is a great design!!!
jag - in reply to carmiac
Great!

Thanks for the input. I'll do some work on it tonight and hopefully print another one out for my machine soon (Once I have my extruder working again).

The holes for the stepper are round because I was intending them to be a countersink for the cap head screws since they go the other way with the Mk6 stepper. I can make the countersink hex and then they will be dual purpose.

I'll extend the idler arm a bit, that's a good idea. I was planning on making a little lever with a cam to loosen the spring tension for changing the filament. I'm not sure if I can get enough travel in a reasonable amount of space though.

I was able to fit a nut in there for the bearing. You
are right that you could probably just thread into the plastic and it might be fine and probably less likely to vibrate loose.

I'll try to put a bit of a chamfer on the hole for the filament.
I'm glad it's working for you! Thanks for testing it out for me!
Was your idler tight at the pivot on the
bottom?
carmiac - in reply to jag
My idler was very tight at the bottom pivot. I ended up sanding it down a bit to fit, though there was some warping there which may have caused the problem.
jag - in reply to carmiac
I'm guessing it's the warping (or maybe sagging because it isn't very well supported. Mine is a pretty loose fit once I get rid of the strings. I think I'll probably switch the support for that to be the same as the idler has. I'll also make it a bit thicker too.
jag - in reply to jag
Your print is making me think that now I should mash this up with the stepper adapter plate to make things simpler for people without the high torque stepper motor.
Nice work, people were unhappy that my design was nema 23 only, now I don't have to worry about making another version.
So, I can't build the most recent version of this because my thermocouple amp on my extruder controller just went and fried but, it looks like it's pretty good.

The bearing is a pretty snug fit. I had to shave out a tiny bit of plastic to get it fit in.

Hopefully I'll get my bot back up and running soon and I can get this running on it.

I printed one earlier today but I lost a few steps in the middle of the print so it was a bit skewed...
carmiac - in reply to jag
Oh, and what size idler bearing is this made for?
carmiac - in reply to jag
Ok, when I get back to town in a week I'd be happy to print out your designs to help tet them. But, it won't be for a week. Stupid paycheck generating job. ;)

So, what are you doing the development in?
jag - in reply to carmiac
Cool. Hopefully I'll have my bot back up in a week or so.

I'm designing in Alibre.
carmiac - in reply to jag
So, I got back to town a couple days early, but only have time to print the idler arm. After looking at it, I'm a bit worried that the bearing support arm on top as you print is going to be a weak point. If you were to extend it up the length of the main arm halfway or so I think it would be much less likely to delaminate.
jag - in reply to carmiac
Mine seems pretty tough but that's a pretty easy change to make. I'll try to do that when I get home. Both of the bearings are 606 bearings (17mm OD). The hole isn't really oversized at all. I put a bit of a taper in it to let the bearing fit in easier but I think I need to do a bit more.
First test run of this (without the bearing on the end of the motor shaft).

It seems I didn't measure the drive wheel correctly so the filament isn't quite centered on the exit hole. Also, the part where the tensioner nut sits isn't strong enough and snapped off (which is also a symptom of my print quality which will hopefully be fixed with the next print). I'll modify the design and upload new files.
jag - in reply to jag
All the files are now the latest revision. The new version is printing away (using the previous version).
carmiac - in reply to jag
I like the way they look. Can't wait to hear how this goes.
jag - in reply to carmiac
Thanks. It didn't print too well (I don't have a spring on there yet so am using some tubing as a spring). There was some slipping in the middle so the bearing mount was too fragile. I redesigned it again.
Oh! I really, really like this! The technique you used for getting the grain right in the pivot arm while having a large overhang looks cool.

A couple question/comments/requests:
Do you think an upper guide for the filament before the drive is needed to keep the filament coming in correctly?
Could you release a version that doesn't have the teflon tube hole?
I think you will find that the extra bearing for the motor shaft is necessary o
ver the long run to avoid putting too much strain on the motor bearings and flexing the part. The bearing pocket is also necessary for those of us using a stepper adapter plate thingiverse.com/thing:5795
jag - in reply to carmiac
Good idea!

There is now a version that has a spot for a bearing and with the filament hole at around 3mm.

I haven't tested it yet. I'll hopefully print one out later today but first I think I'll install the one I already printed to test it out (and use it to print the next iteration).
I really like this design and would really like to see how it performs!
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