MiseryPusher: Geared Stepper filament pusher for MK5 extruder

by MiseryBot, published

MiseryPusher: Geared Stepper filament pusher for MK5 extruder by MiseryBot Mar 19, 2011


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This is a retrofit stepper design for anyone wanting to get rid of the DC motor filament pusher. It uses the MK5 hot end.

Edit: I ended up having to make an aluminum idler pulley. The printed ABS idler pulleys work for a while but eventually get a flat spot and stop working.

The big benefit of this design is that you can cam it open and have full inspection or cleaning ability in seconds.

Oh, and it uses a stepper which allows you to use the Skeinforge 35 reversal module, which will allow your prints to not suck.

The spring tensioner is largely insensitive to variations in filament thickness. One less thing to fiddle with.

It uses a lever design "NEW! IMPROVED! Now with MECHANICAL ADVANTAGE!" that will push really hard on the filament, but is super easy to open and close.

This design uses the super cool 13.6:1 geared stepper motor from over at MakerGear:

In case MakerGear is out of stock, whosawhatsis reports this motor should work:

With the stainelss MK5 drive pulley
drilled out to 8mm (get these with a 20% off coupon: http://bit.ly/fUdpE9 ).

The motor shaft has a support bearing, and all four motor mounting bolts are used.

It bolts right down to the MK5 plexi bridge, using the original hardware.

It needs two 6-32 x 4" screws. I found these as part of a toggle bolt at my local TrueValue hardware store.

It also needs two springs that will fit over the 6-32 bolts. I used Century Spring Company SC-419, also from my local TrueValue hardware store.

It re-uses the 8x7x22 and 6x6x17 bearings from the old MK4.

The design is in OpenSCAD, and included in the file. There are some conditionals to create the files to be exported to STL for the builds. There is either an error in the OpenSCAD file or I am pushing OpenSCAD's limits, because it will only preview in "thrown together" mode now. Well, if you put a % on main body it previews OK. Oh, and the Z axis goes through the motor, which was dumb.

There is a little video of it building here:

History: This is kind of like a lot of different pushers. I like a grooved rolling idler with a bearing. I do not like the a flat bearing pressing right onto the round filament. I like the MK5 drive wheel. I like the 13.6:1 MakerGear stepper. The MK5 Extruder is working (this particular minute). I like the idea of having all four motor mount bolts used. I like having the end of the motor shaft supported in a bearing. Putting all that together with an over-center lever and spring tensioner gets us here.

MK5 Wade's-Style Tensioner by ScribbleJ


Yet another extruder filament pusher by jag

Accessible Wade's Extruder by GregFrost



If you have not replaced your build platform screws with flush head screws, this build is not for you. It will drive your extruder into the raised screw heads. Fair warning.

If you do not like waiting for Skeinforge, using your SD card for builds, going to hardware and hobby stores, cleaning up parts, gluing, clamping, this build may not be for you.

There is a 21-page how to build it PDF, in 53MB of high-resoultion over-documented goodness. Please use "right-click, Save As" get it on your local disk for viewing.

The ZIP file contains the OpenSCAD files and the two STL files need to build it. I used high resolution curves, which is overkill and will make the skeinforge process really slow. Maybe start it and go to lunch or bed or something. You will want to build from the SD card since there will be a lot of resolution in the curves. I built this with my "solid" profile, which is also very slow. Mmmmm . . . patience.

One note: The springs do not have to be very tight. The short+long lever design allows bucket loads of force on the filament with only minimal force on the springs. If it is squishing your filament flat, it is too tight.

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Just wanted to add that I'm still running this extruder 2 years later. It's pretty indestructible. I've presently got it mated to a Makergear hot end and it is amazing!

I'd like to point out that MakerBot is trying to patent your extruder design.

Hi, does this one work with JHead MK4b on MendelMax 1.5?
My MendelMax kit sucks, I think I have to replace several parts. This is one of it.
Can I use it with this http://www.thingiverse.com/thing:16558http://www.thingiverse.com/thi... X-carriage?

Makergear X-Carriage with built-in fan mount and duct for cooling nozzle.

Skeinforge 40 config instructions here for using this with a Kysan 13.6:1 motor, 3MM filament, .35 mm nozzle


Awesome. Ran it last night at pretty high speeds and it held up great. We had a gen3 mount originally. Since this uses a Gen4 and we wanted to use this with a maker gear groovemount hot end, we had to design and make our own mount and groove mount.

I'll post the files for the laser cut pieces to get it to mate up nicely to a Gen3 extruder cupcake ASAP.

Thanks so much for your part! Fastenal stocks roll pins and spring pins. We bought 6mm

This is pretty awesome. I had wanted to do a cam quick release but got impatient before I had a good idea in mind, I was thinking of using a bike tire quick release that I had in the scrap bin but this is much easier for others to replicate.

I think the geared stepper makes a lot of sense from a power vs amperage/heat standpoint. I wish makergear kept them in stock, I've been interested in buying one for a long time now. Have you noticed any issues with inertia in the gear train and rapid reversals? I have a small worry that the shock
load from hundreds of reversals per build might shorten the gearbox life. I have no idea if it would shorten it enough for it to become a common failure or not.

Another thing that would be nice would be to replace the springs with a flexural portion of the ABS frame. Its possible that the extra l
ong bolts and springs could be completely done away with. Fighting creep might be a challenge.

Bounty for anyone who can design an adjustable stiffness torsional spring in abs.

The gears are tiny and not spinning fast so I don't think inertia in the gear train is an issue. The main inertia will be the motor's rotor.

The first stage uses plastic gears so they may wear out eventually.

The ABS springs was one of the other ideas I was playing around with, which was keeping me from actually getting anything done.

As for availability of the motors, I have this one: http://www.phidgets.com/products.php?category=23http://www.phidgets.com/produc...

It seems to be the same gearbox design (same mounting anyway), but it's a lower gear ratio than makergear's with a higher-torque stepper, so the output torque is probably about the same, but it can go faster. They also have higher ratio versions, but those gearboxes are longer, and I'm looking at
mine and I'm already worried that the motor will hit the cupcake's frame if I try to hook it up to anything thicker than a MK5.

Update: I've been using this for a while now with the 5:1 motor from Phidgets. The motor comes within millimeters of colliding with the Z belt (this means that the ones with higher gear ratios will NOT fit), but it works really well.

I wonder if the angled design of MiZ would allow the larger motor. It was not what I was going after, but perhaps an unintended side benefit.

Maybe post a short video of your bot in operation using this? I'll link it in the description. :)

you dont need a 100x100 build platform for these. i crammed them much closer together and rearranged the parts. I can email them to you or post a derivative if you want. printing them now.

Sure - e-mail them over and I can attach the new file here.

Skeining this was taking forever, so I commented-out the $fn = 180.

You can't possibly see that kind of detail in printed parts. In most cases, the number of facets that OpenSCAD chooses automatically is pretty close to the maximum number you will be able to see in a printed part, and too many will slow it down even if you are printing from an SD card, not to ment
ion the insanely slow gcode generation with all of those extra facets.

Ya, the $fn=180 is overkill, but I figure let the resolution limit be the makerbot's limit, not how long I want to wait for the skein :) Let me know if all the parts fit well with a lower $fn setting.

Will do, but it looks like I'll have to either split it up to print one part at a time or do some tuning to get it to print. My Y axis doesn't handle prints with that much traveling between parts very well.

I had to increase my layer height so I could lower my feedrate, but I got all of the parts to print. Screw holes had to be drilled out, but that's normal. The lower-resolution circles were only visible on the M3 holes, which came out as pentagons, and would need to be drilled either way.

I'll need to wait for shipping on some of the hardware, but I'll post pics when I get it put together.

I modified the idler wheel to fit a 608 bearing and drilled out the holes to mount it. I also found some 70mm M4 screws that were just long enough. Pic posted.

This looks like EXACTLY what I've been wanting, a planetary-gear stepper extruder with a cam-lock spring-loaded bearing idler. I keep playing with different variations in my head to try to make it smaller rather than actually modeling anything, so I'm glad someone had the same idea. This will be my next print.

beautiful. Thanks for the great documentation, as well.

Not sure if I'm spending more time printing pieces, or pieces for the printer.... This will be great.

Now that's nifty! I will print this next time I need a filament pusher replacement!!

This is the 5th build, so hopefully it goes together well. Let me know if you build one or make it better. We are now putting the bot back together now with the lowrider :)

Cams and levers! Somebody finally tried Science! I've been wanting a filament clamping system like this since my first 4-bolt/spring Wade's. The fact that its tailored for the makergear setup is perfect.

This is awesome! I was thinking of making some sort of cam to tension/untension my design. You beat me to it!