Direct drive extruder for Wilson or Prusa i3 rework

by mrice, published

Direct drive extruder for Wilson or Prusa i3 rework by mrice Oct 15, 2014
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This is a direct drive extruder that I designed specifically for 1.75mm filament extrusion on my Reprap Wilson.
How to use:

  • It will connect to the standard X carriage (also X carriage for the Prusa i3 Rework by eMotionTech) using four M4 x 20mm screws and nuts.
  • Uses a MK7 drive gear (probably MK8 too, but I've only been using MK7)
  • You will need 3 M3x30mm screws to attach the motor (one is also used to support the hinged lever).
  • The Idler bearing is a 624RS bearing, held in place by a M4x20mm screw and locknut.
  • For the spring, choose a 1" (uncompressed) spring with decent (~10lbs/in.) tension.
  • Through the spring, use a M3 x 50mm screw with a M3 nut going into the slot on the extruder.
  • The hot end mount is JHead compatible and will also work with hot ends like the e3d v6. Two M3 x 30mm screws (probably 20mm or longer is ok) with nuts are used to attach the clamp piece to the outer side of the hot end. A fan mount is provided for a 40mm fan, for which you'll need another M3 screw and nut to mount and four M3 screws with nuts to attach the fan.
    Also included is a "key" that you can press over the end of the motor so that you can manually turn the extruder. It only works with D-shaft motors.

There's also an assembly video for this extruder now on YouTube:


UPDATE Jan 22, 2015 I've altered the extruder body and idler a little bit to add a slot for a second tension spring. This helps keep the idler from pushing more flexible filament off to the side, where it can slip off the drive gear. I've also moved the filament path up a few mm closer to the gear for a similar reason.

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Hi, i printed the original one and the tensioner is broke now. I lost the original stl files and your original tensioner isn't here. Where can i find it please? Thanks for your design, it's a great extruder.

And when i try to work with the github file, sketchup said me that it's not an sketchup project.

hi i've installed this fine extruder on my p3steel v4 xl .
how many e steps did you configured on marlin?
thank you

i was able to repair the file with 3D Builder...

Is there a link to the zip-tieless x-carriage used in the picture?

Your 3D model of the e3d might be incorrect, as this is the hot end that I use with this extruder.

Dec 26, 2015 - Modified Dec 26, 2015
DeathmannX - in reply to mrice

Ouh i see, the bowden is on top a bit longer:


Is it possible to make for this extruder a modification for this?

Hi, I downloaded the files. It is having lot of errors. I tried to fix it with Netfabb basic, but only 90% successful. Anybody got success in this? Or any other way is there to fix the errors?

Jun 14, 2015 - Modified Jun 14, 2015

could you please upload the original file?... I want to make some modifications on this design to fit on a prusa I build. Thank you in advance!
I would like to use the UPDATE Jan 22, 2015 version with two springs

mrice - in reply to

norarth - you are welcome to edit from the original, I designed it in sketchup. The files are located here:



I can confirm the model here in thingiverse is definitely damaged (holes with jagged artifacts). The one in github is perfect. Thanks.

thanks a lot!

Jun 7, 2015 - Modified Jun 14, 2015

Thanks! I'm printing one right now in black PLA. My extruder is an all metal, I hope will not have issues printing it in PLA. Only one question, your stepper have the same interaxis for the screws as the nema 17 stepper?

mrice - in reply to

My motor is a NEMA17, so I think the answer is yes.

Ah, ok... my nema 17 looks different, is the short one. I've been thinking, the short nema17 have enough power or it will miss steps because of low torsion?

hi , what material and setting did you use to print the parts to make the Direct drive extruder.

I print them in PLA at 50% infill and 1.5mm walls.

Has anyone made a MK8 version of this? There's big difference in diameter between MK7 and MK8...

hello how can I change the filament diameter from 1.75 to 3 mm thanks

After a little bit of tweaking I have this direct drive working pretty good on my newly built reworked i3.

It's running an E3Dv6 and I drilled out the extruder body to run the ptfe tube all the way up from the hot end to just below the mk7 gear. I also sourced springs from Home Depot via a multi pack of springs. After a few tries of the different springs, I ended up meshing together two lighter weight springs to provide enough tension.

I've run several multi-hour prints without a single issue. The stepper is running cool and has had no slippage.

With too much tension though, the filament will sometimes slip to one side or the other of the bearing. Also, while the body printed out just fine with everything perfectly fitting, I did find that I had to slightly sand the bearing holder pivot point to fit into the slot.

I had a similar problem on one build of the extruder, it seemed to be particularly a problem on more bendy filament. I have updated the model to add a second spring on the other side of the idler bearing so that the pressure is kept even and the filament can't get pushed to the side and it seemed to work great on the machine I tried it on. I'll get that updated model up here tonight so you can try it if you'd like. The right-side spring is in the same location as before, so it can still be used with one spring if desired. I haven't experience a fit problem with the idler fulcrum, but with the second spring it wouldn't be a problem to make it a little narrower (I had been trying to keep it as wide as possible so that the idler couldn't twist). I'll make that mod too before I post the updated version.

Look forward to trying the revised file. Know what you mean about the twisting of the tensioner because on my 1st print I'd taken too much material off at the pivot point and it'd twist. I cut it out with netfabb and the 2nd print was fine.

I was thinking if you could square up the part of the extruder body against the stepper on the right side where the tensioner slips in (like the left side), this would give it the additional support and eliminate the potential for twisting.

I would like to have the right side squared off, but it would create an overhang that wouldn't print without supports. I suppose a removeable support could be added, though. With the second spring perhaps it won't be necessary. Anyway, I've uploaded the changed version so check it out and let me know how it works out for you. Thanks for the feedback, too!

Dec 30, 2014 - Modified Dec 30, 2014

prompt where to take X-carriage?

You can use my http://www.thingiverse.com/thing:586636 X-carriage, it works well with this extruder.

Prusa i3 Rework X-carriage with additional holes for Wade's extruder

I love this and already buying the parts I am missing as the extruder for the Rework has always given me a headache.

Would you be so kind as to link, or tell me, where you purchased that sping at as all I can find are wimpy ones around the m3 size.

The springs I have been using are from McMaster, part number 9657K76. I get the M3x50mm screws from the same place. For those, I like the hex-cap screws because they are not fully threaded, so the spring glides better on them. That part number is 91292A026.

Shipping must be murder for such a little order. Yeah, I like those screws as well for the same reasons too.

Thank you.

Oh, yeah I use socket cap screws for everything these days and just like you I buy 30mm for everything and use them for everything unfortunately I have to use stainless as plain black oxide metal screws rust here within a week to two weeks as I found out. :/

Has anyone tried printing a mirror image for dual extrusion? Any gotchas?


This looks like a great extruder, is it possible to get the source? I would like to modify it for another carriage. Thanks!

Nov 23, 2014 - Modified Nov 23, 2014
DarkAlchemist - in reply to gumpwa

I am migrating over to this, as you know, but I can't find a good spring and M3x50 is a bear to find.

Which carriage are you modifying for/to?

I want to use this on the Lautr3k I am building.

Nov 7, 2014 - Modified Nov 7, 2014

That key is only going to work if the motor shaft is long enough. I don't think the motor I have has a long enough shaft, and I'd have to file a "D" profile on it anyway, which I will at least for the part under the MK7 set screw.

BTW what is the spacing between the two screws that mount the hot end retainer? They might be far enough apart to fit the mounting holes for the 40mm fan that comes with the ALUhotend. (If not, I'll make an adapter plate to mount the fan to those screws).

looks like at least one of the screw holes to mount it to the carriage is blocked by the motor so you might have to mount the body and then assemble it? Is there any filament guide below the MK7? That is required for certain filament such as Ninjaflex, though I guess one could always drill out the hole under the MK7 a bit and put in a small piece of teflon tubing.

Oct 15, 2014 - Modified Oct 15, 2014
mrice - in reply to scharkalvin

The fourth mount hole isn't blocked, it just appears that way on the picture (although you'd want a pair of needle-nose pliers to hold that nut in place unless you have tiny little person fingers). There's a guide ~2mm through the body under the drive gear, but I think you're right about drilling it and inserting a short piece of PTFE if you wanted to really pimp it out for flexible filament.
*edit: if you did insert a PTFE guide above the hot end, it would be about 22mm long.

What kind of hot end do you have on this one?

I've verified that an ALUhotend fits nicely there too.

It is a JHead, Mark V-BV

any picture to show the real installation?

Added photos!