Replicator 2 Extruder Alternative: Some Spring In Your Step

Posted by on Friday, February 22, 2013 in Uncategorized


The way that the MakerBot Extruder works out of the box is that there is a plunger that pushes the filament against the drive gear. We’ve shipped quite a few MakerBot Replicator 2’s into the world, and based on our data we can say that most people are having good luck with the existing design. However, there’s a bit of a sweet spot when dialing in the right plunger tension, and it can be tough to calibrate.

There are certain issues that the wrong amount of plunger tension can cause. For example, too much tension can cause a clicking sound when the end of the filament isn’t able to move past the drive gear. Too little tension can cause the filament to stop feeding altogether.

There should be a design that makes the process much easier.

Enter Thingiverse user whpthomas who came up with an improvement that has really seen some traction. It’s a great mod that makes the machine more reliable over the long haul.

Genius. We love this.

Thing #42250 “Replicator 2 Extruder Upgrade” by whpthomas, is one of these very useful designs. It’s based on an extruder mod from Thingiverse superstar emmett, who based his design on one from another star user, whosawhatsis. The basic idea of this series of designs is to use a spring-loaded arm to squeeze the filament between the drive gear and a bearing.

After extensive testing, we’ve decided that this approach is too good to ignore. We’ve modified this design to reuse the spring we already use for the build plate. We also added in a little bit of extra guidance for the filament where it enters the hot end of the extruder. Take a look on our Thingiverse page to see our adaptation of whpthomas’ great design.

We will be selling an upgrade kit that involves all the parts, including the printed part online this spring. We could have waited to tell you until we have enough to start selling them, but we decided that it would be good to tell folks about the mod.

If you have trouble with this upgrade, get in touch with our Support Team. They’re happy to walk you through some diagnostics, or you could download this design from Thingiverse and give it a try. The assembly instructions are there, too, and here’s a video to walk you through it step-by-step.

Remember, we are eager to hear your feedback, drop us a note at [email protected]!


UPDATE! The hardware parts for this replacement are available for sale in our online store. Grab them here and build your new extruder!

Tagged with 7 comments

7 Comments so far

  • Mark Durbin
    February 22, 2013 at 6:20 pm

    I printed the previous on in PLA and it melted enough on a 12 hour print that the tension was completely lost from the arm. I have subsequently reprinted the arm in Nylon which is OK. I hope this one fairs better if people are going to print it in PLA.

  • Laird Popkin
    February 23, 2013 at 6:47 am

    Mark, I have emmett’s original design in my Replicator in ABS printing for months. PLA softens at a much lower temp – not surprised it had trouble. Nylon is a cool idea – how did it work?

    I like the filament guide. MBI added.

    Will this design fit the original Replicator?

  • Mark Durbin
    February 23, 2013 at 8:25 am

    Hi Laird, it’s good to know that ABS is fine too,
    The nylon one is working well, I have run 18 hour prints with no loss of tension.
    Apparently this will work for the right extruder on a Replicator 1 (and an MK7 on a ToM) but would need to be reversed for the left extruder.

  • Mike
    February 23, 2013 at 11:43 pm

    You can order the parts for only $8.00 from MB… and then pay $9.45 to have them shipped to California. Any plans to offer more reasonable shipping on the package?

    Or a list of specs for the parts? I can surely find them locally for less than $17.45

  • Hans
    February 25, 2013 at 8:56 am

    Glad you adressed the issue and in a way and manner that suits you. The plunger design may work for some (mine did for 2 months, then it was over), but overall the spring design is much more reliable, especially with varying filament diameters. There’s always room for improvement and it’s better to share this.

    @Mike I payed 22$ for my spring alone, because non metric springs are hard to get in europe. The whole upgrade cost me about 45$, would have been cheaper from MBI. But if you can, get the parts in your local hardware store. You can at least get the specs from the design wphthomas posted on thingverse, although the srping he used got sold out 2 weeks ago.

  • Matt Griffin
    February 25, 2013 at 9:27 am

    I’ve been using Emmett’s version on my Rep1 for a couple of months as well and it is golden (printed in ABS). Been handing out compression springs and bearings to friends in town that need them, as a means to to extend the generosity from Whosawhatsis who gave me a pair of bearings and compression springs last year at Maker Faire New York to try out his original mod around the time most of the hardcore 3D printing folks with MakerBots went to a spring-loaded filament tensioner.

    Looking forward to trying the MakerBot variant on Adafruit’s Rep2! And am curious about the whole slew of mods whpthomas installed in his Rep2. Now filaments of slight diameter variances should print beautifully! Or at least at all. 😉

  • PaulMakesThings
    May 6, 2013 at 5:42 pm

    Looks like I’ll be printing the upgrade in PLA, since that’s all I can run without the upgrade, then hoping it lasts long enough to print the upgrade in nylon.


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