Replicator 2 Extruder Upgrade

by whpthomas, published

Replicator 2 Extruder Upgrade by whpthomas Jan 14, 2013


This extruder upgrade for the Replicator 2 replaces the Delrin plunger with a pinch roller. Using the spring specified in the parts list below, this pinch roller provides about 60N of force on the filament, which provides enough driving pressure on the filament, in combination with the stepper drive gear to prevent stripping.

Unlike other designs, this one uses a pin style bush on which the pinch arm rotates. This provides a large lower friction surface for the pinch wheel arm to rotate on, and allows the mounting screw to be fully tightened so there is no chance of it working loose.

I have extensively tested this design, which has evolved through numerous iterations, and I have also tested several different springs. With the specified spring I can hold the drive gear with my thumb and pull hard on the filament without it stripping, and its done numerous unattended prints with troublesome clear PLA filament - so I can confidently say __it works__.

###UPDATE (Mar 4th 2013)
In v7 I have added a filament guide slot to the bottom of the backing plate. I added a spring channel to hold the spring in place and stiffen the backing plate. I redesigned the arm geometry to make it pivot better - compressed and uncompressed. I altered the pin so one side now holds the base plate down against the stepper motor.

This extruder upgrade was designed using an ACIS solid in Shark FX/ViaCAD (vc3 file included) so will behave well with Makerware, ReplicatorG and skeinforge. There are also STEP files that can be imported into other CAD programs.

Because a few of you have asked - Paypal donations graciously accepted - whpthomas at yahoo dot com

Recent Comments

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Great product, but could you please add pics of the newer versions of the upgrade. I want to be sure that I am putting the upgrade on correctly as the printer is school property, not mine! I have tried everything to fix this printer, and the printer just wont work! the printer seems to not be catching filament because when I print stuff (or at least attempt to!!!), the bottom of the raft looks like it extrudes a normally, then it decreases in amount, then it works for about an hour, then it fails completely! I know it is not a clog because when I push down on the filament, the motor catches it again and takes 5 seconds of continuous pulling in order to come out of the nozzle. Hopefully, the printer should work tomorrow with 60N of force on it!!!!!. If anybody has experienced the same problem where the printouts don't extrude enough and eventually don't catch any more, PLEASE TELL ME HOW TO FIX IT, I AM ABOUT TO THROW THIS PRINTER OUT OF THE WINDOW AND IT'S NOT EVEN MINE TO THROW!!!!!!

Thank you for your replies
Has been upgraded with new accessories.
I would like to ask you now with the extruder won't plug throat how to do.
The 3 d printer market

You should design your own items if you want to sell them. But these printers now come standard with an extruder like this so there wouldn't be much of a market anyway because everyone already sells them on ebay anyway and those with delrin plungers probably already did the upgrade anyway.

More from 3D Printer Extruders

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Print and source parts, disassemble extruder, upgrade and reassemble, enjoy life 3D printing.

**Now that the Replicator 2 ships with an injection moulded version of this extruder upgrade, much of what I have stated below is moot. I hope the current crop of the Replicator 2 owners run into less problems than we early adopters experienced.**


I have come to the considered view that the design of the Delrin plunger drive arrangement on the MakerBot Replicator 2 is defective. It uses a grub screw seated on a rubber O-ring to provide pressure on the filament to keep it in contact with the drive gear (see picture). The problem with using a rubber elastomer as a spring is that it will tend to seat-in over time, loosing some of its 'springiness' and requiring adjustment. However on the Replicator 2, adjustment of the plunger grub screw also requires the extruder unit to be partially disassembled. Now that the blower fan uses self-tapping screws, it doesn't seem like a good idea to be constantly removing and inserting those screws into plastic threads. More to the point, the amount of spring travel provided by the rubber elastomer is not sufficient to accommodate variations in filament diameter from 1.7mm to 1.8mm and maintain even drive pressure. Unfortunately some rolls of filament contain this degree of variation within the roll. In my experience, clear and white PLA are particularly troublesome. Failure of this plunger mechanism to maintain consistent drive pressure during printing leads to failed prints, wasted filament and printer downtime.

The MakerBot website claims that "Replicator 2 has been engineered with the professional designer in mind". I am a professional product designer, and I do not feel that the Replicator 2 Delrin plunger drive arrangement, with these inherent problems, fulfils this usability objective.

So I set about to design an upgrade that used parts which were readily available, an upgrade that could be printed reliably, and one that worked as expected.


I printed the Mk8-Upgrade-Base and Mk8-Upgrade-Arm using my 100 micron ReplicatorG profile thingiverse.com/thing:39050 with the following settings:

Infill 100%
Layer Height 0.15mm
Number of shells 1
Feedrate 80 mm/s
Travel Feedrate 150 mm/s

Make sure you use a PLA that prints reliably on your machine. However, some more experienced Makerbot operators are recommending printing these parts in Black PLA because black has a higher melting point. Nevertheless, solid parts printed in Black PLA are prone to warping, so I have added ear tabs to hold them down on the build plate better. Seeing these have 100% infill, its not a bad idea to print these bit leaner than you normally would by increasing the filament diameter in Print-O-Matic by +0.03mm.

Once printed, ream out the holes on the arm with an M6 and M8 reamer (if you have them) or similarly sized drill bits. This will ensure the parts mate without friction. You can ream out the filament feed hole with the second smallest hex wrench provided with your Replicator 2.

There is also a snap-off support on the bottom of the Base that is there to act as a bridge to support the printing of the recessed area. Carefully use a sharp knife to cut this off and use a small flat file to clean the area of any loose strands of filament. There is 0.5mm clearance here so it doesn't need to be perfect.

I printed the Mk8-Upgrade-Pin using my 100 micron ReplicatorG profile with the following settings:

Infill 100%
Layer Height 0.1mm
Number of shells 1
Feedrate 80 mm/s
Travel Feedrate 150 mm/s

If you don't have a set of metric reamers or drill bits I recommend printing two of these Pins and use the first one with a pair of pliers to ream out the holes. Insert it into each hole separately and twist it around, the flat edge on the pin will tend to act like a reamer and clean out the hole for you. I have tested this approach just to make sure it works.


You will need a 3/8" x 1-1/8" x 0.041" compression spring.

This is available from Home Depot (see photo). It is the middle sized one in the pack but check the dimensions on the pack to ensure you buy the right pack. The same spring is also available in the US at True Value hardware stores.

It is also made by Century Spring Corp. The model number on a store bought packet is C-624, but on the website a similar spring has model number on 519. Phone 800-237-5225

The C-624 has been spotted on Amazon here
and on eBay

If you live in Australia the C-624 has been sited in Bunnings Hardware Stores.

Sodemann Industrial Springs has a metric spring that provides a similar 30N of force, its model number is C03600401120S.


623Z - 3mm ID, 10mm OD, 4mm width

You can get these on ebay, some hobby shops, and small industrial part suppliers. In the US you can pick up one at your local Fastenal store. In Australia, they are available online from BilbyCNC bilbycnc.com.au

This bearing has also been spotted on Amazon here


You will need two M3 x 10mm counter sunk hex head screws, just like the ones Makerbot uses to hold the plunger assembly on, only shorter. If you can't get hex head, M3 phillips head countersunk screws will also do. If you can't get 10mm lengths, then an 8mm and a 12mm will suffice.


1) Unload the filament form your extruder and wait for it to cool down. Wait until the heat-sink fan stops spinning.

2) Turn off the power to your Replicator 2.

3) Unplug the stepper motor and unscrew the two stainless steel hex head cap screws on the front of the heat-sink fan using the second biggest hex wrench provided. This will allow the extruder stepper motor and plunger assembly to be removed.

4) Using the second smalest hex wrench, unscrew the Delrin plunger assembly from the stepper motor. Keep one of the hex head screws for the upgrade, the remaining parts can be placed in a Ziploc bag for safe keeping.

5) Make sure the base plate and parts all fit together - sand and file as required. Make sure that the holes in the plate and arm have been reamed so the pin can be inserted with moderate force and has a firm fit (see instructions above for details).

6) Use the 10mm (or 8mm) counter sunk hex head screw to mount the Base plate on the stepper motor (see picture). I orientate the wiring block on the left hand side because I think having it on the top is rather unsightly.

7) Push the bearing into the slot in the arm and use the 10mm (or 12mm) counter sunk hex head screw hold it in place.

8) Push the pin into the pinch wheel arm, and mount it onto the base plate. Now take the long counter sunk hex head screw left over from the Delrin plunger assembly and insert it into the hole in pin and tighten until snug. I recommend that the flat edge of the pin be orientated so its facing away from the drive gear wheel (see photos) that way all of the load is spread evenly against the curved face.

9) Compress the spring and insert it into place.

10) Position the upgraded assembly on the back of the extruder and mate it with the two stainless steel hex head cap screws, then gradually tighten using finger pressure, making sure not to cross thread. They just need to be snug, so don't over tighten them.

If you live in a hot tropical climate, consider making a gasket out of some card to isolate the stepper from the cooling block (see photo).


You can just use the preheat menu now if you like.

To load, grab the extruder with your right hand and supporting it underneath with your fingers, press down on the pinch wheel arm with the tip of your thumb. This releases the pinch pressure. You should be able insert the filament right down into the extruder tube, and see it oozing out the tip.

To unload, wait for the preheat to reach 230c, then do the same thing as above to release the pinch pressure and pull the filament out.


Check your packing density in skeinforge Dimension is 0.97 ~ 1.0 then measure and update your filament diameter in Print-O-Matic, it should be 173 +/- 2. You can also download my 100 and 200 micron skeinforge profiles here: thingiverse.com/thing:39050

Finally if you are still struggling with stubborn PLA filament, try a drop of olive or canola oil on your finger, lift up the filament feed tube on your extruder and rub a light film of oil over the first 50mm ~ 100mm of filament. That should do the trick :)

I had wondered at first if vegetable oil would effect the print strength, but I see no evidence of this. So I look at it like this, PLA is like high-tech cheese - if you melt cheese in a pan with oil, the oil and cheese separate, and the cheese melts and bonds together - I figure the hot PLA and vegetable oil do a similar thing - the oil ( and it is only a very small amount we are talking about) moves to the outer surface as the filament bonds due to the oils lower viscosity and the changing surface tension.

From what I understand these vegetable oils only burn above 246c ~ 266c (See en.wikipedia.org/wiki/Smoke_point), so while it may be adding some sort of a patina inside the heating chamber (much like you season a cast iron pan), it shouldn't cause any burnt deposits that might gum up the system - but be cautious, I would apply vegetable oil very very sparingly, and only when you think you need to.


If your extruder stepper motor should happen to overheat in 45 degree c summer heat, it may cause the PLA arm to soften and bend out of shape. If this happens to you, don't be alarmed there is a quick remedy. Remove the arm from the stepper motor and holding it by the bearing screw, dip it into a cup of boiling hot water for about a minute (make sure not to wet the bearing). Once soft, bend the arm back to how it should be and allow to cool, then re-install - good as new!


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WEDimagineer on Apr 17, 2014 said:

Great product, but could you please add pics of the newer versions of the upgrade. I want to be sure that I am putting the upgrade on correctly as the printer is school property, not mine! I have tried everything to fix this printer, and the printer just wont work! the printer seems to not be catching filament because when I print stuff (or at least attempt to!!!), the bottom of the raft looks like it extrudes a normally, then it decreases in amount, then it works for about an hour, then it fails completely! I know it is not a clog because when I push down on the filament, the motor catches it again and takes 5 seconds of continuous pulling in order to come out of the nozzle. Hopefully, the printer should work tomorrow with 60N of force on it!!!!!. If anybody has experienced the same problem where the printouts don't extrude enough and eventually don't catch any more, PLEASE TELL ME HOW TO FIX IT, I AM ABOUT TO THROW THIS PRINTER OUT OF THE WINDOW AND IT'S NOT EVEN MINE TO THROW!!!!!!

xinchuangwangluo on Dec 9, 2013 said:

Thank you for your replies
Has been upgraded with new accessories.
I would like to ask you now with the extruder won't plug throat how to do.
The 3 d printer market

xinchuangwangluo on Dec 8, 2013 said:

Could you tell me how to sell this. thank you!

falken76 on Dec 8, 2013 said:

You should design your own items if you want to sell them. But these printers now come standard with an extruder like this so there wouldn't be much of a market anyway because everyone already sells them on ebay anyway and those with delrin plungers probably already did the upgrade anyway.

xinchuangwangluo on Dec 8, 2013 said:

Could you tell me how to sell this thank you!

xinchuangwangluo on Dec 8, 2013 said:

HI I am
Chinese.Do It Yourself 3 d printer enthusiasts. Very much hope to communicate with you together . At the same time also hope to get your help, thank you

xinchuangwangluo on Dec 8, 2013 said:

How to read this

3dcgmodeler on Jul 18, 2013 said:

thank you

eyesontheball on Jul 11, 2013 said:

Anyone know the specs of the hex head screws from the Delrin plunger assembly? I took mine off months ago and can't find them, but I still want to install this upgrade! Been using the Makerbot version upgrade and it starts to suck after about 50 hrs of printing! This one looks to be better. THANKS!

refreitas on Jul 9, 2013 said:

having a really hard time. I think the feeder is working as it should, but I
started hearing some clicks as I had never heard before. Also, in each click, I
can see the (I don't know what to call it) "sprocket" hesitating at
each click. Not using this exact same upgrade, as I had a hard time finding a
good replacement for the spring, but the same principle. Still using the
default medium profile, totally unchanged. Could this be caused by too much spring??
to little?

confused, so I will try the other issues already mentioned, although I’m not
sure how to address some of those issues, such as packing density, or the filament
diameter (what is the print-o-matic?? I only use the makerware!!??

serrated on Jun 21, 2013 said:

i printed this at 0.2 (wasn't able to get 0.15 successfully on my stock replicator 2) and wasn't able to get it to work. sadly the stock plunger worked better.

i think it's due to the arm assembly not rotating freely when it's installed to where the spring wasn't able to put all its force on the bearing. could this be from my print coming out too thick, or do you think i mounted the stepper motor/heatsink/fan too tightly?

I'm reprinting at 0.16 right now, so hopefully that will work better than my first attempt.

jaypom on Jun 11, 2013 said:

OMG... so THIS is how my Replicator 2 is supposed to work!!!! THANK YOU!!!
Bought the screws and bearing on Amazon - Works perfectly....
I was so frustrated with the original setup, this is sooo much better. I'm going to go re-print most of what I've done for the past 3 months!

Badjano on May 28, 2013 said:

I'm from Brazil and we have mm as default measure unit, and I brought the spring dimensions in inches as you provided to the spring store but I think they gave me the wrong spring, would you mind giving me the right dimensions in mm for the spring? thanks! and excuse my primitive english.

d_goodman on May 10, 2013 said:

Can you please make one for the other extruder? It works really well but I have a dual. Shouldn't take too much time, just mirror the arm and base Thanks!

gandi800 on May 13, 2013 said:

You can always mirror them yourself. In most software you simply hit mirror under edit.

rensole on May 7, 2013 said:

This is awesome, I only have one problem.
My servo is getting extremely warm.
So it basicly melts the pla once it gets the the bearing and squishes it so it loses grip.
What would you advise me to do ?

nickdisney on May 7, 2013 said:

that doesnt sound like an issue caused by this... is your extruder fan running? how high do you have the temp set to? 230 is usually sufficient for pla...

AllDigital on Apr 27, 2013 said:

This plunger is awesome! I had problems early on and I swapped out the delrin plunger hex screw for a bearing screw. That worked for a while (not sure why), but then I lost a lot of extrude pressure after a big failed print.

So, I printed and parted this plunger. It was definitely superior, but I still had problems with downward pressure. It turns out that my drive gear was also slipping. This is another REALLY bad design by Makerbot. The flat section of the drive shaft does not reach the grub screw, so the drive gear will eventually start slipping. I modified the shaft by using a Dremel to flatten the shaft a bit further.

The combination of the shaft mod and the new plunger are golden!

Saroyan2 on Apr 26, 2013 said:

Thanks so much for this upgrade, I have one quick question; The base plate support isn't "snapping" off. I assume this hole should be clear based on all the older upgrade pictures, I'm guessing I'll have to drill this out, any thoughts?

jprikkel on Jun 30, 2013 said:

Yes, the circle snaps off.

ark19 on Apr 25, 2013 said:

Kept reminding myself to print the V7 as a spare.... kept postponing until my current Replicator 2 Extruder Upgrade warped :( Used your method of softening the PLA back to shape with hot water and managed to get it back up. So now i'm printing V7 as a replacement. Once it's done, will print another set as spare. Lesson learnt! Hey Whpthomas, the V7 looksreally slick! ;)

kwalus on Apr 23, 2013 said:

Thanks, this is the best upgrade for the rep 2, it has really changed the experience for me. The other thing that made a huge difference was switching to a glass build plate: http://www.thingiverse.com/thi... I could not live without these now. Well done!

ttturner68 on Apr 20, 2013 said:

This is ton better solution than stock? Why hasn't it been hard tooled. I think talc or glass filled nylon would be awesome for this application. I am going to see how cheap a small tool could be made from my Asian sources. Need to be tooled

scvette on Apr 8, 2013 said:

-----------Replicator2 Extruder Upgraders Update----------

I am pleased to announce the availability of complete ready to bolt-on Extruder Upgrade Kits now in high strength ABS.

Still, only $30 including First class shipping(lower 48)

These ABS kits are proving to be all that the PLA kits are, but better in strength and heat resistance.

These kits are like the original PLA kits except I now include all bolts and hardware so there is no need to reused the axle screw from the delrin plunger assembly.

It is a truly five minute upgrade and I can have it in your hands next day by 3pm.

All pricing and contact information can be found here.

or contact me directly at taylorstull (at) giis.net for quick delivery.

mitchell985 on Apr 7, 2013 said:

this work great all makerbots need this it also lets me print anything with no problems

Nidhoggr on Apr 1, 2013 said:

Would this build apply for the Replicator 2X as well?

scvette on Apr 8, 2013 said:

This kit does not fit the 2X. The extruder drive gear on the 2X is spaced 5mm farther out on the shaft from the stepper motor than the Rep2. The 2X extruder parts also run at a much higher temperature than the Rep2 and thus melts PLA parts within 45 minutes. I tried it... :)

robaktime on Mar 31, 2013 said:


I haven't received my replicator 2x yet so I am familiarizing myself with the product 's
features and limitations during the next eight weeks. Your videos are right on and after viewing this little improvement it's clear you have a depth of understanding
that far exceeds the norm. I appreciate your sharing it with us.

morris on Mar 28, 2013 said:

Is there a photo of the snap-off support on the bottom of the base that is there to act as a bridge to support the printing of the recessed area which shows how it looks before and after it is removed? I'm a little confused with the most recent version of this part.

sfernald on Mar 21, 2013 said:

Will these fit the replicator 1? If not, is there a design out there for the replicator 1?

wdelarme on Mar 17, 2013 said:

Bearings here at mcmastercarr.com 7804K128

LloydRoberts93 on Mar 17, 2013 said:

my printer started clicking pretty much straight away when i opened it! i am in the UK however and bought my printer from america and had it imported. sucks that i havent really had a decent print yet. a couple went well but they stopped before they could be finished for no reason.

a side note - does anyone know where i can get the parts i need in the UK? i.e. the spring, bearing etc etc, or anyone could give me a detailed list/name for each part so i can look for them myself. i am completely new to 3d printing too. thanks guys

slepcat on Mar 16, 2013 said:

Thank you for great work. This upgrade are popular in Japanese community too!

jelos98 on Mar 11, 2013 said:

I suspect this is the right spring pack on Home Depot. Right brand, and the two safe working load limits match: http://www.homedepot.com/p/Eve...

kwalus on Mar 6, 2013 said:

This is an outstanding upgrade, thank you!

funbart on Mar 2, 2013 said:

Thanks for this one again. It's usable for the replicator 1 as well. For T1 just mirror the design.

Maybe three suggestions:

- print a spare one, as you can't print when it's broken with a Rep 2. With a Rep 1, you still print the replacement with the other extruder of course.

-about the Gasket for warm climates. I have the feeling it's a good thing to use anyway to insulate the stepper motor from the heater block, but you have to adjust the drive gear on the motor shaft to be sure the drive hear is lined up with the rest of the assembly.

-I think the screws and bearing are commonly available. For the spring I bought 10mm spring in the length of 1 meter (4 dollar) By adjusting the length cut off, you have some influence on the tension applied.


falken76 on Feb 27, 2013 said:

Will this work in PLA? I've read that PLA can't hold the temperature the same as ABS and this would melt? Is that true? If that's the case, where can I purchase this assembled in ABS since I purchased a rep 2 and I can't use ABS. (Did I make a mistake, this damn marketing, it looks like I could have bought a rep one and made it alot better for less with upgrades)

whpthomas on Feb 27, 2013 said:

Almost everyone is printing them in PLA - mine is PLA and holding up quite OK - just print in black if you can and avoid white.

pringle on Feb 27, 2013 said:

Can I print this in ABS? Im unable to print white PLA consistently. Really want to print some bigger pieces with PLA though.

whpthomas on Feb 27, 2013 said:

I know its been successfully printed in nylon so I am sure ABS would work too.

Lubebosch on Feb 27, 2013 said:

Can this be fit to a Rep 1?

whpthomas on Feb 27, 2013 said:

As far as I know yes - it will work on any Mk8 extruder - just scale it by -1 to create a mirror for the other side if you have a dual-extruder.

Lubebosch on Feb 26, 2013 said:

Could this be fitted to a Replicator 1 last generation?

jasonm621 on Feb 25, 2013 said:

Does this work on the Replicator 1? If not what does?

whpthomas on Feb 26, 2013 said:

As far as I know yes - it will work on any Mk8 extruder - just scale it by -1 to create a mirror for the other side if you have a dual-extruder.

pomodesign on Feb 23, 2013 said:

Works like a charm! I do hope MBI compensates you for your design, since they are sending out something just like it for those of us who filed help tickets for feeding issues. Here's the video link they sent me. http://www.youtube.com/watch?v...

Kallipigous on Feb 21, 2013 said:

A quick word of warning. I had my arm snap down the middle this morning (wasn't' pushing any harder than usual so I'm not sure why). It's fine because I had a first attempt still lying around I could use to print a replacement. It's worth printing off a couple though the first time so that you have backups. Otherwise you have to reassemble the original one just to print it off.

whpthomas on Feb 21, 2013 said:

Haven't experienced this - but have had one bend from overheating - so very prudent advice. I have an older version sitting on the shelf as a backup.

falken76 on Feb 20, 2013 said:

I have not even received my printer yet and read the horror stories on google, I can't believe I have to print up upgraded mods and install them in order to ensure that an item I spend over $2 grand on will work as intended. Thank you so much for making this, further reading also suggests that makerbots support would take days and weeks to answer questions with unhelpful 1 sentence responses. This community is awesome.

BrokenLegGuy on Feb 15, 2013 said:

Thank you. I can finally use my Rep 2. I did do a little improvising on the spring though, I couldn't justify paying $5 - $10 for one spring but that's the cheapskate in me. Thanks again.

vector2michael on Feb 14, 2013 said:

Awesome upgrade. It is working incredibly well for me. Thank
you so much for contributing this to the community! Really awesome.

rgremill on Feb 14, 2013 said:


Installed this upgrade last night (got the complete kit from scvette!!!)

Before I was never able to print out anything using the transparent blue filament without many many attempts. After the upgrade I got some of the most beautiful printouts since the very beginning.

Before, the calibration cube looked like a stack of pancakes. Now it prints as one solid block.

Thank you so much for designing this. My bet is that all Replicator 2 owners will have to install this at some point.

Gozeeta on Feb 13, 2013 said:

hi whpthomas!

I was wondering, would you recommend sanding/filing the contact faces between the base and the arm smooth? i did and may have actually increased the friction, but before i print another set to test i'd like to hear your thoughts! thanks for making this thing!

Scott216 on Feb 13, 2013 said:

I printed out the parts and will be installing them soon. Once I do I'll probably do it again at a higher resolution. I used Makerware medium resolution. It was a pain to get the pin to fit. I was looking at McMaster Carr for a shoulder screw and they have one that might be a good substitute for the pin (P/N 90278A317). It has a M3x4mm thread, 4mm dia x 10mm long shoulder and 6mm x 3mm head. The base and arm would have to be modified to use this pin.

JRD on Apr 1, 2013 said:

I agree. This kit would be considerably improved with this seemingly minor change.

scvette on Feb 11, 2013 said:

Replicator 2 upgraders!
I have these preFit assembled extruder upgrade kits version 3 ready for same day shipping at the very low price of $30 shipped(lower48) or +$6.55 international first class.

It is hard or impossible to source all the parts and get it printed, cleaned, assembled and properly fit before I can have it in your lap for the ultimate 5 minute upgrade that it is or for less money.

Don't spend 50 bucks on Ebay for a kit that is just a bag of parts. I spend a lot of time hand fitting the pivot pin for a tight accurate pivot point by hand scraping the small ridges down. Drill out the pin holes and filament guide hole for a nice round smooth hole. I then preFit each assembled kit to my personal Rep2 to ensure a clean tight fit on the extruder motor.

Am I making money on these? Not if I have to include any of my labor time on each one.
Am I here to help the Makerbot Operators Group keep printing cool stuff? You bet!

Here is a link to the Group buy thread at Makerbot Operators
or reach me quick at taylorstull(@)giis.net
Thanks again to whpthomas for the class act piece of hardware that this upgrade kit is!

ark19 on Feb 11, 2013 said:

Hi Whpthomas,
thanks for this design that replaces the original plunger design!
The original plunger design is very amatuer when compared to a design which uses a bearing. Posted a pic of my orange print :) Cheers!

Rassilon on Feb 11, 2013 said:

OK after much hassle trying to source the bearing (it came as pack of 2
pairs of bearings for RC helicopter) at a cost of $7.99 at Action
Hobbies in Calgary, the screws I got a wide selection of M3 screws 8mm -
1.6mm. I think the bearing screw could be a 10mm rather than 12mm

I assembled the parts as directed (yes it does look
better with the stepper rotated), cut down my over long spring.
Reassembled (the fan guard appears to be slack now :/) it actually took
me a dismantle to ensure the filament was going into the heater.
Levelled the plate & applied olive oil (no corn oil to hand) lightly
to the first 20mm

My first print of my own designed part went to
air very quickly, but a friends design of the same part that airprint I
thought at 3% on Friday (pre-mod) is now zipping along at happily

This mod has already proven it's worth & thus far has
given me the product I thought I'd bought in December. Next thing of
yours I'm going to try is the Snap on dial indicator.

cloakofcarrot on Feb 10, 2013 said:

After two weeks or so of use, my replicator 2 failed with a
disastrous failed print on the first long print that I attempted (the
ones before had been relatively short so I could monitor them) that
resulted in the creation of a PLA ball that destroyed the kapton tape
around the extruder.

reading through the forums and watching the video on the support site, I
was able to exhume the extrude from its PLA tomb

without further damaging the heating and temperature sensor
wires by disassembling the extruder unit, and carefully using a
soldering iron to melt away the PLA that did not come off with the
extruder heating procedure.

I was able to get the unit working
again, and by following the suggestions on the various sites regarding
tightening the plunger, and increasing the temperature of the extruder
to 240, I have been able to increase my print success rate.

did contact support regarding this, but after waiting several days, the
only suggestion they made was to give me the support phone number and
suggest I order a replacement part.

I will follow through on
that, but I have also printed out your replacement part and will be
installing it as soon as I get the replacement extruder to prevent this
sort of disaster from happening in the future.

By doing some
experiments with the temperature and the length of print it does appear
that the PLA ball formation is related to the PLA material not feeding
cleanly. Once the printer misses, the PLA starts to form 'curls' and
'fuzz' that then stick to the sides of the extrduer as it passes over -
gradually forming a ball around the extruder.

Increasing the
temperature and the plunger adjustment has so far stopped that from
happening, but I still have consistency issues with prints taller than a
5-10 cm or so - fracture planes appear to form in the prints beyond a
certain height.

By watching the unit for an extended period of
time, I have observed that using the makerware print software seems to
delay the second fan until part way into the print. Once that fan kicks
in the extruder temperature suddenly drops by about 4-5 degrees
(probably would be less if the kapton tape and insulation were still
present). The sudden extra blast of air also seems to cause the PLA to
curl and pull away from the bed as well. If there are feed issues with
the PLA when the second fan kicks in, that also seems to start the
'fuzz' effect, which then results in a failed print.

The second
fan seems to run right off the bat with the ReplicatorG software, which
seems to limit the curling effect more - I am guessing because there is
not a sudden change in temperature part way into the print.

I am
not sure what the behaviour of this fan is supposed to be, but it seems
odd that it would be different using different printing software.

- hopefully I can get a new extruder and get back to just enjoying the
unit instead of having to troubleshoot issues. Based on what I have
read, your modification will allow me to do that - so I look forward to
trying it out. I am having trouble finding the spring and the bolts
though (amazon.com wont ship to Canada) so if someone in Canada knows
where I can order them from please let me know. Thanks,
Mike M..

whpthomas on Feb 11, 2013 said:

Have a search on the google Makerbot operators group, there are some guys in Canada that had excess parts to sell.


hcseanwu on Feb 8, 2013 said:

Willing to buy a kit for the parts! Since I live in Asia, it is impossible to find the parts with correct dimensions. If guys are willing to help please hit me a reply! I appreciate your help in advance.

thePrestige on Feb 9, 2013 said:

Yeap, i have parts..whats your email

kallaspriit on Feb 8, 2013 said:

Does anyone have an image of the Replicator 2X extruder design? It would be interesting to see how they did it there as they're also saying "new design employs a spring-loaded ball bearing". Wish they came up with an official solution for the Rep2 too, even if we had to pay something for it.

Stick-Tec on Feb 8, 2013 said:

I like to know whats the build time for this things with the recommended settings?

My bot just arrives yesterday :-)
Greets from Germany,

whpthomas on Feb 8, 2013 said:

Takes about an hour on my Replicator 2 to print the arm and base, and 15 minutes to print the pin.

anewsome on Feb 7, 2013 said:

whpthomas, I have to thank you in advance for releasing such an awesome design and definite upgrade to the Replicator2. I've had my Rep2 for about 4 months now and I can attest the delrin plunger design should indeed be considered a manufacturer defect. It's an otherwise great 3D printer, marred by an extruder design that is just plain broken.

I've printed 2 different extruder modifications that I found here on thingiverse, both designs are vastly better than the Delrin plunger design. However, I still have trouble printing clear PLA and it's also a bit of a pain getting the pin, spring and bearing just right. For many of us, we'd have to order these tiny parts from various places, just to put it all together. I wish Makerbot would finally admit that the plunger design is not working and offer everyone an upgrade kit to fix this issue.

Until then, we'll just be left to fend for ourselves. I'm going to try working with some of your commenters below and see if one if them will sell me a kit with the right bearing and spring already included.

Also, I notice that you already recognize that there may be an issue with the PLA warping over time. I know this will be an issue. The previous two designs I printed, both eventually warped to the point of no longer being usable. Have you considered testing your design printed in stainless steel? I know Shapeways does this and a friend of mine already did one of his designs in stainless steel and it worked great. I'm wondering if the heating block would transfer heat through the stainless though and cause even more extruder problems. At least the warping would be fixed though :-) ... anyway, just a thought. Thanks again for such an awesome design.

sciencemike on Feb 7, 2013 said:

Thanks for the upgrade. I melted a few of the bright color ones. Then I made the final one out of black because it has the highest melting point. It has yet to melt and bend.

sandersj on Feb 7, 2013 said:

I just installed this upgrade. Super easy, super slick, and I've got a big print going that failed miserably the three previous times I tried to print it. Its going flawlessly so far. THANK YOU for making my expensive paperweight into a 3-D printer.

wgss on Feb 7, 2013 said:

Bravo! I've got a Rep2X on order, which I understand is a different design now, hopefully a better design. But great job on the engineering and the detailed plans. You should consider selling a little "kit" to retrofit, I bet people would just as soon buy a kit then source and order all the pieces...

thePrestige on Feb 7, 2013 said:

Hi there, I have a couple of spares, will sell as a set

1) 1 x ball bearing

2) 1 x spring

3) 2 x M3 screws

All for $10 USD. Exclusive of postage.. but it should be very cheap for standard mail. Can contact me at zhangwl87 [at] gmail com

IcanCwhatUsay on Feb 7, 2013 said:

This makes me want to buy a Replicator all the more...I don't like you right now (at least my wallet doesn't...nothing personal) ;)

Anonymous on Feb 5, 2013 said:

Hi, saw your comment about the R2 feeder upgrade. I'm needing this so if you've got one available to send me I'd really appreciate it. What do I need to do to get one?

Thanks so much for doing this. I'm east of Toronto in the Oshawa/Clarington area FYI.

cthree87 on Feb 5, 2013 said:

I started having this problem today (day 2 with my Rep2). Thanks for the simple upgrade. I'll definately try it out and hopefully get through an entire print without the nozzle clogging.

kallaspriit on Feb 5, 2013 said:

Great stuff, thanks for the upgrade. I wonder how MakerBot came up with such a bad original design. Printed it on medium quality first (as it messed up HQ number of times) and later managed my first proper 100-micron print.

The dimensions of the model could have a bit of margin in them, had to file down the pin, M3 holes and the bearing slot a bit but generally seems to work great at first try :)

fullandc on Feb 5, 2013 said:

thanks to thomas (and all other guys) for making this! - it´s really making life with the rep2 easier - even the first prints i made showed me it is working much better now! - thanks to bre for leaving everybody room to improve things - it would be really boring to have a perfect replicator - my iphone is perfect enough - and i´m already bored!

maker_workshop on Feb 3, 2013 said:

Printed and installed, at the beginning there were some clicks, so I changed the spring. +20 hours of printing later is working great! the stiffer the spring the better, no doubt. Thank you whpthomas! indeed it should be stock. Solved all the clicking.

Andychn on Feb 1, 2013 said:

IF I were Bre...
1. I'd stop production of the Rep2 and insert this upgrade into it's design
2. I'd make upgrade kits (bearing and screws) and send them free of charge to all Rep2 purchasers
3. I WOULD PAY whpthomas and all those who helped! Free plastic seems appropriate.

rgremill on Feb 7, 2013 said:

This x100!!!

Kallipigous on Feb 1, 2013 said:

I found I had to increase the scale by 1.05 for everything for it to match the motor. That way there was no gouging necessary and the screw hole lined up with the screw holes on the motor.

DigiFabLab on Feb 1, 2013 said:


**If you own a Replicator2 from MakerBot - PRINT AND INSTALL THIS MOD!!**

Thank you, Henry (emmet and infinityplusplus)! I've been pulling my hair out for weeks over large, mid-print extrusion fails with a new Replicator2. I swapped at least ten(?) emails with MakerBot support, to no avail. I suspected the (very poor) filament pressure mechanism, but wasn't aware of any improvements—then I found your excellent design, purely by accident. After installing, I just finished a large print that ran without a hitch for 20 hours and 45 minutes. :-)

Worth noting, for those trying to print these parts with either MakerWare or a machine without this improvement -- printing the lever arm laying down (after trimming off the "ears")—with Raft and Support on—was necessary because when the part was printed standing up (without Raft or Support) the extrusions failed at the very top (where the thumb release is). Also, since prints are weaker in the Z direction, laying them down makes the lever stronger if you're having some adhesion issues at the very top.

SmokyFrosty on Jan 31, 2013 said:

I want/need this upgrade so bad! But cant get the parts atm. :@

scvette on Jan 31, 2013 said:

Thank you Whpthomas!
I received my rep2, two days ago and have already printed this upgrade out and put into use. The extruder feeds flawlessly now.
Although I ordered the spring from Amazon, I ordered a couple and instead got a few bags totalling 20 springs.
I would be willing send these out to other Makers or actually put some kits together, but do not want to muscle-in on your beautiful product. With your permission, I would be able to ship these US side for minimal shipping cost and ship time.
Thanks again for this upgrade!

Saroyan2 on Apr 26, 2013 said:

They sent me a ridiculous amount of springs as well. Glad to know I didn't go crazy on the quantity button ;)

whpthomas on Jan 31, 2013 said:

Please do - I have a day job ;) I only printed some out and sent them on because I had spares and others were having trouble sourcing parts and reliably printing the upgrade. Post a group-buy on the Makerbot operators google group - I am sure you will generate some interest.

Sisyphus on Jan 31, 2013 said:

Such an elegant design. And now my Rep2 prints like silk. Great work.

barney on Jan 29, 2013 said:

just successfully printed with natural PLA for the first time after installing this update, produced a flawless print at 0.1mm, I would definitely recommend this upgrade.

whpthomas on Jan 29, 2013 said:

So its not just me - very pleased to hear this ;)

gzumwalt on Jan 28, 2013 said:

Worked perfect, the first time.

jasonmlopes on Jan 27, 2013 said:

Very impressive... been looking at all of your posts.... great work!

BuckRogers1965 on Jan 27, 2013 said:

Here in SE Ohio any M3 screws are impossible to find. There are some M4s, but nobody has the M3s. So I ordered some boxes of 100 from Amazon. I ordered a bunch of springs because the only one I could find was 5 packs of 4 springs each, and I got 10 bearings because the shipping was $5 if you bought 1 or 100 of them. Might put together a little kit for just over my cost plus shipping for people to order these things, get just what they need, all at once, and not have to pay a fortune shipping from 4 places. Offer just the hardware or hardware plus the printed pieces. I keep a big drill set next to the printer and use the drills to ream out the holes after the build. Just use the next size smaller than the hole and it works great. I also found that candle wax works really good to lubricate the plastic parts. Just rub the candle on the part where it rubs against another piece of plastic.

thePrestige on Jan 28, 2013 said:

I need a kit. Are you selling it?

whpthomas on Jan 27, 2013 said:

Happy for you to put a kit together, you can post on the google Makerbot operators group and let everyone know. I did one originally for others who found the parts hard to get, complete with printed parts, but all local springs are out of stock now, so waiting for more. Plus - I have to post from Australia.

Dtrobotics on Jan 26, 2013 said:

I love my replicator 2 but I was having prints fail mid print.

I would trouble shoot each time and I found that is was because even the Makebot filament changed in size up to .1mm over ten or so feet, and the delrin plunger just doesn't have the travel to handle that.

I printed these parts, and found the spring at Home Depot. My local Fastenal didn't have the bearing in stock so I just ended up turning a small aluminum roller the correct size on my lathe and at the slow RPM's the etruder turns it is working great so far. If it ever stops spinning well I will replace it with the bearing.

This fix has solved my printer problems! I have 12 hours of unfailed printing on it, which I could not accomplish with the delrin plunger method.

It works so well I have decided to make a new one on my CNC Mill to make it a long term fix for my printer.

mkc2 on Jan 24, 2013 said:

Printed this one and found the hole placement was better then previous version,
had to sand the pin down as it was a bit over size and make the bearing slot a bit bigger to fit the 3x4x9 bearing.
overall the best version so far....Great work...Thanks

Dugbi on Jan 22, 2013 said:

I love the fact that the users can actually design a better product than the manufacture. I am very thankful that you have created this as I unfortunatley suffer from the dreaded plunger problem. I am in the process of getting all the parts so that I can do the mod. Unfortunatly I have to have someone else print the parts as my printer is in bits. On a side note I noticed that some people have fitted the mod but are still having problems with slippage. I have just stripped my brand new Rep2 down in frustration and have found that the temp sender in the heater block is only lightly crimped to the thermister wire. when I pulled the wire it simply fell out of the fitting in the Heater block. I believe that the wire should be soldered into the fitting. When the head moves the wire has an air gap around it which can only be giving out an incorrect value as air in non conductive. My machine has suffered from blockage and jams since I received it and now i believe that this may be the cause, that the heater block might not be hot enough which is causing the Filament to not melt. Anyway Thanks again and I look forward to fitting your design.

ScottWatrous on Jan 21, 2013 said:

I just got one of these installed on my printer today, I was hoping to cure the dreaded Air Print!

The new part is definitely printing better: smoother lay down, smoother action: but I'm consistently getting air prints about an hour in: so at least as-installed it hasn't cured that issue yet.

The variable I've introduced is that I couldn't find the exact spring listed in-stock here locally, so I ordered the closest thing I could from McMaster-Carr: a 1.25x.375x.041 spring, of which I've trimmed half a coil to bring down to 1.125.

It could be that the spring is too strong or weak, but I'm wondering if this upgrade will even address air-printing without the services of some other mods/tweaks.

Scott216 on Jan 29, 2013 said:

What's the McMaster part number for this spring? I can't find a 1.25 x 0.375 x 0.041 spring on McMaster's website

whpthomas on Jan 21, 2013 said:

No that spring should be OK as long as the number of coils remaining is about 8 or 9 - much less than that and it may be too sparse and provide less tension.

Sorry to hear you are still having issues printing - here are some things to go over. Does your printer print reliably in any colour? It may be a problem with a particular roll of PLA you are using. Is the build plate level http://www.thingiverse.com/thi..., is the packing density set correctly in the profile you are using http://www.thingiverse.com/thi..., have you measured and entered your filament diameter correctly in Print-O-Matic - have you tried applying a dab of vegetable oil to the beginning of the filament.

If none of that helps, try changing the temperature you are printing at - some guys on the Makerbot Operators google group have found that their heater blocks were reporting incorrect temperature readings https://groups.google.com/d/ms... Increasing the print temperature fixed the problem - but this is not a cure-all just may be the problem you are experiencing.

Finally don't change everything at once - or you will have no idea what worked. Dial-in your basic setup first and then start tweaking one thing at a time.

DrGlassDPM on Jan 20, 2013 said:

I'm taking the plunge (anti-plunger) move now. Wish me luck and I'll see you on the other side.

toni1727 on Jan 18, 2013 said:

Hi people, you can buy the springs here:


toni1727 on Jan 18, 2013 said:

Hi! People, you can buy the springs here:


Big-E on Jan 16, 2013 said:

Hi Thomas, I made it, it works awesome! Let me know if you decide to machine these, although the printed one works just fine.

I added it to my Rep2 essentials collection, as well as your dial holder. both excellent parts. Thanks for all the info you gave in the makerbot google group too. I'll be watching your career with great interest!

Neutron7 on Jan 15, 2013 said:

I looked for "C624" on century spring web site, but there was no result, do you have a link for the springs entry? (don't have it at home depot Canada)

ark19 on Jan 15, 2013 said:

Hi Thomas, thanks for the detailed descriptions! Will this bearing work?
ID 3mm, OD 9mm and width 4mm.
I'd ordered it for the MK8 upgrade...

whpthomas on Jan 15, 2013 said:

No its pretty precisely aligned. You really need the ID 3mm, OD 10mm and width 4mm - no simple fix there I am afraid.

bre on Jan 14, 2013 said:


rgremill on Jan 17, 2013 said:

Any chance that Replicator 3 will use this design?

whpthomas on Jan 16, 2013 said:

Hi Bre,

Thank you for the complement. I understand now after watching a CES interview that you decided the launch the Replicator 2 5 months earlier than your had planned because you landed the Wired magazine cover - on balance I am glad you did - despite the teething problems I have experienced with this product. If I had been in your shoes I would have done exactly the same, so I trust you'll see my criticisms above are intended to be constructive.

This upgrade really does seem to have finally fixed my printing problems. I say "make it" and my Replicator 2 now happily obliges. The feelings of frustration and exasperation are fading and my initial excitement and enthusiasm for this truly magical machine is returning. Thank you for your part in making this all possible, it really is transforming the way I work.

Best Wishes,


tedenda on Jan 14, 2013 said:

Do you know if there is a metric alternative to the spring you have chosen?

If you do, maybe you update the description?

whpthomas on Jan 14, 2013 said:

The exact equivalent would be 9.5 x 28.5 x 1.04 mm however in metric, there is a 9.0 x 28.5 x 1.0 which would be close, but too narrow and a bit weaker and the next size up is 9.25 x 33.0 x 1.25 but its a bit too long and too narrow. But if you can get hold of a metric spring that is close, that you think will work and you need me to tweak the design, let me know the spring dimensions and I will upload some revised STL files for you.

tedenda on Jan 14, 2013 said:

I like your detailed description and the good photos!
Will print this tonight and replace the Minimal MK8 that I have mounted now.
I hope this will solve some of my problems!