Replicator 2X Extruder Drive Block Upgrade

by rmcniff, published

Replicator 2X Extruder Drive Block Upgrade by rmcniff Jan 10, 2014
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Makerbot Replicator 2X Extruder Drive Block Upgrade

UPDATE Jan 30, 2014

New V2 files uploaded. A few minor changes were made that should create stronger parts that require less post-finishing. Also, a remix has been created based on user comments to create a version that uses an M4 flat head screw to mount the bearing. If you would prefer to use a screw, you can find that version here:


This is hopefully the last extruder drive block upgrade you'll ever need for your Makerbot Replicator 2X.

It is loosely based on the function of the official Replicator 2 (not 2X) upgrade:
and on the aesthetics of the whpthomas upgrade:

Advantages over other drive block upgrades:

  1. Includes a fully surrounded lower filament guide hole between the drive gear and the entry to the hot end. This is ABSOLUTELY ESSENTIAL when printing with flexible filaments to prevent bending and kinking of the filament. Almost all of the other 2X upgrades are lacking this critical element.

  2. Has a deeper filament guide tube hole than many others, which prevents the guide tube from slipping out while printing.

  3. Requires no extra hardware for mounting the bearing. The mounting pin is included in the design, as it is in the Replicator 2 upgrade.

See the Instructions section for required hardware, notes, and details for a successful print and assembly.


Required Hardware:

Assembly requires the bearing and shoulder bolt from the stock extruder.
Additionally, it requires one M3 flat head cap screw (8mm length) per extruder, and a 0.375" X 1" or similar compression spring. I am currently using a spring from McMaster-Carr that works perfectly. It is part number 1986K5:

NOTE: If your extruder clicks and does not extrude, it you likely have too much spring tension. In this case, swap the spring for a weaker or shorter one.

Printing the parts:

  1. Print the base pieces. I used ABS with 3 shells, 0.15mm layer height, and .3 density supports and "doSupportUnderBridges": true. It helps to print both the left and the right at the same time so that the details of the smaller top come out better

  2. Print the arm pieces. I used ABS with 4 shells, 0.15mm layer height, and 0.4 density supports with "doSupportUnderBridges": true to help the bridging of the guide tube hole.

  3. print the cover pieces. I used ABS with 2 shells, 0.15mm layer height, no supports. Again, it helps to print both the left and the right pieces at the same time to allow cooling between layers

Finishing the parts:

Some post-print detailing may be required to achieve the desired tolerances and fit of components. The below is a rough guide to the drill sizes I used to finish the holes after printing. If you don't have the bits listed, any close approximation should work fine


  • 1/4" end mill was carefully used to grind out the larger hole of the cover piece to get the arm to swing easily while assembled. Could also use a 1/4" drill bit
  • Number 21 drill bit (.161") was used to shape the shoulder bolt holes in the cover and arm pieces
  • Number 44 drill bit (.086") was used to shape the small filament guide holes in the arm and base pieces
  • Number 27 drill bit (.144") was used to shape the bearing peg hole in the cover piece
  • B or C drill bit (.238" or .242") was used to shape the filament guide tube hole


  1. Remove the extruder stepper motor from the Makerbot gantry and remove the existing extruder assembly until you are down to the bare stepper motor
  2. Mount ONLY the new drive block base piece to the stepper motor using the shoulder bolt and M3 screw. Install the stepper motor into the Makerbot gantry and check the alignment of the lower guide hole with the hot end entry hole (See photo). If alignment is off, you may need to re-shape the hole with a drill bit, or re-print the part scaled up to allow for part shrinkage.
  3. Ensure that the drive gear also properly aligns with the lower guide hole. If not, loosen the grub screw and slide the drive gear to the desired position on the stepper motor shaft and re-tighten
  4. Unmount the stepper motor again, and fully assemble the drive block as shown in the photos, using the M3 screw in the base only, and the shoulder bolt as the arm pivot through all three parts.
  5. Re-install the stepper motor with the fully assembled drive block back into the the Makerbot gantry.
  6. Re-connect the cooling fan and stepper motor wires
  7. Enjoy failure-free printing!

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How come when i click on instructions nothing happens and i can't see them anywhere?

Dec 27, 2016 - Modified Jan 15, 2017
rmcniff - in reply to mkwilliq

EDIT: Everything looks like it's back up now

No idea. It looks like thingiverse changed the way they display this information, and now it's just gone. I don't see that info anywhere when I edit the thing either, and don't see a section to add instructions while editing. That link seems pretty pointless if you can't put anything in there. Maybe they're still in the process of updating this.

Sep 3, 2016 - Modified Apr 6, 2017

Considering i wouldnt be needing the stock screw that held on the original part i just took my dremel and cut it off at about 8mm. No need to go out and get another m3 8mm screw. I just installed, works great it seems. just needed to drill out the filament holes a little and sand a couple little pieces down and it was pretty simple.

Zits or blobs aren't going to be caused by the drive block. I mostly only see them when using a bowden setup due to the hysteresis in the tube. However, they can be caused by a lot of other things, such as using poor quality filament that contains air bubbles, or using filament that has absorbed too much moisture from the air. If the blobs occur while the hot end is moving I would suspect one of those two things. If your filament has absorbed moisture, you can dry it out in an oven for several hours at low temperature.

If it happens while the print head is stopped, I would try increasing your retraction speed and/or distance to keep excess filament from oozing out while the head is stationary.

Also, what is your nozzle diameter? Anything above about .4mm seems to ooze filament much more rapidly than ones that are .4mm and under. The nozzle oozes even while not extruding, which can cause a blob when it comes back in contact with your part.

Finally, I would not print ABS at 200. This doesn't seem nearly hot enough to me to get good adhesion between layers, and I'm surprised it is even coming out of your nozzle fast enough. I usually print ABS around 240.

I got it all fixed, not sure what it was but it was my printer not anything else. Deleted the edited comment.

Comments deleted.
Sep 19, 2015 - Modified Mar 9, 2016

Well, this fixed the problem we had with some filaments that were picky on which extruder we used them in.

FYI: Home depot has the screw and spring locally. Not all locations carry them but here is what I found locally (their web site is pretty precise on inventory for even the smallest of parts and locations...you can probably get them shipped to your local store for nothing):

Crown Bolt: M3-.5x8mm flat head phillips screw (3 pack)

Model # 06698

Internet # 203539921

Store SKU # 904299

UPC 0-30699-06698-8

Everbilt: Compression Springs assorted 6 pack (has two - 1 1/8"x3/8"x.041")

Model # 16087

Internet # 202045468

Store SKU # 685436

UPC 0-30699-16087-7

The springs are pretty rugged, they are 1/8" taller than recommended but I managed to squeeze it into the extruder with needle nose pliers...you might want to snip a turn off the end if you find it too tight. They do look like they want to pop out but they haven't yet.

Now to print and replace the left extruder.

Update: With both extruders now installed, and having printed a ton (small to large, simple to complicated), we haven't had a single failure and the springs I used, even a little larger than recommended, haven't caused any issues.

Hi, I like your design, however I have found a bit of an inconsistency... the size/tickness of it is almost twice than the original replicator one... such that you need to get longer hex screws to fit if you're planning to still add the fan, heatsink etc...

I was trying to CNC these on Aluminum but the print came out quite thick...

The size and thickness is almost exactly the same as the original Replicator 2X one. All of the stock screws should work fine. Did you maybe print it scaled up in size? You seem to be the only one so far that has had an issue with this.

uhm nope didn't re-scale it or do anything different... just opened it up with makerbot software and its quite thick... 15mm instead of 9.6 mm of the original one... the bearing hole and areas are good, only thickness is what's different...

@NHSE, wondering the same thing.

Also, anyone make this with PLA? Would its lower melting point be a problem here?

Has anyone tried this on the Rep 1 Dual? I see it mentioned below but no word on fit and function...

May 9, 2015 - Modified May 9, 2015

How are you getting those settings for printing, adjusting the density of the support material? Are you using MakerWare?

Never mind, just realized you can create custom profiles and edit this...

May 7, 2015 - Modified May 7, 2015

Do you have an arm model designed to use the shoulder bolt for the bearing?

Your suggestion of breaking off the peg and drilling a hole for the bearing seems easy and okay for people who have already printed the model. albeit, that little stick of plastic causes a lot of extra build time.

Could you possibly upload the .STEP files for the left extruder?

Nope, this has been covered before. I just mirrored the right side STL files.

thanks so much for making this thing happen!
I wondering if you have a version for 9 mm OD extrusion driver (instead of 12 mm)?

Thanks a lot. Extrudes FPE like a champ...

Mar 10, 2015 - Modified Apr 22, 2015

Amazing ! I am looking at the MakerBot and right now it seems to be working.

Make sure the thermal barrier tube (metal cylinder that screws into the heater block) isn't inserted too far into bar mount. I initially made this mistake and the new extruder drive block was at and odd angle because of this.

Post finishing tip: drill out the filament hole slightly, my filament was too chubby to go through.

I didn't have a spring of adequate strength, so I folded two together and that seemed to do the trick. The future is Open Source software, hardware, everything. This ability to modify and even improve on the original design is glorious!

never mind.
I mirrored it.
I feel so dumb.
Anyhow.. thanks for this posting... really works better than the originals.
I printed them using Nylon.
Very durable

Would it be possible to get the Extruder Arm L .STEP file
I'd actually like all the .STEP files. I"m trying to add an extension to the Extruder Arms.
If I can explain it correctly as follows.

I'm using Master Cam to add an extension with a hoop that is not closed.
But has wings that can be pinched to slightly open the hoop.
I plan to have the guide tube latch into that.

At any rate [email protected] is my e-mail
If you could send the files or write me there it'd be great!


What about printing 1.75 pla flexible with bowden with it? (It is not a joke, is my configuration :( )

Dec 18, 2014 - Modified Dec 18, 2014

I have not measured the screw needed yet but will post when I get to that bit. I'm buying a 10mm M3 Flat Head Cap Screw from McMaster - part number 91294A130 - available in packs of 100 but only four dollars or so.

The bearing is a shielded ball bearing ID 4 mm / OD 10 mm / Thickness 4 mm - McMaster part number looks to be7804K1 (that's what I'm about to order).

The shoulder bolt is 10 mm length 4 mm OD shoulder, 4 mm length M3 thread, and standard socket cap (6 mm dia, 3 mm high) - McMaster part number seems to be 90278A317. But a slot head one, 90270A655, is otherwise identical and 60% of the price, and a socket head low cap height (2 mm) one, 90323A215, is almost as cheap as the slot head and is the one I'm buying. (I'm tight-fisted - must be my Scots ancestors.)

Can you please reply and tell us how long of an M3 Flat Head Cap screw? I just need to now the length. Thanks

Either 8mm or 10mm should work fine. I'd go with 10mm if I had the choice between the two.

Where can I get the needed M3 Flat Head Cap Screw?

How much infill % to make the bases?

I would use 50% or so. It may be overkill, but stronger is probably better in the case of these parts.

How are you supposed to install the bearing? There is no pin like your drawings. All I got was a bevelled hole. Need an extra screw? What size? Also, what length of screw should i order?

Is there anyway someone could print these and send them to me? It's a catch 22, I can't fix it if I can't print with it.

Yeah so for me these didn't work as is, at least not with the springs sold by Makerbot for the upgraded extruder.. The spring seems to be a bit too small (length wise), and wasn't providing enough tension. Just now I printed SCH_Spring_Adj_rev1.stl from http://www.thingiverse.com/thing:62510http://www.thingiverse.com/thi...
to use as a spacer to compress the springs a little more. We'll see
tomorrow if it worked well enough to make it through a large print (it's
been jamming with the old extruder due to any slight imperfections in
the plastic).

Spring-loaded Replicator 1 Drive Block
by ivc

The MakerBot spring will not work well. It is not long enough and probably a bit too thin of wire. If you check out the Instructions section of this thing, you'll see that I spec'd out a spring from McMaster Carr that works very well for myself and others. It is McMaster-Carr part number 1986K5. Good luck!

The shoulder bolt that came with my 2x (mar2014) extruder is way too long (10mm)

This does not fit a Creator 2X. Bearing shaft is too thick, bearing pocket is too small. Body is too thick.

Would you know the specs of the shoulder bolt?

WWC - in reply to WWC

Ah found it in the link

Hi do you know where to get an appropriate M3 screw? Thanks!

rmcniff, could you upload the STEP files for the LEFT extruder arm, base and cover? We tried to take the right side and mirror but TInkerCad gave us garbage resolutions! We are modifying your design to use a bushing and will upload and credit your design once we get it working well.

I've had multiple requests for the left side files, but I never actually drew up the left side. Maintaining changes gets cumbersome if they have to be done in multiple places, and it's not really necessary when the only difference is that one is mirrored. Instead, once the right side files were exported to STL, I just mirrored the STL files using MeshLab.

This is really nicely done. I really appreciate the attention to detail such as the McMaster # and bit sizes for the holes. Everything fit perfectly and worked great. I have been using whpthomas' upgrade previously which was great but I wanted a few changes that yours addressed. When I get a jam I usually pop out the spring and use a wire brush to clean the drive wheel which is easier to do with this design due to the clearance. I removed the outer spring brace to accommodate the springs I had and to make it easier to remove. I also added a screw for the bearing since the pin snapped off. If my mods work out I will upload the remix. Nice work.

Converted my 2x after having a lot of issues with air prints. It has been printing without fail for 2 days now.
I opened the stock spring block while replacing it, and the little spring inside looks pathetic.
Should have done this much sooner.

I'm a bit worried about using ABS in the extruder head, as the 2X with its enclosure will run hotter than the 2, so I'm thinking about getting an aluminium version of this design. Fot now I'm very happpy with it though. Thx -Lieven

Contrary to "common knowledge", I have found that my ABS prints come out much better and with less warping and curling WITHOUT using the enclosure, and even sometimes using active cooling. I would encourage everyone to try it themselves and prove me wrong on that. I print ABS with the top cover off and the door open and my prints come out much better than they ever did while enclosed.

It was seriously a night and day, face-palm, "why didn't I try that before?" kind of moment when I discovered that. It took me forever to try it, since I also just took it for given that ABS prints should be enclosed. For tall and skinny parts I also use active cooling. I don't think layers have adequate time to cool and solidify otherwise, and this is what was causing bad edge curling and warping for me.

Metal would undoubtedly be the best material for the drive block, but ABS should be absolutely fine. I believe even the stock one is made of ABS. I have over 200 hours of print time using printed extruder designs with no temperature related issues. If you really want to put the effort into a metal one, that would be cool and I'd love to see it, but it wouldn't be worth the time and effort for me when they are 100% functional as an ABS incarnation.

The upgrade has been working great so thanks for that, although using it my prints are seeming to have a lot of extra filament zits on the prints. used to print ABS at 220, now down to 200 and the filament still seems to kind of just fall out of the nozzle like its too hot. any ideas on this? Thanks!

Have you heard others having similar success with removing the cover? We have a couple R2X's on campus that are having curling issues that may be interested in trying it. We have shop/lab ventilation so the downside of having more fumes/nanoparticles in the air shouldn't be a problem. (But you should be aware of that if you are printing in a semi confined space)

As for the metal drive block idea, we're excited to try out this upgrade in ABS, and if it works we'd be very interested in helping out with making a metal one. If someone does the design work, we have CNC's that could make it and we'd be happy to test it out and report back.

I have not heard anything from others printing without the cover, but I'm definitely a believer. More air flow seems to give me much better results, provided that there is very good adhesion to the build plate. If the adhesion is poor, it will likely cause edges to peel up worse than they would with the cover on, but the rest of the print is very much improved.

To get the best possible adhesion and surface finish, I use an etched glass build plate wiped with ABS juice. This sticks so well that it won't come off at all until the plate cools and then the parts pop off by themselves. It's the best solution I've found to this point.

Cool piece. Hope to print it soon. What kind of a build plate are you using?

The build plate is a piece of window glass etched with Armour Etch and then wiped with ABS juice (acetone with dissolved ABS in it). I then stuck it to the stock platform at the corners using 4 small pieces of 3M VHB tape. Works great, good adhesion, very smooth flat finish, and the parts pop right off once the plate cools down. I should create a "Thing" for that as well.

Yea you should. I've been having build plate issues with my rep 2x. That seems like a good solution. Does the tape seem to out gas much when heated (smell really bad)?

Anyone know how close these are to working with a Rep1?

Are you fitting these to a Rep1 Dual? If so I'd be interested to hear whether you tried it and how it's working out.

Would you happen to have these files as .sldprt? I'd like to do some modifications in SolidWorks and .stl don't play very well in the program.

I have included the files as STEP files. SolidWorks plays more nicely with these than with STL files

Very nice solution, I really like what you have come up with. Not owning a 2X iI was never able to fully test my upgrade, so I am very pleased to see the improvements you have made - they look very sensible. You still might want to publish a version where the bearing axle is actually a metal cap screw - it can be hard to get vertical rods to print strong enough - particularly for less experienced users.

Thank you for your praise, and for your work that led up to this design. You should know that the set pictured was printed using your 2X extruder design!

If you don't actually have a 2X then I'm thoroughly impressed with what you came up with. I couldn't count on my fingers and toes how many times the calipers came out to measure dimensions on the bot itself while doing the CAD work.

As far as your suggestion for using a cap screw to mount the bearing, that is a good idea. It would even be an easy mod to a print of the existing design. You could just cut off the peg, and drill a ~3mm hole in the arm where it was. Then chamfer the hole in the cover piece to accommodate the head of a 4mm flat head cap screw. Then it could be screwed right through the bearing into the plastic of the arm.