Replicator 2X Extruder Drive Block Upgrade

Author: rmcniff, published on 2014-01-09

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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!

License: Creative Commons – Attribution – Share Alike

Tags: 2, 2X, block, drive, drive_block, extruder, extruder_upgrade, filament, flexible, Makerbot, Replicator, Replicator_2X, Riley, upgrade, whpthomas, X