Introduction: Adjustable Extruder Drive Block Upgrade for Replicator 2X

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This tutorial shows how to assemble an experimental adjustable drive block for the Replicator 2X extruder. The purpose of this design is to allow the operator to fine-tune the pressure applied to the filament by the idler ball bearing.

Note: This is not intended to be a replacement for MakerBot's original extruder block! Since the Replicator 2X Desktop 3D printer is suited for power-users who like to experiment, this adjustable extruder block offers an alternative way of gripping the filament and pressure fine-tuning. Please do not attempt to replace your original block if you are not comfortable disassembling your current extruder and fix any issues. If you try this design, make sure to save the original parts and follow the instructions below carefully.


  • All parts can be 3D printed!
  • Offers step-less filament grip pressure adjustment
  • Built-in filament dust filter with sponge
  • Cover plate to protect stepper motor cables and connectors
  • Fasteners and ball bearing can be re-used from the original
  • Sturdy design

Parts list

  1. Base left (3D-printed part)
  2. Base right (3D-printed part)
  3. Lever left (3D-printed part)
  4. Lever right (3D-printed part)
  5. Bearing cover left (3D-printed part)
  6. Bearing cover right (3D-printed part)
  7. Stepper motor cable cover (3D-printed part)
  8. Knob bottom part (3D-printed part)
  9. Knob top part (3D-printed part)
  10. M3 Nylock nut (2 pcs)
  11. M3 countersunk screw - 23 mm (2 pcs)
  12. M3 countersunk screw - 6 mm (2 pcs)
  13. M3 hexagon screw - 35 mm (2 pcs)

Tools and materials

  • 2 mm hex key
  • Water pump pliers
  • Beak pliers
  • A few drops of super glue

Version history

This design is a variation of current Adjustable Drive Block Upgrade for Replicator 2 and 1, which in turn is a variation of Spring-loaded Replicator 2 Drive Block, which also derived from three other previous designs.


The MakerBot Replicator 2X Desktop 3D printer is best suited to 3D print models made of ABS plastic filament. In contrast to 3D printing with PLA plastic, ABS requires that the process occurs in temperature-regulated and stable conditions. Therefore the 2X has a heated build plate and enclosure to keep the inside of the machine warm.

Being an experimental 3D printer, the 2X requires that the operator understands its capabilities and functions. For instance what temperatures and print speeds are best suited for different shapes and sizes of models.

A simple rule of thumb is that the top hood is only needed when larger 3D prints are made. By adding or removing the hood in conjunction with leaving the front cover open or closed, you can regulate the temperature in which the 3D printed model is made. The temperature and flow of the air in the room where the 2X resides is also a factor to take into account.

It is notable that temperatures around the extruder mechanism can raise significantly when the enclosure is fully closed. During 3D printing the air around the printer reaches typically 50 °C to 60 °C.

It is important that the plastic parts of this adjustable extruder block are 3D printed in ABS plastic (not PLA) at 100% infill to give them the best strength and heat resistance. Please note that this is an experimental design and is not intended to be foolproof and work perfectly in every situation. If you try it, learn from your experience using it. :)

We designed the parts to be as sturdy and strong as possible to be able to cope with 3D printing temperatures for ABS.

Step 1: Download and 3D Print the STL Files

You can download the STL files for this project below for free. If you currently are unable to 3D print you can get in touch with us or ask a friend who has a 3D printer to print the parts for you. All the STL files are checked in netfabb and made fully 3D-printable. Please follow the instructions below.

  • 2X - Adjustable extruder (complete print plate).stl - Contains all 3D-printed parts for this project oriented to be printed in one go on a Replicator 2X build plate.
  • Base (1 pair).stl - The black base plate of the extruder block. It sits flat onto the shiny front surface of the stepper motor. This part has a built-in filament filter pocket where the filament guide tube is inserted.
  • Lever (1 pair).stl - The levers (right and left) of the extruder. This part holds the ball bearing which applies force to the filament and knurled drive wheel which grips the filament. This STL also contains the two small cover plates to keep the bearing in place and distribute forces.
  • Cable cover.stl - An enclosure or cover to protect the cables of the stepper motors from temptation to disconnect the cables when the power is still on (which is forbidden!) ;)
  • Knob_top_part.stl - The top part of the adjustment knob.
  • Knob_bottom_part.stl - The bottom part of the adjustment knob. It is glued to the top part to secure the screw head in place.

Material and infill

Use ABS plastic filament for this 3D-print and make it solid by choosing 100% infill. This consumes marginally more material but assures the highest possible strength of the parts.

You should not need to use raft or support structures for any of these files.

Step 2: Unplug the Power!

Before you do any disassembly or maintenance of your MakerBot Replicator you MUST unplug the power and USB cable completely!

Do this not only by turning off the power switch but also by removing the power cord from the back of the 3D printer.

It is very important to understand that any fiddling with cables, connector, etc., when the power is on, can damage the electronics of the 3D printer.

Use your camera!

We assume that you are experienced working with machines and are comfortable disassembling the extruder. Nevertheless it is always good to have reference data when you take something apart.

Therefore we recommend you to always take photos of each step so that you can easily "travel back in time" to see where things were before you removed them. Almost everyone who has a smart phone also has a camera. Use it! :)

Step 3: Remove the Fan and Heat-sink

  1. Use a 2.5 mm hex key to remove both screws of from the front of the fan grate.
  2. Take a piece of painter's tape to secure the screws in place. You do not need to remove the grate-fan-heat-sink assembly. The tape keeps everything in place ensuring that you put it back in place in the correct manner. It is very important that the cooling fan is not flipped backwards when re-assembled. If you see the fan's sticker through the grate, then the fan is blowing the wrong way! Taping the screws avoids this confusion about the fan's orientation.
  3. Unplug the fan cable connector and tape the assembly to the right back part of the 3D printer. This way you won't misplace it.

One extruder at a time

Please keep in mind that it is better to change one extruder block at a time. First the right and then when that is done completely, you can start replacing the left. This avoids confusion and gives you a reference of the original version.

Step 4: Unscrew the Original Block

Use a 2 mm hex key and carefully remove the original block. Put it in a zip-bag and keep it in a safe place.

While you have the stepper motor axel and its drive wheel exposed, make sure that the set screw is nice and tight by using a 1.5 mm hex key. But do not over-tighten it!

In fused filament fabrication 3D printers it is a common cause for so called air-prints* when the set screw which holds the drive wheel becomes loose. When this happens the stepper motor continues to rotate its shaft as usual during 3D printing but it just slips inside the bore of the drive wheel, meaning that the wheel stands still and the filament is not pushed through the nozzle.

Having a loose set screw can also cause retraction issues. Sometimes if the set screw is just somewhat loose it can cause a play in the rotation of the axle and the drive wheel. Meaning that the filament can be extruded in one direction, but when the retraction occurs the shaft will rotate but the wheel slips a few degrees before it retracts the filament.

*Air-print is a common word describing a failed 3D print when the 3D printer starts a print successfully but at any given print height it suddenly or gradually stops feeding melted plastic through the nozzle.

Step 5: Remove the Support Material of the Base

The STL file for the base has a built-in support material. It is designed with an air gap which makes it easy to remove. You can simply use a pair of beak pliers and a knife.

Step 6: Attach the Base Plate

In this step you need to attach the base plate to the stepper motor. Make sure that the part of the base where the filament guide tube fits, points upwards in the same direction as the stepper motor's cable connector.

As fasteners you will need two M3 countersunk screws. One 23 mm long and one 6 mm long. You can get these from most hardware stores.

To assure that the screws sit firmly in place you can add a drop of blue thread lock on the tip of the screws.

  1. Insert the long screw a few turns by hand into the stepper motors threaded left hole. This will keep the base plate nice and square when you secure the short screw on the right side.
  2. Insert the short screw into the right hole of the base plate and secure it in place. Don't over-tighten it so you stretch and damage the 3D-printed part.

Step 7: Assemble the Lever

The lever holds the ball bearing which applies pressure on the filament and the knurled drive wheel. The lever also has a built-in M3 Nylock nut which "climbs" on an M3 screw attached to the adjustment knob.

  1. Insert an axial ball bearing (4 x 10 x 4 mm) on to the small shaft of the lever
  2. Place the correspondent cover on top of the bearing and into the socket of the lever. You may have to jiggle it a bit to make it fit snugly.
  3. Use a pair of water pump pliers to grip the top of the yellow bearing cover and the bottom part of the lever. Apply gentle pressure until the cover sits firmly in place.
  4. Use beak pliers to firmly grip a M3 Nylock nut.
  5. Insert it into the tip of the lever. Make sure to hold it "upside-down" with the blue nylock ring towards the same side as where the bearing is.
  6. Poke the nut so that it aligns with the hole where the long M3 adjustment screw will be inserted.
  7. Insert the M3 countersunk 23 mm screw into the yellow bearing cap and drive it through so that it sticks out roughly 3 mm.

Step 8: Insert Damping Rubber Into Base

The black 3D printed block base has a hole into which the M3 adjustment screw resides. To give this design a built-in flexibility to let it yield and even-out forces, you can place a small piece of rubber into the bottom of this hole.

You could simply cut a 3 mm long piece of an O-ring or any similar rubber-like material. Push the piece all the way down to the bottom of the hole.

Step 9: Attach the Lever to the Base

Now you can attach the lever with the bearing you made in step 7 to the base of the extruder block. Put it in place and use a 2 mm hex key. Screw it firmly into place but make sure not to use excessive force. The lever just needs to sit snugly in place.

Remember that you can use a drop of blue thread lock to make sure the screw stays in place.

Step 10: Assemble the Adjustment Knob

The adjustment knob is glued to the head of an M3 35 mm screw. It is then secured in place by a drop of glue and a small cap.

  1. Place the knob down on a flat surface.
  2. Insert the head of the screw into the hole of the knob.
  3. Drip one or two drops of super glue into the hole.
  4. Use a stick to spread some glue on the surface of the knob.
  5. Slide down the cap on the screw until it reaches the knob.
  6. Adjust the screws orientation so it points straight up.
  7. Let the glue set completely before using the knob.

Step 11: Insert the Adjustment Screw Into the Lever

  • Insert the adjustment screw into the tip of the lever and the M3 nut.
  • Turn the screw clockwise until it enters the hole and the tip reaches the rubber.
  • You will notice that the lever will slowly start to rotate.
  • Do not over-tighten. You will adjust the right pressure later.

Step 12: Filament Dust Filter

The top part of the base has a cavity into which you can place a small piece of sponge. This will act as a filter which cleans any dirt and dust of the filament before it enters the extruder.

  1. Cut a small sugar cube-sized piece of the edge of a common household sponge.
  2. Grab it with a pair of tweezers and insert it into the rear hole of the base.
  3. Push it in until you can see it from the hole above where the filament enters.
  4. Cut a piece of filament at a narrow angle with side cutters. This creates a sharp tip.
  5. Press this filament tip through the sponge and poke it through.
  6. Continue to press the filament past the ball bearing and drive wheel and make sure it protrudes through the exit hole on the 3D-printed base.

Step 13: Assembled Extruder Block

Your extruder block is now fully assembled and ready to be mounted into the Replicator 2X desktop 3D printer. While you have it in your hand, try feeding the filament up and down manually and adjust the knob to get a sense of how little force it takes to grip the filament against the drive wheel.

Step 14: Mount the Block Into the 3D Printer

Now it is time to put the stepper motor back into its place where it was initially.

  1. Place the extruder block back in place. Make sure the screw holes align.
  2. Detach the blue painter's tape from the fan and heat-sink screws.
  3. Insert the screws into the aluminium beam and secure them carefully into the threaded holes of the stepper motor.
  4. Be careful not to apply too much force. Always turn the screws anti-clockwise until you feel the start of the thread and then reverse it clockwise and carefully tighten the screws.
  5. Reconnect the cables for the stepper motor and heat-sink fan.

Step 15: Repeat Steps 3 Through 14 for the Left Extruder

Now that the right extruder is ready. Repeat steps 3 through 14 for the left extruder.

Step 16: Assemble the Cable Cover

We designed a simple plastic cover which snaps onto the rear of the base plates and the cable holder of the 2X extruder structure.

The purpose of this plate is to protect the cables and connectors of the stepper motors, thus avoiding any accidental disconnecting while the machine is turned on.

Step 17: Adjust Filament Pressure

Now you are almost ready to start 3D printing!

  1. Check all connections to make sure everything is well-assembled and in order.
  2. Mark the first segment of your filament with a marker pen. This makes it easy to see when the filament starts moving.
  3. Insert the power cable into your Replicator 2X and turn on the power switch.
  4. Via the LCD display press load filament as usual.
  5. When the right temperature is reached the stepper motor starts turning to feed filament to the extruder hotend.
  6. Insert the marked filament as usual into the extruder until it passes by the ball bearing and drive wheel.
  7. The pressure applied by the lever is probably too low and the drive wheel will slip.
  8. Gradually turn the adjustment knob clockwise until you can see the filament move down.
  9. Note that the filament reaches the bottom part of the hotend and comes out of the nozzle.
  10. You can now fine-tune the knob to achieve a continuous filament feed. Please do not overthighten! There is no need to increase the pressure significantly after the filament flows continuously.
  11. Please note that this is an experimental design and should not be seen as a final product. Plastic has some tendency to settle and yield when loaded with a force. Experiment with different pressure settings until you reach a steady and continuous flow. Also note that you need to readjust the setting when the temperature of the extruder reaches its peak. For instance if you need to 3D print with the enclosure fully closed.

Step 18: 3D Print Stuff!

Now that you have an experimental extruder block, 3D print some cool designs! Why not start with a 3D-printed miniature of a shipping pallet.


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