Based on the excellent work of Thingiverse users whpthomas, emmett, and whosawhatsis, this design incorporates a spring-loaded arm to squeeze the filament between the drive gear and a bearing with a constant amount of pressure. We added improvements to the designs, such as a hole below the drive gear to guide the filament into the hot end.
MakerBot Replicator 2 owners will love the ease of this system for keeping filament running smoothly, and we salute the innovative MakerBot users who contributed to this design!
UPDATE! The hardware parts for this replacement are available for sale in our online store. Go to http://store.makerbot.com/drive-block-hardware-kit.html.
UPDATE! Rev2 files are now uploaded, and there are STEP files for anyone who would like to take a closer look at the design. There is also a version of the Base that can print without support material.
You can find a video of these instructions here: http://youtu.be/ZdOS5NP5eaE
As well as the three printed parts, you will need the following:
The 2mm and 2.5mm hex wrenches that came with your MakerBot Replicator 2
1 M3 Hex Socket Shoulder Screw, 4mm diameter x 10mm length shoulder
1 Compression Spring, 0.360"OD, 0.276"ID, 0.630" Free Length, 32lbs/in spring rate
1 M3 x 6mm Flat Head Cap Screw
1 Ball Bearing, 4mm ID x 10mm OD x 4mm width
- Print out SCHDrive.thing. The files are precisely oriented to work well with support material as generated in MakerWare. Use the following settings:
Layer height: 0.20 mm
Remove the support structures from the drive block base and bearing arm.
Unload any filament and switch off the MakerBot Replicator 2.
Remove the motor wire harness connector from the port at the top of the extruder motor.
Use the 2.5 mm hex wrench to loosen the two bolts at the lower corners of the front extruder fan. Pull the bolts, fan guard, fan, spacers and heatsink about a centimeter out of the extruder as one piece. This will free the motor. Pull the motor assembly out of the extruder.
Set the motor assembly down on a work surface. Orient it so that the motor shaft points up and the motor connector is on the side farthest from you.
Use the 2 mm hex wrench to remove the two bolts holding the drive block to the motor.
Remove the drive block. You can put the drive block and bolts aside. You will not need any of these parts to complete this part replacement.
Add the new drive block base to the motor so that the flat side rests against the top of the motor, the large hole at the center fits over the drive gear, and the two bolt holes in the base line up with the bolt holes farthest from you on the motor.
Add the small flathead screw to the bolt hole on the right of the drive block base. Screw it in using the 2 mm hex wrench.
Set the bearing arm down on your work surface with the flattest side facing down. The bearing arm is roughly L-shaped, and on the short side of the L you will see a short post pointing upward. Add the radial bearing to this post.
Add the bearing cover to the bearing arm so that the flat side faces up, the more rounded end fits into the round depression at the corner of the bearing arm, and the less rounded end partially covers the bearing. Press the cover on until it is flush with the edges of the bearing arm.
Fit one end of the spring over the round bump on the drive block base. The bump protrudes horizontally from the lower right corner of the drive block base.
Orient the bearing arm so that the bearing is at the left and the bearing cover faces up. Then line up the corresponding bump on the bearing arm with the other end of the spring.
Pinch the front side of the drive block base and the long side of the bearing arm together to compress the spring. Compress the spring until the bolt hole in the bearing arm and the remaining bolt hole in the drive block base line up.
Push the shoulder bolt through both bolt holes at the corner of the bearing arm and into the bolt hole on the motor. Use the 2 mm hex wrench to tighten down the bolt. You might have to push down hard on the hex wrench in order to get the shoulder bolt to thread into the hole in the motor.
The new drive block is now fully assembled, and you can return the motor assembly to the extruder. Slide the motor assembly back into the extruder.
- Making sure the fan bolts at the front of the extruder line up with the two lower bolt holes on the extruder motor, tighten the bolts into the motor using the 2.5 mm hex wrench.
Note: Make sure you are able to push the bearing arm down. If the bearing arm will not move, the fan bolts are probably too tight.
- Return the motor wire harness connector to the port at the top of the motor.
That's it! Start printing and let us know how it works out!