This is the most current version of the extruder kit...

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."

You are buying an assembled Makerbot Replicator 2 Delrin Plunger replacement kit/Extruder Upgrade kit as shown in the first image This assembled kit includes everything needed to replace the delrin plunger on your Makerbot Replicator 2 with a spring loaded ball bearing assembly.

You will get the actual kit shown in the first image. This includes:

• The Back Plate
• The Swing Arm (the top hole may require reaming for the filament to load and unload smoothly)
• TWO Pins - for the pivot joint of the swing arm(the extra pin is used to ream the hole, you will likely destroy it, this is okay, you can also use a 6mm allen)
• Two 10mm flat-top hex screws - One to mount the back plate to your stepper motor (Top Right hole on the back plate) and the other to mount the ball bearing inside the swing arm
• New high quality ball bearing
• New Compression Spring

*Stepper Motor NOT included.

The first image shows the kit fully assembled. The second image shows the parts that make up the kit.

I had nonstop problems upon receiving my Replicator 2, the Delrin Plunger was a piece of junk, maybe you don't have problems yet, but you will. We even had ours replaced but after so much printing it finds it's way into the drive gear and gets torn up. It was unbelievably frustrating and unfortunately, I couldn't even get it working well enough to print the replacement parts. I finally found someone I could pay to make the part but once I received it, I had an incredibly hard time finding all of the hardware that I needed. The new parts they had made were printed with the delrin plunger setup, I used the new parts to print my own parts for the same upgrade, the difference was extremely obvious. Although he was not having issues with his plunger(yet) the print made using the modified extruder was far superior. I will include the picture showing the differences but they are older derivatives of the upgrade.(The delrin plunger version of the print is white and the upgrade print is red). I will also include a photo of the cityscape print and our total print time on our Replicator 2 (304 hours), neither would have been possible without the upgrade.

The following is from the original designer:

This extruder upgrade for the Replicator 2 replaces the Delrin plunger with a pinch roller. 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 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.

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."