Makerbot Replicator 2 has an Extruder Feed Problem.

But the community already had a fix before I even got my printer.  The symptoms are varied.  Prints won't stick to the platform no matter how carefully you adjust the table.  You might just get a missed layer here or there, which really weakens a print.  Or you might get the dreaded air print, when you leave a job that is going to run for 12 hours and you come back to find it only printed half the job and is now just merrily printing nothing into the air.

The problem is the design that came from the original reprap and is a common design issue with many of the modern printers that derive from this venerable ancestor.  There is a hard plastic nub that presses the filament against the extruder drive gear.  The nub is positioned with a hex screw whose position is behind a fan and some wires.  I had issues each time I adjusted the tension on the nub because I would move the wires and the heater would lose power and not maintain temperature until I pressed the wires back into the connector.  The only tension on the nub is from a tiny rubber o-ring, but any more than minor fluctuations in filament diameter would cause the filament to stop feeding.

The problem part, from it's location in the top of the printer, to it's placement on the stepper motor, to where it is in the plastic housing.

Driver stepper motor in place on extruder head from center to right.

Motor and drive gear removed from extruder head.

The assembly that guides the filament and presses the filament into the drive gear.

The solution to the problem is to print an upgrade part from Thingiverse that fixes the problem.  This can be found here:  http://www.thingiverse.com/thing:42250


This is my fix in place before I put the fan cover back in place:

One problem that I had with this upgrade was the high cost of shipping for just a single part, or having to buy far in excess of what I needed for this one project.  Another was the time to get the parts.  I foolishly orded


So what I am proposing to do is to offer the 9 kits that I made up for sale, either just the hardware or the hardware with the plastic piece, just in case you waited too long and your printer can no longer print.

The kit with the plastic parts printed and fit together looks like this:

Kit assembled and printed in Yellow plastic, red and green are also available.

Update May 2013

It looks like Makerbot finally recognized their problem and are having a batch of replacement parts made to update their machines in the field.  I paid $9 for the "free" upgrade, which they claim is for shipping and handling, but that was months ago and I have yet to get the parts to do the repair.  I suggest still doing this fix until you get the mass produced replacement parts.

Dec 2013
I got the replacement part a couple of months ago, finally.  Was too busy in college to upgrade the printer at the time.  Going to tear into the printer at the beginning of the year to finally fix this issue.