Makerbot Replicator 2x leaky nozzle fix

The used Makerbot Replicator 2x we purchased for the office has oozed / leaked plastic from the joint between the right extruder nozzle and the heater block from day one. The material would ooze out and form a plastic stalactite during a print, and occasionally break off and ruin a print.

Small immature green plastic stalactite visible on the right nozzle, on its upper left side. 

I decided to try and fix this by taking apart the extruder and using PTFE plumber's tape on all of the threads.

Makerbot doesn't really intended for end users to change / remove the nozzles, so it takes a fair amount of careful disassembly to do this.  It's also easy to break the ceramic insulators around the hot end heaters, thermocouple wires, etc, so do this at your own financial risk!

First, remove both extruder stepper motors, drive systems, and fans until you have the bare X axis platform and hot ends as shown below. This is a good time to loosen the set screws holding the hot ends in place. These are on the back side of the aluminum block, not quite visible on the "top" side of the photo below. Once these set screws are loose enough the hot ends will drop free- so be careful, the thermocouple / thermistor wires are very fine and easily broken. These set screws are also how you adjust the nozzle height to level the two nozzles.

Steppers, fans, and drive blocks removed

Next, remove the hot end block from the X-axis platform. There are two hex head screws to remove, one on each side of the X-axis platform. 

Bottom of X-axis platform, one screw visible

Once the two screws are removed, the hot end block can be carefully lifted free. This isn't totally necessary but makes disassembling the hot ends easier.

Hot end block lifted free

Setscrew for right hot end fully loosened, starting to pull hot end out (carefully)

Hot End is free. Thermocouple / Thermistor lead visible on the right

I first attempted to remove the nozzle and steel barrel from the hot end block by using a small wrench and a socket, but no luck. They were solid, plus I had trouble putting enough force into the wrenches while trying not a break anything.

Trying a 3/16" wrench

 So, my next step was to remove both the cartridge heater and the thermocouple / thermistor, then I could totally remove the hot end components from the printer.

Heater element removed

After the cartridge heater and thermistor are removed, you can carefully pull off the fiberglass insulation.

Thermocouple / thermistor & insulation removed

Hot End is free! the set screw on the left holds the cartridge heater in place

 I thought that there must be some solidified and baked plastic gluing the nozzle and barrel in place. I thought some careful application of heat from a heat gun would soften the plastic enough to take everything apart. Don't use a blowtorch as you can easily overheat the brass nozzle and deform it.

Heating assembly (heat gun barely visible on the top of photo)

Once everything is hot, very carefully twist the barrel and nozzle off. I didn't take a photo of it, but I held the heater block in place using the an appropriately sized drillbit held in a vice. The ceramic insulation over the aluminum heater block is very easy to crack, so be careful.

Carefully unscrewing parts after heating

Cleaning off the nozzle

Green ooze!

 Once all parts were removed from the heater block, I wrapped a couple layers of PTFE plumber's tape over the male threads. I make sure the tape wasn't blocking the through hole. Once the tape was applied to both steel barrel and nozzle I re-assembled the hot end.

White PTFE tape visible on the bottom side of the steel barrel

 I managed to slightly crack the ceramic jacket on the hot end during dissassembly. I cut some strips from my kapton tape roll that I normally use to cover the heated print bed to patch it back together.

Nozzle back in place. Note the extra kaptontape I used to patch together the cracked ceramic. 

Fiberglass insulation re-applied

Ready for re-assembly

Re-assemble the unit. Note that when you tighten the set screws in the aluminum block that hold the hot-ends in place, you'll have to carefully set the nozzle height- both nozzles should be as close to the same height above the print bed as possible.

The repair worked- after putting everything back together and re-leveling the build platform, all new prints were completed without the annoying plastic stalactites forming.