(This page concerns the Replicator 2. Some of this information is out-of-date, but much still applies)
On July 18 (2014?), due to print problems, I disassembled the extruder head from the gantry. Here's details. Some of the pictures ended up sideways, just tilt your head. Disassembly and reassembly at the level of detail here requires the large hex wrench included with the bot, plus a Phillips screwdriver, a 10mm wrench, a second 10mm wrench or a small crescent wrench, and a 7mm wrench. A vise or vise grips may also be needed.
At some previous time, the front fan had gotten most of its blades broken. The bot was turned on its side before this was discovered, and fan blade shards fell around the insides of the machine, possibly contributing to the clicky noises that are now happening sometimes when the gantry moves in the X and Y directions.
The print is less than a sixth complete. The machine output said it was done, at 5hr24min. There was, however, no large amount of extra plastic that would have been extruded if the problem were something other than, plastic stopped being extruded.
The nozzle had a small blob on it. There was some amount of mess on the kapton tape, but nothing unusual.
The intake hole for the filament showed some roughness on the filament, again pointing to extrusion problems. I could not unload the filament, with or without heat, and with or without pressing on the lever (as required for the extruder mod we have installed).
At this point I started taking the thing apart. If you can, unload the filament. The first step, not pictured, is to remove the front fan. Unplug the fan wires at the molex fastener. There are two screws at the bottom of the grill, requiring the larger hex wrench. The screws pass through the aluminum block, in unthreaded holes, and screw into the bottom of the motor case. These screws are the only thing that holds the motor on, but it's sitting on plastic and won't fall off when you remove the fan. The grill, fan, and heat sink all come off the front once the screws are undone. The screws are about 2.5" long. Once the heat sink is off you can see the extruder behind it.
If the extruder isn't jammed, it and the motor behind it will slide out from the back - unplug the motor power and controller wires first, they're a plug on the top of the motor.
It's dirty, but there was nothing obviously wrong with the extruder looking at it from the front, behind where the fan was. (Pic is sideways though.)
There was some metal dust in the bottom of the gantry. Could have been around for a while. Alternately could be related to the fan breakage. (Also sideways)
Next, remove the blower, or side fan. Unplug its power wires at the red handmade connector with the + and - marks on it. The blower is held on by two horizontal Phillips screws, one at the top left and one at the bottom right, seen from the left side of the gantry. They're about an inch long. It is helpful to slide the gantry to the right to fit your screwdriver when removing these. There's a plastic air guide here as well, which has arms reaching to the screw holes. It may fall off, or just take it off. The wires for the front fan go through where the blower was, remember this for reassembly.
Once the blower is off, in the space where it was, at the bottom, are two hex screws. Remove these to remove the plastic fairing, into which the filament tube fits when all is going well. These screws are short, less than half an inch of threading.
When I took the fairing off, I found a shard of the fan blade sitting on top of the extruder lever! That does not belong there. After this, I was able to remove the extruder, by pressing on the lever to release the spring pressure, and wiggling. The filament stayed in the lower hole, and I basically removed the extruder assembly by sliding it up the filament and off the top. Again this is not normal; usually the filament has been unloaded by this time and there's nothing in there at all.
Now I can see the hole where the filament goes down into the heater assembly, which consists of a big aluminum bar with a hole in it for the filament, plus the actual heater and nozzle below. It's got lots of bits and dust on top, blew those off.
And there's a big notch in the filament where the extruder roller ground it down without being able to push it into the heater. (Pic is sideways)
To try and remove this filament, I heated the heater up, first to 230C and then to 275C. I was able to get the filament warm and stretchy, but it would not come out. I clipped it as close to the hole as I could.
The filament hole, from the top, with a barely visible nub of black filament down in there.
With the heater still hot, I tried pushing a different, orange filament down inside to see if it would unblock in that direction. The orange filament also got hot and melty, but I could not force it through. (pic sideways)
After a second try, the melty bit just moved sideways and started blobbing up. No movement. So I decided to try and remove the heater assembly to see if further disassembly would prove useful. I could not find anything on the internet about this level of disassembly so I proceeded with caution and lots of photographs.
The attachment screws are underneath the gantry. There is one on each side; they use the large hex wrench. They're about half an inch long or a hair more. During reassembly I discovered that the plastic mount is threaded for these screws so you don't actually need to completely remove (and maybe lose) them. Nice thinking, Makerbot.
Now the aluminum bar can be grasped and pulled up. It gets hot when the heat is on, so be sure the heating is off.
Close up, the aluminum bar looks like this. I already loosened the nut on top before taking this picture, normally it's tight to the bar. This nut takes a 10mm wrench, and is VERY tight. The nut below is also 10mm, and there is just room for the wrench to fit between the aluminum bar and the heating element. Nothing is reverse threaded.
This screw is the top of a threaded tube that goes all the way down through both parts, and screws into the heater. (The brass nozzle tip screws onto the bottom of the heater through the other end of the same hole, and mates with the bottom of this tube.) The aluminum is also threaded and screws onto this tube. HOWEVER in most cases, you don't need to take the aluminum bar off, or touch these nuts. They're just more casing for the tube.
If you did take it off, though, you may have to use a vise or a vise grip to get the heater part off, if needed.
Before all that, take the power and sensor wires off the back. The white wires that power the heater have a connector, and the temp sensor wire actually screws in with a little bolt; it's not tight so you can undo it with a small pliers. I tried pulling it before I realized it and made a small tear in the insulation, which I think is not going to be a problem, but avoid it if you can.
Nothing visible in the nozzle tube in this pic, but in life there was a little reflection that looked metallic. (!?!?!?) Was there some kind of internal metal feature? (Turns out, no)
I stuck a piece of wire down and felt around to see where the blockage was (about a quarter inch down). The end of the blockage felt angled. I could not find a wire small enough to fit in the nozzle tip, which is .35mm IIRC, quite tiny!
At this point I felt stumped, and was about to email email@example.com after writing up this page. However, Costa showed up and thought we could make further progress. He, picturelessly, took the heater assembly apart again (the 7mm wrench is used on the nozzle, and either the nozzle will come off, or the heating element will unscrew from the filament tube) and then took the blocked tube down and put it in a vise and stuck a drill bit in and was after some effort able to remove a very solid plug of what appeared to be just plastic. Here is what THAT looked like:
And here's what the heating element and nozzle look like from a couple angles.
At some point we realized that one of the blower fan wires had broken off its connection, and decided to add a connector since just about everything else had one.
So after the plastic plug came out, we figured it was worth putting it all back again and testing it out. While reassembling, there were a couple points I discovered that are worth documenting. I did this:
1. heater assembly
from top, these parts go around the threaded filament tube:
- one 10mm nut
- aluminum block
- other 10mm nut
- heating element
- nozzle tip (may not have been removed)
Note that the threaded filament tube has two sets of threads; the smaller set goes down, and screws into the heating element. Also be careful about the orientation of the aluminum block, as other things screw into it. See pictures:
Get all these screws as tight as you can while retaining the perpendicular geometry of the aluminum block and the heater. The distance between them is enough for a 10mm wrench to get in and hold the nut in between, but it's tight. There isn't a whole lot of leeway here so be as accurate as you can.
The temp sensor wire also needs to get screwed onto the back before the motor goes in; I put the block on the gantry first but had to remove it again.
When it's together, reseat it and screw it to the gantry from underneath.
2. The plastic fairing
This screws to the top of the aluminum block, on the left side. The heating element wires go behind it.
3. motor and fan
Reseat the motor/extruder assembly by sliding it in from behind. The heating element wires coming up from below go in front of the motor and stick out to the left (from the front) towards where they go into the cable protector.
Place the front fan, heat sink, & grill into position. These have the 2 long screws which go in the bottom holes. The wires are supposed to go through the fairing hole to the left, but you may want to leave them in front so they can attach above; this is easier if you will be taking it apart a couple of times. Slide the fan etc in front of the extruder and screw it down to the motor, through the holes in the aluminum bar.
4. blower fan
The blower fan and air guide screw on from the left side using Phillips screws. The wires are normally still attached to the machine through the cable guide, but not in our pics b/c of the broken wire and subsequent addition of a pin connector.
The air guide inserts a short way into the blower exit hole.
Fit the blower fan with the air guide pointed down in between the X axis slider bars and screw in the Phillips screws in the top left and bottom right.
Finally, zip-tie the cable holder back in place, and reattach any wires that still need it. Makerbot used a different kind of connector on each one, so you don't need to worry about connecting the wrong ones (nice thinking Makerbot).
Jog the axes a bit to make sure nothing broke itself while the extruder was in bits, load up some more filament, cross your fingers, and print!
Having done this, I am of the opinion that this is in general a nicely designed extruder assembly, not hard to figure out, with a couple convenient features for the DIY-er. That is, with the extruder modification, not the original extruder!