The Stratasys extruder clog from hell

When I last wrote, I was dealing with a Stratasys FDM 2000 head solenoid that just wasn’t working.  Well, I managed to get a replacement (thanks, John!) and sent the original off to a company in the Chicago area that rebuilds old automotive starter solenoids of that same ‘crimped can’ construction.  I think one of the leads simply became detached from the coil winding, which should in theory be a simple repair.  But having zero experience in that realm, I’m happy to let an expert take a crack at it first.

The solenoid from John works like a champ, so it was on to the next problem – a persistent clog in the support extruder.  I found that I could extrude support material happily enough if I removed the support nozzle, and I did see a few specks of crud get flushed out from the support side as I ran foot after foot of filament through it.  I also cleared out the nozzle itself with a 0.011″ drill bit in a pin vise, just as I’ve done on my 1600.  Still, this didn’t seem to help much.  I could extrude a little bit of material out of the nozzle, but after perhaps 10 seconds or so, the material would stop coming out of the nozzle and would backflow out of the inlet buffer.  I figured that there must be some sort of blockage still in the extruder, so I purchased some soft brass wire and the teeniest wire brushes I’ve ever seen from McMaster-Carr.  I removed the nozzle from the support extruder as well as the support motor drive block, heated the support side to the normal operating temperature in the printer, then quickly removed the head and ran about a foot of the brass wire through the extruder to drag out as much of the soft support material as possible.  I also removed the inlet buffer, but forgot that they actually have a tip that presses into the metal tube that serves as the ‘hot end’, thus rediscovering the issue that Rob @ Incredilution had found when attempting repair on his head.  Namely, I broke off the tip in the heater tube.  Naturally, I shrugged and put the inlet buffer back in place after cleaning, figuring that the break wasn’t a big deal.  I was mistaken – when I heated the head back up and tried feeding support material in once more, the material backflowed out of a heretofore undetected hairline crack on the back face of the buffer itself.

I removed the inlet buffer once more and used a screw to extract the broken tip from the heater tube.

Fortunately, John had machined some replacement inlet buffers some time back from some scrap Torlon that I had sent him, and I’m glad I had one on hand.

Unfortunately, even after thoroughly scrubbing the support extruder, things were now worse than ever, and I now get material backflowing out of the inlet buffer without even a nozzle attached.  I’m somewhat at a loss to explain why this might be, but the best I can figure is that running the brass wire and mini wire brushes through the extruder might have scratched the interior surface, causing sufficient friction to keep the soft plastic from extruding out the end.  With that possibility in mind, I figured I needed to fully tear down the head for a deeper look.

Here’s a look at the bottom side of the head with the bottom shroud removed showing the vanes that direct cooling air over the nozzle tips.

With the exterior shell full removed, we have a good look at the internals.

Here’s the bottom side of the head.

The thermocouple runs right into the end of the melt chamber.

Removing the aluminum foil outerwrap reveals the fiberglass insulation wrap.

With the fiberglass out of the way, we can see the heater coil wound around the melt chamber.

I first had to use a small punch to drive out the roll pin securing the solenoid paddle to the extruder.

Then I could finally snake the extruder free of the heater coil.  I had tried to slip the coil over the end, in the hopes of easily replacing it, but replacing any of this is going to be tough work.

And here it is – the ‘hot end’ freed from its overwrappings.  Now I just need to remove the inlet buffer and give the tube a solid cleaning to try and figure out what is causing the clog.