Repeated clogging on Makerbot Replicator 2 even with new extruder

[verersatz]

Here's the short version of the problem I'm running into:

• Printer started partially extruding in the middle of a print, so I stopped it. Tried to unclog. No matter what I tried, it either pushed out filament in clumps that curl back up toward the nozzle or pushed out strands that are too thin.
• Since I was having so much trouble and had a backup brand new extruder assembly on hand, I replaced the whole assembly. Drive gear wasn't rotating so I put the old drive gear back in.
• Filament came out in a thin strand and then clogged again.
• Seems like every time I get the nozzle clear and then try to load filament through, it clogs again. I'm trying to load it manually in a disassembled state (see pictures). I can't figure out what's going on.

Since I took things apart to the point where the drive gear is no longer in play and I still have the issue, I'm guessing it's not that. I have also tried different colors/brands of filament. Is there something else I'm missing? It doesn't make sense to me that it should be clogging repeatedly with two completely different extruders.

Attaching pictures so you can see that I have gotten the nozzle clear (you can see the light through it) and you can see the state it's in when it reclogs (so you can see what is/isn't affecting it).

March 25, 2016 at 0419PM.jpg March 25, 2016 at 0419PM (1).jpg

[Alibert]

What polymer are you printing with?
What temperature of the nozzle?
What printing speed?

[verersatz]

I'm printing with PLA 1.75mm. The nozzle is at 230 C, which is Makerbot's default for preheating. I heated it to 250 C at some point when trying to unclog. At this point, there's no printing speed, since it's just clogging when I'm trying to push it through manually to test if it's unclogged/ready to be put back together.

[Alibert]

Your print temperature is the one for ABS, not PLA. Turn it down to 200 C to start with (also in the display in preheat settings if you preheat).

At 230-250 your are burning your PLA, thus causing the clogs.

Your nozzle may need to be cleaned or replaced now, as it (and the ptfe tube?) may be filled with crap. Spare nozzles will cost you around $1 a piece if bought from aliexpress. It is wise to keep some stock of them to quickly change out. I actually never clean a clogged nozzle, just replace it with a new one when needed.

[verersatz]

I normally print PLA at 210 when it's actually printing. I was just using the default preheat settings for clearing the nozzle so I could melt the clogged stuff enough to get it out.

[Alibert]

My experience is that too high temperature turns PLA into solids.

Maybe you should dismantle the extruder and check the heatbreak, nozzle and (if present) the ptfe tube?

[verersatz]

Update on this: I was finally able to unclog it and put the extruder assembly back together. It's working for the most part. Some prints are fine, some have been clogging repeatedly with no clear reason. One of them has a lot of support material, so I'm not sure if it has to do with that.

[Alibert]

What speed are you printing at? Supports and infills are printed at higher speeds than outer shells, and you may be pushing your extruder further than it can go. Try halving your speed as a test and see if the clogging stops?

[verersatz]

That's a good thought. I switched to a different printer for the one that was clogging with many supports, but next time I run into the same problem, I'm going to try slowing down the supports and infill speeds and see how it goes. Thanks!