Replicator 2 jamming/thermocoupler errors/something else

[GIbbonz]

Hey guys,

Just a question about the thermocoupler, is it possible for one to be readings incorrect temps? I say this because we've been having problems recently with prints failing part way through (not consistently at the same layers either) it'll recover then keep doing it throughout the rest of the print, the extruder clicking is there so it's either not gripping the filament or it can't push it through (see this lovely example here).

2015-06-17 17.18.34.jpg

All this is is printed with filament we know works, as it's left over stuff from a few weeks back that printed flawlessly (it has been sealed in an air tight container ever since). Been trawling the web and found many references to 'heat creep' or somthing similar, so thought OK it could be that as we do run it fairly hot (220-230) so tried sticking the temperature down to 215. Nope still happened, even more soon this time. So OK, that sounds like the filament is too cold, the extruder can't physically push it through. Which brings me onto my thermocouple theory.
Is it possible it could be reading a temperature 10-20degrees lower than the actual? I say this because I'm i've just printed this:

2015-06-18 11.24.24.jpg

the first 1/4 up to where it fails, is printed at 230degrees. Thereafter I increased the temperature up to 240, and it actually managed to finish the print at an OK quality, i've tested this twice now, with similar results.

So, could this be a problem with the thermocoupler giving a bad reading? Here's a pic of it (it does look a bit dodgy, like some of the casing has melted away.)
2015-06-17 16.56.40.jpg 2015-06-17 16.28.34.jpg

Of course it could be nothing to do with temperature and be something completely different but I'm at a loss and so any help/guidance would be greatly appreciated, thanks!

I appreciate there's not much info to go on here as it's mainly just a question on whether or not this theory could be correct, I plan on picking up a temp probe in the next day or so to test the temperature of the nozzle/block.

[Mjolinor]

" A few weeks back" << there's a clue. Damp filament. Thermocouples rarely read incorrectly, they either work or they do not work. Thermocouple wires are fragile because of their nature but a break will show a fault, it will generally not read incorrectly.

[sinful]

Agree on Mjolinor post, if it is something wrong with thermocouple you normally get an error message. In your case if filament loading functions properly and the filament stream is consistent, the problem could be lying within the Extruder plunger kit, the spring tends to wear off over time, and you need to replace either the whole kit, or you can disassemble it and stretch the spring out, then spray a little bit of WD-40 into the hole where you load filament and you should be fine for such small prints as yours. For the long term solution I would recommend replacing the whole Extruder Upgrade Kit.

[GIbbonz]

I figured as much that the themocouple would either show the correct temp or an error message. Was a bit shot in the dark! Re damp filament, it's been stored in air tight conditions with about 1kg of silica gel, also the problem is also occurring with brand new filament out of the pack (tried 3 new rolls now, all vacuum packed and showed no signs of rips/tears) haven't completely ruled it out, but I think it's very unlikely.

Re the extruder kit, I've looked at it a couple of times whilst dissembling and haven't noticed any obvious wear on it (have been printing for over 1000 hours on this bot though). But i'll take another look and do as you suggested to see if it helps. Thanks guys.

[sinful]

Re the extruder kit, I've looked at it a couple of times whilst dissembling and haven't noticed any obvious wear on it (have been printing for over 1000 hours on this bot though). But i'll take another look and do as you suggested to see if it helps. Thanks guys.

1000 hours is definitely long time for the wear down. I wasn't talking about the whole assembly just the spring, you don't see the wear down so visibly but the tension of the springs tends to weaken and need to be stretched or replaced.

One more thing about your print settings I wouldn't go under the 230°C by printing with original MakerBot filament. Personally I prefer using 232°C.