Trouble in paradise: The Replicator quit extruding…
I’ve been using my Makerbot Replicator (1) to print all the parts for my new C-Bot build. However as of a few days ago, it suddenly quit extruding correctly.
I print almost entirely in PLA, usually from 200-210 degrees. Suddenly, I couldn’t get anything to print unless I raised the temp to 230-245: Pretty crazy for PLA. And the surface quality was terrible. Any lower in temp and I could hear the extruder stuttering, and it wouldn’t really extrude much at all.
Leading up to this I had been printing at 120mm\sec, at .3mm layer height: Squeezing a lot of plastic out of the nozzle at that rate. I noticed a bunch of melted filament around the top-rear of the heater block (you only noticed it when specifically looking for it, couldn’t see it from the front\sides): The only way it could have got there would have been backpressure from the nozzle squeezing it out of an improper location up-stream. My guess is that this somehow started the domino effect to cause whatever was screwing up my current extrusion. It had completely encased the back of the heater cartridge and wrapped around the thermocouple wires. I had to heat the whole block up and carefully pick it away without damaging any of the wires.
Thanks to tips from this forum I got it resolved: One suggestion was that the kapton tape that insulates the thermocouple had worn through, and by grounding to the heater-block it was giving inaccurate temperature readings. This seemed like a prime culprit since I had to crank my temp settings so much higher.
I’m not sure specifically which steps fixed it, but this is what I did:
- Did a complete teardown on the hotend, to the last bolt. Removed old kapton, cleaned up head, wrapped in new kapton.
- Removed heater cartridge and thermocouple : Didn’t noticed any wear-through on the thermocouple kapton, but added more just in case.
- Did however noticed where the wire leaves the thermocouple and bends up around the heater block : one of the bends looked a bit frayed, and was mighty close to the heater block itself: Added extra insulatory kapton at that junction.
- Added a new nozzle, just to weed that out.
- Re-bed level, etc.
General rule of thumb is that PLA does not print reliably over 10 mm^3/sec with a typical Replicator type hardware setup. At 0.3mm layer height, 0.4mm extrusion width, and 120mm/s, you’re doing 14.4 mm^3/sec. That’s reasonable for ABS (which melts faster) but not for PLA. Raising the temp may cover the symptoms for a while but it can also lead to charred filament and worse clogging issues later on.