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I have a FlashForge CreatorX (MakerBot clone) that's been working fine for about 15 months. Int he past month, I started noticing "thin" layers in some of my ABS prints. I finally tracked the issue down to the extruder gear grinding the filament (after a while, enough filament had ground off that the gear teeth were filled with plastic). I cleaned the gear twice before giving up on ABS and switching to PLA. Everything seemed ok until the PLA started doing the same thing during an overnight print (thin layers on prints, audible skipping during filament feed).

Raising the temperature on the extruder seems to fix the problem, but I'm now extruding PLA at 242 °C, much higher than I used to need. I worry that continued printing at this temperature will increase wear on the thermistor and increase my chances of clogging PLA in the gear (an issue I've had twice before).

Are there any common issues that cause this issue of filament not feeding properly? I've tried cleaning out the extruder head with wire and there don't seem to be any clogs…

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  • $\begingroup$ Did you change filament vendor? Maybe this could be an issue. $\endgroup$
    – darth pixel
    May 20, 2016 at 14:46
  • $\begingroup$ If you can remove the feed pressure and feed filament by hand, what does the resistance feel like? If it is high, you may need to clean the head. $\endgroup$
    – Chris Stratton
    May 20, 2016 at 21:45

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I've encountered this on my Replicator Dual in the past. I was only using MakerBot branded ABS filament, so it wasn't a quality issue for me.

What I found was that the delrin plunger design that "helps" keep the filament in contact with the drive gear wasn't actually helping. So, I installed the newer assemblies that use a spinning bearing to contact with the filament.

  • Install (or keep installed) a spring loaded extruder assembly.
  • When feeding filament, loosen the spring and gradually tighten until the filament begins feeding on its own.
  • Try to stay close to the recommended print temperatures for the material. ABS is typically somewhere around 225C, but it depends on the supplier.
  • Ensure your filament is stored in a dry place. This is way more of an issue for PLA, but it doesn't hurt to keep your material protected.
  • If it continues, perhaps swap out the drive gear itself. If you've dropped your motor or somehow a burr has developed on any of the teeth, naturally the burr will cut away the material. Gears are very temperamental and should be considered a consumable.
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After disassembling the extruder mechanism, I tracked the issue down to a clogged extruder… though not in the way I'd expected. A (previously?) common method to drop filament down to the hot end and create a heat-break between the heater and the extruder gear was the use of a PTFE (Teflon) sleeve. Over time, this sleeve can become clogged by filament that has melted and degraded/carbonized, sticking to the "nonstick" walls. This creates a bottleneck for the new filament, preventing smooth extrusion.

Carbonized filament clogging tube. Location of heat-break on used tube.

My printer came with two replacement tubes. Swapping those in for the old, clogged tubes resulted in instantly improved printing… sorta like getting a new printer! Print temperatures are back to normal and everything operates fine. I was also able to drill out the carbonized filament from the old sleeve, though I doubt I'll reuse it. I found replacement sleeves on Amazon here and an alternative, all-metal extruder assembly manufactured by Micro-Swiss. I'm not sure if you'd run into clogging issues on the all-metal one, so perhaps staying with the PTFE tubes and replacing them occasionally is a better way to go.

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