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I've been wrestling with a filament grinding problem for a few weeks now and I'm stuck.

The problem manifests itself as starting a print alright then extrusion stops while the printer keeps moving. When I pull the filament out I see indents from the gear then a depression where it ground down the filament.

Filament used is 1.75 mm Spool3D PETG on a Hictop printer, which is a clone of a Prusa i3. I don't know the exact part number though. The extruder is direct drive, and the 28 mm heatbreak is connected to a heatsink block rather than something with fins. Nozzle is standard 0.4 mm.

My print settings are quite conservative. Speed is 20 mm/s, retraction is 20 mm/s (though it never grinds on retraction), temperature is 255 °C, which is 10 °C higher than what works in my other printers. No print cooling.

At first I thought there was a clog, but I can push the filament though by hand quite well. I also use cleaning filament frequently and it never pulls out any debris. Heatbreak and nozzle have been changed to fresh items.

Does anybody have any other ideas of things I can try, or should I just get a new extruder?

0scar
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henradrie
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  • In the past I solved heat creep issues with PLA (a filament which conducts heat relatively well) by having a small fan blowing fresh air on the extruder gear, which in my case was exposed so it was easy to do. It worked very well. – FarO Aug 18 '20 at 08:53

2 Answers2

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This does sound a lot like you are experiencing the effects of heat creep (How is heat creep characterized?). You should lower the temperature of the hotend and increase the printing speed and retraction speed and possibly lower the retraction length.

If this is heat creep, a new extruder will not help you until you solve the heat creep first. A new hotend that can be cooled better might be a better solution.

0scar
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Additionally to the answer of @0scar:

  1. If the problem happens in the first layer, it can be that the z-offset is not properly setup: if the first layer is too thin, the printer cannot extrude (enough) plastic, and the filament will warm until the gear cannot extrude it any more. The solution is to have the perfect first layer thickness (so it stick well, but extrude the correct plastic amount).
  2. Release a bit the gear pressure on the filament: If the gear is too tight, with the temperature, it start to penetrate/deform the filament, and then is not able to move it.
0scar
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Adrian Maire
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  • Indeed! Also, many users (not me) generally require a little more offset between the nozzle and the bed when printing PETG. – 0scar Aug 17 '20 at 11:01