After building the extruder, I was able to source a couple kilograms of PETG regrind. It came as-is, apparently the company I got it from washes and dries it before further processing, and so did I, although only using tapwater and an oven at about 90C for 4 hours to dry the material.
When I put it in the extruder, two problems occur:
- even at very low temperatures (~170C) there is apparent smoke coming out of the plastic. It’s possible that this is from water evaporating, although it has a “PETG-like” smell, but definitely not as strong as actually burning plastic. I considered that maybe my temperature sensor is off, however I measured the internal temperature with a thermocouple and the values it returned were rather close to the external thermistor.
- the extrusion is inconsistent in that every 15-20 seconds a rough, thin, ~3mm long section extrudes, which contains pockets as in the picture and is very weak
Attaching a filter screen before the nozzle does not make any notable difference.
Does anyone have any ideas why this is? The plastic shouldn’t be impure given that the company I got it from was already using it in their manufacturing process, was the drying insufficient, or am I burning it after all?
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