I've run multiple tests with different temperatures and can't get PETG filament to cool within the specified diameter tolerance. What should I do?

After ensuring the barrel and screw are clean and the pellets are dry, try using a larger diameter nozzle and increasing the Spooler drive wheel speed to reduce the filament diameter. If the filament still falls out of spec, use calipers to measure at several points, as oval-shaped filament could be causing diameter inconsistencies. If the filament is oval, ensure the maximum diameter stays within the nozzle limits. You could also try an extended nozzle, which includes a melt filter to remove contaminants. The extended nozzle provides more back pressure and a longer dieland, which helps stabilize the filament before extrusion