PETG fails by dragging, not just peeling
Unlike PLA, a PETG first layer rarely just lifts off the bed: it goes down stringy and bubbly, and the soft filament sticks to the nozzle and drags across the surface. The result is a rough base and a print that breaks free partway through.
Why PETG won't stick
PETG needs a hotter bed and nozzle than PLA. Polymaker's Polymaker™ PETG product page lists the temperature ranges that get a clean first layer, and notes the cooling-fan range that balances detail against layer bonding. A bed that is too cool, or a fan blowing too early, are the usual culprits.
Recommended temperatures
Each value below is from the Polymaker™ PETG product page.
- Nozzle temperature — 240–260 °C for Polymaker™ PETG. (Polymaker™ PETG)
- Bed temperature — 60–70 °C. (Polymaker™ PETG)
- Cooling fan — 20–60 %: the recommended minimum is 20 % at a 30-second layer time and the maximum is 60 % at a 10-second layer time. (Polymaker™ PETG)
- Dry the filament — Polymaker™ PETG is hygroscopic; dry it at 60 °C for 6 hours before printing. Moisture is a common cause of stringing and a bubbly, weak first layer. (Polymaker™ PETG)
Testing the first layer
Run a 40 mm single-layer square at 20–30 mm/s and look at it from an angle: a good PETG first layer is glossy and even, with the lines fused and no string pulling behind the nozzle. If lines separate, the nozzle is too high or the bed too cool. If the nozzle drags filament, slow the first layer or raise the bed slightly. Let a full print finish before you adjust another setting.