PETG (polyethylene terephthalate glycol) is a glycol-modified polyester filament that prints nearly as easily as PLA while surviving real mechanical loads, making it the common default for functional indoor parts.
The glycol modification is what makes the material printable. Unmodified PET crystallizes as it cools, producing a cloudy and brittle result; adding glycol suppresses crystallization, yielding a clear, tougher polymer that extrudes reliably at consumer temperatures. The same base resin is used in beverage bottles, which is the origin of both its toughness and its reputation for food safety — a property of the raw material rather than of a printed part, whose layer lines still harbor bacteria.
Printing runs at 230–250 °C with a 70–85 °C bed and no enclosure requirement. The material is hygroscopic and prints with audible popping and surface bubbles when wet, so a dry spool matters more than it does for 📝PLA. It also strings badly and fights clean bridging, and its excellent layer adhesion cuts both ways: supports fuse to the part and resist removal.
📝Bambu Lab publishes a heat deflection temperature of 69 °C at 0.45 MPa, which defines the boundary of the material's usefulness. That figure is below what a dark part reaches sitting in direct summer sun, and well below any engine-adjacent surface, so PETG belongs indoors or in shade. Its solvent resistance is likewise moderate, degrading under brake cleaner and acetone. Comparative positioning lives in 📝3D Printing Filament Types.