PETG Filaments
Polyethylene Terephthalate Glycol
PETG (Polyethylene Terephthalate Glycol) sits between PLA and ABS on the difficulty scale: it is tougher and more heat-resistant than PLA, yet far easier to print than ABS. The glycol modifier prevents the brittleness and shrinkage that makes plain PET difficult to print, giving PETG good layer adhesion and a slight flexibility that resists cracking under impact. It is a popular choice for functional parts that need to handle mild mechanical stress or slightly elevated temperatures, and its food-contact-grade variants are used for containers and tool handles. The main challenges are its tendency to string and its stickiness — PETG bonds aggressively to some print surfaces and to itself, which is a strength for layer adhesion but can make prints hard to remove.
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What is PETG used for?
- Mechanical and functional parts requiring moderate toughness
- Containers, clips, brackets and jigs
- Outdoor parts not subject to heavy UV exposure
- Waterproof or moisture-resistant housings
- Prints where some flexibility is an advantage over PLA
How to print PETG
Print PETG between 230 and 250 °C (Polymaker recommends 220–260 °C across their range) with a heated bed at 70–85 °C. No enclosure is required, but avoid strong drafts. Part cooling should be moderate — 30–50 % fan speed gives a balance between surface quality and layer adhesion; too much cooling reduces interlayer bonding. Retraction needs careful tuning to control stringing: start around 4–6 mm for Bowden setups or 1–2 mm for direct drive. PETG is hygroscopic and should be stored with desiccant; a damp spool will string visibly and may produce small bubbles on the surface.
Advantages
- Tougher and more impact-resistant than PLA
- Good heat resistance — viable up to ~80 °C
- Excellent layer adhesion
- Low warping, no enclosure needed
- Food-contact-safe grades available
Limitations
- Prone to stringing — retraction tuning required
- Bonds strongly to some surfaces (glass, PEI) — can pull off coating
- Slightly hygroscopic — moisture causes stringing and bubbles
- Glossy surface shows layer lines more than matte finishes
Common variants
Most PETG on the market is standard clear or opaque PETG. A few notable sub-types exist:
- PETG-CF
- Carbon-fibre-filled PETG for higher stiffness and better dimensional stability; abrasive — use a hardened nozzle.
- PETG-HF / Speed
- High-flow formulas tuned for faster printing (Core XY printers); require slightly higher nozzle temperatures.
- Transparent / clear PETG
- Offers reasonable light transmission; requires very slow print speeds and low fan to minimise haze.