PETG-GF

PETG-GF is ordinary PETG with chopped glass fiber added (typically 15–20%). The glass makes parts noticeably stiffer and more dimensionally stable, cuts warping and shrinkage, raises heat resistance, and leaves a pleasant matte surface. The trade-off is abrasiveness: this filament wears down a brass nozzle, so a hardened nozzle is required.

What it is good for

• Functional parts: brackets, holders, enclosures where stiffness matters
• Jigs, fixtures and tooling that must hold their dimensions
• Parts running in mild heat where plain PETG is no longer enough
• Items that need impact toughness without the brittleness of carbon composites

Where NOT to use it

• Small models with thin, sharp details — glass fiber coarsens the surface
• Transparent parts — the filler makes the plastic matte and opaque
• Parts under high, nylon-level heat — use PA or PET-CF instead
• Printers still on a stock brass nozzle without a hardened swap

How to print

• Nozzle temperature: 240–270 °C
• Bed temperature: 70–85 °C
• Nozzle: hardened steel, 0.4 mm or larger; all-metal hotend
• Speed: 30–60 mm/s — glass fiber dislikes rushing
• Cooling: moderate, 20–40% — too much breaks layer adhesion
• Adhesion: warm bed plus glue stick as a release layer; don't squish the first layer

Drying and storage

PETG-GF is hygroscopic — it absorbs moisture from the air even more eagerly than plain PETG. Wet filament bubbles, hisses, and produces porous, weak walls.

• Drying: 65 °C for 6–8 hours
• Storage: airtight box with silica gel, ideally print straight from a dryer
• Signs of moisture: hissing and steam, surface bubbles, loose walls

Pros and cons

• Noticeably stiffer and more dimensionally stable than plain PETG
• Low warp, prints without an enclosure
• Matte surface that hides layer lines
• Less brittle than carbon composites — better impact resistance

• Abrasive: needs a hardened nozzle and all-metal hotend
• Absorbs moisture faster — drying is mandatory
• Reproduces fine detail worse because of the filler
• Opaque and always matte — not for clear decorative models