Glass-Filled PETG prints at about 250 °C with a 80 °C bed and 30% part cooling. Usable range 240–265 °C nozzle, 70–90 °C bed. Abrasive — needs a hardened nozzle.
PETG-GFGF PETGGlass Fibre PETGGlass Fiber PETG
Starting settings
Nozzle
240–265 °C (start 250)
Bed
70–90 °C (start 80)
Part fan
20–50% (start 30%)
Wall speed
20–40 mm/s
Max volumetric flow
8 mm³/s
Shrinkage
0.3%
Softens at
80 °C
Enclosure
Helps
Nozzle size
0.4 mm or larger — 0.6 mm recommended
Nozzle material
Hardened steel required — this is abrasive
Drying
65 °C for 6 h
Speed
Slower than plain PETG, 20–40 mm/s, for the same reason as the carbon version: filled material does not tolerate flow spikes.
Bed surface
Textured PEI. Glue stick as a release agent on smooth sheets, same as plain PETG.
Nozzle
Hardened steel, 0.6 mm. Glass fibre is if anything harder on a nozzle than carbon, and it will grind a brass one out of round inside a single spool.
What bites people
Glass fill and carbon fill are not interchangeable. Carbon makes a part STIFFER and more brittle; glass makes it TOUGHER, keeping more impact resistance while still adding rigidity. Choose glass for parts that take knocks, carbon for parts that must not flex.
Hardened steel nozzle required. Printing filled filament through brass is the most common way people quietly ruin a hotend.
Warps and shrinks less than plain PETG. Filled material is a real help on large flat parts.
Prints matte and pale with visible fibre in the surface. Do not expect the gloss of plain PETG.
Still hygroscopic. Dry it like any other PETG.
Safety
Nozzle above 240 °C.
Abrasive — hardened nozzle required.
Do not sand or machine without a mask. Glass fibre dust is a respiratory irritant.