PETG

What PETG is good at

Prusa describes PETG as easy to print, suited to beginners and strong and heat resistant enough for technical parts (Prusa prints parts of its own printers in it). Typical uses are mechanical parts, holders, clamps and waterproof parts. It has very little thermal expansion, so it resists shrinking and warping and works for large models, and Prusa rates it for indoor and most outdoor use below 80 °C Rule of thumb.

Prusa's list of limits: prone to stringing, weak on bridges and overhangs, not ideal for fine detail, bonds very strongly to the print surface, supports are hard to remove, and it only dissolves in dangerous chemicals.

Two makers, two sets of numbers

Setting	Prusa knowledge base (its PETG profile)	Polymaker PolyLite PETG TDS
Nozzle	230 °C first layer, 240 °C after Starting point	230 to 260 °C Maker spec
Bed	85 °C first layer, 90 °C after Starting point	70 to 80 °C Maker spec
Cooling fan	Off for the first layers, then about half Starting point	Off to 20 percent Maker spec
Surface	Textured or satin sheet; avoid smooth PEI	PC and textured PEI, glue when needed Maker spec
Drying	Prusament PETG: 55 °C for 6 hours Maker spec	65 °C for 6 hours Maker spec

Prusa itself recommends using its slicer profiles, and profiles are updated over time. The spool's printed range and a temperature tower on your own printer beat any table, including this one.

Strength, flexibility and heat

Prusa calls PETG tough and durable. Polymaker's PolyLite PETG data gives elongation at break of about 8 percent along the layers and about 3 percent across them, a glass transition of 81 °C and a heat deflection temperature of 75 °C at 1.8 MPa Maker spec, compared with 58 °C for the same maker's PLA. Prusa notes that for strength you should add perimeters rather than infill, and that turning the part fan off and printing hotter improves layer bonding at the cost of detail. See Walls and Perimeters.

Bed adhesion: too much, not too little

PETG's common bed problem is sticking too well. Prusa highly recommends textured powder-coated or satin sheets and says to avoid smooth PEI, because adhesion may be strong enough to damage the sheet; if you must use smooth PEI, apply glue stick first as a release layer. Keep the surface clean. See Build Plates and Surfaces.

Stringing and cooling

Prusa names stringing as PETG's main print-quality issue and suggests higher retraction and a lower nozzle temperature, within the maker's range. Cooling helps detail and reduces oozing but weakens layer bonds, so most profiles keep the fan low. Work through Stringing and Oozing and the retraction test before changing several settings at once.

Moisture, storage and drying

Finished PETG parts are water and humidity resistant, but the filament still absorbs moisture before printing; it is in Prusa's drying table. Wet PETG strings heavily and can pop or bubble. Store spools sealed with desiccant and dry them at the temperature the maker gives. See Drying and Storing Filament.

Enclosure and ventilation

PETG does not need an enclosure for warping: Polymaker's PolyLite PETG data sheet lists a closed chamber as not needed Maker spec, and Prusa describes PETG as low-warping. Ventilate the room as you would for any FDM printing; see FDM Emissions and Ventilation.

Post-processing

• Sanding: Prusa says PETG sands both dry and wet.
• Smoothing: only possible with dangerous lab solvents, per Prusa. Not a home process.
• Supports: they bond firmly. Increase the support gap or use an interface layer; see Support Settings.
• Food contact: Prusa does not recommend printed PETG for dishes or food containers, because layer grooves can harbor bacteria.

Common PETG failures

What you see	Usual cause	Where to go
Strings and wisps everywhere	Temperature, retraction, wet filament	Stringing
Blobs that catch the nozzle	Oozing residue on the nozzle, nozzle too low	Over-Extrusion
Print tore a chunk out of the sheet	PETG on smooth PEI without a release layer	Build Plates
Droopy overhangs and bridges	Low cooling (needed for strength)	Overhang Droop