PETG print settings: a practical guide for getting it right

What makes PETG different from PLA

PETG (polyethylene terephthalate glycol) sits between PLA and ABS in terms of difficulty. It prints hotter, strings more readily, and is fussier about moisture than PLA, but it does not warp like ABS and tolerates higher temperatures in use — typically around 75-80°C before it starts to deform. Those properties make it popular for functional parts: brackets, enclosures, clips, anything that might sit in a warm car or near electronics.

The catch is that PETG is less forgiving of incorrect settings than PLA. Too cold and layers delaminate. Too hot and you get strings everywhere. Getting it dialled in takes a few test prints, but once it is right it is consistent.

Starting temperatures

A reliable starting range for most PETG filaments is 235-245°C at the nozzle and 70-80°C at the bed.

Go to the lower end (235°C) for brands with well-controlled formulations and good documentation — Prusament PETG, eSUN PETG, and most Bambu filaments include a data sheet with their recommended range. Go to the upper end (245-250°C) if you are seeing poor layer adhesion, rough surfaces, or the extruder is clicking under load.

First layer temperature: Some slicers let you print the first layer 5°C hotter than the rest of the print. This helps adhesion and is worth enabling if PETG is struggling to stick.

Bed material matters:

• Textured PEI (e.g. textured spring steel): Works well for PETG with no adhesive. Expect strong adhesion — sometimes too strong. Let the bed cool to around 40°C before removing parts or you may damage the sheet.
• Smooth PEI: PETG can bond so aggressively to smooth PEI that you will tear chunks off the sheet or the part. A very thin layer of glue stick (Pritt stick) acts as a release agent.
• Glass: Works, but requires hairspray or glue stick. Clean regularly.

Print speed

PETG likes to go slower than PLA. A safe all-round speed is 40-60 mm/s on perimeters and top or bottom surfaces, with infill up to 80 mm/s if your machine is well-calibrated.

Running faster tends to cause:

• Under-extrusion on corners and overhangs
• Poor layer bonding
• More stringing, because the filament is still semi-molten when the head moves

First layer speed: Keep this at 20-30 mm/s. PETG is more viscous than PLA at temperature and needs time to settle properly before the next layer lands on it.

Retraction

Stringing is PETG's main nuisance. Retraction settings that work for PLA will often need adjusting.

For a direct drive extruder (Bambu, Prusa MK4, most modern machines): start at 1.0-2.0 mm retraction at 25-35 mm/s.

For a Bowden setup: start at 4.0-6.0 mm retraction at 30-45 mm/s.

If you are still seeing strings after adjusting retraction, temperature is usually the culprit. Try dropping 5°C and re-testing before increasing retraction distance further. Excessive retraction with PETG can pull the molten core back far enough to cause jams, particularly on direct drive systems.

Also check:

• Travel speed: Faster travel (200 mm/s or more) leaves less time for ooze, which reduces stringing without touching retraction.
• Coasting: Cutting extrusion slightly before the end of a line (0.2-0.5 mm) helps.
• Wipe on travel: Most slicers have an option to wipe the nozzle on the part outline before travel moves. Useful for PETG.

Cooling

PETG needs less cooling than PLA — typically 30-50% fan speed, not 100%. Too much cooling causes poor layer adhesion and can lead to delamination on tall prints.

Rules of thumb:

1. First two layers: fan off entirely. 2. Layers 3-5: ramp fan to around 20%. 3. Remaining layers: 30-50%, higher for detailed overhangs, lower for solid structural prints.

Some filaments — particularly high-fill or carbon-fibre PETG blends — do better with even less fan. Check the manufacturer's spec sheet if one is provided.

Layer height and line width

A safe starting layer height is 0.2 mm on a 0.4 mm nozzle (50% of nozzle diameter). You can go up to 0.25 mm for functional parts where resolution is not critical, or down to 0.15 mm for better detail. PETG is less forgiving than PLA when you push layer heights close to the nozzle diameter.

Line width can be left at the slicer default (usually 100-120% of nozzle diameter). Some users find widening perimeter line width slightly — to 0.45 mm on a 0.4 mm nozzle — helps adhesion and reduces gaps between perimeters.

PETG-CF (carbon fibre PETG) settings

PETG-CF is standard PETG compounded with short carbon fibres. It is stiffer, lighter, and usually less stringy than unfilled PETG, but it is abrasive. You must use a hardened nozzle — hardened steel or ruby-tipped. Running PETG-CF through a brass nozzle will wear it down noticeably within a few prints.

Adjusted settings for PETG-CF:

• Nozzle temperature: 250-265°C — CF-filled blends need more heat to flow well
• Bed temperature: 75-85°C
• Print speed: 30-50 mm/s — CF filaments are more brittle when flowing fast
• Retraction: Reduce by 20-30% compared to unfilled PETG — carbon fibres can jam if the melt zone is disrupted by large retractions
• Cooling: 0-30% — CF-PETG is sensitive to rapid cooling and will split layers if cooled too aggressively

Expect a matte, slightly rough surface finish rather than the semi-gloss you get from unfilled filament.

PETG-HF (high flow) settings

High-flow PETG is formulated to extrude more easily at temperature, allowing faster printing without under-extrusion. Bambu sells PETG-HF; other manufacturers use similar names.

1. Start with the manufacturer's profile if your slicer has one. Bambu Studio includes dedicated profiles for Bambu PETG-HF. 2. If building from scratch: start at 250-260°C, 75°C bed, and perimeter speeds of 80-120 mm/s. 3. Reduce cooling slightly compared to your standard PETG profile — HF formulations still do not like excessive fan. 4. Run a retraction calibration from scratch. HF PETG can behave quite differently from standard PETG at your existing retraction settings.

PETG-HF at higher speeds can produce slightly rougher surface finishes than standard PETG running at its natural pace. If surface quality matters, slow down.

Moisture

PETG absorbs moisture from the air faster than many people expect. Wet filament shows up as:

• Hissing or popping sounds during printing
• Rough, bubbly surface texture
• Reduced layer strength
• Excessive stringing even with tuned retraction

Store filament in a dry box or sealed bag with desiccant and this is rarely a problem. If a reel has been sitting open on a shelf in a typical UK home for a week or more, dry it before use: 6-8 hours at 60-65°C in a filament dryer or food dehydrator. Oven drying is possible but risky unless your oven reliably holds below 70°C without temperature spikes.

First layer calibration

PETG needs to be slightly further from the bed than PLA. If you are transferring a Z-offset from a PLA calibration, try raising the nozzle by 0.02-0.05 mm. Over-squishing the first layer causes it to spread unevenly and can create adhesion problems on subsequent layers.

A well-calibrated first layer in PETG looks slightly glossy, with lines just touching each other but not merging into a completely flat sheet.

When to mail it in

If you have worked through temperature, retraction, moisture, and speed adjustments and PETG is still failing consistently, the problem may be hardware-side — a worn nozzle, an inconsistent bed heater, or a poorly calibrated extruder. Hark Tech offers mail-in diagnostics and repair for FDM printers including Bambu, Creality, and Prusa machines. Send a description of the problem and, if possible, a short video of the failure, via the contact page. Most diagnostics come back with a clear cause and a quote within a few working days.