For PETG in PrusaSlicer, start here: 230 °C nozzle on the first layer and 240 °C for every layer after it, bed at 85 °C first layer and 90 °C after, a 0.20 mm first layer height, and a first-layer speed of around 20 mm/s. On Prusa hardware those values are already baked into the pre-configured profiles, so a Generic or Prusament PETG profile loads them for you. The two-temperature trick — cooler first layer, hotter body — is deliberate: 230 °C lays down a slightly less sticky bead that is easier to release from the sheet, while 240 °C after that improves layer-to-layer bonding and mechanical strength.
That is the quick answer. The part that actually decides whether your PETG first layer works is not the flow numbers — it is Z offset and bed preparation. Nine times out of ten a failed PETG first layer is mechanical (nozzle height or an unsuitable sheet), not a slicer flow problem. So before you start fiddling with extrusion multipliers, get the petg first layer settings prusaslicer basics right in the order below.
The baseline PETG first-layer settings in PrusaSlicer
| Setting | First layer | Other layers | Where in PrusaSlicer |
|---|---|---|---|
| Nozzle temperature | 230 °C | 240 °C | Filament Settings → Filament → Temperature → Nozzle |
| Bed temperature | 85 °C | 90 °C | Filament Settings → Filament → Temperature → Bed |
| Layer height | 0.20 mm | as chosen | Print Settings → Layers and perimeters |
| First layer speed | ~20 mm/s | 40–60 mm/s | Print Settings → Speed → First layer speed |
| First layer extrusion width | 0.5 mm (0.4 mm nozzle) | — | Print Settings → Advanced → First layer |
| Part cooling fan | Off for layers 1–2 | ~50% | Filament Settings → Cooling |
Check your actual loaded profile before trusting any number. The defaults genuinely vary by PrusaSlicer version and by Generic versus Prusament PETG. The Prusa knowledge base lists 230/240 °C, but at least one recent build has shipped Prusament PETG with 250 °C first layer, 250 °C other layers and the bed at 85 °C both. Neither is wrong — they are different profiles tuned to different filament. Open Filament Settings and read the values that are actually there rather than assuming.
First layer height: 0.20 mm by default, 0.30 mm when PETG fights you
Original Prusa print profiles standardise on a 0.20 mm first layer regardless of the layer height you pick for the rest of the model. That thickness is a sweet spot: enough flow and squish to stick reliably, but not so thick that uneven cooling shows through. Go too thin and the texture of the sheet starts telegraphing into the surface; go too thick and the bead can cool unevenly.
PETG is a special case, though. Because it is viscous and slow to set, a thicker first layer of 0.28–0.32 mm often behaves better — it balances release against adhesion and reduces the chance of the nozzle dragging through tacky plastic. Several users report that moving to 0.30 mm with a 20 mm/s first layer “just works”. One caveat worth stating plainly: changing first layer height will almost always mean re-tuning your Live Z / first-layer calibration, because you have changed how much material sits between nozzle and bed.
First layer speed: slow it right down
For the body of a PETG print, 40–60 mm/s is fine. For the first layer, drop to 15–20 mm/s. The reasoning is physical, not superstition: a slow first layer gives each bead time to wet into the sheet and bond, and it reduces the pull on freshly laid lines that are still molten. PETG sets slowly, so it needs that extra dwell time more than PLA does. PrusaSlicer’s generic first-layer baseline (20–25 mm/s, or 75% of normal) is already in the right ballpark; for sticky engineering PETG, bias to the lower end.
Z offset is the setting that actually decides it
This is the single most important point in the whole article. PrusaSlicer does not change Z offset based on filament type. Load PETG instead of PLA and the slicer keeps the same Z value unless you move it yourself. That matters because PETG and PLA want different nozzle heights — and getting this wrong is what produces most “PETG won’t stick” and “PETG blobs all over the nozzle” complaints.
Here is a genuinely contested point, and you deserve both sides. Prusa’s own documentation says PETG and other high-temperature materials “require to be squished… slightly more” because they tend to warp. Yet widespread community practice is the opposite: experienced users run PETG with less squish — the nozzle slightly higher — to stop the sticky melt dragging and blobbing. Concrete examples from MK3S+ users:
- PLA Live Z at −1.455, PETG at −1.435 (less negative = less squish for PETG).
- Another user: PLA at live Z 0.990, PETG at 0.980 — again, PETG nudged slightly higher.
The practical takeaway: start from your dialled-in PLA height, then adjust in 0.025 mm steps and read the lines. A correct PETG first-layer line looks slightly flattened on top with no gaps and no transparent grooves. If lines are rounded with gaps, lower the nozzle (more negative). If they look glassy, scraped or smeared, raise it. Trust what you see on the sheet over any single stated number.
Set it in the right place for your printer
On load-cell printers (MK4, CORE One, XL) set Z offset in PrusaSlicer under Printers → General → Z offset, where a negative value means a more squished first layer. On MK3-style printers, the cleaner workflow is to leave your PLA Live Z alone on the LCD and make the PETG adjustment in the slicer profile — that way a future recalibration (after, say, a firmware update) doesn’t wipe your material offset. If you do use Live Adjust Z on the LCD, remember you must long-press the knob while the first few layers are printing; change it later and it won’t take.
If you’re still chasing a stubborn first layer across materials, our PrusaSlicer first-layer adhesion guide walks the fixes in order, and the Diagnose tool will read a photo of your first layer and tell you which way to move Z.
Bed surface and release agent: the warning that saves your sheet
This is the part that trips up newcomers to PETG, and it can cost you a steel sheet. On a Prusa Smooth PEI sheet, PETG adheres too strongly and can tear the PEI off when you remove the print. PETG, ABS, ASA, XT and CPH are all flagged as exceptions by Prusa for exactly this reason.
- Use the textured or satin sheet for PETG. The satin sheet gives the same smooth bottom finish but is safe with PETG; the textured sheet is likewise fine.
- If you must use smooth PEI, apply a separator first — a glue stick or a glass-cleaner (Windex-type) film. The glue acts as a release layer so the PETG bonds to the glue, not permanently to the PEI.
- Do not wipe the sheet with IPA or acetone right before PETG. Clean PEI + PETG bonds extremely hard; removing the print can be near impossible and may delaminate the sheet. Acetone before PETG is likewise a mistake.
- Scrub with dish soap and water when switching between PLA and PETG. Their residues are mutually incompatible and alcohol alone won’t shift them.
The Prusa magnetic heatbed with its removable PEI spring steel sheets tops out at 120 °C, so 85–90 °C for PETG is well within range. If you run a different bed, note that some users and data sheets happily print PETG on a bed as low as 60–70 °C — brand-dependent, so treat 85 °C as a reliable starting point rather than gospel.
Cooling: keep the fan off early
PETG needs far less cooling than PLA, and the first layers need none. Run the fan off for the first two layers, then bring it to roughly 30–50%. The mechanism matters: if you blast full fan at layer one, the polymer chains don’t have time to entangle across the interface and you lose interlayer strength. Higher melt temperature improves that bonding, which is why the hotter 240 °C body temperature and a restrained fan work together. Third-party PETG profiles (for example Numakers’) land in the same zone — keep fan always on, min 25%, max 50%, bridges 50%.
First layer extrusion width and brim
Set First Layer Extrusion Width to 0.5 mm for a 0.4 mm nozzle — a fixed value, not a percentage at this height. Wider first-layer lines (120–150% of nozzle diameter, i.e. 0.48–0.60 mm) push more material into the bed and improve adhesion. For tall or small-footprint PETG parts, add a 5 mm brim; it costs seconds to remove and buys you insurance against a corner lifting mid-print.
Dry filament matters more than you’d think
Wet PETG stipples and strings the first layer and hurts adhesion. If the spool has been open a while, dry it at 65 °C for 4–8 hours (4–6 h is a common third-party figure; Polymaker and Bambu cite 6–8 h). A dry spool often fixes a “bad first layer” that no slicer setting could.
The fast troubleshooting checklist
- First layer not sticking? Raise the bed to 75–80 °C if it’s below that, apply a glue stick on PEI or glass, increase first layer height to 0.28–0.32 mm, confirm the fan is fully off for layers 1–2, and drop first-layer speed to 20 mm/s.
- Rounded lines with gaps? Lower the nozzle (more negative Z) in 0.025 mm steps.
- Glassy, scraped or smeared lines? Raise the nozzle in 0.025 mm steps.
- Nozzle dragging blobs through the layer? PETG wants less squish — nudge Z higher, not lower.
- Print welded to a smooth sheet? Switch to satin/textured, or always use a glue separator on smooth PEI.
Want to catch these before you commit a long PETG print? Run the plate through our G-code pre-flight checker or, if you run several machines, Ask The Nozzle’s Printer Farm watches each job with camera-based AI failure alerts and banks good parts into stock with a true cost per part.
FAQ
Why does PrusaSlicer use 230 °C on the first PETG layer but 240 °C after?
The cooler first layer lays down a slightly less sticky bead that releases more cleanly from the sheet, while 240 °C on subsequent layers improves chain entanglement and interlayer strength. It’s a deliberate two-temperature strategy built into Prusa’s profiles.
Does PETG need more or less first-layer squish than PLA?
This is genuinely contested. Prusa’s documentation says high-temperature materials want slightly more squish; most experienced users run PETG with slightly less squish (nozzle marginally higher) to stop the sticky melt dragging. Start from your PLA height, adjust in 0.025 mm steps, and judge by the line appearance.
Can I print PETG on a Prusa Smooth PEI sheet?
Only with a separator. PETG bonds so hard to clean smooth PEI that it can tear the coating off. Use the satin or textured sheet, or apply a glue stick / glass-cleaner film first. Never wipe the sheet with IPA or acetone immediately before PETG.
Why won’t my PETG first layer change on the printer’s LCD?
On MK3-style printers, Live Adjust Z only takes if you long-press the knob while the first few layers are actually printing. Change it later and it won’t apply. The cleaner approach is to set the PETG offset in the slicer and leave your PLA Live Z untouched.