For a 0.4 mm nozzle, the single most reliable first-layer height in OrcaSlicer is 0.25 mm — 62.5% of the nozzle diameter — paired with a first-layer line width of around 110%, a first-layer speed near 20–30 mm/s, and the part-cooling fan off for layer 1. Those four numbers do most of the work. Everything else is fine-tuning for a specific material, bed or defect. This guide walks through each first layer settings OrcaSlicer control, what it actually changes mechanically, and the exact values that get a part to grip the plate on the first attempt.
OrcaSlicer treats the first layer as a separate print from everything above it: its own height, line width, speed, temperature, cooling and — crucially — its own flow. Get that foundation right and the rest of the model follows. Get it wrong and you waste the whole print.
First layer height: thicker is more forgiving
The first layer height is set independently from the rest of the print (variable initial_layer_print_height). A thicker first layer pushes more melted material into the texture of the build surface, bridges small bed imperfections, and gives the plastic more volume to bond with. That is why going thinner almost never helps adhesion — a too-thin first layer is a classic cause of first-layer under-extrusion.
OrcaSlicer’s recommended value for a 0.4 mm nozzle is 0.25 mm, with an upper limit of 65% of nozzle diameter. The official per-nozzle reference:
| Nozzle diameter | Recommended first layer height |
|---|---|
| 0.2 mm | 0.12 mm |
| 0.3 mm | 0.18 mm |
| 0.4 mm | 0.25 mm |
| 0.5 mm | 0.30 mm |
| 0.6 mm | 0.35 mm |
| 0.8 mm | 0.45 mm |
| 1.0 mm | 0.55 mm |
One trap worth knowing: some shipped profiles — Bambu’s in particular — default the first layer to 0.20 mm regardless of the layer height you choose, because the standard was changed a few versions ago to use 0.20 mm across the board. That is not a universal OrcaSlicer rule, and it is not the strongest value for adhesion. For a 0.4 mm nozzle the practical sweet spot sits at roughly 0.2–0.28 mm; 0.25 mm is the reliable default. Dropping below 0.2 mm makes adhesion fussier, not better.
First layer line width: widen the contact patch
First layer line width (initial_layer_line_width, visible in Advanced mode) controls how wide each extruded line is on layer 1. A wider line lays down more material and increases the contact patch against the bed, which both improves grip and compensates for a slightly uneven surface.
Line width can be entered as a fixed value in millimetres or as a percentage of nozzle diameter — the percentage form auto-scales when you change nozzle, so it travels better between profiles. A good general starting point is 100% of nozzle diameter. At exactly 100%, the extrudate leaves the nozzle slightly narrower, then flattens as it is squished onto the layer below to match the nozzle size. For the first layer specifically, nudge it to 110% (about 0.44 mm on a 0.4 mm nozzle); fixed-value guidance of 0.42–0.45 mm achieves the same wider squish. Stay below roughly 150% — beyond that you move into over-extrusion, with blobs and poor surface quality.
There is an interaction worth flagging: the first layer line width also overrides the brim’s and skirt’s line width. So if you widen it for adhesion, your brim and skirt get wider too — usually desirable, but worth knowing before you wonder why your brim changed.
First layer speed: slow enough to bond
First layer speed (first_layer_speed, mm/s or %) governs how long the filament sits against the bed before the nozzle moves on. Slower gives the plastic more time to wet into the surface texture and form a bond. The sensible ranges split by printer class:
- Budget / bowden machines: 20–30 mm/s
- High-speed machines: 40–50 mm/s
Even fast hardware slows down here: the Bambu Lab X1C can push infill at 300 mm/s but still drops its first layer to around 50 mm/s. A conservative, proven set on a direct-drive Ender 3 S1 Plus with PLA is 15 mm/s first layer, 20 mm/s first layer infill, 60 mm/s initial layer travel.
Two companion settings matter. First layer infill speed (first_layer_infill_speed) can run faster than the perimeters, because the solid infill is not defining the part’s edge against the bed. And the first layer travel speed is worth keeping modest — slower travel moves reduce the chance of the toolhead catching and lifting freshly laid, still-soft material.
First layer temperature: a little hotter, then step down
OrcaSlicer’s filament profiles carry separate first-layer nozzle and bed temperature fields, and most of them already run the first layer 5–10 °C hotter than the rest. The extra heat lets the plastic flow into the build plate’s texture and form a stronger mechanical key; after layer 1 the temperature steps down to the normal printing value.
A conservative, repeatable PLA set on textured PEI:
| Setting | First layer | Other layers |
|---|---|---|
| Nozzle temperature | 210 °C | 205 °C |
| Bed temperature | 60 °C | 60 °C |
If you are fighting elephant’s foot — the flared, over-squished base — drop the bed temperature by 5–10 °C, or schedule it to fall after the first layer. That stops the bottom layers staying soft and sagging under the weight of the model above them. It is a cleaner fix than attacking the symptom with flow alone.
First layer cooling: fan off for layer one
Cooling lives in the Filament → Cooling tab, and the first layer should almost always print with the fan off so it bonds to the bed on residual heat. Three variables control the ramp:
- No cooling for the first N layers (
disable_fan_first_layers, default 1) — layers printed with zero fan. - Full fan speed at layer (
full_fan_speed_layer, default 3) — where the fan reaches full part-cooling speed. - Between those two layers the fan speed ramps up linearly from 0% to the maximum.
For PLA: first-layer fan 0%, other layers 100%, no cooling for the first 1 layer. PLA takes full cooling after layer 1 for the crispest detail and best overhangs. PETG is different — it bonds on residual heat, so keep overall cooling low (around 30–50%), raise the fan only on overhangs and bridges, and keep it off for the first layer. Push full cooling on PETG and you get stringing and brittle, weakly bonded layers.
There is also a dedicated first-layer fan speed override that forces an exact fan percentage on layer 1, ignoring the other cooling rules. Its real use is protecting printed toolhead parts — Voron-style ABS/ASA ducts, for instance — from a hot bed: a trickle of airflow cools the ducts without the full blast that could, in some conditions, hurt first-layer adhesion. Most users never need it.
First layer flow ratio: the setting with a scope trap
This is where people lose hours, so read carefully. OrcaSlicer exposes several flow-ratio variables, including first_layer_flow_ratio and bottom_solid_infill_flow_ratio, once you enable “Set other flow ratios” (Advanced mode, Quality tab, just under the filament choice). The actual flow applied is the ratio multiplied by the filament flow ratio (and the object flow ratio if you’ve set one).
The two gotchas that catch nearly everyone:
- First-layer flow ratio does not affect brims and skirts. It is scoped to the model’s first layer, not the adhesion aids around it.
- Bottom Surface Flow Ratio only changes first-layer solid infill — not the first-layer walls, brim or skirt. This has been confirmed across multiple versions, including v2.3.1. Turn it down and your bottom infill extrudes less, but the perimeter and brim lines keep extruding at full flow, so they can look over-extruded by comparison.
Despite that quirk, Bottom Surface Flow Ratio is the right lever for mild first-layer over-extrusion — a nozzle sitting slightly closer to the bed than expected needs a touch less flow. Typical corrective values:
| Symptom | Bottom surface flow ratio |
|---|---|
| Slight over-extrusion / ridged bottom | 0.95 (95%) |
| Marked over-extrusion | 0.85 (85%) |
If the whole first layer — walls and infill together — is consistently over- or under-fed, that is a Z-offset or filament flow calibration issue, not something to paper over with the bottom-surface ratio alone.
A sensible starting profile (0.4 mm nozzle, PLA)
| Setting | Value |
|---|---|
| First layer height | 0.25 mm |
| First layer line width | 110% (≈0.44 mm) |
| First layer speed | 20–30 mm/s |
| First layer infill speed | Up to ~50% faster than perimeters |
| First layer nozzle temp | +5 °C over normal |
| No cooling for first N layers | 1 |
| First layer fan | 0% |
| Bottom surface flow ratio | 1.0, drop to 0.95 only if over-extruding |
If your parts still lift, the problem is usually mechanical before it is in the slicer. For the full material-specific breakdown, our guide on OrcaSlicer first layer settings for adhesion drills into the exact values, and first layer adhesion issues with PLA covers the root causes that no setting will fix. If something’s already failed on the bed, you can upload a photo to our Diagnose tool and get concrete slicer changes back.
FAQ
What is the best first layer height in OrcaSlicer for a 0.4 mm nozzle?
0.25 mm — 62.5% of the nozzle diameter, and OrcaSlicer’s own recommendation. The practical range is 0.2–0.28 mm; staying at or above 0.2 mm keeps adhesion forgiving. Below 0.2 mm, adhesion gets fussier and first-layer under-extrusion becomes more likely.
Why does my first layer flow ratio not change the brim or walls?
By design. The first-layer flow ratio does not affect brims or skirts, and Bottom Surface Flow Ratio only affects first-layer solid infill — not the perimeters, brim or skirt. If walls and infill are both off, calibrate your flow ratio and Z-offset rather than relying on the bottom-surface ratio.
Should the fan run on the first layer?
No, as a rule. Keep the part-cooling fan off for layer 1 so the plastic bonds to the bed on residual heat. OrcaSlicer’s defaults — no cooling for the first 1 layer, full fan by layer 3 — ramp it up linearly after that. PLA then runs 100% fan; PETG stays low at 30–50%.
How do I stop elephant’s foot on the first layer?
Drop the bed temperature by 5–10 °C after the first layer so the base stops staying soft and spreading under the model’s weight. Enabling elephant foot compensation and checking your Z-offset help too, but the bed-temperature step is the most direct mechanical fix.
Before you commit a long print, running it through a G-code pre-flight check catches first-layer and flow mistakes while they’re still cheap to fix — so the foundation is right before the plate ever heats up.