First Layer Adhesion Settings in PrusaSlicer: The Exact Values That Make Prints Stick

The default first layer height in Original Prusa profiles is 0.20 mm, and it is 0.20 mm whether the rest of your model prints at 0.10 or 0.30 mm. That single number tells you most of what you need to know about how PrusaSlicer approaches the first layer: it wants enough flow and squish to bond reliably to the bed, without a layer so thick that it cools unevenly. Get the handful of first layer adhesion settings in PrusaSlicer right and the rest of the print tends to look after itself. Get them wrong and you will chase symptoms up and down the stack for the rest of the job.

There is one thing to understand before touching a slider: PrusaSlicer broadly does what you tell it. If you specify a 0.20 mm first layer height, it calculates flow and movement for 0.20 mm — it does not quietly “help” by tweaking flow behind the scenes the way older Simplify3D builds did. That is a strength, but it also means sloppy values produce a sloppy first layer. Everything below assumes a properly trammed, correctly Live-Z-offset bed. No slicer setting compensates for a mechanical fault, and most “bad first layer” problems are mechanical, not software.

First layer height: why 0.20 mm is the default for a reason

First layer height lives in Print Settings → Layers and perimeters, and you can enter it as an absolute value (0.20 mm) or as a percentage of layer height (e.g. 150%). Its real job is to compensate for an uneven bed — the less flat your surface, the thicker the first layer needs to be to bridge the dips. Because the Original Prusa PEI bed is smooth and well trammed, 0.20 mm works consistently. On a rougher or warped bed, a slightly thicker first layer hides more sins.

Two hard constraints worth knowing:

• Stay within roughly 80% of nozzle diameter for layer height. A 0.15 mm or 0.20 mm micro-nozzle will struggle with a 0.20 mm layer; adhesion suffers because the line geometry goes wrong.
• On an older MK3, there is a firmware floor of 0.15 mm for the first layer height due to the software endstops. You cannot go below it regardless of what the slicer accepts.

Some third-party guides suggest raising the first layer to 0.30–0.35 mm to beat elephant foot. That works mechanically, but it conflicts with the cooling-uniformity rationale behind the 0.20 mm default — thicker first layers cool less evenly. Treat it as a trade-off for a specific problem part, not a universal setting.

First layer extrusion width: the quiet adhesion lever

The Prusa default first layer extrusion width is 120% of a 0.40 mm nozzle, i.e. ~0.45 mm. Wider first-layer lines push more plastic into the bed and overlap each other better, so the whole base bonds more strongly. If your first layer looks slightly starved or shows gaps between lines, nudging this up — from the default 0.42 mm on some profiles to 0.45 mm — often fixes it on its own.

You will see forum “fixes” that crank first layer width to 200% for a fat line. That halves the number of lines on the base and is an extreme last resort, not best practice. Reach for 0.45–0.50 mm long before you reach for 200%.

First layer speed: the setting that quietly surprises people

Slowing the first layer gives the plastic time to wet onto the bed and bond. Official Prusa troubleshooting advice is to drop to about 75% of normal speed for the first three layers, then return to normal; most complete walkthroughs land on 15–25 mm/s for the first layer. Prusa machine profiles bake this in — roughly 20 mm/s on MK3-class machines.

Here is the trap. First layer speed in PrusaSlicer is a single global cap applied to every move on the first layer. If you set it as a percentage, that percentage is evaluated against the speed of each feature being printed — not against the on-printer speed dial. So “80%” means 80% of external perimeter speed, 80% of perimeter speed, 80% of infill speed, and so on. On an XL, where infill runs around 140 mm/s, 80% evaluates to 112 mm/s on the first layer — wildly faster than you intended.

For predictable results, set first layer speed as an absolute value in mm/s. If you genuinely need per-feature control on layer 0:

1. Set first layer speed to 100% in Speed → Modifiers. This is the crucial step — skip it and the modifier below won’t override the global first layer setting.
2. Add a height range modifier covering layer 0 to the first layer height, and set per-feature speeds inside it.

First layer temperature: run it slightly hot

First layer nozzle and bed temperatures live in Filament Settings → Filament → Temperature. The principle is simple: a slightly hotter first layer bonds better, and for warp-prone materials like PETG, ABS and ASA, bed temperature is the more effective lever against corner lift than nozzle temperature.

Prusa’s own ASA profile is a good worked example: nozzle 260 °C, bed 105 °C for the first layer then 110 °C for subsequent layers. The following are community starting points, not official figures — always defer to the range printed on the spool:

A behaviour quirk explains a lot of forum confusion here: on standard Prusa profiles the first-layer nozzle temperature is applied via the Custom Start G-code, not an in-print M104. With 215 °C set for the first layer and 210 °C for other layers, the start G-code sets 215, then the printer drops to 210 at the second layer (height 0.4 mm for a 0.2 mm first layer). If the setting looks like it “isn’t working”, that is why.

Brim: the biggest single adhesion gain

Before you reach for glue stick or other bed treatments, add a brim. Found under Print Settings → Skirt and brim → Brim, it prints a flat collar around the first layer to increase its surface area and anchor the part. It is the right tool for tall objects on a small base and for a bed full of small parts.

• Use at least a 3 mm brim for a meaningful adhesion gain; 5–8 mm for small-footprint parts that lift. On a well-levelled PEI bed, most prints need no brim at all.
• In Advanced/Expert mode you can set a per-object brim: right-click a model → Add settings → Skirt and brim.
• A brim separation gap of ~0.1 mm gives clean removal — but read the next section first, because that gap interacts badly with a default setting.

Elephant foot compensation — and the brim conflict that catches everyone

Elephant foot compensation (EFC) shrinks the first layer to counteract the bulge you get when a hot base is squished onto a hot bed. It is in Print Settings → Advanced → Elephant foot compensation (Advanced or Expert mode; its exact location has moved between versions), and it applies only to the first layer for FDM. Prusa profiles ship with it on by default, usually around 0.2 mm for a 0.4 mm nozzle. The practical ceiling is about half your first layer extrusion width — you should rarely need more than that with a 0.4 mm nozzle. PrusaSlicer 2.2+ also detects thin lines on the first layer and avoids over-shrinking them.

With default PLA settings, elephant foot compensation is 0.2 mm. If you then add a brim, the brim detaches from the model at print time — defeating the point of the brim. This is by design, not a bug.

Because EFC scales the first layer inward, it shrinks the part edge away from the brim. The fix: set elephant foot compensation to 0 whenever you use a brim, so the brim stays attached to the part bottom. You may also need to adjust the skirt so it doesn’t collide with the brim. To find your own EFC value, measure the base over-expansion on a cooled 20 mm calibration cube and halve it — most slicers accept 0.00–0.20 mm in 0.01 mm steps.

Skirt, draft shield and first-layer cooling

The skirt is an outline printed before your parts whose main purpose is to stabilise flow through the nozzle. It is also a free first-layer diagnostic: since it prints first, you can watch it and tweak Live Adjust Z before the part itself commits. The default skirt distance is 6 mm; set it to 0 to attach the skirt to the object and effectively get a brim. Stock Prusa profiles often use a three-layer-tall skirt because a single-layer skirt is fiddly to peel off.

Enable the draft shield for ABS, ASA and other warp-prone materials: it builds a skirt as tall as the tallest object to create a warm micro-climate around the part and keep corners down.

For cooling, head to Filament Settings → Cooling → Disable fan for the first X layers. A value of 3 layers is a sensible default — too-aggressive early cooling is a classic cause of lifting. If parts lift around layers 3–5, reduce first-layer and early fan speed. Exact defaults vary by filament profile, so check what your profile actually does before assuming.

A sensible starting-point table

Work top to bottom, change one thing at a time, and use the skirt to judge each change before the part prints. If you want the exact PLA numbers in more depth, our guide to fixing first layer adhesion in PrusaSlicer and the material-level walkthrough of first layer adhesion issues with PLA go deeper. For a broader diagnostic view, see the real causes and exact fixes for first layer adhesion problems.

Before you hit print

Two tools catch the mistakes above before they waste filament. Run the sliced file through the G-code pre-flight checklist to flag a percentage first-layer speed that will run far too fast, or a brim sitting under 0.2 mm of elephant foot compensation. And if a first layer has already gone wrong, the diagnose a failed print from a photo tool reads the symptom — starved lines, lifting corners, a detached brim — and tells you which of these settings to change.

FAQ

Why does my brim keep detaching from the part in PrusaSlicer?

Because elephant foot compensation is on by default (0.2 mm on PLA profiles) and shrinks the first layer inward, pulling the part edge away from the brim. Set elephant foot compensation to 0 whenever you print with a brim. This is intended behaviour, not a bug.

What should first layer speed be set to in PrusaSlicer?

15–25 mm/s, entered as an absolute value in mm/s. Avoid a percentage: PrusaSlicer evaluates it against each feature’s own speed, not the printer’s speed dial, so “80%” can run the first layer far faster than you expect on fast machines like the XL.

Is 0.20 mm the best first layer height?

For a 0.4 mm nozzle on a flat PEI bed, yes — it is the Prusa default because it balances reliable squish against even cooling. Go thicker only to bridge an uneven bed, and stay within about 80% of your nozzle diameter.

Does the first layer nozzle temperature setting actually work?

It does, but on standard Prusa profiles it is applied through the Custom Start G-code rather than an in-print command, then drops to the other-layers temperature at the second layer. If it looked like it was being ignored, that start-G-code behaviour is the reason.