Ridges, gaps or rough first-layer lines: reading the lines

This guide is for anyone whose first layer sticks but looks wrong: ridged, scratchy, gappy, wavy or uneven. It covers how to read a first-layer test, how each maker sets nozzle height, and the first-layer settings PrusaSlicer, Cura, OrcaSlicer and Simplify3D document. It doesn't repeat our other first-layer guides, so start with the right one:

How do you read the first-layer lines?

Print a single-layer test before you change any setting. Bambu Lab suggests a simple cube 0.2 mm thick, scaled to fit the bed. Prusa's MK3 and MK3.5 families print a zig-zag pattern during First Layer Calibration, ending in a square.

Prusa describes the target for its MK3 and MK3.5 families: "an even surface... with no gaps between lines, nor ridges." Bambu's version is "clean lines that gently overlap without ridges or air gaps."

Bambu's A2L guide adds a useful limit. It says minor imperfections are normal, and that if "only about 10% of the first layer shows slight line-width variations or minor wrinkles" while the rest prints flat, it generally won't have a noticeable impact on the print.

Step 1: Clean the plate and the nozzle

Bambu and Prusa both start with the plate and the nozzle.

• Plate. Bambu says to wash the build plate with warm water and detergent and to avoid touching it with bare hands. It says oils, dust or residue can leave clean areas printing smooth lines while contaminated areas show "warping, dragging, and incomplete lines." Prusa's cleaning advice for its sheets is in our first-layer adhesion guide.
• Nozzle. Bambu says to check the nozzle is clean and free of clogs, and suggests a manual extrusion test from the screen.
• Wiper and leaks (Bambu A2L). If the first layer is too high, Bambu says to check the nozzle wiper is clean and not bent, and that a leaking nozzle "may interfere with leveling height detection."

Step 2: Set the nozzle height

Each maker sets first-layer height differently. Use the method for your printer.

Prusa: MK3 and MK3.5 families

Run First Layer Calibration from LCD Menu, Calibration, First Layer Calibration, then fine-tune with Live adjust Z (LCD Menu, Live adjust Z, while printing). Prusa says to turn the knob counter-clockwise to bring the nozzle closer. On these printers, Prusa says a Live adjust Z change made while printing "is permanent, not only for the ongoing print."

Each sheet type needs its own setting. Prusa says that because smooth, satin and textured sheets have different thicknesses, "you must use a different First layer calibration for each of them." It also says to rerun First Layer Calibration after changing the nozzle, upgrading the extruder, or moving the printer.

Prusa's first layer issues article (MK2/S to MK3.5/S) warns: "Avoid compensating for a lack of adhesion by setting a lower Live Adjust Z." If lowered too much, the nozzle can damage the steel sheet, and that damage "is not covered by the warranty."

Prusa: CORE One, MK4/S, MK3.9/S and XL

Prusa says these LoadCell printers "calibrate the first layer automatically." To fine-tune during a print, long-press the knob while the first layer prints. That change "will not be saved for the next print." For a lasting change, set Z offset in PrusaSlicer under Printers, General, Z offset, where "a negative value means a more squished first layer."

If problems keep coming back on these printers, Prusa's first layer issues article lists model-specific checks: nozzle height in the Nextruder (CORE One, MK4/S, MK3.9/S), expansion joint orientation (CORE One, MK4/S, MK3.9/S, MK3.5/S), and a LoadCell test under Control, Calibrations & tests.

Bambu Lab

• X1 series. Bambu says to go to Settings, then Print Calibration, and start the calibration. It says auto-calibration adjusts settings including bed leveling and nozzle height.
• A2L. Bambu recommends running Auto Heatbed Leveling under Settings, Maintenance, Calibration, Print Calibration, and turning Auto Heatbed Leveling on when sending each print. To adjust height, go to Calibration, First Layer Calibration and change the value in small steps: positive if too low (for example +0.010 mm), negative if too high (for example -0.010 mm). Bambu notes the distance "cannot be adjusted in real time during printing." It also says a different textured or third-party plate "may require a minor Z-offset adjustment."
• A1 series. If the first layer is too low, Bambu says to turn on Bed Leveling in the slicer before printing, especially after changing the plate. If that doesn't fix it, it says to retighten the heater assembly screws and check the heater assembly buckle, because a loose hotend "may shift downward during printing due to extrusion pressure." Our bed leveling guide covers Bambu's temporary start G-code offset for the A1.
• X1, P1, A1, H2 series and P2S. Bambu's test print guide says to make sure the nozzle isn't loose: check the screws on the X1 and P1 series, and the nozzle fixing buckle on the A1 series, H2 series and P2S.

Creality Ender-3 V3 SE

When the first layer doesn't stick or the nozzle scrapes across the plate, Creality says the Z-axis compensation from automatic height detection "deviates from the actual distance." It suggests adjusting the Z-axis compensation slightly while the first layer prints, and updating to firmware 1.0.4 or later.

Simplify3D

Simplify3D's Z-Axis global G-Code Offset is in Edit Process Settings, G-Code tab. It gives the example that -0.05 mm "will begin printing 0.05mm closer to your build platform," and says "a small adjustment goes a long way!"

Step 3: If it changes across the plate

Bambu's test print guide says that "if parts of the layer look different from others, your bed may not be level, or it might be far or too close to the bed." For varying texture across the plate, it says "you need to perform an automated bed leveling before trying any other adjustments." Prusa's calibration guide says that "if the width of the line varies across its length, you may have to do some Bed Level Correction."

Our bed leveling guide covers each maker's leveling, tramming and side-by-side correction.

Step 4: First-layer speed, temperature and line width

Once the height looks right, these slicer settings change how the first layer goes down. Start from your printer maker's profile and change one at a time.

Speed

• Cura: Initial Layer Speed, where "a lower value is advised to improve adhesion to the build plate."
• OrcaSlicer: Initial layer speed covers walls, and Initial layer infill covers solid infill. The wiki says printing solid infill "too fast may result in high internal stresses (increased risk of warping), poor layer uniformity, or adhesion failures."
• PrusaSlicer: First layer speed "will be applied to all the print moves of the first layer" when set in mm/s, or "will scale the default speeds" as a percentage.
• Simplify3D: "if you set a first layer speed of 50%, it means that your first layer will print 50% slower than the rest of your part."
• Bambu: its test print guide gives an example of 30 mm/s for the outer wall and 60 mm/s for infill on the first layer.
• Prusa printers: Prusa's first layer issues article suggests turning the knob during a print to bring speed down to about 75% for the first three layers.

Temperature

The OrcaSlicer wiki says a higher first-layer nozzle or bed temperature can improve adhesion, but to be cautious of deformations such as elephant foot. PrusaSlicer's First layer nozzle temperature tooltip describes it as "nozzle temperature for the first layer." Use your filament maker's range, and see our elephant's foot guide if the base starts to flare.

Line width and height

• PrusaSlicer: the First layer extrusion width tooltip says "you can use this to force fatter extrudates for better adhesion." A percentage "will be computed over first layer height." First layer height lets you print "a thicker bottom layer to improve adhesion and tolerance for non perfect build plates."
• Cura: Initial Layer Line Width is a percentage of the normal line width. "Increasing this could improve bed adhesion." Initial Layer Height says "a thicker initial layer makes adhesion to the build plate easier."
• OrcaSlicer: the wiki says "a wider first layer (with a higher first layer height) improves bed adhesion and compensates for uneven build surfaces." For a 0.4 mm nozzle, its layer height page recommends a 0.25 mm first layer, with a maximum of 65% of nozzle diameter.

Step 5: Rule out flow

Some rough first layers aren't about height. Bambu's test print guide says cracks on the first layer can come from "a dirty nozzle or the flow rate not set correctly," and that a mix of over-squished areas and gappy areas "suggests that the flow rate may not be calibrated correctly." If height and leveling check out, see our under-extrusion and over-extrusion guides for flow calibration.

What if the lines look right?

Prusa says that if the first layer looks like its "good" example but you still have adhesion problems, "your problem lies somewhere else, like a dirty/greasy sheet, print-settings, bed leveling/XYZ calibration, or under-extrusion." At that point, our first-layer adhesion guide is the next stop.

A sensible order

1. Print a single-layer test and compare it with the table above.
2. Clean the plate and the nozzle.
3. Run your printer's calibration or leveling, especially after changing plates.
4. Adjust nozzle height in small steps with your printer's own tool, one test at a time.
5. If the lines change across the plate, work through our bed leveling guide.
6. Fine-tune first-layer speed, temperature and line width from your maker's profile.
7. If height and leveling are right but lines are still uneven, check flow.

How this guide was checked

This is a research-based guide. We haven't printed these tests for it. Every symptom, menu path and setting name comes from the Prusa Research, Bambu Lab, Creality, Simplify3D, PrusaSlicer, Cura and OrcaSlicer sources listed above, retrieved on 2026-10-11. Printer steps are kept to the models each maker's page names. Read more in our editorial standards.

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