First Layer on My Prusa Mini

Getting the first layer right is one of the most frustrating and most rewarding parts of 3D printing. Recently, I went through a series of prints on my Prusa Mini that simply refused to behave. Sometimes the filament dragged across the bed without sticking, other times it bonded so tightly that large test sheets tore apart when I tried to remove them. This was the beginning of a longer journey into calibration, cleaning, and learning what the printer was trying to tell me.

The First Problem Signs

My earliest prints showed all the classic symptoms of a poorly tuned first layer. There were gaps between lines, uneven adhesion, and an inconsistent surface that alternated between glossy streaks and weak stringy areas. It was clear that my Live Z offset wasn’t dialled in, but what complicated things was that the centre of the bed seemed to behave differently from the edges. The middle was slightly over-squished while the outer lines were too high, something I would later discover is quite common on the Mini.

I also noticed that cold pulls weren’t behaving the way I expected. The filament came out too easily, which meant the nozzle was probably clean, but the offset and first layer squish were off. This reassured me that the nozzle itself didn’t need immediate replacement, even after about a week of runtime.

Cleaning the Smooth Steel Sheet

One of the first real breakthroughs came not from the printer, but from the print surface. IPA wipes alone were not enough. Oils from handling build up over time, and no amount of alcohol will cut through that residue. What worked was a proper wash in warm water with unscented washing-up liquid, followed by a rinse, dry, and then an IPA wipe to remove any lingering dust. Handling the sheet only by the edges made an immediate difference in consistency. Once reinstalled, adhesion was already noticeably improved.

Live Z Adjustments

The real turning point came with a bold move on the Z offset. At first, my offset was too high, leaving gaps between extrusions. I lowered it by –0.200 mm in one go, and the difference was immediate. Instead of disconnected strings, the first layer started to look like a solid sheet.

From there, it was a matter of micro-adjustments. Tiny steps of –0.02 mm smoothed out the striping and evened out the squish. The goal was a matte surface with faint ridges that stuck firmly without looking scraped or glossy. This stage taught me to move in two phases: a big adjustment to fix the obvious problem, then smaller trims to perfect the result.

Temperatures and Speeds

For Sunlu Orange PLA, I experimented with temperatures and eventually found a reliable balance:

• Nozzle at 215 °C for the first layer, dropping to 210 °C for the rest
• Bed at 60 °C consistently, with the option to bump to 65 °C for large bases
• Cooling fan off for the first two to three layers, then 100% afterwards

On the speed side, I noticed that PrusaSlicer’s default first layer solid infill speed of 40 mm/s was too aggressive compared to my 20 mm/s perimeter speed. The difference created inconsistencies across large bases. Dropping the solid infill speed to 20 mm/s to match the perimeters gave me a noticeably more uniform first layer.

Stress-Testing with a Large Square

To really prove the calibration, I printed a single-layer 180×180 mm square at 0.2 mm height with no cooling. This covered almost the entire Mini’s bed and revealed exactly how even my first layer was. The centre initially showed signs of over-squish, leaving a shiny patch, but a +0.02 mm adjustment eased that without sacrificing adhesion at the edges. Watching this large sheet print was the best confirmation that the changes were working. It stuck perfectly during the job and released cleanly once the bed cooled.

Cooling turned out to be critical. If I tried to remove the part while the bed was still warm, the PLA tore apart. Letting it return to room temperature made removal easy with a simple flex of the sheet. This lesson alone saved me from damaging more test prints.

Cold Pull Revisited

I came back to the cold pull technique as a way to double-check the nozzle condition. On the Prusa Mini, if the filament comes out without resistance, it means there is no major clog or residue. If it carries burnt particles or feels rough, it is time for cleaning or replacement. After seven days of runtime, my nozzle still looked fine. This reinforced that the main issue had been calibration and not hardware failure.

Creating a Cheat Sheet

After all the trial and error, I consolidated everything into a one-page cheat sheet. It includes nozzle and bed temps, speed recommendations, cooling settings, Z offset notes for each sheet type, and reminders about bed prep and print removal. This reference now lives next to the printer and prevents me from repeating mistakes. Instead of recalibrating blindly, I can pick up exactly where I left off.

Key Lessons Learned

• Bed preparation is as important as calibration. Soap and hot water beat IPA alone.
• Large Z moves solve big problems, but micro-adjustments solve the details.
• First layer speeds should match across perimeters and solid infill.
• Cooling strategy matters as much as temperature.
• Write down your offsets and settings for each sheet and material.

With these lessons in hand, my Prusa Mini is now far more reliable. The first layer goes down smoothly, sticks when it should, and releases without a fight once cool. For the first time, I feel confident walking away from a print without needing to hover nervously over the bed.

Until next time,
Joe