Why Your First Layer Won't Stick

Almost every failed print fails in the first two minutes. The nozzle lays down a line, the line curls up behind it, and forty minutes later you come back to a plate covered in what the internet affectionately calls spaghetti. The good news: first layer problems have a short list of causes, and you can work through all of them in about five minutes. The trick is knowing what to look at first. Start by learning what a good first layer looks like Before you change any settings, print something and look at it. This one skill will save you more time than any setting in your slicer. A good first layer has three properties: The lines touch each other. No gaps between them. The surface should look solid, like a sheet, not like a row of parallel worms. The lines are slightly flattened. A round line means the nozzle was too far from the plate. You want the plastic squashed a little, so it has somewhere to grab. You can't easily lift a corner with your fingernail. If a corner pops up while the print is still running, it will keep going. If your first layer looks like separate round strands with gaps between them, your nozzle is too high. That's the single most common cause, and it's the first thing to check. If the layer looks scratched, translucent, or has ridges where the plastic was pushed sideways, your nozzle is too low. This causes its own problems — it can clog the nozzle and leave a flared "elephant's foot" at the base of your model. The five-minute checklist Work through these in order. Stop when the problem goes away. 1. Check your Z-offset This is the distance between the nozzle tip and the plate on the first layer, and it's wrong more often than anything else. The classic method: heat the bed to printing temperature, put a sheet of ordinary printer paper (about 0.1 mm thick) under the nozzle, and adjust until you feel slight drag when you pull the paper. Not free-sliding, not stuck — a light scrape. Most modern printers let you adjust the Z-offset live, while the first layer is printing. This is by far the easiest way to do it. Start a print, watch the lines, and nudge the offset down in steps of 0.01–0.02 mm until the lines stop being round and start touching each other. Do this with the bed hot. Metal expands, and a plate levelled cold will not be level at 60 °C. 2. Clean the plate Fingerprints are grease, and nothing sticks to grease. If you've picked the plate up with bare hands — and everyone does — that's very likely your problem. Wash it in the sink with warm water and ordinary dish soap, then dry it with a clean cloth or paper towel. This works better than isopropyl alcohol, which spreads thin films of oil around as much as it removes them. Use alcohol for a quick touch-up between prints, and soap and water properly every week or two. After cleaning, handle the plate by the edges. One warning: if you have a textured PEI plate, don't scrub it with anything abrasive. The texture is the adhesion. 3. Check your bed temperature Cold plastic doesn't stick. Rough starting points: Material Bed temperature PLA 55–65 °C PETG 70–85 °C ABS / ASA 100–110 °C TPU 40–60 °C If you're at the low end and struggling, add 5–10 °C. Many slicer profiles also run the first layer a few degrees hotter than the rest of the print, which is worth doing. Bear in mind that the number on your screen is what the sensor reads, usually near the heater, not necessarily what the surface is doing. A cheap infrared thermometer or a bed thermistor test will tell you if your plate reads 60 and delivers 48. 4. Slow down the first layer The first layer is the one layer with nothing underneath it to hold the plastic in place. Print it slowly — around 20–25 mm/s — even if the rest of the print runs at 60 or 200. Fast first layers drag plastic instead of laying it down. If your prints stick fine on small parts but fail on big ones, speed is a likely suspect. 5. Turn the part cooling fan off for layer one Cooling is what gives you crisp overhangs later in a print. On the first layer it does nothing but cool the plastic before it can bond to the plate. Almost every slicer has a setting for this. Fan off for layer 1, then ramp up from layer 2 or 3. For ABS and ASA, keep the fan off or very low for the whole print. 6. Use a sensible first layer height With a standard 0.4 mm nozzle, a first layer of 0.2 mm is forgiving and reliable. Going down to 0.12 mm gives you a slightly nicer bottom surface and a much less reliable print, because it leaves no margin for a plate that isn't perfectly flat. If you're fighting adhesion, set the first layer to 0.2 mm or even 0.25 mm and stop worrying about it. When the settings are fine and it still won't stick Small footprints A model that touches the plate on four tiny points has almost nothing to grab with. Add a brim — a flat skirt of material attached to the base of the model, usually 5–8 mm wide. It peels off afterwards with a fingernail or a deburring tool. A brim solves more adhesion problems than any other single setting, and costs almost no material or time. Warping If a print sticks fine at first and then lifts at the corners partway through, that's not adhesion — that's warping. The plastic is shrinking as it cools and pulling itself off the plate. Warping is mostly about temperature stability. Move the printer away from open windows, doors and air conditioning. A draught across a print is enough to lift a corner. ABS and ASA warp badly enough that they realistically need an enclosure; PLA rarely warps at all; PETG sits in between. The wrong surface for the material Different plates suit different materials: Textured PEI is the most forgiving all-rounder, and leaves a pleasant matte finish on the bottom. Smooth PEI gives a glossy bottom and grips PLA extremely well — sometimes too well. Glass needs help: a thin layer of glue stick, or hairspray. That "too well" is a real issue. PETG bonds to smooth PEI and glass so strongly that it can rip chunks out of the plate when you remove the part. The standard fix is counterintuitive: put a thin layer of ordinary glue stick down first, as a release agent. It stops PETG bonding directly to the surface. A worn plate PEI sheets don't last forever. If the middle of your plate — where you print everything — has stopped gripping while the edges still work, the coating is worn. Most plates are double-sided, so flip it over and carry on. Wet filament won't fix itself If you're getting popping and hissing noises from the nozzle, visible steam, or a rough, bubbly surface, your filament has absorbed moisture from the air. Wet filament makes weak, ugly first layers regardless of how well levelled your plate is. PLA is fairly tolerant. PETG and TPU absorb water quickly — a spool left open on a shelf for a month in a humid climate is measurably worse than a fresh one. You can dry filament in a dedicated dryer, or in an oven at low temperature if you can trust it to hold 45–55 °C without spiking. Don't put PLA above about 50 °C — it will soften and fuse on the spool. Store spools with silica gel in a sealed box, and the problem mostly disappears. A short summary If your first layer isn't sticking, in order: Look at the lines — round and separated means the nozzle is too high Adjust the Z-offset live while printing, with the bed hot Wash the plate with soap and water Raise the bed temperature 5–10 °C Slow the first layer to 20–25 mm/s Turn the fan off for layer one Add a brim Nine times out of ten, it's the first three. Get in the habit of watching the first layer go down instead of walking away, and you'll catch failures in thirty seconds instead of forty minutes.