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How does a 3D printer actually work?

Day 1, part 2 of learning 3D printing in 7 days: how an FDM printer turns filament into a part, from the extruder gear and hot nozzle to the cooling fan, the heated bed and why every layer needs something below it.

Tutorials Beginner 1:02 27 views Nov 03, 2026
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About this video

How a 3D printer works, in one minute

This is day 1, part 2 of PrintPal's learn 3D printing in 7 days series. After your first print, here's what the printer is actually doing. Most home printers are FDM (fused deposition modeling) printers: they melt plastic filament and draw your part one thin layer at a time.

The plastic: thermoplastic filament

Filament is a thermoplastic. It softens when heated and turns solid again when it cools, and you can repeat that over and over. Most filaments start to soften at around 50–70 °C, and they're printed much hotter than that so they flow through the nozzle.

From spool to part, step by step

  1. The extruder gear grips the filament and pushes it into the print head in very small, precise amounts.
  2. The hot nozzle melts it just enough to squeeze out as a thin line.
  3. The part-cooling fan on the side of the print head hardens each line almost instantly, so it keeps its shape.
  4. The heated bed keeps the first layer warm and sticky. Plastic shrinks as it cools, so a cold first layer would pull up and come loose. That's why the fan is usually off or low for the first layer.
  5. Layer by layer, each new layer sits on the one below it until the part is done.
Part What it does If it goes wrong
Extruder gear Pushes the exact amount of filament Gaps or blobs (flow problems)
Nozzle / hotend Melts the filament Clogs, stringing
Cooling fan Solidifies each line Droopy overhangs, curled edges
Heated bed Holds the first layer down Warping, prints coming loose

Why you can't print in mid-air

Every layer has to rest on something. A printer can't start a line in empty space, which is why steep overhangs and supports matter so much. Read how to fix 3D printed overhangs and how to stop supports sticking to your print. If prints won't stay down, see how to fix the first layer with one setting.

What's next

All of this is controlled from your slicer. Day 2 covers slicing, infill and PLA vs PETG.

FAQ

What does FDM mean?
Fused deposition modeling: melting plastic and laying it down in layers. Resin (SLA/MSLA) printers work differently, curing liquid resin with light.

Why is the bed heated?
So the first layer stays soft and sticky through the whole print instead of shrinking and peeling up.

Why is the cooling fan important?
It sets each line right after it's laid down, so overhangs, bridges and small details keep their shape.

Full Transcript

Day 1 of teaching you 3D printing in 7 days. After our first successful print, let's look into the basics of how the printer works. The material used for printing is thermoplastic, which softens when heated and solidifies when cooled down. Most materials start softening at 50 to 70 degrees Celsius. The filament goes through the printhead into the nozzle pushed by a gear by very small amounts straight into the nozzle. The nozzle heats up, makes it soft enough to be pushed through and laid under the printhead. And the plastic becomes solid straight away, thanks to the fan on the side of the printhead, besides the first layer. Because if it became solid, it wouldn't hold to the print bed. Because when it gets cold, it shrinks and would detach from the bed. That's why the print bed is always heated to keep the first layer soft and sticky through the whole print. Now it laid a single layer. That will support the one above it, meaning we can never start printing something in the air. This will be important in the next videos. And all of this can be controlled from the slicer, that we will go over in the next parts.