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How 3D Printing Works

A 3D printer builds objects by stacking thin layers of melted plastic. Think of a precise robot holding a hot glue gun, drawing one layer, moving up a fraction of a millimeter, and drawing the next — hundreds or thousands of times until the object stands complete.

The common home method is called FDM (fused deposition modeling). Almost everything in these guides assumes FDM.

The parts that matter

Filament is the raw material: a spool of plastic string, usually 1.75 mm thick. The printer pulls it in, melts it, and pushes it out. Different plastics behave differently — see Filament in Plain Language.

The extruder grips the filament and feeds it forward. Two styles: Bowden (the motor sits on the frame and pushes filament through a tube) and direct drive (the motor rides on the print head). Direct drive handles flexible filament better; Bowden is lighter and common on budget printers.

The hot end and nozzle melt the plastic (around 200°C for common plastics) and squeeze it out through a tiny hole — usually 0.4 mm wide. That hole size sets the detail level: smaller nozzle, finer detail, slower print.

The build plate is the surface the object sticks to while printing. It is usually heated (around 60°C for common plastics) to help the first layer grip. A clean, level plate is the difference between a print that works and a pile of spaghetti — see Your First Print.

Layers and orientation

Because objects are built bottom-up in layers, orientation matters. A part printed standing up is weaker between layers than the same part printed lying down — layers can separate under stress along the layer lines. When something needs strength, orient it so the stress runs along the layers, not across them.

Overhangs are parts of the model that stick out sideways with nothing underneath. Plastic can't print on air past about 45 degrees, so steep overhangs need temporary supports — thin scaffolding the slicer adds and you snap off afterward. Designing or orienting to avoid supports saves time and filament.

From file to object

  1. You get a model — a 3D file, usually .stl or .3mf, downloaded or designed yourself.
  2. A slicer program converts it into G-code: the literal move-by-move instructions for your printer (temperatures, speeds, paths). See Slicing Basics.
  3. The printer follows the G-code, layer by layer, until done.

That's the whole pipeline: model → slicer → printer → object. Every guide here is about making one of those steps go smoothly.

Sources