How Does 3D Printing Work?

The pipeline, start to finish

Every print, on any machine, goes through the same five steps:

1. Model in CAD. A 3D model defines the geometry, usually made in CAD software (or downloaded, or generated by AI tools). This is the stage where wall thickness and tolerances get decided.
2. Export the file. Save the model as an STL (a mesh of triangles, the classic format) or 3MF (a modern format with more metadata) that slicer software can read.
3. Slice it. Load the file into a slicer (like Cura, PrusaSlicer, or OrcaSlicer), which divides the model into hundreds of horizontal layers and generates the G-code.
4. Print. The printer follows the G-code line by line, building the object one layer at a time, each fused to the one below. This can take minutes to days depending on size and settings.
5. Post-process. Remove supports, and sand, clean, or paint as needed.

What the slicer decides

The slicer is where a 3D shape becomes real movement, and it's where you make the key calls. Beyond cutting the model into layers, it lets you set orientation (how the part sits on the plate), support structures (scaffolding for overhangs), layer height (thinner means finer but slower), infill (how solid the inside is), and temperatures. Those choices decide how strong, how detailed, and how fast the print turns out, so always preview the sliced layers before you print.

How FDM builds a part

Fused deposition modeling (FDM), the common desktop type, feeds a plastic filament into a heated nozzle that melts it. The nozzle moves along the paths in the G-code, laying down one thin layer of molten plastic on the build plate. Then the build moves down (or the nozzle up) and the next layer is deposited on top, fusing as it cools. Repeat a few hundred times and the part is complete. Because each layer bonds to the last, FDM parts are slightly weaker across layers than along them, which affects how you orient a part.

How SLA and SLS build a part

The other two technologies build layers differently but follow the same pipeline:

• SLA (resin): a light source cures liquid photopolymer resin into solid plastic, one layer at a time, from a vat. Curing with light gives very fine detail and smooth surfaces.
• SLS (powder): a laser sinters (fuses) fine nylon powder into solid layers. The surrounding unfused powder supports the part as it builds, so no separate support structures are needed, which makes complex shapes easy.

Why the process matters to you

Understanding the pipeline is what lets you get good prints: the slicer settings control quality, orientation affects strength and supports, and the layer-by-layer nature explains why overhangs need support and why some surfaces look rougher than others. To put it into practice, see 3D printing for beginners, and for the overview, what is 3D printing.