How does 3D printing build objects layer by layer?

3D printing, also called additive manufacturing, starts with a computer model sliced into many horizontal layers. The printer deposits or solidifies material layer by layer using methods such as fused deposition modelling, resin curing, or powder sintering. Because it adds material only where needed, it can produce complex shapes that are difficult to make with traditional manufacturing. The first major commercial 3D printing processes were developed in the 1980s, including stereolithography patented by Chuck Hull in 1986. Today the technology is used for prototypes, medical implants, aerospace parts, and even food.