How 3D Printers Build Objects Layer by Layer from Liquid

This patent describes the foundational method for 3D printing, where a machine builds a three-dimensional object layer by layer by hardening a liquid material with light or other energy.

What it covers

The patent describes a system (Claim 1) that creates 3D objects by forming thin layers, called "laminae," from a special fluid that hardens when exposed to specific energy. The system uses "reaction means" (Claim 2) like a beam of ultraviolet light (Claim 9) to draw each cross-section of the object on the liquid's surface. As each layer solidifies, an "object support means" (Claim 2) moves the partially built object away, allowing the next layer to form and attach. For example, a laser draws the bottom layer of a small plastic toy boat on a liquid resin, then the boat dips slightly, and the laser draws the next layer, building the boat up from the liquid.

What it doesn't cover

• —3D printing methods that use powdered materials, like selective laser sintering (SLS), instead of a fluid medium.
• —3D printing methods that extrude melted plastic filaments, like Fused Deposition Modeling (FDM).
• —Systems that build objects by adding material from the side or top, rather than "extracting" them from a designated surface of a fluid.
• —Methods that don't rely on a "synergistic stimulation" (e.g., light, electron beam, chemical jet) to change the material's state.

The clever bit

The core innovation was the precise, automated, layer-by-layer construction of complex 3D objects from a liquid bath, using a controlled energy source to solidify specific cross-sections. This allowed for the creation of intricate shapes that were otherwise impossible to mold or machine.

Why it matters

This patent, by Charles Hull, is widely considered the foundational patent for stereolithography (SLA), the first commercially viable 3D printing technology. It laid the groundwork for an entire industry, enabling the rapid prototyping of parts and the creation of complex geometries previously impossible to manufacture.

Real-world examples

• 1.Stereolithography (SLA) 3D printers
• 2.Digital Light Processing (DLP) 3D printers
• 3.Formlabs Form series printers
• 4.Carbon 3D printers