You can freely build on How 3D Printers Build Objects Layer by Layer from Liquid

What this patent 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 is now free to use

All 1 claims of US 4575330 are in the public domain. Specifically:

The 1 dependent claim add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• 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.

Who is building on this today

Companies like 3D Systems (founded by Hull), Formlabs, Carbon, and Stratasys continue to develop and sell advanced stereolithography and resin-based 3D printing systems. These companies are constantly innovating on the materials, speed, and precision of this foundational technology.

Products built on expired version of this technology

How to cite this patent in your documentation

UVP Inc. US Patent 4575330. Apparatus for production of three-dimensional objects by stereolithography. Granted 1986, expired 2004. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.