# How Machines Build 3D Objects Layer by Layer from Melting Plastic > This patent describes a method and machine for creating three-dimensional objects by precisely depositing melted material, layer by layer, from a movable nozzle onto a base. - **Patent:** US 5121329 - **Original title:** Apparatus and method for creating three-dimensional objects - **Owner:** Stratasys Inc - **Granted:** 1992 - **Status:** Public domain (expired) - **Times cited:** 793 - **Field:** manufacturing, mechanical, software, consumer_electronics, materials ## What it does This patent describes an apparatus that builds a three-dimensional object by sequentially depositing multiple layers of solidifying material. It uses a movable head with a dispensing outlet, or nozzle, that releases material in a fluid state, such as melted plastic (Claim 1). This material then solidifies at a specific temperature. A mechanical system moves the dispensing head and a base member relative to each other along X, Y, and Z axes (Claim 1). This movement allows the machine to precisely place each layer, building up the object slice by slice. For example, a computer-aided design (CAD) program can create a 3D model, which is then converted into instructions for the machine to deposit material for each layer (Claim 11). ## What it does NOT cover - Does not cover 3D printing methods that do not involve depositing material from a dispensing head, such as laser sintering of powder or stereolithography using light to cure liquid resin. - Does not cover processes where the material does not solidify after being discharged from the nozzle, as Claim 1 specifies a 'supply of material which solidifies at a predetermined temperature'. - Does not cover methods that build objects without forming 'multiple layers' sequentially, as described in Claim 1. - Does not cover systems where the dispensing head and base member do not move relative to each other in three dimensions along 'X,' 'Y,' and 'Z' axes. - Does not cover 3D printing techniques that do not meter the discharge of material from an orifice at a predetermined rate, as required by Claim 1. ## The clever bit The core innovation was precisely controlling the deposition of a material that changes state (from fluid to solid) in successive, thin layers. By moving a dispensing head and base member in three dimensions, and carefully metering the material, complex shapes could be built up automatically, layer by layer, with controlled thickness. ## Real-world examples 1. Stratasys FDM 3D printers 2. Ultimaker desktop 3D printers 3. Prusa Research 3D printers 4. Creality Ender series 3D printers 5. Most consumer-grade 3D printers that use plastic filament ## Why it matters This patent is foundational to Fused Deposition Modeling (FDM), one of the most widely used 3D printing technologies today. It laid the groundwork for how many modern 3D printers operate, enabling the creation of physical prototypes and functional parts directly from digital designs. The company Stratasys, founded by the inventor, commercialized this technology, making 3D printing accessible for various industrial and, eventually, consumer applications. ## Frequently asked questions ### What does How Machines Build 3D Objects Layer by Layer from Melting Plastic cover? This patent describes a method and machine for creating three-dimensional objects by precisely depositing melted material, layer by layer, from a movable nozzle onto a base. ### Who owns patent US 5121329? Stratasys Inc owns this patent, granted in 1992. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 5121329 cited by? This patent has been cited by 793 later patents that build on its ideas. ### What problem does this patent solve? This patent is foundational to Fused Deposition Modeling (FDM), one of the most widely used 3D printing technologies today. It laid the groundwork for how many modern 3D printers operate, enabling the creation of physical prototypes and functional parts directly from digital designs. The company Stratasys, founded by the inventor, commercialized this technology, making 3D printing accessible for various industrial and, eventually, consumer applications. ### What does this patent NOT cover? Does not cover 3D printing methods that do not involve depositing material from a dispensing head, such as laser sintering of powder or stereolithography using light to cure liquid resin. **Full plain-English explainer:** https://patentbrief.org/patent/us/5121329/fdm-3d-printing-stratasys **Original patent:** https://patents.google.com/patent/US5121329 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How 3D Printers Build Objects Layer by Layer from Liquid](https://patentbrief.org/patent/us/4575330/stereolithography-3d-printing) — 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. - [How a 3D Printer Makes Flexible Medical Devices with Two Liquids](https://patentbrief.org/patent/us/12415312/additive-manufacturing-system-method-and-corresponding-components-for-making-ela) — This patent describes a specialized 3D printing system that precisely mixes and deposits two liquid silicone parts to create flexible, solid medical devices like prosthetics, using a rotating and translating base and a special nozzle that prevents drips. - [3D Printing Conductive Plastics Without Melting Them](https://patentbrief.org/patent/us/12233592/solid-state-additive-manufacturing-methods-for-compounding-conductive-polymer-co) — This patent describes a method for 3D printing objects and coatings from conductive plastics by mixing polymer and conductive fillers in a solid-state process, rather than melting them, to create parts that can conduct electricity or heat. - [How to Precisely Control Solid-State 3D Printing for Stronger Materials](https://patentbrief.org/patent/us/20240109245/process-control-systems-and-methods-using-a-solid-state-additive-manufacturing-s) — This patent describes a system for precisely controlling solid-state additive manufacturing, allowing real-time adjustments to create specific material structures without melting, using continuous material feeds. - [How to 3D Print Metal Parts with Easy-to-Remove Supports](https://patentbrief.org/patent/us/12358049/interface-layers-for-removable-supports) — This patent describes a method for 3D printing complex metal objects with support structures that can be easily removed after the final part is made solid, by using a special non-stick layer in between.