Types

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Since the late 1970’s several types of 3D printing have been invented. Originally the printers were large and expensive. They were also very limited in what they could print.

There are several methods of 3D printing now available. They differ in the material used to print & the way material is deposited to create an object. Some methods soften or melt materials to create the layers. These include Selective Laser Melting (SLM), Direct Metal Laser Sintering (DMLS), Selective Laser Sintering (SLS) & Fused Deposition Modeling. Other methods cure liquid materials using sophisticated technology. This is known as Stereolithography (SLA). Laminated Object Manufacturing (LOM) cuts thin layers to shape and joined together. Each technology has its own strengths and weaknesses. The things to consider when choosing a machine are going to be speed, cost of printer, cost of prototype or plans, cost & choice of printing materials and color capabilities.

Extrusion Deposition – Fused Deposition Modeling was developed in the late 1980’s and commercialized in 1990. It uses a plastic filament or metal wire that is wound on a coil and unreeled to supply material to an extrusion nozzle which turns on and off the flow. This nozzle heats up to melt the material and can move horizontally and vertically. The expiration of the patent associated to this technology cleared the way for a large open – source community use and development.

Granular Materials Binding – Another approach is to fuse materials in a granular bed. A laser is usually used to sinter the media into a solid. Examples are Selective Laser Sintering (SLS) and Direct Metal Laser Sintering (DMLS). (SLS) was developed & patented by Dr. Carl Deckard and Dr. Joseph Beaman at the University of Texas at Austin under the sponsorship of DARPA in the mid 80’s.

Selective Laser Melting (SLM) – completely melts a powder with a high energy laser. This method creates fully dense materials with similar properties to conventional manufacture metals.

Electron Beam Melting (EBM) – manufacturing for metal parts by melting metal powder layer by layer with an electron beam in a vacuum. Unlike Metal Sintering that operates below the melting point EBM parts are fully dense, void – free and very strong.

Photopolymerization – Used primarily in Stereolithography, produces a solid part from a liquid. This process is redefined from the previous effort of François Willème in 1860.

Digital Light Processing (DLP) exposes a vat of liquid polymer to a light from a DLP projector. Exposing the liquid causes it to harden then the process is repeated.

Multiphoton Photopolymerization – is a 3D microfabrication technique that creates ultra small features. It traces the desired object into a block of gel using a focused laser. the gel is only cured into a solid where the laser was focused and the remaining gel is washed away. Feature sizes of under 100 nm are as easy to create as complex structures with moving or interlocked parts.