Thursday, April 4, 2013

It Started with Stereolithography

Stereolithography diagram from Wikimedia Commons
Stereolithography diagram from Wikimedia Commons
As I have mentioned in previous posts, 3D printing is one of the fastest growing technologies and is poised to transform manufacturing over the next decade. This is the first of several posts I have planned to describe how specific 3D technologies work.

The first 3D printer was developed by Charles Hull in Valencia, California in the 1980s.  He first used the term stereolithography in his patent entitled “Apparatus for Production of Three-Dimensional Objects by Stereolithography” issued on March 11, 1986. Hull later relocated to Rock Hill, South Carolina and formed the company 3D Systems to manufacture the 3D printers.

Stereolithography works by sweeping an ultraviolet laser beam across a vat filled with a liquid photopolymer resin. Where the laser beam hits the resin, it solidifies to form one layer of a solid part. The part is lowered by a distance of .05mm to .15mm and a resin filled blade sweeps across the part to coat it with a fresh layer of liquid resin. This layer is also solidified by the ultraviolet laser and the process is repeated, layer by layer, until the full 3D part is completed. After printing, the parts are submerged in a chemical bath to remove any excess resin and cured in an ultraviolet oven.

The .stl file format, which is often used to store 3D dimensional data, was also developed by Hull to enable the transfer of the shape data into the stereolithography machines. 

Stereolithography was originally intended to accelerate the engineering process by allowing the creation of rapid prototypes and is still used primarily for that purpose. The process is also used to make molds for investment casting. The machines are typically large, expensive and produce parts with extremely high resolution and accuracy.

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