In continuing this series on manufacturing, my thoughts turn to a time nearly 25 years ago while I was editing a magazine for the foundry industry. That was when I first heard the word “stereolithography,” a term attributed to Charles W. Hull. He patented a method and equipment for producing solid objects by “printing” them in successive thin layers – one atop the next – that eventually formed a specified shape.
Hull’s original patent described a process and invention by which a reservoir of curable ultraviolet photosensitive polymer and an ultraviolet laser light beam could be used to deposit layers of liquid polymer on a platen. The light beam would then be moved to trace the cross-sectional pattern of a part upon the photosensitive polymer, thereby hardening it. A new layer of liquid polymer would then be applied to one below it, and the ultraviolet laser would again trace the part’s cross section. This would happen repeatedly, eventually building a part of a defined shape according to the tracings of the laser for each polymer layer. This oversimplification aside, Hull’s patent formed the basis of the first company to commercialize the capabilities of this process. That company, 3D Systems, still operates from its headquarters in South Carolina.