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.

    Early on, stereolithography was an intriguing idea to an established manufacturing culture in which components – regardless of the process used to form them – were often produced or finished by removing material from a product “blank.” Stereolithography was the antithesis of that, and many were quick to recognize the economic potential of such a process. Unsurprisingly, additional techniques using raw build materials such as liquids, sheets and powders of plastics, ceramics and metals were soon developed. Each of these was a variation on the theme of building a part up layer by layer. The term “3-D printing” was also used to describe these processes.

    Early stereolithographic techniques were found to be too slow to be of much use for product production, but they were extremely fast when it came to forming a product prototype in record time. The term “rapid prototyping” came into use to describe the family of processes by which prototypical parts were produced in layers for evaluation and testing by product-design engineers.

    During the last two decades, great strides have been made in the software, hardware, techniques and raw materials that could be used to build parts. Additive manufacturing (AM) has become the broad term that covers these techniques. FORGE ran an article on this topic in our August 2012 issue (p. 19). In it, author Jon D. Tirpak of SCRA Applied R&D made the following statement: “Additive manufacturing is one of those technologies that impression die forges especially need to watch.”

    I couldn’t agree more with our frequent contributor. How this statement is interpreted by our industry is up to key executives in the forging community. But is AM something to “watch” or something for which to “watch out.” In my opinion, AM is more opportunity than threat to the forging community.

    Whatever you might think about this topic, Tirpak was clear in his article’s closing statements when he said, “AM is not something to be reckoned with in the future. It is here now.”


Dean M. Peters, Editor