More recently, the development of modern techniques was influenced by the work of two men, Otto John Munz and Wyn Kelly Swainson. Otto John Munz was born in Czechoslovakia, moved to Canada in the late 1930s and later settled in Alexandria, Virginia in the 1940s. He was an inventor and patent lawyer. He patented a system called Photo-Glyph Recording, which consisted of creating multiple layers of a photo emulsion to replicate a 3D structure that came from a scanned object. Using a piston in a cylinder, the photo emulsions were added to create a 3D object. Subsequently, this object could be manually or photochemically carved to create the final 3D object [6].

The other pioneer was Wyn Kelly Swainson from California. In 1968, he proposed the “Method, Medium and Apparatus for Producing Three Dimensional Figure Product”. This method consisted of creating a 3D figure in a volume of medium which includes an intimate mixture of at least two components selectively sensitive to dissimilar parameters of electromagnetic radiation. The medium was then exposed to two beams of radiation guided in response to an image description and having dissimilar electromagnetic parameters matched to the medium. In this manner, the path of the first beam with a specific parameter of activation resulted in the first component being formed. The path of a second beam with a second parameter of activation resulted in another part of the object being completed [7].

As was mentioned at the beginning of the chapter, Hideo Kodama and Charles Hull are considered the fathers of “modern” rapid prototyping. In 1981, while working in the Nagoya municipal industrial research institute in Japan, Professor Kodama published a paper on a photopolymer rapid prototyping system entitled “Automatic Method for Fabricating Cubic Shapes,” as a 3D information display method. In his method, Kodama described a way to fabricate solid models by building layers using a 3D plastic model with photo-hardening polymer [1]. A 2 story house piling up 27 layers of 2 mm thick layers of resin was built using this method and is likely the first ever 3D printed object in history (Fig. 1.3). Professor Kodama presented his work in national and international meetings. However, he was unsuccessful to get the attention of the scientific community causing him to abandon the project. He started to file a patent but never completed the application. His work therefore remained unrecognized for several years, until 1995, when he was awarded the Rank Prize, a privately funded British award for outstanding inventors. He shared the prize with Charles Hull.

Charles Hull was born 1939 in Clifton, Colorado. He received a Bachelor of Science degree in engineering physics in 1961 from the University of Colorado. In 1984, he invented a system for generating a 3D object using successive, adjacent, cross-sectional laminae of the object. A fluid medium capable of altering its physical state in response to appropriate synergistic stimulation was used to create the layers. Each successive lamina was automatically integrated onto the previous ones to recreate the desired 3D object. He called this method stereolithography apparatus (SLA) [2]. He filed and obtained a patent in 1987 for this innovative method, similar to the one described by Kodama. Hull founded a company called 3D systems in Valencia California and sold the first SLA in 1988. The company continued to grow, and Hull remains the chief technology officer. He has been recognized internationally as great inventor and was included in the hall of fame for inventors in 2014. Figure 1.4 shows the first SLA and the first object printed using the machine, a cup that took months to finish. (Photo courtesy of 3D system, Inc.).