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© Dr. Des. Volker Ruhl
Excerpt of the thesis of Dr. Des. Volker Ruhl at Harvard University, Cambridge Massachusetts about
"Computer-Aided Design and Manufacturing of Complex Shaped Concrete Formwork"
The Additive Techniques - Rapid Prototyping
Solid Freeform Fabrication (SFF) is a class of manufacturing technologies aimed at the rapid fabrication of one-of-a-kind, structural strength components without part-specific tooling or process planning. SFF arose from the dream of „push-button“ prototyping, in which solid three-dimensional geometric models are created automatically under computer control. Originally merely used for creating models for visualization, many industrial users of SFF technologies are realizing the greater potential of SFF as a legitimate manufacturing process for producing patterns and in some cases, functional components.
The general class of described solid freeform fabrication systems, is the dominant prototyping technology at present, and has the potential to even become a key manufacturing technology in the future.
A Brief History
Based on the availability of representative 3D geometric computer models, experimental attempts at the “direct” generation of physical objects, without traditional (subtractive and formative) machining tools, were begun in the 1970s in Israel, in Japan by Kodama and the US by Formigraphics (1974) and Dynell Electronics (1976). Nagoya Ind. Research (1981) 3M Company (1982), Batelle Labs (1984), Fujiutsu (1986). followed in the early 1980’s1;
However, the intriguing idea of printing 3-dimensional objects on the basis of computer models - the technology of Rapid Prototyping and Manufacturing (RP&M) - became commercial reality when a Valencia, California -based company introduced an additive process called „StereoLithography (STL)“ in March 1986. The first STL apparatus, the SLA-1, was previewed at the US AutoFact Fair in Chicago, in November 1986. In 1988, 3D Systems exhibited the first industrially usable technical equipment under the description „StereoLithography Apparatus“. The company 3D Systems was found by Chuck Hull the inventor of the StereoLithography process (STL).
Other vendors followed with similar ideas in the late 1980s and the early 1990s, such as Cubital (Itzchak Pomerantz), W. Masters (Producer of Kayaks, 1987), Light Sculpting (1988), DuPont (1989), Stratasys (1990), Helisys and EOS GmbH (1991), DTM, Mitsui and Teijin Seiki (1992), Soligen (1993), Sanders (1994), BPM (1995), Ennex (1996).
By 1996, Rapid Prototyping was one of the most quickly developing manufacturing technologies in the world. In less than ten years, it has grown from a single system sold by one company, to a point where15 different generic types of additive autofabricators are sold commercially. Seven of these types are based in the United States, four in Japan, two in Germany and one each in Israel and France (see table ).
A total of 1499 systems were sold between 1988 and 1995, of which one third (526 systems) were sold in 1995.2 Among the industrialized countries the United States still dominates the field with 80 percent of the installed systems.3 The number of rapid prototyping service bureaus grew from 42 in 1992 to 230 in 1996.4 Research is being conducted in virtually every industrialized country and hundreds of academics and industrialists are actively involved in developing RP technology. This exponential rate of growth makes it virtually impossible to remain informed about research in the United States and the rest of the world.
The Name “Rapid Prototyping”
The name Rapid Prototyping originally stems from its first applications for fit, form and function testing. Because of the fact that the 3-D build-up of an object is achieved through successive layers, an early expression in the 1990s for Rapid Prototyping was “Layer Manufacturing Technology”. The different processes are also summarized in the terms „Solid Freeform Fabrication Processes (SFF),” „Material Incress Technology,“5 and “Toolless Manufacturing.” The two most frequently used are Rapid Prototyping (RP)6 and Solid Freeform Fabrication (SFF).