Page 552 - 04. Subyek Engineering Materials - Manufacturing, Engineering and Technology SI 6th Edition - Serope Kalpakjian, Stephen Schmid (2009)

32 Chapter 20 Rapid-Prototyping Processes and Operations

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FIGURE 20.4 (a) Schematic illustration of the fused-deposition-modeling process. (b) The
FDM 900mc, a fused-deposition-modeling machine. Source: Courtesy of Stratasys, Inc.

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FIGURE 20.5 (a) A part with a protruding section that requires support material.
(b)-(e) Common support structures used in rapid-prototyping machines. Source: After P.F.
Jacobs, Rapid Prototyping ca” Manufacturing: Fundamentals of Stereolithography. Society of
Manufacturing Engineers, 1992.

Although some FDM machines can be obtained for around $20,000, others can
cost as much as $300,000. The main differences between them are the maximum size
of the parts that can be produced and the numbers and types of materials that can
be used.
20.3.2 Stereolithography
A common rapid-prototyping process-one that actually was developed prior to
fused-deposition modeling-is stereolit/aography (STL). This process (Fig. 20.6) is
based on the principle of curing (hardening) a liquid photopolymer into a specific
shape. A vat containing a mechanism whereby a platform can be lowered and raised
is filled with a photocurable liquid-acrylate polymer. The liquid is a mixture of
acrylic monomers, oligomers (polymer intermediates), and a photoinitiator (a com-
pound that undergoes a reaction upon absorbing light).