143rapid Prototyping Development

There are three major rapid prototyping approaches that have influenced the development of laser-based rapid manufacturing in metals. These are stereolitho-graphy [5, 6], laminate object manufacturing [7], and selective laser sintering [8]. Each of these technologies use sophisticated computer codes to convert solid models into two-dimensional "slices" along a particular stacking axis. In the case of stereolithography, a photosensitive polymer is extruded through a nozzle and cured using an ultraviolet laser. In laminated object manufacturing, thin plastic sheets are laser cut and then stacked to form a three-dimensional structure. Selective laser sintering uses polymer powder as a feedstock and a laser to fuse them together. The resulting objects made from these three processes are prototypes used for the purposes of evaluating form and fit. Shapes made from these processes are not structural. Recently, work done on improving the strength and temperature capability of the resins and polymer feedstocks has resulted in pseudostructural parts (i.e., parts that have structural integrity over a very limited life span). The key element of these rapid prototyping processes are the computer codes used to control machine movement, and it is this technology that can be transitioned to rapid manufacturing of metal components. Of the three technologies mentioned above the selective laser sintering (SLS) process has been successively modified to be used with metal powders, as described later.

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