Original Date: 04/01/1993
Revision Date: 01/19/2007

Technical specialists at McDonnell Douglas Aerospace (MDA) have investigated two similar rapid prototyping technologies for producing small, complex-shaped prototype parts such as nose cones. Stereo lithography (SLA) involves the use of a photo sensitive polymer bath from which plastic prototypes are created using a laser for the polymer curing. Another technology, referred to as selective laser sintering (SLS), uses a powdered wax that is sintered with a laser to create a replica of the part to be made via investment casting. Both rapid prototyping technologies can produce parts in a fraction of the traditional time. These technologies also have a reduced overall cost per prototype.

Prior to the advent of rapid prototyping technology, MDA was dependent on a model shop with experienced machinists to build prototypes. While the model shop is still used, MDA employs rapid prototyping technology for some parts. The cost drivers for this effort include the intensive labor required to manually produce prototypes. The prototypes built with the traditional process often required many man-hours.

There are numerous service bureaus that produce SLA prototypes from CAD drawings. Also, there are SLA systems in St. Louis at McDonnell Aircraft Company, and at the Douglas Aircraft facilities in Long Beach. MDA-West has worked with both McDonnell Douglas SLA systems as well as with service bureaus, and one service bureau that produces prototypes with SLS technology.

Several lessons emerged from using rapid prototyping technologies including the fact that this type of rapid prototyping can produce successful models. There is a factor of 10 cost differential between the use of outside service bureaus compared to MDA internal cost and schedule to produce a part by conventional methods. The facet size used in solid model design impacts surface finish of prototype, and the accuracy of the design database is critical in obtaining an acceptable prototype.

MDA-West has confidence in producing dimensionally, accurate and functional hardware at low cost and short lead time. SLA and SLS will continue to be used for future part prototyping.

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