Original Date: 07/25/2005
Revision Date: 09/12/2006

(equipment: 3D-Systems SLA Systems)
Rapid prototyping involves the conversion of Computer-Aided Design models directly into an accurate and scalable physical part. Rapid prototyping has proven to be very useful in product development and production planning to shorten life cycle phases and validate the design at the earliest possible time. Northrop Grumman Electronic Systems uses this capability to support product development and production planning and has also been successful in the use of rapid prototyping in the design and manufacture of both hard tooling for metal forming and punching and in the development of new resins with improved thermal and dimensional characteristics.

The process of rapid prototyping uses a dimensionally accurate, solid model to produce a representative physical part in less time than traditional modeling and prototyping approaches require. Stereo lithography is a rapid prototyping methodology that uses a photosensitive resin that transforms from a liquid to a solid state when exposed to ultraviolet light. Northrop Grumman Electronic Systems (NGES) has rapid prototyping capability based on three stereo lithography systems manufactured by 3D Systems. The machines use ultraviolet lasers to expose the photosensitive resin and build physical parts.

NGES uses its rapid prototyping capability to produce design models used for engineering review, producibility review, part fit and tooling verification, wind tunnel and water tank evaluation, and investment casting molds. These applications are typical within many industries because models can be produced for one-tenth the cost of traditional modeling approaches. NGES has extended its expertise and use of rapid prototyping beyond traditional applications in three noteworthy areas: development of improved resins, optimization of process cycle time, and use of stereo lithography as an alternative to building hard tooling for use in metal forming and punching operations.

NGES has worked closely with its resin manufacturer to develop a new resin with improved thermal characteristics. Prior to the development of this resin, both leading and trailing edges of wind tunnel models would melt during testing. The increased melting point of the new resin prevents this model degradation. NGES is currently working with the resin manufacturer to develop a new resin with improved processing characteristics that will allow for a reduction in dimensional tolerance errors. Improved performance is projected to provide a 1-mil tolerance versus the normal 5-mil error limit.

Processing time is a major impact on the cost of prototyping so that any efficiency gained in processing of a model provides a direct reduction in cost. NGES has developed the experience and expertise to understand the critical aspects of solids modeling that impact model build time. By working with customers of the Prototype Shop, NGES has been successful in reducing average model build time and in reducing the cost associated with this process.

An application of rapid prototyping unique to NGES is the design and manufacture of hard tooling for metal forming and punching operations. The Rapid Prototyping Shop has developed a metal-filled epoxy resin that can be backfilled into a honeycombed model to produce a solid, robust tool. Such tools have been produced and used in NGES production processes with hundreds and even thousands of failure-free machine cycles.

While rapid prototyping is a mature and widespread practice, NGES has been successful in defining critical limitations in materials, processing characteristics, and applications of the technology. By overcoming these limitations, NGES has enhanced and extended the capability and value of this process.

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