TEXT 22. Rapid manufacturing

With increased competition from the global economy, manufacturers face the challenge of delivering new customized products more quickly than before to meet customer demands. A delayed development or delivery can mean business failure. Several technologies collectively known as Rapid Manufacturing (RM) have been developed to shorten the design and production cycle, and promise to revolutionize many traditional manufacturing procedures.

Before production of a product begins, a sample or prototype is often required as part of the design cycle, to allow demonstration, evaluation, or testing of the proposed product. The fast creation of a prototype is known as Rapid Prototyping (RP), and is generally carried out before specialized molds, tools, or jigs are designed. Prototyping traditionally required considerable skilled hand labor, time, and expense, typically applied to cutting, bending, shaping, and assembling a part from standard stock material. The procedure was often iterative, with a series of prototypes being built to test various options. For many applications, this process has been revolutionized by a relatively recent technology known as layer manufacturing or Solid Freeform Fabrication (SFF), in which a part of an arbitrary shape can be produced in a single process by adding successive layers of material. RM also includes the fast fabrication of the tools required for mass production, such as specially-shaped molds, dies, and jigs. Many different layer manufacturing processes have now been developed, using an increasing range of materials. The parts produced have been of steadily increasing size and durability, and as the quality has improved layer manufacturing is being used more and more frequently to fabricate the parts both for production tools and functional prototypes. The application of layer manufacturing to make the components used in production is termed Rapid Tooling (RT). It has been applied to injection molding, investment casting, and mold casting processes.

For some products, it can be economical to use layer manufacturing to produce the final products themselves, sometimes in a matter of days instead of weeks or months. Although the layer fabrication process itself is typically not as fast as traditional mass production techniques, it eliminates tooling, setup, and assembly processes, can produce parts of superior quality and complexity, and can be ideal for making custom parts based on a customer's special requirements. More manufacturers are taking advantages of these techniques.

Layer manufacturing allows parts of completely arbitrary 3-dimensional (3D) geometry to be fabricated, offering designers a new freedom to shape parts optimally without the constraints imposed by forming, machining, or joining. Another important advantage is that the process utilizes the computer description of the part shape directly, and allows integration of the Computer Aided Design (CAD) with the Computer Aided Manufacture (CAM) of the part. It therefore allows a manufacturing cycle with a seamless transition through the computer design, simulation, modeling, and fabrication procedures.

In addition, the profiles used by the fabrication process are straightforward for the designers and customers to understand, thus facilitating technical communications. The technologies now available include a variety of different processes, such as Stereolithography, Selective Laser Sintering, Shape Deposition Manufacturing, and Laminated Object Manufacturing. The cost saving potential of RM techniques may be illustrated by a research program studying the application of several layer manufacturing technologies to the production of tools for sheet metal forming. Sheet forming involves plastic deformation of sheet metal blanks by one or more operations into required shapes, usually by pressing the metal against a mold or die by fluid or elastic pressure. The tooling required is relatively expensive to produce by traditional machining, but layer manufacturing offered great savings. Numerous commercial RM systems for various materials and sizes are now available on the market around the world. RM technologies have seen rapid development and improvement in capability, and have been in widespread use for well over ten years. They have gained tremendous success by practical verification, and will no doubt see further development and application in the future.