Over the last few years, the concept of DDM or rapid manufacturing has gained popularity among users of additive fabrication machines, and more companies are getting interested. The technique, which makes plastic components on demand, offers production engineers several benefits, including no machine or tooling costs, reduced inventory, and design flexibility during production.

During DDM, molten plastic is extruded in layers as fine as 0.005 in. When an overhang exists, a disposable support material is deposited. When the part is complete, the material may be dissolved in a water-based solution. No further processing is necessary. No tooling is needed because each part is built up layer by layer, as opposed to machining a part or a tool, which starts with a billet of material that gets milled away to create the part or the mold.

Joe Hiemenz, technical communications manager for Stratasys (www.stratasys.com), a Minneapolis, MN, U.S.–based supplier of DDM equipment, says that while DDM is often used in low-volume, complex manufacturing processes, all OEMs should consider it. “No company should overlook the elimination of tooling because this means three things: the elimination of the high costs of tooling, the elimination of tooling rework, and the reduction of wait time from many weeks to just a day or two,” he says.

He also says that mass production manufacturers should take a look at one of the largest growing DDM applications—fabrication and assembly tools such as jigs and fixtures. “All manufacturers need these assembly tools, and they are, by definition, low volume,” Hiemenz says.

Vacuum manufacturer Oreck, for example, uses DDM to produce custom work pallets. As a work-holding device, the production floor pallets secure the top cover of the vacuum in a precise position so that the vacuum can be assembled quickly and easily. After placing the motor, fan housing, and other support components into the stationary top cover, the bottom cover is attached.

In the past, Oreck’s custom pallets were constructed via traditional means, such as silicone or epoxy molds and urethane castings with inserts. “Using direct digital manufacturing reduces fixture production costs by up to 65% because we produce the fixtures in-house,” says Bill Fish, Oreck senior model maker. “With some projects costing over $100,000, the savings can be substantial.”

The aesthetics of DDM, however, are not equal to injection molding, so the process is usually reserved for internal parts. The machine can also be used for prototyping. “Appliance manufacturers, even of white goods, have multiple plastic components. Any plastic component is a candidate for either rapid prototyping or direct digital manufacturing,” Hiemenz says. “DDM won’t work for every application, but it is worth checking out.”