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Rapid tooling & prototyping get even speedier.

Faster and more accurate hardware and stronger materials were the main new developments for rapid prototyping at this year's AutoFact Show in Detroit. Especially noteworthy were several advances in rapid tooling, including direct-tooling methods for stereolithography and a tooling-ready material for laminated-object manufacturing.

DIRECT TOOLING VIA SLA

3D Systems of Valencia, Calif., reported new applications for its Direct AIM system, in which stereolithography is used to make the mold core-and-cavity set itself. To turn the SLA patterns into a short-run injection mold, 3D Systems adds a tin-bismuth backing material, copper cooling lines, and a simple ejection system - all of which goes into a mold base. The whole process, from art to tool, takes as little as 3 hr, says v.p. Mark Bell. According to Bell, customers have injected a variety of resins in Direct AIM cavities, including ABS, PP, PC, nylon, and even some glass-filled materials. On a prototype ribbed.cellular-phone part made by Motorola, the SLA cavity withstood injection pressures as high as 4400 psi and temperatures as high as 450 F. The tool yielded more than 70 ABS parts. Some applications reportedly have obtained a few hundred shots from these Direct AIM tools, although a mold for glass-filled nylon started to fall apart after eight shots. "Direct AIM can have a tremendous impact in the five- to 500-shot range," notes Bell.

For higher production, molders are looking to other rapid-tooling methods, such as 3D's Keltool process, which produces cores and cavities from powdered metal. For example, ProtoCam of Allentown, Pa., employed Direct AIM to make an initial run of 20 medical parts in an FDA-approved PP. Later on, when the design had been accepted, ProtoCam used the Keltool process to make a mold that turned out 5000 pieces.

At AutoFact, 3D Systems and AlliedSignal Inc., Morristown, N.J., announced that the two companies have been working on applying AIM to powder injection molded ceramics and metals.

NEW PROTOTYPING MATERIALS

A new composite build material has been developed for laminated-object manufacturing (LOM), a rapid-prototyping system from Helisys Corp., Torrance, Calif. The new "LOM-Composite" material consists of a base layer of randomly oriented glass fibers mixed with a ceramic material and secured with a thermoplastic binder. The underside layer is of thermoset epoxy. The resulting material is said to be 6-9% stronger than the existing paper build material called "LOMPaper." The composite also shows z-axis growth of less than 0.4% under 90% relative humidity, according to Helisys.

When run on the company's LOM 2030H machine - which builds parts by laminating successive layers of sheet material - the binder and epoxy diffuse into each other, creating a permanent bond. Beta-testing applications for the new material included direct injection and blow molding tooling.

Stratasys Inc., Eden Prairie, Minn., released a new elastomer material for its fused-deposition modeling (FDM) machines. Called E20, this thermoplastic polyester has a flex modulus of 20,000 psi.

NEW FOR STEREOLITHOGRAPHY

Aaroflex Corp. of Fairfax, Va., recently emerged as a second source for stereolithography equipment besides 3D Systems. The company's new "Solid Imager" creates models from layers of selectively cured photosensitive resins, using either gas or solid-state lasers. President Albert Young claims a speed advantage for the new system because it scans the laser at up to 1250 in./sec and can selectively scan just the part slice rather than the entire vat.

Young cites an average accuracy of 0.0005 in./in. over 10 in. Layer thicknesses range from 0.002 to 0.20 in. Solid Imager's standard build envelope is a 25-in. cube, though larger units are available on a custom basis. Aaroflex recommends a DuPont build material, though Young adds that the system is compatible with any commercial sterolithography resin.

3D Systems also showed off its new-generation stereolithography machine, the SLA-5000. Chief among the machine's new features is a high-powered laser that enables a 20% throughput improvement and 50% improvement in fine-part detail. Minimum layer thickness has been halved to 0.002 in.
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Title Annotation:1997 AutoFact Show
Author:Ogando, Joseph
Publication:Plastics Technology
Date:Jan 1, 1998
Words:659
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