Desktop plastics manufacturing leads news at AutoFact '89.

Desktop Plastics Manufacturing Leads News at AutoFact '89

A new entry in the growing field of "desktop manufacturing" headed the news for plastics processors at AutoFact '89, the Society of Manufacturing Engineers' Automated Factory exhibition held recently in Detroit. The show topped off a decade that brought engineering computing out of the mainframe and onto the factory floor. In recent years, though, AutoFact's emphasis has shifted from factorty automation to computer-aided design and manufacturing (CAD/CAM), and there were a few important software announcements in this area.

NEW IN DESKTOP

MANUFACTURING

DTM Corp., Austin, Tex. (formerly Nova Automation), introduced the SLS model 125 for desktop manufacturing of objects up to 12 in. diam. and 15 in. high. The DTM machine, the first such system in commercial use, uses selective laser sintering (SLS) to form objects layer by layer out of powdered plastics or other materials (see also PT, Feb. '89, p. 78). This differs from another desktop manufacturing process known as stereolithography, which forms objects in layers using a laser and a photopolymerizable liquid.

Depending on its sintering characteristics and the power of the laser, nearly any material that softens and has decreased viscosity upon heating theoretically can be used for SLS, including ABS, PVC, TP polyester, nylon, wax, polystyrene, epoxy, and even metals and ceramics with suitable binders. However, DTM says it will concentrate on engineering plastics and wax for investment castings. The company is co-operating with Cleveland-based BF Goodrich Co. on development of new materials for SLS.

Sintering occurs after a layer of fine powder heated close to its melting point is leveled in a container with a roller. Using previously created CAD solid-modeling data, a laser traces one cross-section of the desired object. As the laser strikes the powder particles, it raises their temperature momentarily to the point where they sinter and weld together without melting. The next layer of powder is then put down, leveled and sintered, and the process is repeated until the object is built.

SLS differs from powder metallurgy in that it does not require dies to press the powder into the part's shape before sintering. Since SLS does not require any part-specific tooling, it is therefore more cost-effective when only a few parts are to be made, according to the company.

Since the model is formed one cross-section at a time, undercuts and projections result in unconnected islands in certain cross-sections. Support structures, such as connective webbing, are necessary in liquid-based stereolithography systems to keep pieces from floating off. This is reportedly not a problem with SLS, for the unsintered powder acts as a natural fixture and holds the islands in position. DTM also claims that SLS is faster than stereolithography, particularly when forming complex models.

DTM, like Du Pont Co., Wilmington, Del., which offers a stereolithography system known as Somos, plans to offer prototyping services rather than selling the machine technology itself, although DTM spokesmen say the company is considering renting the Model 125 SLS system for $15,000/mo. with an option to buy. (CIRCLE 10)

Meanwhile, 3-D Systems, Valencia, Calif., the only firm actually selling stereolithography equipment, announced at the show that its new SLA-500 system, now in field testing, will be able to produce larger parts than the company's current SLA-250--up to 20 in. diam. and 24 in. high. It will be priced around $450,000. The SLA-250 has a 10-in.-square work area and is priced at $185,000. (CIRCLE 11)

NEW & IMPROVED CAE SOFTWARE

At the show, Intergraph Corp., Huntsville, Ala., introduced I/Cool, a plastics mold-cooling analysis program. By simulating and analyzing thermal properties of the injection molding process, I/Cool enables users to determine optimal cooling-line layouts for uniform mold cooling. Uniform cooling has been show to lead to better stress distribution, reduced warpage, less scrap, shorter cycle times, and ultimately, lower tooling costs.

I/Cool uses models generated by I/Flow, Intergraph's injection flow-analysis program. From an I/Flow model, I/Cool provides the interface to Moldtemp, a thermal-analysis program available from Moldflow Inc., Trumbull, Conn. Moldtemp allows optimization of the cooling circuit layout for injection molding (see PT, April '89, p. 80) and can be operated directly from within the I/Cool package. I/Cool is available for use with Intergraph's Unix workstations for $4000. (CIRCLE 12)

An interface to Moldflow software has now been added to the Pro/Shell-mesh finite-element meshing package from Parametric Technology, Waltham, Mass., to provide an interface to Moldflow software. Like other programs in the Pro/Engineer CAD/CAM software line, Pro/Shellmesh is said to be easy to use in that it uses familiar manufacturing terms to represent complex operations. The company also introduced Pro/Manufacturing, a CAM package that adds process-plan generation, display of intermediate and completed tool paths, material removal, and other data for NC machining to the Pro/Engineer line.

Pro/Engineer software now runs on the IBM RT and PS/i models 70 and 80, in addition to workstations from Apollo and Hewlett Packard, Digital Equipment Corp., Sun Microsystems, Silicon Graphics, Tektronix, and NEC. Prices start at $9500 for Pro/Engineer, $7000 for Pro/Manufacturing, and $3000 for Pro/Shellmesh. (CIRCLE 13)

Computervision, Bedford, Mass., announced an update to its Calma Plastics Designer Tool and Manufacturer Tool Software packages. The company says that programs from Moldflow and Advanced CAE Technology, Ithaca, N.Y., are now easier to access from within the Calma packages. Previously available only for Apollo workstations, the Calma programs have been adapted to run on Vax minicomputers from Digital Equipment. Prices start at $68,000 for Plastics Designer Tool and $46,000 for the Plastics Manufacturer Tool. (CIRCLE 14)