Mold analysis, rapid prototyping dominate AutoFact Show news.

A long awaited midplane generator for quick conversions from CAD models to mold-filling meshes and a new 3-D modeling system that works in an office environment topped the plastics-related news at the AutoFact '95 exhibition in Chicago. A new 3-D CAD system for personal computers also debuted at the show.

MOLD ANALYSIS MADE EASIER

If creating a midplane mesh (the starting point for mold-filling analysis) from a 3-D solid model gives you headaches, Moldflow Inc. of Shelton, Conn., has a new remedy. Its automatic midplane generator does the job in minutes rather than days. With the touch of one computer key, "MF/Midplane" first imports the model from the CAD package and then automatically performs classification, matching, collapsing, and stitching steps. The result: a fully connected midplane mesh. That's a big advance over days or weeks of manual editing or model re-creation, says Moldflow director Roland Thomas.

In recent tests conducted by Moldflow, MF/Midplane produced what the company termed "excellent" results in about 70% of the models tested, while 15% more gave "acceptable" results. The remaining 15% of cases were "problem parts." MF/Midplane is slated for release early this year at a cost of roughly $5000.

In other CAE news, Moldflow and Matra Datavision Inc. of Andover, Mass., announced a North American partnership through which Moldflow will offer Matra's "Geometry Quality Checking Tools" - software that provides a quality-control check of your model. And the two companies will both market the "Total Plastics Solution" combining Moldflow's analysis products with Matra's CAD software, especially the Strim surface modeler. "We've found that the cleanest IGES files by far were from Strim," notes Moldflow's Thomas.

NEW 'OFFICE MODELER'

Is it an office copier? Is it a printer? No, it's a new modeling system from 3D Systems Inc., Valencia, Calif. About the size of a large copier [ILLUSTRATION OMITTED], this new modeler marks the company's first foray into the office environment with a modeling machine that produces no excessive fumes, heat, or noise. Using a process called "Multi-Jet Modeling," or MJM, the system works by selectively shooting layers of a proprietary thermoplastic material through a computer-controlled print head similar to the type used in contact labeling systems.

Users load the machine by dropping walnut-sized pieces of the $50/lb material into a feed hopper and melting mechanism. Like a printer, the new modeler hooks up for use with just a power cable and an Ethernet connection to the user's CAD network. Set-up is no more difficult than for a printer - the user simply makes selections from an on-screen dialogue box. MJM software submits jobs as .STL files to the machine and schedules them in a queue (similar to a printer). Advanced scheduling options are in the works to allow users to interrupt the queue in order to arrange different-size parts for maximal utilization of the platform space.

Besides being easy to use, the machine is fast, says product marketing manager Mervyn Rudgley. One demo part, a palm-sized solid telephone model with surface details and an antenna, took about 4 hr. "The machine is getting 20% faster every six months as we refine its design and software," he says.

3D Systems is more modest about MJM's accuracy, which Rudgley says is "measured in hundredths of an inch, not thousandths." But that accuracy is just fine, he notes, for the machine's intended use as a "concept modeler" rather than as a maker of functional prototypes or casting patterns. Price for the whole system is $60,000.

NEW RAPID TOOLING PROCESS

At press time, DTM Corp. of Austin, Texas, supplier of selective laser sintering (SLS) machines for rapid prototyping, was slated to commercialize its new rapid-tooling process by the start of this year. Called RapidTool, the process creates injection mold core/cavity sets from SLS parts. First a "green" part is produced by SLS from a mixture of metal powder and thermoplastic binder. The parts go into a furnace to burn off the binder. The porous parts are then infused with copper, creating an alloy said to be comparable to 7075 aluminum.

While the process was first announced a year ago, DTM has only recently brought the accuracy to a level appropriate for injection molds. DTM says RapidTool now offers predictable shrinkage of 2% in all directions from green stage to final part. DTM estimates overall accuracy to be around [+ or -] 0.005 in. on the first inch and [+ or -] 0.001 in./in. thereafter.

A RapidTool module will cost $37,500 - not including the $50,000 furnace and $311,000 SLS 2000 modeler.

DTM also announced that it has a new family of amorphous copolymer model-making materials called TrueForm for soft tooling applications such as RTV silicone molds. To achieve the necessary surface finish, TrueForm consists of spherical particles under 30 microns. "We can achieve RMS 200 right out of the machine," reports Dr. Michael Ervin, v.p. of engineering. DTM's polycarbonate, by contrast, typically yields a rougher finish out of the machine and requires more hand finishing. Also, TrueForm exhibits roughly half the shrinkage of DTM's polycarbonate and has a lower processing temperature (140-158 F).

In other rapid proto-typing news, Parts Now of Northridge, Calif., is a new service bureau established by Soligen Technologies Inc., also of Northridge, to use its Direct Shell Production Casting (DSPC) process. DSPC produces ceramic molds for casting metal parts such as prototype molds. Working from a CAD model, the DSPC system first creates a virtual version of the casting shell. The company's rapid-prototyping machine, the Shell Casting Unit, then builds the shell from successive layers of a ceramic powder and liquid binder shot from an ink-jet print head. The resulting shell is used as a mold for casting metal parts such as a core and cavity set. In all, the time from CAD art to metal part can be as little as a day, says program manager Gordon Clark.

Stratasys, Inc., Eden Prairie, Minn., now has a medical-grade ABS (FDA Class 6) for its fused-deposition modeling (FDM) system. Stratasys also reports an innovative new use for FDM: Andersen Corp. of Bayport, Minn., has used it to model a variety of extruded window profiles.

BPM Technology Inc. of Greenville, S.C., has shipped the first models of its Personal Modeler, which uses a five-axis jetting system to build models from small drops of molten thermoplastic (see PT, Sept. '95, p. 52).

PC-CAD SOLID MODELER

The newest entry in Windows-based solid modeling is "SolidWorks '95," sold by a Concord, Mass., company of the same name. It uses the Parasolids modeling kernel from EDS Unigraphics for parametric, feature-based geometric modeling on a PC. SolidWorks includes the "Feature Manager," an icon- and text-based history of the model's construction. SolidWorks is available for Microsoft Windows NT and '95 and costs $3995.