Making the switch to 3-D

Toolmakers and OEMs still wrestle with the fact that the longest lead times for most products reside with the tooling needed to make the plastic components in an assembly. Moldbuilders at one division of electronics giant Matsushita (Osaka, Japan) believe they may have won a round or two by switching from 2-D CAD to 3-D solid modeling.

Matsushita Electric Co. Malaysia (Melcom), introduces several new products every year for the Southeast Asian market, and produces a variety of consumer appliances ranging from refrigerators and TVs to vacuum cleaners and washing machines. Long lead times for building molds at Melcom were putting a crimp in the time-to-market race. Molds were first designed in 2-D CAD, which couldn’t define the complex contours found in most of the parts. So designers then created a wooden model that they used to copy mill EDM tooling.

Building the physical model, producing the EDM tooling, then machining the mold often ate up most of the product development time. For larger plastic components of a washing machine, for example, the machining time alone was about eight weeks. Compounding the problem was the fact that Melcom had only one EDM machine and several projects going at once. Lowered accuracy of the copy mill/EDM method also required molds to receive additional hand finishing to meet quality standards.

Technicians decided to evaluate 3-D solid modeling software in hopes that it could reduce time to market. According to technician Hui Ling Soh, the basic idea was to fully define the mold as a solid model so that it could be produced on a machining center. “This would eliminate the physical model and EDM, allowing us to produce the mold in a single manufacturing step,” Soh explains. After six months, they chose Unigraphics for its ability to completely define complex contours and easily convert the geometry into a CNC program for machining.

One of the trial projects, a washing machine pulsator, proved that making the switch to 3-D was well worth the effort. “We designed and produced the mold in eight weeks, compared to the 12 weeks previously required for similar molds,” adds Soh.

To begin the project, designers used the integrated free-form modeler to define complex contoured shapes. For the more regular shapes of the geometry, they switched to feature-based modeling techniques. Although this process took the same amount of time devoted to geometric design in the past—two weeks—the former 2-D process had captured only simpler geometry.

Eliminating the physical model was easy. Designers simply used the solid part model as the part master. “This improved the accuracy of our downstream processes by avoiding translation errors,” Soh says. “We were able to produce the CNC program directly from the solid model.”

The software contains a milling module that helps automate definition of initial roughing passes. Semifinishing and finishing passes with a ball-nose end mill were then generated by selecting surfaces and entering machining conditions.

Technicians were able to program a majority of the machining this way, resorting to EDM for one area of the part with several radiuses smaller than available tooling. But again, the solid model was used to program the electrode for EDM machining, eliminating the need to build a physical model.

Once the CNC file was downloaded to a Makino CNC machining center, Melcom used the software’s visualization to verify and display the CNC toolpath. Machining operations were completed in four weeks, half the time required in the past.

Even the mold inspection process was simplified. Using the solid model to program the coordinate measuring machine saved time, and the results showed that the mold was considerably more accurate than those produced in the past. It needed only one day for hand finishing, as opposed to seven days previously.

Soh foresees even greater time savings for future projects. “As we gain proficiency and confidence in the software, we expect to be able to move more quickly on upcoming assignments,” he says. “We will also be able to reuse existing master models to develop new products with similar geometry.” In addition, Melcom plans to make use of high-speed machining capabilities inherent in the software for finer surface finish and less hand working.