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November 2, 1999

5 Min Read
Making changes on the fly

Moldmakers often wince when the subject of engineering changes comes up. Specifically, they point to an obvious irony. As customers ask for increasingly compressed lead times, they are also sending larger numbers of engineering changes.

Although the practice of concurrent engineering is often faulted for this phenomenon, the real culprit is the misapplication of concurrent engineering concepts. Ideally, toolmakers, OEM designers, and molders should work on a project from the start to prevent numerous errors in the downstream process. Before designs are set, input from moldmakers can help ensure that a part is in fact moldable, and that the tool can be built cost-efficiently. This, in turn, helps to reduce the number of changes required.

Unfortunately, some OEMs still view early supplier involvement as an addition to the product development cycle rather than a time saver. In reality, toolmakers often receive information too late, forcing backend changes for moldability, increasing lead times and tool cost.

Scott Lyngaas, CNC and programming manager at Foreman Tool & Mold (St. Charles, IL), doesn’t have any easy answers to this trend. “As OEMs step up the pace of bringing new products to market, they are eliminating some review steps and asking toolmakers to complete details,” he explains. “As a result, we need to do two things—find and keep talented people and adopt new technologies that will speed up the toolmaking process.”

According to Lyngaas, there are also exceptions to the rule. “Concurrent engineering does have its benefits when applied correctly. There is a reduction in the bureaucracy at customers’ engineering organizations. As a result, we can often get files to work on even before the part design is finalized, which lets us jointly resolve any tooling issues up front. In many cases, this alone can save us two weeks’ time.”

Reality Check
Foreman is a 15-year-old toolmaker, with a 33,500-sq-ft plant that employs 80 in two 12-hour shifts, seven days a week. Foreman offers turnkey services—design and development, moldmaking, and rapid prototyping. Primary markets are electrical/electronic, automotive, appliance, and metering devices for both industry and home.

“Our customers’ concurrent engineering projects can affect us dramatically,” says Lyngaas. “Very often we get incomplete geometry, and sometimes there are changes on a weekly basis. Some projects are released for tooling on what is fundamentally a best-available-information basis. Functional engineering for subassemblies, and often part geometry itself, continues even while initial work on the tooling gets underway.”

When incoming CAD geometry is not as complete as expected, engineers and programmers need more CAD time than expected before any mold machining can start. “We may get new changes on a project even before the previous changes have been implemented,” Lyngaas adds. “On a few jobs we get a new file every day.”

To compensate, Foreman practices its own brand of concurrent design and engineering. Programming begins almost immediately, before the design is complete. To ensure that the current file is the only one being worked on, Lyngaas maintains a strict print and electronic file control system. “We typically deliver a mold in eight weeks,” he says, “and even less if all goes well.”

Foreman has a large cadre of software: PowerShape and PowerMill (Delcam International); Camax (SDRC); Pro/E (Parametric Technology); SurfCam (Surfware); and Cadkey. Most of Foreman’s CNC machines are Mazak and Mitsubishi products.

Stepping Up the Pace
Two recent moldmaking projects—a door handle bezel and a joystick control button—illustrate Foreman’s work. According to Lyngaas, the door handle bezel, which nestles into a car door’s interior, went through so many iterations that it has become a concurrent engineering classic. The large number of changes in the bezel design meant that Foreman engineers and programmers constantly had to compare new and newer file versions to find changes.

“Previously,” he explains, “this was done by overlaying the new and old geometries, one in red and one in, say, blue. Then we would visually examine the image. This was tedious and often took hours on complex parts.”

Using a PowerShape function called Comparison Check, however, mold designers can now automatically identify the changed geometry and eliminate all redundancies. “It takes about 30 minutes for the size files we typically work with,” he adds. “We also use the software to add draft angles to ribs and bosses.”

Sculptured and ergonomic surfaces, a big trend in automotive interiors, present another challenge for Foreman’s mold designers. This is typified in a second project that involved a complex-shape button, part of the joystick control for six-way power seats and mirrors (Figure 1).

“What was once a nondescript knob has evolved into a part that users can operate intuitively by touch,” says Lyngaas. “This was a pyramidal part with a rounded top. The inside was hollow except for a threaded boss for mounting on the joystick. The whole part would fit in a 1-inch cube, but it was a geometry challenge from the outset. The file came in untrimmed and there were problems with variable radiuses.”

A vertical cylinder subtracted from each of the four side faces was the critical geometry. The resulting recesses reassure drivers their fingers are in the right places. Cylinder edges were blended, with varying radiuses, into the sides’ other contours.

“We could not do this with previous software without some very cumbersome and time-consuming workarounds,” he says. “As an example, once the first side was done, our previous software did not have a way to drive the radiuses around the other three sides of the part.”

Foreman’s programmers speculated that holding the variable radiuses of the vertical cylinder while maintaining the part wall thickness might have been too big a calculation load. The challenge was handed to programmer John Lenert. “The button’s design was done with PowerShape in 31/2 hours,” recalls Lenert, “and the entire job was programmed in just two days.”

Contact information
Foreman Tool & Mold Corp.
St. Charles, IL
Rick Foreman
Phone: (630) 377-6389
Fax: (630) 377-5364
E-mail: [email protected]

Delcam International Inc.
Windsor, ON
Tracy Pringle
Phone: (519) 974-8088
Fax: (519) 974-8170
Web: www.delcam.com
E-mail: [email protected]

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