February 2008 Edition

VMC

Injecting Speed into the Mold Business

Impressed with the reliability of a manufacturer's VMCs, a mold producer adds a fifth machine to retain a competitive advantage

The need to double or triple machining feed-rates to gain faster cycle times was a factor in the decision by Great Lakes Mold, Shelby Township, MI, a contract mold making shop, to add a Fadal VMC 2216FX to its shop. The machine is its fifth vertical machining center from MAG Fadal, Chatsworth, CA.

In addition to producing molds for automotive suppliers, Great Lakes builds molds for its own injection molding operations, including electrical connectors and safety restraint latches. Bases, inserts, slides, lifters, and other mold details, as well as graphite electrodes for EDM operations, are machined on Fadal VMCs.

"This is a tough business, but we successfully compete on a global basis for injection mold work," Greg Adams, president of Great Lakes Mold, said.

"Our mold-building facility has the output of a shop twice its size. We routinely do lights-out unmanned machining, and our wire EDM machines run all night. Our high-productivity machining capability is a definite advantage that we have over others."

Cutting speeds are up to 250 ipm

Its newest addition helped Great Lakes maintain that advantage. Cycle times have been reduced by as much as 75 percent with the MAG Fadal 2216FX compared to its older machining centers. Typical cutting speeds are up to 100 ipm, even on hardened steel. Previously, feed-rates averaged 40 ipm. Depending on the application, feed-rates can be as high as 250 ipm. Mold components are typically hardened to 48 R_C to 52 R_C, but can go up to 68 R_C, with the heat treatment process occurring between the rough and finish cuts. P-20 and S7 are used frequently, as well as high-grade aluminum — QC7 — for prototype work.

Cycle times have been reduced by as much as 75 percent

"The core and cavity machining workload can be a bottleneck, especially when we're producing eight-cavity or even 16-cavity molds," Ron Kriss, production supervisor, said. But, not anymore.

It takes about five minutes to perform a contour machining operation that once took 20 minutes. Higher feed-rates, combined with skillful programming, is the reason. The more cavitations in the mold, the more the potential time savings.

Adding to the new machine's productiveness, the Fadal GE Fanuc 0i-MC control that is attached includes a look-ahead feed feature that optimizes cutting speed through advanced data processing power.

Trajectory errors are reduced, and corners are sharper. A preview function lets the control consider multiple upcoming program blocks to optimize acceleration and deceleration of the cutting speed. An automatic corner override reduces the feed-rate when cutting inner corners, preventing an overload of the cutter and improving the surface finish.

Net Machining

Achieving superior dimensional tolerances and surface finishes without post-machining is a priority at the shop.

"We've been focused on net machining since before there was a term for it. In almost all applications, we've eliminated fitting of sub-inserts, spotting of the core and cavity, and bench work," Kriss said. "The accuracy of the Fadal machines plays a big role in our machine-to-zero capability."

“It takes about five minutes to perform a contour machining operation that once took 20 minutes”

On the new machine, rigid box-way construction and dual-mounted ball screws contribute to the consistently tight tolerances and surface finishes. Those at Great Lakes are also happy with the reliability and service-ability of their Fadal machines. Sales and support come from the local Fadal dealer, VMC Technologies, Troy, MI.

According to Bruce Proctor, senior mold maker, the toughest challenge in recent years was creating a complex mold for a fuse-panel frame. A mold of 450 inserts, each of them different, was involved.

"We pulled it off in seven weeks. The previous, original version of the mold that had been built in China took months," Proctor said. "If we'd had the faster Fadal 2216FX at the time, it would have been easier in terms of the machining of inserts on a tight schedule." MAG Fadal

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