North American mold shops, already facing stiffer offshore competition, are also confronting the new challenges of machining deeper cavities and more hostile material combinations. Both Chicago Mold Engineering and Redoe Mold Ltd. see larger auto headlight molds requiring deeper cavities and longer reaches. Precision Mold Base Corporation, Tempe, Ariz., copes with more difficult bi-metal “sandwiches” in their popular mold bases.

“Mold cavities today typically are 5 to 8 inches deeper than they were just five years ago, requiring more long-reach milling,” according to Jay Noble, lead machinist at RML. “The main drivers are the automotive styling trend toward longer run-outs in exterior light assemblies, and the push for lower part counts.”

That’s the bad news. The good news is that, with high-feed machining practices and leading-edge tooling, alert mold shops are overcoming these obstacles and improving their competitive positions. “Long-reach machining, indispensible for deep cavities, is all about increasing rigidity and reducing lateral cutting forces,” said Bill Fiorenza, die and mold product manager at Ingersoll Cutting Tools.

Following that strategy, Chicago Mold Engineering, St. Charles, Ill., now completes the semi-roughing of extremely deep cavities in high-hard, P20 steel in half the time as before. An Ingersoll Hi-FeedMini cutter feeds at 200 IPM, versus 80 IPM before. A cavity that once took six hours is now done in two and a half.

Likewise Redoe, in Windsor, Ont., finishes 15- to 22-inch deep pockets in hardened stock in half the time as before ,and completes 8:1 aspect holes four to five times faster. Despite the 300-400 IPM feed rates, versus 50 IPM before, edges last 20% longer. They do the deep work on a husky Toshiba VBM tooled with a high-feed Ingersoll Form-MasterV Master V cutter mounted on an extra-rigid Inno- Fit shank extension.

“We used to have to slow down the deeper we went, but not anymore,” Noble added. “Even at these rates, the sudden insert fractures that can haunt long-reach work are a thing of the past.”