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Would you put no-name tires on your new Mercedes? Probably not but many users spend months choosing an expensive lathe and then take the "vanilla chuck" that comes with it, says Len Atkins, president, SMW Systems Inc. (Santa Fe Springs, CA).
He contrasts these users with the "enlightened ones" who search out performance features and exploit every competitive advantage they can find. "Smart manufacturers who buy new equipment because business is booming do everything they can to cut part costs. They know that if cost per workpiece doesn't go down, it will be that much harder to ride out a slump later on."
Cutting costs means taking a close look at setup and changeover times, and that means changing mind sets as well as equipment. "Parts cost on a lathe has everything to do with uptime," says Atkins, "yet most manufacturers still think a machine has to be idle for 15-30 minutes while the operator loosens two bolts in each chuck jaw, takes the jaw off, indexes the chuck, takes the second and then the third jaw off."
Changing the mind set is easier than it used to be now that you can retrofit that old machine with new high-tech equipment. For years, machines with short-stroke chuck actuating cylinders, usually Japanese-built, accepted only the standard chucks provided by the builder. Now many high-performance chucks with standard top tooling retrofit to these machines, spurring interest in the new designs. Here's a sample of what's available and ways of using new designs to give companies a strategic edge.
Gripping at High Speed
"Precision work, especially tubes, has always been a problem for power chucks--worse as the spindle stops and clamping pressure increases," says Terry Korndoerfer, applications engineer, MicroCentric Corp. (Plainview, NY). Higher spindle speeds demand some way of counteracting centrifugal force without applying clamping pressures that will distort work.
New jaw-actuating mechanisms avoid this pitfall by permitting roughing with heavy clamping force on the jaws and finishing with less force. These designs, along with tighter manufacturing tolerances on the jaws themselves, make it unnecessary to rebore soft jaws to the machined diameter that they will grip each time they are remounted.
One approach to the problem of gripping force at high speeds is a mechanical-grip-air-release collet chuck...