When it comes to higher-volume part production, one of the advantages that Greg Hyatt, manager of Product and Process Development, Makino Inc. (Mason, OH), points out that machining centers offer in place of conventional special machines actually occurs before production begins: "The process can be proven on a single, standard machine, rather than waiting nine months or more for a special machine to be built." This early validation—or the ability to determine early on whether there needs to be equipment modification—is, Hyatt explains, "Extremely valuable for risk control and for the introduction of new products." That is, not only does it help provide a wider window for fore-casting, but there is also the opportunity to deal with fixture problems or even product design changes that are par for the course in most any program.
This proof-of-concept capability then leads to another advantage of machining centers versus special machines: there is the opportunity to ramp up incremental production (and ramp down as demand declines).
Because there is an increasing move toward more flexible medium- to high-volume systems—whether this means a machining center station within a fairly fixed transfer line or an entire system of machining centers—there is, Hyatt suggests, more reliability being built in to machining centers. Before the machining center approach caught on, when there were just the onesy-twosy sort of installations, the machines were engineered and built for these production-oriented applications almost as though they were special machines. "Now," Hyatt points out, "volumes are higher for agile equipment, so we can amortize engineering cost across more machines and make investments in reliability and maintainability that the product couldn't have carried in special or lower volumes."
Among the things Makino is doing to help assure the reliability of its machining center equipment are:
- Spindles: Circulating coolant through the spindle, including cooling the inner and outer races. This helps assure the correct preload for any duty cycle.
- Designed for Dry: "It used to be assumed that we'd use fluid to flush chips. But because of health, safety, and economic reasons, there's more dry machining," says Hyatt. Consequently, the bed, way covers, and guarding for new machining center designs are such that the removal of chips without fluid is accommodated.
- Toolchangers: Hyatt admits that toolchangers were once a problem with regard to timing elements. But Makino is using a single cam design so that everything works off of the action of that cam so these timing errors are eliminated.
- Increasing Capability: One of the knocks against machining centers in place of more traditional transfer lines is that pallet qualification can be a problem vis-a-vis quality (i.e., lots of pallets need to be qualified, which can be a considerable pain). However, one means by which that problem can be minimized is by having multiple operations performed on a single machine. So Makino has developed the means by which operations including honing, grinding, line boring, and gundrilling can be performed by the machining center. What's more, Hyatt suggests that one of the problems with some machining center-based lines had actually been the special machines developed to do those operations, a problem that has been eliminated.
"We started working 10 years ago on some of these developments," Hyatt says. "Our machines have become economically competitive with dedicated equipment in high volumes."