|The MC 16: designed with powertrain production in mind.|
Although Heller Machine Tools (Troy, MI) has been building transfer line equipment since the 1950s (or, more accurately, its parent company, Gebr. Heller Maschinenfabrik GmbH of Nurtingen, Germany, has been doing so—and has been building machine tools for more than 100 years), Juergen Seybold, vice president, Sales & Service, says that when many people in the North American auto industry think of Heller, they think primarily of its stand-alone machines.
But Seybold points out that the company also produces equipment that falls within a category that the company designates FST, for Flexible System Transferline. The point here is to have a series of pre-designed stations that can be easily fitted together to create whatever capability is required. "This allows us to go from a real old-fashion style transfer line—just drill in and out—all the way to a series of complex stations," Seybold says. At places like DaimlerChrysler powertrain plants in Germany, Heller's system capabilities are well-recognized. And to be sure, systems are at work here in U.S. facilities; the Viper power plant was being produced on Heller machines long before Daimler hooked up with Chrysler.
One of the things that the Heller kit approach allows is a faster ramp-up to production. Additionally, it helps amortize some of the engineering costs that are associated with a program because the FST modules are existing units, not "special" machines in the context of one-offs, machines that require lots of engineering.
Recognizing that there is an advantage to ramping up production, Heller is offering some interesting approaches. For example, one of the stand-alone series of machines it offers, the HCS, consists of multi-spindle heads. This type of machine (pallet sizes range from 500 x 630 mm to 800 x 1,000 mm; head dimensions go up to 630 x 500 mm) is capable of handling medium- to high-volume production. But because a company might want to start low before going high, Heller is offering the same tool interface for a stand-alone machining center as on the HCS. This means that a single-spindle machine can be used to prove out the tooling, then that same tooling can be used on the higher-volume HCS machine.
Because nowadays many companies are considering the use of machining centers alone for their powertrain machining operations, Heller engineers devised the MC 16/25 series of horizontal machining centers. Seybold notes that the working range of the MC 16 is 630 mm in all axes, a size that he says allows the machining of "any V6 block there is." Block machining was a consideration when developing the machine. He points out, as well, that while the price of a transfer line station for a block is typically in the above-$400,000 range, an MC 16 can be obtained for less than $300,000. As the machine's tool magazine can accommodate up to 40 HSK-type tools, it is easy to understand that an MC 16 can out-perform a standard transfer line station in terms of functionality.
The MC 16 offers a rapid traverse rate of 40,000 mm/min. in all three axes. The pallet size is 400 x 500 mm. One of the robust design elements that is part of the machine—one that takes automotive-style operations into account—is the fact that the rotary table provides the Z-axis motion rather than the column. Instead of having the machine come to the work, in effect there is a reversal. (The column does provide Y- and X-axes motions, however.) The machine is accurate, providing a resolution of 0.2 microns and a positioning accuracy of 7 microns.
The standard spindle for the MC 16 goes from 45 to 8,000 rpm. Should a faster rotation be required, then there is a spindle that goes from 45 to 16,000 rpm. Should someone need to go even faster, there is a 45 to 24,000 rpm spindle. Seybold points out that the design of the motorized spindles used is such that if there is a motor failure, there is a quick separation of the spindle and the motor in order to keep downtime to a minimum.
The standard control for the machine is the Heller uni-Pro CNC 90. Other vendors' units can also be designated.
Although the MC 16 is quick, it is not as fast as machining centers with linear motors. Seybold says that Heller has done extensive R&D on linear motors, but that the company has not come up with a way to produce linear motor machines economically. Still, a 24,000 rpm motorized spindle and an acceleration rate of 10 m/s2—both achievable on the MC 16—are nothing to sniff at.