Why turn to CNC grinders?

Manufacturing Engineering, Sep 1999 by Enk, Randall

Job shops that switch from manual to CNC systems find they improve productivity and compensate for lack of operators with traditional skills

Not only is following the path of least resistance human nature, it's also good business. Take, for example, the tendency of progressive machine shops to replace manual grinders with CNC grinders.

Unlike the machining and turning center industry, which has embraced CNC technology, the grinder industry has been a decade behind, due to grinding's lack of priority on the shop floor. It's hard to believe, but the majority of grinder sales are still conventional machines.

Okamoto was the first to develop CNC profile grinding, introducing it at IMTS in 1968. As Technical Services Manager for Okamoto, I can say that every one of our customers who has replaced manual grinders with CNCs has had positive results-typically results that exceeded their expectations.

Take a good, long look around the grinding shops in this country, and you will see the graying of America. Manual grinding is, sadly, a dying art, and one that has more variables than any other machining process. It takes years of dedication to understand its nuances. True grinder artisans know intuitively how to compensate for variations in room temperature or humidity. Grinding in the morning can differ from grinding in the afternoon. Grinder operators continually adjust the process by dressing the grinding wheel and repositioning the infeed. Without accurate compensation, the tolerances required today would be difficult to achieve.

Because grinding is the final operation in many manufacturing processes, the tolerance relationships between different surfaces on the same workpiece are critical. Being able to grind all of these areas in a single setup ensures proper accuracies. CNC grinding achieves this objective more easily, quickly, and accurately than conventional grinding.

In today's job market, it's rare for a machine shop to find a young apprentice eager-and patientenough to learn the art of grinding, which can take many years. Someone just out of high school has cut their teeth on computers, electronic games, and automation. Programming CNC grinders is a more natural progression for them.

Talented grinder hands can be very costly due to their knowledge and experience. This high labor cost creates a challenge when competing with low-cost overseas labor. One of Okamoto's customers, Bill Kushmaul, president and CEO of Tech Mold (Tempe, AZ, is passionate about this topic.

"We need to reduce the labor portion of our jobs in order to compete in the new global economy. A global economy brings many benefits. It also brings plenty of foreign competition. For us to compete in this economy today, and for years to come, we must reduce the cost of our products," says Kushmaul.

"Every shop owner has a fantasy of getting the most out of his capital by having a full talented night shift. As we know, talented people often do not like working nights. This is unlike our offshore competition. I have several colleagues in the Pacific Rim that report a full labor force 24 hours a day, seven days a week. The people there are highly motivated. They know that it took hard work to build America so in a sense they are driven to accomplish the great things we did. That is precisely why, in order to be successful we need to work smarter, not harder." These observations explain why Kushmaul has become a CNC user.

He purchased an Okamoto ACC-7-18DXNC seven years ago. Since that time, he has expanded with the purchase of four ACC-8-20DXNCP machines, one of which incorporates autoloading. The machines at Tech Mold have working envelopes of 6 x 18" (150 x 457 mm) and 8 x 20" (203 x 508 mm) chuck sizes, 2hp (1.5-kW) grinding-wheel spindle motors, and 8" (203-mm)-diam grinding wheels. All of their machines have standard Fanuc controls, which allow two-axis simultaneous motion, as well as indexing devices.

Tech Mold makes precision injection molds for the medical, packaging, and high-end consumer electronics industries. Kushmaul employs 155 people in a mold-building facility.

At Okamoto, we've found there is no typical CNC grinding customer. They can vary from mold shops, to high production manufacturing, to job shops. CNC grinders can't be pigeon-holed.

Boston Centerless (Woburn, MA) is a job shop that discovered CNC grinders' versatility. Three months ago, we installed our IGM-15NC internal CNC grinder, which has a Fanuc control and linear motion guideways (which enable contour grinding and precise axis positioning). A very compact machine, the IGM-15NC can grind internal diameters as large as 6" (150 mm) with lengths as long as 5" (127 mm).

Len Pagliaro, engineering manager for Boston Centerless, says, "We do cylindrical and ID grinding specialty work. We can grind jobs on a conventional machine, but we aren't always able to grind to the necessary tolerances and production quantities."

One source of relief for Pagliaro is the positive reaction of his team to the new CNC grinder. "Our manual grinding people like the CNC. Even our oldtimers want to learn it. It took a good month before the guys felt comfortable using the CNC, but once you get the control down, it's an easy machine to run."