Workholding For Job Shop FMS

One of the most interesting parts of my job is that I get to visit a large number of manufacturing facilities during the course of a year. My travels not only take me around North America, but also to Europe, Asia and South America on a regular basis. As the world continues to shrink due to technological advancements, more U.S. companies are finding it profitable to compete in the international arena. Observing how "world class" manufacturers are solving their production problems can provide us with some ideas on how to improve our own facilities.

Germany has long been recognized as a metalworking powerhouse. Hydac Alleingang, a manufacturer of hydraulic and pneumatic components, was founded in 1963. Today there are eight plants in the northern industrial area of Sulzbach, Saarland. Plant 5 is not only the central production plant for the power steering units sold to the automotive industry, but it also is responsible for supplying sub-components to the other Hydac facilities. This is one large job shop.

Reinhold Lang, director for central production, says, "We produce 40 percent of the needed mechanical parts for all eight plants. We concentrate on producing parts as competitively as on the open market. To do that, we invest in the most modern equipment, plus accessories that ensure the profitability of these operations."

The hydraulic components are machined on a flexible manufacturing system that consists of three Makino horizontal machining centers and a pool of 23 pallets that carries special tower clamping systems from Hilma-Roemheld. In the two years that this program has existed, the system has used 1,500 NC programs to produce 2,000 different workpieces.

"With the purchase of this highly productive system, we wanted to reduce setup time, making the clamping system universal," says Mr. Lang, "so we looked around for a clamping system, and that led us to Hilma-Roemheld. We were impressed by the effectiveness of this clamping system, but with our multiple part sizes, the machines were not being used to their full capacity. After intense discussions, something happened that I still have trouble understanding. Hilma came up with a new clamping system within a week that answered all our requests. Our Fluid Power systems and compact hydraulic components are mostly produced on the FMS. We do not produce for warehousing anymore. In today's philosophy, we produce only to fill orders; we store only NC programs, not parts."

Manfred Helmer, production group supervisor at Hilma, says, "At the start we had to jump over our own shadow. We had good experiences with the new design, but had not realized (what) the single part design needed. With Hydac, we found a quick solution. One of the main criteria, among others, was to provide a workholding device that would increase uptime of the machines. In addition, the maximum weight on the pallet had to be reduced. We manufactured the base plates out of the strongest aluminum available. The towers are produced in one piece. That reduces costs and increases stability as well as precision."

The Tower System is extremely robust and cost-effective, suited for at least four equal or different workpieces. The one-piece design of the tower, coupled with fixed jaws that are an integral part of the base plate, ensures maximum precision and stability. Clamping points arranged at 90 degrees allow for machining workpieces on three sides in a single clamping application. Many accessories and field-tested extras extend the range of applications.

Mr. Lang continues, "We now have our machining center and workholding operation organized so that if we have a part that already has been programmed we can begin the job with almost no setup time. We can produce a power steering component with a touch of a button, regardless if it is a single part or a complex sub-assembly."

Mr. Helmer concludes, "The challenge to convince a potential client brought this to a quick solution. We realized that this new concept could be marketed on a broader basis, especially for multiple clamping. Horizontal machining centers need to be flexible. Despite the small lot sizes, these systems are very profitable."

Mr. Lang says that the results have been so convincing the company will outfit its second line of three Makino A-55 machining centers with the same clamping system.

For more information, contact Manfred Hilmer at Hilma-Roemheld GmbH, P.O. Box 1220, D-57260 Hilchenbach, Germany, telephone 49-2733-28-10, or fax 49-2733-28-11