Customized Machines with Software CNC

With its specialist knowledge in the field of induction heating, Stemmermann GmbH contributes to the general feeling of safety. The parts, which are mass-hardened, must resist extreme stress, for example during rudder setting in an Airbus airplane or in shock absorber piston rods. In addition, 18 employees produce several million parts per year in two shifts. Since the start of production in 1974, the company, now managed by the second generation of the family, has acquired extensive know how in processing sintered steel.

Everyday production is characterized by short-term, high volume orders which are often collected on the same day. This requires considerable flexibility in production planning as well as in use of the individual machines. In the year 2000, a full order book made the company think about expanding their manufacturing capacity, but a borrowed test machine with controls from a well-known manufacturer could not convince the team responsible at Stemmermann. "Our staff found the controls particularly inconvenient to use", remembers managing director Dirk Stemmermann. "The controls were also inflexible, awkward to program and the operation was not clear for the workers."

"Due to its flexibility, OpenCNC allows the customizated building of machines."

Thanks to retrofits with OpenCNC, even several older machines reach a high level of productivity.

The open software CNC from MDSI seemed to be a suitable solution. OpenCNC offered not only the required flexibility with respect to building new machines but also the chance of increasing the performance of some older machines by up to 20 percent with retrofits. The concept of an open-architecture software CNC allowed the affordable building and customizing of new machines to the exact production needs of Stemmermann GmbH. The use of standard PCs and other standardized hardware components means that the company is largely independent of any one controls supplier, especially in the long run. "Previously, the mechanical life of our machines mostly outlived that of the controls", explains Dirk Stemmermann. "So any repairs or spare parts required for the controls soon incurred considerable costs."

Here the managing director saw one of the strengths of OpenCNC, as standard components can be replaced relatively easily in the event of repairs or if more powerful new hardware becomes available. And the software itself can also increase machine productivity as new versions can be installed at regular intervals.

The development and construction of the first machine took three months. "The delivery period for a ready-made machine would have been six to eight months, plus the time required for the necessary customizations here at the company”, says Dirk Stemmermann. "The bids that came in were considerably more expensive and the machines wouldn’t have been as universal for use with our wide range of parts. With OpenCNC, on the other hand, we have machines which are tailored exactly to our needs."

The good experiences Stemmermann GmbH has had with OpenCNC have prompted the company to use the software CNC on a new kind of machine with a dual-frequency generator. With 100 kilowatts of power at a frequency of 200 to 250 kilohertz and 200 kilowatts at 20 kilohertz, it enables contour-accurate hardening, for example of gear-wheels, while shortening the heating process from 2.8 to between 0.2 and 0.5 seconds. "With this new machine generation, we are entering new territory together", says Christian Schlomann. "But we are convinced that the flexibility of OpenCNC will 125 ill also be helpful here and that we will be able to realize this ambitious project." As the possibilities of reducing auxiliary process times have been exhausted, the dramatic shortening of the heating process means an enormous increase in productivity.

"The new machines running OpenCNC are tailored exactly to the needs of Stemmermann GmbH."