The requirements for a five-axis machining centre of this kind are high. A fundamental requirement is to have a correspondingly large working area or collision circle. The machine must then provide powerful rough machining, since the degree of machining for the housings – which are made from a special aluminium alloy – is over 60%. Ultimately, though, it all comes down to the finishing. High-quality surfaces are required for the seal seats and in the interior in particular. “The seal is the most important thing about these housings,” explains Andreas Tinner. “Otherwise, it wouldn’t be possible to generate a high vacuum. And if the surfaces in the interior have a high level of roughness or even grooves, it becomes immensely more difficult to create a vacuum. In this case, it can take a number of hours for the pump to generate the high vacuum required.”

Hurdles such as excessively high procurement costs and long delivery times were initially encountered in the search for a suitable machine. Upon a visit to the Starrag plant in Rorschacherberg, however, Paul Oberholzer’s machining team finally found what they were looking for. The site is home to the Center of Production Excellence (CPE), where Starrag tests and optimises sophisticated new machining processes – and it was here that the team was able to see the STC 800 five-axis machining centre in action for themselves.

Starrag developed the STC series for the economic machining of very sophisticated structural components, multi-blades and casings with long cycle times. These machining centres stand out on account of their very good stability and excellent dynamic properties, as well as thanks to the tried-and-tested swivel head that allows for simultaneous five-axis machining. With a maximum workpiece size of 1,400 mm in diameter and height, as well as a permissible workpiece weight of up to 2,000 kg, the Starrag STC 800 satisfies other fundamental prerequisites.

The machine was also available to be delivered on the desired date. Since the middle of 2021, the Starrag STC 800 has been running predominantly in a two-shift operation at Max Schilling’s new production hall in Mollis. The main components that are manufactured are housing components for vacuum handling chambers and for process chambers. PCD tools produce surfaces that fulfil all requirements. The parts are then pre-cleaned and rinsed several times. The assembly then takes place in a Class 7 clean room. In order to be able to supply the fully assembled assembly, Max Schilling has also invested in a clean room of this kind.

“So far, our investment has paid off,” reports Andreas Tinner with satisfaction. “The chamber production is proceeding very successfully. With a single set-up, the housings come out of the machine in perfect condition after around ten hours. We still haven’t had any complaints from our customers.” Instead, what they have received are new requests for housings in even larger dimensions. “We actually hadn’t expected such requests to come in so quickly. However, we have already reserved space in our new hall, which provides a suitable foundation to be equipped for further investment. And we’ll certainly be discussing this with Starrag.”