Maschinenfabrik Berthold Hermle AGMaschinenfabrik Berthold Hermle AG

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User reports

Precision milling for efficiency

Christian Frey, Managing Director and creative developer of small gas turbines and mini jet engines

From model making enthusiast to businessman: How Christian Frey began by turning his hobby into a career, developed that into a high-tech company, and how Hermle‘s 5-axis CNC milling technology contributed to it all.

From model builder and later industrial modeling craftsman in conventional tool and mold making through model (aircraft) making to small gas turbines and mini jet engines – to the early history of a company, BF-Turbines GmbH & Co. KG, D-63856 Bessenbach, nothing sums up the whole story better than the proverbial warning “start-up at rocket speed”! The following user report, explains what this all means. Christian Frey came in contact with the 5-axis CNC high-performance machining centres of Maschinenfabrik Berthold Hermle AG for the first time in his capacity as model builder and industrial modeling craftsman concerned with parts manufacturing in tool and mold making described above. His first real experience with the machines was very positive. The scene changes: It’s not unusual for a modeling craftsman to pursue model building of a different type in his free time, for example model aircraft – of course with a machine that actually files. An affinity to the corresponding jet engines is somewhat unusual, however, as the “true” model aircraft fanatic places great value on authenticity. It’s not simply a matter of scaling down the size of the aircraft, recreating it with smaller dimensions, but ideally of fitting it with an “authentic” motor or jet engine, not just with the usual electric drive. But Christian Frey was not really satisfied with what was available on the market. So he went to the factory and started to develop small gas turbines and mini jet engines for model aircraft. Somewhere during a period of four years the idea of gas cannisters emerged for absolutely realistic jet model building, true in every detail.

The Hermle C 30 U machining centre

You always remember the good parts!

So Christian Frey stopped developing and manufacturing alongside his job and founded BF-Turbines GmbH & Co. KG in close collaboration with his test pilot Florian Keilwitz. To move development forward, implement optimization measures without losing time and reliably ensure continuity in production and spare parts supply, the decision was made to set up in-house manufacturing. Christian Frey explains: “Since turbine manufacturing is characterized by special machining requirements, and since I was familiar with the performance capabilities of Hermle machining centres from earlier days, it was clear that we should buy a 5-axis machining centre right away.” That happened in the fall of 2011 and since then the machine has been used for highly flexible and productive manufacturing of both turbine and jet engine parts in small series production as well as for prototypes and spare parts. The C 30 U dynamic 5-axis CNC high-performance machining centre is ideally suited for this great diversity of machining tasks in a challenging range of parts. After some time, series production status is reached and a higher quality standard is achieved – and approval is issued for a flight altitude of 10,000 m. The actual capabilities, practical suitability and long-term reliability of BF turbines can perhaps be well assessed by noting that the small gas turbines and mini jet engines are frequently used today in the reconnaissance drones of well known defense technology companies. Not without pride Christian Frey notes: “As standard products we currently have the performance versions B100F with a thrust of 120 N at 125,000 rpm and B300F with a thrust of 300 N at 104,000 rpm in the product line. These are true power packs and the only way we could do this was by keeping the components compact and machining every part until it truly reached its smallest possible dimensions, to save weight and space. The parts must also be highly precise and optimally designed for flow, meaning the surfaces must be machined perfectly to achieve maximum efficiency and the lowest possible consumption of jet fuel. So far we have produced over 450 turbines on the Hermle C 30 U 5-axis CNC high-performance machining centre.”

A selection of challenging, turbine parts for 5-axis machining, made of high-strength aluminum, semi-finished Inconel and fine cast Inconel


The maximum level of availability offered by the Hermle machining centre is indispensable for ensuring availability for deliver and profitability. Not just because of the familiar Hermle attributes: 5-axis functionality, high performance, long-term accuracy and high machining quality, but also because of their proven excellent and competent service and literal immediate response capability to malfunctions.

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