Development of a carbide broaching process for roughing profiled grooves

 

The Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University conducts intensive research in the area of broaching technology. The main field of application of broaching is the manufacturing of profiled grooves in turbine discs for aircraft engines. According to current forecasts of the aircraft manufacturers Airbus and Boeing, the volume of traffic will increase by 4.4 % per year over the next 20 years. This results in an anticipated demand from around 36,000 new passenger aircrafts worldwide, which is accompanied by a corresponding need for new aircraft engines.

A bottleneck process in the production of the engines is the production of the rotating turbine discs, in particular the production step of manufacturing profiled grooves by broaching. The profiled grooves realize a form connection between the turbine blades and the disc. The profiled grooves are subject to the highest quality standards, since in case of failure severe damage to the entire aircraft results. According to the state of the art, tools made of high speed steel (HSS) are used at cutting speeds between vc = 2 and 4 m/min. The development of a new tool concept based on the cutting material cemented carbide has the potential to increase productivity by increasing the cutting speed by a factor of six and doubling the tool life at the same time.

Due to the brittle material behavior of cemented carbide, the challenge lies in the development of an adapted tool geometry, which ensures a process-safe use under the existing thermomechanical load. Furthermore, within the framework of this project, a modular tool design with regard to the achievable process reliability and service life is being investigated. A basic body made of steel with joined cemented carbide cutting edges is used, which further increases the economic efficiency of the use of carbide due to the reduced material costs. Criteria for evaluating the modular concept are the geometric accuracy as well as the stability of the tool along several regrinding cycles.