Due to frequent punch breakage of the brittle-hard carbide, economic tool life could therefore only be achieved in isolated cases. The Fineblanking Working Group (AKF), a strategic research network for international and innovative companies from the fineblanking technology sector, is pursuing the goal of using carbides reliably for the fineblanking of high-strength steel. The aim is to significantly increase the cost-effectiveness of the manufacturing process.

In collaboration with the fineblanking working group, the WZL machine tool laboratory at RWTH Aachen University has now succeeded in significantly improving the performance of fineblanking through the use of carbide punches. Scientifically developed measures were used to design a fineblanking tool for the use of carbide punches and to optimize the process control. High-strength sheet metal with a thickness of 6 mm was reliably fineblanked in a series of tests on the Feintool XFT 2500 speed fineblanking press and a test series of 10,000 strokes was carried out. The carbide punch showed hardly any signs of wear, whereas a conventional HSS punch was almost at the end of its service life as a reference. The cost-effectiveness of fineblanking was significantly increased by a substantial reduction in wear.

Use of carbide for fineblanking

The fineblanking process for the use of carbide punches was first comprehensively evaluated in a research project lasting several years. Measures were derived from this evaluation in order to control the mechanical stress on the carbide during stripping, with the factors fineblanking press and process control, tool construction, strip layout and carbide machining playing a central role.

The Feintool XFT 2500 speed servomechanical fineblanking press enables precise process control in terms of process forces and guide accuracy. The selection of suitable press parameters can further reduce the load on the active elements. The fineblanking tool has been completely redesigned to ensure precise and rigid guidance of the cutting punches.

During the tool redesign, all process and tool-related influences that cause a bending moment in the cutting punch were taken into account and eliminated. The result is a detailed list of requirements and design recommendations for fineblanking tools with carbide punches. Based on the requirements determined, the working group member Precision Resource Canada has designed and manufactured a new type of test tool.

The project fineblanking of high-strength steel with carbide has demonstrated the effectiveness of cooperation between companies from different disciplines in the fineblanking working group. In a joint collaboration, the WZL generated knowledge about fineblanking with carbide punches that enables users to apply the technology in industrial practice. In further work by the fineblanking working group, all measures taken for the project will be revised in order to enable the economical use of carbide with the simplest possible measures under the conditions of the special requirements. This lays the foundation for future detailed basic research into the stress situation of carbide punches during the stripping process.