In the field of turning, drilling, milling we are engaged in experimental and simulative investigation of classical machining processes with definded cutting edge. The focus is on the interaction of workpiece and tool, i.e. the influence of the materials including tool coating, the cooling lubricant and its supply as well as the tool geometry and the cutting data. For the simulation well-known FE-tools like Ansys and Abakus are used but also new particle-based methods are investigated. The process evaluation is based on the forces, the workpiece surface and dimensional accuracy as well as the tool wear. The focus is on materials that are difficult to machine.
The turning process, in particular the orthogonal cut, usually forms the basis for characterizing the specific cutting properties of workpiece materials. Accordingly, a test stand based on an NC lathe was constructed, which is equipped with force measurement, acoustic emission sensor and pyrometers, so that chip length, chip compression and temperature of the chip can be measured. Furthermore, an in-process tribometer is available that allows the measurement of the friction coefficient between a spherical pin and the newly generated workpiece surface under process temperature and cooling lubricant conditions.
The most common machining operation is the drilling of holes. Special in-house requirements on which we work are the drilling of fibre-reinforced plastics, partly in sandwich composites with metallic materials made of aluminium or titanium and the drilling of holes in hard ceramic materials. In the case of carbon fibre reinforced materials, diamond-coated tungsten carbide twist drills and coordinated geometry have significantly improved the service life of such tools. In the case of hard ceramic materials, new solutions have been found by circular milling with PCD tools, whereby these PCD cutting edges have been given specific geometries with the aid of ultra-short pulse lasers in cooperation with our laser group.
In contrast to turning and drilling, the load on the individual cutting edge varies greatly during one tool revolution in a milling process. The cutting edge makes an interrupted cut, which results in a strong dynamic mechanical load on the "machine - tool - workpiece" system. Therefore, the main area of research for this method is the investigation of the cutting stability. In the case of chattering, the unstable situation is the main focus of investigation.
The focus is on the recognition of chatter ("chatter detection") and the avoidance of chatter. For that purpose, work is being done on process and machine models that use modern data processing (artificial intelligence, neural networks) to extract information on process stability from online measurement and control data of the machine tool.
The fly cutting process is important for precision & ultraprecision machining, where a single, usually monocrystalline cutting edge leaves an extremely precise and reflective surface. Also relevant is High Speed Cutting (HSC), in which the cutting speeds are approximately 10 times higher than at conventional cutting. Other cutting methods are High Performance Cutting (HPC), in which high material removal rates are the main focus, and High Feed Cutting (HFC), in which high feed speeds at low cutting depths are important. HSC technologies also allow hard materials to be machined with defined cutting edges.