Machining of hard special materials

The development of innovative materials and material applications requires the application of new or adapted production techniques. The Institute for Welding Technology and Cutting Manufacturing Processes at Clausthal University of Technology is dedicated to material-related research and university teaching of manufacturing processes in welding technology and cutting manufacturing. The extensive offer to students and industry is supplemented and completed by teaching and research tasks in the related fields of production engineering, industrial management, quality management and wear research. In addition to basic research in numerous DFG-funded projects, ISAF's application-oriented research in AIF-funded projects and industrial assignments is oriented towards current issues in industrial companies.

One of ISAF's main research areas in the field of machining is the hard machining of components made of modern high-performance materials such as technical ceramics, graphite, glass and aramid fibre composites using the innovative ultrasonic lapping process. In ultrasonic vibratory lapping, loose lapping agent grain, generally boron carbide dispersed in water, is used as a tool on which a mould tool vibrating in the ultrasonic range acts, Fig. 1. Microscopic eruption of the finest particles occurs and the negative contour of the mould tool is reproduced exactly in the workpiece. With its process variants of profile countersinking, drilling and ultrasonic milling, ultrasonic vibration lapping is very flexible with regard to component complexity and opens up new possibilities for shaping hard machining. Three-dimensional, complex structures, slots and bores can be produced. For example, fine bores and webs with dimensions of less than 0.5 mm can be produced from semi-finished products with the highest precision and within the tightest manufacturing tolerances, Figure 2. But the process can also be used to optimize cutting tools, e.g. to reproduce three-dimensional surface models as chip grooves.

Ultrasonic vibratory lapping is being researched at ISAF with the aim of developing material- and task-adapted machining strategies for ceramic materials. The investigations form the basis for a reproducible finishing of ceramic components with defined component properties. For the production of complex component geometries, machining guidelines for multi-axis CNC machining and planetary erosion with rotating pin tools are developed.

In research projects in connection with industrial partners, feasibility studies are carried out for the material-compatible process design also for other, non-ceramic materials such as glass and composite materials. One project, for example, deals with the production of finest drillings and complex structures in glass substrates, as required in electronics and microsystems technology. Another research project is intended to provide the basic principles for the application of ultrasonic vibration lapping in the machining of hard metals after sintering.

In addition to the research activities, the following services are offered by ISAF in the field of ultrasonic technology:

• Single part and small series production as well as prototype construction in glass, technical and conventional ceramics, CFK, GFK, glass ceramics, natural stone
• Production of specimens for materials testing (bending and tensile specimens, TEM preparation etc.)
• Technology development and transfer