Description and Investigation of Size Effects in the Scaling of a Hot Forging Process and a Milling Tool Into the Microscale

Abstract

From the general trend towards higher miniaturization and functional integration results an increasing demand for metallic parts of smallest dimensions (down to 100 μm). Industrial realization of these parts and the further breakthrough of products containing microparts require suitable production technologies with respect to accuracy, productivity, efficiency and reliability. This aspect is still a significant limitation. The problems which occur at the production of microparts with scaled, conventional processes will be expound by means of a process (microforging) and a microtool (micro diamond milling cutter). The application of metal forming technologies to the production of metallic microparts is limited by problems arising from size effects related to the small dimensions e.g. the influence of the microstructure becomes an important aspect to consider. An approach to these problems is the laser assistance of the microforming process. Laser light is used to increase the temperature of the material during forming, to increase the formability in the required area of the part and to reduce the flow stress and anisotropy of the material. To enable the transmitting of laser light into the workpiece, sapphire tools are used. Experimental investigations have shown that the use of sapphire tools in laser-assisted microforming processes is a suitable method for the production of microparts. Further investigations aim at modeling the material behavior and size effects in microforming processes and the integration of these models into FE simulations in order to extend its application to microproduction processes. The increasing requirements on form and surface qualities for milling tools used in micromanufacturing increasingly become more difficult to fulfill with conventional manufacturing processes. Alternative methods, for example Chemical Vapor Deposition (CVD) based procedures, could offer advantages. They do not only make smallest dimensions possible, but also allow the desired manufacturing tolerances of the tools to be met. As an example of a diamond growth process the development and testing of diamond side milling cutters for application in microtechnology are described [1, 2, 3, 4].