M. Deuchert

Limits and challenges of manufacturing micro moulds

Due to the ongoing miniaturisation in industrial sectors like automotive, electronics or medical, the development of new manufacturing processes which are suitable for micro system technologies gains more and more importance. The miniaturisation of components leads to challenges in the manufacturing of micro parts. One application area is the manufacturing of moulds for the micro powder injection moulding (μPIM) process. This process requires good surface qualities and a sufficient demoulding behaviour of the moulds. Micro milling, micro electrical discharge machining (μEDM) and micro laser beam machining (μLBM) are appropriate processes for the manufacturing of micro structures in different materials. Abrasive micro peening can be used for further precision treatment. Depending on the desired structure a single process or the combination of several processes has to be chosen to obtain superior surface qualities of the moulds. This paper deals with challenges and limits of the manufacturing processes among others exemplified on a gearwheel mould.

Investigation of the Surface Characteristics for the Micro-Cutting Process with Finite Element Simulation

As the service life of components is significantly influenced by the surface layer properties, namely surface roughness, surface work hardening and residual stresses, these are the focus of many investigations. As these properties can be measured experimentally in many cases only after finish of the process, simulation models can be used to explain the final process results by the interpretation of the development of the result quantities during the loading and unloading state. The developed and validated simulation model and the extended process knowledge can be used afterwards to predict process parameter combinations with optimal process results for other cutting tool-workpiece combinations without performing large and costly experimental investigations. In the present study, the dependences of surface work hardening and residual stresses on process parameters of micro-cutting, namely cutting depth, cutting velocity and cutting edge radius are investigated by 2D finite element simulations using ABAQUS/Standard. The material behaviour of normalized AISI 1045 is described in dependence of strain, strain rate, and temperature. Chip formation is modelled by continued remeshing of the work piece. The simulation results are validated by the comparison with experimentally determined integral width and residual stress depth profiles, using x-ray diffraction method. The influence of the ploughing process, characterized by the ratio of cutting edge radius to cutting depth, on surface characteristics is well described by the simulation model.

Burr Minimization and Removal by Micro Milling Strategies or Micro Peening Processes

Micro milled mold inserts made from hardened and tempered steel can have burrs in the size order of 50 μm at the edges. These burrs often prevent the easy demolding of green bodies from micro powder injection molds. Further surface treatments on the molds are necessary to improve surface quality thus facilitating demolding processes. In the present study, three different processes: micro milling, abrasive micro peening and ultrasonic wet peening, have been investigated for their suitability as viable solutions for reducing or eliminating burrs. The tool used for the micro milling process is capable of removing existing burrs but creates new burrs which are inherent to the tool movement over the machined surface. While abrasive micro peening leads to a reduction of burrs on the mold surface, the material below the impacted surface is plastically deformed. Ultrasonic wet peening showed the best effectiveness at removal of burrs of a wide variety of complex geometries in a short processing time and without plastic deformation of the edge zones.