Laser chemical machining, a non-conventional processing method based on thermally activated electrochemical material dissolution, represents a promising technology for manufacturing metallic dies for micro forming applications. Prior to widespread industrial acceptance the machining quality of laser chemical machining should be characterized. For this purpose, laser chemical machining is compared with micro milling regarding both the dimensional accuracy and the surface quality. Therefore, square micro cavities exhibiting side walls between 100 μm and 400 μm in length and 60 μm in depth are machined with both manufacturing processes into the cobalt-chrome alloy Stellite 21. The geometrical features are investigated using laser-scanning confocal microscopy and scanning electron microscopy. On the one hand, laser chemical machining is more suitable for manufacturing cavities with dimensions < 200 μm due to higher shape accuracy with stable mean edge radii of (11.2 ± 1.3) μm as a result of roughing and finishing steps. On the other hand, the finish quality of micro milling with mean surface roughness Sa of 0.2 μm could not be achieved with laser chemical machining due to in-process induced waviness. Finally, the metallographic analysis of the surface-near layers reveals that both manufacturing processes ensure gentle machining without any noticeable micro structural impact.

Micro milling is a flexible technique for the production of micro mechanical components like dies and moulds and process control is the key to reach the strong production requirements. Requirements, given by engineers and designers, are addressed mainly to the functional performance of the produced part, therfore topographic features are most decisive. Surface parameters, mainly of statistical origin, have been used for a long time in surface characterisation and process monitoring. Furthermore, it is known that these parameters correlate with the desired functional behaviour, but this knowledge is usually not used for a deterministic process design, uneconomic try and error approaches are still common.Mathematical investigations can use the full process flexibility for an in-process functionalization by selecting optimal conditions and process parameters with respect to a set of relevant surface parameters. In this study, micro ball-end milling is investigated and process parameters in order meet a predefined bearing ratio curve as accurately as possible are identified. Therefore, a mechanistic surface generation model has been developed and is used as a forward model for an iterative optimisation. Static and dynamic process geometry and a micro mechanical material removal operator are the main features of the model. In the first part of the paper the semi-empirical model is calibrated for certain tool and workpiece materials. In the second part optimal feed speed and width of cut are determined. Finally, an experimental validation is presented and the comparison of the predefined, the predicted and the experimental bearing ratio curves shows a good agreement.

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Abstract. In order to meet the requirements of micro rotary swaging, the local properties of the tools should be adjusted properly with respect to abrasive and adhesive wear, compressive strength, and toughness. These properties can be optimally combined by using different materials in specific regions of the tools, with a gradual transition in between to reduce critical stresses at the interface during heat treatment and in the rotary swaging process. In this study, a newly developed co-spray forming process was used to produce graded tool materials in the form of a flat product. The graded deposits were subsequently hot rolled and heat treated to achieve an optimal microstructure and advanced properties. Micro plunge rotary swaging tools with fine geometrical structures were machined from the hot rolled materials. The new forming tools were successfully applied in the micro plunge rotary swaging of wires of stainless steel.

Micro systems technology is one of the key enabling technologies of the 21st century [Hes03], with increasing relevance due to a general trend towards miniaturisation in many industries. The main boosters for this trend are currently the consumer and communication electronics market and-to a lesser extent-medical technology (especially microfluidic devices, which had a market volume of approx. $2.5B in 2017 [Cle17]). As an example, for the companies organized in the industry association