Comparison between microfabrication technologies for metal tooling

This paper is based on the information gathered within the Multi-Material Micro-Manufacture (4M) Network activities in the Processing of Metals Division (Task 7.2 'Tooling') (www.4m-net.org). The aim of the task involves a systematic analysis of the partners' expertise in different microtechnologies for processing tooling inserts made of metal. The following technologies have been analysed: micromilling, micro-electrodischarge machining (EDM, including wire-EDM, sinking-EDM, and EDM-milling), laser micromachining, electroforming, and electrochemical milling (ECF) (an electrochemical machining innovative process proposed by HSG-IMAT). Considered tool-insert materials are nickel for electroforming, stainless steel for ECF, and tool steel (AISI H13) for all other processes. Typical features (ribs, channels, pins, and holes) required by micro-optics, microfluidics, and sensor and actuator applications have been selected to form the benchmark part and to carry out this analysis. The results provide a global comparison between the micromanufacturing processes mentioned earlier in terms of technical capabilities and cost effectiveness of different feature machinings. As a second result, the current limitations of these technologies concerning feature sizes, surface finish, aspect ratios, etc. have been identified. The main conclusion drawn is the absence of a consolidated technology to produce three-dimensional free-form shapes smaller than 100-200 mu m to date.