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Efficient Micromachining of Ceramic Materials in free formed, accurate and reliable shapes

Final Report Summary - MiCMa^3 (Efficient Micromachining of Ceramic Materials in free formed, accurate and reliable shapes)

Objectives

The MICMA3 project has the ambition to improve the current ceramics manufacturing process chain to respond flexibly and cost-effectively to the increasing demand of advanced and micro scale ceramics applications. The focus is on the investigation of alternative technologies, micro-EDM (Electrical Discharge Machining) and micro-HSM (High Speed Milling), for the efficient, reliable and flexible micromachining of ceramics in hard state.

Background

Thanks to the unique combination of exceptional high hardness, thermal and oxidation resistance, technical ceramics, like Si3N4, SiC, ZrO2, Al2O3 and composites, find extensive applications in modern industry. The traditional machining of ceramics is still, however, a labour- and cost-intensive procedure. A significant challenge concerns the small scale production of 3D complex components and micro sized features without defects and at acceptable cost. Diamond grinding is applied after sintering to accomplish superior surface quality and close tolerances, but weighing for more than 70 % upon the final cost of the single component. Densification steps may also introduce micro-defects which lead to risk of failure of the materials during service.

Foreground

Micro-EDM
EDM is a competitive method for the machining of ultra hard materials and micro components. With the addition of an electrically conductive secondary phase into the insulating ceramic matrix, it also proves to be an attractive method for the processing of ceramics. The focus here was the investigation of the EDM capabilities in ceramics machining at micro scale. Both commercial and own developed electrically conductive ceramics, including ZrO2-TiN, Al3O2-TiCN and TiB2 were considered during investigation. Experiments were conducted on a SARIX SX-100-HPM micro-EDM milling centre, and suitable roughing and finishing process strategies were developed for all these materials. Highly competitive results were obtained; especially, the ZrO2-TiN composite showed machining rates up to 0.3 mm3/min and surface quality down to 0.18 um Ra at medium-high and low discharge energy conditions, respectively. The type of material removal mechanisms was also studied. Based on the developed technologies, several demonstrators were realised, including micro moulds, micro extrusion dies and air bearing components. Feature accuracies within 5 um were obtained.

Micro-HSM
HSM and diamond coating of tools have been recently introduced as key technologies for the efficient and cost effectively machining of various kinds of abrasive materials and composites, such as graphite, ceramic powder and carbon fibre reinforced alloys. Thanks to exceptional high hardness and wear resistance of diamond, machining opportunities also rapidly increases. The focus here was to investigate the feasible machining of fully sintered ceramics by means of micro-HSM tools. HSM is less expensive than diamond grinding and more versatile. Experiments were conducted on a KERN MMP 2522 micro-milling centre. Wet and dry machining conditions were both considered during investigation. Highly competitive results were obtained; especially, optical surface qualities, with Ra below 20 nm, were achieved on a fully sintered ZrO2 ceramic block at a cutting speed of 120 m/min. The effect and the mechanisms of tool wear were also analysed. A dedicate tool solution is being developed.

The results display high potential for the development of a combined EDM-HSM manufacturing process chain for the accurate and flexible micromachining of electrically conductive ceramics. HSM of ceramics also provides the potential for a stand alone and versatile solution for the finishing of pre-shaped fully sintered ceramics as well as for the machining and micro structuring of ceramic surfaces.

Contacts: eleonora.ferraris@mech.kuleuven.be; dominiek.reynaerts@mech.kuleuven.be
Web site: http://www.mech.kuleuven.be/micro/