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ZrO2 ceramic has a wide range of applications, such as in the thermal barrier coating (TBC) of turbine blades, micro actuators, and gas sensors. However, this material is challenging to machine due to its high hardness and brittleness. Although spark assisted chemical engraving (SACE) can be used to machine ZrO2 ceramics, the traditional SACE models for glass are difficult to apply to ZrO2 ceramics since the melting point of ZrO2 is much higher than that of glass. A theoretical basis for applying the SACE process to ZrO2 ceramics is still lacking, which makes applying the SACE process to machine micro cavities with high surface quality in ZrO2 ceramics very challenging. This paper proposes an energy action model based on the processing voltage, pulse width and machining gap by analyzing the energy transfer process of SACE. The energy model expresses difference in the spark energy between physical removal and chemical removal. Through machining experiments, the contact effect of the SACE process on ZrO2 ceramics was found, and the reasons why the SACE process is sensitive to the machining gap were clarified. Furthermore, physical and chemical removal process models with or without the discharge constraint onto the end of the tool electrode were established. Using the above theoretical models, a circular ring microcavity without micro cracks on the surface was achieved in a ZrO2 ceramic workpiece by using the SACE process with the regulating energy effect trending to the chemical removal. Additionally, considering the contact effect and the process models applied in the SACE scanning process of ZrO2 ceramics, a tool electrode with a spring structure was employed to solve the bending problem of the micro tool electrode. As a result, a square micro-cavity with high surface quality was machined successfully.

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Microstructures determine flow properties of microfluidic chip. Micromold forming is an effective method to realize mass manufacturing of microfluidic chips. This requires to machine some kind of special microstructure of high surface quality on a metal/alloy workpiece. Micro V-shaped grooves are the typical microstructures of the chip micromolds used for controlling microfluid or weld packaging. In this research, a scanning micro-electrochemical machining (ECM) process of V-shaped grooves is proposed using a tool electrode fabricated by micro–electrical discharge machining (EDM) on-machine. Theoretical and experimental research was conducted for achieving the V-shaped grooves with a given angle on die steel. A long-distance V-shaped groove with the given angle of 67 deg and the depth of 125 μm was successfully machined.

Although nickel-titanium (NiTi) alloys have many excellent material properties, micro structures of NiTi alloys are rarely machined by conventional mechanical machining due to its high elasticity and severe tool wear. A micro tube as an active catheter with typical driving structures made from a NiTi shape memory alloy (SMA) is a key part in an interventional micro robot system. The driving structures, as complex 3D micro structures pierced through the thin-walled micro tube, are mainly fabricated by a lithography-based process at present. However, not only is the process inefficient and costly, but its etching depth is also limited. In this research, a novel process of 3D servo scanning micro electro discharge machining (EDM) with the movement of two-axis linkage and one-axis servo is proposed for efficiently machining 3D micro structures. The processing procedures are presented, including 3D model design, scanning paths planning, 3D NC codes generation and 3D micro EDM. The emphasis is focused on the methods for planning the scanning paths and generating the CNC codes considering the special 3D micro structures. By using the planned complementary scanning paths, the processing stability is improved for successfully machining the typical driving structures within 5 h. The machining experiments verify the feasibility of the proposed process and related methods.