In this study, a useful indirect cutting force measurement method using an acceleration sensor and current hall sensors is proposed. A series of experiments was performed on a precise micro machining stage with a high-speed spindle. A three-axis acceleration sensor was installed on the spindle head, and current hall sensors were connected to the motor current inlet cables. From the results obtained, the correlations of the tool teeth rotation and current amplitude showed a linearity of 92.0% precision for hall sensor signals, and 98.0% precision for acceleration sensor signals. Even though the results using the acceleration sensor showed better linearity than those of the current hall sensors, the signals can be easily affected by chattering, spindle vibration, and other external disturbances. From this perspective, the current hall sensor can provide more robust results.

Yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics have been utilized as a restorative dental material. Presintered Y-TZP ceramics are machined using the Computer-Aided Design and Computer-Aided Manufacturing (CAD/CAM) techniques. In this study, pre-sintered 3 mol % yttria-stabilized zirconia (3Y-TZP) bioceramics reinforced with Al 2 O 3 particles were prepared by sintering at relatively low temperature. The machining characteristics of the developed 3Y-TZP composites were investigated using an end-milling process. A series of experiments were performed on a high speed spindle with several sensors: a tool dynamometer, an acceleration sensor, and an acoustic emission sensor. The tool dynamometer was installed below the work-piece, a three-axis acceleration sensor was installed on the spindle head, and the acoustic emission sensor was installed on the fixture. The machining characteristics of the composites material were evaluated in a high speed machining process under various cutting conditions by changing the cutting speed, depth-of-cut, and feedrate. The machined surface was investigated using SEM photographs.

Recently, with increasing demand for precise micro-components productions, the importance of micro machining processes is increasing in many fields, including the automotive, aerospace engineering, medical instruments and computer industries. However, compared with macro machining processes, it is very difficult to observe the machining process due to its low MRR (material removal rate), very small tool size, high speed spindle, and low sensor signals levels, etc. Micro tool dynamometer can be a solution for this; however, its applications are limited due to the expense, sensitivity, robustness, and workpiece size. Thus, in the present study, a useful indirect cutting force measurement method involving an acceleration sensor and current hall sensor is proposed. A series of experiments were performed on a precise micro machining stage. Measured signals were analyzed in the frequency domain after FFT (Fast Fourier Transform), and the results were compared with the cutting force components measured via the acceleration sensor and current hall sensor, respectively. From the results, it could be verified that the proposed indirect cutting force measurement method is a useful way to monitor the micro end-milling processes. Finally, to predict the cutting forces in micromilling processes, the modified polynomial neural network (PNN) and the back-propagation neural network are compared.

Recently, micro square pyramid patterns which can be obtained by a light diffusion effect have been widely studied and examined. However, micro pyramid patterns are difficult to fabricate, because of a deburring problem. Therefore, a micro machining technology for the fabrication of micro pyramid patterns has emerged as an essential element. Burr can almost be generated on the edge of the micro pattern when the micro square pyramid pattern is manufactured by a mechanical cutting process. The micro pyramid pattern shape is difficult to maintain as an original form when the burrs are removed. So various methods have been used in an attempt to remove the burrs. A micro magnetorheological (MR) fluid jet polishing process is one of various methods to remove burrs. The process can control shear force for material removing it by a controlled viscosity of the MR fluid due to magnetic-field adjusting. In this paper, magnetic analysis and the deburring process were carried out to fabricate a micro square pyramid pattern on brass (non-magnetic material) and nickel (ferromagnetic material) using a micro MR fluid jet polishing system. Finally, the deburring characteristics and the shape analysis of micro pyramid patterns were investigated by using a micro MR fluid jet polishing system.

AlN-hBN ceramic composites with 3 mass% CaF2 were fabricated by spark plasma sintering at 1800°C for 10 min. The effects of hBN content on mechanical properties, microstructure, and machinability of AlN-hBN composites were investigated. With increasing hBN content, relative density, flexural strength, and Young's modulus decreased, whereas fracture toughness increased slightly. Vickers' indentation cracks are largely deflected near hBN platelets, implying a weak interfacial bond between the AlN and the hBN. The fracture surfaces of AlN-hBN composites showed a higher tendency of intergranular fracture than monolithic AlN. During end-milling processes, the cutting resistance decreased with hBN content, demonstrating the machinability of AlN ceramic can be improved significantly by the addition of hBN.