Micro-machining Of Pre-sintered Ceramic And Size Accuracy Control In Z Axis

Ceramic has many physical and chemical properties, such as high hardness, strength, resistance against corrosion and abrasion and due to those, It has been used widely in the field of MEMS. But machining the full-sintered ceramic in traditional mechanical ways causes severe tool wear and bad processing quality. Micro machining of pre-sintered ceramic is capable of overcoming those disadvantages and in the meantime, it leads to high-efficiency and low-cost machining process.When machining pre-sintered ceramic mechanically, tool wear occurs because of the interact force between tool and workpiece, in the meanwhile, micro machining machine tool has random positional error in some degree. These two aspects caused size error of the three-dimensional workpiece. In order to assure micro machining accuracy, this paper focused on the research on tool wear and positional error of machine tool, expressing infeasibility of the use of the material removal rate(MMR) to compensate tool wear in practical experimental condition, putting forward a way, changing tool path, to minimize radial height of tool wear, putting forward a way, periodical detect in machining process to compensate size error in Z axial, to improve machining precision of the three-dimensional micro ceramic workpiece.This paper analyzed that in mechanical layered milling process, the uneven stress on tool lateral side caused uneven tool wear. The Hr, height of radial tool wear caused by uneven tool wear, only can be decreased, not be totally extinguished.0degree and90degree tool path are used together by turn when the tool removed one layer material in order to wipe off remain material caused by processing copy. Experimental results showed that Hr can be reduced down to the machining layer value.The tool MMR was calculated in this three-step way:First, cavities of different volumes were manufactured with same machining parameters. Second, detect the actual depths of those cavities and the axial height of tool wear (Ha). Third, those two values were used and MMR was gained. But the calculated MMR from experiments data differed in a range of3%%to9%%. So the conclusion can be drawn that MMR was not useful in compensating the tool wear, at least in this experimental condition.The machine tool which was used in this micro machining process produced positional error in some degree. Detections with electro-balance and voltage proved the existence of positional error experimentally, plus or minus alternatively. So positional error can explain why the accurate Ha couldn’t be gained and it also played a role in size error in Z axial direction of micro ceramic structure, together with Ha.A new method was proposed to compensate size error in Z axial direction, which was periodical detection in machining process. The electro-balance was used to detect Z coordinates before and in the middle of machining process. Those coordinates were compared to compute D-values between them, which can also be called machining positional errors caused by Ha and machine tool positional error together. Then those D-values can be used to compensate the machining positional errors precisely.The detecting process was optimized. It was experimentally proved that when detecting, on the balance tray was better than on the pre-sintered ceramic body, with no rotation was better than with rotation, positioning error can be neglected which was caused by the distance between detecting point to machining position.LabVIEW program was compiled which was applied for controlling compensating machining progress automatically. Six working states were distributed, they were initialization, machining, positioning to detecting point, detect, position to machining point and termination.Comparative experiments were carried, and it can be proved with those experiments results that this new method can improve the accuracy of machining cavities’ depth, size errors were no more the2μm.