| Summary: | 碩士 === 國立臺灣師範大學 === 機電科技研究所 === 98 === Many side walls of micro holes and slots are not easily measured by current measuring instruments, such as: coordinate measuring machine, laser displacement meter, or high magnification toolmaker microscope. It is very difficult for overcoming the oxide layer on the workpiece and lighting in the deep hole of the workpiece. A non-contact micro measurement center combining automatic optical inspection (AOI), micro EDM with capacitance sensing is designed and developed to automatically, precisely measure the perpendicularity of micro slot-wall on the precision mould. The measurement center can on-machine makes various micro probes to rapidly provide for the needed stylus in measurement. The AOI acquires the image from the feature profile of workpiece by way of the developed machine vision and perform the image binary to determine the centric position for guiding the movement of the micro probe. Capacitance sensing, by which a signal with very low voltage and high frequency is employed, is used for precisely measuring the slot-wall. To ensure the measuring accuracy, a ‘four steps feed’ strategy of the probe is proposed. The measuring data are converted to digital data, and then transferred into frequency domain from time domain via fast Fourier transform (FFT) to regulate the feed of the probe and record the positions. Owing to non-contact measurement, the measurement will not be affected even if the oxide layer exists on the workpiece. The measuring accuracy which the probe is first calibrated via the gauge block of grade-0 can be maintained within the positional accuracy of the measurement center and the working time decreased. A geometrical accuracy of narrow slot on the IC lead frame is successfully measured which demonstrates the developed measurement center possesses very high feasibility. It is expected that the techniques of measurement center will significantly contribute to the precision machining industry.
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