| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 89 === In this study, a discharge location detection system is designed and implemented based on the principle of discharge location detection. All the practical problems encountered, including EMI prevention, electrical circuit noises reduction and system calibration, are also discussed.
With the use of this system, the research is divided into three parts.
The first part is to estimate the workpiece''s shape and height by using the discharge location detection method. The method used in the past for estimating the workpiece''s height is rather complex and its validity is limited only to certain working conditions. In contrast, the method developed in this study can estimate the workpiece''s shape and height on line in a relatively simple way. The time for every estimation is only 0.03 sec, and the estimation error is within 2mm. It is much better than other methods.
The second part is focused on wire breakage problem from a viewpoint of discharge location concentration. Experiments are conducted with bad water flushing and over feed-rate in order to explore the gap situation before wire breakage. It is found that the breakage of wire is attributed to heavy thermal load caused by discharge location concentration and high abnormal ratio.
The third part is to investigate the relationship between the distribution of discharge location and the characteristic of WEDM. The result of the experiment shows that, when the distribution of discharge is not uniform, it is likely to have a workpiece with less vertical straightness of machined part. Besides, this study also discusses the influence of feed-rate, discharge off time, and water pressure over the distribution of discharge location. The higher feed-rate or the smaller discharge off time will make the distribution of discharge location more uniform. Also, the smaller the lower water pressure is, the larger the discharge numbers in the lower location will be.
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