线切割机床工具电极的可靠性建模与评估

电火花线切割机床将金属丝作为切割工具,亦称工具电极,而断丝是线切割机床最频繁的故障模式.为提高加工过程的可靠性,进而提高生产效率,需要对工具进行可靠性建模与评估.将两次断丝故障之间的工作时长(即断丝间隔时间TBB,Time between Breakings)作为可靠性数据,并假设数据服从两参数Weibull分布;基于数据和最小二乘法,得到了Weibull分布参数估计值;进行假设检验.结果表明:两参数Weibull分布可用于工具电极的可靠性模型.结合实例,求出某电火花线切割机床的平均断丝间隔时间MTBB(Mean time between Breakings),并将其作为可靠性指标,基于该指标提出建议,以提高加工过程的可靠性.

Reliability Modeling and Evaluation of Tool Electrode for Wire Electrical Discharge Machine

A WEDM ( Wire Electrical Discharge Machine) takes metal wire as the cutting tool or tool electrode, of which the wire breaking is the most frequent failure mode. In order to improve the reliability of the cutting process and further the manufacturing efficiency,it is necessary to implement reliability modeling and assessment for the tool. First,the time between two wire breakings is taken as the reliability data,which is named TBB ( Time between Breakings) ,and the data is assumed to follow the two-parameter Weibull distribution;then,based on the data and the least squares method, the Weibull parameters are estimated;and finally, the hypothesis test is implemented. Results indicate that the two-parameter Weibull distribution is fit to the reliability model of the tool electrode. In combination with a real experiment, the MTBB ( Mean Time between Breakings ) of WEDM is obtained and taken as the reliability index, based on which corresponding advice is proposed to improve the reliability of the processing process.