A new problem that classical statistical methods are incapable of solving is reliability modeling and assessment when multiple numerical control machine tools(NCMTs) reveal zero failures after a reliability test. Thus...A new problem that classical statistical methods are incapable of solving is reliability modeling and assessment when multiple numerical control machine tools(NCMTs) reveal zero failures after a reliability test. Thus, the zero-failure data form and corresponding Bayesian model are developed to solve the zero-failure problem of NCMTs, for which no previous suitable statistical model has been developed. An expert-judgment process that incorporates prior information is presented to solve the difficulty in obtaining reliable prior distributions of Weibull parameters. The equations for the posterior distribution of the parameter vector and the Markov chain Monte Carlo(MCMC) algorithm are derived to solve the difficulty of calculating high-dimensional integration and to obtain parameter estimators. The proposed method is applied to a real case; a corresponding programming code and trick are developed to implement an MCMC simulation in Win BUGS, and a mean time between failures(MTBF) of 1057.9 h is obtained. Given its ability to combine expert judgment, prior information, and data, the proposed reliability modeling and assessment method under the zero failure of NCMTs is validated.展开更多
High speed machining has received an important interest because it leads to an increase of productivity and a better workpiece surface quality. However, at high cutting speeds, the tool wear increases dramatically due...High speed machining has received an important interest because it leads to an increase of productivity and a better workpiece surface quality. However, at high cutting speeds, the tool wear increases dramatically due to the high temperature at the tool-workpiece interface. Tool wear impairs the surface finish and hence the tool life is reduced. That is why an important objective of metal cutting research has been the assessment of tool wear patterns and mechanisms. In this paper, wear performances of PCBN tool, ceramic tool, coated carbide tool and fine-grained carbide tool in high speed face milling were presented when cutting cast iron, 45# tempered carbon steel and 45# hardened carbon steel. Tool wear patterns were examined through a tool-making microscope. The research results showed that tool wear types differed in various matching of materials between cutting tool and workpiece. The dominant wear patterns observed were rake face wear, flank wear, chipping, fracture and breakage. The main wear mechanisms were mechanical friction, adhesion, diffusion and chemical wear promoted by cutting forces and high cutting temperature. Hence, the important considerations of high speed cutting tool materials are high heat-resistance and wear-resistance, chemical stability as well as resistance to failure of coatings. The research results will be great benefit to the design and the selection of tool materials and control of tool wear in high-speed machining processes.展开更多
制造设备间的广泛互联、互操作是制造领域实现广泛物联的重要前提.对数控系统进行实时监测,收集数控系统加工参数、刀具几何参数、零件质量检测等异构数据,进行有效地关联监控是目前研究的热点.基于OPC(object linking and embedding fo...制造设备间的广泛互联、互操作是制造领域实现广泛物联的重要前提.对数控系统进行实时监测,收集数控系统加工参数、刀具几何参数、零件质量检测等异构数据,进行有效地关联监控是目前研究的热点.基于OPC(object linking and embedding for process control)UA(unified architecture)连接数控系统,建立基于MTConnect的"适配器-代理(adapter-agent)"通用数控系统实时监控体系.研究实时监控数据模型、通信框架及其访问策略,给出了机床加工过程监控数据的标准数据模型.开发的原型系统在某航空薄壁件的实际加工过程进行实时监控,实现了加工过程数据、离线数据的综合可视化表达,验证了所提出的数控系统信息集成方法的有效性.该方法构建的数据模型清晰地表达了各加工要素,具有很好的可扩展性.展开更多
基金Project(2014ZX04014-011)supported by State Key Science&Technology Program of ChinaProject([2016]414)supported by the 13th Five-year Program of Education Department of Jilin Province,China
文摘A new problem that classical statistical methods are incapable of solving is reliability modeling and assessment when multiple numerical control machine tools(NCMTs) reveal zero failures after a reliability test. Thus, the zero-failure data form and corresponding Bayesian model are developed to solve the zero-failure problem of NCMTs, for which no previous suitable statistical model has been developed. An expert-judgment process that incorporates prior information is presented to solve the difficulty in obtaining reliable prior distributions of Weibull parameters. The equations for the posterior distribution of the parameter vector and the Markov chain Monte Carlo(MCMC) algorithm are derived to solve the difficulty of calculating high-dimensional integration and to obtain parameter estimators. The proposed method is applied to a real case; a corresponding programming code and trick are developed to implement an MCMC simulation in Win BUGS, and a mean time between failures(MTBF) of 1057.9 h is obtained. Given its ability to combine expert judgment, prior information, and data, the proposed reliability modeling and assessment method under the zero failure of NCMTs is validated.
文摘High speed machining has received an important interest because it leads to an increase of productivity and a better workpiece surface quality. However, at high cutting speeds, the tool wear increases dramatically due to the high temperature at the tool-workpiece interface. Tool wear impairs the surface finish and hence the tool life is reduced. That is why an important objective of metal cutting research has been the assessment of tool wear patterns and mechanisms. In this paper, wear performances of PCBN tool, ceramic tool, coated carbide tool and fine-grained carbide tool in high speed face milling were presented when cutting cast iron, 45# tempered carbon steel and 45# hardened carbon steel. Tool wear patterns were examined through a tool-making microscope. The research results showed that tool wear types differed in various matching of materials between cutting tool and workpiece. The dominant wear patterns observed were rake face wear, flank wear, chipping, fracture and breakage. The main wear mechanisms were mechanical friction, adhesion, diffusion and chemical wear promoted by cutting forces and high cutting temperature. Hence, the important considerations of high speed cutting tool materials are high heat-resistance and wear-resistance, chemical stability as well as resistance to failure of coatings. The research results will be great benefit to the design and the selection of tool materials and control of tool wear in high-speed machining processes.
文摘制造设备间的广泛互联、互操作是制造领域实现广泛物联的重要前提.对数控系统进行实时监测,收集数控系统加工参数、刀具几何参数、零件质量检测等异构数据,进行有效地关联监控是目前研究的热点.基于OPC(object linking and embedding for process control)UA(unified architecture)连接数控系统,建立基于MTConnect的"适配器-代理(adapter-agent)"通用数控系统实时监控体系.研究实时监控数据模型、通信框架及其访问策略,给出了机床加工过程监控数据的标准数据模型.开发的原型系统在某航空薄壁件的实际加工过程进行实时监控,实现了加工过程数据、离线数据的综合可视化表达,验证了所提出的数控系统信息集成方法的有效性.该方法构建的数据模型清晰地表达了各加工要素,具有很好的可扩展性.
