In heavy duty machine tools, hydrostatic turntable is often used as a means for providing rotational motion and supporting workpiece, so the accuracy of turntable is crucial for part machining. In order to analyze the...In heavy duty machine tools, hydrostatic turntable is often used as a means for providing rotational motion and supporting workpiece, so the accuracy of turntable is crucial for part machining. In order to analyze the influence of load-indcued errors on machining accuracy, an identification model of load-induced errors based on the deformation caused by applied load of hydrostatic turntable of computerized numerical control(CNC) gantry milling heavy machine is proposed. Based on multi-body system theory and screw theory, the space machining accuracy model of heavy duty machine tool is established with consideration of identified load-induced errors. And then, the influence of load-induced errors on space machining accuracy and the roundness error of a milled hole is analyzed. The analysis results show that load-induced errors have a big influence on the roundness error of machined hole, especially when the center of the milled hole is far from that of hydrostatic turntable.展开更多
The paper discussed cutter-work engagement situation hidden behind the mechanical and thermal load effect on cutting edges during high speed hard machining process. The engagement situation was investigated in great d...The paper discussed cutter-work engagement situation hidden behind the mechanical and thermal load effect on cutting edges during high speed hard machining process. The engagement situation was investigated in great detail using experimental and geometrical analytic measures. Experiments were conducted using A1TiN-coated micro-grain carbide end mill cutters to cut hardened die steel. On the basis, a general high speed hard machining strategy, which aimed at eliminating excessive engagement situation during high-speed machining （HSM） hard machining, was proposed. The strategy includes the procedures to identify prone-to-overload areas where excessive engagement situation occurs and then to create a reliable tool path, which has the effect of cutting load reduction to remove the prone-to-overload areas.展开更多
软件定义网络(Software Defined Network, SDN)是一种新型的网络体系架构,其原理是采用OpenFlow对网络结构进行自定义的扩展与管理。为进一步研究SDN架构的特性并实现网络负载均衡,文章基于Mininet仿真工具对SDN的网络负载均衡进行深入...软件定义网络(Software Defined Network, SDN)是一种新型的网络体系架构,其原理是采用OpenFlow对网络结构进行自定义的扩展与管理。为进一步研究SDN架构的特性并实现网络负载均衡,文章基于Mininet仿真工具对SDN的网络负载均衡进行深入研究,分析了OpenFlow协议技术及其原理,验证了SDN架构的功能和基本工作流程,构建了网络负载均衡仿真研究的实验环境,并在Mininet中进行了模拟实现,为进一步研究SDN架构提供了有效的技术支撑。展开更多
基金Projects(51575010,51575009)supported by the National Natural Science Foundations of ChinaProject(Z1511000003150138)supported by Beijing Nova Program,China
文摘In heavy duty machine tools, hydrostatic turntable is often used as a means for providing rotational motion and supporting workpiece, so the accuracy of turntable is crucial for part machining. In order to analyze the influence of load-indcued errors on machining accuracy, an identification model of load-induced errors based on the deformation caused by applied load of hydrostatic turntable of computerized numerical control(CNC) gantry milling heavy machine is proposed. Based on multi-body system theory and screw theory, the space machining accuracy model of heavy duty machine tool is established with consideration of identified load-induced errors. And then, the influence of load-induced errors on space machining accuracy and the roundness error of a milled hole is analyzed. The analysis results show that load-induced errors have a big influence on the roundness error of machined hole, especially when the center of the milled hole is far from that of hydrostatic turntable.
文摘The paper discussed cutter-work engagement situation hidden behind the mechanical and thermal load effect on cutting edges during high speed hard machining process. The engagement situation was investigated in great detail using experimental and geometrical analytic measures. Experiments were conducted using A1TiN-coated micro-grain carbide end mill cutters to cut hardened die steel. On the basis, a general high speed hard machining strategy, which aimed at eliminating excessive engagement situation during high-speed machining （HSM） hard machining, was proposed. The strategy includes the procedures to identify prone-to-overload areas where excessive engagement situation occurs and then to create a reliable tool path, which has the effect of cutting load reduction to remove the prone-to-overload areas.
文摘软件定义网络(Software Defined Network, SDN)是一种新型的网络体系架构,其原理是采用OpenFlow对网络结构进行自定义的扩展与管理。为进一步研究SDN架构的特性并实现网络负载均衡,文章基于Mininet仿真工具对SDN的网络负载均衡进行深入研究,分析了OpenFlow协议技术及其原理,验证了SDN架构的功能和基本工作流程,构建了网络负载均衡仿真研究的实验环境,并在Mininet中进行了模拟实现,为进一步研究SDN架构提供了有效的技术支撑。
