Research On Motion Characteristics Of Automatic Tool Changer

The automatic tool changer(ATC)is one of the most important functional parts in machining center,that cooperates with the tool magazine to assist the machining center to complete multiprocess tasks.During tool changing,the transmission mechanism of ATC needs to execute multiple start-stop movements according to the design requirements,and thus ATC becomes a multiple-fault component of the machining center.Compared with the hydraulic(gas-liquid)type ATC,the commonly used mechanical cam type one has a shorter change time but a more complicated transmission mechanism,and its motion characteristic is worth further exploring.In this paper,the motion characteristic of mechanical compound cam type ATC is taken as the research object.The main research contents are as follows:Firstly,the operation principle and mechanism constitution of the automatic tool changer are analyzed.On this basis,the motion cycle of the tool changing period is designed,and the cartesian coordinate motion cycle diagram is drawn.The motion law of cam and its followers are studied by dimensionless motion parameters to optimize the motion cycle,and the theoretical displacement curve of the device is obtained.Secondly,a qualitative analysis is performed on the compound cam,which is the core drive part of the device,especially the globoidal indexing cam,and the cam type is determined.On this basis,the contour curve equations of the compound cam are established.Combined with the geometric motion parameters of the cam and the previous research contents,the parametric modeling of the composite cam is completed by pro/E,and then the whole machine modeling of the composite cam ATC is completed.Finally,based on the Adams platform,the virtual prototype of the automatic tool changer is completed.Through the empirical and analytical methods,the contact collisions of the virtual prototype are analyzed in detail.In order to ensure the accuracy of the motion simulation,the chain transmission system is designed and introduced to improve virtual prototype by using the mechanical module of Adams.The virtual prototype simulation of ATC is achieved,and the motion characteristic curves of displacement,speed,acceleration are outputted.The simulation results,compared with the theoretical motion characteristic curves above,and the experimental detection curves by research group,are proved to be accurate.The research results provide reference for the revised design of ATC in machining centers.