Dynamic Analysis Of Box Feeding Mechanism Of Pharmaceutical Packaging Machine For Joints With Clearance

The actioncan be basically completed according to the motion track of the initial design.when the box feeding mechanism of the pharmaceutical packaging machine is running at a low speed,However,when running at a high speed,there will be situations in which the boxis detached from the suction cup,the transmission position is inaccurate,and some parts are worn out and deteriorated.The difference between the joints clearance and the type of joints has an important nonlinear effect on the system.Clearances existing in joints are inevitable,and the type of joints sometimes difficult to change under certain conditions.The paper takes the feeding mechanism of the pharmaceutical packaging machine as the research object,studies the description,dynamic response and contact force model of the joints with clearance.The following is the main research contents in this paper:The mathematical model of the revolution joint and the translation joint is established when considering the clearance.The separation and contact state are described by the vector method,and the position,the distance,relative speed and force between the two potential contact points are obtained.The mathematical description method of cam groove joint is presented,determine the location of the two potential contact points,The expressions of distance,relative velocity and force between the two potential contact points are derived,and the discriminant condition for three different states are established.Combined with the FEM,the contact examples are numerically calculated in the elastic range,The mathematical expressions of the time-varying contact stiffness of the revolute joint with clearance are derived,and the applicability of three pure elastic contact models is studied: Persson force model compared with the Hertz and the improved Winklercontact model,it is more suitable for the revolute joint with clearance,The Hertz contact model is more suitable for the translation and cam groove joint with clearance.The revolute,translation and cam groove joints in the box feeding mechanism of the pharmaceutical packaging machine were simulated under the working conditions of different clearance size,rotation speed.The results show that the translation and cam groove joints with clearance have a great influence on the angular velocity and angular acceleration of suction cup,and revolute joint with clearance mainly affects the angular acceleration and has randomness.Aiming at the imperfection of the calculation precision of Impact function in Adams,based on the Hunt-Crossley energy dissipative contact force model,combined with the energy method and the dynamic equation,the expression of the maximum deformation is derived,a new viscous damping factor is obtained,and an improved normal contact force model is proposed: For this model and several common normal contact force models of the same type,the relationship between contact force,relative velocity and deformation under different recovery coefficients is studied.Verified that the improved normal contact force model not only ensuring correctness but also have the accuracy and scope of application.