Fault Analysis Of Reaction Injection Molding System And Design And Analysis Of Floating Die-shelf

Reactive injection molding system is widely used because its products are light in weight and thin in wall.The die-shelf in this system has important technical and economic significance for product quality and production cycle,especially its reliability and precision of allocation and alignment are particularly important.This paper established the fault tree of reactive injection molding system,and then studied the precision of allocation and alignment of the die-shelf.The main research contents and results are as follows.（1）The fault tree of reactive injection molding system was established,and the qualitative analysis of the fault tree was carried out.On the basis of understanding the working principle and process of the reaction injection molding system,the reaction injection molding system is divided into injection system,mold frame system,temperature control system,hydraulic transmission system and electrical control system.The fault tree of mechanical structure and the fault tree of hydraulic system is established.The qualitative analysis of the fault tree shows that the reliability and precision of allocation and alignment of the die-shelf seriously affect the life of the mold and the forming quality of the product.It also shows the weaknesses of the flat-opening hydraulic die-shelf are the guide mechanism and the synchronous mechanism.（2）A design scheme of floating die-shelf was proposed.In order to improve the precision of allocation and alignment of the die-shelf,the floating mechanism is first used to increase the degree of freedom of the template-A in the floating die-shelf,then the guide mechanism is used to reduce the degree of freedom of template-A in the floating die-shelf.The floating die-shelf is a spring damping flexible mechanism.The floating die-shelf is composed of floating platform,spring mechanism,tripping sleeve and guide mechanism.The floating die-shelf has the advantages of no impact,no friction and long service life.In addition,the structure of floating mechanism and guide mechanism in floating die-shelf was analyzed.（3）The mechanical simulation model of the floating die-shelf was established,and the contact force of the 60-degree taper guide mechanism of the floating die-shelf during the working process was analyzed.ADAMS is used to simulate and analyze the floating die-shelf.The three-dimensional model of the floating die-shelf is simplified,the material properties,the connection pairs,the driving force and the load are set.The driving force of the template-A and the contact force of the guide mechanism under different deviation conditions are simulated and analyzed.The results show that the driving force of template-A increases with the increase of deviation distance and angle.Under the condition that the template-A deviates the same distance from Y axis and Z axis,the driving force under the condition that the template-A deviates from Z axis is lower than the driving force under the condition that the template-A deviates from Y axis.When the floating die-shelf deviates in both Y-axis and Z-axis,the offset in the Z-axis decreases to 0 at first.More than 48%of the contact force of the guide mechanism is distributed in the direction of movement of the template-A（X axis）.With the movement of the template-A,the contact force of the guide mechanism increases first and then decreases to 0 in the Y-axis and z-axis.（4）The influence of spring stiffness on the driving force of the template-A was analyzed.According to the established mechanical simulation model,the influence of spring stiffness K₁（Y-axis）and spring stiffness K₂（Z-axis）on the driving force of the template-A was analyzed.The results show that the driving force of the template-A increases with the increase of K₁ under the condition of the same Y axis deviation distance.Under the condition of the same Z-axis deviation distance,the driving force of template-A increases with the increase of K₂.Under the condition that template-A is offset by 6mm from template-B in Y axis,when K₁=50N/mm,the driving force of template-A is 1280.6N,when K₁=500N/mm,the driving force of template-A is 14180.4N.Under the condition that template-A is offset by 6mm from template-B in Z axis,when K₂=50N/mm,the driving force of template-A is 639.8N,when K₂=500N/mm,the driving force of template-A is 5633.0N.When the compression distance is fixed,the maximum contact force that spring can provide will decrease with the decrease of spring stiffness.Therefore,the appropriate spring stiffness should be selected for the floating mechanism.（5）The effective plane movement range of the 60-degree taper guide mechanism of the floating die-shelf was analysed.Five variables are used to describe the position and attitude of the template-A.The five variables are the displacement of Y-axis,the displacement of Z-axis,the rotation angle of X-axis,the rotation angle of Y-axis,the rotation angle of Z-axis.When the projection of the end faces of the two guide cones on the template-A on the YZ plane is respectively within the projection of the two guide cones on the template-B on the YZ plane,the floating die-shelf can clamp.The effective plane movement range of the 60-degree taper guide mechanism of the floating die-shelf is studied when template-A is not rotated and rotated.When the template-A is rotated,the effective plane movement range is unevenly distributed around the origin.As the rotation angle of the template-A increases,the effective plane movement range of the floating die-shelf decreases.