Multi-point Supporting Fixture Design And Location Layout Optimization For Thin-walled Parts Cutting

Thin-walled parts are widely used in aerospace industry,which have the characteristics of high strength and light weight.The aerospace parts are mostly curved thin-walled parts,because of its large size and low stiffness.It trends to deform and flutter during the machining processing.The deformation and flutter greatly affect the quality and accuracy of the workpiece.Therefore,it is necessary to study and design a fixture for the thin-walled workpiece cutting to satisfy the quality requirements.In terms of the tendency of spacecraft intensive launch,the production pattern of thin-walled parts is characterized by single-piece,small batch and customization.Therefore,it is necessary to study the flexible fixture that adapts to the variation of characteristic parameters of thin-walled parts in a certain range.This paper focus on studying the fixture design for the thin-walled arc plate.The fixture structure design,location layout optimization and machining vibration suppression analysis are studied through theoretical analysis,finite element simulation,test verification and evolutionary algorithm.The main research contents are as follows:A multi-point supporting fixture was designed to support and locate the thin-walled arc plate with the various characteristic parameters.Based on the analysis of the cutting performance and the location principle of thin-walled parts,a clamping constraint model was established.And the multi-point supporting fixture structure for cutting thin-walled parts was designed with the reconfigurable structure and the selected critical parts.The fixture entity was manufactured and the multi-point clamping fuction is achieved through vacuum adsorption force.The designed fixture can enhance the rigidity,improve the machining stability,and meet the clamping requirements of thin-walled workpiece with different sizes.A multi-objective optimization method of fixture location for thin-walled arc plate was proposed,which combines improved BP neural network with multi-objective genetic algorithm.On the basis of "N-2-1" location principle,the location coordinates of the location points were defined as design variables,and the clamping deformation and vibration displacement were defined as the targets of location layout optimization.Latin hypercube sampling method was preferred to select the candidate location points.The sample data wass collected by calculating the clamping deformation and the main vibration mode displacement of the thin-walled workpiece with the help of finite element method.Through introducing particle swarm optimization algorithm to improve the neural network,a high-precision agent model for the nonlinear relationship between design variables and target was established.Then the optimal location layout scheme was obtained by multi-objective genetic algorithm,which ensured the effectiveness and efficiency of location layout optimization.The vibration reduction analysis of thin-walled parts machining based on multi-point supporting fixture was completed.Considering the effort of the location point,the vibration reduction of cutting process was studied based on the designed multi-point supporting fixture.First,the principle of vibration reduction is analyzed.Consequently,the feasibility of improving machining stability by increasing stiffness and damping is confirmed.The effect of the number and layout of locating points on the cutting vibration characteristics is confirmed by modal testing.Also,it is verified that the designed fixture and the optimized location layout can effectively restrain the machining vibration.