Error Analysis And Clamping Force Optimazation Of Fixture System In Flexible Engine Production Line

The "flexible" fixture switching system is one of the key technologies for the fully automated flexible production line of automotive engines.How to design a CNC flexible fixture switching system that meets the mixed production tasks of different components has become the primary problem of this research.Since,the "flexible" fixture increases the risk of lowering the clamping accuracy,this paper research the fixture system from three aspects: fixture system structure,fixture system positioning error and deformation displacement error caused by multiple clamping forces.Firstly,investigates on the key technologies of flexible production of automobile engine parts are carried,coming with the importance and the tendency of flexible fixture system.Then,the overall scheme of fixture switching system is designed,including based on the autonomous laser guided AGV as the vehicle,the rapid switching system using image visual positioning and the hydraulic fixture using KOSMEK zero-point positioning system.Secondly,the strength analysis and finite element modal analysis of the fixture system are carried out for the four different loads,and the key components are optimized.After the improvement,verify that the indicators meet the design requirements.Thirdly,based on the kinematics principle,the integrated static positioning error model of the fixture containing the zero-point positioning system is established.The Monte Carlo method is used to simulate the distribution of the workpiece positioning pose error,which is compared with the traditional “maximum minimum method” calculation result.The prediction result is more accuracy.Then,the sensitivity of the workpiece pose error component to each error source is analyzed,which provides a theoretical basis for the tolerance distribution of each positioning component of the fixture.Fourth,the displacement L2 norm and the minimum total residual energy are minimized as the objective function,and the multiple clamping force is used as the optimization variable and the static balance of the workpiece as the constraint condition to establish Multi-clamp force multiobjective optimization model;using the dichotomy method for optimization calculation,respectively compared with the initial value,the optimization percentages of the six clamping forces are 85.24%,85.24%,38.48%,58.09%,50.63%,31.28%.In addition,the minimum residual energy and the minimum displacement L2 norm are respectively optimized by 95.90% and85.24%.Finally,the validity of the model calculation is verified by the static error experiment of the fixture.The experimental analysis of the deformation of the workpiece under different clamping force combinations is carried out,and the necessity of determining the optimal clamping force is obtained.Then,using the fixed measuring point and changing the tapping point method,the vibration characteristics of the clamping system in the direction of the main shaft are tested on the machine turning table,and the natural frequency of the Z-direction deformation displacement is 109.38 Hz.Compared with the finite element calculation result,the second order of the system When the natural frequency is 74.786 Hz,the Z-direction oscillates and provides theoretical support for the processing frequency planning.