Optimal Design And Error Analysis Of 3-PUU Parallel Bending Forming Mechanism

The purpose of this paper is to provide an in-depth analysis and study of the errors in the 3-PUU parallel pipe bender.At present,based on the motion characteristics of the parallel mechanism,a principle has been proposed to achieve accurate forming of pipes in one complex axis,and corresponding equipment has been developed.However,in practical applications,these devices still have many errors,resulting in large errors in tube bending and forming.For this reason,this paper will analyze and study the geometric errors of 3-PUU parallel bending machine in detail and propose an error compensation scheme to improve the forming accuracy of 3-PUU parallel bending machine.Firstly,in order to improve the motion performance and working accuracy of the parallel bending mechanism,this paper analyzes the influence of the force transfer capability of the bending mechanism on the tube bending capacity,and selects the better structure size with the force transfer performance of the parallel mechanism as the optimization index.After the structure size is determined,suitable forming parameters are selected according to the size of driving force,and the optimal range of forming parameters in the quality space is determined,thus improving the accuracy of pipe bending and forming.Secondly,the structure and working principle of the parallel bending machine are thoroughly studied and analyzed in this paper,and the mathematical model of the contact angle error of the pipe and the bending die and the geometric error of the parallel mechanism are established,and the simulation is verified by using mathematical software and 3D modeling software.At the same time,the error sources with the greatest influence on the position of the parallel mechanism are identified through the sensitivity analysis of the geometric errors to provide reference for the mechanism design.Finally,the strategy to compensate the contact angle error of the tube and bending die and the geometric error of the parallel mechanism is proposed,and the correctness of the error model and error compensation strategy is verified using finite element simulation.The simulation results show that the forming accuracy is improved from 35.5745% to6.9342% after the error compensation,which significantly reduces the error of tube bending and forming.In addition,this paper also investigates the problems related to the stress distribution and deformation of the pipe during the bending process by using the finite element simulation software.