Classified Optimization Strategy Of Weld Line Of Multi-hole Plastic Products Based On Simulation

Weld line is the major factor restricting the quality of multi-hole plastic parts.Plenty of research has been devoted to improving the quality of weld line.However,few papers have distinguished the weld line from the formation mechanism.In order to improve the quality of weld line fundamentally,this paper has established the targeted optimization strategy of for two main categories of weld line respectively,cold and hot weld line,according to their different formation mechanism and diverse influencing factors.The two optimization strategies are optimization of cold weld line based on gate size adjusting and valve gate timing,and optimization of hot weld line by multi-objective optimization of process parameters,respectively.The main research is developed as follows:Firstly,the quantitative evaluation system of weld line based on Simulation platform was achieved.In order to quantitatively characterize the fusion quality of weld line based on Simulation platform,the influences of melt fusion temperature and confluence angle on the fusion quality of weld line were taken into account from the analysis of the formation mechanism of weld line.A quantitative evaluation system of weld line based on Simulation Platform was established by combining temperature at flow front and confluence angle.The validity of the evaluation system was verified by the following optimization strategy.This research provides guidance for standardization of the evaluation system of weld line based on simulation platform.Secondly,the optimization strategy of cold weld line was established based on gate size adjusting and valve gate timing.Aiming at the position control of cold weld line,a method to realize the small-range position control of cold weld line by controlling gate size,based on determining the feasibility by limit method and optimizing by experiment design,was established,and a method to realize the random position control of cold weld line through valve gate timing optimization by means of approximation speed matching method and o optimizing by experiment design was also developed,which effectively improves the efficiency of the position optimization of cold weld line.Aiming at the elimination of cold weld line,a more accurate criterion for judging the delay time of valve gate was determined,then the elimination of cold weld line was realized based on this criterion.Furthermore,the optimization strategy of hot weld line based on multi-objective optimization of process parameters was developed.In order to achieve the rapid and effective optimization of the process parameters,a multi-objective optimization method was established,which combining Latin Hypercube Sampling(LHS),Kriging method,Back Propagation Neural Network(BPNN),Non-dominated Sorting Genetic Algorithm(NSGA-II)and Technique for Order Preference by Similarity to Ideal Solution(TOPSIS).Firstly,LHS was used to arrange the experiments.Secondly,in order to establish a high-precision surrogate model which can accurately map the relationship between process parameters and optimization objectives,BPNN and Kriging surrogate model were established respectively,and the evaluation strategy of surrogate model accuracy was put forward.The prediction accuracy of the two surrogate models were fully compared by the two-step method including overall accuracy testing and single factor analysis testing.Then the Kriging model with a higher accuracy was determined as the final surrogate model.Finally,the Pareto frontier optimal solution of the process parameters was determined by combining NSGA-II and TOPSIS algorithm.Finally,the example of multi-hole panel forming was applied to verify the effectiveness of the proposed classified optimization strategy of weld line.The simulation and production experiments both show that the quantitative evaluation system of weld line based on simulation platform established in this paper can effectively measure the fusion quality of weld line.At the same time,the proposed classified optimization strategy of weld line can effectively realize the optimization of weld line and promotion of molding quality of multi-hole panel.It can be extended to the optimization of weld ling of multi-hole plastics parts of the same kind.