Study On Optimization Design Of Clamping Mechanism For All-electric Injection Molding Machine

A clamping mechanism is the key mechanical structure to ensure mold achieving reliable on-off movement. The clamping mechanism of all-electric injection molding machine takes the servo motor as power source to make the movement of the moving platen more high-speed, stable and accurate. So all-electric injection molding machine is often applied in precision parts production and other high-end injection molding engineering field.This paper takes the clamping mechanism of all-electric injection molding machine as the research object. According to the given basic parameters and movement, this paper gives the design and analysis of movement characteristics for the clamping mechanism. Combined with the finite element technology and the modern optimization algorithms, we complete the statics analysis of moving platen, front platen, pull-rods and front platen structure optimization. The main contents of research are as follows:(1) The design and optimization of clamping mechanism. This paper studies on the regular types of clamping mechanism. Then, taking the electrical toggle type connecting rod clamping mechanism as the research object, we analyze the clamping motion characteristics and mechanical properties based on its sketches and main technical parameters. According to the the original data and the relationships among parameters, we get the basic design and 3D model of clamping mechanism, conduct kinematics analysis with ADAMS on the model and get the result that clamping mechanism accords with the movement of slow-fast-slow performance fundamentally. Then, we select the maximum of the force amplification(M), the minimum of the structure’s length(L) and the maximum of the stroke’s ratio (Ms) as the optimization goal to build the optimal model of clamping mechanism. Finally, the optimization design is carried out on the clamping mechanism by using the fmincon function in MATLAB to obtain good performance of clamping mechanism.(2) The Finite element analysis of key components of the clamping mechanism. The statics analysis is carried out on the moving platen with Workbench finite element software and it determines the design scheme of the relative small-mass and deformation-uniformity template upon the structure improvement. The statics analysis and the structural parameters optimization of equal mass model is also carried out on the front platen through Workbench & Pro/E. And it reduces the stress concentration and deformation of the template. Besides, we analyze the mechanical characteristics of the Pull-rods and study the stress of the screw thread and the screw thread section under different nut by FEM. The result shows that the threaded force is mainly concentrated on the first 3 threads and the screw thread segment using suspended nut fastening allocates the stress distribution to the other threads, which makes the threaded force is more uniform as a whole and decreases the maximum stress by 9.86%. Accordingly, it verifies the effectiveness of the suspension nut on preventing pull-rods thread fracture.(3) The topology optimization of the front platen. Based on the analysis of statics of front platen, the topology optimization is carried out with Workbench. It proposes a modification scheme of the front platen according to the pseudo-density images. After the static analysis of the modified model, the result shows that the mass reduces by 4.5% and the deformation reduces by 13.5% after the topology optimization, which declines the consumable platen materials effectively, improves the platen stiffness.(4) The multi-objective optimization of structural parameters of the front platen. By the static analysis and the topology optimization results, It establishes the multi-objective optimization model of the front platen on the basis of the height(P2), the reinforced bottom depth(P3) and the outside diameter of convex sets of platen center(P4) with the optimized aim of the minimum of front platen’s mass and deformation. The optimization for the front platen is studied by the Direct Optimization components of Workbench and the MATLAB programming method based on neural network and the algorithm NSGA-II. Finally, we get the optimum solution for Pareto of the front platen under the constraint condition. After the optimization, the mass and deformation of the front platen have been reduced accordingly. It is concluded that the optimization result of the front platen based on MATLAB is superior to the result from Workbench.This topic has completed the design of clamping mechanism based on the provided parameters of the clamping mechanism of all-electric injection molding machine. The optimization is also accomplished for athletic performance of entire motion mechanism and important parts. Finally, this paper achieves the expected design requirements and the ideas as well as the methods of the research also have some reference for other machinery’s design research.