Research On New Process Of Combination Of Local Vacuum Forming And Extrusion Blow Molding

The process of extrusion blow molding has advantages of low production cost, strongadaptability and extrusion blow molding workpieces with a high degree of integrity. It iswidely used in the production of hollow container and industrial workpieces of complexshape. Extrusion blow molding workpieces have been uneven thickness, severely reducingthe quality and performance of the workpieces. It limits the using scope of the workpieces,and becomes a bottleneck restricting the development of extrusion blow molding.In this paper, the author analyzed a large number of industrial workpieces, anddesigned series study models with a flange of the same diameter of20mm and differentheights (10mm,15mm,20mm,25mm and30mm). The vacuum channels were located onthe blow mold. The vacuum forming is introduced into the process of extrusion blowmolding. Firstly, parison free deformation is slowly completed under the action of vacuumnegative pressure. Secondly, parison constrained deformation is quickly completed underthe combination of inflation pressure and vacuum negative pressure. The thicknessuniformity of the workpieces was optimized by reducing the speed of free deformation,extending the time of free deformation and increasing the amount of free deformation. Inthis paper, the new combination process of local vacuum forming and extrusion blowmolding is called new process of extrusion blow molding with local vacuum forming.The organic combination of POLYFLOW, Pro/E and AutoCAD used to simulate andanalyse the parison deformation process of inflation of the two processes. For theworkpiece with the same high flange, the simulation range and variance of wall thicknessby the new process is much smaller than the range and variance by the traditional process.The new process reduces the wall thickness distribution range, and improves the wallthickness uniformity significantly. In the simulation process, the best process parameterswere got by orthogonal experiment to guide the physical experiments. For the workpiecewith the same high flange, the variance of wall thickness by the new process is muchsmaller than the variance by the traditional process known from the experimental results.The new process significantly improves the wall thickness uniformity. On the basis ofsimulation and experiment, the optimum parameters for each model were given to guideindustrial production. The maximum height of20mm of flange was given to provide areference for the design of industrial workpieces. In this paper, workpieces design, CAE analysis, mold design and physicalexperiments was organically combined. From the simulations and experiments, thecombination of local vacuum forming and blow molding significantly improves theworkpieces thickness uniformity. The process of combination of local vacuum forming andblow molding is a low cost, practical method, highly feasible, and can significantlyimprove industrial workpieces wall thickness uniformity.