以制品几何精度为目标的塑料挤出模具优化设计方法

Optimization Design Method of Plastic Extrusion Die for Product Geometric Accuracy

对于壁厚不均的复杂塑料异型材挤出模具的设计,口模出口处的流动平衡是必要条件,但并不充分,挤出制品仍存在由于挤出胀大各向异性所引起的挤出形变。针对上述问题,建立以制品几何精度来评价挤出胀大各向异性行为的数学模型,并据此建立几何精度优化设计目标函数和约束条件。以挤出口模出口流动平衡和挤出制品的几何精度为目标,提出高精度挤出模具优化设计方法。以Benchmark模型为例,采用响应面法,依次完成基于流动平衡和基于几何精度的挤出模具优化设计,得到了挤出模具流道的几何精度最优解。与Benchmark案例相比,几何精度优化设计最优解的尺寸精度系数下降了98.2%。结果表明,高精度挤出模具设计方法充分结合了流动平衡优化设计方法的高效率和几何精度优化设计方法的高精度,在实现口模出口流动平衡的基础上,显著提高了挤出制品的几何精度。

For the design of complex plastic profile extrusion die with uneven wall thickness,the flow balance at the die exit is a necessary condition,but not sufficient.Due to the anisotropic behavior of extrudate swell,the extrudate still has a certain degree of deformation.Therefore,a mathematical model is established to evaluate the anisotropic behavior based on the geometric accuracy of products,and objective functions and constraints of geometric accuracy optimization design are established.Aiming at the flow balance at the die exit and the geometric accuracy of the extrudate,a high-precision optimization design method of the extrusion die is proposed.Taking the benchmark model as an example,an optimal solution of geometric accuracy of extrusion die channel is obtained.Compared with the benchmark case,the dimension accuracy coefficient of the optimal solution is reduced by 98.2%.The results show that high precision extrusion die design method fully combines high efficiency of the flow balance method and high precision of the geometric precision method.Based on the flow balance at die exit,the geometric precision of the extrusion product is significantly improved.