变阻流区厚度的T型模具流道设计方法  

Design method for flow channel in T die with variant thickness of chock zone

作　　者：麻向军 MA Xiangjun(The Key Laboratory of Polymer Processing Engineering of the Ministry of Education,National Engineering Research Center of Novel Equipment for Polymer Processing,South China University of Technology,510640 Guangzhou,China)

机构地区：[1]华南理工大学聚合物成型加工工程教育部重点实验室,聚合物新型成型装备国家工程研究中心,广州510640

出　　处：《应用力学学报》2022年第4期791-796,共6页Chinese Journal of Applied Mechanics

基　　金：国家重点研发计划项目(No.2019YFB1704900)。

摘　　要：热塑性塑料片材或流涎膜常用T型模具挤出成型,采用等歧管半径和等阻流区厚度的流道结构时,通常采用增加歧管半径或减小阻流区厚度的方法提高熔体出口流率沿流道宽度方向的均匀性,前者有利于降低挤出压力,但熔体停留时间显著增加,而后者有利于降低熔体停留时间,但挤出压力急剧增大。基于对流道中熔体流动的分析,采用沿流道宽度方向减小歧管半径的结构减小熔体停留时间,沿流道宽度方向增加阻流区厚度的结构降低挤出压力,在满足沿流道宽度方向熔体出口流率均匀的条件下,利用流变学理论推导了阻流区厚度沿流道宽度方向变化的微分方程,对该方程进行数值求解并拟合可得到阻流区厚度。与等歧管半径和等阻流区厚度的流道相比,变歧管半径和变阻流区厚度的流道可以显著降低挤出压力和熔体停留时间。同时,通过对歧管尺寸和形状的设计,在不显著增加挤出压力的情况下能够显著降低熔体停留时间,而通过阻流区长度和厚度的设计,在不增加熔体停留时间的情况下调整挤出压力以适应不同的成型要求。T die is usually used to manufacture the sheet or casting film of thermoplastics.In order to improve the thickness uniformity of product manufactured using T die with constant radius manifold and constant thickness choke zone,increasing the radius of the manifold or decreasing the thickness of the choke zone was usually adopted to improve melt exit flow rate.However,a larger manifold diameter would prolong the melt residence time although it is beneficial to decreasing extrusion pressure,while a thinner chock zone would increase the extrusion pressure although it is beneficial to shortening the melt residence time.A new structure of flow channel with decreasing radius of manifold and increasing thickness of choke zone along the width of flow channel is proposed in this paper to shorten the melt residence time and reduce the extrusion pressure based on the analysis of melt flow characteristics in flow channel.Under the condition of uniform melt exit flow rate along the width of the flow channel,the differential equation of thickness of chock zone is deduced based on rheology,which can be solved by numerical method and fitted in design.Compared with flow channel with constant radius manifold and constant thickness choke zone,the proposed flow channel with thickness-varying chock zone and radius-varying manifold is beneficial to decrease the extrusion pressure and shorten the melt residence time significantly.Using the proposed flow channel in T die design,the melt residence time can be shortened further without increasing extrusion pressure significantly by the dimension and shape design of manifold,while the extrusion pressure can be adjusted to meet extrusion requirement without increasing melt residence time by the length and thickness design of choke zone.

关 键 词：变阻流区厚度 变歧管半径 熔体出口流率 挤出压力 熔体停留时间 流变学 

分 类 号：TG76[金属学及工艺—刀具与模具]