【作者】 李吉泉；

【导师】 李德群； 郭志英；

【作者基本信息】 上海交通大学 ， 材料加工工程， 2008， 博士

【摘要】 塑料注射成形是成形塑料制品的重要方法之一,也是材料加工学科的一个重要组成部分。注射成形过程中影响制品质量及其稳定性的因素很多,不合理的设计会导致严重的产品缺陷,材料、工艺等因素的波动则会引起制品质量的不稳定,甚至导致废品的出现。在各种波动条件下,以提高产品质量稳健性为目标,综合考虑质量和成本的稳健设计方法,已成为目前塑料注射成形的重要前沿课题之一。本文首先对各种稳健设计方法进行讨论,重点阐述了设计过程涵盖系统设计、参数设计和容差设计三个阶段的三次设计。在塑料注射成形工艺过程和功能分析的基础上,建立了多层次注射成形工艺功能模型,并着重对多层次的注射制品质量进行了讨论。并以该多层次模型为基础,结合具体产品的质量要求,建立了制品的质量-成本评价目标,为参数设计和容差设计提供了目标和约束。用数值模拟软件数据库中的材料特性数据来近似材料特性参数波动情况,并采用Plackett-Burman设计方法,分析了材料特性参数对注射成形工艺性能的影响,明确影响注射成形过程的显著因素,将其作为三次设计中材料特性的噪声因素进行三次设计。在材料特性单独波动、工艺单独波动的情况下,分别采用内外表直积法对影响制品翘曲变形的重要工艺参数进行了参数设计,使其在保证较小制品变形的基础上,制品的尺寸特性较为稳定。然后在材料特性和工艺同时波动的情况下,采用综合噪声因素法对重要工艺因素进行了参数设计。为了进一步提高注射制品尺寸的稳定性,进行了材料特性噪声因素和工艺噪声因素的容差设计。通过正交试验进行各噪声因素之间交互作用的验证和显著因素的分析,明确了容差设计的主要对象。通过模拟试验分析了主要噪声因素对制品尺寸的影响情况,在此基础上进行了容差的调整。两个实际产品的讨论和应用表明,注射成形工艺三次设计显著提高了注射产品质量的稳健性。其中,系统设计的研究成果可直接应用于注射成形工艺的评价和设计;参数设计使制品质量较好,并能获得较为稳定制品质量的注射成形工艺;容差设计使制品质量的稳定性进一步得到了提高。在参数设计过程中还研究了塑料特性对注射成形工艺性能的影响,获得了影响注射成形工艺性能的显著材料特性参数,这些显著特性参数可为注射成形工艺设计提供参考。在容差设计过程中发现材料特性中的PVT参数b2s是影响制品尺寸稳定性最显著的噪声因素,通过调整其容差可较明显地提高制品尺寸的稳定性,应当是尺寸精度要求较高的场合中重点考查和控制的材料特性参数。通过上述注射成形三次设计的讨论和应用,说明了稳健设计方法在注射成形工艺中的应用和意义。通过三次设计,注射成形工艺能获得较好质量特性的制品,并且制品质量特性在生产过程中具有良好的稳定性。本文的过程与方法可为注射成形中各种优化设计和稳健设计方法的应用提供参考,其思路和结果也可为注射成形的质量工程应用提供依据。更多还原

【Abstract】 Plastic injection molding is a key polymer processing technique to transform granules into various plastic parts. It is also one of the most important disciplines of material process engineering. There are many factors affecting the quality of injection molded products, and unreasonable design parameters would lead to serious product defects. In the factors affecting injection molding, material properties fluctuations, process fluctuations and other noise factors will lead to fluctuations in the product qualities, even lead to the emergence of waster products. Considering quality and cost with fluctuations in a variety of conditions, robust design has become one of the leading subjects in plastic injection molding to improve the stability of product qualities.Because of the important status and great role of three stage design in robust design methods, three stage design was chosen in this paper to improve product quality, which includes three design stages: system design, parameter design, and tolerance design. Based on the function discussion of injection molding, it was proposed that the multi-level quality-cost design model of injection molded product, whose focus was multi-level product qualities for injection molding. The product evaluations were established with specific product quality requirements based on the multi-level quality-cost design model. They would provide objectives and constraints for the following robust design.In the noise factors of injection molding, the material properties fluctuations were approximated by the property parameters’distributions of series materials in the database of numerical simulation software. Before fluctuations study, it was necessary to construct the materials based on the materials property distributing to analyze the technical property, and Plackett-Burman Design was introduced to reduce experiment times. The study of technical property provided significant material noise factors for three stage design, and provided the leading material properties for the choosing of material and process drawing of injection molding. The direct product of inner-outer array was applied to improve the dimension stability with small warpage in the parameter design of significant process variables, considering the material properties fluctuations and process fluctuations respectively. While, an integrated noise factor method was introduced in the parameter design of controllable factors under the comprehensive fluctuations of material properties and process.After the system design and parameter design, tolerance design with material properties fluctuations and process fluctuations were introduced to further improve the dimension stability of injection molded products. The interaction between the noise factors and significance of noise factors were analyzed by orthogonal test to determine the target of tolerance design. The tolerances of significant noise factors were adjusted according to the affection of the noise factors on product dimension.Discussion and application on two products showed that the three stage design would observably improve robustness of injection molded product quality. In the three stage design of injection molding, the result of system design would be applied to evaluation and design of injection molding, parameter design had got good process conditions with better quality and quality robustness, and tolerance design improved the quality robustness further. During the parameter design, the study on material technical properties proposed significant material properties for plastic injection molding, which providing information for design of injection molding process. During the tolerance design, it was detected that the PVT parameters b2s was the most significant noise factors for dimension robustness of injection-molded products, and the dimension robustness was improved by tolerance adjustment of b2s. This noise factor should be the key material property parameter to test and control in the precision injection molding.By the discussion and application of three stage design in injection molding, this paper studied the application and signification of robust design in injection molding. The injection molding process with robust design will introduce better quality of the products and stability of processing. The process and methods of this paper provide reference for optimizations and robust designs of injection molding, and the ideas and conclusions provided theoretical basis for quality management of injection-molded products.更多还原