Interactive robust optimal design of plastic injection products with minimum weldlines

A new robust optimal design methodology has been developed and applied to the design of plastic injection molding products. Taguchi’s robust design method and an optimal design search algorithm are integrated with a commercial CAE simulation tool. A direct search-based optimization procedure is implemented with the considerations of process variations as well as uncontrollable noise variables. The Interactive Design Space Reduction Method (IDSRM) based on orthogonal arrays for design of experiments is developed as a general optimization tool. Using the system, designers can interactively adjust the design space during the searching process for the optimal solution based on the outcomes of the experiments. The developed methodology is applied to an industrial application: a molding process design of an automobile front bumper to minimize the weldline, a form defect of plastic parts. Compared with the initial design solution, the optimized design aided by the proposed methodology shows a more efficient and better result in terms of design robustness against process variations.     

Robust design of multiple dynamic quality characteristics

The Taguchi method is a useful technique to improve the performance of products or processes at a lower cost and in less time. The traditional Taguchi method focused on a single characteristic to optimize the parameter conditions. In practice, most products and processes have more than one quality characteristic. Several approaches dealing with multiple static quality characteristic problems have been reported. However, little attention has been focused on optimizing the multiple dynamic quality characteristics. This research presents an approach to optimizing multiple dynamic problems based on quality loss. The objective is to minimize the total average quality loss for the multiple dynamic quality characteristics experiment.     

Optimisation of Multiple Quality Characteristics Based on Percentage Reduction of Taguchi’s Quality Loss

The traditional Taguchi method was focused on ensuring good performance at the parameter design stage with one quality characteristic, but most products and processes have multiple quality characteristics. The optimal parameter design minimises the total quality loss for multiple quality characteristics. Sev-eral studies have presented approaches addressing multiple quality characteristics. Most of these papers were concerned with maximising the parameter combination of SN ratios. This paper presents an approach for multiple quality characteristics based on the percentage reduction of quality loss. A multiple regression is employed to fit the function of percentage reduction of quality loss and to optimise the parameter design with multiple quality characteristics using mathematical programming. The results reveal the advantages of this approach are that the optimal parameter design is the same as the traditional Taguchi method for the single quality characteristic; the optimal design maximises the amount of reduction of total quality loss for multiple quality characteristics. ID="A1" Correspondance and offprint requests to: F.-C. Wu, Department of Industrial Management, Van-Nung Institute of Technology, 1 Van-Nung Road, Chung-Li, Taiwan 320, ROC. E-mail: shogo@cc.vit.edu.tw     

Die fatigue life design and assessment via CAE simulation

In die design process, the design and prediction of die fatigue life is a non-trivial issue. Many factors in die life cycle from design, fabrication to service all affect die life. The die life in cold forging processes is basically determined by die fatigue failure. The design and assessment of die fatigue life needs to consider all the affecting factors including die structure and component design, materials selection and properties configuration, die fabrication and service conditions. Currently, there is no efficient approach to providing complete solutions by considering all of these factors. CAE simulation technology, however, presents a promising approach to addressing the issue. In this paper, a simulation-based approach for die life design and assessment is presented. The approach employs both stress-life and strain-life fatigue analysis methods to conduct the die fatigue life design and analysis based on the stress and strain revealed by CAE simulation. As the die stress and strain in forming process vary dynamically, the integrated simulation of forming process and die deformation is conducted in such a way that the dynamic die stress and strain can be identified and determined. To implement this idea, a realization framework is orchestrated and the processes and procedure under the framework are succinctly articulated. The implementation with case studies is finally used to test and verify the validity, robustness, and efficiency of the developed approach. The approach is proven to be able to provide satisfactory solutions for die life design and assessment in the early stage of die design.     

Optimising robust design for correlated quality characteristics

Many industries have employed the Taguchi method over the years to improve product and process performance. This method is powerful and effective in helping manufacturers to design their products and processes as well as to solve troublesome quality problems. Several studies have presented approaches to multiple quality characteristics. Few published articles have focused primarily on optimising the correlated multiple quality characteristics. This research presents an approach to optimising the correlated multiple quality characteristics using principal component analysis and grey relational analysis based on quality loss. As can be seen in the results, the advantage of this approach is that the chosen optimal design for multiple quality characteristics is robust for the correlated multiple quality characteristics. This method finds the optimal parameter conditions more easily, even when the average quality losses of the quality characteristics are all diverse.     

基于田口稳健性设计的多品种小批量生产工序质量改进

首先应用动态特性的田口稳健性设计理论,对多品种小批量生产工序的输出响应值与输入值建模分析,估计出模型参数以及信噪比评价指标,找出影响输出响应值的因素。并通过试验设计与分析,找到最佳可控因素水平组合,使输出响应值对于噪声因素不敏感,而对输入值很敏感,最终使得对于不同的生产品种以及对于投入的新品种,过程的输出响应值均达到稳健的目的,从而大大提高过程质量。最后应用电子束表面硬化案例进行了仿真分析。     

Process quality improvement of a qualitative response with dynamic characteristic

To achieve quality improvement in manufacturing environments, the design of experiment (DOE) and Taguchi methods are two efficiency approaches to address such problems. Applying those methods to resolve quality improvement frequently focuses on the measurable quality response (or quantitative response). However, the complexity of products or processes is gradually increased and due to the limitation of measuring equipment, the quality response could not be directly measured. Visual inspection or measurement is then used to judge the quality for nonmeasurable response (or qualitative response). Basically, for assessing the quality of a qualitative response, it is initially divided into several classes or ordered categories. As for customers’ requirements gradually changing and applications’ flexibility gradually increasing, a dynamic structure for this process will be another important consideration for manufacturers. That is, it causes the work of quality improvement to be dynamically analyzed. Dr. Taguchi had proposed a dynamic method to analyze such issues. However, only several studies focused on quality improvement of a qualitative response during the static characteristic. Parameter optimization approaches were seldom proposed to address quality improvement of a qualitative response with the dynamic characteristic. Therefore, in this study, we proposed an integrated parameter-optimization approach to resolve quality improvement of a qualitative response with dynamic characteristics. An illustrative example, quality improvement of lead twist during the stamping process for lead frame manufacturing at Science-based park in Taiwan, is employed to demonstrate the effectiveness of the proposed approach.     

基于有限元法和Taguchi方法的移动硬盘耐撞性能稳健设计

运用Taguchi参数设计方法,提出了基于数值模拟的移动硬盘跌落冲击耐撞性能稳健设计方法。以6.3cm(2.5in)移动硬盘为研究对象,建立了基于有限元软件ANSYS/LS-DYNA的移动硬盘跌落冲击三维有限元模型。分析了关键结构参数对移动硬盘耐撞性能稳健性的影响,进行了移动硬盘耐撞性能稳健设计,获得使磁盘盘片接触面等效应力对地面硬度变化具有稳健性的最优参数水平组合,并进行了仿真试验验证分析。该方法为改进设计提高移动硬盘耐撞性能提供了理论依据。     

Optimising the thermoforming process of polymeric foams: an approach by using the Taguchi method and the utility concept

The use of the conventional Taguchi method for determining the optimum setting of controllable factors through off-line experiments focuses on products with a single quality characteristic or response. However, most products have several qualitative characteristics or responses of interest. The Taguchi method in itself optimises a single response or performance characteristic, yielding a set of process parameters. This particular setting, however, may not give the desired results for other characteristics of the product. There is a need to obtain a single optimum setting of process parameters that can be used to produce products with optimum or near optimum quality characteristics as a whole. Multi-characteristic response optimisation may be the solution to the above problem. In this report, a case study on thermoforming polypropylene foams, utilising a simplified multi-criterion methodology based on Taguchis approach and utility concept, is discussed. Key processing factors affecting product quality are identified. It has been shown that the proposed Taguchi approach with the utility concept can provide an appropriate solution to yield a satisfactory product quality for a multi-response process optimisation problem.     

Multi-objective optimization of injection molding process parameters in two stages for multiple quality characteristics and energy efficiency using Taguchi method and NSGA-II

In this paper, the parameters optimization of plastic injection molding (PIM) process was obtained in systematic optimization methodologies by two stages. In the first stage, the parameters, such as melt temperature, injection velocity, packing pressure, packing time, and cooling time, were selected by simulation method in widely range. The simulation experiment was performed under Taguchi method, and the quality characteristics (product length and warpage) of PIM process were obtained by the computer aided engineering (CAE) method. Then, the Taguchi method was utilized for the simulation experiments and data analysis, followed by the S/N ratio method and ANOVA, which were used to identify the most significant process parameters for the initial optimal combinations. Therefore, the range of these parameters can be narrowed for the second stage by this analysis. The Taguchi orthogonal array table was also arranged in the second stage. And, the Taguchi method was utilized for the experiments and data analysis. The experimental data formed the basis for the RSM analysis via the multi regression models and combined with NSGS-II to determine the optimal process parameter combinations in compliance with multi-objective product quality characteristics and energy efficiency. The confirmation results show that the proposed model not only enhances the stability in the injection molding process, including the quality in product length deviation, but also reduces the product weight and energy consuming in the PIM process. It is an emerging trend that the multi-objective optimization of product length deviation and warpage, product weight, and energy efficiency should be emphasized for green manufacturing.     

Robust parameter design and multi-objective optimization of laser beam cutting for aluminium alloy sheet

The application of laser beam for precise cutting of sheet metals, in general, and reflective sheet metals, like aluminium, in particular, has become of interest in the recent past. The optimum choice of the cutting parameters is essential for the economic and efficient cutting of difficult to cut materials with laser beams. In this paper, a robust design and quality optimization tool called the Taguchi methodology has been applied to find the optimal cutting parameters for cutting of a reflective sheet made of aluminium alloy with a Nd:YAG laser beam. All the steps of the Taguchi method, such as a selection of orthogonal array, computation of signal-to-noise ratio, decision of optimum setting of parameters, and the analysis of variance (ANOVA), have been done by a self-developed software called computer aided robust parameter design (CARPD). A considerable improvement in the kerf taper (KT) and material removal rate (MRR) has been found by using Taguchi method-based predicted results. Confirmatory experimental results have shown good agreement with predicted results. Further, the Taguchi quality loss function has also been used for multi-objective optimization of laser beam cutting of Al-alloy sheet. The results of multi-objective optimization are compared with the single-objective optimization and it has been found that the kerf taper was increased by 1.60% in multi-objective optimization while the MRR was same in both cases.     

鼠标外壳注塑件翘曲变形模拟分析

基于CAE数值分析技术和田口实验方法,研究了保压压力、熔体温度、冷却时间、保压时间和模具温度等因素对翘曲变形的影响.以翘曲变形量最小为目标,通过正交试验方法获得了最佳参数组合以及最佳参数组合条件下的翘曲变形量.结果显示,通过模流分析来预报产品缺陷,优化工艺参数,可以缩短模具开发周期,降低成本,提高企业竞争力.     

A Robust Tolerance Design Method Based on Fuzzy Quality Loss

The traditional tolerance design model ignores the impact of noise factor, so that the design may be infeasible due to variations in design constraints. Based on the analysis of fuzzy factors in tolerance design and the limitations of the traditional Taguchi squared quality loss function, a fuzzy quality loss function model utilizing fuzzy theory was introduced. Concepts on fuzzy quality loss and fuzzy quality loss cost were proposed in the model. The characteristics of the new model and the advantages over the traditional Taguchi quality loss function were analyzed. A robust tolerance design model using a fuzzy quality loss function was proposed. An example was given to illustrate the proposed model. Results and comparisons show that the method is suitable and reliable, and makes the conclusions more objective and reasonable. This work was translated from the Journal of Zhejiang University (Engineering Science), 2004, 38(5) (in Chinese) This project is supported by the National Natural Science Foundation of China (no. 50275136) and the National Key Laboratory Project (no. 51489020104JW0401)     

汽车CAE软件系统的应用研究

论述了汽车 CAE软件系统的功能 ,对 HB670 1轻型客车进行了动力性计算和验证及传动系参数优选 ,对HB6790型客车进行了有限元分析和可靠性行驶试验 ,应用表明 ,该软件实现了初始方案到优化设计的计算机模拟 ,进而缩短产品的生产周期 ,减少实验次数 ,提高产品质量     

Quality management research by considering multi-response problems in the Taguchi method – a review

Off-line quality control is considered to be an effective approach to improve product quality at a relatively low cost. The Taguchi method is one of the conventional approaches for this purpose. Through this approach, engineers can determine a feasible combination of design parameters such that the variability of a product’s response can be reduced and the mean is close to the desired target. Most previous applications of the Taguchi method only emphasize single-response problems, while the multi-response problems have received relatively little attention. However, several correlated quality characteristics of a product are usually considered for product quality by a consumer. Though a lot of research is being done on this subject, there is ample scope for applying quality by design concepts, especially when dealing with multi-response variables. This paper presents a literature review on solving multi-response problems in the Taguchi method.     

基于田口方法的汽车悬架稳健性优化

针对悬架设计制造过程中存在不确定性因素而带来性能不稳定的问题,对某电动车麦弗逊悬架进行空间运动学分析,建立了求解悬架性能参数的数学模型,并通过试验验证了模型的合理性。利用该数学模型,采用田口稳健性设计方法,进行正交试验设计,对悬架跳动力学特性进行了多目标稳健性优化,将优化结果进行蒙特卡罗验证,结果表明,优化后的悬架性能及其稳健性均有了很大提高。     

覆盖件冲压仿真参数化建模方法

针对在覆盖件冲压成形领域对快速、自动化的有限元网格建模方法的迫切需求,提出一种快速的汽车覆盖件冲压仿真建模的思路与方法.将覆盖件冲压工艺设计与冲压成形仿真前处理集成,使用散乱三角面片模型,在自主开发的CAE前处理软件中,进行参数化的工艺补充面和压料面设计.模型的网格剖分与冲压工艺设计同时进行,自动生成整套模具的网格模型供冲压仿真计算.为了真实地模拟板料网格的流动,提出了参数化的真实拉深筋的模型建模方法和板料网格的预细分方法.完成了相关软件的开发.多个汽车覆盖件冲压工艺设计和冲压仿真计算实例说明了该方法的有效性.     

A sequentially integrated multi-criteria optimization approach applied to laser transmission weld quality enhancement—a case study

In the present research, a sequentially integrated optimization approach, based on Taguchi method, response surface methodology, and desirability function analysis, is proposed for evaluating the optimal set of laser transmission welding parameters. Two quality characteristics namely, weld strength and weld width, and three welding parameters namely laser power, welding speed, and focal position are selected for experimental work. Taguchi quality loss function is first used to find the optimum level of control factors. The outputs of Taguchi analysis is further used in central composite design for developing response surface models. Desirability function analysis is performed next using the developed response surface models, to evaluate the optimal parameters setting by considering multiple objectives. The weld quality is improved markedly at the optimal process condition, as verified by additional confirmation tests. The performance of the proposed optimization approach is also compared with the Taguchi method and grey–Taguchi method and found that the proposed optimization approach gives better results than the other two techniques.     

双回路全动力液压制动阀的稳健设计

根据系统原理建立了可用于制动阀稳健设计及其制动压力响应特性分析的动态数学模型,试验验证了仿真模型的正确性。在分析系统制动特性主要影响因素的基础上,确定了制动阀的设计变量及不确定因素。对制动阀进行的基于制动压力损失最小的稳健设计结果表明,合理选择设计参数可使加工精度降低、制动性能的稳健性提高。研制的制动阀经工业性应用证明,系统性能满足国家标准要求。     

Multi-response optimisation of thermosonic copper wire-bonding process with correlated responses

Multi-response optimisation has become an increasingly important issue in complex industrial processes, particularly in situations where more than one correlated responses must be assessed simultaneously. This study discusses the optimisation of a multi-response thermosonic copper wire-bonding process, used in the semiconductor assembly industry. Since nine process parameters were adopted as control factors for this experiment, the design of the experiment was based on the Taguchi method as per L ₁₂ orthogonal array. Three responses, assumed to be correlated, were considered for each experimental trial. In order to take into account correlations among responses, a specific method for analysis was used, drawing on multi-criterion methodology based on Taguchi’s quality loss function, principal component analysis and grey relational analysis. Finally, experimental confirmation was carried out to identify effectiveness of the method. It has been shown that the generic approach in the analysis for correlated responses provides better results than traditional method of analysis, in terms of optimal parameter design that meets the specifications of all three responses, for the observed process optimisation.