Taguchi Quality Research Articles

Optimization Parameters of Femtosecond Laser Isolation Processing for a Microcrystalline Silicon Thin Film Solar Cell

This study explored the isolation process of a laser used to scribe the thin film layers of a microcrystalline silicon thin film solar cell. Using the Taguchi quality design, this study employed an L 18 orthogonal array to plan and implement an experiment for an isolation scribing process using a femtosecond laser. The isolation scribing materials included ZnO:Al, 500 nm–thick AZO transparent conductive thin film, 500 nm–thick microcrystalline silicon thin film with 38% crystallinity, and 300 nm–thick aluminum back-contact film. The results indicated that the fair processing quality characteristics included the minimum scribing line width, the flattest trough bottom, and the least number of surface bumps on the processing edge. The optimal single quality characteristic parameters of the Taguchi quality design were obtained using main effect analysis and the analysis of variance (ANOVA). The analytic hierarchy process (AHP) theory was applied to determine the optimal parameters for the multiple quality characteristics of the isolation scribing process. When the integrated isolation scribing line width of various layers was thinner, the area occupied on the solar cell was smaller, thus directly enhancing the photoelectric efficiency of the solar cell.

Design Methodology for the Minimization of Contact Width between Pressure Lip Seal and Shaft

In this research, a design methodology for minimizing the contact width between the pressure lip seal and the shaft was developed, by employing Taguchi quality engineering and statistical design of experiment method with CAE analysis. Instead of the real experimental measurements, the influential design parameters can be performed by simulation to save cost and time. A lip seal of 38 mm diameter was optimized, as a design case, according to the contact pressure response to the Mooney-Rivlin material properties and physical dimensions in different operation environments. The current methodology is shown to be an effective design tool for a pressure lip seal.

Robust Optimum Design of PIFA for RFID Mobile Dongle Applications

A novel planar inverted F-antenna (PIFA) structure for a dongle-type RFID reader module with a resonant frequency of 920 MHz is proposed using a robust optimum design process. In order to take into account the robustness against noise factors, the Taguchi quality method is complemented to the evolutionary strategy optimization method. The validity of the proposed design process is verified through a noise test and comparisons of the computation and the experiment results.

Economic production order quantity and quality

The purpose of this study is to integrate a conventional production-inventory management approach and a process-quality design approach so as to promote quality and reduce costs. Because the integration of these two approaches into a single system is conducted under the influence of a deterioration process, estimated costs of production must be modified. Only then can these various costs be presented as a total cost for the present integrated system. This total cost includes: a setup cost for production reordering and process resetting, quality-related costs stemming from the loss of product quality along with a tolerance-related production process cost and a failure cost for product defects, backorder costs for production shortage, carrying costs generated by the storing and handling of inventory, and material costs for determining the process mean. The Taguchi quality loss function is introduced to assess quality loss in the system. The decision variables include the initial setting (process mean), process tolerance, and production order quantity. These variables need to be determined simultaneously to minimise the average total cost for a cycle time. An example is presented to demonstrate the proposed approach.

Application of grey-based Taguchi method for simultaneous optimization of multiple quality characteristics in laser transmission welding process of thermoplastics

In the present work, Taguchi method in combination with grey relational analysis is applied for solving multi-criteria optimization problems in laser transmission welding processes. The welding parameters, namely laser power, welding speed and defocal position are optimized with respect to weld strength and weld width. Using the Taguchi quality design concept, an L16 orthogonal array table is chosen for the experiments. Grey relational analysis is applied to convert the multiple quality characteristics to a single performance characteristic called grey relational grade. Optimal welding parameters are then determined by the Taguchi method using grey relational grade as the quality index. Furthermore, analysis of variance is carried out to identify the most significant factor for the overall output feature of the laser transmission welding process. The results of the confirmation experiment show that the optimal laser transmission welding parameters can be determined effectively so as to improve multiple quality characteristics through this approach.

Method and Application of Multistage Machining Quality Control Based on Minimum Overall Mean Quality Loss

To improve the quality control effect and decrease the manufacturing cost in the product’s multistage machining processes, based on the quality loss of single stage machining process, an overall mean quality loss model of multistage machining processes is established by the integration of Duncan cost model, Taguchi quality loss model, mean shift index and average time to signal (ATS). By using this quality loss model, the overall mean quality loss optimal function of multistage machining processes is constructed and the control parameters of this function are optimally solved. Besides, The Shewhart control chart and Cause-selecting control chart can be optimally designed with the control parameters of this optimal function. Finally, on the basis of an application, the multistage machining quality control based on minimum overall mean quality loss is verified to improve the control chart’s performance under the condition of the minimum overall mean quality loss.

Taguchi quality specification categories and the computation of Six-Sigma metrics: analytical and service industry anomalies and their managerial implications

In this paper, we show that the vital Six-Sigma metrics based on traditional Six-Sigma methodology are based on the Taguchi quality specification category defined as 'nominal is best' where defects exist in both tails of the process distribution. We demonstrate that these metrics are significantly in error when applied to the other Taguchi quality specification categories, 'smaller is better' and 'larger is better' that exist in all industries, but which are particularly prevalent in service businesses. Because measurement and the production of accurate process control and improvement metrics are at the core of the Six-Sigma strategy, this anomaly is a potentially very significant one. The results show that, contrary to expectations based on Six-Sigma theory, even high-performance service processes are characterised by low levels of Taguchi robustness. The results also show that service science, in general, and the science of variation, in particular, have the potential to make a significant contribution to the improvement of service quality.

Bionic Fan Optimization Based on Taguchi Method

In this research, the multi-response optimization of mass flow rate and A-weighted SPL using Taguchi quality loss function has been done for bionic fan performance. The factors of the geometric parameters selected in this investigation are blade number, boss ratio, and blade stagger angle. The contribution of each parameter factor to the performance of bionic fan has been determined. The blade stagger angle has been found as the most effective factor and its contribution is 52.58% on multiple quality characteristics. The verification test has also been performed based on the optimum conditions predicted. The values of the mass flow rate and the A-weighted SPL at the optimum levels of the fan parameters are 0.4518 kg/s and 61.47 dB(A), respectively against the initial fan of 0.3438 kg/s and 70.50 dB(A). The mass flow rate and the A-weighted SPL have been increased by 0.1080 kg/s and decreased by 9.03 dB(A), respectively. The optimization results demonstrate considerable improvement in both mass flow rate and A-weighted SPL with the multiple response optimization combination, as compared with those of the initial fan.

Optimization of Multi-Response Problems Using Taguchi's Quality Loss Function Based on Grey Relational Grade

This article presents an approach which first combines grey relational grade and weighted quality loss function to convert the values of multiple responses obtained from each of the Taguchi orthogonal designed experiments into a single performance evaluation value. Then the analysis of variance (ANOVA) and the SN ratio based Taguchi analysis are conducted to find out respectively the relative importance of the process parameters and a set of near optimal parameter settings. A validation experiment is then conducted to confirm the finding. A case of multi-response turning process optimization is used to illustrate the proposed approach. Two sets of weights for the total quality loss were applied and the results were compared. The effectiveness of this approach was demonstrated by the improvement of turning performance in the both weight settings.

A Practical Approach to Robust Design of a RFID Triple-Band PIFA Structure

This paper presents a practical methodology of obtaining a robust optimal solution for a multi U-slot PIFA (Planar Inverted F-Antenna) structure with triple bands of 433 MHz, 912 MHz and 2.45 GHz. Using evolutionary strategy, a global optimum is first sought out in terms of the dimensions of the slots and shorting strip. Then, starting with the optimized values, Taguchi quality method is carried out in order to obtain a robust design of the antenna against the changes of uncontrollable factors such as material property and feed position. To prove the validity of the proposed method, the performance of the antenna is predicted by general-purpose electromagnetic software and also compared to experimental results.

Multi-response optimization of oil agglomeration with multiple performance characteristics

In this paper, the multi-response optimization of grade and recovery simultaneously using Taguchi quality loss function has been done for Zonguldak/Turkey bituminous coal by oil agglomeration. The controllable factors selected in this investigation are solid content, amount of oil, agitation time and agitation rate. The percentage contribution of each controllable factor has been determined on the performance of oil agglomeration. The amount of oil has been found as the most effective factor and its contribution is 65.42% on multiple quality characteristics. The confirmation experiment has also been carried out according to the optimum conditions predicted. The grade and recovery have been increased up to 0.565% and 93.04%, respectively against the initial value of grade and recovery as 0.436% and 75.08%, respectively. The results show considerable improvement in both the quality characteristics such as grade and recovery with the multi-response optimization used, as compared the initial value of grade and recovery.

Alpha mistake of Taguchi method with L18 array for STB type QCH using simulation

The alpha mistake of Taguchi method is investigated for the smaller-the-better type quality characteristic with L18 (21 × 37) array using simulation. The results showed that the Taguchi method might result in identifying incorrectly some insignificant factors as significant. In conclusion, Taguchi's quality engineering concepts are valuable, but his statistical tools, including: signal-to-noise ratio, testing at F value of four and pooling-up techniques, are found inefficient tools for robust design.

Optimization of kerf quality characteristics during Nd: YAG laser cutting of nickel based superalloy sheet for straight and curved cut profiles

Kerf characteristics are important from the quality of cut point of view. The kerf characteristics are also changing with the profile of cutting. This paper presents parameter optimization of the kerf quality characteristics during pulsed Nd: YAG laser cutting of nickel based superalloy thin sheet. The kerf quality characteristics considered are kerf width, kerf taper and kerf deviation, and measured through Tool Makers Microscope. The essential process input parameters were identified as oxygen pressure, pulse width, pulse frequency and cutting speed. Based on the Taguchi quality design concept, an L27 orthogonal array has been used for conducting the experiments for both straight and curved cut profiles. The results indicated that the optimum input parameter levels suggested for curved cut profiles are entirely different from straight cut profiles except kerf width.

Study of the Deployment of Taguchi Quality Engineering Strategy

Study of the Deployment of Taguchi Quality Engineering Strategy

Taguchi Loss Function for Varus/Valgus Alignment in Total Knee Arthroplasty

Methods of designing equipment to improve quality have been developed by Taguchi. A key feature of these methods is the development of loss function, which quantifies the financial cost (loss) resulting from deviations from target dimensions. Total knee arthroplasties can fail due to prosthetic component malalignment. A Taguchi loss function for varus/valgus alignment of the prosthesis and revision rates was developed. Six studies were identified from a comprehensive literature search. Varus and extreme valgus alignments correlated with an increased percentage of prosthetic failure. A loss function of L( y) = $326.80y2 , where y was deviation from ideal varus/valgus angle, was determined. The expected loss function was EL=$326.80y¯2+s2 , where y¯ was the mean deviance from the ideal varus/valgus angle and s2 was the variance in varus/valgus angle. This loss function was used to estimate the cost savings of using computer-assisted surgical navigation in total knee arthroplasty (TKA). The average savings of a navigated TKA versus a conventional TKA, based on the expected loss equation derived from the Taguchi loss function, was $2,304 per knee. The expected loss function derived here can serve as a tool for biomedical engineers seeking to use Taguchi quality engineering methods in designing orthopaedic devices.

An optimal tolerance allocation model for assemblies with consideration of manufacturing cost, quality loss and reliability index

PurposeThe purpose of this paper is to provide an optimal tolerance allocation model for assemblies with consideration of the manufacturing cost, the quality loss, the design reliability index with various distributions to enhance existing models. Results of two case studies are presented.Design/methodology/approachThe paper develops a model with consideration of the manufacturing cost, the Taguchi's asymmetric quadratic quality loss and the design reliability index for the optimal tolerance allocation of assemblies. The dimensional variables in normal distributions are initially used as testing and compared with the data from the prior researches. Then, the dimensional variables in lognormal distributions with the mean shift and the correlation are applied and investigated.FindingsThe results obtained based on a lognormal distribution and a normal distribution of the dimension are similar, but the tolerance with a lognormal distribution is little smaller than that with a normal distribution. The result of the reliability with the lognormal distribution obtained by the Monte‐Carlo is higher than that with a normal distribution. This paper shows that effects of the mean shift, the correlation coefficient and the replacement cost on the cost are significant and designers should pay attention to them during the tolerance optimization. The optimum tolerances of components of a compressor are recommended.Research limitations/implicationsThe model is limited to the dimensions of components with the normal distribution and lognormal distributions. The implication should be enhanced with more data of dimension distributions and cost of assembly components.Practical implicationsTwo case studies are presented. One is an assembly of two pieces and another is a compressor with many components.Originality/valueThis model provides an optimal tolerance allocation method for assemblies with the lowest manufacturing cost, the minimum quality loss, and the required reliability index for the normal distribution and lognormal distribution.

Applying Taguchi method to determine the target values in goal programming

Setting the right target is of utmost importance in goal programming. An erroneous or an unreasonable target can lead to inferior solutions, resulting in misallocation of resources. This paper, using Taguchi's quality loss function proposes a systematic approach for setting an appropriate achievement level for goals in goal programming. The application of the proposed model is illustrated through a case study.

Optimization of process parameters using weighted convex loss functions

Setting the optimal process parameters under certain criterion is among the most important factor to determine a product’s profit. In this study, we generalize Taguchi quality model to more general process scenario, which consider multiple input and output quality variables simultaneously. Using the weighted convex loss function, we discuss the optimization of process parameters for Taguchi quality model and a trade-off problem as well. The working requirements for optimization are presented and the examples to illustrate our result are demonstrated.

The alpha error of the Taguchi method with L16 array for the LTB response variable using simulation

Taguchi's quality engineering concepts are of great importance in designing and improving product quality and process. However, most of the controversy and mystique have been centred on Taguchi's tactics. This research proposes an extension to the on-going research by investigating the probability of identifying insignificant factors as significant, or the so-called alpha error, with L16 orthogonal array for the larger-the-better type response variable using simulation. The response variables in the L16 array are generated from a normal distribution with the same mean and standard deviation. Consequently, the null hypothesis that all factors in the L16 array will be identified as insignificant is true. Simulation results, however, reveal that some insignificant factors are wrongly identified as significant with a very high probability, which may provide a risky parameter design. Therefore, efficient and more valid statistical tactics should be developed put out Taguchi's important quality engineering concepts into practice.

Design of experiments in software quality improvement

The software industry and information technology (IT) research laboratories incorporate quality management methods to their everyday operations, expecting to make their products more robust to customer demands thus sustaining their market penetration against their competitors. In this work, we present a simple methodology that may assist practitioners in the field of continuous improvement in IT product development and software quality assurance to prioritise those code quality parameters that require the most attention in order to optimise run-time critical responses. Design of experiments (DOE) is employed according to Taguchi's quality philosophy to show how to discern 'cause-and-effect' relationships among code performance metrics and code oriented quality factors. Through a case study in a typical heat-flow simulations application such as often encountered in mainstream industrial operations, code quality parameters are selected to be the node count, mesh size, the numerical tolerance, the count of iterations and the solver constant.