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Reviews a real‐life investigation carried out on copper coating of CO⊂2 welding wire. The major quality problems were non‐uniformity in coating thickness and other associated problems. The factors identified as responsible are speed of drawing the wire, acid, ferrous and copper sulphate. Describes three stages of the study. The results obtained revealed a number of interesting facts about the process. The extent to which the copper coating is influenced by these factors independently and interactively was vividly brought out by factorial experiments, fractional factorial experiments and standard orthogonal arrays. These results show various intricate dynamics of interest to a process controller.

The aim of this paper is to proposes a simple and unified method for generating the aliasing pattern of two‐ and three‐level fractional factorial designs be they regular or non‐regular. The paper also demonstrates how the aliasing patterns obtained using the postulated method can be used to render the main measures of aliasing severity.

The proposed method is based on viewing the fractional factorial designs geometrically. It entails regarding the columns of any design as vectors. On the premise that any two vectors are orthogonal if they are at right angle and bearing in mind that aliasing is a form of departure from orthogonality, the proposed method determines the degree of aliasing between any two columns by assessing the extent to which the angle between them differs from 90°.

Three examples were used to illustrate how the proposed method can be applied and to validate its results. The first dealt with a regular two‐level L₈ 2⁵⁻² design whereas the second concerned a non‐regular two‐level L₁₂ design used to study five‐factors, and the third example is based on a non‐regular L₁₈ design employed to examine three‐factors at three‐levels. For each of these, the aliasing pattern generated using the proposed method matches the one obtained using the conventional methods.

A recent empirical study of how experimental design is applied in certain Manufacturing Engineering journals revealed that aliasing is rarely investigated. One possible reason for this is the difficulty associated with comprehending the conventional methods of dealing with aliasing particularly in the cases where non‐regular two‐ and three‐level orthogonal arrays are used. The proposal of a simple and unified method for dealing with aliasing should encourage the researchers and practitioners to assess aliasing when performing their experiments.

During the past few years, statistical process control and experiment design concepts have taken a prominent place within the industry. The use of such tools within the Motorola, GEG manufacturing environment, has grown to the point where reflow and wave solder process development and optimisation has significantly benefited. The ability to evaluate statistically and model various known and unknown phenomena has provided GEG's manufacturing technology with a series of very powerful tools to aid in process control and development. The primary purpose of this paper is to present the various approaches used by GEG to implement the previously mentioned statistical tools, with respect to the development of infra‐red (I‐R) reflow solder processes and enhancement of certain quality characteristics associated with wave soldered printed wiring boards (PWBs). Beyond specific GEG applications, the paper discusses the role of statistically designed experiments and process control methods as a vehicle for providing answers to complex manufacturing problems. In addition, a discussion of the mathematical and graphical methods underlying the interpretation of quantitative data is presented. Perhaps the most important benefit derived from the use of statistics to solve manufacturing and quality problems is related to decision making. When experiments are conducted to isolate unwanted sources of process and product variation, decisions must be made to determine whether or not certain experimental effects are important. Through the application of statistics, the researcher can ascertain the mathematical probability associated with the random chance occurrence of various experimental effects. With this knowledge, the researcher can make decisions with known degrees of risk and confidence. Without such knowledge, an organisation might possibly expend valuable resources and derive no direct benefit. Ultimately, the principal reason for applying statistical methods and procedures is to increase quality and yield, while simultaneously reducing costs.

The purpose of this paper is to improve the key quality performance of the terminal of earphone in an electronic company.

Sequential experimental designs are employed. Significant input variables are found through a full factorial design. Then a response surface model is constructed considering curvature in the linear model.

Optimized key input variables’ parameters are found using the response surface model. The key quality performance, coplanarity of the terminal of earphone has been improved.

Instead of running a full factorial design in the first stage, a fractional factorial may be used to reduce experimental runs.

The paper presents a good solution for reducing defects caused by large coplanarity of a kind of earphone terminal.

The methodology used in this case can be easily extended to similar cases.

The aim of this study is to optimize the process parameters of area-forming rapid prototyping system to improve the model dimensional repeatability and to minimize the process time as well.

Model dimensional repeatability is based on the dimensional standard deviation of the test sample. The significant factors that affect the model dimensional repeatability and process time are established by the fractional factorial design. Response surface methodology, based on the central composite design, is applied to evaluate the regression models of the response variables including prototype’s dimensional repeatability and processing time. Finally, a desirability function for each individual response variables is constructed to obtain the optimal process parameters.

The significant factors that have an impact on the main effects of response variables model dimensional repeatability and process time found by the fractional factorial design are curing time, light flux and platform moving velocity.

All previous studies were concerned with product accuracy in area-forming rapid prototyping system. In this work, we focus on optimization of model dimensional repeatability.

The purpose of this study is to identify the most influential factors affecting the printing properties and print quality of digitally printed silk fabrics in terms of colour strength and fixation percentage.

In this study, five factors (concentration of thickener, concentration of urea, concentration of alkali, pH of pretreatment liquor and steaming duration) were investigated using a blocked 2⁵⁻¹ fractional factorial experiment. The type of thickeners [polyacrylic acid and polyacrylamide (PAM)] were considered as a block.

Linear models were obtained and statistically tested using both analysis of variance and coefficient of determination (R²), and they were found to be accurate at 90 per cent confidence level. It was revealed that concentration of alkali, concentrations of urea and pH of the pretreatment liquor had an increasing effect on colour strength, whereas concentration of thickener and steaming duration showed decreasing effect on colour strength of digitally printed silk fabrics. Furthermore, concentration of alkali, concentrations of urea had increasing effect on dye fixation percentage, whereas steaming duration showed decreasing effect on dye fixation percentage of digitally printed silk fabrics. In addition, PAM thickener based pretreatment recipe exhibited better printing properties for the digitally printing of silk fabrics.

The main influences and significant two-factor interactions were discussed in detail to gain a better understanding of the printing properties of digitally printed silk fabrics. The findings of this study are useful for further optimisation of pre- and post-treatment processes for digital printing of silk fabrics.

The purpose of this study is to demonstrate the variation between the set torque and the actual torque at which the actuator trips can be minimized using Taguchi's robust engineering methodology. The paper also aims to demonstrate the application of feature selection approach for the identification of insignificant effects in unreplicated fractional factorial experiments.

The methodology used was design of experiments with the set torque as the signal factor and the tripping torque as response variable. The compounded noise factor was identified based on the type of operations and load variation, which are not under the manufacturer's control. The effect of five control factors (with two levels each) and two interactions were studied. The experiments were designed using L8 orthogonal array.

The result showed that the factors spring height, spring thickness, star washer position and the interaction between drive shaft length and spring height play a significant role in actuator performance. The implementation of the optimum combination of factors resulted in improving the overall capability indices, Cp from 0.52 to 2.12 and Cpk from 0.4 to 1.67.

This study provides valuable information to actuator manufacturers on optimizing actuator performance.

To the best of the author's knowledge, no study has been conducted using Taguchi's robust engineering methodology to optimize actuator performance. In addition, no attempt has been made in the past to identify the insignificant factors and interactions using feature selection approach for unreplicated fractional factorial experiments.

Statistical experimental design (SED) can be used as an analytical tool to investigate the effect of a range of PCB processing parameters (variables) on certain final properties (responses). Compared to the “typical” method of carrying out experimental trials, the use of SED can identify “interactions” between variables that may not become apparent without extensive testing otherwise. The SED route also offers a measure of experimental error within the process and can suggest ways to optimise the process, with a reduced number of experimental runs. An application of the SED process is also discussed regarding the evaluation and optimisation of a horizontal liquid photoimageable solder mask (LPISM) spraying process in accordance with certain key factors.

Degradation measurement of some products requires destructive inspection; that is, the degradation of each unit can be observed only once. For example, observation on the mechanical strength of interconnection bonds or on the dielectric strength of insulators requires destruction of the unit. Testing high-reliability items under normal operating conditions yields a small amount of degradation in a reasonable length of time. To overcome this problem, the items are tested at higher than normal stress level – an approach called an accelerated destructive degradation test (ADDT). The present paper deals with formulation of constant-stress ADDT (CSADDT) plan with the test specimens subject to stress induced by temperature and voltage.

The stress–life relationship between temperature and voltage is described using Zhurkov–Arrhenius model. The fractional factorial experiment has been used to determine optimal number of stress combinations. The product's degradation path follows Wiener process. The model parameters are estimated using method of maximum likelihood. The optimum plan consists in finding out optimum allocations at each inspection time corresponding to each stress combination by using variance optimality criterion.

The method developed has been explained using a numerical example wherein point estimates and confidence intervals for the model parameters have been obtained and likelihood ratio test has been used to test for the presence of interaction effect. It has been found that both the temperature and the interaction between temperature and voltage influence the quantile lifetime of the product. Sensitivity analysis is also carried out.

Most of the work in the literature on the design of ADDT plans focusses on only a single stress factor. An interaction exists among two or more stress factors if the effect of one factor on a response depends on the levels of other factors. In this paper, an optimal CSADDT plan is studied with one main effect and one interaction effect. The method developed can help engineers study the effect of elevated temperature and its interaction with another stress factor, say, voltage on quantile lifetime of a high-reliability unit likely to last for several years.

The purpose of this paper is to investigate the effect of main process parameters of selective laser melting (SLM) technology on single lines and single layers manufactured from 17‐4 PH martensitic powder using the experimental design approach.

A fractional factorial approach has been applied to vary and to identify the optimal set of process parameters using three different powder particle size distributions for 17‐4 PH steel. This paper assesses the impact of influence factors such as process and material parameters on objective factors such as dimension of single lines and single layers, as well as surface roughness.

The influence of process parameters and materials properties on single line and single layer manufacture is shown and proved statistically. The effect of each process parameter and their interactions on single layer and single line stability and quality has been investigated, and a complex objective function analyzing geometrical stability of single lines has been proposed. The findings indicate the most appropriate 17‐4 PH powder particle size distribution.

The research provides a systematic scientific approach using fractional factorial experiment design to identify the influence of process parameters, materials parameters and their combinations on essential martensitic steels (17‐4 PH steel) single lines and single layers characteristics such as geometrical stability and surface roughness. This approach will be extended to 3D parts fabrication and reported in a later paper.