M. Affan Badar

Intelligent Search-Based Selection of Sample Points for Straightness and Flatness Estimation

Form error estimation with a CMM requires prudent sampling and accurate zone fitting. This paper proposes use of optimization search methods for reducing sample size, while maintaining high accuracy. The approach is demonstrated with examples of straightness and flatness. For straightness, region-elimination search is used. For flatness, two pattern search methods: Tabu search and a hybrid search, are employed and their performance is compared. Sampling begins with a necessary number of initial points and a zone is determined. Next points are sampled based on the search methods, with suitable application of intensification/diversification strategies, looking for improvement in the zone fit. Search is conducted in both the +ve and -ve directions from the fit feature and is stopped when a solution for the maximum deviation is realized. The two solution points are added to the initial set and the corresponding tolerance is computed. The tolerance is compared with that obtained for the population of a large sample, to verify the accuracy. It is found that the number of points sampled is potentially less than that typically used to achieve the same accuracy.

Second-law-based thermoeconomic optimization of a sensible heat thermal energy storage system

An analytical method for the second-law-based thermoeconomic optimization of a sensible heat-storage system, in which the energy is stored in a large liquid bath from a hot-gas source, is presented. In this approach, monetary values are attached to the irreversible losses caused by the finite-temperature difference heat transfer and pressure drop in the storage system. Results are presented in terms of the optimum number of transfer units as a function of a dimensionless unit-cost ratio, charging time, and reduced temperature difference of the storage system.

Uncertainty analysis of heat-exchanger thermal designs using the Monte Carlo simulation technique

The Monte Carlo simulation technique for determining uncertainties of the thermal parameters needed in designing heat exchangers is discussed. Parameters such as the outside diameter Do, thickness t and thermal conductivity k are assumed to have Gaussian distributions, while the heat-transfer coefficients hi, and ho are considered to follow normal, log-normal and Weibull forms of distribution. An illustrative example is presented. The overall heat-transfer coefficient U obtained from the simulation is found to have a distribution that is well approximated by the Weibull model. Using the Weibull distribution of U, the additional percentage area is calculated for 80 and 99% confidence levels (CLs). The proposed approach of design analysis incorporates realistic risks associated with uncertainties of the parameters.

Experimental Analysis of Search-Based Selection of Sample Points for Straightness and Flatness Estimation

In earlier work [Bader et al., ASME J. Manuf Sci. Eng. 125(2), pp. 263-271 (2003); Int. J. Mach. Tools Manuf. 45(1), pp. 63-75 (2005)] the authors have presented an adaptive sampling method utilizing manufacturing error patterns and optimization search techniques for straightness and flatness evaluation. The least squares method was used to compute a tolerance zone. In this paper, experimental analysis is performed to verify the sturdiness of the adaptive sampling procedure. Experiments are carried out to investigate the effects of different factors on the sample size and absolute percent error of the estimated tolerance from that of a large population sample. Twelve 7075-T6 aluminum plates are end-milled and 12 cast iron plates are face-milled. Two sets of four plates from each lot are selected randomly, one each for straightness and flatness estimation. Factor A used in both straightness and flatness analyses is manufacturing process (i.e., surface error profile). Factor B for straightness is step size whereas for flatness it is search strategy (i.e., number of bad moves and restart allowed). Factor C for flatness is search algorithm (i.e tabu and hybrid). Plates are nested within the levels of manufacturing process. The results have been analyzed and compared with other sampling methods. The analyses reveal that the current approach is more efficient and reliable.

Reliability analysis of aeroplane tyres

Aeroplanes are repairable systems consisting of several non‐repairable parts; tyres are one of these. Proper record of failure data is valuable in interpreting the failure pattern, for comparative evaluation of the quality of tyres of various manufacturers, and for prediction of the future needs in a specified planning horizon or for specified operational hours. Analyses failure data of several aeroplane tyres in an aviation set‐up, and interprets these in a reliability framework. Three parameters Weibull model is found to be quite appropriate for reliability characterization of tyres. These reliability models can be effectively integrated into a computerized material requirement planning system of the aviation facility to forecast the number of tyres needed for a given planning horizon.

Impact of ISO 9001 certification on firms financial operating performance

Purpose – The purpose of this paper is to investigate the impact of ISO 9001 certification on US firms’ financial operating performance for a period of five years including one-year prior to certification, year of certification, and three fiscal years after certification. Design/methodology/approach – The paper is based on an examination of a sample of 397 firms that had received ISO 9001 certification from 1991 to 2002. Certified-firm, non-certified-firm, and matched-control-firm operating performances were examined over the same period based on the ratio of pre-tax operating income to total assets (EBITA/TA). Wilcoxon signed-rank test was used to test for significant differences in operating performance among the certified, non-certified, and matched-control firms. Findings – The paper concludes that there was significant improvement performance from prior year to year of certification. The certified firms performed better than the non-certified firms. The certified firms also performed better than the ...

Cost of quality consideration following product launch in a present worth assessment

Purpose – The purpose of this paper is to investigate the impact of costs of quality on the present worth (PW) of a new product launch at a North American automobile manufacturer. Design/methodology/approach – The paper is based on the examination of various cash flows associated with a new product launch within an automobile manufacturer. Standard cash flows and a PW analysis were examined and compared to non-standard cash flows which take into consideration post-launch cost of quality (CoQ). A sensitivity analysis was used to determine if any CoQ factors affected the integrity of the product launch. Findings – The paper concludes that there is an impact on the PW of a program when CoQ is considered as a cash flow element. CoQ should be considered in a product launch PW analysis preceding any commitment to invest. Research limitations/implications – This study suggests that, given data on the costs that will accrue assuming standard quality concerns following product launch, and the occurrence of special...

An optimal integrated QSMS model from cluster analysis

Purpose The purpose of this paper is to develop an optimal model of an integrated quality and safety management system (QSMS). Design/methodology/approach Keywords related with these systems were identified from international standards and subsequently mined from a selection of peer reviewed articles that discuss and propose varying forms of integrated models for both systems. Cluster analysis was used to establish the degree to which integrated models, as described in the articles were quality dominant vs safety dominant. Word counts were utilized for establishing content and attributes for each category. An optimal integrated model was developed from the final cluster analysis and substantiated by a one-way analysis of variance. Experts from industry were consulted to validate and fine-tune the model. Findings It was determined that characteristics of an optimal integrated model include the keywords “risk,” “safety,” “incident,” “injury,” “hazards,” as well as “preventive action,” “corrective action,” “rework,” “repair,” and “scrap.” It also combines elements of quality function deployment as well as hazard and operability analysis meshed into a plan-do-check-act type work-flow. Research limitations/implications Given the vast array of clustering algorithms available, the clusters that resulted were dependent upon the algorithm deployed and may differ from clusters resulting for divergent algorithms. Originality/value The optimized model is a hybrid that consists of a quality management system as the superordinate strategic element with safety management system deployed as the supporting tactical element. The model was implemented as a case study, and resulted in 13 percent labor-hour saving.

Cost consequence of failure in failure mode and effect analysis

Purpose The purpose of this paper is to investigate the possibility of including the cost consequence of failure in the a priori risk assessment methodology known as failure mode and effect analysis (FMEA). Design/methodology/approach A model of the standard costs that are incurred when an electronic control module in an automotive application fails in service was developed. These costs were related to the Design FMEA ranking of the level of severity of the failure mode and the probability of its occurrence. Monte Carlo simulations were conducted to establish the average costs expected for each level of severity at each level of occurrence. The results were aggregated using fuzzy utility sets into a nine-point ordinal scale of cost consequence. The criterion validity of this scale was assessed with warranty cost data derived from a case study. Findings It was found that the model slightly underestimated the warranty costs that accrued, but the fit could be improved with adjustments dictated by actual usage conditions. Research limitations/implications Cost data used in the simulations were derived from government and academic surveys, analyses, and estimates of the manufacturing cost structure; and nominal costs for various quality issues experienced by Tier 2 automotive electronics supplier. Specificity is lacking. The sample size and the type of the failure modes used to validate the model are constrained by the number and type of products which have had demonstrable performance concerns over the past three years, with cost data available to the authors. The power of the validation is limited. The validation is considered a screening assessment. Practical implications This work relates the characterization of risk with its potential cost and develops a scaling instrument to allow the incorporation of cost consequence into an FMEA. Originality/value A ranking scale was developed that related severity and occurrence rank scores to a cost consequence rank that keys to a cost of quality figure (given as percent of sales) that would accompany a realization of the failure mode.

Effect of Price and Brand on Common Platform Appliance Failure

This main objective of this study is to determine if common platform dishwashing products have similar warranty failure rates when brands and price points are variable. Data for this study are based upon over four years of data involving one million individual sales and over 150,000 warranty failures of a common platform dishwashing appliance. It is concluded that there are similar failure rates between common platform dishwashers when different brands are at the same price point. Other conclusions indicate that there are non-similar failure rates between common platform dishwashers when the same brand is at different price points. There is a significant resource cost in the development of products. To minimise the resource cost and maximise the return on investment, many companies develop several new products from one common platform. Common platforms spread across several separate brands. Different brands attract different customers who have different perceptions of quality. Customers view quality as a mix of utility and reliability and expect high reliability during the warranty period. It is often assumed by the developer that the warranty failure rate will be similar for common product platforms even when products are marketed under different price points. The goal of this research is to test if this common assumption is accurate.