Off-Line Quality Control, Parameter Design, and the Taguchi Method

Abstract

A Japanese ceramic tile manufacturer knew in 1953 that is more costly to control causes of manufacturing variations than to make a process insensitive to these variations. The Ina Tile Company knew that an uneven temperature distribution in the kiln caused variation in the size of the tiles. Since uneven temperature distribution was an assignable cause of variation, a process quality control approach would have increased manufacturing cost. The company wanted to reduce the size variation without increasing cost. Therefore, instead of controlling temperature distribution they tried to find a tile formulation that reduced the effect of uneven temperature distribution on the uniformity of tiles. Through a designed experiment, the Ina Tile Company found a cost-effective method for reducing tile size variation caused by uneven temperature distribution in the kiln. The company found that increasing the content of lime in the tile formulation from 1 % to 5% reduced the tile size variation by a factor of ten. This discovery was a breakthrough for the ceramic tile industry.A technique such as this that reduces variation by reducing the sensitivity of an engineering design to the sources of variation rather than by controlling these sources is called parameter design. This example, which appeared in a Japanese book, "Frontier Stories in Industry" published by Diamond Sha Publishing Company in Japan, illustrates that parameter design is a cost-effective technique for improving manufacturing processes.

Multi-response optimization using weighted principal component

“…In the application of the PCA method [14,15], the main processes of dealing with the multi-response problem are: (1) to compute the quality loss of each response, (2) to normalize the quality loss of each response, (3) to transform these normalized quality loss into a multi-response index or a named multiresponse performance statistic, (4) to obtain the best combination of factors/levels, and (5) to perform a confirmation experiment. Above all, process (3) is the spirit of PCA method in solving the multi-response problem.…”

“…Its objective is to obtain the best combination of factors/levels so that the quality engineers can control the quality of industrial products in offline design. To achieve Taguchi's objective, three stages must be applied-system design, parameter design, and tolerance design [1,2]. By now, the Taguchi method can not optimize the multi-response problem; engineers' judgement is the only way to solve the multi-response problem in the Taguchi method.…”

Simultaneous Parameter and Tolerance Design for an Electronic Circuit Via Computer Simulation and Statistical Optimization

“…a poor grade or process should be selected at the initial design stage for economic reasons. The assigned low, middle, and [1,16,21,25,28].…”

Cost effectiveness of using a correlated variable in a complete inspection plan when inspection error is present

“…This function has been shown empirically to be appropriate for many products [3,12], and has been used in many areas, including parameter design [3,14], tolerance design [ 14,161, process capability analysis [14], and design of inspection specifications [15-181. Nevertheless, other cost functions can be used under a similar framework presented in this article. The per-item expected quality cost is determined by…”