Complete Inspection Plan Research Articles

Tolerance chart balancing with a complete inspection plan taking account of manufacturing and quality costs

This paper introduces a mathematical model of tolerance chart balancing for machining process planning under complete inspection. The criteria considered in this study are based on the combined effects of manufacturing cost and quality loss, under constraints such as process capability limits, product design specifications, and product quality requirements. Manufacturing costs include the machining cost, part cost, inspection cost, reworking cost, and replacement cost. The machining cost is expressed in geometrical decreasing functions, which represent tolerances to be assigned. Process variability is expressed in quadratic loss functions, which represent the deviation between the part measurement and the target value. An example is presented to demonstrate the proposed model. A comparison made with previous methods shows that the proposed model minimizes the total cost of manufacturing activities and quality-related issues in machining process planning, particularly in the early stages. Moreover, the applications are not be limited to machining process planning but can also be used in other forms of production planning.

Optimal Parameter and Tolerance Design with a Complete Inspection Plan

The need to remain competitive has led manufacturing sectors to consider tolerances as the key to achieving low cost and high quality. To produce quality products at low cost in today’s manufacturing industry, an integration of product design and process planning is essential. Process tolerance is one of the most important parameters that link product design and process planning. The process mean is also a critical parameter for further quality improvement and cost reduction under the permissible process setting adjustment within design tolerance limits. This study discusses an approach to integrate the product and process design via the optimisation of process mean and process tolerance.

Economic design of a complete inspection plan with interactive quality improvement

Consider the monitoring of an ongoing production process subject to complete inspection. Inferior quality products are either reworked or scrapped to assure good outgoing quality. Whenever the quality characteristic of a product exceeds a predetermined action limit, remedial action is taken to restore the process to an in-control state. In addition, the decision maker has a learning opportunity to improve the process by investing in resources to identify and eliminate the causes of deviation from the target quality. Taking a learning action would improve the mean value of the quality characteristic of items produced in an out-of-control state. This paper proposes a cost model to determine the optimal number of learning actions to be taken and the optimal action limit. The model considers the trade-off between quality cost and process improvement cost.

Selection of the Optimal Precision Level and Target Value for a Production Process: The Lower-Specification-Limit Case

In a complete inspection plan, every finished item is subject to repeated measurements for inspection of quality. The average of these measurements is used to determine its disposition. Items are acceptable and sold at the regular price to the primary market if the average value of repeated measurements meets a lower specification limit. Otherwise the items are sold as scrap at a reduced price. With a consideration of inspection error, this paper presents an economic model to determine the most profitable target value and optimal measuring precision level for a production process. As expected, the model without error consideration is a special case of our model when the inspection precision level approaches infinity. Moreover, the optimal number of repeated measurements is given, based on maximizing the net expected profit per item.

Impact of inspection errors on performance measures of a complete repeat inspection plan

In quality assurance of critical multicharacteristic components complete repeat inspection plans have been proposed to guard against inspection errors. The optimal number of repeat inspections is determined using a model for the plan which minimizes the total expected cost, which consists of the cost of false acceptance, cost of false rejection and cost of inspection. In this paper performance measures for such plans are defined and then the statistical and economic impact of inspection errors on these measures is investigated. The impact of the errors is studied by conducting sensitivity analysis on the errors utilizing a computer software which implements an algorithm that determines the optimal parameters of the model of the plan. Then the levels of the errors are varied and the behaviour of the performance measured are observed. Results indicate that the impact of type I and type II errors are significant and have considerable effect on the performance measures of complete repeat inspection plans. Als...

Inspection error effects on economic selection of target value for a production process

In a complete inspection plan, every finished item is subject to variable inspection. Items are acceptable if they meet specifications. Otherwise, the items are sold as scrap at a reduced price. This paper presents an economic model to determine the most profitable target value for a production process with consideration of inspection error. As expected, the model without error consideration is the special case of our model when inspection precision level approaches infinity.

A complete inspection plan for dependent multicharacteristic critical components

Here a complete inspection plan for critical components with several characteristics is designed for the case where the characteristics’ defective rates are statistically dependent. The plan minimizes total expected cost resulting from type-I and II errors and the cost of inspection. A mathematical model and an algorithm for obtaining the optimal number of repeat inspections are developed and demonstrated by an example. The output of the model is an optimal inspection plan to control the quality of critical components.

Economic design of a complete inspection plan with feedback control

This paper studies production control with complete inspection where every finished product is subject to variable inspection. Two process states, in-control and out-of-control, are assumed. If the inspection signals that the process is out of control, remedial action is taken to restore the process to the in-control state. Inspected items are either accepted with a quality cost or reworked according to the observed quality characteristic. Specification limits and action limits are derived from an economic model.

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

Due to advances in automated manufacturing systems and automatic inspection equipment, complete inspection (screening) has drawn increased attention recently and has become a widespread practice. Screening can be based on the performance variable of interest or on a variable which is correlated with the performance variable. Using a correlated variable as the screening variable is attractive when the inspection on the performance variable is destructive or costly. The purpose of this article is to illustrate both theoretically and empirically when a correlated variable rather than the performance variable should be used as the screening variable when inspection error is present.

Economic design of a complete inspection plan for bivariate products

SUMMARY Complete inspection plans for bicharacteristic products are considered. A decision approach is presented to minimize the cost involved after inspection. Extension to multicharacteristic models is also discussed.

Selection of the Optimal Inspection Precision Level for a Complete Inspection Plan

Due to the advances in automated manufacturing systems and automatic inspection equipment, 100% inspection has recently drawn increased attention. Consider such an inspection plan, where all the outgoing items are subject to inspection by variables. If ..

Economic design of product specifications for a complete inspection plan

Abstract In a complete inspection plan, all outgoing items are subject to inspection, and the items failing to conform to the predetermined specifications are reworked so that their quality characteristics are exactly equal to the expected value (target value). This paper presents an economic model to determine the most profitable specifications for the complete inspection plan with the considerations of (a) economic loss caused by quality deviations, (b) rework cost, and (c) inspection cost. The solution to the cases in which the inspection cost is a constant provides important insights of the model. A detailed solution procedure is also given to a model in which the inspection cost is a linear function of the width of the specifications, the quality characteristic is normally distributed, and other loss and cost functions are assumed of a quadratic or linear form.

The Effects of Inspection Error on a Complete Inspection Plan

Abstract In a complete inspection plan, every incoming item is subject to variable inspection. If the inspection result indicates that an item fails to meet predetermined specification limits, the item is reworked so that its quality characteristic is exactly equal to the target value. The specification limits are determined by the tradeoff among the cost incurred by imperfect quality, cost of rework and cost of inspection. The economic and statistical effects of inspection error on the complete inspection plan are investigated. Two models with considerations of inspection error are developed under different rework schemes, then compared with the model without inspection error consideration.