The Economic Design of -Charts When There is a Multiplicity of Assignable Causes

Cost comparisons of modifiedX̅chart for autocorrelated observations

“…Duncan [6] presented the first cost model for economic design determining the values of test parameters for the X control charts that minimizes the average cost when a single out-of-control state (assignable cause) exists, which is called the economic design of X control charts. Since then, considerable attention has been devoted to the economic determination of the test parameters of X charts [7][8][9][10]. Lorenzen and Vance [1] provided a unified approach to the economic design of process control charts.…”

A Study About Average Cycle Time in Maintenance of Equipment.

“…The control charts are the important tools of statistical process control SPC, they can be used in order to detect process shifts in both line of mean and variance, the tool of x control chart can monitor and indicate average cycle time, and to show if the procedure of maintenance of equipment is not under statistical control, the corrective action will be done in order to prevent further nonconforming products and to be manufactured by defected equipment and to stop losses [1], it means that the maintenance will return production to the corrected condition, the maintenance with SPC is used to achieve an optimal product quality, the x control chart is used for this purpose, therefore it is regarded as a main tool in maintenance procedure in the manufacturing firms, and it can give greater chance to designate a model to value statistical criteria in this procedure, the first model of economic design of x control chart was applied by the researcher, and later he extended his research from single to multiple assignable causes in which the failure mechanism was assumed to be an exponential distribution [2], by its equations, it can really give lower time and minimum cost when compared with other models such as Shewhart's model, because the researcher added an optimum methodology in his research in order to get three design parameters: subgroup size (n), sampling interval (h) and control-limit width (+ k & -k standard deviation), and this initial model was made for minimizing cycle time [3].…”

A Study About Loss of Costs of Maintenance for Equipment by Using Taguchi Method of Quality Control.

“…The maintenance under statistical control is used to achieve maintenance with higher quality level; hence, the xcontrol chart is used as a main tool for the purpose related to maintenance of equipment. Also, the control chart will give greater chance to designate a model for economic design to evaluate statistical criteria in the maintenance procedure, and the first model of economic design of x control charts is applied by the researcher, later he extends his research from single to multiple assignable causes in which the failure mechanism is assumed to be an exponential distribution [2], in addition, it can really give lower time and lower cost when compared with Shewhart's model, and an optimum methodology to get three economic design parameters of sample size (s), sampling interval (h) and control-limit width (+ & -k standard deviation), this initial model is made for minimizing loss cost, sampling cost, testing cost, repairing cost, false alarm cost, searching cost, and an increasing cost from out-of-control process [3,4].…”