Integration of EPQ model and economic-statistical design of a non-central chi-square control chart considering net present value

This study develops an integrated economic-statistical model for determining the chart parameters, economic production quantity, and sampling schedule. The existing papers that integrated the mentioned concepts, suffer from three major disadvantages as follows: (1) they only have investigated the effects of quality shifts in the process mean while it is not effective just to indicate the product quality; (2) they often have optimized the manufacturing cost without considering the time value of money and statistical properties of control chart to simplify the mathematical model; (3) they usually have used fixed sampling interval for monitoring the process whereas it may be different in the real situations. To eliminate the mentioned bugs, this paper utilizes a non-central chi-square chart to monitor mean and variance of quality characteristics considering the economic and statistical properties. To early detection of assignable causes, this research applies non-uniform sampling such that integrated hazard rate over all the sampling intervals would be the identical value. Moreover, it considers the net present value of the system costs, to make the model more adapted to the real conditions. According to problem complexities, the particle swarm optimization algorithm is employed to minimize the total system costs subject to statistical constraints. Finally, a numerical example is analyzed to prove the efficiency of the suggested model. Also, a sensitivity analysis is implemented on the expected total cost per production cycle and process variables to extend insights into the matter.

کلیدواژه ها:

Economic production quantity ، non-central chi-square chart ، net present value ، variable sampling interval ، economic-statistical design