Economic production lot-sizing model in an imperfect production system with maintenance

Purpose – We develop economic production lot-sizing model, determine optimal manufacturing quantity and investigate its properties to minimize an expected cost when a random defective rate for product is considered.
Design/methodology/approach – We investigate an optimal manufacturing quantity for economic production lot-sizing model with a random defective rate and preventive maintenance service for manufacturing machinery. If a manufacturing machinery produces defective items which more than a certain threshold, lot tolerance percent defective, then this indicates that a machine shifts from an in-control condition to out-of-control condition and maintenance services should be provided to decrease the possibility of producing imperfect-quality products. A mathematical model is developed to find optimal manufacturing quantity, optimal production run time and optimal preventive maintenance schedule.
Findings – The elapsed times until process shifts get shorter as the machine deteriorates. We consider a process which is finished at the earlier time between the optimal production time and lot tolerance percent defective-exceeded time. The economic manufacturing quantity and optimal preventive maintenance schedule are obtained and they help policymakers make appropriate
decisions for company.
Originality/value – We believe this approach is novel because the economic manufacturing quantity model is developed with preventive maintenance service and lot tolerance percent defective for manufacturing facility. Out-of-control condition and in-control condition are also considered for the optimal maintenance schedule for the manufacturing facility.

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Economic manufacturing quantity, Out-of-control, Preventive maintenance, Process deviation