SIMULTANEOUS DUE DATE ASSIGNMENT AND LOT SIZING WITH UNCERTAIN FLOW TIMES

Due date assignment for customer orders has been studied in various production environments using different modeling approaches. In this paper the researchers consider a production system in which the orders of several customers are produced in a single batch because of the economy of scale. If a batch is completed before receiving customer orders. inventory carrying cost is incurred but if it is completed after receiving customer orders. shortage cost is incurred and finally if the order is delivered after its due date. tardiness cost is charged. The problem is to decide on batch size. due date of batch (imposed on supply process) and lead time (to be quoted to the next coming customers) so that relevant costs are minimized, The objective function is to minimize total cost of supply. inventory carrying. shortage and tardiness. Production flow times are probabilistic which follow a probability distribution. The proposed model is solved using real-coded genetic algorithms and numerical results are presented. This work was motivated by a heavy equipment production system which has some products with relatively Two demand rates. high prices and long supply lead times.