Storage Problem in a Shampoo Making System

In this paper we address the problem of planning a temporary storage area in a shampoo making system. Everyday, the packing service of the company, which gathers several packing lines, transmits plans of orders to produce (also called batches) to the making service. Each plan corresponds to the work that will be performed by one packing line for the next production horizon. A batch, which consists of a volume of 12 tons of the same shampoo juice is produced by the making service and transferred to a tank before being sent to the corresponding packing line. There are several families of shampoo and a tank must be cleaned when the next batch to store have a different shampoo family than the last stored batch. In this temporary storage problem the goal is to minimize the number of tank cleanings and the maximum lateness of batches. Two different cases of this problem are considered: in the first the lateness is allowed, and in the second no lateness is allowed. Complexity of these two cases is studied and three solution algorithms are proposed to solve the second case.