ILOG CPLEX 11.0 User's Manual > Discrete Optimization > Using Logical Constraints: Food Manufacture 2 > Describing the Problem

The problem is to plan the blending of five kinds of oil, organized in two categories (two kinds of vegetable oils and three kinds of non vegetable oils) into batches of blended products over six months.

Some of the oil is already available in storage. There is an initial stock of oil of 500 tons of each raw type when planning begins. An equal stock should exist in storage at the end of the plan. Up to 1000 tons of each type of raw oil can be stored each month for later use. The price for storage of raw oils is 5 monetary units per ton. Refined oil cannot be stored. The blended product cannot be stored either.

The rest of the oil (that is, any not available in storage) must be bought in quantities to meet the blending requirements. The price of each kind of oil varies over the six-month period.

The two categories of oil cannot be refined on the same production line. There is a limit on how much oil of each category (vegetable or non vegetable) can be refined in a given month:

There are constraints on the blending of oils:

The final product (refined and blended) sells for a known price: 150 monetary units per ton.

The aim of the six-month plan is to minimize production and storage costs while maximizing profit.