There are hundreds of people in charge of production management that make a manual production scheduling. This is a combinatorial optimization problem of complex solving because of the large number of constraints, the variety of selection criteria and the almost infinite number of possible solutions (even for problems of small dimension).
Therefore, the implications of a specific decision (e.g.: to place a product on a machine before other products) are always decisive in the final outcome of the production. To obtain a satisfactory result it is necessary to include an optimization phase in the scheduling production process.
Using the experience over the years, production managers are able to minimize the negative impact of having to manually produce a sequence of manufacturing operations. However, even these solutions can be improved. A better sequence of operations will result in an increase of overall productivity, with the respective financial impact.