Optimization of polymer extrusion with genetic algorithms

In the manufacture of plastics parts by extrusion or injectionmoulding, polymers are usually plasticized in single-screw units.The mechanisms involved are complex and dependent on the material,the geometry, and the type of operation. Usually, process optimizationis based on trial and error—a very inefficient method.A more efficient approach is to solve the inverse problem, i.e.to determine the operating conditions that produce the desiredoutput and/or product characteristics. An alternative strategyconsists in maximizing the value of an objective function, bysolving the direct problem iteratively. The nature of the objectivefunction—with conflicting criteria—and the characteristicsof the search space make an approach based on genetic algorithmsworth investigating. Therefore, a modelling package, an objectivefunction, and a genetic algorithm are interrelated to solvethe industrial extrusion problem. The advantages and disadvantagesof this implementation are discussed.