ASSESS THE APPLICATION OF METAL ADDITIVE IN EXTRUSION BLOW MOULDING

Nowadays, with the availability of powerful numerical codes processing tool designers can conceive, theoretically, very high-performance tools. However, in several situations, conventional machining methods limit significantly the geometries that can be manufactured, either due to technical or budget limitations. With the advent of additive manufacturing techniques, the boundaries of the machinable geometries are being pushed forward. This work presents a case study, comprising the design of a mixer section in a blow moulding extrusion die, that combines numerical modelling tools and a manufacturing approach that integrates a metal additive manufacturing method, the Selective Laser Melting (SLM). The new manufactured geometries, that take advantage of the design freedom provided by additive manufacturing, aim improving of the mixing rates and reducing the time required to change materials during production. Figure 1 illustrates the material distribution in the flow channel 10s afters the material change (from concentration C=0 to concentration C=1), for three different tools. As shown, the extrusion die comprising the mixing section machined with conventional machining approaches (Plain) still presents a large amount of the initial material (C=0) near the wall. This is mainly a consequence of the low velocities in that region, which restricts the material renewal. On the other hand, in both extrusion dies machined by additive manufacturing (009 and 010) the initial material (C=0) is almost absent on the same problematic regions. The results obtained, in what concerns to the decrease of the time required to change the materials, clearly evidence the advantages of using numerical modelling tools to aid the design of processing equipment and the potential of employing additive manufacturing approaches, as SLM, to machine polymer processing equipment.