Thermal behaviour of resin inserts for micro injection moulding: a FEM analysis

One of the future challenges is to satisfy a manufacturing market in which the raw material and its storage are increasingly limited, while the need for product diversification is growing. In this context, the global market, especially in the biomedical sectors, sees a growing interest in the miniaturization of products and features for which micro injection moulding (µIM) seems to be ready. Improvement in mould flexibility in terms of reconfigurability of the cavity mould and features is requested to µIM. A tailored insert approach for the micro mould has been adopted to study different materials and micro manufacturing technologies to produce the inserts with such extreme features. Novel high temperature resins for additive manufacturing, able to withstand temperatures up to 250°C, are used to realize inserts for µIM prototyping and small batches. A numerical simulation of the process to produce a 400µm thick thin plates of polymethylmethacrylate (PMMA), a typical benchmark and polymer for microfluidic applications, has been conducted to evaluate the thermal behavior of the resin insert on the molten polymer with respect to the steel one. The results evidenced an isolating behavior of the resin which reduces the thermal dissipation with consequent lower viscosity also during the packing pressure. To validate the results an experimental campaign, was made using both a steel insert and a high-temperature resistance resin insert. The part produced with the resin insert presented diffused flash, a defect usually correlated to high melt temperature and high injection pressure.