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At the present time, there is a growing interest in additive manufacturing (AM) technologies and their integration into current process chains. In particular, the implementation of AM for tool production in micro injection molding (µ-IM), a well-established process, could introduce many advantages. First of all, AM could avoid the need for the time-consuming and expensive fabrication of molds for small series of customized products. In this work, the feasibility, quality, and reliability of an AM/µ-IM process chain were evaluated by designing and fabricating mold inserts for µ-IM by stereolithography (SLA) technology; the mold inserts were characterized and tested experimentally. The selected geometry is composed of four thin cavities: This particular feature represents an actual challenge for both the SLA and µ-IM perspective due to the large surface-to-volume ratio of the cavity. Two different materials were used for the mold fabrication, showing sharply different performance in terms of endurance limit and cavity degradation. The obtained results confirm that the µ-IM process, exploiting an SLA fabricated mold insert, is feasible but requires great accuracy in material choice, mold design, fabrication, and assembly.

Micro‐injection moulding is one of the key manufacturing technologies for thermoplastic polymeric materials for the mass production of high value miniaturized components. However, this process is not just a straightforward down scaling of the conventional injection moulding technique. Indeed, during the micro‐injection the polymer melt is forced to flow at high strain rates through very small channels in nonisothermal conditions; this can lead to complex microstructures and to parts with unexpected performances. In this work, the relationships among the processing conditions, the mechanical properties and the microstructural characteristics of polyoxymethylene miniaturized specimens obtained by injection moulding were investigated. The attention was focused on the influence of the process temperatures on the mechanical behavior, examined by uniaxial tensile tests, and on the microstructural characteristics of the specimens, examined by differential scanning calorimetry, wide‐angle X‐ray diffraction, polarized light microscopy, and dynamic‐mechanical thermal analysis. The results highlighted that material ductility in the miniaturized specimens is significantly affected by the mould temperature, because of the sample microstructure. Different degrees of orientation of polymer crystallites and different morphologies of the skin/core transition region were observed in dependence on the process temperatures. POLYM. ENG. SCI., 54:512–521, 2014. © 2013 Society of Plastics Engineers

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