Abstract
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.
Highlights
Injection molding of micro or thin components is a widespread technology due to its capability of manufacturing low-cost and highly repeatable polymeric parts relevant to many different fields, from IT to healthcare to the biomedical sector
Considering the micro world, which this paper is focused on, some experimental works were already done in recent years, especially by Tosello et al, about the fabrication of bricks and cylindrical pillars molded by soft tools carried out via digital light processing (DLP) technology
Leveraging the very low part thickness, in this work, the ejection was performed by a cylindrical pin with a diameter of 1.3 mm placed on the sprue at the center of the mold insert, pushing on a thicker region of the molded part and enabling a radial peeling of the parts from the cavities
Summary
Injection molding of micro or thin components is a widespread technology due to its capability of manufacturing low-cost and highly repeatable polymeric parts relevant to many different fields, from IT to healthcare to the biomedical sector. Considering the micro world, which this paper is focused on, some experimental works were already done in recent years, especially by Tosello et al, about the fabrication of bricks (dimensions 5 × 4 mm) and cylindrical pillars (height and diameter 200 μm) molded by soft tools carried out via digital light processing (DLP) technology These authors focused on thermal numerical modeling for tool life evaluation [15], cost analysis, and the optimization [16,17] and quality of molded parts [18,19,20]. The two molds were characterized to evaluate the achieved dimensional and geometrical precisions of the stereolithography process and experimentally tested in the micro-injection molding machine to evaluate the replication capability and durability in terms of number of shots to failure (NSF), and the feasibility, accuracy, and reliability of the proposed SLA/μ-IM process chain
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