Abstract
Injection moulding is one the most familiar processes for manufacturing of plastic parts by injecting molten thermoplastic polymers into a metallic mould. The cycle time of this process consists of the phases of injection, packing, cooling, and ejection of the final product. Shortening of cycle time is a key consideration to increase productivity. Therefore, in this manuscript the adoption of additively manufactured mould inserts with conformal cooling channels by means of selective laser melting (SLM) with the aim to reduce process cycles is presented. The design and manufacture of a mould insert with conformal cooling channels for producing pressure fitting thermoplastic parts is described. Numerical analysis of the injection process and simulation of shape distortions after SLM were conducted providing useful results for the design and manufacture of the mould insert. The results of the numerical analyses are compared with experimental 3D geometrical data of the additively manufactured mould insert. Temperature measurements during the real injection moulding process demonstrating promising findings. The adoption of the introduced method for the series production of injection moulded thermoplastics proves a shortening of cycle times of up to 32% and a final product shape quality improvement of up to 77% when using mould inserts with conformal cooling channels over the conventional mould inserts.
Highlights
Additive manufacturing (AM) processes have recently gained immense importance in producing industries especially in sectors where high quality and shape accuracy is demanded for low-volume manufacturing or individualized products [1,2]
While other authors either focus on the design and optimization conformal cooling channels in injection moulds with for particular applications [12,13,14] or on the cooling effects during injection moulding with different mould materials or hybrid solutions [15], in this work we provide an insight into the holistic design approach of the adoption of additively manufactured mould inserts with conformal cooling channels for the production of injected moulded thermoplastics parts
The mechanical properties of the final product produced with conformal cooling were not explicitly characterized experimentally over those produced by conventional cooling, a series of mechanical pull-out and hydrostatic creep tests as well as bending tests under pressure were conducted to ensure the quality of the final products as per the manufacturer’s quality control requirements
Summary
Additive manufacturing (AM) processes have recently gained immense importance in producing industries especially in sectors where high quality and shape accuracy is demanded for low-volume manufacturing or individualized products [1,2]. Laser-based powder-bed fusion (L-PBF) and in particular selective laser melting (SLM) are able to provide metallic products of almost unlimited complexity with mechanical and fatigue behavior similar to bulk material. These advantages make SLM an ideal solution for the fabrication of moulds [3]. Maraging stainless steel has been the material of choice in aerospace and tooling sectors due to excellent mechanical properties such as high strength and toughness. Maraging steels processed via SLM generally exhibit higher yield strength, tensile strength and hardness compared to wrought counterparts [6]
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