Stereolithography (SLA) utilised to print injection mould tooling in order to evaluate thermal and mechanical properties of commercial polypropylene

Injection moulding is a widely-used industrial-scale manufacturing method for plastic parts high volumes due to its high-scale economy and manufacture ease for several resins. Moulds are expensive and are only economical for large production batches. Additive manufacturing offers the ability to produce complex designs without moulds; but it isn’t economical and is only suitable for small parts numbers. We describe a hybrid IM/AM process, which utilises AM to produce moulds for IM, employing polymer-based systems for their short processing times, high resolution and ease of finishing. Due to the printed moulds insulating nature, it’s necessary to conduct trials to assess the moulded parts’ properties. Polypropylene (PP), a semi-crystalline polymer often used in IM, was selected for trial. We aimed to evaluate the thermal and mechanical properties of the moulded parts emphasising the PP crystalline structure. The resins used for printing moulds were photocurable polymers, while tooling-grade steel was utilised as industry standard control. Results indicate the insulating nature of the AM inserts affected the moulded parts’ crystallinity, but these parts had similar mechanical properties to parts moulded using a regular steel tool, indicating this system may be used for short and pilot runs in applications where these properties are critical.