Applying high-performance resins in stereolitography printing to produce prototype injection moulds

Additive manufacturing (AM) revolutionised the modern plastics industry. Its flexibility and ability to build almost any complex geometry without the need for conventional tooling or machining is especially desirable. In our article, we analysed two resins which can be processed by vat photopolymerisation: High Temperature and Rigid10K. They are especially recommended for rapid tooling because of their resistance to heat loads, high strength and stiffness. The application of vat photopolymerisation to produce prototype injection moulds is a definite novelty because the international research community has not realised the potential of this AM technology in rapid tooling. We performed dynamic mechanical analysis in temperature sweep and creep time temperature superposition (TTS) modes to determine the temperature-dependent stiffness and creep characteristics of the resins. The storage modulus of the High Temp resin was 2960 MPa at room temperature while it was 4055 MPa for Rigid10K. Their difference in storage modulus gradually diminished as they were heated to 123 °C. Above that, the High Temp resin showed higher modulus. The creep compliance of Rigid10K was considerably lower compared to the High Temp resin until 90 °C but it was excessive above that. After the material tests, two injection mould inserts were printed and post-cured. The inserts were fitted with strain gauges and thermocouples, which measured the operational deformations and the temperature of the inserts during injection moulding. The Rigid10K insert showed nearly an order of magnitude lower maximum deformation than the High Temp insert. The Rigid10K insert endured the injection moulding test while the High Temp insert cracked. The results proved that both resins are applicable in prototype injection mould making, but the durability of the Rigid10K insert is considerably better.