Development of a rapid prototyping solution for vulcanized rubber components

Abstract

Trelleborg Sealing Solutions were interested in producing samples of functional rubber components using additive manufacturing; however the technology to achieve this was not currently available. This project was created to develop a process where additive manufacturing is used to create mould inserts, which are then used in a traditional rubber injection moulding machine to create rubber samples. This would allow the production of a batch of rubber samples without needing to produce a metal mould, thus avoiding wasted costs and saving time. 3D printing a mould insert would involve a great challenge since unlike thermoplastic polymers; the mould for rubber materials has to be heated in order to vulcanize or crosslink the material. This project started with selecting a suitable 3D printing technology and material to suit this application. This resulted to be PEEK printed using an FDM additive manufacturing technology. A moulding setup as well as various insert designs were created and tested using Moldflow simulations and moulding trials. This led to the selection of a diaphragm design for the printed insert. However at this point the PEEK 3D printing process was not yet optimised and the printed inserts were suffering from severe delamination. To solve this issue the next step was to carry out various PEEK characterisation tests (Tensile, Compression, Heat Deflection Temperature, and Differential Scanning Calorimetry) to find the optimal PEEK blend and the best method of printing it into an insert. Having found the best insert design and the optimal method of producing it, the final set of inserts was produced and tested. During these moulding trials more than 45 functional rubber components were produced from the same set of printed inserts, which did not show signs of severe degradation or delamination. Finally, rubber characterisation tests (Compression Set, IRHD, and DSC) were carried out on the produced rubber components, and it was proven that the parts created from the PEEK inserts had the same properties, and thus the same degree of cross-linking as their counterparts moulded in a traditional metal mould.