Organic rubber injection moulding uses traditional organic rubbers and synthetic organic rubbers, like SBR and EPDM. These undergo a curing process called ‘vulcanisation’, which gives them a resilient structure for high-durability applications. The rubber is heated and mixed with vulcanising agents before being injected into a preheated mould where the product is cured and formed.
Seals Direct
Natural and synthetic rubber injection moulding can create parts with excellent mechanical properties, such as increased resilience, elasticity and abrasion resistance. These properties are often required in heavy-duty applications, including tyres, hoses and industrial seals. The process has longer cycle times because of the vulcanisation process, but it provides enhanced durability.
Seals Direct, supplier of custom rubber seals, trims and gaskets, used injection moulding to manufacture rubber bumpers for a customer within the railway industry. The customer was looking for a product they could fit over the end of an RSJ steel beam for safety edge protection. We developed a product that fitted over the 20mm thick steel corner. Since it was used within railway stations, it was manufactured from a commercial grade of EPDM as it did not need to conform to the EN45545 certification required within transport systems.
The most common restricting factor with bespoke moulded rubber products is the mould tool’s initial set-up cost. As the shape required by this project was unique, we had to create a new tool to mould a corner piece specific to the customer’s requirements. The costs often exceed £2,000, which can be prohibitive for a client that only requires a small number of items. As this moulded corner piece was required by our customer for hundred buildings, they were happy to absorb the cost.
Due to the initial high set-up tooling costs, we ensured that the profile shape could fit over an RSJ made from 20mm thick steel. Failure to choose the correct profile shape may have required subsequent rounds of prototyping and tooling, leading to longer set-up and development costs. We sent our customer an existing product so they could test suitability with their specific RSJ. Once approved, we developed our corner-shaped tool on this existing product knowing that it would correctly fit over the 20mm thick steel.
This rubber bumper was developed for edge protection on steel beams. They previously experienced issues with damage to other equipment that unintentionally knocked into the end of these RSJs. By protecting the edge with a rubber-based product, anything that hit the end of the RSJ touched softer rubber rather than hard metal.
Developments in 3D printing technology have allowed us to quickly prototype rubber profiles using flexible rubber-like filaments. This enables us to print a short sample of their chosen profile for testing and evaluation before proceeding with further prototyping or bulk production. Accelerating the timeline is important for quickly refining designs and developing multiple sealing solutions suitable for the final application.
To prototype rubber sections, we use a TPU-95A filament – a Thermoplastic Polyurethane with a 95 Shore hardness. It is a blend of rubber and PVC with a hardness that is roughly comparable to the rubber on a car tyre. It offers the necessary flexibility to create rubber-like seals that can stretch and return to their original shape without deformation. It provides all the benefits of TPU with a high elasticity that is easy to print. It also offers excellent layer-to-layer bonding.