Sometimes a product can only realistically be configured as a closed volume. Bottles, flasks, fluid containers and vessels of all types, including low pressure gas containers need to be produced as a hollow part and this is often quiet difficult to achieve as a rapid prototype, especially with the right material characteristics.

Fortunately there’s a solution to this in a process termed RotoRIM, the rotational moulding or casting of a hollow part in PU resin. Conventional rotational moulding, used to create large vessels in low volumes or blow moulding, used for small to medium sized vessels in higher volumes, both utilise thermo-plastic resins, and in the case of roto-moulding, the tools need to be heated to a high temperature as part of the process. For this reason the tools are manufactured from aluminium alloys or tool steel, and as a consequence the costs are relatively high in small numbers.

Although PU roto-moulding or RotoRIM, involves a thermal reaction inside the tool, the resultant temperatures are low, which allows us to make tools from lightweight PU materials or epoxy resins. The advantage is that these tools can be produced quickly and at lower cost so allowing our clients to experiment with their designs whilst also facilitating potential low-volume production capability as a follow-on.

Examples where RotoRim has proven to be a cost effective route to prototypes as well as low volume production are most prevalent in the automotive and scientific equipment industries where manufactures of niche or premium vehicles, or scientific instruments for example, can enjoy the benefits of fluid or gas tight vessels, with good quality A surfaces within a few weeks of placing an order. And it’s not just vessels, we can also provide pipes and ducting with complex profiles, inline reservoirs, enclosures with re-entrant features and low shore hardness bellows and bladders.

Benefits of Rapitypes Reaction Injection Moulding (RIM moulding)

  • Low-cost tooling for large parts
  • Thin walled components (1.5mm)
  • Short lead-times for large components
  • Low volume production components
  • Large one off or prototype component manufacture up to 2000mm long
  • Low capital investment.
  • Short or long runs
  • Minimum set up
  • Cosmetic surface finishing
  • In-mould coating (no need for post finishing)
  • Integral gaskets and glands
  • Flame retardant materials (V0)
  • Rigid foam buoyant water proof materials
  • Soft foam materials
  • High impact PP like elastomer
  • Encapsulation and over-moulding
  • Roto RIM moulded hollow components

RIM PU is the result of a reaction between two liquid components isocyanate and polyol as they are injected into a closed mould at low pressure. The two components are mixed together as they flow into the mould as a low-viscosity liquid and the reaction, which increases the temperature and the pressure at the surface of the tool, forms the polyurethane part in the tool cavity.

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