Here’s how we create the parts you see above, right from your own initial concept to the finished casting:
- The process starts by researching the works drawings, using facilities such as the NRM Search Engine, to resource the very best and most suitable items for us to work from.
- The drawings are used to create a full size 3D CAD model. All modelling is done in house.
- The models are scaled down to any scale required, typically 5″ and 7 1/4″, before subtle modifications to allow the castings to be created. This can involve making ports larger, adding machining allowances or modifying details to ensure they will be visible in the final product.
- The models are sent to Auckland, New Zealand where Mike at Stanier Engineering produces wax prints of the models. These are delivered to a local foundry; usually a precious metals facility.
- The castings are sent to the UK for packaging or machining.
The Casting Process
Traditional Investment casting is carried out using a pattern to create a silicone rubber mould. This mould is used to produce the wax, which in turn is used to make a second mould made from an investment material, such as Plaster of Paris. That wax is melted from the mould ready for the molten metal to be poured in; in our case this process is carried out inside a vacuum.
However, Cro Fittings’ process is quicker, more precise and less expensive for the client. This is because the initial step of making a silicone mould for creating the wax isn’t carried out. We achieve this with the use of a Projet 3D printer.
The printer prints in two materials; a castable wax and a soluble support wax. The purpose of the support wax is to facilitate fine details, passageways and any features that protrude from the models. This support wax is dissolved after printing before the waxes are used for casting.
With a resolution of 700 dpi and layer thickness of 16 microns we can produce very fine detailing for you. The high resolution of the machine means the surface finish of the prints is a very high standard. Further, Cro Fittings’ castings retain printed details more accurately, because our process is carried out in a vacuum.