The traditional casting process known as “lost wax” dates back some 3,000 years, but today with the help of modern technology, it is used to create items from the finest jewellery to extremely complex aerospace components.
Mould Making and Wax Pattern Creation
A high quality non-shrinking silicon based rubber compound is used to produce a flexible and reusable mould. The original is placed in a box were the rubber solution is poured over then put under a vacuum to release any trapped air. Once set, the mould is then carefully cut in half and the original is removed. The two halfs are then put back together to create a detailed cavity of the original.
Depending on the item, one of our specially made waxes is then injected into the mould under pressure. After cooling, the mould is opened to reveal a perfect copy of the original. The wax patterns are then mounted around a wax stem to create a ‘Tree’ and enclosed in a stainless steel flask ready for the next process.
Investing and De-Waxing
A high quality investment powder, used in jewellery casting, is mixed with water to create a type of slurry which is then poured into the flasks which then sets around the wax tree. The flasks are then loaded into a computer-controlled kiln where, over the period of 16 hours, it will melt out the wax and fire the flasks. Once the kiln has spent several hours at 750c it is slowly cooled to 500c, only then the flasks ready to be cast.
Casting and Finishing
Brass or Bronze ingots are melted by a high powered induction generator or a gas air furnace. Depending on the weight and size of the items the molten metal is then either poured under vacuum or cast by centrifuge to ensure that the molten metal fills every cavity and detail.
After more cooling the flasks are then quenched in water and high a pressure water jet is used to remove most of the investment and allowed to dry before a very fine shot blast finishes the process.
The castings are then cut from the tree and the feeders removed to create finished copy ready for checking and packing.
Some items are put through our rumble polisher which over 4-6 hours create a nice satin finish but plating, painting, patternation or mop polishing are all finishing processes we leave to our customers.