Process 1: Mould engineering & production
Precision investment casting starts with the engineering & production of a casting mould, also known as a wax tool. With use of a casting mould a wax model can be sprayed with a very accurate dimension and an excellent contour sharpness. These wax models are glued together onto a so-called wax ‘tree’ on which a casting funnel is mounted. In a later stage of the process, steel is poured into the funnel. Depending on the size of the series, the mould is installed either onto a manual or automatic press.
After the wax models are glued together, the tree is given a fireproof ceramic shell. This shell is constructed by repeatedly submerging the tree (up to 7 or 9 times) in a slurry and sprinkle it with ceramic sand. The ceramic layers are then hardened in a drying chamber, exposed to air.
After the layers have been formed and dried, the wax is melted out of the ceramic tree by using steam (120°C) in an autoclave. This is why it is called ‘lost wax casting’. The molten wax can be regenerated and is reusable. The ceramic tree is then baked at a high temperature (1100°C) and reaches its final strength through the sintering process. Wax leftovers are burned up during this process.
Process 3: Casting process
The desired steel alloy is melted in a large furnace and brought to casting temperature. The ceramic tree is, at the same time, heated in a oven to prevent thermal shocks during the casting process. After the tree has been heated, it is removed from the oven by a robotic arm and the steel is poured in by means of counter gravity. When the trees have been cast, they have to be cooled on a cooling conveyor (with nitrogen). The trees are then removed from their ceramic shells, by breaking the shell with a fully-automatic knock-off hammer. This removes most of the ceramic.
Process 4: Finishing & Machining
The remainder of the ceramic is removed in the Finishing Department by means of steel, sand and/or water blasting. The next step involves sawing or vibrating the products off from the steel tree. The steel leftovers are sorted on alloy and may be melted again during the next casting badge. Finally, the ingate is sanded off, the product is machined, calibrated or heat-treated when necessary.
Contact Person: Mr. Fred Zhang
Tel: 0086 574 28861663