Wax injection and moulding

Model preparation for casting
Casting gold or silver involves more than just smelting the metal and pouring it into a form. A lot of preparation needs to happen prior to that. As a first step, our gold smiths prepare a master form, which needs to fulfil some requirements in order to be suitable for casting. Then, a casting channel needs to be added, and it is vulcanised in to a natural rubber block. The model is cut very precisely from the block, using a scalpel - the rubber form is created .

Wax injection and moulding
Wax with a temperature of 72°C and at a pressure of about 0.4 bar is injected into the rubber form. After a short while, the wax model can be removed and set to the wax tree. The finished wax tree is set into a steel flask and, then inside the investment mixing machine, mantled with liquid investment compound. All air is removed by creating a vacuum and agitating the compound. This way, there won‘t be any air bubbles that could lead to a poor surface in the later casting process. The predried flasks are set into a large rotary kiln with their openings facing downward.

They are burned out for 14 hours overnight in temperature controlled conditions, and then sintered to about 730°C. For casting, the flasks are cooled down to about 600°C. Next, the precious metal is melted down in a foundry crucible at a temperature of 950-1050°C. The flask is taken from the kiln and placed into the foundry. In the vacuum pressure casting plant, the liquid metal is pressed into the flask, using a vacuum and pressure.
In the centrifugal pressure casting plant, centrifugal force presses it into the flask. Following casting, the flask is taken out, the investment compound is removed. The result is a finished casting tree in gold or silver. Now, the separate components are cut from the casting tree and allocated to the various production tasks.