The operation of die-casting mould.
1. Prepare the operating tools, check that the flame gun. Fuel can and pressure are under normal operations, and make the die-casting cement (mixing cement or soil with edible oil and water. Better to use the cement commonly used for making tooth moulds).
2. After selecting the desired jewellery design from the sketches manual, weigh an amount of metal about 0.6 - 1 gram more then the nominal weight specified in the sketches manual, then place the metal dose oil the upper part of the sprue.
3. Use a small flame the heat rapidly the periphery of the mould in several rounds.
4. Concentrate the flame (for extra large moulds it is batter to use two flames for heating at the same time. One for the upper portion and one for the lower) at the metal and heat gradually to the required temperature. (During the process boric salt can be added to facilitate melting if necessary).
5. When the metal completely melts and becomes white hot, the white hot metal is flowing with high fluidity, then press the cement down onto the die-cast mould slowly and straightly from right above the mould, then press the cement down slowly and steadily onto the mould, until it has reach the botton or two-thirds the depth of the mould cavity.
6. Remove the cement after 15 seconds and pick up the mould with tweezers.
7. Clean the mould with brush in the water. Heat up the mould, steep it in hydrochloric acid then take it out and clean it with water if necessary.
8. Rectify the shape of the mould.
Important points to note.
1. Do not damage the mould with pressure, shocks or moisture.
2. The mould cement should be compact without any hollow spaces, also it should not be too soft or hard.
3. Do not use strong flames to heat quickly at the start of the process. Do not heat it partially.
4. During die-casting do not stamp or press too quickly.
5. Die-casting action must be steady, accurate without any shaking or shrinkage.
6. The die-cast piece must be allowed to dwell for at least 15 seconds inside the mould after die-casting is complete.
7. The amount of gold used must not be too big, otherwise the metal will splash during die-casting.