The features of precision metal casting are that casting form is not affected when castings are taken out and casting form can be reused to produce large numbers of identical castings. Compared with sand casting, castings after precision metal casting have tinier grain structure and better mechanical properties. Pores are common defects in die castings but cannot be easily found in metal castings.
Currently, there are three major production processes involving metal casting: gravity casting, low-pressure casting and counter-pressure casting.
Precision metal casting molds are composed of the following parts:
1. Densener and feeding system, used together to accelerate solidification rate in relatively thick areas of castings.
2. Exhaust system, used for exhausting gas from cavity during mould filling of molten metal.
3. Pouring system, used for pouring molten metal into cavity at a specified speed.
4. Feeding system, used for feeding at relatively thick areas of castings during solidification process.
Generally speaking, production process of precision metal casting is very similar to that of sand casting because both methods are used to pour castings by gravity. To ensure proper pouring of castings, enough casting heads should be ensured. The proper position of pouring system, casting heads and densener should be ensured to meet the need of sequence solidification. As for sequence solidification, first of all, castings should be solidified towards casting heads from the position far from casting heads. It pouring system is not properly designed, insufficient pouring and shrinkage defects will be caused. And if feeding system and densener are not properly designed, too much shrinkage defects and too long mold closing time will be caused.