Mold material is the most important factor in determining the manufacturing method. Aluminum is difficult to cast and only certain aluminum alloys can be cast.
In general, aluminum alloys with high silicon content are most suitable for casting, while high-strength aluminum alloys cannot be cast, and mechanical processing methods are used. Copper beryllium alloy molds have good properties. Steel molds are mostly machined, and zinc alloys are easy to cast.
If the number of cavities is large, the cavity is complicated or irregular, the cavity tolerance requirements are low, the cavity volume is large, or the production lot is small, the casting method can be used to manufacture the mold. Casting molds are less expensive, but have lower durability and thermal conductivity than machined molds.
High-performance molds can be produced by some special casting methods. For example, the pressure casting method can reduce the porosity of aluminum and copper-bismuth alloys, and ensure high precision of the cavity. The machining methods for blow mold cavities mainly include milling and grinding.