gravity casting and die casting , based on the method used to pour the molten metal . Gravity casting, also known as free casting, involves the natural flow of molten metal into the mold cavity under the influence of gravity. Below, we'll delve deeper into the differences between sand casting, die casting, and gravity casting.
Sand casting is a traditional casting technique that primarily uses sand as the molding material. This technique typically utilizes gravity casting, but low-pressure casting or centrifugal casting can also be used when required. Sand casting has a wide range of adaptability and is suitable for the production of castings of various sizes and complexities, from small to large, simple to complex. In the past, sand casting typically used wood molds, but over time, to overcome the shortcomings of wooden molds, which are prone to deformation and damage, Xudong Precision Castings has gradually replaced these molds with aluminum or resin molds, which offer greater dimensional accuracy and longer service lives. Although these new molds are relatively expensive, their cost advantage over metal casting molds is particularly evident in small-batch production and the manufacture of large castings.
Metal casting is a modern process that utilizes heat-resistant alloy steel to create hollow casting molds. This technology supports both gravity casting and die casting. Metal molds offer exceptional durability and can be reused multiple times, producing a single casting with each pour of molten metal, significantly improving production efficiency. Furthermore, metal castings excel in dimensional accuracy and surface cleanliness. They are also stronger and more resistant to damage than sand castings.
Therefore, when mass-producing small and medium-sized castings of non-ferrous metals, especially when the casting material has a high melting point, metal mold casting is usually the first choice. However, metal casting also faces some challenges. The processing costs of heat-resistant alloy steel and hollow cavities are relatively high, resulting in the high cost of metal molds . Although its cost is lower than that of integral and die-casting molds, in small-batch production, the mold costs allocated to each product may still be too high and not very economical. In addition, metal molds are also limited by the size of the mold material, the cavity processing equipment, and the capacity of the casting equipment, and may not be able to cope with particularly large castings.
Die casting, short for metal mold pressure casting, is highly regarded for its high productivity . Die casting machines are key equipment for this process and are categorized into two types: hot chamber and cold chamber . Hot chamber die casting machines are favored for their high degree of automation and low material loss, but are limited by their heat resistance and are primarily suitable for casting low-melting-point materials such as zinc and magnesium alloys. High-melting-point materials such as aluminum alloys, on the other hand, require cold chamber die casting machines.
During the die-casting process, molten metal fills the mold cavity under high pressure and high speed, forming and solidifying under high pressure. However, this process also has drawbacks: the molten metal can trap air from the mold cavity and form pores within the casting during the filling process. Therefore, aluminum alloy die-castings are not suitable for heat treatment , while zinc alloy die-castings are not suitable for surface coating.
