What is investment casting vs sand casting?

Investment casting and sand casting are two common casting processes in the manufacturing industry, each with its own characteristics and applications. The following is a comparison between them:

• Process:
  • Investment casting: Also known as lost - wax casting, it involves creating a wax pattern of the desired part. The wax pattern is then coated with a ceramic shell. After the shell hardens, the wax is melted and drained out, leaving a hollow cavity. Molten metal is poured into the cavity, and once it solidifies, the ceramic shell is broken away to reveal the finished part.
  • Sand casting: Sand casting uses a sand mold to shape the molten metal. The process begins with creating a pattern, which is used to form an impression in the sand. The sand is compacted around the pattern to create the mold. Cores can be inserted into the mold to create internal cavities. Molten metal is poured into the mold, and after solidification, the sand is removed to obtain the casting.
• Surface finish:
  • Investment casting: It offers a much better surface finish, with smoother surfaces and finer details. This is because the ceramic shell provides a more precise and smooth cavity for the metal to fill.
  • Sand casting: Generally results in a rougher surface finish compared to investment casting. The sand grains leave an imprint on the surface of the casting, and there may be some porosity and irregularities.
• Dimensional accuracy:
  • Investment casting: Allows for high dimensional accuracy, capable of producing complex shapes with tight tolerances. It is suitable for parts that require precise dimensions and close tolerances, such as aerospace components and high - precision mechanical parts.
  • Sand casting: Has lower dimensional accuracy compared to investment casting. The sand mold can deform slightly during the pouring process, and there may be variations in the size and shape of the casting. However, it is still suitable for many applications where lower precision is acceptable.
• Production volume:
  • Investment casting: Is more suitable for small to medium - volume production runs. The process is relatively expensive and time - consuming, but it is cost - effective for producing high - quality parts in limited quantities.
  • Sand casting: Can be used for both small and large - volume production. It is a more flexible process, and the tooling costs are relatively low for simple patterns. For large - scale production, automated sand casting systems can be used to increase productivity.
• Material compatibility:
  • Investment casting: Can be used with a wide range of materials, including ferrous and non - ferrous metals, as well as alloys. It is commonly used for stainless steel, titanium, and precious metals.
  • Sand casting: Is compatible with most metals and alloys. It is widely used for casting iron, aluminum, and bronze parts. However, some high - temperature alloys may require special sand formulations and processing techniques.
• Cost:
  • Investment casting: The overall cost is higher due to the more complex process, the use of specialized materials (such as the wax and ceramic shell), and the higher labor requirements. However, for parts with high - quality requirements, the cost may be justified by the reduced need for secondary processing.
  • Sand casting: Generally has a lower initial cost, especially for simple parts and large - volume production. The sand molds are relatively inexpensive to produce, and the equipment is more widely available. However, for complex parts, the cost of pattern making and core production can increase.