Investment casting and sand casting are reliable, cost-effective, quality manufacturing processes that allow for flexibility in budgets, timelines, and design. The pattern used to make casting molds lasts through thousands of impressions and years of use, producing the exact same measurements every time. Patterns also are easily replicable when needed.
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When manufacturers choose casting to mass produce complex parts, they have the option of choosing investment casting, which is also called the lost wax process, or a sand casting. The following is a breakdown of the two distinct processes and their advantages.
While investment casting is ideal for highly complex designs – it can cast 1/8-inch walls at the thinnest and work with both ferrous and non-ferrous metals – investment casting does have weight and size limitations. It is typically more costly than sand casting. It also requires longer lead times, however this is relative since Stainless Foundry & Engineering offers some of the lowest lead times in the industry.
Sand casting achieves net shapes within a quarter of an inch and has a rougher surface finish. Parts can be machined to achieve the exact tolerance and look for the finished part. Sand casting is more versatile with size and weight capabilities than investment casting.
Any manufacturer, prior to requesting a quotation, should consider all of the advantages of each process and decide in the end which process will yield a finished product to the desired quality at the lowest cost. An investment casting may cost more upfront, but when calculating secondary costs of sand casting it may be a wash.
If you are considering the design of a new part to be cast, or weighing the options of sand or investment casting, please contact us. Our sales and engineering team can assist in determining which process would work best for you.
The main concept behind investment casting has been used to cast metal for the past thousands of years, which was known as the lost wax casting. Although, the method has improved over time with technological advancement.
In this article, we have discussed the investment casting advantages and disadvantages.
Tight Tolerances: Investment casting can produce highly accurate parts with tighter tolerances, hence it is also called precision casting.
Material Reusability: You can recycle and reuse the mold material for the next casting cycle.
High-Quality Finish: The investment casting process can produce precise parts while maintaining an excellent surface finish. Therefore, the need for additional surface finishing is greatly reduced.
Complex Shapes: You can cast very complex parts using investment casting. Moreover, it doesn’t require any draft, unlike other casting processes.
Casting Size Variation: Investment casting allows manufacturing of various sizes and shapes. You can easily cast parts ranging from a tiny to a large model.
Material Diversity: It is possible to cast almost any metals and alloys of varying melting points, for instance, steel, aluminum, bronze, cobalt, brass, and others.
Longer Casting Cycles: The process involves a lot of steps. Therefore, each casting cycle takes much longer to complete.
Quite Expensive: Investment casting is quite costly compared to other processes. This is especially true when dealing with a low volume of production.
Labor Intensive: As the process is complex and involves a lot of steps, it is quite labor-intensive. So, the labor cost is high for precision casting.
Difficult to Cast Cores: It is difficult to cast any parts that require cores. Very smalls holes would be challenging or impossible to cast using the investment casting process.
Investment casting is a complicated process with a lot of steps. Moreover, many factories do most of the process manually. So, it is common to have some defects in the parts if not handled carefully which can offset the investment casting advantages.
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We have discussed some common defects of investment casting below,
Shrinkage Crack
it is possible to get shrinkage cracks when ceramic shell mold will restrict molten metal from contracting during the cooling or solidification process. Irregular shapes, rough holes may form due to this.
Porosity
Porosity can severely impact the quality of the parts. Sometimes air entrapment occurs during the pouring or casting of molten metal. Without the proper precautions, It can also form during the cooling process.
Inclusions
It is the inclusion of other materials into the casting. A very common form of inclusion defect is refractory material getting entering the wax model through unintended cracks.
Misrun
Misrun is a very common type of defect. It occurs if the investment casting mold isn’t filled by the molten metal. It usually happens if the metal starts solidifying during pouring, and the mold or metal is too cold.
Deformation
Sometimes deformation in the casting may occur during the solidification process. This type of defect may happen due to shrinkage stress.
Cold Shuts
When molten metal entering two streams inside a mold fails to merge properly, it is known as a cold shut. It usually happens due to the cooling of the metal streams before they meet each other.
Despite the high expenses involved, Investment Casting is a very popular casting process. However, companies will choose the cheapest possible solution that meets their requirement. That limits the application of precision casting to certain scenarios.
One of the investment casting advantages is that it can cast almost any material. However, manufacturers mainly use ferrous metals, and metals with a very high melting point. While they use die casting for non-ferrous metal casting parts.
Because other popular casting techniques such as die-casting use steel molds to cast other metals. It is not possible to die-cast steel as it would require a mold built with a material of a higher melting point than that of steel.
One could also opt to machine a bar stock. But, it is only practical for prototyping or production of a small volume of parts. Investment casting would provide a much cost-effective solution for medium to large volume production of high-strength parts.
Industries that have a demand for high strength and precise parts would go for investment casting. There are a lot of investment casting manufacturers in China as well. Currently, it is popular in many industries including,
These industries have a high demand for precision casting parts. Investment casting is commonly used to manufacture automobile parts, and turbines for ships and aircraft. Firearms production has also focused on investment casting to reduce the manufacturing cost. Moreover, the medical industry has a high demand for precision parts, thus making the investment casting process a good solution.