Sand Casting Vs Die Casting

Modern manufacturing employs many types of casting processes. Each one has its own advantages and disadvantages and as such, different applications. Here we explore the difference between two casting procedures that are used extensively – die casting and sand casting – and how to choose between these two processes. 

What is die casting? 

Die casting refers to a high pressure process in which liquid or molten metal is forced into a mold. 

The mold, or die, is shaped to produce the wanted product. When the molten metal in the die cools and solidifies, the wanted product is ejected. The same cycle is repeated to manufacture large quantities of the item. 

Die casting is a quick process and thus, is one of the fastest ways to manufacture metal based products. 

Based on the type of machines, materials used and the process followed, these types of die casting processes are primarily used for manufacturing parts:

What is sand casting? 

As the name suggests, sand casting uses sand to create the casting molds. The process starts with the desired shape of the product being made out of a compatible material such as wood or plastic. This pattern is then placed into a top and bottom mold and sand packed tightly around the pattern. 

Once the sand is packed around the pattern, the mold is finalized and clamped together. Molten metal is poured into the mold and allowed to cool. 

When the metal cools and solidifies, the sand is removed via methods such as vibration or water jets. 

Since sand casted products do not conform to the mold with high dimensional accuracy, post processing such as polishing, sanding, and removal of excess metal is needed. The product is tested for quality after post processing. 

Applications of sand casting include engine blocks, hardware pieces and even furniture. While it is not high in accuracy, this method is a mainstay as the cost is very low compared to other casting methods. 

Differences between die casting and sand casting

While both die casting and sand casting are popular casting methods that are efficient, there are certain characteristics that will help you choose one over the other for your project. 

Dimensional accuracy

Die casting is able to create products with incredibly high dimensional accuracy. The precision of this process creates parts that are ready to use right out of the mold. 

Parts created with sand casting are usually far from desired tolerances. 

Lead time

Lead time refers to the time used to prepare the molding possess before casting begins. It is longer for die casting as there are more steps needed for the die casting process. This includes mold machining, and testing of the die. 

Sand casting molds can usually be made within a day if the desired pattern is already decided on. As such, it is suitable for projects that have small lead times. 

Out of mold surface finishing

Die casted parts have exceptional surface finishing due to the smooth inner surface of the mold. 

Sand casting parts will most likely have a sand particle texture imprinted on the out of mold surface. This, however, can be rectified with post production processes such as sanding and polishing.

Complexity of casting

With planning, both these casting processes can manufacture complex shaped parts. However, die casting is still the preferred choice when it comes to producing parts that are exceptionally complex. 

This does not mean that the sand casting process is lacking in this area, as engine blocks, which is definitely not a simple item, is often sand casted. 

Production volume

Die casting is a process that is best suited for high volume productions (more than 1000 castings). This is because of the large initial investment and effort needed. Unless there is a good reason, it is not recommended to spend so much on expensive dies if only a few parts are needed. 

Besides this, die casting is often used for high volume production because dies are reusable and die casting machines can be automated. This makes the whole process fast and simple. 

Sand casting does not require a big initial investment. However, as each part will need a new sand mold, it is often used for low volume projects. 

Price

Sand casting is the best way to go if the price is a concern. It is an easy, inexpensive and yet effective method to manufacture usable parts. 

The initial investment for die casting is high. However, the large investment is quickly offset when manufacturing large quantities. This is especially true as dies can be reused many times over. 

Conclusion

Although there are fundamental differences between these two processes, both die casting and sand casting have applications in manufacturing. If you need high volume, have sufficient lead time and do not have issues with the initial cost, die casting will save money in the long run. 

As such, die casting is probably the right choice over sand casting if you are looking to produce high volumes. 

This article is a part of our comprehensive guide on “Die casting: Process, Equipment, Uses, and More

If you have further questions on these processes or want more insight on the right casting process to use for your project, EKO Industries is an experienced company specializing in industrial manufacturing. 

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