Casting is a popular modern metal manufacturing method that involves molten material and a mold. Die casting and sand casting are two of the most renowned variants of the casting process. Here’s an extensive guide to die casting vs sand casting to help you choose the best method for your next project.
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Selecting one metal casting process over the other can be quite daunting without expert help. Sand casting and die casting each offer unique advantages and disadvantages, affecting your final project outcome. Ultimately, the right manufacturing method will depend on several key factors, such as:
Below is further insight into the key difference between sand and die casting.
The die casting process involves pushing or pouring molten material into a metal mold called a die. It is an excellent option for manufacturing products with high dimensional stability.
Here are some details on how die casting works, the best metals for the process, as well as its main advantages and disadvantages.
The first step in the die casting process is creating the mold. The die or mold has an internal cavity or core that matches the shape of your desired final product.
You can use CNC machining to create high-quality molds. In modern manufacturing, mold engineers rely on Computer-Aided Design (CAD) to develop digital models of the die and Computer-Aided Manufacturing (CAM) to create the final physical product.
These programs help simulate the finest details of the mold, such as:
After passing several simulations, the mold designer shares the mold specs and drawings with specialist toolmakers. These toolmakers then run trials and use CNC machining to ensure the final mold meets your project requirements. Apart from the cavity, industrial dies may also contain:
In this step, the molten material is injected into the die under high pressure, ensuring even distribution. You fill the mold cavity with molten metal under immense pressure, ranging from 1,400 psi to 26,000 psi.
This injection method is faster than gravity die casting, resulting in a more efficient filling rate. It allows you to develop intricate molds with thin walls and smoother surface finishes.
The cooling stage begins once the molten material fills the molds. Maintaining a controlled and uniform cooling rate achieves the desired microstructure. However, the molten metal needs sufficient time to solidify to prevent internal and surface defects.
Once the casting is complete, you can unclamp the mold from the casting. Depending on the presence of surface defects and your desired outcome, you then subject the ejected part to secondary finishing processes such as:
The die-casting process primarily uses non-ferrous alloys including:
Some key advantages of die casting over sand casting include:
However, this manufacturing method also has some drawbacks:
The sand-casting process uses expendable sand molds to help create complex metal products. Sand is inexpensive and can withstand high temperatures, making it suitable for casting metals with high melting points.
Silica sand is the most commonly used material. It often contains an added resin or clay binder to help maintain the cavity shape. Other common additives, such as coal dust and sea coal, minimize casting defects and improve mold strength.
Below are further details on the sand casting process, recommended material, and its main advantages and disadvantages.
The mold-making process starts by packing sand into each half of the mold. Sand is packed around a pattern replicating the casting’s external shape. Once you remove the pattern, you have a core that you’ll use for metal casting. If you wish to add internal features, you must create separate cores before forming the mold.
The time required to make the mold depends on:
You can prepare the mold by lubricating the cavity surfaces, easing the casting removal process. Then, you position the cavities and clamp the mold halves tightly together. This step is crucial to preventing material leakage.
After properly clamping the mold, you can pour the molten metal from its ladled container. This pouring process is either manual or automated. Pouring continues until every channel and cavity is filled. This occurs quickly to prevent premature cooling and solidification of any section of the metal.
Once it enters the core, the molten metal starts to cool and solidify, taking on the casting’s final shape. The required cooling time depends on the metal’s temperature and the casting’s wall thickness. If the molten material cools too quickly, the product may develop:
After the needed solidification time passes, you can break the sand mold open to free the underlying casting. This final step may involve shot blasting to remove residual sand from the part’s surface.
Sand casting accommodates a wide range of metals, making it a versatile choice for several applications:
Sand casting is a highly sustainable process ideal for prototype casting and low-to-medium volume production runs. Some advantages of sand casting over die casting include:
Sand casting isn’t always a viable option for all uses. It has several disadvantages:
Both die and sand casting are relatively fast and effective ways of casting metal products. So, how do you know which one of these methods is the best for your particular application?
Here are some key differences to help you choose between die cast vs sand cast.
1. Cost Breakdown: Which Method Is More Cost-Effective?
The cost of metal product manufacturing largely depends on your parts’ complexity and production volume. Die casting generally has more costly tooling expenses, and higher-grade materials are needed to withstand high-pressure casting. Despite being more expensive up front, die casting spreads the cost over high-volume production runs. This lowers the cost of production per part.
2. Surface Finish & Accuracy: Which Is Smoother?
Die casting produces a better surface finish than sand casting due to the molten metal’s high-pressure injection. Unlike sand casting, this process contributes to high dimensional accuracy, minimizing the need for further finishing.
3. Speed & Volume: Which Works Faster?
Die casting is designed for higher production speed and higher volumes. It is highly automated, with rapid injection cycles and efficient ejection systems. Meanwhile, crafting sand molds takes a much shorter time but requires remaking for every production run. This feature makes sand casting ideal for custom, low-production cycles.
4. Strength & Durability: Which Lasts Longer?
Die-cast products benefit from high-pressure injection, resulting in denser casting with good strength and stability. Sand-cast products are more prone to internal porosity, which weakens the part’s overall fatigue resistance. Luckily, sand casting allows for high strength, which results in the creation of sturdy metal parts.
5. Environmental Impact: Which Is Greener?
Die casting is highly controlled, producing less material waste from flashing defects. However, it needs more energy due to the high temperatures and pressure involved in melting and injecting the metals. Sand casting, on the other hand, generates plenty of material waste. Depending on the binder type and the melting practices, the process may also produce more emissions.
There are other unique considerations to factor in when you compare die casting and sand casting:
1. Design Complexity: Which Allows More Detail?
Sand casting can handle more complex designs and larger components than die casting. However, die casting provides greater speed and dimensional accuracy. Your final selection will depend on which parameter and product requirement you focus on.
2. Customization: Which Works for One-Off Parts?
Sand casting services are ideal for one-off production runs, as you break the mold to extract the final product. However, you can opt for die casting when using the mold for multiple runs.
3. Repairability: Can These Parts Be Fixed?
While some repairs are possible with die castings, sand castings are much more repairable. They have thicker walls and less precise tolerances, allowing you to use joining techniques like welding and brazing to fix sand casting defects. Die casting has tighter tolerances, and the high-pressure injection creates a denser, less porous structure.
Sand casting and die casting processes cater to separate project needs. While there may not be a clear winner in the die casting vs. sand casting discussion, the right option depends on your requirements.
As a premier sand and die casting manufacturing company, The Federal Group USA can help you with both of these methods. Contact us to find out more about the cost of die casting vs sand casting options for your manufacturing needs.
Owner of The Federal Group for 44 years, Robert is a serial entrepreneur and built his manufacturing business from scratch at the age of 26. He is an expert on all things forging, casting, and machining. On the weekends, he enjoys golfing, playing guitar, and spending time with family.
