What is Sand Casting Process?
Sand casting (which is also known as sand molded casting) is a metal casting process in which sand is used as a mold material.
The reason why sand is used in mold preparation is that it is cheap and it has high refractoriness.
Sand Casting Process (7 steps)
The following steps are involved in the sand casting process.
- Place the pattern in the sand.
- Setup the gating system for the flow of metal.
- Remove the pattern to create a mold cavity.
- Pour the molten metal in the mold cavity.
- Wait for cooling and solidification of metal.
- Break the sand mold and remove the casting.
- Cleaning and inspection of casting.
Let me explain to you how the sand casting process is done.
You can see the schematic diagram for sand casting in the image below.
First of all the solid replica of the desired shape is manufactured, which is known as pattern.
After this, the molding sand is rammed around the pattern, and finally the pattern is removed to get the desired shape in the sand, which is known as mold cavity.
Sometimes, sand cores are also placed in the mold cavity to get the hollow castings as per requirements.
The runners are risers made in the sand, providing a path for the flow of molten metal.
The molten metal enters the mold cavity from the runner and the excess metal flows up in the riser.
Runners and risers act as a reservoir for the molten metal which adds the liquid metal to the mold cavity as the metal shrinks on solidification.
The metal is allowed to cool down and solidify.
The sand mold is broken down to remove the solid casting.
The surface of casting manufactured by this process is little bit rough, even after using a fine grained sand for mold preparation.
After this, the cleaning and inspection of casting is done through which we can come to know whether the final casting is properly manufactured or not.
Runners and risers are cut away from the casted component.
Machining is done on this casted component to obtain the smooth surface finish and accurate dimensions.
Almost 70% of metal castings are manufactured by using a sand casting process.
Now let me tell you some advantages and disadvantages (pros and cons) of sand casting process.
Advantages of Sand Casting
Advantages of Sand Casting process are mentioned below.
- Very large parts can be manufactured by using a sand casting process.
- Complex shapes which are difficult to manufacture by machining process, can be manufactured by using sand casting process.
- Sand casting is used for manufacturing the castings of different metals as well as alloys.
- Tooling cost and equipment cost is less.
- The scrap sand and metal can be recycled easily.
- Manufacturing is simple and easy.
Disadvantages of Sand Casting
Disadvantages of sand casting process are mentioned below.
- Casted component has poor strength.
- Porosity can be seen in casted components due to some residual gases.
- Surface finish obtained by the sand casting process is rough.
- Machining is required on casted component to get the smooth surface finish.
- Labour cost is high and the production rate is low.
Applications of Sand Casting
Applications of sand casting process are mentioned below.
- Sand casting process is used for manufacturing a wide range of components having complex shapes. The weight of casted component can be as light as few grams and heavy as tons.
- Smaller casted components include parts like gears, pulleys, crankshaft, propellers, connecting rods, etc.
- Heavy casted components include housing for large equipment, base for heavy machine, etc.
- Automobile parts like engine blocks, cylinder heads, transmission cases, engine manifolds, etc can be manufactured using sand casting process.
Sand casting process: Image by Krzysiulek, Public domain, via Wikimedia Commons