Pros and Cons of different types of Casting Processes
There are various types of casting processes, each with its own set of benefits and disadvantages. Below, you will find the different casting processes, each with its advantages, disadvantages and recommended application.
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Investment Casting
Also know as lost wax casting, investment casting is a process commonly applied in cases where both solid parts and complex, hollow cores are required.
Advantages
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It is able to deliver close dimensional tolerances.
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Both ferrous and non-ferrous metals can be casted using investment casting.
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It delivers a good as-cast finish.
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With investment casting, complex shapes, intricate core sections, finer details and thinner walls are possible.
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It offers a flexibility in design and is a useful process for casting alloys that are difficult to machine.
Disadvantages
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Investment casting has a higher cost associated with it. In fact, it is more expensive than Sand Casting, Permanent Mold and the Plaster Casting process.
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When compared to other types of casting processes, investment casting needs a longer product-cycle time.
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There is a limitation on the size of parts that can be casted.
The advantages of this casting process overshadow costs when permanent mold and sand casting cannot deliver the desired complexity needed. Costs are also reduced by the quality surface finish investment casting delivers, reducing the cost of both machining and tooling.
You can learn more about this process, metals that can be casted, precision, tolerances and more by visiting our Investment Casting page.
Sand Casting
A process typically relying on silica-based materials, sand castings process involves finely ground, spherical grains tightly packed together into a smooth molding surface.
Advantages
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This is the least expensive process when producing small quantities (normally less than 100) and also boasts with the least expensive tooling.
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With sand casting, manufacturers are able to cast very large parts.
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Both ferrous and non-ferrous metals can be casted using this process.
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A low post-casting tooling cost.
Disadvantages
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Sand casting's dimensional accuracy is less than that delivered by other processes.
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This process requires large tolerances.
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The surface finish for ferrous casts delivered by this process usually exceeds 125 RMS.
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Castings produced with this proceed usually exceeds the calculated weight.
The advantages of sand casting process are more beneficial in cases where strength to weight ratios allows for it. Yielding a lower degree of accuracy, it does on the other hand offer low machining costs. For more information on this process, please visit our Sand Casting page.
Die Casting
Die casting involves the molding of materials under high pressure, and consists of Cold-Chamber Conventional Die Casting, Hot-Chamber Conventional Die Casting and Multi-Slide Hot-Chamber Die Casting for aluminum, brass, magnesium and zinc.
Advantages
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Die casting is able to deliver parts that has a good dimensional tolerance.
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Parts produced using die casting require a minimal amount of post machining.
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This casting process also delivers an excellent part to part consistency, ideal for large production scales.
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It is a cost effective process when used for a high volume production run.
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This process is suitable for metals with a relatively low melting point, such as aluminum, lead, magnesium, zinc and some copper alloys.
Disadvantages
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This process is only an economically sound option for a large production quantity, as the tooling costs for die casting are expensive.
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In this process, it is difficult to guarantee minimum mechanical properties and is thus do not function as structural parts.
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This process is also not recommended for hydrostatic pressure applications.
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There is a limit on the size of parts that can be casted. It is a suitable process for castings of about up to 75 pounds.
While it is an economically viable option for large production runs, die cast parts' mechanical properties cannot be assured, resulting in these parts not having a structural function. It is however a good process to opt for in cases where a large quantity of the part is needed, the parts produced will not have a structural function and in cases where parts will not be subjected to hydrostatic pressure.
For further information on this process, please feel free to visit our Die Casting page.
Permanent Mold Casting
Permanent mold casting is a process used in which permanent molds consists of mold cavities, machined into metal die blocks and appropriate for repetitive use.
Advantages
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This type of casting process is less expensive than die casting or investment casting.
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Casting delivered using this process are dense and pressure tight.
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Permanent mold casting is able to deliver a closer dimensional tolerance than sand casting is able to.
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The repeated use of molds are possible.
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It has a rapid production rate combined with a low scrap rate.
Disadvantages
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This process is only able to cast non-ferrous metals.
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Permanent mold casting has a higher cost of tooling than sand casting has.
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It becomes less competitive with sand casting in cases where three or more sand cores are required in the process.
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Because of the high tooling cost associated with permanent mold casting, it is only a financially viable option for high production runs.
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Limited to small castings with a simple design exterior.*
These types of casting processes are used in cases where parts are subjected to hydrostatic pressure and is perfect when casting parts that have no cores, a low profile and is part of a large production run (usually more than 300).
*Recent developments do allow for more complex castings, such the aluminum engine blocks and heads produced.
Learn more about our services and processes by visiting our Permanent Mold Casting page.
Plaster Casting
Plaster casting is a casting process with similarities to sand casting. Instead of using sand in the process, a mixture of water, gypsum and strengthening compounds are used.
Advantages
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Plaster casting is capable of delivering a closer dimensional tolerance than sand casting is able to.
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It delivers a smooth, as-cast finish.
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Casting larger parts using this process is less expensive that it would be when using investment casting processes.
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Intricate shapes with finer details are possible.
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Thinner, as-cast walls are also delivered by this casting process.
Disadvantages
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Plaster casting requires a minimum of a 1 degree draft.
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It is a more expensive process when compared to permanent mold and sand casting.
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This process may require the frequent replacement of plaster molding materials.
Though a more expensive process than most sand casting processes, it is a more economically sound option when a good surface finish quality is needed.
Back to Main Page: Metal Casting
Further Suggested Reading:
Metal casting, or foundry, consists of pouring molten metal into a mold cavity and then allowing that mold to cool and the metal to solidify. The process is used to manufacture objects of all sizes, from mere grams to thousands of kilograms, for medical, automotive, aerospace, and other industries.
Sounds simple, but there are many different methods of casting, all with unique characteristics.
Metal Casting Process Characteristics
Several features unite different variations of the metal casting process:
- The production process is high volume and low cost.
- Complex shapes may be cast, eliminating or minimizing the use of other manufacturing processes like machining, forging, and welding.
- It offers the ability to cast large-scale objects like pump housings or valves.
- Uniform material properties like machinability, bearing, and strengths are obtained on the cast object.
- Cutting weight reduction is obtained by allowing products to be cast as thin-wall casting.
Beyond these shared traits, the metal casting process features two main categories: expendable and reusable.
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- Reusable molds can be reused after the castings are ejected.
- Expendable molds are consumed during the casting process.
Most molds consist of a minimum of two pieces forming a cavity where the liquid metal is poured to produce the metal castings.
Different Methods Of Casting Commonly Used In Manufacturing
Sand Casting
Sand casting is reusable; in most cases, it uses permanent patterns to produce molds. Liquid metal is poured through orifices or into the mold to form the casting, and the casting has to cool down before being ejected.
The advantages of this method are that it can produce complex shapes, has a low cost, and is suitable for materials with poor elasticity. The disadvantages of this method are that surface finishes are usually rough and have an imprecise tolerance.
Shell Mold Gravity Casting
This method is expandable and uses chemically bonded sands that utilize polymeric or chemical glues to hold the sand grains together. It uses a permanent pattern in most cases to create the molds.
A heated pattern is placed over a sandbox with chemically bonded sands at the bottom in the shell mold process. The box is turned, so the bonded sand lays on the heated pattern forming the molds. The shell mold is then cured in a heated oven, allowing the properties to become uniform. Finally, the shell mold is removed, obtaining the final molds for casting.
The main advantages of this process are the casting surface finish quality, the ability to produce thin wall thickness, and complex castings. The main disadvantages of this process are the high production costs and casting prices, high pattern cost, and size and weight limitations of casting.
Low- & High-Pressure Die Casting
The low-pressure die casting method fills a mold and lets the casting solidify under pressure, and the metal is forced into the die from below low-pressure die casting.
The high-pressure die casting forces liquid or semisolid metal into a mold under high pressure and lets the casting solidify under pressure. Both methods are reusable.
The principal advantages of these processes are that the parts are relatively cheap, labor cost is reduced through the automatization process, and the final product has a high accuracy dimensioning. The main disadvantages of these processes are that the high melting-point metals are not suitable, long lead time, air trapped in the mold chamber affects the final product, and changes to parts and designs are usually time-consuming.
Investment Casting
The investment casting process commonly uses a wax replica or any polymer pattern to which a thick ceramic coating or refractory material is applied. The wax or refractory material is removed, the ceramic fired, and the molten metal poured into the cavity created by the pattern.
The main advantages of this process are that complex parts can be created using a single piece of investment casting, a smooth surface finish is achieved, dimensional precision is achieved, and wax material is reused. The main disadvantages of this process are the high cost due to specialized equipment, multi-step processes, and parts that are difficult to cast if they require small and deep holes.
Tilt Casting
The tilt casting process involves a connection between the casting crucible, the mold, and the coordinated tilting of both the crucible and the mold itself.
The main advantages of this process are automation, standardization, waste minimization, and scalability. Some disadvantages are the possibility of damaging moving parts and the difficulty of working with them in constraint spaces.
Centrifugal Casting
The centrifugal process consists of reusable molds. The main characteristic of this process is that a measured volume of liquid metal runs into a spinning mold. The melted metal is transported to the outer side of the mold due to the centrifugal forces created by the centrifugal forces.
The main advantages of this process are the high density achieved that results in increased mechanical strength product, inclusion, and lighter impurities, and no gates and risers are needed. The main disadvantages of this process are the inaccurate inner diameter of the product and the limitation of alloys that can be cast through centrifugal casting.
Lost Foam Casting
The lost foam casting process uses a foam replica coated with a refractory material which is then immersed in loose sand, creating a mold. The foam then evaporates when the melted metal enters the mold.
This process's main advantages are ease of use, the simplified procedure, and high dimensional accuracy. The main disadvantages of the lost foam casting process are that it is more expensive when compared with different methods of casting and creates a low-strength final product.
Vacuum Die Casting
This process uses a vacuum tank and pumps to extract the gasses in the mold cavity when the molten metal is poured into the hole.
The main advantages of this process are superior final casting mechanical properties and surface quality, reduction of cavity back pressure, and improvement of filling conditions. The disadvantages of this process are the difficulty of installation and sealing, leading to a higher cost and the need for specialized labor personnel.
Squeeze Casting
The squeeze casting process utilizes a two-part mold, a cope (top) and a drag (bottom). Molten metal is poured in the drag, and the cope squeezes the metal giving it a final shape.
The main advantages of this process are eliminating internal pores, shrinkage, and other defects, its ease of automatization, and its low surface roughness. The main disadvantages of the squeezing die casting process are the high setup cost, the long lead time, and the difficulty of modifying a design.
Choosing a Metal Casting Method
Comparing and evaluating the different methods of casting can be challenging. A cast can have multiple ways of manufacturing, and selecting the process will depend on the casting needed and its characteristics.
The best method is using a simulation casting software, where you can emulate and visualize the entire process, analyze the advantages and disadvantages of each approach, and gather information about the final product. Simulation casting software helps manufacturers reduce error, identify production problems, and analyze product characteristics.
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