Making items by pouring molten metal into a blank, shaped space is known as metal casting. The metal then hardens and cools into the shape that this shaped mold has provided for it. If an item needs to be machined out of a solid piece of metal, casting is frequently a less expensive option. There are numerous metal casting techniques available. The use of metals, the length of the run, and the complexity of the casting all influence what kind of casting is most effective.
Demand for complicated and high-quality products has increased in tandem with a growth in industrial demands and applications. Fortunately, there are many casting methods that can create intricate and precise products for a range of uses and customer requirements.
Understanding the benefits and drawbacks of different casting techniques will help you choose the best process for your manufacturing needs. This is why in this article; I’ll be discussing the various types of casting processes along with their benefits and drawbacks
Types of Casting Process
The followings listed below are the common types of casting processes available in today’s industrial world:
- Sand Casting Process
- Gravity Die Casting
Pressure Die Casting
Sand Casting Process
Any metal alloy, ferrous or not, can be cast using the flexible casting method known as sand casting. It is frequently employed in industrial settings for mass manufacturing of components for automobiles made of metal casting, such as engine blocks, cylinder heads, crankshafts, etc.
An artificial or naturally-bonded sand-based mold is used in the procedure to create the mold’s flat surface. Cope (the upper half) and drag are the two components of the mold surface. (The lower half). Using a pouring cup, molten metal is poured into the design, where it is then allowed to harden and take on its final shape. Finally, surplus metal is removed so that the finished metal casting product can be finished.
Below are the benefits of the sand-casting process:
- Costs of production are quite low, especially for low-volume production
- Huge component fabrication
- Casting both iron- and non-iron-containing alloys
- Ability to recycle
- Processing of high-melting-point metals, such as titanium and steel
Below are the disadvantages of the sand-casting process:
- A lower level of accuracy than alternative techniques
- This strategy is challenging to apply to products with established dimension and weight specifications.
- Products produced by the method have a rough surface finish.
Gravity Die Casting
Gravity die casting, commonly referred to as permanent mold casting, produces metal and metal alloys using reusable molds consisting of metal, such as steel, graphite, etc. This kind of metal casting can be used to create many different items, including wheels, engine pistons, pipe fittings, gear housing, and gears.
In this method, molten metal is directly poured into the cavity of the mold while being pulled downward by gravity. The die can be angled to manage the filling for greater coverage. The items are created by allowing the molten metal to cool and solidify inside the mold. As a result, this method increases the prevalence of casting materials such as specific bronzes, cast iron, and alloys of lead, zinc, aluminum, and magnesium.
In contrast to conventional pressure casting procedures, these types of casting methods fill the mold from the bottom up. However, compared to sand casting, the method has a higher casting rate. But because expensive metal molds are used, the price is significantly greater.
Below are the benefits of gravity die casting:
- Because of the quick solidification, it produces goods with excellent surface quality.
- Products made using casting are highly precise and tightly toleranced.
- Reusable molds increase productivity and cut down on production expenses by saving time.
- The goods have improved mechanical qualities.
- Manufacturing of thin-walled products
Below are the disadvantages of gravity die casting:
- On occasion, the product gets a ding from the ejection mechanism used to remove the casting from the mold.
- Mold production expenses are higher.
- Casting complicated objects is challenging.
Pressure Die Casting
Depending on the pressure, there are two different forms of pressure die casting. both high-pressure and low-pressure die casting, to be exact. For mass production of complex geometries requiring fine precision, high-pressure die casting is more common. In contrast, low-pressure die casting is a better casting technique for the manufacturing of large and straightforward parts.
These types of metal casting involve the high-pressure injection of non-ferrous metals and alloys including zinc, tin, copper, and aluminum into a reusable mold that has been coated in lubricant. In order to prevent metal hardening, high pressure is maintained throughout the quick injection procedure. After the procedure is finished, the casting is extracted and finished to eliminate any unnecessary material.
When it comes to filling the mold, pressure die casting differs from gravity die casting. Whereas high-pressure injection of molten metal into the metal mold is used in pressure die casting. The needed product is subsequently made by quickly solidifying the molten metal.
Below are the benefits of pressure die casting:
- High dimensional tolerance and precision
- High productivity and excellent product quality
- Fewer post-casting machining operations required
- Molten metal cooling more quickly in order to increase production rates
- The process can continue for a longer period of time without replacing the die.
Below are the limitations of pressure die casting:
- High cost of the tools used
- Only non-ferrous materials are allowed
- Complete setup necessitates a large monetary outlay.
- It is not used for structural parts since it is difficult to assure that products have the desired mechanical qualities.
To create a disposable ceramic mold for investment casting, sometimes referred to as lost wax casting, a wax pattern is coated with refractory material and a binding agent. Molten metal is then poured into the mold to create metal castings. Investment types of casting are expensive and labor-intensive processes that can be used to create metal casting products such as gears, bicycle trunks, motorcycle discs, and replacement parts for blasting equipment in large quantities or in intricate castings.
Below are the benefits of investment casting:
- It can create components with thin walls, greater complexity, and excellent surface quality.
- Minimizes the requirement for post-casting machining
- Can cast alloys that are difficult to melt, such as stainless steel, thin steel, etc.
- The shell mold separates, allowing for castings with 90-degree angles.
- high items’ dimensional accuracy
- Molding allowance for shrinkage
Below are the limitations of investment casting:
- Costly to utilize
- Longer production cycle
- Higher mold manufacturing costs
- Wax patterns for each casting cycle must be made with a fresh die.
With the exception of the mold being composed of a substance known as “Plaster of Paris,” the plaster casting procedure is similar to sand casting. Plaster cools the metal more slowly than sand due to its limited thermal conductivity and heat capacity, which aids in achieving high precision, especially for pieces with thin cross-sections. However, high-temperature ferrous materials cannot be used with it.
In particular, the plaster mold types of casting process can be used to create small castings of 30 grams and big castings of 45 kilograms.
Below are the advantages of plaster casting:
- The finished surface is smooth
- The capacity to cast complicated structures with thin walls with greater dimensional precision than sand casting
Below are the disadvantages of plaster casting:
- Fewer uses for copper- and aluminum-based alloys
- It could be necessary to often replenish the plaster molding material.
- A substance that is less stable than sand and could have an impact on the entire process
- Increased cooling times, which affect production rates
- Incompatible with highly flammable materials
- The procedure is typically more costly than most casting operations.
Roto casting, commonly referred to as centrifugal casting, is a method for producing cylindrical pieces industrially using centrifugal forces. In this kind of metal casting, molten metal is poured into a hot spinning die. The high-pressure molten metal is distributed throughout the die with the aid of centrifugal forces.
There are three types of centrifugal casting: vertical centrifugal casting, semi-centrifugal casting, and genuine centrifugal casting. In contrast to true centrifugal casting, semi-centrifugal casting uses a sprue to entirely fill the mold. However, because of the constant rotation used in true centrifugal casting, the molten metal adheres to the sides. On the other hand, vertical centrifugal casting involves directional molding and the same procedure as true centrifugal casting, as the name implies.
Typically, rotational geometries like cylinders are produced through centrifugal casting. especially components such as cylinder liners, piston rings, clutch plates, bush bearings, etc. Additionally, pouring the metal into the mold’s center helps to minimize flaws like blow holes, shrinkage, and gas pockets. It is not, however, appropriate for all metal alloys.
Below are the advantages of centrifugal casting:
- Process yield improvements and waste reduction
- High-density and practically defect-free casting
- Making composite metal castings of a barrel and sleeve is easy with this method.
- There is no demand for gates and risers.
Below are the disadvantages of centrifugal casting:
- The cost of centrifugal casting is substantial.
- demand for skilled personnel
- manufacture of specific shapes
The distinction between investment casting and lost-foam casting is that the former employs wax for the pattern while the latter uses foam. Following the creation of the pattern, the refractory ceramic is coated using dipping, coating, spraying, or brushing. The finished product is then created by pouring the molten metal into the mold.
These types of casting can be applied to a variety of materials, including ferrous alloys, alloy cast iron, carbon steel, and alloy steel. The lost-foam casting process is particularly used to produce items like pump housing, fire hydrants, valves, and fittings.
High production precision and accuracy are just a couple of the benefits of lost foam casting. This technique, however, has a few drawbacks that make it unsuitable for low-volume applications.
Below are the advantages of lost-foam casting:
- High-quality casting
- Flexibility in design
- Excellent production
- Cost-effective for large-scale manufacture
Below are the limitations of lost-foam casting:
- High pattern costs for small manufacturing volumes
- Low strength results in pattern distortion or damage, which lengthens production procedures and delivery times.
The manufacturing of vacuum casting, as the name suggests, takes place under a vacuum pressure of 100 bar or less in order to exhaust gas from the mold cavity. In these types of casting processes, bubbles, and air pockets are removed by pouring molten metal into the mold cavity inside a vacuum chamber. The die cavity is evacuated under a vacuum to prevent gases from becoming trapped there during the metal injection process. The metal is then taken from the mold after being cured in a heating chamber.
Many industries, including those in the automotive, aerospace, electronics, marine, and telecommunication sectors, use the vacuum die-casting method. As a result, structural chassis components and vehicle body elements are some components produced by this manufacturing technique.
Below are the benefits of vacuum casting:
- Die casting’s mechanical characteristics, surface quality, and porosity should all be improved.
- Making thin-walled products
- It is feasible to heat-treat items and weld them.
- Ideal for small-scale manufacture
- There is no need for costly hard tool finishing.
- early stages reduce air pockets and bubbles
Below are the disadvantages of vacuum casting:
- High cost of tooling
- The process mold has a limited lifespan.
- Possibilities of hollowness
Squeeze casting, also known as liquid forging, is a hybrid metal forming method that combines die forging with permanent mold casting in a single stage. In this procedure, a predetermined volume of molten metal alloy is pumped into a die and shaped under pressure. The metal component is then heated to the melting point and removed from the die.
Squeezing die casting, in particular, is a possible casting method for safety-critical components in automobile systems. For instance, chassis frames, brackets, nodes, space frame joints, aluminum front steering knuckles, etc.
The advantages of casting and forging processes are combined in this kind of metal casting. For instance, the intense pressure used during solidification aids in preventing porosities and shrinkage. However, it is less common than other casting methods for mass production due to unique tooling needs.
Below are the benefits of squeezing casting:
- Removes intrinsic defects including pores, holes from shrinking, and porosity from shrinkage
- Minimal surface abrasion
- It could stop casting cracks.
- High-tensile elements
- There is no material waste
Below are the limitations of squeezing casting:
- Fewer design options for parts’ shape
- Decreased productivity
- Increased machining needs
- Requires precise control, which slows the process overall
It enables the consistent mass production of metal profiles having a fixed cross-section, as the name would imply. In the manufacture of steel bars, this kind of casting is frequently used. Additionally, semi-continuous casting products like billets, ingots, bars, etc. are produced by the vertical cast.
A surface of the solid metal can form on the liquid metal in the center of the mold by carefully controlling the rate at which molten metal is injected into the open-ended, water-cooled mold. Therefore, metal solidification occurs from the outside in. After this procedure is complete, metal strands can be constantly removed from the mold. Mechanical shears or moving oxyacetylene torches can be used to cut goods off at predetermined lengths. Continuous casting typically results in homogenous, reliable, and dense products.
Below are the advantages of continuous casting:
- Casting products come in a wide range of sizes, from thin strips to bigger slabs and billets.
- Lower expenses as a result of ongoing production
- Reduced waste of materials
Below are the limitations of continuous casting:
- Molds must be continuously cooled; otherwise, center-line shrinkage will occur.
- Casting only simple shapes with a fixed cross-section
- Huge amount of ground space and a significant initial investment
- Understanding die casting
- Understanding the difference between metals and non-metals
- List of best glues for metal
- 4 common types of metal casting processes
- Different types of sheet metal forming processes
In conclusion, casting is a versatile and fundamental manufacturing technique that is essential for the creation of a wide variety of goods in different industries. The many casting processes, such as sand casting, investment casting, die casting, and others, each have unique benefits, and the best one is chosen based on the quantity and complexity of the product to be produced, the amount of required raw materials, and other considerations.
Investment casting excels at making detailed and high-precision components, while sand casting is a cost-effective technique for producing huge, complex parts with a variety of materials. Die casting, which is frequently used in the automotive and electronics sectors, is perfect for high-volume manufacture of parts with constant quality and dimensional accuracy. Centrifugal casting and permanent mold casting both offer distinctive solutions for particular applications.
The choice of casting process depends on the particular requirements of a project. Each casting method has its own set of benefits and limits. In the end, the variety of casting techniques enables producers to effectively produce components and goods in a variety of sizes, forms, and materials, adding to the diversity and innovation discovered throughout industries globally. Casting techniques will probably change as technology and materials develop, opening up new opportunities for manufacturing in the future.
That is all for this article where the common types of casting are discussed. I hope it was helpful, if so, kindly share it with others. Thanks for reading, see you around!