Casting is the process of making things by pouring a liquid, like molten metal, into a mold and waiting for it to harden. Once the melted material has hardened, the solidified workpiece is taken out of the mold and put through several finishing steps or used as a finished product.
Casting is often used to make parts for cars, planes, and other vehicles, and it can also be used to make complex solid, and hollow shapes.
With the development of different casting methods, it is now possible to make complex, precise products for a wide range of uses.
The goal of this article is to explain these casting methods, their pros and cons, and how to choose the best method for your manufacturing needs.
Let’s delve into the details.
Types of Casting Process
Casting is a versatile manufacturing process with various methods, each suited to different applications and requirements. Here’s a brief overview of the main types.
- Sand Casting
- Permanent Mold Casting
- Die Casting
- Squeeze Casting
- Investment Casting
- Centrifugal Casting
- Plaster Mold Casting
- Lost-Foam Casting
- Vacuum Casting
Each method offers unique advantages, making them suitable for specific materials and design complexities.
Let’s get started with a detailed overview of each casting process.
Sand Casting
Casting has been around since at least 1000 B.C. However, sand casting holds the distinction of being the oldest known casting process. Sand casting has come a long way since it was first used. It can now make more complicated parts, use a wider range of materials, be more accurate, and design larger parts.
However, the fundamentals of metals remain relatively unchanged. After hundreds of years of improvement, sand casting is now the most common way to cast metal
Types of Sand Used in Sand Casting
Green Sand
Green sand, often known as clay, is the material used to make molds out of wet sand. As the metal is poured, the mold is still uncured. Green sand casting is efficient and cost-effective since the sand may be used again and again.
Because sand is so easy to shape, it often falls apart or moves during the casting process, which ruins the final product. However, the method is so secure that it has persisted for ages and is being utilized today.
Water glass or Sodium Silicate
You can also use sodium silicate to make the mold casting. When carbon dioxide is added to sodium silicate, it quickly turns from liquid to solid. Because of this, the sodium silicate begins to lose water. When a casting requires a cavity, this method is indispensable.
When used alone, sodium silicate forms a solid casting core. But combining it with other materials allows the cast to be broken and the core removed. The casting will be ineffective if the core gets stuck inside due to improper mixing.
Resin Sand
When the right proportions of resin and sand are combined and heated, the result is a smooth, solid mold. Castings made from a solid mold are less likely to be flawed, but they are also more expensive and take longer to make.
A resin sand mold takes more time to make than a green sand mold since the two materials have to be combined and burned separately. Even though the resin can be recycled, resin sand is more expensive and always needs to be replaced. Because of this, the total price tag will increase.
The Process of Sand Casting
If you’re looking for a casting technique, sand casting is it. The sand casting process is simple, but you need the right tools and know-how to make a perfect casting:
Creating a Mold
Making a casting mold is the first order of business. To create a sand mold, sand must be packed into both halves of the mold. Sand is compacted around a pattern that represents the finished casting’s exterior. The casting cavity is left after the pattern is taken away.
Preparing and Clamping the Mold
It is necessary to get the mold ready for pouring the molten metal after it has been created. Before trying to take the casting out of the mold, the surface of the cavity is greased to make the job easier. It’s important to consider the sand and metal you’re working with while choosing a lubricant. The mold is closed and clamped shut. Costs must be kept low and wastage avoided by keeping a tight seal between the two halves of the mold.
Pouring
The casting chamber is separated from the rest of the mold by a gating system, which may also be thought of as a gap. Molten metal is then poured into the sand mold through this gap.
Cooling
As soon as the molten metal is put into the mold, it will start to cool and harden. A casting takes its final shape when all of the cavities have been filled and the metal has solidified. The mold must cool for the specified amount of time before it may be opened.
Removing the Cast
Once the casting has been set for as long as it needs to, the mold can be broken and the casting can be taken out.
Trimming
While the casting is cooling, the material in the mold’s channels solidifies and bonds to it. This extra material will have to be taken off the casting, either by hand or with a trimming press. How long it takes to cut away the surplus will be determined by how big the casting is.
Sand Casting Mold
- Pattern: Used to create the mold cavity; commonly made from materials such as wood, plastic, or metal.
- Molding Sand: Different types of sand are used, including silica sand, zircon sand, olivine sand, magnesium sand, and bronze sand.
- Binders: Various binders are employed to hold the sand together, such as clay, water glass, vegetable oil, and synthetic resin.
- Sand Core: Primarily used to form internal holes and cavities within the casting, ensuring the desired internal geometry.
Sand Casting Materials
- Steel
- Aluminium Alloys
- Bronze Alloys
- Brass Alloys
- Graphite Iron, Grey Iron
Advantages of Sand Casting
- It is cost-effective in low-volume production, especially if smaller quantities are needed.
- It is useful for manufacturing large components.
- You can cast both ferrous alloys and nonferrous alloys.
- It produces metals that are easy to recycle.
- It is highly effective for high-temperature metals, such as steel and titanium.
Disadvantages of Sand Casting
- Sand casting has a relatively low degree of accuracy.
- It isn’t easy to use this method when the size and weight of the product are predetermined.
- This process produces rough-surfaced products.
Sand casting can be used in many industrial settings, like the mass production of engine blocks, cylinder heads, and crankshafts.
Common Sand Casting Products
- Electronic equipment
- Mining equipment
- Medical equipment
- Automobile parts
- Agricultural machines
- Engine blocks
- Cams, bushing, screws, nuts, bearings, and gears.
Permanent Mold Casting
Permanent mold casting refers to a molding method in which liquid metal is filled with a metal casting mold by gravity and cooled and solidified in the mold to obtain casting.
For mass production, the mold is made of a high-temperature material, like hot-work die steel or cast iron, that can handle being heated and cooled many times. Molds made of H13 steel can be used about 100,000 times, so this process is called permanent mold casting.
The Process of Permanent Mold Casting
Setting Up the Mold
The mold is heated to between 150 and 260 degrees Celsius (between 300 and 500 degrees Fahrenheit) before the metal is poured in. This helps the metal flow better and reduces flaws. The surfaces of the mold cavities are then coated with ceramic to make it easier to take out the parts and to make the mold last longer.
Assembling the Mold
There are at least three components to a mold: the two mold halves, any cores used to create intricate details, and the mold itself. Usually, these cores are fabricated from steel or iron. However, sand cores are also employed. The cores are placed in the molds and the halves are fastened together.
Pouring
A ladle is used to slowly pour the molten metal through a sprue located at the mold’s top. Through a series of runners, the metal is guided into the mold.
Cooling
Metal is poured into a mold and left there to cool and harden.
Cracking
When the metal has reached its final state of solidification, the two halves of the mold are separated and the cast is taken out.
Trimming
As the casting is allowed to cool, the metal (located in the runner) and the sprue solidify and become connected to the casting. The extra material will be trimmed off.
Permanent Mold Casting Mold
The materials used for permanent mold casting are generally ductile iron, 45 steel, and H13 steel, which have a mold life of about 10-15,000 times, 20,000 times, and 100,000 times respectively.
Permanent Mold Casting Materials
- Steel (Alloy, Stainless, Carbon)
- Copper
- Aluminium
- Cast Iron
- Magnesium
- Nickel, Lead, Tin
- Zinc, Titanium
Advantages of Permanent Mold Casting
Using casting from a permanent mold has many advantages for your undertaking. When using this technique, you may expect to obtain homogeneous, high-quality pieces.
- Disadvantages of Permanent Mold Casting
There are several disadvantages to permanent mold casting, but this is true of any method. Though some of them are quite small, they may all add up to make this a poor choice for your work.
- Permanent casting requires molds to be created, which can be a costly process if you require a handful of castings.
- To cast something, the metal mold must have a higher melting point than your casting.
- Highly detailed textured surfaces are impossible to achieve.
- It works best with medium to small castings and is impractical for larger ones.
Common Permanent Mold Casting Products
- Engine Components
- Housings
- Gears
- Wheels
Die Casting
Die-casting involves melting “low melting point” metals and injecting them into die-casting molds that have already been made. Die-cast sheet metal parts are very accurate, precise, and repeatable because they can be made in the same way over and over again.
Types of Die Casting
There are two types of die-casting methods.
Hot Chamber Die Casting
Die casting in a hot chamber is the best method for working with materials with low melting points, such as zinc, tin, lead, and magnesium alloys. However, if the alloy has a higher melting point, the pump could be damaged because the metal would touch the pump directly. So, a hydraulic system is used to melt the metal and force it into the die under pressure.
Cold Chamber Die Casting
Die casting in a cold chamber is ideal for working with materials such as aluminum, which have a high melting point. The high temperatures needed to melt such metals can damage the pumping system, so this process is perfect for them.
The Process of die-casting
The die-casting process has five distinct steps, but the whole thing rarely takes more than a minute. Below, we break down the procedure into its parts.
Clamping
Die-casting begins with the two parts of the mold being assembled and clamped together. Each die half is prepped with a thorough cleaning and lubrication before being clamped. Larger parts, more side cores, and more cavities all mean more time spent lubricating.
Plus, lubrication may be needed after every cycle or every two or three cycles, depending on the material. When the two halves are joined inside the machine, they are clamped and securely closed.
Injection
At the appropriate time, molten metal is moved to a chamber. It is subsequently injected into the die. How much the transfer method of a die-casting machine changes depends on how the machine is made. After the metal has been moved, it is injected at high pressure into the die.
The strong pressure keeps the molten metal inside the die, where it cools and hardens. Shot is the term used to describe the quantity of metal used to fill the die.
Cooling
The metal will begin to solidify and cool as soon as it is introduced to the die cavity. The casting is created when the metal fills the die’s cavity and hardens. So that the casting solidifies the right way, the mold won’t be opened until the required amount of time has passed.
When figuring out how long it will take for the molten metal to cool, the thermodynamic properties of the metal, the complexity of the die, and the casting’s maximum wall thickness are all taken into account.
Ejection
Once the casting has cooled, the die is opened and the casting is pushed out using an ejection mechanism. The casting envelope’s size is a key factor in estimating the ejection time.
Trimming
The die channels’ contents will bond to the casting as it cools. It is necessary to remove this metal from the casting, as well as any flash that may have formed.
Die Casting Mold
The die-casting tool is an important part of the die-casting process, which determines the shape and dimensional accuracy of the casting.
Die casting mold is a special kind of precision machinery with high cost and a long production cycle.Die Casting Materials
- Aluminium
- Lead
- Copper
- Zinc
- Tin
- Magnesium
Advantages of Die Casting Process
Die casting is an important technique in metal fabrication because it is inexpensive and easy to use. The die-casting process, however, offers additional benefits. Here are some that you should know.
- Complex parts can be created.
- It gives an avenue to manufacture multiple parts without needing to assemble them.
- There is a reduction in labor costs.
- The thickness of the wall can be varied.
- A rapid cycle time for production.
- Use of recyclable materials.
Disadvantages of Die Casting Process
- It is only suitable for metals with low melting points but not high ones.
- It is not suitable for large sheet metal components.
- Die cost is high.
Die casting can be used to produce aerospace parts, automotive parts such as gear, cylinders, gladhands, and industrial products such as compressor pistons, heat sinks, etc.
Common Die Casting Products
- Engine Components
- Housing Appliance
- Pump Components
- Home Appliances
- Mechanical products
- Automobile and ship products
Squeeze Casting
The liquid forging or squeeze casting process combines both permanent mold casting and dies forging into one step. During this process, the molten metal alloy is poured into a mold, and pressure is used to shape it. Metal parts are heated to melting temperatures and then extracted from dies.
The squeezing die casting process is a good way to make parts for automotive systems that are important for safety. Parts like nodes, chassis frames, brackets, and space frame joints are all examples of safety-critical parts.
The Process of Squeeze Casting
Coat the Die
A graphite coating is preferable.
Pouring
After coating the die, an accurate quantity of molten metal is poured into the bottom half of the die.
Close Die
After pouring the molten metal, close the die.
Apply Pressure
Apply a predetermined continuous pressure after closing the die. As the pressure is applied, the molten metal is forced into the available space of the die cavity and forms the required component.
Eject Casting
Afterwards, the pressure is withdrawn and the component is ejected from the die.
Squeeze Casting Material
- Aluminium Alloys
- Magnesium Alloys
- Stainless Steel
- Super Alloy
Advantages of Squeeze Casting
- It effectively eliminates internal defects, such as pores, shrinkage holes, and porosity.
- The roughness of the surface is low.
- Casting cracks can be prevented with it.
- It produces exceptionally strong components.
- There is no material waste.
Disadvantages of Squeeze Casting
- Geometric flexibility is limited.
- Its rate of productivity is low.
- The requirements for machining are high.
- It slows down the overall process due to the need for accurate control.
Common Squeeze Casting Products
- Bevel Gear
- Wheels
- Pistons
- Gear Blanks
- Super Alloy Discs
- Stainless Steel Blades
Investment Casting
Traditionally, investment casting refers to lost-wax casting. Several ancient cultures used it to create artwork, including ancient Chinese and Egyptian cultures. Nowadays, investment casting is used in various industries, including agriculture, construction, automotive, power generation, etc.
In this method, a liquid refractory material is “invested” into the mold pattern. This is why the method is called “investment casting.”
Investment casting is different from other ways of casting because liquid material is poured around the mold instead of into the mold cavity. In this first step, the liquid refractory material is injected into the mold.
The Types of Investment Casting
Foam
It can be used by engineers to create 3D models of their ideas. It is a way to make ornamental metal shapes, groups of shapes, and very complicated designs.
Water Glass
The shell’s binding agent is water glass rather than ethyl silicate. The method, which dates back to the 1950s, saves money on materials and shortens the time it takes to make things. Because the method, operation, and parameters are not as hard to understand, regular workers can use it, which increases output and efficiency.
Direct Investment
The first step is to carve the pattern by hand or with a machine to make a one-up version for lost wax treatment. This method can be used to make a prototype, make small batches of finished products, or figure out how big an object is.
Vacuum Casting
The process of vacuum casting involves drawing liquid casting material into a mold with a vacuum. The process is very different from injection molding, in which liquid materials are pushed into a mold.
The Process of Investment Casting
Making of Patterns
In most cases, the wax design is created as a single unit by being injection molded onto a metal die. Any pattern’s interior details can be formed with cores. Several patterns are joined together into a tree-like structure by use of a central-wax gating system. The gating system creates passageways for the molten metal to follow on its way to the mold chamber.
Constructing Molds
This “pattern tree” has a ceramic shell that protects the patterns and gating system. The shell is made when the tree is dipped into a mixture of tiny ceramic particles, covered with larger ceramic particles, and dried. Thus, the term “lost wax” casting refers to the process by which a wax mold is replaced with a hollow ceramic shell.
Pouring
The mold is heated to around 1000 degrees Celsius (1832 degrees Fahrenheit) in a furnace before the liquid metal is pumped in through the gating system. Although gravity is usually employed to accomplish the pouring process, a vacuum or pressure can also be employed.
Cooling
Once the mold is full of molten metal, it is left to cool and harden into the final casting’s form. Several factors, including material, mold thickness, and part thickness, affect how long a part takes to cool.
Casting Removal
The casting can be released from the mold once the liquid metal has cooled. Aside from the usual method of using water jets to break the ceramic mold, there are other ways to do it. After being cut out, the pieces are broken away from the gating system.
Finishing
The gates on the part are polished using a variety of methods, such as grinding and sandblasting. Heat treatment is another way to make the finished product harder.
Investment Casting Materials
- Stainless Steel
- Carbon Steel
- Low Alloy Steel
- Copper Alloy
- Aluminium Alloy
- Super Alloy
- Cast Iron
Advantages of Investment Casting
- This technology can produce thin walls, complex parts, and high-quality surfaces.
- It ensures that no post-casting machining is required.
- This casting method can cast stainless steel, thin steel, and other hard-to-melt alloys.
- It allows for castings with 90-degree angles since it breaks away from the shell mold.
- The products are of high dimensional accuracy.
- In the mold, there is an allowance for shrinkage.
Disadvantages of Investment Casting
- It requires labor to operate.
- It takes longer to produce.
- The cost of mold manufacturing is higher.
- Every casting cycle requires a new requirement for dies to create wax patterns.
Common Investment Casting Products
- Medical Equipment
- Turbine Blades
- Machine Components
- Firearm Components
- Golf Club Heads
- Pieces of jewelry
- Gears
Centrifugal Casting
With centrifugal casting, you can produce components with high material soundness. So, it is used in things that need to be very reliable, like jet engine compressor cases, hydro wear rings, and military equipment. Because the process needs less machining, it can also make complex shapes for less money than forgings and fabrications.
Casting is done centrifugally by pouring molten metal into a spinning die that has been preheated. The die may be oriented vertically or horizontally, depending on the part configuration.
When molten metal is poured into a spinning mold, it is spread out at a pressure close to 100 times the force of gravity. Combining this applied pressure with controlled solidification and secondary refinement produces superior-quality components.
When the spinning die begins to fill with molten metal, the denser metal is forced toward the wall. Sound metal solidifies from the outside in, while less dense material, like impurities, “floats” towards the outside.
After the cast has hardened, it is taken out of the mold and machined to get rid of any imperfections in the inside diameter. This leaves a structure that is free of flaws.Centrifugal Casting Types
True Centrifugal Casting
True centrifugal casting is the best way to make a part with a constant diameter and a fixed axis of rotation. A cylindrical mold is inside, and it spins at a predetermined rate around its axis.
When you pour molten metal through the center, it gets pushed outwards and onto the side of the mold by centrifugal force. When it sets, the casting can be removed from the mold. The amount of molten metal poured into the mold controls the casting’s final thickness.
This type of centrifugal casting has a direction of solidification because the cooling process moves from the outside to the inside.
Semi-Centrifugal Casting
Castings made via semi-centrifugal casting are solid, as opposed to tubular casts made via centrifugal casting. Multiple parts can be cast in a single centrifugal casting process because of the dense concentration of mold.
Rotational speed, pouring temperature, component diameter, pouring speed, cooling rate, and mold temperature all have an impact on the final casting’s quality.
Centrifuging
When using a centrifuge, mold cavities of different sizes and shapes are set at a fixed distance from the axis of rotation of the centrifuge. The liquid metal is poured into the middle of the mold, and then centrifugal forces force it into the cavity of the mold via the sprue into the runner.
The features of the castings may shift depending on how far they are from the spin axis, much like in true centrifugal casting. Jewelry, small bushes, and sleaves are just some of the small items that can benefit from this technique.
The Process of Centrifugal Casting
Preparing the Mold
A refractory-ceramic coating is applied in several stages to the cylindrical mold walls. After the mold has been prepared and fastened, it is rotated at high rates (300 to 3000 RPM), usually around 1000 RPM.
Pouring
Without using runners or any other sort of gating mechanism, molten metal is simply poured into the spinning mold itself. As the mold is filled, the centrifugal force causes the material to move closer to the mold walls.
Cooling
If you pour molten metal into a mold and keep rotating it, the metal will cool evenly and evenly distribute itself throughout the form. The outer walls of the mold cool off first, followed by the inside.
Removing the Cast
Stopping the rotation allows the casting to be taken out once it has cooled and been formed.
Finishing
The centrifugal force pushes the metal toward the mold walls, while the less dense impurities float to the interior of the casting. Consequently, the inner diameter of the part must be cleaned and smoothed using subsequent procedures like machining, grinding, or sandblasting.
Centrifugal Casting Materials
- Stainless Steel
- Alloy Steel
- Carbon Steel
- Copper
- Aluminium
- Nickel
- Cast Iron
Advantages of Centrifugal Casting
- There is an increase in yield and waste reduction.
- There is almost no defect in the casting, and it has high density.
- It is convenient to manufacture composite metal castings for barrels and sleeves.
- There is no need for gates and risers.
Disadvantages of Centrifugal Casting
- Investing in centrifugal casting is expensive.
- A skilled workforce is needed.
Common Centrifugal Casting Products
- Cylindrical Metal Pipes
- Cylinder Liners
- Railway Carriage Wheels
- Flywheels
- Automobile Axial Components
- Fuselage
- Axial Components for Marine Application
Plaster Mold Casting
Plaster casting is like sand casting, but the molds are made of plaster of Paris instead of sand. In plaster mold casting, gypsum can be combined with strengthening compounds and water to create a mold.
Patterns for plaster are usually made of metal or rubber, and they are coated with a substance that keeps them from sticking to the mold. Unlike metal molds, rubber molds are flexible enough to be taken off if the casting has reentrant angles, interior angles greater than 180°, or complex angles.
Molds made from this material are inexpensive, quick to create, reusable, more accurate, and easy to modify. Whenever a gap is found around a mold, plaster is used to fill it. When a plaster part is a cast, it usually cracks or forms defects, which requires replacing it with a new one.
Types of Plasters for Plaster Mold Casting
It is crucial to select the appropriate plaster for the task at hand when making molds from plaster. Different types of plaster dry with different amounts of holes, get stronger at different rates and shrink at different rates. Each of these criteria affects how various types of plaster are utilized. It’s crucial to know how plasters are used to make molds before beginning a molding operation.
Pottery Plaster
For those looking for a middle ground between affordability and longevity, pottery plaster is a solid choice. Very little smoothing of the mold is necessary, and the cured material has a compression force of 2,400 PSI. It’s porous enough to use with casting materials that need an absorbent mold to cure correctly.
Plaster of Paris
Plaster of Paris (PoP) is a cheap plaster that is easy to find and can be used for a wide range of creative projects. Since it cures a relatively weak compressive strength of 2,000 PSI, it is also commonly used for one-time molds. Because it is porous, you can’t use it with liquid casting materials like latex without first sealing it.
Gypsum Cement
Although it can be worked like plaster, gypsum cement dries to a significantly higher hardness and density. One hour after mixing, it reaches 1,000 PSI in compressive strength and 5,000 PSI once fully cured. The cost of gypsum cement is higher than that of pottery plaster, or PoP, but the durability it provides makes for a cast that may be reused again without compromising accuracy.
High-Strength Gypsum Cement
Some uses of gypsum cement are meant to reach very high strengths quickly, up to 4,000 PSI in just one hour. This is twice the strength that PoP reaches once it has reached its full curing potential. You’ll most often find these products at foundries, but you might also find them in factories where molds need to withstand hundreds of castings.
The Process of Plaster Mold Casting
Create the Mold
The mold is made by pouring a plaster mixture into the tool (die). After the mold has hardened, the cope and drag halves are taken off the tool, put back together, numbered, and left to dry.
Pour the Metal
The cavity is filled using a gravity pour approach. Casting quality is strictly monitored, as are all other variables. The metal’s temperature, the mold’s temperature, the cooling rate, the mold’s tilt, the riser’s size and placement, and the metal’s filtration are all factors to consider. To achieve the best possible results, we perform rotary degassing, make use of a continuous-melt furnace, and use a reduced-atmospheric testing system.
Break Out
The casting is revealed by breaking away the mold material once the metal has set.
Cleaning of Components
After that follows the process of removing any gates, chills, runners, or other small casting flaws. A “raw” casting is the result.
Machining
The casting process typically cannot accommodate, or is too expensive to include, the precise geometry required for high-precision applications, hence these are often machined by hand as a final step. To machine castings, we have a specific machining division. To guarantee the uniformity and accuracy of the machining of each casting, we employ technology with multi-axis capabilities and probe technology.
Advantages of Plaster Mold Casting
- With plaster casting, the finish on the surface is smooth.
- Compared with sand casting, it is more accurate in dimension.
- With thin walls, it is possible to cast complex shapes.
Disadvantages of Plaster Mold Casting
- There is generally a higher cost associated with this process than most casting operations.
- A limited number of applications are available for aluminum- and copper-based alloys.
- It may be necessary to replace the plaster molding material regularly.
- It is not suitable for materials with high melting points.
- The longer the cooling time, the slower the production rate will be.
Common Plaster Mold Casting Products
- Fitting Tools
- Ornaments
- Lock Components
- Fittings
- Valves
- Gears
Lost-Foam Casting
The lost foam casting process is an evaporative pattern casting technique. Pattern making with this method is very similar to investment casting, except that wax is used instead of foam in the casting process.
The foam pattern was introduced to metalworking in 1958. Even though this method of mold casting isn’t as common as sand mold casting or permanent casting, it still has a lot of benefits, especially when it comes to making complex and precise molds.
With the lost foam method, the pattern doesn’t have to be taken out before the casting because the foam evaporates when the molten metal is poured into it. That reduces the complexity of the pattern removal process.
The Process of Lost Foam Casting
Pattern Molding
Foam molding presses are typically used to create a foam design and gating system. The quantity of objects to be copied affects how the pattern is created. Most often, a closed mold is used to cast the pattern in polystyrene (2.5% polystyrene, 97.5% air).
Cluster Assembly
The cluster is formed by adhering the gating mechanisms and the pattern together.
Coating
This cluster is now given a coating of a permeable refractory material, and it is allowed to dry under conditions that are very tightly regulated. The pattern is surrounded by a thick, protective shell.
Sand Fill & Compaction
Now that the cluster has been dried and coated, it can be placed in a casting flask filled with loose, unbound sand and vibrated to achieve tight compaction, thus preserving the pattern or shape in the sand.
Pouring
The liquid metal is now poured over the gating system’s top, where it will be channeled into the cluster. The first pattern is instantly lost as the pouring molten metal engulfs it.
Breaking the Mold
After the cavity of the mold has been filled, it is left alone so that the molten material can cool and harden. After a casting has cooled and solidified, the shell mold and sand are broken apart and the gates and risers are removed, revealing the finished casting.
Finishing
The finished product can be heat treated or go through more finishing steps, just like with other casting methods.
Lost-Foam Casting Materials
- Nickel Alloys
- Aluminium Alloys
- Cast Irons
- Steel
- Stainless Steel
- Copper Alloys
Advantages of the Lost-Foam casting
- It has extensive casting precision.
- It provides flexibility in design.
- It helps provide a clean production environment.
- It is a cost-effective solution for high-volume production.
Disadvantages of the Lost-Foam casting
- Production of low-volume patterns involves high pattern costs.
- Patterns with low strength can be distorted or damaged.
- It has a longer delivery time due to many production processes.
Common Lost-Foam Products
- Cylinder Heads
- Differential Carriers
- Engine Blocks
- Crankshafts
- Transmission Cases
Vacuum Casting
The process of vacuum casting involves drawing liquid casting material into a mold with a vacuum. The process is very different from injection molding, in which liquid materials are pushed into a mold.
Vacuum casting offers significant advantages when parts are undercut or have fine details.
To begin with, 3ERP has to create a master model that can use CNC machining centers or 3D printers. A liquid silicone mold is then made by immersing the master model in liquid silicone.
The silicone mold can be used once the master model has been cut and removed. During this step, the mold is filled with casting resin, which is then vacuumed to remove air pockets and bubbles.
Once the resin part has cured in the oven, it is removed from the silicone mold and can be reused approximately 20 times.
The cast parts are exact replicas of the original master models. This solution can make quality small batches of parts in small batches.
The Process of Vacuum Casting
Model the Component
Making a computer model of the desired component is the first stage in making a vacuum-cast part. As with injection molding molds, the model is made following strict design criteria.
Creating a Mold Pattern
The master pattern for the mold is drawn out in 3D. The silicone molds used in the casting process are created from the master pattern, the primary mold. It’s a test run for long-lasting molds that can be cast in silicone, like metal or high-strength plastic.
Fabricating Silicone Molds
After a master pattern has been made, silicone molds can be made. Direct silicone molds are made from a casting box and the mold pattern.
The mold pattern is hung inside the casting box. The pattern has cores and inserts placed within it. Casting risers and gates allow liquid silicone to be poured into the mold, and the final mold can be easily removed by lifting the casing box.
Preparing Polyurethane Resin
Before casting, the polyurethane resin is heated and mixed with certain casting components, like colors and other agents. There are many different types of polyurethanes—each with its own unique material and structural features—to choose from.
Curing
When the solution has been completely set and the mold has been sealed, it is ready to be cast by being placed in a vacuum casting machine. No matter what kind of polyurethane is used, the casting method is the same, but the time and temperature needed may change. After the casting process is complete, the mold is allowed to continue to cure inside the casting machine.
Removing the Mold
Curing helps ensure that the cast will maintain its shape after being taken out of the mold. To fully remove the cast, the mold must be taken out of the machine after curing and then broken in half. It’s essential to take care when de-molding the cast so that it doesn’t get damaged. As the cast is taken out of the mold, excess materials like gates and runners are also taken out.
Advantages of Vacuum Casting
- It improves the porosity of die casting, its mechanical properties, and its surface quality
- It can be used to produce products with thin walls.
- There is the possibility of welding and heat-treating products.
- It can be produced at low volumes.
- You can finish hard tools with inexpensive methods.
- The early stages of the process reduce air pockets and bubbles.
Disadvantages of Vacuum Casting
- The cost of tooling is high.
- There is a short life expectancy for the mold used in the process.
- There are always problems with hollowness.
Common Vacuum Casting Products
- Plastic Bottles
- Tins
- Mobile Cases
- Sunglasses
- Pens
- Food Packaging
Final Thoughts!
Casting processes offer a wide range of methods to produce high-quality, precise components for various industries. By understanding the unique advantages of each casting technique, manufacturers can select the best approach for their specific needs, ensuring efficient production and superior product quality.
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