As the needs and uses of industry have grown, so has the need for products that are both complex and of high quality. Different casting processes make it possible to make complex and precise products for a wide range of uses and needs.
To select the right casting method for your manufacturing requirements, it is essential to know the advantages and disadvantages of these methods. This article briefly overviews various casting processes and their pros and cons.
What Is Casting?
Casting is a way to make metal parts in the shape you want by pouring molten metal into a mold and letting it solidify and cool to room temperature. It can produce complicated and intricate parts, no matter their size. Casting can be used for mass production because it can make a lot of isotropic metal parts at once. Different types of casting use different materials and molds to produce the desired products.
Types of Casting Process
These are the five most common casting processes with their advantage and disadvantages:
Lost Foam Casting
The lost-foam casting method is similar to investment casting, but instead of wax, it uses a foam mold. Once the pattern is made, it is coated with a refractory ceramic by dipping, brushing, coating, or spraying. Then the molten metal is poured in the mold to make the product.
● Lost Foam Casting Process
This method can be used on many different materials, such as alloy steel, carbon steel, cast iron, ferrous alloy, etc. The lost-foam casting process makes things like pump housing, fire hydrants, valves, and fittings.
Advantages
● Casting with high accuracy
● Allows flexible design
● Clean production
● Suitable for mass production
Disadvantages
● Pattern costs are high
● Low strength causes the pattern to be messed up or broken.
● There are a lot of steps in making something, and it takes longer to get it to you
Pressure Die Casting
Depending on how much pressure is used, there are two types of pressure die casting. There are two kinds of die casting: low-pressure and high-pressure. High-pressure die casting is often used to make many parts with complicated shapes that need high precision. However, low-pressure die casting is a better casting method for making large, simple parts.
Non-ferrous metals and alloys like zinc, tin, copper, and aluminum are injected under high pressure into a mold coated with a lubricant. So, high pressure is kept up during the whole process of rapid injection to keep the metal from getting too hard. After the entire process is done, the casting and finishing are removed to remove any extra material.
● Pressure Die Casting Process
The way that the mold is filled is different for pressure die casting and gravity die casting. In pressure die casting, molten metal is injected under high pressure into a metal mold. The molten metal is then quickly cooled to make the needed product.
Advantages
● High accuracy and tolerance for size
● High productivity and a good product
● Less need for machining after casting
● Fast cooling of molten metal means faster production rates.
● Complete setup requires a large capital investment
● The process can go on for more hours before the die needs to be changed
Disadvantages
● The costs of tools are pretty high
● Only non-ferrous materials can be used
Plaster Casting
This process is similar to sand casting, but the mold consist of a mixture called "Plaster of Paris." Plaster has a low heat capacity and thermal conductivity, so it cools the metal more slowly than sand. This helps achieve high accuracy, especially for thin parts with a small cross-section. But it could be better for high-temperature iron-based materials.
● Plaster Casting Process
With the plaster mold casting process, it is possible to make both small castings of 30 grams and large castings of 45 kilograms.
Advantages
● Smooth Surface Finish
● It is cheaper
● It isn't easy to make complex shapes with thin walls
Disadvantages
● The plaster molding material may need to be changed out often.
● Not suitable for high-melting materials
● Longer cooling times
Sand Casting
Sand casting is a method that can be used to make parts out of any metal alloy, whether it is made of iron. It is used in factories to make many things, like engine blocks, cylinder heads, crankshafts, and other metal casting parts for cars.
● Sand Casting Process
The smooth surface of the mold is made from silica-based materials, such as sand, that have been naturally bound or made in a lab. The surface of the mold has two parts: cope (the top half) and drag (the lower half). Molten metal is poured into the pattern with a pouring cup, and then it is left to cool and harden into the final shape. Lastly, the final metal casting is finished by removing any extra metal.
Advantages
● The costs to make them are reasonable, especially if they are made in small quantities.
● Both ferrous and non-ferrous alloys can be cast.
● Recycling ability
● It is challenging to work with steel and titanium because they have high melting points.
Disadvantages
● Compared to other methods, this one needs to be more accurate.
● It's hard to use this method for products whose size and weight are fixed
● Rough surface finish
Centrifugal Casting
Centrifugal casting, also called "roto casting," is a way to make cylindrical parts in a factory using centrifugal forces. In this type of metal casting, the molten metal is poured into a spinning die that has already been heated. The high-pressure molten metal is spread out in the die with the help of centrifugal forces.
● Centrifugal Casting Process
Centrifugal casting can be done in three different ways:
● The true centrifugal casting process
● The semi-centrifugal casting process
● The vertical centrifugal casting process
Unlike true centrifugal casting, semi-centrifugal casting uses a sprue to fill the mold to the top. However, molten metal sticks to the sides due to continuous rotation in true centrifugal casting. On the other hand, vertical centrifugal casting uses directional molding, just like true centrifugal casting, and follows the same process.
Advantages
● Better process results and less waste
● The casting is dense and has almost no flaws.
● Making barrel and sleeve composite metal castings is easy with this method.
● It produces a unique shape
● There is no need for gates and risers
Disadvantages
● Centrifugal casting needs a lot of money.
● Need for skilled workers
Steps in Making Different Kinds of Castings
Most casting processes follow a few basic steps, such as making a pattern, making a mold, choosing and pouring metal alloys, and then finishing the part that was cast.
Pattern Making
To make a pattern, you need to know the mold's shape. Wax, sand, plastic, and even wood can be used for pattern-making.
Mold making
After that, there's a need to make different molds for casting. Sand, plaster, or a ceramic shell can be used to make a single-use mold. Each of them is made differently. Also, patterns made from wax or foam are burnt in a kiln.
Selecting the Suitable Metal Alloy
Ferrous or non-ferrous alloys are used to make metal castings. Alloys are chemical mixtures of elements with the best mechanical properties for their final uses. Where steel, malleable iron, and gray iron are all types of ferrous alloys. Non-ferrous metals, on the other hand, are things like aluminum alloys, bronze, and copper.
Melt and Pour the Alloy
After the metal alloys have been chosen, the metal is poured into the mold. The process works by putting a solid piece of metal over a crucible and heating it with an open flame or in the furnace until it melts. The molten metal can be poured straight from the crucible for small castings. But for larger castings, the metal may need to be moved into a larger ladle before it can be poured into the mold.
Finishing
After the casting has hardened, it is taken out, and the metal surface is polished. Also, finishing can include scrubbing or machining to eliminate waste material that is too big for scrubbing.
Ares Prototyping Die Casting Services
Choosing the proper casting process and expertise for your products is essential. At Ares Prototyping, we give you access to a team of professional engineers with a lot of experience with die casting, vacuum casting, and other casting services. The expertise of our working team allows us to advise you and answer any question you may have.
We also offer rapid online quotes for your parts by uploading a design file to our online quotation platform. You can be sure that we offer the best at prices in line with the market.
