Casting GuideCasting is an engineering manufacturing process of pouring liquid materials (mostly metal) into a mold to create a die through the natural hardening process. After curing, the workpiece is removed from the mold for various finishing operations or used as a final product. Casting allows for the production of complex solid and hollow parts in a very efficient and fast way. The casting process can be used to produce different components for a wide range of industries, including automotive, aerospace, etc.
Types of Casting Processes
Sand casting is commonly used to produce large parts by filling molten metal into a cavity made of natural or synthetic sand. The cavity is formed by using a pattern usually made of wood or metal, the pattern having the same shape and size as the actual part. The prepared pattern is slightly too large, so the mold cavity is also slightly larger, which can compensate for the shrinkage of the molten metal during the cooling process. Sand casting usually relies on silica-based materials, such as synthetic sand or natural bonding sand.
The main advantages of sand casting are:
● Cheap production costs, especially for small batches
● Good for large components
● Supports ferrous and non-ferrous metals
● Low cost of post-casting tools.
However, sand casting has a lower accuracy compared to other casting methods and it can get tricky manufacture components with concrete dimensions and weight specifications.
Die casting involves the use of high pressure to mold materials into a certain form, usually non-ferrous metals and alloys. Parts with regular wall thickness can be manufactured at a much higher precision with die casting. During this process, the metal is forced into the mold at high pressure to ensure the production of the same parts, better surface finish, and improved dimensional accuracy. Die casting molds are expensive because they are made of hardened steel and because their production takes longer. This insertion under high pressure is very quick. This prevents any of the material hardens before the forming process. After the insertion, the component is removed from the mold and all waste is removed. Some parts produced by die casting do not even need to be machined after casting.
The main benefits of die casting are:
● Close size and shape tolerances
● Dimensional accuracy and uniform design
● Less post-casting machining
As with everything, die casting has also its disadvantages. It has relatively high tool costs, but this also makes it more cost-effective in mass production. It may also be difficult to ensure the mechanical properties of die-cast parts, which means that these products are generally not used as structural parts. Since the mold is usually two-piece, die casting is limited to products that can be removed from the mold without damaging the mold, as is done in other casting processes.
This is a casting technology with a wide range of industrial applications, including the casting of mechanical parts that are important for the durability of the final product. TV picture tubes, spherical glass objects, pipes, flywheels, and boilers are also produced by centrifugal casting. When pouring molten metal, the permanent mold rotates around its axis at high speed. The molten metal moves toward the mold wall under the action of centrifugal force and solidifies after cooling and produces small parts.
A traditional casting process for metals that are difficult to process. It is also used to produce parts that cannot be formed by conventional manufacturing techniques, such as turbine blades or aircraft parts that withstand high temperatures. This process provides excellent dimensional accuracy and surface finish. The pattern is made of wax or other molten material, leaving a cavity filled with the material of the parts produced. Disposable wax molds are used for each casting of investment casting or lost wax casting. The wax is directly injected into the mold, taken out, and then coated with refractory materials and adhesives, usually in several stages to form a thick shell.
The main advantages of investment casting are as follows:
● A high degree dimensional accuracy
● Good for thin-walled parts with complex geometries
● Supports both, ferrous and non-ferrous materials
● Relatively high-quality surface finish and detail
Permanent Mold Casting
Permanent molds are similar to die casting and centrifugal casting molds, especially the use of reusable molds made of steel or graphite and are commonly used in casting materials such as lead, zinc, aluminum and magnesium alloys, certain bronzes and cast irons. This is a low-pressure process and is usually cast manually using multiple molds on a turntable. As the molds rotate through the various stations, they are coated, closed, and filled in sequence, opened, and emptied.
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