Patterns are essential tools used in metal casting to create the desired shape and structure of the final metal object. They serve as a replica or model of the intended part, and they are made from materials such as wood, plastic, or metal.
Each pattern has its own unique characteristics and is used in specific casting processes. The selection of the pattern type is important to ensure that the final casting is of the desired shape and quality. This is why I’ll be explaining the various types of patterns used to create molds for metal objects.
The function of patterns is to help reduce casting defects and produce an object with a smooth surface. Many kinds of patterns designs are typically made using materials like wood, metal, or plastic. Sometimes, wax patterns are required for specific applications. Wax patterns are used in the investment casting process.
The various kinds of patterns used in the casting process are single-piece patterns, two-piece patterns, gated patterns, multi-piece patterns, match plate patterns, skeleton patterns, sweep patterns, loose-piece patterns, follow board patterns, cope and drag patterns, segmental patterns, and shell patterns. They are tailored to specific casting requirements. Learn about casting tools here!
Now, let’s go deep to explain the different types of pattern and their uses!
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Types of Patterns in Casting
Below are the various types of patterns:
Single-Piece Pattern
These types of patterns are less complex in design and can be placed either in cope or drag. Single-piece pattern types are used in large castings, e.g., stuffing boxes for steam engines. This pattern is exactly like the desired object. A single-piece pattern is also known as a solid pattern.
This pattern is economical because it simply requires straightforward shapes and flat surfaces. It is perfect for straightforward operations and small-scale manufacturing. This is why industries where large objects are made make use of it.
Split or Two-Piece Pattern
These types of patterns are used for intricate casting. It is also known as the split-piece pattern. It has cope and drag as its major components. The cope component utilizes dowel pins and is aligned with the drag.
It contains two dowel pins and two dowel holes that are used to align and attach the two sections. The shape of the casting determines the position of the separation planes (irregular or flat). The use of split patterns can be found in the production of steam valves and weapons.
Loose Piece Pattern
These types of patterns are obtained when a solid piece has a backdraft or projections that may lie above and below the parting plane. One disadvantage of loose patterns is that the adjustment of the projected pattern can be done during ramming. This may slow down the casting process.
Gated Pattern
Gate patterns contain one or more loose patterns attached to gates and runners. Gated patterns are used in producing small castings in mass-production systems. Just as earlier mentioned, casings are produced in bulk using multi-cavity molds.
The molds are made by joining a few patterns and gates and giving them a single runner for the melting metal. These patterns are composed of metal, and gates and runners are created by attaching metal pieces to the pattern.
Match Plate Pattern
These types of patterns are similar to split patterns. The cope and drag portions are mounted on opposite sides of a plate (usually metal), which adhere to the contour of the parting surface. Gates and runners are also mounted on the match plate. The match plate pattern is used for a large number of castings, resulting in higher productivity.
The other sides of a match plate are made of wood or metal. The plates also support the runners and gates. This kind of pattern is utilized in machine molding. It is widely used in industry for casting a variety of items, it is expensive, precise, and high-yield. The casting of metals like aluminum frequently employs this style of pattern.
Sweep Pattern
In a sweep pattern, the cavity is created by rotating a wooden board along one of its edges. These types of patterns are used when a large amount of casting is required in a short time. Its components include a spindle, a base, and a sweep or wooden board. It is known for producing castings in a short period of time.
Cope and Drag Pattern
These types of patterns are similar to split patterns. They contain a cope and drag portion, each mounted separately on a match plate. They are used in the production of large castings. The process cannot be done by a single worker due to the weight of the molds. The cope and drag portions of the mold are made separately. This is because the entire mold is too heavy for one operator to lift.
Segmental Pattern
Circular castings like wheel rims, gear blanks, and other similar items frequently use this kind of pattern. These patterns consist of pieces that are moved to create each piece of the mold to create the full mold.
Skeleton Pattern
This pattern is just like a sweep pattern made of wooden frames that carry the shape of the part to be cast. A skeleton pattern is for large castings with simple geometrical shapes. It is also used in pit and floor wood processes.
Skeleton patterns are a suitable option for castings with simple sizes and shapes because of their large size. This type of casting pattern is expensive and immobile. Although it is not the most economical choice, it is quite good at getting rid of additional sand.
Shell Pattern
These types of casting patterns are produced in a mold that outlines the shape of the part to be coated. A shell pattern type is a great option for building structures with hollow interiors. It divides in half, then dowels the two pieces together.
Follow Board Pattern
These types of patterns are used as devices. It is used for various purposes in foundry work. It is made of wooden board. As split or solid patterns become more challenging, a follow board with a contour matching the precise geometry of one-half of the pattern is created. Learn about casting defects here!
That is all for this article, where I explained the different types of patterns and their functions. I hope it was helpful, if so, kindly share with others. Thanks for reading, see you around!
