Pattern in casting is a very common manufacturing process to produce metal parts. Molds also called casting patterns are where the manufacturers pour the molten metal in. Then metal parts are formed after the cooling of shaped metal materials.
Before the pattern-making process, the casting pattern design is very crucial because of its effect on final products. Casting manufacturers should consider the casting pattern design thoroughly according to the product requirement. Otherwise, there will be expensive replacement costs after casting. In order to avoid this situation, we need first to understand what types of patterns there are. Are there different types of patterns in different processes, such as investment casting, sand casting, and shell mold casting?
What is Pattern in Casting?
Generally speaking, the pattern is a replica or model of the final object that is to be created through the casting process. It serves as a template or mold that determines the shape, size, and often the surface finish of the finished casting part.
In the casting pattern-making process, it is not only important to consider the shaping mold cavity and accurate dimensions, but also the scientific feeding system, and mold removal method.
Key Considerations of Pattern in Casting
2 factors you should consider when creating different kinds of patterns.
Materials of Casting Pattern
Your casting pattern materials should have these properties:
- Low cost and lightweight: with lower cost and lighter weight you can balance costs and returns.
- Resistance to water: choosing the material with resistance to water protects your casting pattern from rusting. Casting patterns with this kind of material will have a long lifetime and produce high-quality patterns.
- Durable: durable material provides a long lifetime for your casting pattern.
- Versatile: various industries need casting patterns for the casting process, so the versatile property of casting pattern material is very important. It ensures the pattern can be used in many kinds of industries, and repaired easily.
Types of pattern allowances
Other factors like the type of casting pattern and the properties of casting metal should also be considered. Therefore, there are some casting pattern allowances you should pay attention to during the pattern manufacturing process.
- Draft allowances: draft allowances create a taper for removing casting patterns without any distortion. And the accurate angle of taper depends on the type of mold and surface, and the complexity of the casting pattern.
- Shrinkage allowance: usually the casting pattern has a bigger size than the mold, because most metal material contracts when it cools. The shrinkage allowance compensates for the cooling shrink of metal, and the precise parameter of the allowance depends on the metal material.
- Distortion allowance: casting patterns have a special design for avoiding the expected cooling distortion.
- Machining allowance: excess material in the finishing stage for compensating some lost materials.
Casting VS.Pattern
The main difference between a pattern and casting is that a pattern is a replica used to create the mold, determining the shape of the final metal part, while casting is the actual metal product produced by filling the mold with molten material, taking on the shape defined by the pattern.
Casting: It is a kind of process where manufacturers pour the molten metal into a mold, where the material cools and solidifies. The final shape of the products was decided by the mold cavity, and that is where the pattern appears.
Pattern: Before you make a mold, you should design a pattern first. The pattern is the primary factor affecting the shape of the mold and the final product shapes.
10 Commonest Types of Patterns in Casting
We use 10 different types of patterns in the casting process. Single-piece pattern, two-piece pattern, gated pattern, multi-piece pattern, match plate pattern, skeleton pattern, sweep pattern, lose piece pattern, cope and drag pattern, shell pattern.
There are more details about 10 different types of patterns.
Single Piece Pattern
Single piece pattern, also called solid pattern is the lowest cost casting pattern. It is very suitable for simple processes and small-scale production. Many large casting manufacturers still prefer it because this casting pattern can easily make castings with simple shapes and flat surfaces, such as simple rectangular blocks. One flat surface is used to separate planes.
Two-Piece Pattern
Two-piece pattern, also called split-piece pattern, is a common casting pattern for intricate casting. This kind of pattern has parting planes which may have flat or irregular surfaces, and the exact position of the plane was decided by the shape of the casting. There are two pieces of the split-piece pattern. One of the parts is molded in drag and another is molded in cope. And the cope part always has dowel pins. With the dowel pins, the two halves of split-piece pattern can be aligned.
Multi Piece Pattern
Multi-piece pattern is a good solution for complex designs that are hard to make. This kind of pattern includes 3 or more pattern pieces: the top, bottom, and middle parts. The top part is cope, the bottom part is drag, and the middle part is called checkbox.
Match Plate Pattern
Match plate pattern has a metallic plate to divide the cope and drag areas into the opposite face of the plate. This kind of pattern nearly has no hard work and can provide high output. It is widely used in casting manufacturing and usually has an expensive cost, along with precise casting and high yield. This kind of casting pattern is widely used in metal casting like aluminum casting.
Gate Pattern
Gate pattern can consist of one or more patterns into a pattern molding pattern. It is designed for the mold which makes multiple components in one casting process. The gates are used to combine the different patterns, and runners are to create a flowway for the molten materials. This kind of pattern is expensive but reliable, and it is usually used for small precision castings. Dawang Steel Castings mainly utilizes this gate pattern to produce high-quality investment casting parts.
Skeleton Pattern
Skeleton pattern is large in size, and it is a good choice for casting which has a simple size and shape. This kind of casting pattern is expensive and not versatile. It is not the best choice from an economic perspective, while it is very efficient in extra sand removal. If you want to use this casting pattern you should highlight the wood frames when you casting. The skeleton pattern is widely used in the industries of pit or floor welding.
Sweep Pattern
Sweep pattern uses a wooden board with proper size to rotate along one edge to shape the cavity. This kind of casting pattern creates a cavity in the vertical direction and the base of it is attached to sand. It also creates casting in a very short time, and it consists of three parts: spindle, base, and sweep which is also called wooden board.
Loose Piece Pattern
Loose piece pattern can help manufacturers remove one piece of solid pattern which is above or below the parting plane of the mold. This kind of pattern needs extra skilled labor work, so it is an expensive casting pattern in castings.
Cope and Drag Pattern
Cope and drag pattern consists of two separate plates, and it has two parts that can be separately molded in the pattern molding box, and these parts create the cavity. This kind of pattern is similar to the two-piece pattern and is usually used in large casting.
Shell Pattern
This method is favored for its ability to produce intricate, dimensionally precise castings with excellent surface finish. Shell patterns find common applications in industries requiring high precision, such as automotive and aerospace, due to their capacity to deliver fine details and efficient cooling during casting processes. Dawang Steel Castings utilizes this shell pattern to produce high-quality shell mold casting parts.
The above are about 10 different types of patterns in the casting process.
Conclusion
During the casting process, the choice of different types of patterns can often decide the quality and cost of final castings. Whether it’s a shell pattern for intricate precision or other patterns for investment casting and sand castings, understanding the advantages and applications of each pattern type is crucial for achieving the desired results in metal casting. Proper pattern selection contributes significantly to the overall efficiency and success of the casting process, ensuring that the final castings meet the required specifications and quality standards while also optimizing production costs.
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