Casting is a very common manufacturing process to produce metal parts. It creates molds also called casting patterns where the manufacturers pour the molten metal next, and metal parts finished after the cooling of shaped metal materials.
During the casting process, the casting pattern is very crucial because of its effect on final products. Casting manufacturers should consider the casting pattern design completely according to the final products. There will have an expensive changing cost after casting.
What Is Pattern in Casting?
Generally speaking, the pattern in casting is the object for casting. Casting pattern shapes casting mold, and the mold creates metal parts, so the casting pattern is very crucial to the final parts. Therefore, the casting parts designer should consider more product details during the pattern design phrase
Making a casting pattern is not only shaping a mold cavity, accurate dimensions, scientific feeding system, and mold removing method should also be considered.
Key Considerations of Pattern in Casting
2 factors you should consider when you create casting patterns.
Materials of Casting Pattern
Your casting pattern materials should these properties:
- Lower cost and less weight: with the lower cost and less weight you are easier to find the balanced point of costs and returns.
- Resistance of water: choosing the material with resistance of 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 of your casting pattern, so you should consider the durable property of the material before you choose casting pattern materials.
- Versatile: various industries need casting patterns to create 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 easier.
Casting Pattern Allowances
Other factors like the type of casting pattern and the properties of casting metal should also consider. Therefore, there have some casting pattern allowances you should pay attention to when you make a casting pattern.
- Draft allowances: draft allowances creates a taper for removing casting patter 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 of 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. We call it a distortion allowance.
- Machining allowance: excess material in the finishing stage for compensating some loss materials.
Casting VS. Pattern
The main difference between pattern and casting is that a pattern is a tool while casting is a kind of process.
Casting: It is a kind of process that manufacturers pour the molten metal into a mold, where the material cools and solidifies. The final shape of products was decided by the mold cavity, while the shape of the mold should be considered, and that is where the pattern appears.
Pattern: Before you make a mold, you should design a pattern firstly. The pattern is the primary shape of the mold and finally, the product shapes according to the pattern.
10 Commonest Types of Patterns in Casting
We use 10 types of casting 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 have more details about each of the casting pattern.
Single Piece Pattern
Single piece pattern, also called solid pattern is the lowest cost casting pattern. It is very suitable for simple process, and small scale production and the large casting manufacturers prefer it because this kind of casting pattern make casting process just needing simple shapes, flat surfaces like simple rectangular blocks. One flat surface is used to separate planes.
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 surface, 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 which is hard to make. This kind of pattern includes 3 or more pattern which helps you achieve mold making.
Take the three-piece pattern as an example. The pattern is made of the top, bottom, and middle parts. The top part is cope, the bottom part drag, and the middle parts are called as 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 the manufacturing industry, and usually has an expensive cost, precise casting and high yield. And this kind of casting pattern is widely used in metal casting like aluminum.
Gate pattern can consist of one or more patterns into a molding pattern. It is designed for the mold which makes multiple components at one casting process. The gates are used to combine the different patterns, and runners to create a flow way for the molten materials. When the gates and runners have already attached, the patterns are loosing. This kind of pattern is expensive, and it is usually used for small castings.
Skeleton pattern is large in size, and it is a good choice for the casting which has the simple size and shape. This kind of casting pattern is expensive and not versatile. It is not the best choice from the aspect of economic, while is very efficient in extra sand removing. 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 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 with sand, and it also creates casting in a very short time, and it has consisted of three parts: spindle, base and sweep which 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 expensive casting pattern in castings.
Cope and Drag Pattern
Just like its name, cope and drag pattern has consisted of two separate plates, and it has two parts which can be separately molded on the molding box, and these parts create the cavity. This kind of pattern has a bit similar with the two-piece pattern and is usually used in large casting.
Shell pattern is a good choice to create hollow shaped structure. It parts along the center and dowels the resultant halves.
During the casting process, casting patterns are very important which decide the casting molds and the quality of castings. Before choosing the casting pattern, you should consider some factors, such as the size, shape of your casting products, and choose the best pattern for your casting business.
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