Sweep Pattern In Casting
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| Sweep Pattern Diagram |
In the casting process, there are requirements to produce large-size casting, cope and drag pattern can produce such casting but cost, labour time, and material for pattern production is very high.
To solve this problem sweep pattern is used in the sand casting process which reduces time, labour, material, resources and material handling equipment by using a wooden board to create an impression in the sand.
I have explained below the sweep pattern used in the loam moulding process with diagrams, advantages, disadvantages, applications and differences between sweep and segmental pattern in the casting process.
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What is the sweep pattern in casting process?
A sweep pattern is a pattern designed to make a large axisymmetrical shape casting such as a bell in the mould cavity using a plane sweep wooden board.
This sweep board made of wood is rotated along its central axis with a pivot to create a mould cavity in loam sand as shown in diagram (a) below.
The sweep board is supported by the metal frame which is rotated 360 ℃ in the sand to produce products with grooves and ridges. The best material for making the sweep board is wood.
Shows diagram (a) below sweep board pattern below rotates in the mould and is supported by a spindle to make a mould cavity.
The diagram shows a sweep board that is to be swept in the sand to make a mould cavity in the sweep moulding process.
Sweep board is also called scrapper board as it scraps the loam sand away to produce the mould cavity.
This sweep pattern is an assembly of a rotating sweep board and a vertical straight spindle that is attached to the base of the sand mould.
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| (a) Sweep Pattern |
A mould cavity made from a sweep pattern is shown in diagram (b) below where molten metal is poured to produce sand castings such as bells, spindles and cylinders.
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| (b) Sweep Pattern In Casting |
The time required to produce symmetrical casting is reduced as the sweep board needs to just rotate around its axis to make a cavity in the sand.
The casting produced with this pattern is done in a pit or floor moulding by pouring molten metal directly into the sweep mould in the sweep moulding process as shown below in diagram (c).
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| (c) Pouring Molten Metal In Sweep Pattern Mould Cavity |
Shown below is the final casting diagram (d) made from a sweep pattern in casting.
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| (d) Sweep Pattern Casting |
Sweep pattern in the sand casting process eliminates making entire solid casting saving time and cost of pattern production.
This pattern has its own advantages and limitations which are explained below separately.
What are the types of pattern material used for sweep patterns?
Wood is the best material for making these patterns but metal is also used for higher accuracy, high volume production, durability, and moisture resistibility if the cost of producing casting is justified.
To achieve a better surface finish wood pattern is polished, sanded and coated with wax material.
What is the difference between a sweep pattern and a segmental pattern?
| Sweep Pattern | Segmental Pattern |
|---|---|
| 1) Loam sand is used for making mould while using this pattern. | 1) Loam sand is not used for mould-making while using this pattern. |
| 2) This pattern is used to produce casting with more depth and thickness than the segmental pattern. | 2) A segmental pattern is used for producing casting with lesser depth and thickness such as a ring. |
| 3) Cavity is made with one single sweep. | 3) Cavity is made not in one sweep but in incremental segments without complete pattern rotation. |
| 4) Casting products such as bells, pans and cores are produced using this pattern. | 4) Casting products such as rims and rings are produced using this pattern. |
Sweep Pattern Application
What are the applications and use of sweep patterns, list them with examples?
The application of sand casting made from this pattern can be seen in the decorative, automobile, and interior design industries.
Use of sweep pattern in the sand casting process and examples of products manufactured using this pattern are as follows:
- Kettles.
- Balusters.
- Metal cores.
- Cylinders.
- Circular pans.
- Ornamental railing.
- Flywheels.
- Products for ornamental purposes.
- Decorative fixtures.
- Bell shape casting.
- Wheels.
- Circular shape components.
Sweep Pattern Advantages
What are the advantages of using a sweep pattern in casting?
- The pattern is not expensive and can produce large-size casting without use.
- Pattern-making is easy and less time-consuming as the only board needs to be produced in the carpentry department.
- Pattern material is saved, for producing the same full-size solid pattern material required would be more.
- The time required for making mould cavities is reduced.
- Best for manufacturing prismatic and simple shape casting at a lower cost.
- Pattern assembly is not complex as it consists only of a vertical spindle and sweep board.
- Economical for producing large-size casting having symmetrical shapes and designs.
- The weight of the sweep pattern is low thus, easy to handle in the foundry.
Sweep Pattern Disadvantages
What are the disadvantages of using a sweep pattern in casting?
- Only contoured symmetrical casting can be produced which has a common axis.
- Limitation on creating complex shapes as the board only rotates along the axis reducing the possibility of making any sharp edges, cuts and corners in the final casting.
- Limitation of types of sand used, loam sand is the only best-suited sand for the sweep patterns.
- The productivity of sweep moulding is low as the process needs to be done by the operator manually.
- Not suitable for small-size casting as these castings can be easily produced using a match plate pattern.
- Pattern-making cost does not match for low volume production.
- Wooden material used for making wooden boards tends to change in dimensions when moisture is absorbed.
- Sweep moulding needs a skilled employee in the foundry for the sweeping operation of the sweep board in the mould.
Sweep Pattern In Casting MCQ (Multiple Choice Question & Answer)
1) Which of the following patterns is used for making larger symmetrical casting in less time, energy, resources, low pattern cost and using loam sand?
2) Which of the following parts are assembled to make a sweep pattern?
3) Which of the following pattern assemblies is similar to the sweep pattern in casting?
4) Sweep board used for making the pattern is generally made from which most common material to reduce the cost of pattern production?
5) Why loam sand is used for producing casting using a sweep pattern?
Sweep Pattern In Sand Casting Takeaway
The sweep pattern is one of the patterns among various types of pattern.
The process of using a sweep pattern to produce casting is called sweep moulding.
To make a casting, a sweep wooden pattern which is like a template is placed in the mould and the pattern is swept around the axis of the spindle in all 360 degrees removing all loam sand to form a symmetrical cavity for the sand casting process.
Once the cavity is produced by the wooden plank the gating systems are cut in the loam sand keeping mould ready for the pouring operation.
This pattern is the best pattern to produce large-size symmetrical curved shape casting with low pattern cost that cannot be produced by cope and drag pattern in the manufacturing process.
Stimulation software and CAD modelling is used today to produce accurate size sweep pattern and casting.