Different types of patterns in casting are mentioned below.
- Solid or single piece pattern
- Split or two piece pattern
- Match plate pattern
- Cope and drag pattern
- Loose piece pattern
- Gated pattern
- Sweep pattern
- Skeleton pattern
- Shell pattern
- Segmental pattern
- Follow board pattern
- Lagged up pattern
- Multi piece pattern
So these are the different types of patterns in casting (or foundry). Now let me give you short and simple information about each of these patterns (very quickly).
Let’s dive right into it.
#1) Solid or Single piece pattern
- Single piece pattern is the smallest of all the patterns.
- As the name suggests, this type of pattern is made up of single piece without joints, particles and loose pieces.
- For moulding with two or more patterns, one or more moulding boxes may be used.
- One has to prepare runners, risers and feeding gates for casting with this type of pattern. And hence this consumes more time.
- The single piece patterns are perfect for simple and large size casting.
#2) Split or Two piece pattern
- Sometimes, mould preparation is very difficult, and withdrawal of pattern also becomes difficult. In such cases, the split pattern or two piece pattern is used.
- Two split patterns are useful for the casting of unusual or difficult shapes. It is also easy to make the mold of difficult shapes by using two piece patterns.
- As the name suggests, two piece patterns are made up of two pieces. One piece is placed in the cope and another piece is placed in the drag, and the dowel pin holds both the pieces in a pattern.
- The surface which is formed at the center of both the patterns is known as parting line.
#3) Match plate pattern
- The match plate patterns are made up of metal and are generally used for mass production of small size castings.
- Match plate patterns are made in two pieces, like split patterns and to consist of a metallic plate known as match plate.
- As shown in above line diagram, the patterns are mounted on both sides of the match plate.
#4) Cope and drag pattern
- Some castings are heavy and large. For such castings, the complete pattern also becomes heavy and it becomes difficult to handle such heavy patterns.
- So for such castings, the patterns are made into two parts which are separately moulded in different moulding boxes.
- As the moulds are prepared, both the boxes are assembled which forms the complete cavity.
- One of the parts of the mould cavity is called cope and the other part is called drag.
- In cope and drag pattern, the entire casting is done in an assembled position (as a single piece). While in a two piece pattern, the casting is done into two pieces.
#5) Loose piece pattern
- In order to get some difficult shapes of casting, some patterns are made with loose piece which can be removed later when the mold cavity is formed.
- The loose pieces are the integral parts of the pattern only, but they are withdrawn back from the mold cavity after removal of the pattern. (See above image).
- It is little difficult to make a mould cavity using a loose piece pattern and it requires skilled labour.
#6) Gated pattern
- In gated pattern, the pattern is used to make multiple cavities, and these mould cavities are connected with each other using gates or runners.
- The molten metal when poured, gets distributed in each mould cavities and the desired casting is obtained in all the mold cavities.
- Gated pattern is used for mass production of castings.
#7) Sweep pattern
- Sweep patterns are generally used for preparing large size moulds.
- The sweep pattern is made by using a wooden sweep board called sweep.
- The outer end of the sweep board is designed such that it gives the shape of desired casting (see above image).
- Sweep patterns are used mainly for the cylindrical casting jobs.
- As shown in figure, the sweep board is attached with the spindle which is held in the vertical direction. After the vertical spindle is held, the moulding sand is rammed and finally the wooden sweep is rotated which gives the desired cavity in the sand.
#8) Skeleton pattern
- Sometimes the casting which is to be prepared is easy to manufacture, but it is very large in size, and only few number of castings are needed to manufacture. In such cases, it becomes very costly to prepare a large solid pattern for preparing a big mould cavity.
- For such reasons, the pattern having a wooden frame is prepared. In other words, the wooden frame (like a skeleton) is prepared which is then filled with moulding sand and rammed properly.
- Now, the extra unwanted sand is removed from the inside part of the frame (or skeleton), and finally the mould cavity will be ready.
- The image shown above is the skeleton pattern for a pipe.
#9) Shell pattern
- Shell pattern is mounted on a plate and it is parted along the center line such that it forms two accurate halves.
- Basically, these short bends are moulded and cast in pairs.
- Shell pattern is mainly used for pipe work and drainage fittings.
#10) Segmental pattern
- Segmental pattern is mainly used for the mould preparation of the larger circular castings by avoiding the use of solid pattern of exact size.
- The concept of segmental pattern is similar to that of the sweep pattern.
- The difference between sweep pattern and segmental pattern is that, the sweep pattern is given a continuous rotation to get the desired shape. While in a segmental pattern, the entire pattern is not used, but the portion of the pattern is used which generates the mould in parts.
- The portion of the pattern is pivoted at the center as shown in picture, and after preparing the part mould in one position, the segment is moved to the next position.
- In this way, the complete mould is prepared using a segmental pattern.
#11) Follow board pattern
- There are some patterns which have weak portions and these weak portions even break due to ramming force.
- In such cases, it is essential to support these weak patterns.
- So for supporting these patterns, a special type of pattern is used known as the follow board pattern.
- In a follow board pattern, the wooden board is used to support the weak pattern, so that it does not break due to ramming force.
- In simple words, the follow board acts as a seat for the pattern.
#12) Lagged up pattern
- Few cylindrical patterns like pipes, columns, barrels, etc are built using lags or staves to get the proper shape.
- The wooden strips called lags are fixed on each side of the heads as mentioned in the above picture.
#13) Multi Piece pattern
- Some castings have difficult shapes, and it is difficult to get the exact mould by using a single piece pattern.
- So in such cases, the pattern is splitted into different pieces so that it becomes easy to remove each part of pattern from the mold cavity.
- This type of pattern is known as multi piece pattern.
- Generally, 3 three molding boxes are required to make a multi piece pattern.