PATTERN
*It is replica of the final object to be made. The mould cavity is made with the help of pattern.
*A pattern is one of the important tools used for making cavities in the mould into which molten metal is poured to produce a casting.
*Patterns are replicas of the casting required. It is similar in shape and size to the final product, but not
exactly.
TYPES OF PATTERN
1) Single piece pattern
2) Split piece pattern
3) Loose piece pattern
4) Gated pattern
5) Match pattern
6) Sweep pattern
7) Cope and drag pattern
8) Skeleton pattern
9) Shell pattern
10) Follow board pattern
Figure 1: Single piece, Split, Match-plate, Cope and Drag Pattern
1.SINGLE PIECE PATTERN
*This type of patterns are made of single solid piece without joints, partings (or) loose piece. Therefore, it is called solid (or) one-piece patter.
*It is made exactly into the desired casting to be produced with some allowances. It is used for making a few large size simple castings. The removal of pattern the sand is easy.
2. SPLIT PATTERN
*Split pattern is made into two parts. One part is to produce the lower half of the mould where as the other part is used to produce the upper half the mould.
*These two parts are assembled together in a correct position by pins called dowel pins.
*The line separting these two parts is called parting line.
*Split pattern are used for making spheres, cylinders, bearings and pulleys.
3. SHELL PATTERN
*Shell pattern is a hollow pattern. Its outer shape is used for making the mould. The core is prepared using the inner surface of the pattern itself. It is also known as block pattern.
*These pattern are usually made of metal. The pattern is made into two halves and joined accurately by dowels.
4.LOOSE PIECE PATTERN
*If a pattern is made from a single piece having projections (or) back drafts which lie above and below the parting line, it is impossible to withdraw it from the mould.
*After making the mould, the solid pattern is first removed and then loose pieces are removed without breaking the mould. This is called loose piece pattern.
5.GATED PATTERN
