Type of Patterns


The types of pattern a depend upon many factors like the bulk of casting type of molding process, number of casting required. The following types of patterns are community used.





1. Solid or Single piece Pattern


A single piece pattern is the simplest of the all the patterns It is made in one place and carries no joint, partner or loo pieces Although it is cheapest but it can use only upto limited extent because it's moulding involves large number of operations like gate cutting, providing runners and risers etc.



2.Two Piece or Split Pattern


Many patterns can not be made in a single piece because of the difficulties faced in moulding. To eliminate this difficulty and for castings of complex design or usual shape split patterns are used to form the mould.



 3.Multipiece Pattern


This type of patterns are used when casting having a more complicated design shape than above requires two parts to facilitate an easy moulding and without of pattern.


There pattern many consists of 3, 4 or more, number of parts, depending on their design.



4.Match Plate Pattern


These patterns are made in two pieces; one piece mounted on one side and the other side of the other side of a plate called match plate pattern.


The plate may carry only one pattern or a group patterns mounted in the same way on its sides.


These kinds of patterns are used for rapid production of small and accurate casting on a large scale.



5. Gated Pattern


To produce good casting, it is necessary to ensure that foll supply of molten metal flows into every part of the mould Provision for easy passage of the flowing metal in the mould is called gating and is provided in the gated patterns.


In gated patterns, a single sand mould carries a number of cavities. Patterns for these cavities are connected to each other by means of gate formers which provide suitable channels or gates in sand for feeding the molten metal to these cavities. A single runner can be used for feeding all the cavities. This enables a considerable saving in moulding time and a uniform feeding of molten metal. For small quantities, these patterns may be made of wood, but for large production, metallic patterns are preferred.



6. Skelton Pattern


When the size of the casting is very large but easy to shape and only a few numbers are to be made, it is in economical to make a large solid pattern of that size. In such cases partem consisting of a wooden frame and strip is made, called skelton pattern.


It is filled with sand rammed, and the surplus sand is removed by means of a strickle.



7. Sweep Pattern


For preparing moulds of large symmetrical castings, particularly of circular cross section, Sweep patterns are very helpful. 

It saves time, labour and material.


It consists of base suitable placed in sand called vertical sand and a wooden template called sweep.


The outer end of sweep carries the contour corresponding to the desired shape of casting.


The sweep rotates about spindle to form a cavity.




8. Pattern with Loose-Pieces


Introduction to Manufacturing Processes Some pattern usually single piece are made to have loose pieces in order to enable for their easy withdrawal from the mould.


When the mold is complete, the pattern is withdrawn leaving the piece in the sand, which are later withdrawn separately through the cavity formed by pattern.




9. Segmental Pattern


Segment patterns are generally applied to circular work such as rings, wheel rim gear etc.


They are some how like sweep pattern but the difference is sweep is given continues revolving motion to generate the desired shape, whereas a segmental pattern is a portion of a solid pattern it self and the mould is prepared in a parts by it.




10. Loam Moulding


It is a very different method of moulding.


In this, a rough structure of component is ade by hand using bricks and loam sand.


The sand is used is known as loam sand or loam martar.


Then the desired shape is given to the mode structure, with the help of strickle sweeps, hence pattern is not required.


After preparing the mould, it is baked to give strength. This method is used for producing large costing in very small number.


It enables saving time, labour and material because of pattern is avoided.


But not used widely because it takes time for preparing mould and skilled moulder is required.


It is used for producing parts like cylinders, round bottom kettles, gears huge belts etc.




11. Follow Board Pattern


A follow board is a wooden board used to support a pattern during moulding. It acts as a seat for the pattern. Such single piece patterns, which have an odd shape or very thin wall require a follow board.


Examples of such patterns are shown in figure. In the former case, the follow board is provided with a cavity corresponding to the shape of the pattern in which the pattern is seated for moulding. In the latter case, the follow-board carries a projection conforming to the inside shape of the thin-walled pattern to support it during moulding. If such a support is not provided, the pattern may sag or get broken, due to less wall thickness, during ramming.