Types of Pattern Pattern Allowances

PATTERN In casting, a pattern is a replica of the object to be cast, used to prepare the cavity into which molten material will be poured during the casting process

PATTERN REQUIREMENT Its size and shape is same with required casting. Strong and long life Simple in design Less in weight Less expansive During the work size and shape remain constant.

Types of pattern Solid Pattern Split Pattern Gated Pattern Match Plate Pattern Cope and Drag Pattern Loose piece Pattern Skelton Pattern Sweep Pattern Shall Pattern

Solid Pattern Solid pattern - A solid pattern is a model of the part as a single piece. It is the easiest to fabricate, but can cause some difficulties in making the mold. The parting line and runner system must be determined separately. Solid patterns are typically used for geometrically simple parts that are produced in low quantities.

Split Pattern

Gated Pattern

Match Plate Pattern

Cope and Drag Pattern

Loose piece Pattern

Skelton Pattern

Sweep Pattern

Allownces The allowances for accurate casting Because of Metal shrink in volume Cannot get good surface finishing Mold can expand when pattern out from mold Mold and casting can damage

Pattern allowance Shrinkage allowance Finishing allowance Draft allowance Rapping allowance Distortion allowance

Shrinkage allowance Metal shrink in volume when solidifying from liquid state

Finishing allowance The surface finish obtained in castings is generally poor dimensionally inaccurate

Draft allowance It facilitates withdrawal of pattern from mold Given an inclination of 2-3 degree so that while lifting the pattern

Rapping allowance Usually during removal of the pattern from the mold cavity, the pattern is rapped all around the faces, in order to facilitate easy removal. In this process, the final cavity is enlarged.

Distortion allowance During cooling of the mold, stresses developed in the solid metal may induce distortions in the cast. the pattern in the opposite direction of distortions

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