What Is A Pattern? What Are The Modifications Given To The Pattern? -->

What Is A Pattern? What Are The Modifications Given To The Pattern?

The pattern is the replica of the product to be made by a casting process. The patterns are used as the model for mold making. To meet the required dimensions of mold, the patterns are given certain modification when compared to casting product.

Functions of pattern

  • It used to produce mold cavity.
  • Gates and riser can be attached to the pattern so that it obtained in mold cavity automatically.
  • Pattern determines the location of the core. Core prints are given to pattern to support the core.
  • Locate the points to check the dimension of casting.
  • It used to establish a parting line of the mold.

Modification given to the patterns

Elimination of fine details: Patterns eliminate the fine details of an object that are very difficult to obtain by casting. For example, textures on the surface. The fine details are given to the object during subsequent operation of the casted product.

Patterns are given certain allowances known as pattern allowance: The main reason for allowance is that the casting includes the transition of phase (fluid to solid).  The different type of allowance given to the patterns includes shrinkage allowance, distortion allowance, draft allowance, etc.

Provision for core prints: These are provided to support the cores to make hollow parts of the casting.

🔗Types of pattern allowance and its reason
🔗Core prints, core location, core shift, core venting, and chaplets

Elimination details of pattern

It is not possible to get very fine details of the surface of an object by a sand casting process. In such cases, it is better to eliminate the fine details of the surface and provide machining allowance to the later surface finishing process. The details that eliminate during pattern making depend on the required accuracy, the type of casting and molding process and type of surface finishing process.

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