2. Types of Pattern Pattern Allowances

3. 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

4. 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.

5. 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

6. 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.

7. Split Pattern

8. Gated Pattern

9. Match Plate Pattern

10. Cope and Drag Pattern

11. Loose piece Pattern

12. Skelton Pattern

13. Sweep Pattern

14. 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

15. Pattern allowance Shrinkage allowance Finishing allowance
Draft allowance
Rapping allowance
Distortion allowance

16. Shrinkage allowance
Metal shrink in volume when solidifying from liquid state

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

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

19. 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.

20. 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

21. Thank You