Skeleton patterns are generally used for-

Concept:

Patterns

• A pattern is the replica of the casting to be formed with some modifications. These modifications are in the form of allowances.
• Patterns are of great variety because of their different designs, constructions, and methods of use. More commonly used types are
  • Solid/Single-piece pattern
  • Two-piece/Split pattern
  • Multi-piece pattern
  • Sweep pattern
  • Segmental pattern
  • Skeleton pattern
  • Shell pattern
  • Gated pattern
  • Loose piece pattern
  • Match plate pattern

Skeleton pattern

• The skeleton pattern is used for casting a very huge part.
• Instead of making a completely solid form, the pattern is made of a wooden frame and rib construction (skeleton) to form a partially exterior or interior outline of the casting so that a general contour and size of the desired casting may be produced.
• The ribbed construction is filled with clay sand or loam and rammed.
• The proper contour is made by using a template or stickle which removes excess sand out of the spaces around the ribs and also makes the proper contour.
• A skeleton pattern is made usually in two parts.

• A skeleton pattern for molding a large pipe with flanges at both ends shown in the figure above.
• The skeleton pattern is set on the compacted and leveled sand floor with its flat face.
• Its hollow portion are filled with sand and rammed and the final cylindrical shape to the pattern is given by using the stickle