Sagging of thin pattern due to ramming can be overcome by constructing a supporting block which may fit inside the pattern to serve as a support during ramming, such a pattern is called

Explanation:

Pattern:

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

Match plate pattern

• Split patterns attached on either side are known as the match plate patterns.
• In match plate pattern the cope and drags portions mounted on opposite sides of a plate (usually metallic) called the match plate. The gates and runners are also mounted on the match plate.
• Match plate pattern leads to higher productivity or mass production.
• Match plate pattern is used for small casting with higher accuracy.
• A match plate pattern is used in machine moulding.

Follow board pattern

• The pattern adopted for those castings where there is some portion which is structurally weak are likely to break by the force of ramming.
• This can be overcome by constructing a supporting block which may fit inside the pattern to serve as a support during ramming.

Built-up pattern

• Built-up patterns of two or more pieces.
• Patterns for special pulleys are built up of segments of wooden strips.
• These segments are made by cutting strips to the curvature required.

Lagged up pattern

• Cylindrical patterns e.g., barrels, pipes or columns are built up with lag or stave con­struction to ensure proper shape.
• Longitudinal strips of wood, called ‘lags’ or ‘staves’, are bevelled on each side and glued to the wooden end pieces called ‘heads’.