Casting

Manufacturing Technology – II MI 232

Instructor – Inderdeep Singh

Spring 2011-2012

Foundry - Factory that produces metal castings
• Casting:
Process in which molten metal flows by gravity or other force into a mold where it solidifies in the shape of the mold cavity

Steps:
1. Melt the material (metal) 2. Pour it into a mold 3. Let it freeze

Refractory mold  pour liquid metal  solidify, remove  finish

Capabilities and Advantages
• Versatile: complex geometry, internal cavities, hollow sections • Versatile: small (~10 gms)  very large parts (~1000 Kg)
– Engine blocks and heads, machine frames, railway wheels, pipes, church bells etc.
– Dental crowns, jewelry, small statues, frying pans

• ECONOMICAL: little wastage (extra metal is re-used)

• ISOTROPIC: cast parts have same properties along all directions
• Some casting methods are suited to mass production • All varieties of metals can be cast, ferrous and nonferrous • High complexity with few steps (usually)

Disadvantages of Casting
• Limitations on mechanical properties • Poor dimensional accuracy and surface finish for some processes;

e.g., sand casting
• Safety hazards to workers due to hot molten metals • Environmental problems • Expensive and time-consuming patterns/molds/dies • Solidification issues: shrinkage, porosity, ~low strength, brittleness • Some methods require many steps

Casting
Pattern » Mold » Pour » Cool » Remove » Inspect

Types of Casting : Expendable Mold, Multiple Use Mold Sand Casting : Expendable Mold casting process uses sand as molding material

Requirements
• • • • • • Mold : single or multiple use Melting Process Pouring Technique Solidification Process Mold removal Clean, Finish, Inspection

METAL CASTING PROCESSES
Categories
• Expendable mold processes - mold is sacrificed to remove part • Mold (Sand, Shell, Vacuum, Expanded Polystyrene, Investment Casting, Plaster and Ceramic) – Advantage: more complex shapes possible –