Manufacturing Processes UES 102 PDF

Thapar Institute of Engineering & Technology – Patiala Manufacturing Processes UES 102 1 Casting Intro 2  Casting In the casting processes, a material is first melted, heated to...

Thapar Institute of Engineering & Technology – Patiala Manufacturing Processes UES 102 1 Casting Intro 2  Casting In the casting processes, a material is first melted, heated to proper temperature, and then poured into a cavity or mold that holds it in the desired shape during cool-down and solidification. 3  Casting Casting is a process in which molten metal flows by gravity or other force into a mold where it solidifies in the shape of the mold cavity. The term casting is also applied to the part that is made by this process. It is one of the oldest shaping processes, dating back 6000 years. The variety of casting processes use different pouring methods (gravity, vacuum, low pressure, or high pressure) 4 Casting 5  Capabilities and Advantages of Casting Can create complex part geometries Can create both external and internal shapes Some casting processes are net shape; others are near net shape Can produce very large parts Some casting methods are suited to mass production 6  Disadvantages of Casting Different disadvantages for different casting processes: – 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 7  Parts Made by Casting Big parts – Engine blocks and heads for automotive vehicles, wood burning stoves, machine frames, railway wheels, pipes, church bells, big statues, pump housings Small parts – Dental crowns, jewelry, small statues, frying pans All varieties of metals can be cast, ferrous and nonferrous 8 Two Categories of Casting Processes 9 Two Categories of Casting Processes 1. Expendable mold processes - mold is sacrificed to remove part – Advantage: more complex shapes possible – Disadvantage: production rates often limited by time to make mold rather than casting itself 2. Permanent mold processes - mold is made of metal and can be used to make many castings – Advantage: higher production rates – Disadvantage: geometries limited by need to open mold 10 Expendable mold processes 11  Overview of Casting Technology Casting is usually performed in a foundry Foundry = factory equipped for making molds, melting and handling molten metal, performing the casting process, and cleaning the finished casting Workers who perform casting are called foundrymen 12  Casting Steps Steps in casting seem simple: – Melt the metal – Pour it into a mold – Let it freeze 13  Casting Steps 1. Pour the molten metal into sand mold 2. Allow time for metal to solidify 3. Break up the mold to remove casting 4. Clean and inspect casting – Separate gating and riser system 5. Heat treatment of casting is sometimes required to improve metallurgical properties 14 Sand Casting Production Sequence 15