Course Content

Foundry (Moulding and Casting operations)

1. Perform mould preparation for solid bearing

2. Perform mould preparation for flange coupling

3. Perform mould preparation for split bearing

4. Perform mould preparation for connecting rod

5. Perform mould preparation for V-pulley

6. Perform mould preparation for gear pulley

Turning Operations

1. Perform plain turning operations

2. Perform step turning operations

3. Perform taper turning operations

4. Perform collar turning operations

5. Perform knurling operations

6. Perform facing operations

Welding Operations

1. Layout of beads

2. Perform lap joint

3. Perform butt joint

4. Perform T-joint

Introduction about the Fabrication Lab Practice

The foundry process, also known as metal casting, is a manufacturing method used to create metal objects by pouring molten metal into a mold. After the metal solidifies, the casting is removed and undergoes finishing operations. A foundry is the factory where this process takes place.

The Foundry Process

The foundry process is a cornerstone of the manufacturing industry, producing everything from automotive parts to complex machinery components. It typically involves these steps:

• Pattern Making: The process begins with creating a pattern, which is a replica of the final object to be cast. Patterns are made slightly larger than the final product to account for metal shrinkage during cooling. Common materials for patterns include wood, metal, and plastic.

• Mould Preparation: A mould is created using the pattern. The mould contains a cavity that is a negative impression of the pattern. A cope is the upper half of the mould, while the drag is the lower half. The sand is packed around the pattern inside a flask (a box-like frame) to form the mould cavity. Cores, which are separate parts placed within the mould, can be used to create internal cavities or features in the final casting.

• Melting and Pouring: Metal is melted in a furnace to a molten state. This process often involves refining the metal to remove impurities and adjusting its chemical composition. Once the metal reaches the correct temperature, it is poured into the mould cavity through a channel called a sprue.

• Solidification and Cooling: The molten metal fills the mould cavity and cools, solidifying into the shape of the casting. As it cools, the metal shrinks.

• Shakeout and Finishing: The solidified casting is removed from the mould, a process called shakeout. For sand moulds, this often involves breaking the mould apart. The casting is then subjected to finishing operations, such as removing excess material like the sprue and runners (the channels that guided the molten metal).

Mould Preparation

Mould preparation is a critical phase of the casting process. The type of mould used depends on the metal, the complexity of the part, and the desired production volume.

• Expendable Moulds: These moulds are used only once and are destroyed to retrieve the casting.

  • Sand Moulding: This is the most common and versatile method. The mould is made of sand mixed with a binder (like clay and water) that holds its shape. Green sand casting, which uses moist sand, is a popular sub-type.

  • Shell Moulding: A mould is made from a thin shell of resin-bonded sand, which provides better dimensional accuracy and a smoother surface finish than traditional sand casting.

  • Investment Casting (Lost-Wax): A wax pattern is created and coated with a ceramic slurry. The wax is then melted out, and molten metal is poured into the resulting ceramic shell. This process is excellent for producing intricate, high-precision parts.

• Permanent Moulds: These moulds are made from metal or other durable materials and can be reused for many castings.

  • Gravity Die Casting: Molten metal is poured into a reusable metal mould under the force of gravity.

  • Pressure Die Casting: Molten metal is forced into a metal die (mould) under high pressure. This is a very fast and efficient process for high-volume production of non-ferrous parts.

Turning Operations on a Lathe

After a part is cast, it often needs additional machining to achieve its final dimensions, surface finish, and tolerances. A lathe is a machine tool that rotates a workpiece against a cutting tool to remove material. The primary operation performed on a lathe is turning, which reduces the diameter of a cylindrical workpiece.

• Straight Turning: This is the most basic turning operation, where the cutting tool moves parallel to the axis of the workpiece to create a cylindrical shape with a uniform diameter.

• Taper Turning: Used to produce a conical surface by either setting the tool at an angle, offsetting the tailstock, or using a special taper turning attachment.

• Facing: The cutting tool is moved perpendicular to the axis of rotation to machine a flat surface on the end of the workpiece.

• Parting (or Cutting Off): A thin tool is used to cut off a finished part from the main workpiece.

• Grooving: A tool is fed into the workpiece to create a narrow, recessed channel or groove.

• Boring: An internal turning operation that enlarges or refines a pre-existing hole.

• Knurling: Creates a textured pattern on the surface of the workpiece to improve grip.

Welding Operations

Welding is a fabrication process that joins materials, typically metals, by fusing them together with heat, pressure, or both. In the foundry industry, welding is primarily used for repair and upgrading of castings.

• Casting Repair: Castings can sometimes have minor defects like porosity, sand holes, or shrinkage. Instead of scrapping the part, foundries use welding to fill these defects. The defective area is first excavated to sound metal, then a welding process is used to add filler material, and finally, the repaired area is ground smooth.

• Common Welding Processes:

  • Shielded Metal Arc Welding (SMAW): Also known as "stick welding," this process uses an electrode covered in flux to create an arc and fill the joint. It is common for its simplicity and versatility.

  • Gas Tungsten Arc Welding (GTAW): Also known as "TIG welding," this process uses a non-consumable tungsten electrode and an inert shielding gas to produce high-quality, precise welds. It is often used for critical casting repairs.

  • Gas Metal Arc Welding (GMAW): Known as "MIG welding," this semi-automatic process uses a continuous wire electrode and a shielding gas. It is a faster process, suitable for a range of materials.