Principles of

Major

Manufacturing

Processes

Prepared by:

Behzad Heidarshenas

Ph.D in Manufacturing

Processes

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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

• cleaning the finished casting

Workers who perform casting are called

foundrymen

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The Mold in Casting

Mold is a container with cavity whose geometry

determines part shape

Actual size and shape of cavity must be

slightly oversized to allow for shrinkage of

metal during solidification and cooling

Molds are made of a variety of materials,

including sand, plaster, ceramic, and metal

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Open Molds and Closed Molds

Two forms of mold: (a) open mold, simply a container in the

shape of the desired part; and (b) closed mold, in which the

mold geometry is more complex and requires a gating system

(passageway) leading into the cavity.

Cavity is open to atmosphere

Cavity is closed

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Two Categories of Casting Processes

1. Expendable mold processes – uses an

expendable mold which must be destroyed to

remove casting

Mold materials: sand, plaster, and similar

materials, plus binders

2. Permanent mold processes – uses a

permanent mold which can be used over and

over to produce many castings

Made of metal (or, less commonly, a

ceramic refractory material)

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Sand Casting Mold

Sand casting mold.

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Overview of Sand Casting

Sand casting is a cast part produced by

forming a mold from a sand mixture and then

pouring molten liquid metal into the cavity in

the mold. The mold is then cooled until the

metal has solidified

Most widely used casting process, accounting

for a significant majority of total tonnage cast

Nearly all alloys can be sand casted, including

metals with high melting temperatures, such as

steel, nickel, and titanium

Castings range in size from small to very large

Production quantities from one to millions

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A large sand casting weighing over 680 kg (1500 lb) for an air

compressor frame

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Steps in Sand Casting

1. Pour the molten metal into sand mold CAVITY

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

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Sand Casting Production Sequence

Figure: Steps in the production sequence in sand casting.

The steps include not only the casting operation but also

pattern-making and mold-making.

METAL FORMING

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Material Properties in Metal Forming

Desirable material properties:

Low yield strength

High ductility

These properties are affected by temperature:

Ductility increases and yield strength decreases

when work temperature is raised

Other factors:

Strain rate and friction

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Basic Types of Deformation Processes

1. Bulk deformation

Rolling

Forging

Extrusion

Wire and bar drawing

2. Sheet metalworking

Bending

Deep drawing

Cutting

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(stock has high V/A)

(stock has low V/A)

Bulk Deformation Processes

Characterized by significant deformations and

massive shape changes

"Bulk" refers to workparts with relatively low

surface area-to-volume ratios

Starting work shapes include cylindrical billets and

rectangular bars

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Basic bulk deformation processes: rolling

Rolling 15

Basic bulk deformation processes: forging

Forging

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Basic bulk deformation processes: (c) extrusion

Extrusion

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Basic bulk deformation processes: (d) drawing

Wire and Bar Drawing

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Sheet Metalworking

Forming and related operations performed on metal

sheets, strips, and coils

High surface area-to-volume ratio of starting metal,

which distinguishes these from bulk deformation

Often called pressworking because presses perform

these operations

Parts are called stampings

Usual tooling: punch and die

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Basic sheet metalworking operations: bending

Sheet Metal Bending

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Basic sheet metalworking operations: drawing

Deep Drawing

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Basic sheet metalworking operations: shearing

Shearing of Sheet Metal

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