Department of Applied Sciences, BVCOE New Delhi
ES-119 UNIT -3
MANUFACTURING PROCESS
HOT WORKING �& �COLD WORKING PROCESS
METAL TEMP. (degree Cel.)
ALUMINIUM 150
COPPER 200
IRON 450
NICKEL 590
ZINC At room temp
LEAD Below room temp
TIN Below room temp
RE- CRYSTALLISATION TEMPERATURE
HOT AND COLD WORKING
Advantages of HOT WORKING
Large deformation can be obtained
In hot working process, the grain structure of the metal is refined and thus mechanical properties improved
Porosity of the metal is considerably minimized
If process is properly carried out, hot work does not affect tensile strength, hardness, corrosion resistance, etc
Concentrated impurities, if any in the metal are disintegrated and distributed throughout the metal
Disadvantages of HOT WORKING
Some metals cannot be hot worked because of their brittleness at high temperatures.
Handling and maintaining of hot working setups is difficult and troublesome.
Because of the thermal expansion of metals, the dimensional accuracy in hot working is difficult to achieve.
Rapid oxidation of metals occurs
PRINCIPAL OF HOT WORKING
HOT WORKING
GRAIN FLOW
GRAIN FLOW
FORGING METHODS
SMITH OR HAND FORGING
SMITH OR HAND FORGING
TYPES OF SMITH FORGING
FULLERING
FULLERING
FLATTENING
SWAGING
PUNCHING
BENDING
DRIFTING
DROP FORGING
PRESS FORGING
UPSET OR MACHINE FORGING
UPSET OR MACHINE FORGING (CLOSE)
UPSET OR MACHINE FORGING (OPEN)
FORGING TOOLS
FORGING TOOLS
FORGING TOOLS
FORGING TOOLS
FORGING TOOLS
COLD & HOT CHISEL
FORGING TOOLS
FORGING TOOLS
FORGING TOOLS
FORGING TOOLS
WHAT IS EXTRUSION
A material is pushed or drawn through a die of the desired cross-section .Any solid or hollow cross-section may be produced by extrusion, which can create essentially semi-finished parts. The metal can forcing through a die in the same direction or opposite direction.
Extrusion
Typical use: ductile metals (Cu, Steel, Al, Mg), Plastics, Rubbers
Common products:
Al frames of white-boards, doors, windows, …
The cross-sections that can be produced vary from solid round, rectangular, to L shapes, T shapes.
Extrusion may be continuous (theoretically producing indefinitely long material) or semi-continuous (producing many pieces). Extrusions can be done with the material hot or cold.
Commonly extruded materials include metals, polymers, ceramics, and foodstuffs.
Direct extrusion: A metal billet is located into a container, and a ram compresses the material, forcing it to flow through one or more openings in a die at the opposite end of the container.
Indirect extrusion: The die is mounted to the ram rather than at the opposite end of the container. One advantage of the indirect extrusion process is that there is no friction, during the process, between the billet and the container liner.
Extrusion: Schematic, Dies
Exercise: how can we get hollow parts?
Drawing
Commonly used to make wires from round bars
Similar to extrusion, except: pulling force is applied
WHAT is DRAWING?
Drawing is an operation in which the cross-section of solid rod, wire or tubing is reduced or changed in shape by pulling it through a die.
The principle of this procedure consist of reducing the thickness of a pointed ,tapered wire by drawing it through a conical opening in a tool made of a hard material.The wire will take shape of the hole.
Drawing improves strength and hardness when these properties are to be developed by cold work and not by subsequent heat treatment.
This process is widely used for the production of thicker walled seamless tubes and cylinders therefore; shafts, spindles, and small pistons and as the raw material for fasteners such as rivets, bolts, screws.
SHEET METAL WORKING
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SHEET METALWORKING
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Sheet Metalworking Defined
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Metals used for sheets
There are many different metals that can be made into sheet metal, such as aluminum, brass, copper, steel, tin, nickel and titanium. For decorative uses, important sheet metals include silver, gold, and platinum (platinum sheet metal is also utilized as a catalyst.)
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Steel (American Wire Gauge in inch)
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Gauge | Thickness |
28�26�24�22�20�18�16�14�12�11�10�8�7 | 0.015”�0.018”�0.024”�0.030”�0.036”�0.048”�0.060”�0.075”�0.105�0.120”�0.134”�0.160”�0.1874” |
Aluminium (AWG in inch)
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Gauge | Thickness |
22�20�18�16�14�12�11�10 | 025”�0.032”�0.040”�0.050”�0.063”�0.080”�0.090”�0.100”�0.125”�0.160”�0.190” |
Sheet and Plate Metal Products
Sheet and plate metal parts for consumer and industrial products such as
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Advantages of Sheet Metal Parts
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Sheet Metalworking Terminology
Tooling to perform cutting, bending, and drawing
Machine tool that performs most sheet metal operations
Sheet metal products
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Three Major Categories of �Sheet Metal Processes
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Cutting
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Shearing between two sharp cutting edges
Shearing, Blanking, and Punching
Three principal operations in press working that cut sheet metal:
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Shearing
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Blanking and Punching
Blanking - sheet metal cutting to separate piece from surrounding stock
Cut piece is the desired part, called a blank
Punching - sheet metal cutting similar to blanking except cut piece is scrap, called a slug
Remaining stock is the desired part
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(a) Blanking and (b) punching
Bending
Straining sheetmetal around a straight axis to take a permanent bend
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(a) Bending of sheet metal
(b) both compression and tensile elongation of the metal occur in bending
Types of Sheetmetal Bending
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V-Bending
For low production
Performed on a press brake
V-dies are simple and inexpensive
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Edge Bending
For high production
Pressure pad required
Dies are more complicated and costly
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Springback in Bending
Springback = increase in included angle of bent part relative to included angle of forming tool after tool is removed
Reason for springback:
When bending pressure is removed, elastic energy remains in bent part, causing it to recover partially toward its original shape
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Drawing
Sheet metal forming to make cup‑shaped, box‑shaped, or other complex‑curved, hollow‑shaped parts
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Products: beverage cans, ammunition shells, automobile body panels
Shapes other than Cylindrical Cups
Square or rectangular boxes (as in sinks),
Stepped cups,
Cones,
Cups with spherical rather than flat bases,
Irregular curved forms (as in automobile body panels)
Each of these shapes presents its own unique technical problems in drawing
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Embossing
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Embossing: (a) cross‑section of punch and die configuration during pressing; (b) finished part with embossed ribs
Power and Drive Systems
Hydraulic presses - use a large piston and cylinder to drive the ram
Longer ram stroke than mechanical types
Suited to deep drawing
Slower than mechanical drives
Mechanical presses – convert rotation of motor to linear motion of ram
High forces at bottom of stroke
Suited to blanking and punching
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Sheet Metal Operations �Not Performed on Presses
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Stretch Forming
Sheet metal is stretched and simultaneously bent to achieve shape change
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Stretch forming: (1) start of process; (2) form die is pressed into the work with force Fdie, causing it to be stretched and bent over the form. F = stretching force
Spinning
Metal forming process in which an axially symmetric part is gradually shaped over a rotating mandrel using a rounded tool or roller
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Conventional spinning: (1) setup at start of process; (2) during spinning; and (3) completion of process