Sheet metal processes involve cutting, bending, and forming thin metal sheets. Common processes include shearing to cut sheets, bending using various dies, drawing to make hollow parts, and stamping using progressive dies. Other specialized processes such as roll forming, spinning, and superplastic forming provide unique shapes through techniques like continuous bending over rolls or stretching over mandrels at high temperatures. A variety of automotive, aircraft, and household goods are produced from sheet metal using these forming techniques.
2. Introduction
Sheet metal is simply metal formed into thin and flat
pieces. It is one of the fundamental forms used in
metalworking, and can be cut and bent into a variety of
different shapes. Countless everyday objects are
constructed of the material. Thicknesses can vary
significantly, although extremely thin thicknesses are
considered foil or leaf, and pieces thicker than 6 mm
(0.25 in) are considered plate.
3. Sheet metal processing
The raw material for sheet metal manufacturing
processes is the output of the rolling process.
Typically, sheets of metal are sold as flat, rectangular
sheets of standard size. If the sheets are thin and very
long, they may be in the form of rolls. Therefore the
first step in any sheet metal process is to cut the correct
shape and sized ‘blank’ from larger sheet.
5. Introduction
1. Sheet metal processes involve plane stress loadings
and lower forces than bulk forming
2. Almost all sheet metal forming is considered to be
secondary processing
3. The main categories of sheet metal forming are
• Shearing
• Bending
• Drawing
6. Shearing
Shearing is a sheet metal cutting operation along a
straight line between two cut-ting edges by means of a
power shear.
7. Blanking and punching
Blanking and punching are similar sheet metal cutting operations that
involve cutting the sheet metal along a closed outline. If the part that is cut out is
the desired product, the operation is called blanking and the product is called
blank. If the remaining stock is the desired part, the operation is called punching.
Both operations are illustrated on the example of producing a washer
10. Bending force :
Maximum bending force, P = KYLT2
W
K – constant ranges from 0.3(wiping die) – 0.7(u-die)-1.3(V-die)
Y – yield stress
L- length of the bend
T- thickness of sheet
For a V-die
Max bending force, P = (UTS)LT 2
W
UTS – Ultimate tensile strength
11. Drawing
Drawing is a sheet-metal operation to make hollow-shaped
parts from a sheet blank
12. Dies and Punches
Simple- single operation with a single stroke
Compound- two operations with a single stroke
Combination- two operations at two stations
Progressive- two or more operations at two or more
stations with each press stroke, creates what is called a
strip development
13. COMPOUND DIES
Several operations on the same strip performed in one
stroke at one station with a compound dies
Schematic illustrations: (a) before and (b) after blanking a common washer in a
compound die.note the separate movements of the die(or blanking) and the punch
15. Merits
•High strength
•Good dimensional accuracy and surface finish
•Relatively low cost
Demerits
•Wrinkling and tearing are typical limits to drawing operations
•Trimming may be used to reach final dimensions
17. ROLL FORMING
Process where sheet metal strips are passed through
consecutive set of rolls and bent in consecutive
stages and then sheared into specific lengths and
stacked continuously.
Forming speed: below 1.5 m/s (300 ft/min)
Examples: Door panels, picture frame, and gutters.
18. Stretch Forming
Process where a sheet metal is clamped along
it’s edges and stretched over a male die (form
die or form punch).
Examples: aircraft wing-skin panels, fuselages,
and boat hulls.
19. Rubber Forming
One of the dies in the set is made of polyurethane
membrane, which is a type of flexible material.
Polyurethane is resistant to abrasion, cutting or tearing
by the metal, and has a long fatigue life.
20. SPINNING
Process where a circular
piece of sheet metal is
placed and held against a
mandrel and rotated
while a rigid tool deforms
and shapes the material
over the mandrel.
May be performed at
room temperature or at
higher temperature for
thicker metal.
21. Shear spinning :
Known as power spinning, flow turning, hydro-spinning, and
spin forging
Produces axisymmetric conical or curvilinear shape
Single rollers and two rollers can be used
It has less wastage of material
Typical products are rocket-
motor casing and missile
nose cones.
22. Tube spinning
Thickness of cylindrical parts are reduced by spinning them on a
cylindrical mandrel rollers
Parts can be spun in either direction
Large tensile elongation up to 2000 % are obtained within certain
temperature ranges and at low strain rates.
23. Super Plastic Forming
Types of
structures made
by diffusion
bonding and
superplastic
forming of sheet
metal. Such
structures have a
high stiffness-to-
weight ratio.
24. EXPLOSIVE FORMING
First used to form metals in the 1900’s. A sheet metal blank is
clamped over a die, and the entire assembly is lowered into a
tank filled with water. The air in the cavity is evacuated, and an
explosive is detonated at a certain height above.
25. MAGNETIC-PULSE FORMING
Also called electromagnetic forming. Energy stored in a capacitor
bank is discharged rapidly through a magnetic coil. Magnetic field
crosses metal tube (conductor) creating eddy currents which have
an opposing magnetic field.
(a)
(b)
Figure 16.45 (a) Schematic illustration of the magnetic-pulse forming process used to form a
tube over a plug. (b) Aluminum tube collapsed over a hexagonal plug by the magnetic-pulse
forming process.
Hinweis der Redaktion
SHEET METAL PROCESSES
ntroduction Sheet metal is simply metal formed into thin and flat pieces. It is one of the fundamental forms used in metalworking, and can be cut and bent into a variety of different shapes. Countless everyday objects are constructed of the material. Thicknesses can vary significantly, although extremely thin thicknesses are considered foil or leaf, and pieces thicker than 6 mm (0. 25 in) are considered plate.
Sheet metal processing The raw material for sheet metal manufacturing processes is the output of the rolling process. Typically, sheets of metal are sold as flat, rectangular sheets of standard size. If the sheets are thin and very long, they may be in the form of rolls. Therefore the first step in any sheet metal process is to cut the correct shape and sized ‘blank’ from larger sheet.
Sheet Metal Forming processes
Introduction 1. Sheet metal processes involve plane stress loadings and lower forces than bulk forming 2. Almost all sheet metal forming is considered to be secondary processing 3. The main categories of sheet metal forming are • Shearing • Bending • Drawing
Shearing is a sheet metal cutting operation along a straight line between two cut-ting edges by means of a power shear.
Blanking and punching are similar sheet metal cutting operations that involve cutting the sheet metal along a closed outline. If the part that is cut out is the desired product, the operation is called blanking and the product is called blank. If the remaining stock is the desired part, the operation is called punching. Both operations are illustrated on the example of producing a washer
Bending is defined as the straining of the sheet metal around a straight edge
Bending force : Maximum bending force, P = KYLT 2 W K – constant ranges from 0. 3(wiping die) – 0. 7(u-die)-1. 3(V-die) Y – yield stress L- length of the bend T- thickness of sheet For a V-die Max bending force, P = (UTS)LT 2 W UTS – Ultimate tensile strength
Drawing is a sheet-metal operation to make hollow-shaped parts from a sheet blank
Dies and Punches Simple- single operation with a single stroke Compound- two operations with a single stroke Combination- two operations at two stations Progressive- two or more operations at two or more stations with each press stroke, creates what is called a strip development
COMPOUND DIES o Several operations on the same strip performed in one stroke at one station with a compound dies Schematic illustrations: (a) before and (b) after blanking a common washer in a compound die. note the separate movements of the die(or blanking) and the punch
Progressive dies
Merits • High strength • Good dimensional accuracy and surface finish • Relatively low cost Demerits • Wrinkling and tearing are typical limits to drawing operations • Trimming may be used to reach final dimensions
Applications • Roofing • Ducting • Vehicles body buildings like 3 wheelers, 4 wheelers, ships, aircrafts etc. • Furniture, House hold articles and Railway equipment
ROLL FORMING n n n Process where sheet metal strips are passed through consecutive set of rolls and bent in consecutive stages and then sheared into specific lengths and stacked continuously. Forming speed: below 1. 5 m/s (300 ft/min) Examples: Door panels, picture frame, and gutters.
Stretch Forming n n Process where a sheet metal is clamped along it’s edges and stretched over a male die (form die or form punch). Examples: aircraft wing-skin panels, fuselages, and boat hulls.
Rubber Forming n n One of the dies in the set is made of polyurethane membrane, which is a type of flexible material. Polyurethane is resistant to abrasion, cutting or tearing by the metal, and has a long fatigue life.
SPINNING n n Process where a circular piece of sheet metal is placed and held against a mandrel and rotated while a rigid tool deforms and shapes the material over the mandrel. May be performed at room temperature or at higher temperature for thicker metal.
Shear spinning : Known as power spinning, flow turning, hydro-spinning, and spin forging o Produces axisymmetric conical or curvilinear shape o Single rollers and two rollers can be used o It has less wastage of material o Typical products are rocketmotor casing and missile nose cones. o
Tube spinning o o o Thickness of cylindrical parts are reduced by spinning them on a cylindrical mandrel rollers Parts can be spun in either direction Large tensile elongation up to 2000 % are obtained within certain temperature ranges and at low strain rates.
Super Plastic Forming Types of structures made by diffusion bonding and superplastic forming of sheet metal. Such structures have a high stiffness-toweight ratio.
EXPLOSIVE FORMING o First used to form metals in the 1900’s. A sheet metal blank is clamped over a die, and the entire assembly is lowered into a tank filled with water. The air in the cavity is evacuated, and an explosive is detonated at a certain height above.
MAGNETIC-PULSE FORMING o Also called electromagnetic forming. Energy stored in a capacitor bank is discharged rapidly through a magnetic coil. Magnetic field crosses metal tube (conductor) creating eddy currents which have an opposing magnetic field. (a) (b) Figure 16. 45 (a) Schematic illustration of the magnetic-pulse forming process used to form a tube over a plug. (b) Aluminum tube collapsed over a hexagonal plug by the magnetic-pulse forming process.