metal forming.ppt
Post on 04-Jun-2018
230 Views
Preview:
TRANSCRIPT
-
8/14/2019 Metal Forming.ppt
1/80
Metal FormingInstructor: Dr. Syed Amir Iqbal
-
8/14/2019 Metal Forming.ppt
2/80
Metal Forming
Plastic deformation to change the shape of a metal workpiece
using a tool, called a die, by applying a stress that exceeds the
Yield Strength of the metal
Stresses are typically compressive:
Examples: rolling, forging, extrusion
However, some forming processes
Stretch the metal (tensile stresses)
Others bend the metal (tensile and compressive)
Still others apply shear
-
8/14/2019 Metal Forming.ppt
3/80
Importance of Bulk Deformation
In hot working, significant shape change can
be accomplished
In cold working, strength can be increased
during shape change
Little or no waste - some operations are near
net shape or net shape processes
The parts require little or no subsequent
machining
-
8/14/2019 Metal Forming.ppt
4/80
Material Behavior in Metal Forming
Plastic region of stress-strain curve is of primary
interest because material is plastically deformed
In plastic region, metal's behavior is expressed bythe flow curve:
where K= strength coefficient; and n= strain hardening
exponent.
Flow curve based on true stress and true strain
nK
-
8/14/2019 Metal Forming.ppt
5/80
Flow Stress
For metals at room temperature, strength
increases when deformed due to strain hardening
Flow stress= instantaneous value of stress
required to continuedeforming the material
where Yf = flow stress, that is, the yield strength as a
function of strain
n
f KY
-
8/14/2019 Metal Forming.ppt
6/80
Temperature in Metal Forming
Kand nin the flow curve depend on temperature
At higher temperatures both K and n are:
At higher temperatures ductility is:
Thus, the force and power required to performdeformation operations at elevated temperatures are:
Three temperature ranges in metal forming:
Cold working
Warm working
Hot working
-
8/14/2019 Metal Forming.ppt
7/80
-
8/14/2019 Metal Forming.ppt
8/80
Cold Working
Performed at roomtemperature
Many cold forming processes are important
mass production operations
Minimum or no machining usually required
These operations are near net shapeor net
shapeprocesses
-
8/14/2019 Metal Forming.ppt
9/80
Advantages of Cold Forming
Better accuracy, closer tolerances
Better surface finish
Strain hardening = strength and hardness
Grain flow during deformation can cause
desirable directional properties in product
No heating of work required
-
8/14/2019 Metal Forming.ppt
10/80
Disadvantages of Cold Forming
Forces and power required in the deformation
operation are:
Surfaces of starting workpiece must be free of
scale and dirt
Ductility and strain hardening limit the amount of
forming that can be done, metal may not be
ductile enough to be cold worked
-
8/14/2019 Metal Forming.ppt
11/80
Warm Working
Performed at temperatures above room
temperature i.e. 0.3 Tm- 0.5 Tm
Dividing line between cold working and warm
working often expressed in terms of melting
point:
0.3Tm, where Tm= melting point (absolute
temperature) for metal
-
8/14/2019 Metal Forming.ppt
12/80
Advantages of Warm Working
Lower forces and power than in cold working
More intricate work geometries possible
Need for annealing may be reduced or
eliminated
-
8/14/2019 Metal Forming.ppt
13/80
Hot Working
Deformation at temperatures in the range of
0.5Tm0.75 Tm
In practice, hot working usually performedsomewhat above 0.75Tm
Metal continues to soften as temperature increases
above 0.75Tm, enhancing advantage of hot working
above this level
-
8/14/2019 Metal Forming.ppt
14/80
Advantages of Hot Working
Workpart shape can be significantly altered
Lower forces and power required
Metals that usually fracture in cold working can
be hot formed Strength properties of product are generally
No strengthening of part occurs from work
hardening Advantageous in cases when part is to besubsequently processed by cold forming
-
8/14/2019 Metal Forming.ppt
15/80
Disadvantages of Hot Working
Lower dimensional accuracy
Higher total energy required (due to the
thermal energy to heat the workpiece)
Work surface oxidation (scale), poorer surface
finish
Shorter tool life
-
8/14/2019 Metal Forming.ppt
16/80
What is Strain Rate?
Strain rate in forming is directly related to speedof deformation v
Deformation speed v= velocity of the ram or
other movement of the equipment Strainrateis defined:
where = true strain rate; and h= instantaneousheight of workpiece being deformed
.
h
v
.
-
8/14/2019 Metal Forming.ppt
17/80
Strain Rate Sensitivity
Theoretically, a metal in hot working behaves like
a perfectly plastic material, with strain hardening
exponent n= 0
The metal should continue to flow at the same flow
stress, once that stress is reached
However, an additional phenomenon occurs duringdeformation, especially at elevated temperatures:
Strain rate sensitivity
-
8/14/2019 Metal Forming.ppt
18/80
Effect of Strain Rate on Flow Stress
Flow stress is a function of temperature
At hot working temperatures, flow stress also
depends on strain rate
As strain rate increases, resistance to
deformation
This effect is known as strain-rate sensitivity
-
8/14/2019 Metal Forming.ppt
19/80
Effect of Temperature on Flow Stress
Effect of temperature on flow
stress for a typical metal. The
flow stress decreases with
increase in temperature and
tends to increase with increase
in strain rate.
-
8/14/2019 Metal Forming.ppt
20/80
Basic Types of Deformation Processes
-
8/14/2019 Metal Forming.ppt
21/80
Basic Types of Deformation Processes
1. Bulk deformationstarting material has low surface areato volume (e.g. billets & bars)
Rolling
Forging
Extrusion Wire and bar drawing
2. Sheet metalworkingstarting material has high surfacearea to volume (e.g. sheet & coils)
Bending Deep drawing
Cutting
-
8/14/2019 Metal Forming.ppt
22/80
-
8/14/2019 Metal Forming.ppt
23/80
Sheet Metalworking
Often calledpress working Parts are often called stampings
Usual tooling:punchand die
Bending Cutting
-
8/14/2019 Metal Forming.ppt
24/80
Forging
Deformation process in which work is compressedbetween two dies
Oldest of the metal forming operations, dating from
about 5000 B.C. Components: engine crankshafts, connecting rods,
gears, aircraft structural components, jet engineturbine parts
Also, basic metals industries use forging to establishcomponents and parts that are subsequentlymachined to final shape and size
-
8/14/2019 Metal Forming.ppt
25/80
Types of Forging Dies
Open-die forging - work is compressedbetween two flat dies, allowing metal to flowlaterally with minimum constraint
Impression-die forging - die contains cavity orimpression that is imparted to workpart
Metal flow is constrained so that flash is created
Flashless forging - workpart is completelyconstrained in die
No excess flash is created
-
8/14/2019 Metal Forming.ppt
26/80
Open-Die Forging
Compression of work-part between two flat dies
Deformation operation reduces height and increases
diameter of work
Common names include Upsetting or Flat die forging.
-
8/14/2019 Metal Forming.ppt
27/80
Open-Die Forging with No Friction
If no friction occurs between work and die surfaces, then
homogeneous deformation occurs, so that radial flow is uniform
throughout workpart height and true strain is given by:
h
holn
-
8/14/2019 Metal Forming.ppt
28/80
Open-Die Forging with Friction
Friction between work and die surfaces constrains lateral flow of work,
resulting in barreling effect
In hot open-die forging, effect is even more pronounced due to heat
transfer at and near die surfaces, which cools the metal and increases its
resistance to deformation
-
8/14/2019 Metal Forming.ppt
29/80
Impression-Die Forging Flash is formed by metal that flows beyond die cavity into small gap
between die plates
Flash serves an important function:
As flash forms, friction resists continued metal flow into gap,
constraining material to fill die cavity
In hot forging, metal flow is further restricted by cooling against dieplates
-
8/14/2019 Metal Forming.ppt
30/80
-
8/14/2019 Metal Forming.ppt
31/80
Advantages and Limitations
Advantages of impression-die forging comparedto machining from solid stock:
Higher production rates
Savingof metal Finished part strength
Favorable grain orientation in the metal
Limitations:
Not capable of close tolerances
Machining often required to achieve accuracies andfeatures needed
-
8/14/2019 Metal Forming.ppt
32/80
Flashless Forging
Starting workpart volumemust equal die cavityvolume within very closetolerance
Process control moredemanding thanimpression-die forging
Accurate control of volumeof material.
Close tolerances can beachieved by proper diedesign.
Good die life.
-
8/14/2019 Metal Forming.ppt
33/80
-
8/14/2019 Metal Forming.ppt
34/80
Rolled Products Made of Steel
-
8/14/2019 Metal Forming.ppt
35/80
Diagram of Flat Rolling
There is a point on the roll where thework velocityequals the roll velocity,
this is the Neutral or no slip point.
Friction is zero on either side of this
point.
The friction is expressed in terms ofcoefficient of friction .
The reduction in thickness of the plate
is called DRAFT, expressed as (totf).
Draft is the function of coefficient of
friction and roll radius R. i.e. thelarger the coefficient of friction and
roll radius, the draft becomes the
maximum and hence the maximum
reduction in thickness is possible.
-
8/14/2019 Metal Forming.ppt
36/80
Rolling Issues
With Hot rolling, material properties are
improved, but dimensional tolerances are not
as tight, and surface oxidation occurs.
Wavy Edges
Zipper
Edge cracks
-
8/14/2019 Metal Forming.ppt
37/80
Shape Rolling
Work is deformed into a contoured cross section
rather than flat (rectangular)
Accomplished by passing work through rolls that
have the reverse of desired shape
Products include:
Construction shapes such as I-beams, L-beams, and
U-channels Rails for railroad tracks
Round and square bars and rods
-
8/14/2019 Metal Forming.ppt
38/80
Thread Rolling
Bulk deformation process used to form threads on cylindrical
parts by rolling them between two dies
Performed by cold working in thread rolling machines
The grain distribution in thread rolling are more improved and
beneficial as compared to thread machining.
-
8/14/2019 Metal Forming.ppt
39/80
Upsetting and Heading
Forging process used to form heads on nails, bolts,and similar hardware products
More parts produced by upsetting than any otherforging operation
Performed cold, warm, or hot on machines calledheadersorformers
Wire or bar stock is fed into machine, end isheaded, then piece is cut to length
For bolts and screws, thread rolling is then usedto form threads
-
8/14/2019 Metal Forming.ppt
40/80
Upsetting
An upset forging operation to form a head on a bolt orsimilar hardware item The cycle consists of: (1) wire stockis fed to the stop, (2) gripping dies close on the stock andthe stop is retracted, (3) punch moves forward, (4)bottoms to form the head.
-
8/14/2019 Metal Forming.ppt
41/80
Heading (Upset Forging)
Examples of heading (upset forging) operations: (a) heading a
nail using open dies, (b) round head formed by punch, (c) and(d) two common head styles for screws formed by die, (e)
carriage bolt head formed by punch and die.
-
8/14/2019 Metal Forming.ppt
42/80
Swaging
Accomplished by rotating dies that hammer a
workpiece radially inward to taper it as the
piece is fed into the dies Used to reduce diameter of tube or solid rod
stock
Mandrel sometimes required to control shape
and size of internal diameter of tubular parts
-
8/14/2019 Metal Forming.ppt
43/80
Swaging
Swaging process to reduce solid rod stock; the dies rotate asthey hammer the work In radial forging, the workpiece rotateswhile the dies remain in a fixed orientation as they hammer thework.
-
8/14/2019 Metal Forming.ppt
44/80
Extrusion
Compression forming process in which work metalis forced to flow through a die opening toproduce a desired cross-sectional shape
Process is similar to squeezing toothpaste out of
a toothpaste tube In general, extrusion is used to produce long
parts of uniform cross sections
Two basic types: Direct extrusion
Indirect extrusion
-
8/14/2019 Metal Forming.ppt
45/80
Direct Extrusion
Also calledforward extrusion As ram approaches die opening, a small portion
of billet remains that cannot be forced throughdie opening
This extra portion, called the butt, must beseparated from extrudateby cutting it justbeyond the die exit
Starting billet cross section usually round
Final shape of extrudate is determined by dieopening
-
8/14/2019 Metal Forming.ppt
46/80
Direct Extrusion
-
8/14/2019 Metal Forming.ppt
47/80
Indirect extrusion
Indirect extrusion to produce (a) a solid cross section and (b) a
hollow cross section.
Limitations of indirect extrusion are imposed by
Lower rigidity of hollow ram Difficulty in supporting extruded product as it exits die
-
8/14/2019 Metal Forming.ppt
48/80
Hot vs. Cold Extrusion
Hot extrusion - prior heating of billet to above itsrecrystallization temperature
Reduces strength and increases ductility of themetal, permitting more size reductions and morecomplex shapes
Cold extrusion - generally used to producediscrete parts
The term impact extrusion is used to indicate highspeed cold extrusion
Material possess some degree of strain-hardening
-
8/14/2019 Metal Forming.ppt
49/80
Complex Cross Section
A complex extruded cross section for a heat sink (photo courtesy of
Aluminum Company of America)
-
8/14/2019 Metal Forming.ppt
50/80
Wire and Bar Drawing
Cross-section of a bar, rod, or wire is reduced by
pulling it through a die opening
Similar to extrusion except work ispulledthrough
die in drawing (it ispushedthrough in extrusion)
Although drawing applies tensile stress,
compression also plays a significant role since
metal is squeezed as it passes through die
opening
-
8/14/2019 Metal Forming.ppt
51/80
Wire and Bar Drawing
Drawing of bar, rod, or wire
-
8/14/2019 Metal Forming.ppt
52/80
Area Reduction in Drawing
Change in size of work is usually given by area
reduction:
where r= area reduction in drawing;Ao=
original area of work; andAr= final work
o
fo
A
AA
r
-
8/14/2019 Metal Forming.ppt
53/80
Wire Drawing
Continuous drawing machines consisting of
multiple draw dies (typically 4 to 12) separated by
accumulating drums
Each drum (capstan) provides proper force to drawwire stock through upstream die
Each die provides a small reduction, so desired total
reduction is achieved by the series
Annealing sometimes required between dies to
relieve work hardening
-
8/14/2019 Metal Forming.ppt
54/80
Continuous drawing of wire
-
8/14/2019 Metal Forming.ppt
55/80
Features of a Draw Die
Entry region - funnels lubricant into the die to prevent scoring
of work and die
Approach - cone-shaped region where drawing occurs
Bearing surface - determines final stock size
Back relief - exit zone - provided with a back relief angle
(half-angle) of about 30
-
8/14/2019 Metal Forming.ppt
56/80
Sheet metal forming
Sheet metal forming is a grouping of many complementary processes that are
used to form sheet metal parts. One or more of these processes is used to take a
flat sheet of ductile metal, and mechanically apply deformation forces that alter
the shape of the material.
Before deciding on the
processes), one should
determine whether a particular
sheet metal can be formed into
the desired shape without
failure. The sheet metal
operations done on a press maybe grouped into two categories,
cutting (shearing) operations
and forming operations.
-
8/14/2019 Metal Forming.ppt
57/80
Cutting (Shearing) Operations
In this operation, the workpiece is stressed beyond its ultimatestrength. The stresses caused in the metal by the applied forces willbe shearing stresses. The cutting operations include:
Punching (Piercing)
Blanking
Notching
Perforating
Slitting
Lancing
Parting Shaving
Trimming
Fine blanking
-
8/14/2019 Metal Forming.ppt
58/80
Shearing Operations
Punching (Piercing):It is a cutting operation by which various shapedholes are made in sheet metal. Punching is similar to blanking except thatin punching, the hole is the desired product, the material punched out toform the hole being waste.
Blanking: Blanking is the operation of cutting a flat shape sheet metal. Thearticle punched out is called the blank and is the required product of the
operation. The hole and metal left behind is discarded as waste.
-
8/14/2019 Metal Forming.ppt
59/80
Notching: This is cutting operation by which metal pieces are cut from the edge of a sheet, strip orblank.
Perforating: This is a process by which multiple holes which are very small and close together are cutin flat work material.
Slitting: It refers to the operation of making incomplete holes in a workpiece.
Lancing: This is a cutting operation in which a hole is partially cut and then one side is bent down toform a sort of tab. Since no metal is actually removed, there will be no scrap.
Parting: Parting involves cutting a sheet metal strip by a punch with two cutting edges that matchthe opposite sides of the blank.
Shearing Operations
-
8/14/2019 Metal Forming.ppt
60/80
Shaving: The edge of blanked parts is generally rough, uneven andunsquare. Accurate dimensions of the part are obtained byremoving a thin strip of metal along the edges.
Trimming: This operation consists of cutting unwanted excessmaterial from the periphery of previously formed components.
Fine blanking: Fine blanking is a operation used to blank sheetmetal parts with close tolerances and smooth, straight edges in onestep.
Shearing Operations
-
8/14/2019 Metal Forming.ppt
61/80
Shearing Dies Because the formability of a sheared part can be influenced by the quality of its sheared edges,
clearance control is important. In practice, clearances usually range between 2% and 8% of thesheets thickness; generally, the thicker the sheet, the larger is the clearance (as much as 10%).
However, the smaller the clearance, the better is the quality of the edge. Some common
shearing dies are describe below:
Punch and Die Shapes: As the surfaces of the punch and die are flat; thus, the punch force
builds up rapidly during shearing, because the entire thickness of the sheet is sheared at the
same time. However, the area being sheared at any moment can be controlled be bevelingthe punch and die surfaces, as shown in the following Figure. This geometry is particularly
suitable for shearing thick blanks, because it reduces the total shearing force.
-
8/14/2019 Metal Forming.ppt
62/80
Compound Dies
Several operations on the same strip may be performed in onestroke with a compound die in one station. These operations are
usually limited to relatively simple shearing because they are
somewhat slow and the dies are more expensive than those for
individual shearing operations.
(a) (b) Schematicillustrations: (a)before and (b) afterblanking a commonwasher in acompound die.
Note the separatemovements of thedie (for blanking)and the punch (forpunching the holein the washer).
-
8/14/2019 Metal Forming.ppt
63/80
Progressive DiesParts requiring multiple operations, such as punching, blanking and notching are made
at high production rates in progressive dies. The sheet metal is fed through a coil strip
and a different operation is performed at the same station with each stroke of a series
of punches.
(a) Schematic illustration of making a washer in a progressive die. (b) Forming of the toppiece of an aerosol spray can in a progressive die.
-
8/14/2019 Metal Forming.ppt
64/80
Forming Operations
In this operation, the stresses are below the ultimate strength of the metal. In thisoperation, there is no cutting of the metal but only the contour of the workpiece ischanged to get the desired product. The forming operations include:
Bending: In this operation, the material in the form of flat sheet or strip, isuniformly strained around a linear axis which lies in the neutral plane andperpendicular to the lengthwise direction of the sheet or metal. The bendingoperations include:
Drawing: This is a process of a forming a flat workpiece into a hollow shape bymeans of a punch, which causes the blank to flow into die cavity.
Squeezing: Under this operation, the metal is caused to flow to all portions ofa die cavity under the action of compressive forces.
V-bending
Edge bending
Roll bending
Air bending
Flanging
Dimpling
Press break forming
Beading
Roll forming
Tube forming
Bulging
Stretch forming
-
8/14/2019 Metal Forming.ppt
65/80
Bending of Flat Sheet and Plate
V-bending Edge bending Roll bending
Bending in 4-slide machine Air bending
-
8/14/2019 Metal Forming.ppt
66/80
Flanging Flanging is a process of bending the edges of sheet metals to 90o
Shrink flangingsubjected to compressive hoop stress.
Stretch flangingsubjected to tensile stresses
-
8/14/2019 Metal Forming.ppt
67/80
Dimpling
First hole is punched and expanded into a flange
Flanges can be produced by piercing with shaped punch
When bend angle < 90 degrees as in fitting conical ends its
called flanging
-
8/14/2019 Metal Forming.ppt
68/80
Press break forming
Sheet metal or plate can be bent easily with simple fixtures using apress. Long and relatively narrow pieces are usually bent in a press
break. This machine utilizes long dies in a mechanical or hydraulic
press and is suitable for small production runs. The tooling is simple
and adaptable to a wide variety of shapes.
-
8/14/2019 Metal Forming.ppt
69/80
Beading
In beading the edge of the sheet metal is bent into the cavity of adie. The bead gives stiffness to the part by increasing the
moment on inertia of the edges. Also, it improves the
appearance of the part and eliminates exposed sharp edges
(a) Bead forming with a single die. (b) Bead forming with two dies, in a
press brake.
-
8/14/2019 Metal Forming.ppt
70/80
Roll formingFor bending continuous lengths of sheet metal and for large
production runs, roll forming is used. The metal strip is bent in stages
by passing it through a series of rolls.
Stages in roll forming of a sheet-metal door frame. In Stage 6, the rolls may be
shaped as inAor B.
-
8/14/2019 Metal Forming.ppt
71/80
Tube BendingBending and forming tubes and other hollow sections require special tooling to avoid
buckling and folding. The oldest method of bending a tube or pipe is to pack the insidewith loose particles, commonly used sand and bend the part in a suitable fixture. This
techniques prevents the tube from buckling. After the tube has been bent, the sand is
shaken out. Tubes can also be plugged with various flexible internal mandrels.
Methods of bending tubes. Internal mandrels,or the filling of tubes with particulate materials such assand,are often necessary to prevent collapse of the tubes during bending .Solid rods and structural shapes
can also be bent by these techniques
-
8/14/2019 Metal Forming.ppt
72/80
BulgingThe basic forming process of bulging involves placing tabular, conical or curvilinear
part into a split-female die and expanding it with, say, a polyurethane plug. The punch
is then retracted, the plug returns to its original shape and the part is removed by
opening the dies.
(a) Bulging of a tubular part with a flexible plug. Water pitchers can be made by this method. (b) Production
of fittings for plumbing by expanding tubular blanks with internal pressure. The bottom of the piece is thenpunched out to produce a T. (c) Manufacturing of Bellows.
-
8/14/2019 Metal Forming.ppt
73/80
Stretch FormingIn stretch forming, the sheet metal is clamped around its edges and stretched over a die or
form block, which moves upward, downward or sideways, depending on the particularmachine. Stretch forming is used primarily to make aircraft-wing skin panel, automobile door
panels and window frames.
Schematic illustration of a stretch-forming process. Aluminum skins
for aircraft can be made by this process.
Hydroform (or) Fluid Forming Process
-
8/14/2019 Metal Forming.ppt
74/80
Hydroform (or) Fluid Forming Process
In hydroforming or fluid forming process, the pressure over the rubber membrane is
controlled throughout the forming cycle, with maximum pressure reaching 100 MPa (15000
psi). This procedure allows close control of the part during forming to prevent wrinkling ortearing. When selected properly, rubber forming and hydroforming processes have the
following advantages:
Low tooling cost
Flexibility and ease of operation
Low die wear No damage to the surface of the sheet and
Capability to form complex shapes.
The hydroform (or fluid forming) process. Note that, in contrast to the ordinary deep-drawing process, the
pressure in the dome forces the cup walls against the punch. The cup travels with the punch; in this way,deep drawability is improved.
Deep Drawing Processes
-
8/14/2019 Metal Forming.ppt
75/80
Deep Drawing Processes
Drawing operation is the process of forming a flat piece of material (blank) into a hollow
shape by means of a punch, which causes the blank to flow into the die-cavity. Round sheetmetal block is placed over a circular die opening and held in a place with blank holder &
punch forces down into the die cavity. Wrinkling occurs at the edges.
Shallow drawing: depth of formed cup D/2 Deep or moderate drawing: depth of formed cup > D/2
(a) deep-drawing process on a circular sheet-metal blank. The stripper ring facilitates the removal of the formed cup
from the punch. (b) Process variables in deep drawing. Except for the punch force, F, all the parameters indicated inthe figure are independent variables.
-
8/14/2019 Metal Forming.ppt
76/80
Drawing Operations
Examples of drawing operations: (a) pure drawing and (b) pure stretching. The bead prevents the sheet metalfrom flowing freely into the die cavity. (c) Possibility of wrinkling in the unsupported region of a sheet in drawing.
-
8/14/2019 Metal Forming.ppt
77/80
Redrawing OperationsContainers or shells that are too difficult to draw in one operation are generally redrawn. In
reverse redrawing, shown in following Figure, the metal is subjected to bending in thedirection opposite to its original bending configuration. This reversal in bending results in
strain softening. This operation requires lower forces than direct redrawing and the material
behaves in a more ductile manner.
Reducing the diameter of drawn cups
by redrawing operations: (a)
conventional redrawing and (b) reverse
redrawing. Small-diameter deep
containers undergo many drawing andredrawing operations.
f
-
8/14/2019 Metal Forming.ppt
78/80
Top of Aluminum Can
Metal-Forming Process for Beverage Can
-
8/14/2019 Metal Forming.ppt
79/80
Metal Forming Process for Beverage Can
Steps in Manufacturing an
Aluminum Can
The metal-forming processes involved inmanufacturing a two-piece aluminumbeverage can
-
8/14/2019 Metal Forming.ppt
80/80
top related