The document discusses sheet metal working processes and cutting operations. It describes the three major categories of sheet metal processes as cutting, bending, and drawing. Cutting operations like shearing, blanking, and piercing are used to separate sheet metal into pieces or make holes. Proper die clearances and cutting forces must be considered for optimal cutting. Tools called punches and dies are used to perform these operations on stamping presses.
Classification of metal removal process and machines: Concept of generatrix and directrix Geometry of single point cutting tool and tool angles, tool nomenclature in ASA, ORS, NRS. Concept of orthogonal and oblique cutting, Mechanism of Chip Formation: Type of chips. Mechanics of metal cutting, interrelationships between cutting force, shear angle, strain and strain rate. Various theories of metal cutting, Thermal aspects of machining and measurement of chip tool interface temperature, Friction in metal cutting
Classification of metal removal process and machines: Concept of generatrix and directrix Geometry of single point cutting tool and tool angles, tool nomenclature in ASA, ORS, NRS. Concept of orthogonal and oblique cutting, Mechanism of Chip Formation: Type of chips. Mechanics of metal cutting, interrelationships between cutting force, shear angle, strain and strain rate. Various theories of metal cutting, Thermal aspects of machining and measurement of chip tool interface temperature, Friction in metal cutting
Forging is the operation where the metal is heated and then a force is applied to manipulates the metals in such a way that the required final shape is obtained.
Theory of metal cutting MG University(S8 Production Notes)Denny John
Theory of metal cutting MG University(S8 Production Notes)
Scenario of manufacturing process – Deformation of metals,
Schmid’s law (review only) – Performance and process parameters – single point cutting
tool nomenclature - attributes of each tool nomenclature - attributes of feed and tool
signature on surface roughness obtainable, role of surface roughness on crack initiation -
Oblique and orthogonal cutting – Mechanism of metal removal - Primary and secondary
deformation shear zones - Mechanism of chip formation, card model, types of chip,
curling of chips, flow lines in a chip, BUE, chip breakers, chip thickness ratio –
Mechanism of orthogonal cutting: Thin zone and thick zone, Merchant’s analysis – shear
angle relationship, Lee and Shaffer`s relationship, simple problems – Friction process in
metal cutting: nature of sliding friction, columb`s law, adhesion theory, ploughing, sublayer
flow – Empirical determination of force component.
This presentation contains various aspects of metal cutting like mechanics of chip formation, single point cutting tool, chip breakers, types of chips,etc
Sheet metal characteristics – shearing, bending and drawing operations – Stretch forming operations – Formability of sheet metal – Test methods –special forming processes-Working principle and applications – Hydro forming – Rubber pad forming – Metal spinning– Introduction of Explosive forming, magnetic pulse forming, peen forming, Super plastic forming – Micro forming.
Forging is the operation where the metal is heated and then a force is applied to manipulates the metals in such a way that the required final shape is obtained.
Theory of metal cutting MG University(S8 Production Notes)Denny John
Theory of metal cutting MG University(S8 Production Notes)
Scenario of manufacturing process – Deformation of metals,
Schmid’s law (review only) – Performance and process parameters – single point cutting
tool nomenclature - attributes of each tool nomenclature - attributes of feed and tool
signature on surface roughness obtainable, role of surface roughness on crack initiation -
Oblique and orthogonal cutting – Mechanism of metal removal - Primary and secondary
deformation shear zones - Mechanism of chip formation, card model, types of chip,
curling of chips, flow lines in a chip, BUE, chip breakers, chip thickness ratio –
Mechanism of orthogonal cutting: Thin zone and thick zone, Merchant’s analysis – shear
angle relationship, Lee and Shaffer`s relationship, simple problems – Friction process in
metal cutting: nature of sliding friction, columb`s law, adhesion theory, ploughing, sublayer
flow – Empirical determination of force component.
This presentation contains various aspects of metal cutting like mechanics of chip formation, single point cutting tool, chip breakers, types of chips,etc
Sheet metal characteristics – shearing, bending and drawing operations – Stretch forming operations – Formability of sheet metal – Test methods –special forming processes-Working principle and applications – Hydro forming – Rubber pad forming – Metal spinning– Introduction of Explosive forming, magnetic pulse forming, peen forming, Super plastic forming – Micro forming.
this file is about the types of dies and also its manufacturing procedure.this is important for the industry and for the industrial and manufacturing engineering..are of this field is manufacturing engineering and die designalso for the blanking dies and punches
Press working terminology is described in a simple way to understand.Classification and Types are also explained in a simple way to understand by everyone.
Prediction of Draw Ratio in Deep Drawing through Software Simulationsirjes
Deep drawing process is one of the most commonly used Metal Forming Process within the
industrial field. Different analytical, numerical, empirical and experimental methods have been developed in
order to analyze it. In this paper deep drawing process with varying punch and die geometries are analysed. This
work reports on the stages of finite element analysis (FEA) and simulations of a Deep drawing process. The
obtained result allows to find optimum draw ratios in deep drawing.
Roll forming Long parts with constant complex cross-sections; good surface finish; high
production rates; high tooling costs.
Stretch forming
Large parts with shallow contours; suitable for low-quantity production; high
labor costs; tooling and equipment costs depend on part size.
Drawing Shallow or deep parts with relatively simple shapes; high production rates;
high tooling and equipment costs.
Stamping Includes a variety of operations, such as punching, blanking, embossing,
bending, flanging, and coining; simple or complex shapes formed at high
production rates; tooling and equipment costs can be high, but labor costs
are low.
Rubber-pad
forming
Drawing and embossing of simple or complex shapes; sheet surface protected
by rubber membranes; flexibility of operation; low tooling costs.
Spinning Small or large axisymmetric parts; good surface finish; low tooling costs, but
labor costs can be high unless operations are automated.
Superplastic
forming
Complex shapes, fine detail, and close tolerances; forming times are long,
and hence production rates are low; parts not suitable for high-temperature
use.
Peen forming Shallow contours on large sheets; flexibility of operation; equipment costs
can be high; process is also used for straightening parts.
Explosive
forming
Very large sheets with relatively complex shapes, although usually axisymmetric;
low tooling costs, but high labor costs; suitable for low-quantity
production; long cycle times.
Magnetic-pulse
forming
Shallow forming, bulging, and embossing operations on relatively lowstrength
sheets; most suitable for tubular shapes; high production rates;
requires special tooling.
Formability of superplastic deep drawing process with moving blank holder for...eSAT Journals
Abstract In this present work, a statistical approach based on Taguchi Techniques and finite element analysis were adopted to determine the formability of conical cup using warm deep drawing process. The process parameters were temperature, coefficient of fric-tion, strain rate and blank holder velocity. The experimental results were validated using a finite element software namely D-FORM. The AA1050–H18 sheets were used for the superplastic deep drawing of the conical cups. The strain rate by itself has a significant effect on the effective stress and the height of the conical cup drawn. The formability of the conical cups was outstand-ing for the surface expansion ratio greater than 2.0.
Keywords: AA1050-H18, superplastic deep drawing, blank holder velocity, temperature, coefficient of friction, strain rate, conical cups, formability.
Extrusion, Drawing, Forging and Sheetmetal working processesmulualemamar
This Material presents about metal forming processes from those it slides about bulk deformation and sheet metal working processes includes (extrusion, drawing, forging and sheet metal operations).
Sheet Metal Working, Temperature and sheet metal forming, Applications Sheet Metal Parts, Categories of sheet metal processes, Shearing, stages in shearing action, Punch and Die Sizes, Sheet Metal Bending
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Ch6 sheetmetw proc (1) Erdi Karaçal Mechanical Engineer University of Gaziantep
1. 2.11.2014 CHAPTER 6 SHEET METAL
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CHAPTER 6
SHEET METAL WORKING PROCESSES
6.1 INTRODUCTION
ME 333 PRODUCTION PROCESSES II
Sheet metalworking includes cutting and forming operations performed on
relatively thin sheets of metal (0.4-6 mm).
The tooling used to perform sheet metalwork is called punch and die. Most sheet
metal operations are performed on machine tools called presses.
The term stamping press is used to distinguish these presses from forging and
extrusion presses. The sheet metal products are called stampings.
The commercial importance of sheet metalworking is significant.
The number of consumer and industrial products that include sheet metal parts:
automobile and truck bodies, airplanes, railway cars and locomotives, farm
and construction equipment, small and large appliances, office furniture,
computers and office equipment, and more. Sheet metal parts are generally
characterized by high strength, good dimensional tolerances, good surface finish,
and relatively low cost.
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Sheet-metal processing is usually performed at room temperatures (cold working).
The exemptions are when the stock is thick, the metal is brittle, or the deformation
is significant.
These are usually cases of warm working rather than hot working.
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The three major categories of sheet-metal processes:
(1) cutting (shearing, blanking, piercing)
(2) bending
(3) drawing.
Cutting is used to separate large sheets into smaller pieces, to cut out a part
perimeter, or to make holes in a part.
Bending and drawing are used to form sheet metal parts into their required
shapes.
Piercing and Blanking Cut off Lancing
blank scrap
blanking piercing
scrap
Final shape required
Fig.6.1 Some cutting operations
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Classification of Sheet
Metalworking Processes
Fig.6.2 Basic sheet
metalworking
operations:
(a) bending,
(b) drawing, and
(c) shearing;
(1) as punch first
contacts sheet and
(2) after cutting.
Force and relative
motion are indicated
by F and v
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Classification of Sheet Metalworking Processes
Fig.6.2 Basic processes involved in forming sheet metal components. (a) Processes involving
local deformation.
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6.2. PIERCING AND BLANKING
A commonly used piercing-blanking die set and related terms are shown in the
following figure.
Fig.6.3 Components of a punch and die
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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:
Starting stock produced
by shearing operation
from a big metal sheet
Fig.6.4 Steps
in production
of washer
8. Blanking punch diameter= Db-2c
Blanking die diameter= Db
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The cutting of metal between die components is a shearing process in which the
metal is stressed in shear between two cutting edges to the point of fracture, or
beyond its ultimate strength.
The metal is subjected to both tensile and compressive stresses; stretching beyond
the elastic limit occurs; then plastic deformation, reduction in area, and, finally,
fracturing starts and becomes complete.
Hole punch diameter= Dh
Hole die diameter= Dh+2c
Fig.6.5 Shearing of sheet metal
between punch and die
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ME 333 PRODUCTION PROCESSES II
The cutting of metal between die components is a shearing process in which the
metal is stressed in shear between two cutting edges to the point of fracture, or
beyond its ultimate strength. The metal is subjected to both tensile and
compressive stresses; stretching beyond the elastic limit occurs; then plastic
deformation, reduction in area, and, finally, fracturing starts and becomes complete.
Fig.6.5 Shearing of sheet metal between punch and die
10. Fig. 6.6. Shearing of sheet metal
between two cutting edges:
(1) just before the punch contacts
2.11.2014 CHAPTER 6 SHEET METAL
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Engineering analysis of metal cutting:
Cutting of sheet metal is accomplished by a shearing action between two sharp edges. The
shearing action is illustrated in the figure:
Fig.6.3 Shearing
work;
(2) punch begins to push into
work, causing plastic
deformation;
(3) punch compresses and
penetrates into work, causing a
smooth cut surface; and
(4) fracture is initiated at the
opposing cutting edges that
separate the sheet.
Symbols v and F indicate motion
and applied force, respectively.
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At the top of the cut surface is a region
called the rollover. This corresponds to
the depression made by the punch in the
work prior to cutting. It is where initial
plastic deformation occured in the work.
Just below the rollover is a relatively small
region called the burnish. This results
from penetration of the punch into the
work before fracture began.
Beneath the burnish is the fractured
zone, a relatively rough surface of the cut
edge where continued downward
movement of the punch caused fracture of
the metal.
Finally, at the bottom of the edge is a
burr, a sharp corner on the edge caused
by elongation of the metal during final
seperation of the two pieces.
12. ME 333 PRODUCTION PROCESSES II
6.2.1. Engineering Analysis_CLEARANCE
Process parameters in sheet metal cutting are clearence between punch and die,
stock thickness, type of metal and its strength and length of the cut
Clearance c in a shearing operation is the space between the mating members of
a die set (e.g.punch and die).
For optimum finish of cut edge, proper clearance is necessary and is a function
of the kind, thickness, and hardness of the work material.
In an ideal cutting operation the punch penetrates the material to a depth equal to
about 1/3 of its thickness before fracture occurs, and forces an equal portion of
the material into the die opening.
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Common die clearances (linear clearance) are 2-5% of the material thickness.
Angular clearance is gradient given to the hole in the die such that cut material will
easily be removed. Angular clearance is usually ground from 0.25⁰ to 1.5⁰ per side.
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The correct clearance depends on sheet-metal type and thickness t:
c = a*t
where a is the allowance (a = 0.075 for steels and 0.060 for aluminum alloys).
If the clearance is not set correctly, either an excessive force or an oversized burr
can occur:
Fig.6.7 Effect of clearance:
(Left) clearance too small
causes less than optimal
fracture and excessive
forces, and (Right) clearance
too large causes oversized
burr.
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Figure (a) Effect of the clearance, c, between punch and die on the
deformation zone in shearing.
As the clearance increases, the material tends to be pulled into the die rather
than be sheared. In practice, clearances usually range between 2% and 10%
of the thickness of the sheet. (b) Microhardness (HV) contours for a 6.4-mm
(0.25-in) thick AISI 1020 hot-rolled steel in the sheared region.
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The calculated clearance value must be;
- substracted from the die punch diameter for blanking operations or
- added to die hole diameter for punching:
Fig.6.8
Die diameter is enlarged with clearance c in punching.
In blanking, the punch diameter is decreased to account for clearance.
D is the nominal size of the final product.
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ME 333 PRODUCTION PROCESSES II
An angular clearance must be provided for the die hole to allow parts to drop
through it:
Fig.6.9 Angular clearance
for the die opening in
punching and blanking.
17. ME 333 PRODUCTION PROCESSES II
P DtS
P SLt
(for round holes)
(for any contours)
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6.2.2. CUTTING FORCE
The pressure (or stress) required to cut (shear) work material is;
For example to produce a hole of 20mmX20mm in a material 2mm in
thickness with 40 kg/mm2 shear strength:
P= 40 kg/mm2x(2x20+2x20)mmx2mm
P= 40x160 kg= 6400 kg force is required.
where;
S= shear strength of material, kg/mm2
D= hole diameter, mm
L= shear length, mm
t= material thickness, mm
18. ME 333 PRODUCTION PROCESSES II
Simple dies
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6.2.3 TOOLS AND DIES FOR CUTTING OPERATIONS
When the die is designed to perform a single operation (for example, cutting,
blanking, or punching) with each stroke of the press, it is referred to as a simple
die:
Fig.6.10 The basic components of the simple blanking and punching dies
19. Multi-operational dies
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More complicated pressworking dies include:
• compound die to perform two or more operations at a single position of the
metal strip
• progressive die to perform two or more operations at two or more positions of
the metal strip
Fig.6.11 Method of making a simple washer in a compound blanking and punching die
20. 2.11.2014 CHAPTER 6 SHEET METAL
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ME 333 PRODUCTION PROCESSES II
Multi-operational dies
Schematic illustrations: (a) before and (b) after
blanking a common washer in a compound die.
Note the separate movements of the die (for
blanking) and the punch (for punching the hole in
the washer). (c) Schematic illustration of making a
washer in a progressive die. (d) Forming of the top
piece of an aerosol spray can in a progressive die.
Note that the part is attached to the strip until the
last operation is completed.
21. ME 333 PRODUCTION PROCESSES II
r
α 3
rSin
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6.2.4 CENTRE OF PRESSURE
Sheet metal part that to be blanked is of irregular shape the summation of
shearing forces on one side of the center of the ram may greatly exceed the
forces on the other side. This result in bending and undesirable deflections might
happen. Center of pressure is a point, which the summation of shearing forces
will be symmetrical. This point is the center of gravity of the line that is the
perimeter of the blank. It is not the center of gravity of the area.
y
2
r
x y
2
a b
x
h
3
y
Fig.6.14 Center of pressure for some shapes
22. ME 333 PRODUCTION PROCESSES II
l x l x l x
lx
....
1 1 2 2 3 3
l y l y l y
1 1 2 2 3 3
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Procedure to find center of pressure:
1. Divide cutting edges into line elements, 1,2,3, ...
2. Find the lengths l1, l2, l3, ...
3. Find the center of gravity of each element as x1, x2, x3, ..., y1, y2, y3, ...
4. Calculate the center of pressure from:
l
l l l
x
....
1 2 3
ly
l
l l l
y
....
....
1 2 3
23. Find the center of pressure and the required cutting force of the following blank
(S=40 kg/mm2 and t=2mm).
.
3592
. cm
x 189
.
11598
y 610
2.11.2014 CHAPTER 6 SHEET METAL
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ME 333 PRODUCTION PROCESSES II
EXAMPLE
1
2
3
4
5
6
Element l X Y (l)(x) (l)(y)
1 4.00 0.00 6.25 0.00 25.00
2 4.71 1.50 9.20 7.05 43.33
3 3.20 4.00 7.00 12.80 22.40
4 2.50 4.00 5.00 10.00 12.50
5 3.00 1.50 4.25 4.50 12.75
6 1.57 1.00 0.00 1.57 0.00
TOTAL 18.98 35.92 115.98
. cm
.
1898
.
1898
and the cutting force is;
P= LtS 189.8mmx2mmx40kg/mm2 =15184 kg
24. Since cutting operations are characterized by very high forces exerted over very
short periods of time, it is some times desirable to reduce the force and spread it
over a longer portion of the ram stroke.
Two methods are frequently used to reduce cutting forces and to smooth out the
heavy loads.
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ME 333 PRODUCTION PROCESSES II
6.2.5 REDUCING CUTTING FORCES
1. Step the punch lengths; the load may thus be reduced approx. 50%.
2. Tapering the punch; grind the face of the punch or die at a small shear angle
with the horizontal. This has the effect of reducing the area in shear at any time,
and may reduce cutting force as much as 50%. The angle chosen should
provide a change in punch length of about 1.5 times of material thickness. It is
usually preferable to a double cut to prevent setup of lateral force components.
Fig.6.15 Different configurations 0.25+t
for reducing the cutting force
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ME 333 PRODUCTION PROCESSES II
Fig.6.– Effect of different clearances when punching hard and soft alloys
26. In designing parts to be blanked from strip material, economical strip utilization is of
high importance. The goal should be at least 75% utilization.
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ME 333 PRODUCTION PROCESSES II
6.3 SCRAP-STRIP LAYOUT FOR BLANKING
where;
t : thickness of the stock,
W: width of the stock,
B: space between part and edge (1.5t),
C: lead of the die (L+B),
L&H: dimensions of the work piece.
27. Scrap
Util
Scrap 100
2.11.2014 CHAPTER 6 SHEET METAL
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ME 333 PRODUCTION PROCESSES II
Locating the work piece for maximum economy is very important.
% X100
Total
.
% . X
Total
Util
28. HOMEWORK:
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ME 333 PRODUCTION PROCESSES II
If two strips (250 mm and 125 mm width) are available for the production of 100
mm blanks, which one have to be preferred for maximum material utilization?
29. ME 333 PRODUCTION PROCESSES II
6.4 BENDING
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Bending is defined as the straining of the sheet metal around a straight edge:
Fig.6.15 Bending of sheet metal
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ME 333 PRODUCTION PROCESSES II
Bending operations involve the processes of V-bending and edge bending:
Fig.6.16 (Left) V-bending, and (Right) edge bending; (1) before and (2) after bending
•V-bending—sheet metal is bent along a straight line between a V-shape punch and die.
•Edge bending—bending of the cantilever part of the sheet around the die edge.
31. Bending is the process by which a straight length is transformed into a curved
length. It is a very common forming process for changing sheet and plate into
channel, tanks, etc.
For a given bending operation the bend radius can not be made smaller than a
certain value, otherwise the metal will crack on the outer tensile surface. Minimum
bend radius is usually expressed in multiples of the sheets thickness. It varies
considerable between different metal and always increases with cold working. Bend
radius is not less than 1 mm and for high strength sheet alloys the minimum bend
radius may be 5t or higher.
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R - bend radius
BA - bend allowance
- bend angle
L0 - original length
t - sheet thickness
Lf L0
Lf=L1+L2+BA Rmin>5t practical
32. ME 333 PRODUCTION PROCESSES II
where Lb is the length of the blank, L are
the lengths of the straight parts of the
blank, BA is the bend allowance,
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This is the stretching length that occurs
during bending. It must be accounted to
determine the length of the blank,
Fig.6.17 Calculation of bend allowance
where A is the bend angle; t is the sheet thickness;
R is the bend radius; Kba is a factor to estimate stretching,
defined as follows:
Kba = 0.33 for R < 2t
Kba = 0.50 for R ≥ 2t
33. 1 min
r t A
2
( 1
A )
r
A A
A A
r A
2
R t/
o
f
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The minimum bend radius for a given thickness of sheet can be predicted fairly
accurately from the reduction of area measured in tension test, Ar.
1
2
R
2
min
2
r r
t
R
for Ar< 0.2,
for Ar> 0.2,
o f
o
A
Another common problem is springback. It is the dimensional change of the formed
part after pressure of the forming tool has been removed. It results from the change
in strain produced by elastic recovery.
2
R t/
Springback ratio
f
o
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The commonest method of compensating for springback is to bend the part to a
smaller radius of curvature than is desired so that after springback the part has
the proper radius.
Springback is the elastic recovery leading to the increase of the included angle
when the bending pressure is removed.
To compensate for springback two methods are commonly used:
1. Overbending—the punch angle and radius are smaller than the final ones.
2. Bottoming—squeezing the part at the end of the stroke.
Fig.6.18 Springback in bending
Fig.6.19 Compensation of springback by:
(a) and (b) overbending; (c) and (d) bottoming
35. Lt
2
R t
P o
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The force required bending a length L about a radius R may be estimated from;
2
tan
2(
/2)
Bending forces
The maximum bending force is estimated as
where Kbf is the constant that depends on the process, Kbf = 1.33 for V-bending
and Kbf = 0.33 for edge bending; w is the width of bending; D is the die opening
dimension as shown in the figure:
Fig.6.20 Die opening dimension D,
(a) V-bending, (b) edge bending
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Equipment for bending operations
Fig.6.21 Press brake with CNC gauging system Fig.6.22 Dies and stages in the press brake
forming of a roll bead
37. ME 333 PRODUCTION PROCESSES II
6.5 DEEP DRAWING (Derin Çekme)
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Deep drawing is the metal working
process used for shaping flat sheets
into cup-shaped articles such as
bathtubs, shell cases, and
automobile fenders. Generally a hold
down or pressure pad is required to
press the blank against the die to
prevent wrinkling. Optional pressure
pad from the bottom may also be
used.
Fig.6.23 Drawing of a cup shaped part
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Deep drawing of a cup-shaped part
Fig.6.24 Deep drawing of a cup-shaped part: (Left) start of the
operation before punch contacts blank, and (Right) end of stroke
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In the deep drawing of a cup the metal
is subjected to three different types of
deformations. In the flange part, as it is
drawn in, the outer circumference must
continuously decrease from that of the
original blank Do to that of the finish
cup Dp. This means that it is
subjected to a compressive strain in the
hoop (tangential) direction and a tensile
strain in the radial direction. As a result
of these principal strains, there is a
continual increase in the thickness as
the metal moves inward. However, as
the metal pass over the die radius, it is
first bend and then straightened while
at the same time being subjected to a
tensile stress. This plastic bending
under tension results in considerable
thinning. Punch region is under very
little stress.
Fig.6.23 Types of deformations in different region
during deep drawing of a cup shaped part
40. ME 333 PRODUCTION PROCESSES II
Clearance
Clearance c is the distance between the punch and die and is about 10% greater
than the stock thickness:
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c = 1.1t
Holding force
The improper application of the holding force can cause severe defects in the
drawn parts such as (a) flange wrinkling or (b) wall wrinkling if the holding force is
too small, and (c) tearing if the folding force is overestimated.
Fig.6.25 Defects in deep drawing of a cup-shaped part
41. D
d
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The force on the punch required to produce a cup is the summation of the ideal
force of deformation, the frictional forces, and the force required to produce
ironing. Mathematical calculation of the drawing force is very complex. Following
approximate equation is developed:
P dt n
H
d
D
e B o
11 2 2 . /
where;
P = total punch load, o= average flow stress,
d = punch diameter, D = blank diameter,
H = hold drawn force, B = force required to bend,
t = wall thickness, = coefficient of friction,
= efficiency
Drawing force may be calculated for practical purposes by:
P dt o when LDR 2 (Limiting Drawing Ratio)
42. D
LDR
D d 4dh 2 and
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The drawability of a metal is measured by the ratio of the blank diameter to the
diameter of the cup drawn from the blank (usually accepted as punch diameter). For
a given material there is a Limiting Drawing Ratio (LDR), representing the largest
blank that can be drawn through a die without tearing.
e
d
Where, is an efficiency term to account for frictional losses. If =1, then LDR=2.7
while =0.7, LDR2 which is used in most practical applications.
Some of the practical considerations which affect drawability:
Rd 10t
Rp should be big enough to prevent tearing.
Clearance between punch and die; 20 to 40% greater than “t”.
Hold-down pressure; 2% of o and lubricate die walls
The diameter of blank required to draw a given cup may be obtained approximately
by equating surface areas.
where; h is height of cup.
D d
dh
2 2
4 4
43. 1st draw
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If the shape change required by the part design is too severe (limiting drawing ratio is
too high, or LDR is not sufficient to form a desired cup), complete forming of the part
require more than one drawing step. The second drawing step and any further
drawing steps if needed, are referred to as redrawing. Throat angle is 10-15.
Redrawing is generally done in decreasing ratios as given below:
(D/d)= 1.43, 1.33, 1.25, 1.19, 1.14 and 1.11.
If these redrawing steps are not enough to reach required cup diameter, annealing
have to be performed and then redrawing can be performed.
last draw
6.5.1 REDRAWING
Fig.6.26 Redrawing of a cup
44. 6.5.2 EXAMPLE:
Draw 1st 2nd 3rd 4th 5th 6th
Ratio 1.43 1.33 1.25 1.19 1.14 1.10
Solution:
LDR=2 D/d = 200/50 = 4 > 2
So that redrawing is necessary.
200
D
1. 139.86
139.86
D
1 D
D
105.16
2 D
D
D
3 D
D
D
4 D
D
D
5 D
D
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A 200 mm blank is to be drawn to a 50 mm cup. Estimate the minimum number of
draws required using the drawing ratios given below:
56.38>50
1.43
1.43 1
1
D
D
2. 105.16
1.33
1.33 2
2
3. 84.13
1.25
1.25 3
3
D
84.13
4. 70.69
1.19
1.19 4
4
70.69
5. 62.01
1.14
1.14 5
5
62.01
6. 56.38
1.1
1.1 6
6
45. 84.13
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Therefore annealing should be applied. But it might be better to anneal the blank
before 6th draw to reduce number of redraws. We know that LDR=2. So that if
annealing is performed after 3rd draw where D3 = 84.13 mm, than ratio to reach
required cup diameter is:
1.68
50
< 2
Therefore, after 3rd draw, blank is annealed and then redraw with a ratio of 1.68 to
obtain required cup diameter. The required number of drawing is then 4.
46. ME 333 PRODUCTION PROCESSES II
6.6 OTHER SHEET-METAL FORMING OPERATIONS
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The Guerin process involves the use of a thick rubber pad to form sheet metal
over a positive form block:
Fig.6.27 The Guerin process: (Left) start of the operation before
rubber pad contacts sheet, and (Right) end of stroke
The Guerin process
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Examples of equipment and products manufactured by the Guerin process:
Fig.6.28 Rubber pad press showing
forming tools on the press table
Fig.6.29 A large number of different components
can be made simultaneously during one press cycle
with rubber pad presses
Advantages: small cost of tooling
Limitations: for relatively shallow shapes
Area of application: small-quantity production
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It is similar to Guerin process but instead of rubber pad a rubber diaphragm
filled with fluid is used:
Fig.6.30 Hydroform process:
(1) start-up, no fluid in the cavity;
(2) press closed, cavity pressurized
with hydraulic fluid;
(3) punch pressed into work to form
part.
Symbols:
v - velocity,
F – applied force, and
p - hydraulic pressure
Hydroforming
Advantages: small cost of tooling
Limitations: simple shapes
Area of application: small-quantity production
49. Stretch forming
In stretch forming the sheet metal is stretched and bent to achieve the desired shape:
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Fig.6.31 Stretch forming: (1) start of the process; (2) form die is pressed into the work
causing it to stretched and bent over the form. Symbols: v - velocity, Fdie - applied force
Advantages: small cost of tooling, large parts
Limitations: simple shapes
Area of application: small-quantity production
50. Spinning
Spinning is a metal forming process in which an axially symmetric part is gradually
shaped over a mandrel by means of a rounded tool or roller:
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Fig.6.32 In spinning operation, flat circular blanks are often formed into hollow shapes such
as photographic reflectors. In a lathe, tool is forced against a rotating disk, gradually forcing
the metal over the chuck to conform to its shape. Chucks and follow blocks are usually
made of wood for this operation
Advantages: small cost of tooling, large parts (up to 5 m or more)
Limitations: only axially symmetric parts
Area of application: small-quantity production
51. HIGH-ENERGY-RATE FORMING (HERF)
These are metal forming processes in which large amount of energy is applied in a
very short time. Some of the most important HREF operations include:
Explosive forming
It involves the use of an explosive charge placed in water to form sheet into the die cavity.
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Fig.6.33 Explosive forming: (1) set-up, (2) explosive is detonated, and (3) shock wave
forms part
52. Explosively formed elliptical dome 3-m in diameter being removed from
the forming die
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Fig.6.34 Explosively formed elliptical
dome 3-m in diameter being
removed from the forming die
Advantages: small cost of tooling, large parts
Limitations: skilled and experienced labor
Area of application: large parts typical of the aerospace industry
53. Electrohydraulic forming
This is a HREF process in which a shock wave to deform the work into a die cavity is
generated by the discharge of electrical energy between two electrodes submerged
in water. Similar to explosive forming, but applied only to small part sizes.
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Fig.6.35 Setup of electrohydraulic forming
54. Electromagnetic forming
The sheet metal is deformed by the mechanical force of an electromagnetic field
induced in the workpiece by a coil:
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Fig.6.36 Electromagnetic
forming: (1) set-up in which
coil is inserted into tubular
workpiece surrounded by
die, (2) formed part
Advantages: can produce shapes, which cannot be
produced easily by the other processes
Limitations: suitable for magnetic materials
Area of application: most widely used HERF process to
form tubular parts
55. HOMEWORK:
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If two strips (250 mm and 125 mm width) are available for the production of 100
mm blanks, which one have to be preferred for maximum material utilization?
56. ME 333 PRODUCTION PROCESSES II
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THE END
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