ABSTRACT
The
metal bending machine is designed to be manually operated. The bending machine
with working capacity to complete a 900 fold of a full-length plate
(8 ft = 2400mm) and up to 2.5mm thickness. The construction is based on initial
machine design, materials. The machine can be used to perform any type of
bending. It consist of heavy beams which are coupled together to bring about
any shape of bending after the flat sheet has been marked out to specified
dimensions. It serves as invaluable equipment because it offers solution to the
technology of sheet metals in Nigeria.
TABLE OF
CONTENT
PAGES
Front
page………………………………………………………………………… i
Certification……………………………………………………………………….. ii-iii
Dedication……………………………………………………………………… iv
Acknowledgement……………………………………………………………. V
Abstract……………………………………………………………………………. vi
Table of
content……………………………………….…………………… vii-ix
Project
topic……………………………………………………………………. 1
Aim……………………………………………………………………………….. 1
Procedures………………………………………………………………………. 1
Selected materials…………………………………………………………… 2
Equipment………………………………………………………………………… 3
CHAPTER ONE
1.0 INTRODUCTION................................................................ 4
1.1 Importance of Sheet Metal Work and Bending Machines . 4-9
1.2 Historical Review and Classification of Bending Machines. 9-12
1.3 Operational Characteristic of the Bending Machine………. 12-14
CHAPTER TWO
2.0 BENDING TECHNOLOY…………………………………………………………………. 15
2.1 Principles of Bending………………………………………………. 15-17
2.2 The mechanics of Bending……………………………………….. 17-19
2.3 Plastic Deformation Due to Bending…………………………… 20-21
2.4 Spring Back……………………………………………………………… 21-22
2.5 Method for Compensating Spring Back…………………… 22-16
2.6 Method of Determining Angle of Spring Back……………… 26-27
CHAPTER THREE
3.0 DESIGN CONSIDERATION………………………………………… 28
3.1 Bending Stress…………………………………………………………… 28-31
3.2 Material Selections………………………………………………………… 32
3.2.1 Physical Properties of Metal…………………………………………. 32-33
3.2.2 Mechanical Properties of Metal…………………………………….. 34-38
3.3 Material Selection Table……………………………………………….. 39
CHAPTER FOUR
4.0 COMPONENT DESIGH,
CONSTUCTION,
CHAPTER FIVE
5.0 ANALYSIS…………………………………………………………………… 54
5.1 Construction………………………………………………….…………….. 55
5.2 Anticipated Faults and Corrections…………….………………..… 55-56
5.3 Maintenance…………………………………………………………………56-57
5.4 Conclusion……………………………………………………………………. 57
5.5 Recommendations………………………………………………………… 58
References……………………………………………………………………
CHAPTER ONE
1.0
INTRODUCTION
1.1
Importance of Sheet Metal Work and Bending
Machine
What is a metal? It is a
strong shinny, which conducts electricity and melts when you make it hot
enough. But surely metal must be something more than this because there are
other substances such as carbon,, glass and rubbers, which are, obviously not
metals but can also variously claim to have strength, elasticity or electrical
conductivity.
Furthermore, most of the
metals will melt when heated sufficient. What then is a metal? A study of
simple metallurgy will show that there is one important factor, which
distinguishes metals from non-metals and that is the neat, orderly arrangement
of the atoms into regular geometric molecules. Metal is a good conductor of
heat and electricity and forming basic oxides.
An alloy is a fused mixture
or compound of two or more pure metals. The reasons for making these mixtures
are many and various. Pure metals have certain desirable properties but are
often lacking in other ways. Therefore it is necessary to mix other metals with
them in order to preserve and improve their basic properties. To quote a well
known example: Aluminum is a light weight metal which makes it useful for
aircraft construction, but it is also soft and weak so a small quantity of
copper is added to it to give the necessary strength and rigidity (Courtesy,
1980).
The subsequent development of
iron and steel to suit its use in various forms enables it to serve effectively
wherever used. Iron and steel remains the most vastly used material for
structural works, enclosures and packages.
The most popular forms of
iron and steel remains the sheet form, mostly used in enclosure and vessel
fabrication. The term metal sheet refers to lighter gauges of steel in rolled
form ranging in thickness from approximately 0.4mm to 3.2mm. (Surenda singh,
1979).
Many engineering components
are produced from flat sheets of metal which are cut to shape and then folded
to form the finished article. The edges are then secured by a variety of
methods such as welding, soldering and riveting. The accuracy of the size of
drawing the shape on the flat sheet know as the development. Allowance is made
at this stage for folding or bending, the amount varying with the radius of the
bend and the metal thickness.
Quite a large of sheet metal
is employed in the manufacturing industries, in building of aircrafts,
automobiles and household appliances. Sheet metal to a large extent is used in
the building industries for roofing, heating, prefabricated structures and air
conditioning casings.
The base metal iron and
bronze were appreciated for their strength especially for weapons and tools;
copper, tin and lead came to be used mainly for their utility or durability-
for cooking, for storage or for strengthening wooden construction of any kind.
The particular property of
metals that can be mixed or alloyed in various combinations and proportions to
make a better materials for particular purposes was understood in the ancient
world. Copper and tin produces bronze; copper and zinc produces brass; lead and
tin produces pewter. This property has been exploited with ingenuity and
increasing scientific knowledge while the designation iron, copper, lead,
silver and gold are still commonly used (Surenda, 1979).
All metals shares certain
characteristic: a uniform smooth complexion; great strength and tenacity; but
also easily worked surface; and malleability (their capacity to assume any
desired shape).
All these are carried out
with the help of sheet metal works, which involves fabrication of metallic
objects by cutting, forming/ bending and fastening, welding etc. are referred
as sheet metal works. (Oyewole and Agada, 2000).
The term bending refers to an
operation in which metal is deflected from its original form to a new position
generally at an angle or a curve and it remains so permanently. Bending is a
common metalworking technique to process sheet metal. It is usually done by
hand on a box and pan brake, or industrially on a press brake. Typical products
that are made like this are boxes; such as electrical enclosures, rectangular
ductwork and some firearm parts.
Usually, bending has to
overcome both tensile stress as well as comprehensive stress. When bending is
done the residual stresses make it spring back towards its original position,
so we have to over bend the sheet metal keeping in mind the residual stresses.
The machine used for bending
operation is called sheet metal bending machine. This machine can be used to
perform any type of bending. It consists of heavy beams, which are coupled
together to bring about any shape of bending after the flat sheet has been
marked out to a specific dimension of bending. This machine is extensively used
in our community today by steel fabricators and production workshops for the
fabrication of iron gates, security doors, burglary proofs, Louvre frames etc.
(Oyewole and Agada 2000).
The street metal bending
machine has great importance. It is used for bending metal sheet into shape and
it is also used for giving out design.
1.2
Historical Review and Classification of Bending
Machines
Over the years tremendous
efforts have been made both in the study, design and development of tolls and
machinery employed in manipulating sheet metal into desired shape mostly by
bending.
The earliest approach to
bending sheet metal to desire shape involves the use of stakes (thick or strong
sharpened stick driven into the ground as a support, boundary, mark etc.)
alongside hand tools of wood or rubber mallet, bench socket positioned at right
angle to the craft-man. Stakes are of different types and forms corresponding
from the type of bend to be made. The finishing achieved from this is generally
poor and not very accurate. It’s other dements lie in the much labour required
and limitation of the length of the sheet that can be bent.
To overcome these demerits
and boost the fabrication industry, machine to carry out the bending operation
were thereby developed. Bending machine in use include pinch bending rolls,
power operated pyramid rolls, lock forming machine, Timman’s Jenny, Swing beam.
The cramp folding machine; had operated geared bending machine, the box is the
most versatile and easy to operate of all bending machines.
A top Vee-shaped blade
descends on the plate, forming the necessary bend in vee- shaped bottom die.
Top blades could be in varying width thus allowing box forms to be produced.
Fig 1.1: The press brake
The swing beam is a manually operated bending
machine and it is extensively used in our community today by steel fabricators
and production workshops. It is extensively used because it does not require
electricity. The swing beam bending machine is easy to operate and it can bend
a metal sheet of about 2.5mm.
DESIGN
The sheet metal bending machine that is
designed and reported here is the swing beam type consisting of a clamping
beam, bending beam, machine bed, supporting frame and the bend
Fig 1.2: Sketch o a metal the machine
1.3 Operation Characteristic
of the Bending Machine
The
design is such that will carry out vee-shape angle bend on a sheet metal of
maximum thickness of 2.5mm and maximum width of 8ft (2 1 . e. a standard sheet metal plate length. A sheet metal
thickness above 2.5mm cannot be bend by this machine but can be bent by a press
brake. Press brake may be of either mechanical or hydraulic operation i.e. the
power to drive the press is by a flywheel or by hydraulic rams (khurmi and
Gupta, 1979).
1.
The
essential components of the bending machine are:
2.
Clamping
beam with threaded shaft, it hold the sheet metal to the machine bed.
3.
Machine
bed, it houses the sheet to be bent.
4.
Bending
beam, this ensures the folding of the sheet metal.
5.
Pedestal,
it supports the entire machine.
Turning the threaded shaft
anti-clockwise, the bending beam lift up and an opening created, then, metal
strip can be slotted into the machine for bending. Turning the shaft clockwise
the bending beam comes or clamp down onto the machine bed, the sheet is clamped
in between the clamping beam and the machine bed. By lifting the folding handle
/bending lever up, the sheet metal bends into shape. The handle is released,
the shaft (threaded) is turned anti-clockwise and the sheet is removed.
A back gauge is provided to control the length
of sheet that enters into the machine for bedding in case where sheets to be
cut are smaller in length between the back gauge and the bending zone. Metal
sheets are measured and marked; the marked portion is placed alongside the edge
of the folding blade.
Fig
2.1: Basic bends and bend elements
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