Sheet
metal processes are versatile processes used in metal forming industries. Due to
its various advantages, sheet metals are widely used in manufacturing industries. All cars
bodies, metal doors, fan blades, metal desks etc. are sheet metal products. There
are various processes to transform sheets into required product. These processes can be classified into three ways.
1. Sheet Metal Cutting Process
2. Sheet Metal Bending Process
3. Deep Drawing
In my last article, we have learnt about various sheet metalcutting processes. In this article we mainly focus on sheet metal bending
processes.
Let’s start the discussion.
Sheet Metal Bending:
Bending is a most common sheet metal forming operation. Many
products like automobile components and its body, home appliance, paper clip, metal
doors etc. are shaped by bending process. Before discussing about bending
process and its types, first you should learn about basic terminologies used in
bending. It will help you to clearing understanding of process and its various
parameters. These are given below.
Bending Terminology:
Neutral Axis:
It is an imaginary axis which does not undergo any stress during bending.
Outer Fibers:
Those fibers which are under tension during bending process,
known as outer fibers. These are at one side of the neutral axis. It is shown by red color in figure.
Inner Fibers:
Those fibers which are under compression during bending
process, known as inner fibers. These fiber are shown by blue color in figure.
Bend Allowance:
The length of the neutral axis in the bend zone is known as
bend allowance.
Bend Angle:
The angle form by the bend area at the center of bend is
known as bend angle.
Bend Radius:
Distance between bend center and neutral axis is known as
bend radius. It is denoted by r.
Minimum Bend Radius:
The minimum bend radius is the bend radius at which a crack
appears on the outer surface of the bend. It is usually expressed in term of sheet
thickness, such that 2T, 3T, 4T etc. It is different for different material.
Springback:
When load is removed, the sheet metal shows some elastic recovery
and tends to achieve its original position. This phenomenon is called
springback. It will increase the final bend radius and decrease the bend angle
after spingback.
Bending is a process in which the metal is deform in such a
way that the length and thickness before bending and after bending remains same. It
only changes shape of the work piece. Actually it is an ideal condition but
practically length and thickness changes up to some extent in bend area.
Every metal when subjected to a moment or couple, it tends to bend. Sheet
metals have high bending ability which makes it versatile for various shaping
and forming process.
Different Sheet Metal Bending Process:
These are most common bending process.
Press Brake Forming:
This process uses a mechanical or hydraulic press brake to
bend a sheet. This machine utilizes long dies to convert sheet into various
shapes. It is easiest way of bending and can be easily automated.
Roll Bending:
This process uses a three rollers set to bend a sheet by
adjusting the distance between rolls. This process can utilize to form various
curvatures.
Four Slide machine Bending:
This process uses three movable and one stationary slide to
bent a work sheets as shown in figure. This is used to bent small work pieces.
Beading:
It is a process in which the periphery of the sheet metal is
bent into the cavity of a die. It increases moment of inertial of the section and stiffness. It also eliminates exposed sharp edges.
Flanging:
It is a process of bending the edges of the metal sheet at perpendicular
to the length. It can be further divided according the shape like straight
flange, stretch flange, joggled flange, shrink flange etc. as shown in figure.
Dimpling:
It is a process in which first a hole in made into the sheet
metal and then it is expanded into a flange using punch die system.
Hemming:
It is an operation in which the edge of the sheet is folded
over itself. This process increases stiffness of the part and eliminate sharp
edges.
Roll Forming:
It is an continuous bending process used for long work piece. This
process uses a serious of rolls of various shapes according to the bending process.
The metal sheet allows to pass through these rolls and the part is sheared and
stacked continuously.
These are most common sheet metal bending processes. If you
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