Manufacturing OF MECHANICAL ENGINEERING UNIVERSITY OF ENGINEERING AND

Manufacturing
Process

Project
Report

(Spring)

 

 

Submitted to:

Dr
Azhar Hussain

Submitted by:

Muhammad
Hanzala    (15-ME-79)

 Fazeel Ahmad             (15-ME-81)

M
Asif Nawaz              (15-ME-82)

Umar
Iftikhar               (15-ME-85)

Asad
Aleem                (13-ME-35)

DEPARTMENT OF MECHANICAL ENGINEERING

UNIVERSITY OF ENGINEERING AND TECHNOLOGY

TAXILA

January 2018

 

Spring

Definition:

A spring is
an elastic object that
stores mechanical energy. Springs are
typically made of spring steel. There are many
spring designs. In everyday use, the term often refers to coil springs.

Explanation:

When a conventional spring, without stiffness variability
features, is compressed or stretched from its resting position, it exerts an
opposing force approximately
proportional to its change in length (this approximation breaks down for larger
deflections). The rate or spring constant of a spring is the
change in the force it exerts,
divided by the change in deflection of the
spring. That is, it is the gradient of the force
versus deflection curve. An extension or compression spring’s rate
is expressed in units of force divided by distance, for example lbf/in or N/m.
A torsion spring is a spring
that works by twisting; when it is twisted about its axis by an angle, it
produces a torque proportional
to the angle. A torsion spring’s rate is in units of torque divided by angle,
such as N·m/rad or ft·lbf/degree.
The inverse of spring rate is compliance, that is: if a spring has a rate of 10
N/mm, it has a compliance of 0.1 mm/N. The stiffness (or rate) of springs
in parallel is additive, as is the
compliance of springs in series.

History:

Simple non-coiled springs were used
throughout human history, e.g. the bow (and
arrow). In the Bronze Age more sophisticated spring devices were used, as shown
by the spread of tweezers in
many cultures. Ctesibius of Alexandria developed
a method for making bronze with
spring-like characteristics by producing an alloy of bronze with an increased
proportion of tin, and then hardening it by hammering after it was cast.

Types:

Springs can be classified depending on how the load force is
applied to them:

·       
Tension/extension
spring – the spring is designed to
operate with a tension load,
so the spring stretches as the load is applied to it.

 

 

 

 

·       
Compression
spring – is designed to operate with
a compression load, so the spring gets shorter as the load is applied to it.

 

 

·       
Torsion
spring –
unlike the above types in which the load is an axial force, the load applied to
a torsion spring is a torque or twisting force, and the end
of the spring rotates through an angle as the load is applied.

·       
Leaf
spring –
a flat spring used in vehicle suspensions,
electrical switches, and bows.

 

 

Hooke’s law:

As long as not stretched or compressed
beyond their elastic limit,
most springs obey Hooke’s law, which states that the force with which the
spring pushes back is linearly proportional to the distance from its
equilibrium length:

{displaystyle F=-kx, }

F=-kx

where

x is the displacement vector –
the distance and direction the spring is deformed from its equilibrium length.

F is the resulting force vector
– the magnitude and direction of the restoring force the spring exerts

k is the rate, spring constant or force constant of the spring, a constant that
depends on the spring’s material and construction. The negative sign indicates
that the force the spring exerts is in the opposite direction from its
displacement

 

Design
Limitations:

Depending on what kind of spring you want to design, and depending on
where it will be

Used, your design
will be limited:

For
Compression Springs:

• If the spring will set solid (compress all the way, so that all the
coils touch each other) at the limit of its travel, the diameter of the wire
times the number of coils cannot be greater than the space allowed, unless you
want the spring itself to act as a mechanical stop to the motion.

• Springs that operate in a high-temperature environment (like for
instance inside an engine will need to be made slightly longer to compensate
for the fact that the heat may have an effect on the length of the spring. The
section on finishing will tell you more about this.

• As a compression spring assumes a load and shortens, the diameter of
the

Active coils will increase. This is only a problem when the spring has
to work in a confined space.

 

For Extension Springs:

• There should be some mechanical limit on how far the spring will
extend, or the spring will lose its shape and not return to its initial
condition with all coils closed.

• Extension springs operating in a high-temperature environment may have
to be coiled extra-tight, as the heat will tend to weaken the spring. The
section on extension springs will tell you more about this.

 

Uses:

§  Vehicles: Vehicle suspension

§  Watches: Balance
springs in
mechanical timepieces and spring-loaded bars for
attaching the bands and the clasps.

§  Mini Drill

§  Jewelry: Clasp mechanisms.

§  Lock mechanisms:
Key-recognition and for coordinating the movements of various parts of the
lock.

§  Pop-open devices: CD players, Tape recorders etc.

§  Pens

§  Spring
mattresses

§  Slinky

§  Trampoline

 

Material:

Steel alloys are the most commonly used
spring materials. The most popular alloys include high-carbon (such as the
music wire used for guitar strings), oil-tempered low-carbon, chrome silicon, chrome vanadium,
and stainless steel.

Other metals that are sometimes used to
make springs are beryllium copper alloy, phosphor bronze,
and titanium. Rubber or urethane may be used for cylindrical, non-coil springs.
Ceramic material has been developed for coiled springs in very high-temperature
environments. One-directional glass fibre composite materials are being tested
for possible use.

Future:

Demands of the rapidly growing computer
and cellular phone industries are pushing spring manufacturers to develop
reliable, cost-effective techniques for making very small springs. Springs that
support keys on touchpads and keyboards are important, but there are less
apparent applications as well. For instance, a manufacturer of test equipment
used in semiconductor
production has developed a micro-spring contact technology. Thousands of tiny
springs, only 40 mils (0.040 in or 1 mm) high, are bonded to individual contact
points of a semiconductor wafer. When this wafer is pressed against a test
instrument, the springs compress, establishing highly reliable electrical
connections.

Medical devices also use very small
springs. A coiled spring has been developed for use in the insertion end of a
catheter or an endoscope. Made of wire 0.0012 in (30 micrometres or 0.030 mm)
in diameter, the spring is 0.0036 in (0.092 mm) thick—about the same as a human
hair. The Japanese company that developed this spring is attempting to make it
even smaller.

Procedure:

·       
First of all take a coil of required material which is our desire.

·       
Straighten the wire which is used.

·       
Then take a circular rod of desired dia.

·       
Weld the wire with the rod and put the rod in to the chuck of
lathe.

·       
Set the lathe on minimum speed.

·       
Adjust the gear so that carriage move slowly.

·       
Fit the nut in the tool post and pass the wire through it.

·       
Then start the lathe the chuck will rotate as well as carriage
will move.

·       
Hold the wire strongly and tight it.

·        
As lathe and carriage moves the spring will be done.

Coiling:

If you’re using a lathe to make your
springs, you’ll be standing there, letting the lathe pull the wire. The lathe
will do what you want, but it will not know to stop if things get out of
control. So, before you start the lathe, figure out what you’re going to do if
things go haywire. Know how to stop the lathe, and know which way you can
safely run. Never reach over the wire to get to your lathe controls, especially
when working with heavy wire. Reach under it and avoid injury if your wire
guide breaks.

 Keep the lathe speed DEAD SLOW: with heavy
wire, 10 rpm is about right.

Don’t grab onto wire that’s being fed
into the lathe. Stop the lathe and back it off until there’s no tension in the
wire before you put your hands near.

Hand
tools:

You’ll need some basic hand tools:

• A vice (either floor- or
bench-mounted)

• Wire cutters (6″ diagonal)

• Needle-nose pliers

• Callipers (if dimensions are critical)

• Tape measure (if dimensions are rough)

• Crescent wrench

• Acetylene torch (if working with wire
over about .250″)

Workpiece:

 

 

 

Observations and
Calculations:

 

For spring 1

 

Material:
Copper

No. of turns= 15

Length of
spring=
25cm

Pitch= 2cm

Diameter of
spring coil= 3.4cm

Length of wire=
163.28cm

 

For spring 2

 

Material:
Stainless Steel

No. of turns= 16

Length of
spring=
11.5cm

Pitch=
1.7cm

Diameter of
spring coil= 1.8cm

Length of wire=
91.06cm

 

Conclusion:

·       
It is concluded that
the spring making depends on the material of the spring. We have to choose
material wisely, it should be ductile, stiff and durable.

·       
Secondly, while making
spring the lathe speed is also very important to observe.

·       
Wire should be held tight
it is being wound on the lathe.

 

References:

·       
Wahl, A. M. (1944). Mechanical springs. Machine Design Series, 1st
Edition

·       
Khurmi, R. S. and Gupta, J. K. (2010).
Machine Design, 14th Edition

·       
Wright, R. N. (2010). Wire Technology:
Process Technology and Metallurgy, 2nd Edition

·       
article.sapub.org

·       
www.scribd.com

·       
www.wikipedia.com