KME

1. INTRODUCTION
A new machine is born because there is a real or imagined need for it. It evolves from
someone’s conception of a device with which to accomplish a particular purpose. From the
conception follows a study of the arrangement of parts, the location and length of links, the places
of gears, bolts, springs, cams and other elements of machines. With all ideas subject to change and
improvement, several solutions may be and usually are found, the seemingly best one being chosen.
“Design” is defined as formulation of a plan or a procedure for the satisfaction of human
need. “Mechanical Engineering design” is a major segment of engineering; it deals with conception,
design, development, refinement and applications of machines and mechanical apparatus of all
kinds. “Mechanical design” means the design of systems of a mechanical nature – machines,
products, structures, devices and instruments. Mechanical design utilizes mathematics, material
sciences and engineering mechanics.
Characteristics of a Good Designer
(a) A good background in strength of materials, so that the stress analyses are sound.
(b) A good acquaintance with the properties of materials used in machines.
(c) A familiarity with the major characteristics and economics of various manufacturing
processes.
(d) A preparation for deciding wisely.
(e) Ability to deal with basic problems of disciplines outside his specialty.
(f) Thorough knowledge of use of computers.
(g) Some aesthetics sense, because the product must have “customer appeal” if it is to sell.
(h) Knowledge of manufacturing methods.
(i) Knowledge of economics and comparative costs, because the best reason for the existence
of designers/engineers is that they save money for stakeholders.
(j) Inventiveness and creative instinct, most important for maximum effectiveness.
(k) Communication skills.
Other important considerations are to answer some questions like: Will the machine be safe? Will
the machine be easy to service and repair?

2. DESIGN PROCESS
1. Recognition and identification of Need
Though, not always, design begins when an engineer recognizes a need and decides
to do something about it. Recognizing a need and identifying it, often requires high
creativity because the need is often not obvious.
2. Definition of Problem
Defining the problem means giving a detailed description of the object to be
designed, such as its characteristic specifications, dimensions, its inputs and outputs
and also the limitations on these quantities.
3. Synthesis
Synthesis includes the combination of possible system elements to form a connected
whole system. The term system applies to any collection of inter-related and inter-
acting components that work together in an organized manner to fulfil a specified
task.
The process of producing a system model (model is a representation of a physical
system which can be used to predict the behaviour of the real system) is referred to
as system modelling. The model may be a scaled down physical version of the real
system or a full scale model (called the physical model).
If we can understand the physical principles which govern the behaviour of the
system, it may be possible to set-up mathematical equations to predict the
performance of the real system (the mathematical model) otherwise an
experimental model is made.
4. Analysis and Optimization
One may synthesize several components of the system, analyse and optimize them,
and return to synthesis to see what effect this has on the remaining parts of the
system.
5. Evaluation
Evaluation is a very important phase in the design procedure. It involves series of
tests that the system is made to undergo to evaluate its characteristics. These
include the reliability of the system, its performance when compared to other
similar systems, its easy to maintainability and whether its defective parts can be
easily procured and replaced in case of a breakdown.

3. 6. Presentation
This is the final and most vital phase of design process. Presentation means
communicating the outcome of the evaluation process i.e. the new system evolved,
to the management, by explaining to them ways and means in which this system is
better than the prevailing one and how it satisfies the requirements by giving an
outcome comparable with other similar systems.
DESIGN CONSIDERATION
There are number of characteristics which must be considered in a given design situations:
 Strength
 Reliability
 Thermal properties
 Corrosion
 Wear
 Friction
 Processing
 Utility
 Cost
 Safety
 Weight
 Life
 Noise
 Styling
 Shape
 Size
 Flexibility
 Control
 Stiffness
 Surface finish
 Lubrication
 Maintenance
 Volume
 Liability

4. Reference:
[1] A Textbook of Machine Design by Rajendra Karwa © 2002, Firewall Media.
[2] Design of Machine Elements 2nd Edition by K Ganesh Babu and K Srithar © 2010 by Vijay Nicole
Imprints, Private Limited.