Design and Manufacturing - Study Notes

Chapter 3



3.1. Introduction

Developing a manufacturable product is not an easy job. This chapter presents some methods that help achieve quality products. Rather than making a detailed study, only an overview of designing process is attempted here.

3.2. Features of design process

The following features can be observed in a design process.

•  Iteration

•  Decision-making

•  Conversion of resources

•  Satisfaction of need

Design is completed in many phases. In each phase, repeated attempts are required to accomplish the aim. A satisfactory conclusion can be reached on, only after a number of trials.

Decision-making is essential for a designer to select one out of several. A designer often comes across several equally acceptable alternatives to meet some end. In such conflicting situations, designer has to make the best decision.

In any design process, there is conversion of resources such as time, money, talent, materials and other natural resources.

All designs are aimed at satisfying some human need. Needs, whether important or unimportant is the starting point of design.

3.3. How a design is born?

In a broad sense there are two methods by which a design comes into existence.

•  Design by evolution (Traditional Design)

•  Design by innovation (Modern Design)

•  Design by evolution

This implies the traditional method of design in which the objects and articles that we see around has taken its present form by gradual change of time. If one looks at history it can be seen that most of the tools, equipments, implements, took a long time to acquire their present form. Things changed gradually with the passage of time. Each change was made to rectify some defects or difficulties faced by the users. Bicycles, calculators, computers, steam locomotives etc. all went through a process of evolution in which designers tried one concept after another. Even today this process is being used to some extent. However, this evolutionary process is very slow. i.e., it took a very long period of time to occur even a slight modification. The main reason for this slow evolutionary process of design was the absence of proper information and design data records.

In modern design situations the evolutionary methods are not adequate because of the following reasons.

1. The traditional designing did not consider the interdependence of products. They were concerned about only one component /product. But in the modern world, the existence of one product is dependent on another in some way or other.

2. In the past, production was on small scale. Thus the penalty of a wrong design was tolerable. But, in the present time, production is on large-scale basis. As a result, any penalty of a wrong design will cost great loss.

3. Requirements of the customers of today's world changes so frequently. Traditional design lags behind the advanced product & process technologies available today.

5. Traditional design methods cannot cope with competitive requirements of the modern world.

Due to the above reasons modern design problem cannot be handled by traditional methods.

•  Design by Innovation

Since the traditional design method failed to cope with modern design requirements, nowadays almost all designs are made by innovation. i.e., developments of a product by following scientific and purposeful effort.

The innovative design is entirely different from the past practice of evolutionary design. Here the designer's task is greatly magnified. He has to design and create something, which did not exist yet. Here he tries to solve the design problem in a systematic and orderly manner. This approach is similar to analytical problem solving.

However, an innovative designer faces the following difficulties.

1. He has to collect and evaluate information on a product, which is non-existing yet.

2. Necessity of analyzing complicated interaction of components.

3. He has to make predictions regarding its performance.

4. He has to ensure the technical and economical feasibility of the product.

Notwithstanding the above difficulties, there are eminent experts like Morris Asimow, J.E. Shigly, Dieter etc have attempted to systematize the design process. This systematized steps in design process is called Morphology of Design . The best way in which any problem can be solved is to break up the problem and to try for a solution in an analytical method. This approach of problem solving is also adopted in the Morphology of design.

3.4. Problem-solving Methodology

Knowingly or unknowingly we follow six basic actions when we try to find solution of any problem.

1. Establish or convince ourselves that there is' a problem. Or we understand that a solution is needed.

2. Plan how to solve this problem

3. By analyzing the problem we decide what is actually required from the problem-solver. Or we decide the requirements.

4. Generate alternative solutions.

5. Evaluate the alternatives.

6. Present the acceptable solution.

3.5. Morphology of Design.

Morphology means a study of form or structure'. Morphology of design refers to the time based sequencing of design operations. It is a methodology of design by which ideas about things are converted into physical objects. The logical order of different activities or phases in a design project is called the morphology of design.

3.6. Design Process- Simplified Approach

A simplified approach to designing as outlined by Morris Asimow is given below. According to him the entire design process in its basic forms consists of five basic elements as given below.







Design operations imply the various processes done during designing. These


•  Searching for possible alternatives systems to satisfy a need.

•  Formulating a model for analysis purpose.

•  Materials selection, etc.

But in order to carryout the above processes (i.e., design operations) a lot of information is required. The required informations may be broadly classified into two.

1. General Information

E.g. Scientific Laws

Information on market trends etc.

2 . Specific information .

E.g. Information on manufacturer's catalogue

Materials science handbook etc.

Once the designer has obtained the necessary information he can start design operations. The design operations give outcome s. The outcome may be in the form of

Computer print outs, or drawings.

Next stage is the evaluation of this outcome. The purpose of evaluation is to decide whether this outcome is able to meet the need. Here a comparison between the capabilities of the outcome and the need is carried out. If the outcome is sufficient to meet the need, the designer goes on to next step, otherwise the design operation is repeated


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