Design and Manufacturing - Study Notes

Chapter 1

 

DEFINITION OF ENGINEERING DESIGN

 

1.1 Introduction:

The economic future of India depends on our ability to design, make and sell competitive products. Excellent design and effective manufacture are the pre-requisites of a successive industry. There is a general impression that the quality of Indian products can still be improved. The fact that consumers have lost their confidence on Indian-made products cannot be denied. This problem can be solved only by designing and manufacturing better products through improved methodology. Keeping this in view, the subject “Design and manufacturing” purpose to present the methods and procedures of design and manufacture.

Although engineers are not the only people who design things, the professional practice of engineering is largely concerned with design. It is usually said that design is the essence of engineering.

The ability to design is both a science and an art. The science can be learned through procedures developed by eminent scholars. But the art can be learned only by doing design.

•  Types of Products

A product is the tangible end result of a manufacturing process and is meant for satisfying human needs. The product can be classified as follows: -

•  Convenience goods

These are less expensive and are clustered around shops and restaurants. These can be purchased at consumer's convenience.

E.g. Cigarette, Candy, Magazines etc.

2. Shopping goods

These are expensive and people buy it less frequently.

E.g. Jewellary garments etc.

3. Specialty goods

These are purchased, taking extra pain.

E.g. Rare objects like stamps.

4. Industrial goods.

These are items used in the production of other items.

Eg. Raw materials.

Another way of classifying products is into,

(a) Continuous Products, and

(b) Discrete products

The continuous products are those which are produced in a continuous fashion. For example, plates, sheets, tubes and bars etc are produced in very long lengths, and then these are cut into desired lengths.

On the other hand, discrete products are produced one after another, each in separate units.

On the basis of the output product, the Industry is usually named as continuous industry and discrete industry.

1.3 Requirements in a good product

•  Customer Satisfaction

•  Profit

How to achieve customer satisfaction?

-The product should function properly.

-It must have desired accuracy

-It must have desired reliability

-It must be easy to operate

-It must be serviceable

-It must make minimum space utilization

-It must withstand rough handling

-Pleasant appearances.

-Reasonable price.

How can it be profitable?

-It must be easy to manufacture

-The raw material must be cheap and easily available

-The manufacturing process has to the decided on the basis of quantity to be produced

-It must use standard parts

-It must be easy to pack and distribute.

1.4 Definition of Design: (S ‘94)

Designing is such a vast field that it is defined in several ways. Various definitions of designing as pronounced by well-known designers are

“Design is that which defines solutions to problem which have previously been solved in a different way”

Design is the conscious human process of planning physical things that display a new form in response to some pre-determined need”.

“Design is an act of collecting all pertinent information for the production of goods and services to meet some human need”.

The design of any component includes two things,

•  Product design

•  Process design

The product design involves the development of specification for a product that will be functionally sound, good in appearance, and will give satisfactory performance for an adequate life.

The process design involves developing methods of manufacture of the products so that the component can be produced at a reasonably low cost.

1.5 History of Design Process

•  Design by Single Person

•  Over-the-wall design

•  Simultaneous Engineering

•  Concurrent Engineering

•  Integrated design and Manufacture.

In olden times one person could design and manufacture an entire product. Even for a large project such as the design of a ship or a bridge, one person had sufficient knowledge of the Physics, Materials and manufacturing processes to manage all aspects of the design and construction of the project. This period is referred to as the period of design by single person in the history of design.

 

 

 

By the middle of the 20th century products and manufacturing processes became so complex that, one person could not handle all aspects of design and manufacturing. This situation led to over-the-wall design process.

In this method each functional departments were separated from others, as shown by wall. There was only one-way communications between Customer, Marketing, Engg. Design and production department. The customers ‘throw' their needs to marketing department. The marketing department may throw the customer needs to the design department, in many instances, orally. The Engg. Design department may conceive a design and hands it over to the manufacturing sections. The manufacturing department interprets that design and makes the product according to what they think suitable. Unfortunately, often what is manufactured by a company using over-the-wall process is not what the customers had in mind. This is due to lack of interaction between the different departments. Thus, this single direction over-the-wall approach is inefficient and costly and may result in poor quality products.

By the early 1980's the concept of simultaneous engineering emerged. This philosophy emphasized simultaneous development of the manufacturing process- the goal was the simultaneous development of the product and the manufacturing process. This was accomplished by assigning manufacturing representatives to be members of design team, so that they could interact with the design engineers throughout the designs process.

In the 1980's the simultaneous design philosophy was broadened and called concurrent engineering. A short definition of concurrent engineering is the simultaneous progression of all aspects, at all stages of product development, product specification, design, process and equipment etc. In concurrent engineering the primary focus is on the integration of teams of people having a stake in the product, design tools, and techniques and information about the product and the processes used to develop and manufacture it. Tools and techniques connect the teams with the information. Although many of the tools are computer-based, much design work is still done with pencil and paper. In fact, concurrent engineering is 80% company culture and 20% computer support.

With the advent of computer technology, drastic changes have taken place in the field of design and manufacturing. The result was a completely integrated design and manufacturing system. This system makes a good use of technologies such as CAD/CAM, FMS etc. The computer integrated manufacturing systems (CIMS) moves towards the ‘Factory of the future'. CIMS is necessary for better quality, efficiency and productivity.

 

 

 

QUESTIONS

 

 

•  How can you explain the term design? Explain the process of mechanical design. Discuss the role of creativity in the design process (S'94, 8M)

•  The design of product is …..........customer expectations. (S'99, S'94)

•  .…………get first preference in design

Ans. Functional requirements (S'93)

•  Explain the meaning of

•  Conceptual design

•  Functional design

(iii) Production design. Give suitable examples for each. (S'03)

 

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