CHAPTER 2 : TYPES OF DESIGNS

2.1 The design can be classified in many ways. On the basis of knowledge, skill and creativity required in the designing process, the designs are broadly classified into three types
(i) Adaptive Design (W 95, 97, 98 ‘00)
(ii) Variant Design (S 97, 99)
(iii) Original Design

(i) Adaptive Design
In most design situations the designer’s job is to make a slight modification of the existing design। These are called adaptive designs. This type of design needs no special knowledge or skill. E.g. converting mechanical watches into a new shape.

(ii) Variant Design
This type of design demands considerable scientific training and design ability, in order to modify the existing designs into a new idea, by adopting a new material or a different method of manufacture. In this case, though the designer starts from the existing designs, the final product may be entirely different from the original product.
E।g. converting mechanical watches into quartz watches. Here a new technology is adopted.

(iii) Original Design
Here the designer designs something that did not exist previously। Thus, it is also called new design or innovative design. For making original designs, a lot of research work, knowledge and creativity are essential. A company thinks of new design when there is a new technology available or when there is enough market push. Since this type of design demands maximum creativity from the part of the designer, these are also called creative designs.

2.2 On the basis of the nature of design problem, design may be classified as
(a) Selection design
(b) Configuration design
(c) Parametric design
(d) Original design
(e) Re-design

(a) Selection Design.
It involves choosing one or more items from a list of similar items. We do this by using catalogues.
Eg. -Selection of a bearing from a bearing catalogue
-Selection of a fan for cooling equipment
-Selecting a shaft।

(b) Configuration / Layout / Packaging Design (W 97, S'02)
In this type of problem, all the components have been designed and the problem is how to assemble them into the completed product. This type of design is similar to arranging furniture in a living room.
Consider the packing of electronic components in a laptop computer. A laptop computer has a keyboard, power supply, a main circuit board, a hard disk drive, a floppy disk drive and room for two extension boards. Each component is of known design and has certain constraints on its position. For example, the extension slots must be adjacent to the main circuit board and the keyboard must be in front of the machine.

The different components are shown above. The designer’s aim is to find, how to fit all the components in a case? Where do we put what? One method for solving such problems is to – select a component randomly from the list and position it in the case so that all the constraints on that component are met.
Let's take keyboard first. It is placed in the front. Then we select and place a second component. This procedure is continued until we reach a conflict, or all the components are in the case. If a conflict arises, we back up and try again. Two potential configurations are shown above.

(c) Parametric Design
Parametric design involves finding values for the features that characterize the object being studied.
Consider a simple example –
We want to design a cylindrical storage tank that must hold 4 m3 of liquid.
The volume is given by
V = r2 l
The tank is described by the parameters, radius 'r', and length l.
Given V = 4 m3 = r2 l
r2 l = 1.273
We can see a number of values for the radius and length, that will satisfy this equation। Each combination-values of r and l gives a possible solution for the design problem.

(d) Original Design
As described in an earlier section, an original design in the development of an assembly or component that did not exist before।

(e) Redesign
The redesign is a modification of an existing product to meet new requirements। It is same as adaptive design. Most design problems solved in industry are for the redesign of an existing product. Suppose a manufacturer of hydraulic cylinders makes a product that is 0.25m long. If the customer needs a cylinder 0.3m long, the manufacturer might lengthen the outer cylinder and the piston rod to meet this special need.

2.3. On the basis of the objective or strategy the designs are of following main types.
A. Production Design
B. Functional Design
C. Optimum डिजाईन

A. Production Design
In production design, the designer designs something in such a way that the cost of producing the product is minimum। That is, the first responsibility of the designer is reduction of production cost. Hence, a production designer is concerned with the ease with which something can be produced, and that at a minimum cost.

B. Functional Design W93
In functional design, the aim is at designing a part or member so as to meet the expected performance level.
Functional design is a way of achieving given requirements।- but the same may the unproducible or costly to produce. A good designer, then, has to consider the production aspects also. A product designed without keeping all these aspects into account, wastes time, money and efforts.

C। Optimum Design [W 95]
It is the best design for given objective function, under the specified constraints।

2.4 On the basis of the field/ area or the domain of design, the following types are important.
1. Mechanical Design
2. Machine Design
3. System Design
4. Assembly/sub-assembly design
5. Computer aided डिजाईन

1. Mechanical Design
It means use of scientific principles, technical information and imagination in the design of a structure,or machine to perform prescribed functions with maximum economy and efficiency।

2. Machine Design
It is the process of achieving a plan for the construction of a machine।

3. System Design
System Design is an iterative decision making process to conceive and implement optimum systems, to solve problems and needs of society।

4. Assembly/sub-assembly design [S 93]
In the design of Assembly/sub-assembly the major criterion is the fulfillment of functional requirements. The assembly has to be designed to meet broad technical parameters and purpose for which it was meant.
The characteristic features are:
¬ The total number of parts used in the design must be minimum.
¬ Sub-assemblies should be capable of being built separately in order to give maximum manufacturing flexibility.
¬ Standard parts may be used.
¬ Flexible parts should be avoided, as they are easily damaged during handling and assembly।

5. Computer aided design [CAD]
It is a design methodology in which the designs take the advantages of digital computer to draw concepts, analyze and evaluate data etc. Computers are largely used in a design office for simulation and prototype study. In modern design, computers have become an indispensable tool.
Other types of designs are
Probabilistic Design
Industrial Design
Probabilistic Design [S 96]
It is a design approach in which design decisions are made using statistical tools. Generally, the external load acting on a body, the properties of materials etc are liable to vary. In probabilistic design, the designer takes into account the variations of such parameters.
Industrial Design [W 93]It is the design made by considering aesthetes, ergonomics and production aspects