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.
a. Design by evolution (Traditional Design)
b. Design by innovation (Modern Design)
a. 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.
4 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.
b. 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 ApproachA 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
Wednesday, April 23, 2008
Tuesday, April 8, 2008
remaining पार्ट ऑफ़ 2
(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
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
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.
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.
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