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Design and manufacturing study notes

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Study Materials of Design & Manufacturing

Chapter 1

DEFINITION OF ENGINEERING DESIGN

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

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Study Materials of Design & Manufacturing

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.

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Study Materials of Design & Manufacturing

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.

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Study Materials of Design & Manufacturing

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
• Adaptive Design (W 95, 97, 98 ‘00)
• Variant Design (S 97, 99)
• Original Design
• 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.

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Study Materials of Design & Manufacturing

• 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.
• 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.

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Study Materials of Design & Manufacturing

2.2 On the basis of the nature of design problem, design may be classified as
• Selection design
• Configuration design
• Parametric design
• Original design
• Re-design
• 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.

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Study Materials of Design & Manufacturing

• 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.

Keyboard

Main Circuit board

Extension slots



Floppy drive


Power supply



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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Study Materials of Design &Manufacturing.

• 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 m 3 of liquid.
The volume is given by
V = r 2 l
The tank is described by the parameters, radius 'r', and length l .
Given V = 4 m 3 = r 2 l
r 2 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.
• Original Design
As described in an earlier section, an original design in the development of an assembly or component that did not exist before.
• 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.