Manufacturing Technology (ME461) Lecture2

8/12/2019 Manufacturing Technology (ME461) Lecture2

1/20

ME-461, Manufacturing

Technology

Instructor: Shantanu Bhattacharya


2/20

Computer aided design

A large no. of factors are responsible for the success

of any engineering organization.

Engineering design of products and processes is one

of the most critical factors for success. Understanding of the design process and the

computer aided design tool CAD is required to realize

a producible product design.

Computer graphics play an important role in the

product development process by generating

presenting and manipulating geometric models.


3/20

Product design process Contemporary design is a highly sophisticated process and it requires the involvement of not

only design engineers but also personnel from the departments of manufacturing, finance,

marketing, and so on.

The primary input to any design process is the recognition of the fact that a need for aproduct or service exists.

The basic steps involved in the design process are (a) Problem identification (b)Preliminary

ideas (c) Refinement process (d) Analysis process (e) Decision process (f) Implementation.

(1)Problem Identification: The key to designing a

successful product lies in properly identifying the need

and the attributes of that need to which the product is

being developed.

Therefore the problem identification process should

involve the collection of field data; conducting field

surveys and experiments; use of intuition, judgment,

and personal observation and physical

measurements.For example: Consider the problem of developing a

line of high quality notebook sized computers that will

eventually beat the competition. There is a need to

identify the characteristics of the product that will be

successful in a highly competitive market.

For example the design product should be light in weight, highly portable, self contained, and sized to fit in abriefcase, have a standard keyboard layout feel, and have a compatible operating system, among many other

features.


4/20

Product Design Steps

(2) Preliminary Ideas:Once the problem domain has been identified, the

second phase is to generate as many ideas as possible. Brainstormingsessions should be used to generate solutions to the present problem that

may revolutionize present methods. For example: in case of notebook

sized computers, consider the possibility of technological choices in very

large scale integrated (VLSI) circuits; materials choices and design

complexities for price competitiveness; and choices for making theproduct reliable, testable and producible.

(3) Refinement Process: During the refinement process, several good ideas

are pursued, using scale drawings to determine their merits in terms of

space requirements, critical measurements, dimensions of structural

members, and interactions of surfaces and planes.(4) Analysis Process: The analysis phase is concerned with the evaluation of

best designs from the point of view of a number of criteria such as cost,

functional requirements, and marketability. Other engineering tools such

as finite element methods and assembly analysis tools should be used to

evaluate alternative designs from the functionality point of view.


5/20

Product Design Steps

(5) Decision Process: Most often a product is ultimately manufactured using a

single design. Therefore there has to be a decision phase of the design

process wherein a design that has all desirable characteristics is selected

with the following attributes:

(a)Manufacturable at minimum cost.

(b)Design with all desirable quality built-in.

(c) Design that can be quickly manufactured to make the product avialable to

the customers faster.

(6) Implementation process: This step is essentially a detailed design phase.

The detailed specifications of materials, dimensions, tolerances, and

surface roughness should be provided. The idea is to make the drawings to

be used directly for developing process plan so that the product can be

manufactured.


6/20

A brief history of CAD

Automotive and aerospace industries have been at the

forefront of development of CAD technology.

Its origin however can be traced back to Ivan Sutherlands

thesis in 1963 describing a system called sketch pad.

The system known as sketch pad is now known as interactive

graphics and was developed under the SAGE (semi automatic

ground environment) project.

It helped change the radar information into computer

integrated pictures and allowed the flexibility of choosing the

information by pointing a light pen at the desired location on

the cathode ray tube display.


7/20

CAD/CAM systems A wide variety of CAD/CAM systems are currently avialable.

Essentially a CAD system comprises of three major components:

Hardware, which includes computer and input/output devices, application

software, and the operating system software.

The operating systems software act as the interface between the

hardware and the CAD application software system.

The classification scheme we use in thissection is based on hardware of the system.

More specifically, we classify systems by the

host computer that drives the system.

Generally, CAD/CAM systems are classifiedinto four types:

1. Mainframe Based systems

2. Minicomputer based systems

3. Workstation based systems

4. Microcomputer based systems


8/20

Mainframe based system When large engineering projects are involved mainframe based systems are

preferred. The organization of such systems are shown below.

Two major computer system environments

in such a system are the user environment

and the system environment.

The user environment includes workstations

and peripherals such as printers andplotters.

The number of workstations is limited by the

capacity of the host computer so as to

permit a system desired system response

time.

The main segments of a workstation areinput and output devices.

Input devices include cursor control devices

for graphic input and a keyboard containing

programmed function keys for text input.

The light pen, joystick, mouse, stylus on a

digital tablet are commonly used forcontrolling the cursor.


9/20

Input output devices


10/20

Introduction to Geometric Transformation

Computer graphics plays an important role inthe product development process by

generating, presenting, and manipulating

geometric models of objects.

During the product development process, for

proper understanding of designs, it is

necessary not only to generate geometric

models of objects but also to perform such

manipulations on these objects as rotation,

translation and scaling.


11/20

Introduction to Geometric transformation

Essentially, computer graphics is concerned with generating,

presenting and manipulating models of an object and itsdifferent views using computer hardware, software and

graphic devices.

Usually the numerical data generated by a computer at very

high speeds is hard to interpret unless one represents thedata in graphic format and it is even better if the graphic can

be manipulated to be viewed from different sides, enlarged or

reduced in size.

Geometric transformation is one of the basic techniques thatis used to accomplish these graphic functions involving scale

change, translation to another location or rotating it by a

certain angle to get a better view of it.


12/20

Geometric Transformation

Two dimensional transformation:


13/20

2-D transformation

Example : In the figure above, suppose the initial coordinates of vertices A,B,C are

(1,3), (4,5), and (5,3.5), respectively. Determine the coordinates of new vertices A, B

and C after translating the triangle by a distance D= [7, -2]T(where T represents

transpose). Verify that the lengths of the edges of the triangle are unchanged.


14/20

2-D transformation

2 D f i


15/20

2-D transformation Scaling

Example: From the figure on the right, show that

the length of the edge AB is equal to three times

that of AB after scaling the object uniformly by

factor 3.


16/20

2-D transformationRotation:

Rotation in 2D space is defined as moving

any point (x,y) of an object to a new position

by rotating it through a given angle about

some reference point. Positive angles are

measured counterclockwise from x to y. The

mathematical expression for the rotating

transformation is not as obvious as the

formulas for translation and scaling


17/20

2-D transformation (Rotation)

Example: Determine the new position of

object A placed on a round holding tableafter the table has been rotated by 35 deg.

Solution:


18/20


19/20

Homogeneous transformation

Although the 2D and 3D transformationspresented in the previous sections have

obvious geometric meaning it is not efficient

or economical to implement them on a

computer.

This is because translation involves the

addition of matrices whereas scaling and

rotation involves multiplication.

It is however possible to implement a scheme

involving only multiplication which would

simplify the transformation process.

H T f ti


20/20

Homogeneous Transformation

Date post:	03-Jun-2018
Category:	Documents
Upload:	jayant-raj-saurav
View:	227 times
Download:	0 times

Manufacturing Technology (ME461) Lecture2

Documents