COMPUTER

AIDED

DESIGN

AND

MANUFACTURING

BE, 7th Semester CA

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Computer Aided Design & Manufacturing (CAD/CAM)

Computer-aided design (CAD): CAD is the use of computer programs to

create two- or three-dimensional (2D or 3D) graphical representations of

physical objects. CAD software may be specialized for specific applications.

CAD is widely used for computer animation and special effects in movies,

advertising, and other applications where the graphic design itself is the

finished product. CAD is also used to design physical products in a wide

range of industries, where the software performs calculations for determining

an optimum shape and size for a variety of product and industrial design

applications.

In product and industrial design, CAD is used mainly for the creation

of detailed 3D solid or surface models, or 2D vector-based drawings of

physical components. However, CAD is also used throughout the engineering

process from conceptual design and layout of products, through strength and

dynamic analysis of assemblies, to the definition of manufacturing methods.

This allows an engineer to both interactively and automatically analyze design

variants, to find the optimal design for manufacturing while minimizing the

use of physical prototypes.

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Computer Aided Manufacturing (CAM): CAM is the use of computer

systems to plan, manage and control the operations of manufacturing plant

through either direct or indirect computer interface with the plant’s production

resources. Computer Aided Manufacturing commonly refers to the use of

numerical control (NC) computer software applications to create detailed

instructions (G-code) that drive computer numerical control (CNC) machine

tools for manufacturing parts. Manufacturers in a variety of industries depend

on the capabilities of CAM to produce high-quality parts.

A broader definition of CAM can include the use of computer applications to

define a manufacturing plan for tooling design, computer-aided design (CAD)

model preparation, NC programming, coordinate measuring machine (CMM)

inspection programming, machine tool simulation, or post-processing. The

plan is then executed in a production environment, such as direct numerical

control (DNC), tool management, CNC machining, or CMM execution.

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CAD/CAM (computer-aided design and computer-aided manufacturing)

refers to computer software that is used to both design and manufacture

products.

CAD is the use of computer technology for design and design documentation.

CAD/CAM applications are used to both design a product and program

manufacturing processes, specifically, CNC machining. CAM software uses

the models and assemblies created in CAD software to generate tool paths

that drive the machines that turn the designs into physical parts. CAD/CAM

software is most often used for machining of prototypes and finished parts.

CAD/CAM is key to improve manufacturing productivity and the

best approach for meeting the critical design requirements.

CAD/CAM software provides engineers with the tools needed to

perform their technical jobs efficiently and free them from the tedious and

time-consuming tasks that require little or no technical expertise.

CAD/CAM software speeds the design process, there fore increasing

productivity, innovation and creativity of designers.

CAD/CAM is the only mean to meet the new technological design and

production requirements of increased accuracy and uniformity.

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Computer assistance, while a designer converts his or her ideas and

knowledge, into a mathematical and graphical model represented in a

computer.

CAD/CAM involves all the processes of conceptualizing , designing,

analyzing, prototyping and actual manufacturing with computer’s assistance.

Latest techniques of geometric modeling (Feature base or parametric

modeling) and manufacturing like rapid prototyping (RP) have bridged the

gap between product conceptualization and product realization.

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CAD/CAM FLOW CHART

Fig: Information flow chart in CAD/CAM Application

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PRODUCT CYCLE

For the reader to appreciate the scope of CAD/CAM in the operations of a

manufacturing firm, it is appropriate to examine the various activities and

functions that must be accomplished in the design and manufacture of a

product. We will refer to these activities and functions as the product cycle. A

diagram showing the various steps in the product cycle is presented in Figure.

The cycle is driven by customers and markets which demand the product. It is

realistic to think of these as a large collection of diverse industrial and

consumer markets rather than one monolithic market. Depending on the

particular customer group, there will be differences in the way the product

cycle is activated in some cases, the design functions are performed by the

customer and the product is manufactured by a different firm.

In other cases, design and manufacturing is accomplished by the same firm.

Whatever the case, the product cycle begins with

concept, an idea for a product. This concept is cultivated, refined, analyzed,

improved, and translated into a plan for the product through

the design engineering process.

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Fig: Product cycle (design and manufacturing)

The plan is documented by drafting Ii set of engineering drawings showing

how the product is made and providing a set of specifications indicating how

the product should perform.

Except for engineering changes which typically follow the product

throughout its life cycle, this completes the design activities in above figure.

The next activities involve the manufacture of the product.

Product

Concept

Design

Engineering Drafting

Process

Planning

Production

Scheduling Production

Quality

Control

Customer

& Market

Order New

Equipment

& Tooling

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A process plan is formulated which specifies the sequence of production

operations required to make the product. New equipment and tools must some

times be acquired to produce the new product. Scheduling provides a plan that

commits the company to the manufacture of certain quantities of the product

by certain dates. Once all of these plans are formulated,

the product goes into production, followed by quality testing, and delivery to t

he customer.

The impact of CAD/CAM is manifest in all of the different activities in

the product cycle, as indicated in Figure. Computer-aided design and

automated drafting are utilized in the conceptualization, design and

documentation of the product. Computers are used in process planning and

scheduling to perform these functions more efficiently.

Computers are used in production to monitor and control the

manufacturing operations. In quality control, computers are used to perform

inspections and performance tests on the product and its components.

As illustrated in Figure, CAD/CAM is overlaid on virtually all of the activities

and functions of the product cycle.

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In the design and production operations of a modem manufacturing firm, the

computer has become a pervasive, useful, and indispensable tool. It is

strategically important and competitively imperative that manufacturing firms

and the people who are employed by them understand CAD/CAM

Computer

aided design

Computer automated

drafting &

documentation

Computer aided

process planning

Product

concept

Customer

& Market

Quality

Control

Computer

aided quality

control

Computer controlled

robots, machines, etc.

Computer scheduling,

material requirements

planning, shop floor control

Production Scheduling

Process

planning

Order new

equipment &

tooling

Design

Engineering Drafting

Fig: Product cycle revised with CAD/CAM overlaid

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In order to establish the scope and definition of CAD/CAM in an engineering

environment and identify existing and future related tools, a study of a typical product

cycle is necessary. The following Figure shows a flowchart of such a cycle.

Typical Product Life Cycle

The Manufacturing Process

The Design Process

Synthesis

Analysis The CAD Process

The CAM Process

Design

needs

Design definitions,

specifications, and

requirements

Collecting

relevant design

information and

feasibility study

Design

conceptualization

Design

modeling and

simulation

Design

analysis

Design

optimization

Design

evaluation

Design documentation

and communication

Process

planning

Order

materials

Design and

procurement of

new tools

Production

planning

NC, CNC, DNC

programming

Production Quality

control Packaging

Marketing

Shipping

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14

CAD Tools Required to Support the Design Process

Design phase Required CAD tools

Design conceptualization Geometric modeling techniques; Graphics

aids; manipulations; and visualization

Design modeling and simulation

Same as above; animation; assemblies;

special modeling packages.

Design analysis Analysis packages; customized programs

and packages.

Design optimization Customized applications; structural

optimization.

Design evaluation Dimensioning; tolerances; BOM; NC.

Design communication and

documentation

Drafting and detailing…

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Manufacturing phase Required CAM tools

Process planning CAPP techniques; cost analysis;

material and tooling specification.

Part programming NC programming

Inspection CAQ; and Inspection software

Assembly Robotics simulation and

programming

CAM Tools Required to Support the Design Process

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16

PRODUCT ENGINEERING It is to the process of designing and developing a device, assembly, or system

such that it be produced as an item for sale through some production

manufacturing process. Product engineering usually entails activity dealing

with issues of cost, productivity, quality, performance, reliability,

serviceability and user features. These product characteristics are generally

all sought in the attempt to make the resulting product attractive to its

intended market and a successful contributor to the business of the

organization that intends to offer the product to that market. It includes

design, development and transitioning to manufacturing of the product. The

term encompasses developing the concept of the product and the design and

development of its mechanical, electronics and software components. For

example a product like a digital camera would include defining the feature

set, design of the optics, the mechanical and ergonomic design of the

packaging, developing the electronics that control the various component and

developing the software that allows the user to see the pictures, store it in

memory, download to a computer, etc. After the initial design and

development is done, transitioning the product to manufacture it in volumes

is considered part of product engineering. Product engineering is

an engineering discipline that deals with both design

and manufacturing aspects of a product.

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BENEFITS of CAD/CAM

Benefits of CAD

The benefits of CAD include lower product development costs, increased productivity, improved product quality and faster time-to-market.

• Better visualization of the final product, sub-assemblies and constituent parts in a CAD system speeds the design process.

• CAD software offers greater accuracy, so errors are reduced.

• A CAD system provides easier, more robust documentation of the design, including geometries and dimensions, bills of materials, etc.

• CAD software offers easy re-use of design data and best practices.

CAD

• Greater flexibility.

• Reduced lead times.

• Reduced inventories.

• Increased Productivity.

• Improved customer service.

• Improved quality.

• Improved communications with

suppliers.

CAM

• Better product design.

• Greater manufacturing control.

• Supported integration.

• Reduced costs.

• Increased utilization.

• Reduction of machine tools.

• Less floor space.

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Benefits of CAM

The benefits of CAM include a properly defined manufacturing plan that

delivers expected results in production.

• CAM systems can maximize utilization of a full range of production

equipment, including high speed, 5-axis, multi-function and turning

machines, electrical discharge machining (EDM) and CMM inspection

equipment.

• CAM systems can aid in creating, verifying, and optimizing NC programs

for optimum machining productivity, as well as automate the creation of

shop documentation.

• Advanced CAM systems with product lifecycle management (PLM)

integration can provide manufacturing planning and production personnel

with data and process management to ensure use of correct data and

standard resources.

• CAM and PLM systems can be integrated with DNC systems for delivery

and management of files to CNC machines on the shop floor.

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Need for CAD/CAM

• Design and manufacturing forms the core of engineering.

• To remain competitive in global economy.

• New products with enhanced features at competitive costs.

• Short lead times and short product lives

• Reduction in product life cycle.

• Mass customization –Customer specific changes to satisfy diverse

requirements –High flexibility in the manufacturing system.

• Reduction in manufacturing cost and delivery time.

• Increasing consumer awareness about quality.

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CONCURRENT ENGINEERING

“The simultaneous performance of product design and process design.

Typically, concurrent engineering involves the formation of cross-functional

teams. This allows engineers and managers of different disciplines to work

together simultaneously in developing product and process design.”

“Concurrent engineering methodologies permit the separate tasks of

the product development process to be carried out simultaneously rather than

sequentially. Product design, testing, manufacturing and process planning

through logistics, for example, are done side-by-side and interactively.

Potential problems in fabrication, assembly, support and quality are identified

and resolved early in the design process.”

Basic Goals of Concurrent Engineering (CE) are:-

• Dramatic improvements in time to market and costs

• Improvements to product quality and performance

• Do more with less

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Benefits of Concurrent Engineering

• Reduces time from design concept by 25% or more.

• Reduces Capital investment by 20% or more.

• Continuous improvement of product quality.

• Increases Product Life Cycle Profitability.

• New technique adopted to improve efficiency of product design & reduce product cycle design time.

• Team of people from different function areas.

• Interaction between different departments.

• Use of special methods like DFMA and FMEA.

• Different departments can start their work simultaneously.

• Improve workflow.

• Eliminates conflict and procedures.

• Holistic approach to product development.

• Robust products.

• Reduction in lead time for product development.

• IT tools –CAD systems with solid modeling. capabilities, KBE, RDBMS, PLM, ERP.

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Fig: Concurrent engineering (Simultaneous or parallel) vs Sequential engineering

Fig: No. of Changes for Concurrent & Traditional Engineering

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WINDOW & VIEWPORT

A window defines a rectangular area in world coordinates. You define a

window with a GWINDOW statement. You can define the window to be

larger than, the same size as, or smaller than the actual range of data values,

depending on whether you want to show all of the data or only part of the

data.

A viewport defines in normalized coordinates a rectangular area on

the display device where the image of the data appears. You define a viewport

with the GPORT command. You can have your graph take up the entire

display device or show it in only a portion, say the upper right part.

WINDOW DEFINITION

The window must be defined the feet or meters or miles on in any length

dimension horizontally and vertically. It is more common to define the corners

of the window with reference to some world cordinate origin. These

dimensions will be input into the computer as (x,y) data, and subsequent

manipulations will be supplied to this computer model.

In the general case, with reference to origin O in fig, let as assume

that the window QRST is defined by the following limits in the world

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Coordinates:

𝑊l = 𝑥 − coordinate of left edge of window, TQ

𝑊r = 𝑥 − coordinate of right edge of window, RS

𝑊b = 𝑦 − coordinate of bottom edge of window, QR

𝑊t = 𝑦 −coordinate of top edge of window, ST

Fig: Parameters for (a) Window, (b) Viewport

The coordinates of the bottom left, bottom right, top right and top left corners

of the window, designed Q,R,S and T in fig are

Q(𝑊l, 𝑊𝑏), 𝑅 𝑊r, 𝑊b , 𝑆 𝑊r, 𝑊t , and 𝑇(𝑊l, 𝑊t)

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One way of inputting the window parameters is

SET WINDOW(𝑊l, 𝑊b , 𝑊r , 𝑊t)

This sequence (𝑊l, 𝑊b , 𝑊r , 𝑊t) of the window limits is the more common one

VIEWPORT DEFINITION

This zone may be defined in screen coordinates (s,t) or in plotting (pixel)

coordinates (p,q). More commonly, it is defined in the Normalized

coordinates (u,v) already, ranging from (0,0) at left bottom to (1,1) at top

right.

The advantage of normalized coordinates is the viewing

transformation relationship derived on this basis can be applied to any screen

display aspect ratio (b/h) and any resolution (m by n pixels). Further, with

(u,v) known, we can get the (s,t) and (p,q) coordinates by use of equations.

Let us further assume that the viewport is defined by the following limits in

the normalized coordinates, with reference to origin O’.

Coordinates:

𝑉l = 𝑢 − coordinate of left edge of viewport, HE

𝑉r = 𝑢 − coordinate of right edge of viewport, EF

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𝑉b = 𝑣 − coordinate of bottom edge ofviewport, FG

𝑉t = 𝑣 −coordinate of top edge of viewport, GH

This quantities too are often designated variously. The coordinates of bottom

left , bottom right, top right, and top left corner of the view designated E,F,G

and H in fig are

E(𝑉l, 𝑉𝑏), 𝐹 𝑉r, 𝑉b , 𝐺 𝑉r, 𝑉t , and 𝐻(𝑉l, 𝑉t)

One way inputting the viewport parameters is

SET VIEWPORT(𝑉l, 𝑉b , 𝑉r , 𝑉t)

Again order of input may differ and need to specified.

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Clipping to the world-coordinates window is usually applied to the

objects before they are passed through the window-to-viewport

transformation. For a 2D object, the latter transformation is simply a

combination of translation and scaling, the latter not necessarily uniform.

(a) Window (b) Viewport

A window and a viewport are related by the linear transformation that maps

the window onto the viewport. A line segment in the window is mapped to a

line segment in the viewport such that the relative positions are preserved.

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The window, in effect, defines the portion of the graph that is to be displayed

in world coordinates, and the viewport specifies the area on the device on

which the image is to appear.

In above figure are showing follows:

• World coordinates -- Problem-oriented

• Screen coordinates -- Of device in use.

• Normalized screen coordinates -- (0,0) and (1,1) at opposite corners of the

screen.

• Window -- Visible rectangular region of the world. Boundaries are

specified in world coordinates.

• Viewport - A region, within the screen, that displays a window. Boundaries

are specified in

a. Screen coordinates

b. Normalized screen coordinates (transformations between window

and viewport coordinates are machine-independent)

• A window acts as a clip region only for future insertions.

• A window may have many viewports

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Relation b/w Windows, and Viewports

1. A window defines a rectangular area

in world coordinates.

2. A window can be defined with a

GWINDOW statement.

3. The window can be defined to be

larger than, the same size as or

smaller than the actual range of data

values, depending on whether we

want to show all of the data or only

part of the data.

4. A window is related by the linear

transformation that maps the

window into the viewport.

5. A line segment in the window is

mapped to a line segment in the

viewport such that the relative

positions are preserved.

1. A viewport defines in normalized

coordinates a rectangular area on the

display device where the image of

the data appears.

2. A viewport is defined with the

GPORT command.

3. We can have our graph take up the

entire display device or show it in

only a portion, say the upper right

part.

4. A view port is also related by the

linear transformation that maps the

window into the viewport

5. The ultimate intention of computer

graphics is to represent the image of

any object in the window.

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MODELING COORDINATES

We can construct the shape of individual objects in a scene within separate

coordinate reference frames called modeling (local) coordinates.

WORLD COORDINATES

Once individual object shapes have been specified, we can place the objects

into appropriate positions within the scene using reference frame called world

coordinate.

To be useful, a graphics system needs to be universal in scale: it

needs to be able to represent atoms or galaxies on the same screen and do both

with minimal hassle for the user. This dictates the requirement that the

package should accept arbitrary rectangular coordinates supplied by the user.

The users coordinates, denoted (x,y), will be called World Coordinates

throughout the course. In the user's world, he chooses an origin O, a pair of X

and Y axes centered at O, and a unit of length along these axes, and all

positions are then specified relative to the origin and measured in his length

units along the axes. The length unit could be feet, angstroms or light years.

Note that the World is infinite in extent - there is no largest or smallest

coordinate. This corresponds to our need for example to possibly track

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Fig: Modeling, World. Device & Normalized Coordinates

a space-ship throughout the galaxy, or to represent a black hole collapsing to a

point. Furthermore the coordinates are also continuous

NORMALIZED DEVICE COORDINATES

Finally, the world coordinates description of the scene is transferred to one or

more output-device reference frames for display, called device (screen)

coordinates.

A graphic system first converts world coordinate positions to

normalized device coordinates, in the range 0 to 1.This makes the system

independent of the output-devices.

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HOMOGENEOUS COORDINATES

Homogeneous coordinates.(x,y,w) instead of (x, y)

Points (x, y) in the plane z = w of a 3D space.

Fig: Homogeneous Coordinates

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NORMALIZED HOMOGENEOUS COORDINATES

Normalized device coordinates (NDCs) make up a coordinate system that

describes positions on a virtual plotting device. The lower left corner

corresponds to (0,0), and the upper right corner corresponds to (1,1).

NDCs can be used when you want to position text, lines, markers, or polygons

anywhere on the plotting device (that may or may not already contain a plot).

Fig: Normalized Homogeneous Coordinates

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