CAD VS MANUAL APPLICATION

CAD VS MANUAL APPLICATION

One of the
best ways to
communicate
an ideas is
through some
form of picture
or drawing.
Before starting your engineering drawing you should plan how you are
going to make best use of the space. It is important to think about the
number of views your drawing will have and how much space you will use
of the paper.


ISOMETRIC DRAWING

The representation of the object in figure 2 is called an isometric
drawing. In an isometric drawing, the object's vertical lines are drawn
vertically, and the horizontal lines in the width and depth planes are
shown at 30 degrees to the horizontal.


ORTHOGRAPIC PROJECTION

•The aim of an engineering drawing is to convey all the necessary
information of how to make the part to the manufacturing department.
• For most parts, the information cannot be conveyed in a single view.
• Rather than using several sheets of paper with different views of the
part, several views can be combined on a single drawing using one of
the two available projection systems,

- first angle,
- third angle.


FIRST ANGLE PROJECTION
The diagram below demonstrates how the projection systems work

• With first angle projection, the
view you are looking at is projected
through to the other side of the
object.
• If we are drawing the three visible
sides of the object illustrated in first
angle projection, we are drawing
the views projected on the other
side of the object and not three
nearest views.


THIRD ANGLE PROJECTION

• Using third angle projection,
the view you are looking at is
displayed at the same side.
• If we are drawing the three
nearest faces of this object, the
top and the two nearest views
are the ones we would draw with
the top view appearing above
the side view.

DIMENSIONING

• The purpose of dimensioning is to provide a
clear and complete description of an object. A
complete set of dimensions will permit only one
interpretation needed to construct the part.
Dimensioning should follow these guidelines.
– Accuracy: correct values must be given.
– Clearness: dimensions must be placed in appropriate
positions.
– Completeness: nothing must be left out, and nothing
duplicated.
– Readability: the appropriate line quality must be used
for legibility.


DIMENSIONING
• We have "dimensioned" the object in the
isometric drawing.
• As a general guideline to dimensioning, try
to think that you would make an object and
dimension it in the most useful way.
• Put in exactly as many dimensions as are
necessary for the craftsperson to make it
-no more, no less.
• Do not put in redundant dimensions.
• If "tolerances" or accuracy levels have
been included, the redundant dimensions

often lead to conflicts when the tolerance
allowances can be added in different ways.


DIMENSIONING

• Detailed dimensions required for manufacture
are excluded from assembly drawings. But
overall dimensions of the assembled object are
usually indicated.
• If the spatial relationship between parts if
important for the product to function correctly
then these should also be indicated on the
drawing.
• For example indicating the maximum and
minimum clearance between two parts.


Definitions and Dimensions
The dimension line is a thin
line, broken in the middle to
allow the placement of the
dimension value, with
arrowheads at each end.


Where To Put Dimensions

The dimensions should be placed on the face that describes
the feature most clearly.

SECTIONING

• Sections and sectional views are used to show hidden detail more
clearly.
• They are created by using a cutting plane to cut the object.
• A section is a view of no thickness and shows the outline of the object
at the cutting plane.
• Visible outlines beyond the cutting plane are not drawn.
• A sectional view, displays the outline of the cutting plane and all visible
outlines which can be seen beyond the cutting plane.
• The diagram below shows a sectional view, and how a cutting plane
works.


SECTIONING

Cross-Sectional Views

Sectioning Objects with Holes,
Ribs, Etc.

Half-Sections


ASSEMBLY DRAWINGS
• The assembly of these parts is shown
in an assembly drawing also known as
a general arrangement.

• It corresponds closely to what you
actually see when viewing the object
from a particular angle.
Parts list
• Each part is given a unique number,
indicated on the drawing by a circle
with the number in it and a leader line
pointing to the part.
• The leader line terminates in an arrow
if the line touches the edge of the
component, or in a circle if the line
terminates inside the part.


Industrial Scenario
• Global
• World class organisation
• Labour problem
• Dynamic, highly adaptive
• Shorter product life cycle
• Emphasis on quality
• Rapid technology advances


Changing Environment
• CHANGES

•

CORPORATE

STRATEGY

• Business
Patterns
• Technology
• Methods
• Standards
• Data
processing

•
•
•
•
•

Business
Automation
Integration
Information
Resources

ENTERPRISE

COMPETITION
INNOVATION

FAST

COST

QUALITY


Industry Trend for the Product
Development Process
•
•
•
•

Less time to design, develop and prove out
Improved quality
Less costs, waste and warranty returns
One Main Focus:
Get the product released closer to market
demand. Longer to market means less likely
product will meet customer wants.


Comparison of Product Development Cycle
Typical of Automotive Industry

BEFORE
37 – 48 months

NOW
16 – 24 months

What is CAD
• CAD – Computer Aided Design
• CAD now involved concept to production
• A generic term for all aspects of design
using computer software tools
• Usually covers geometry creation,
manipulation and the production of
drawings


CAD – Description
• The use of computer systems to assist in the creation,
modification, analysis or optimisation of a design
• The computer system consists of the hardware and
software to perform the specialised design functions
required by the particular user.
• Hardware – computer, one or more graphics display
terminals, keyboards and other peripheral equipment.
• Software – computer programs to implement computer
graphics on the system plus application programs to
facilitate the engineering functions of the user.


DEVELOPMENT IN CAD
Complexity
Functionality

Internet
Web-enabled
Collaborative

NT, Linux
Solid model
Low-cost
Desktop
Pro-engineer
More functions
Complex 3D
Kernel modeller
AutoCAD
PC CAD
Unix workstation

Mini computer
Turnkey CAD
Drafting

32 bit midi computer
More functionality
Expensive
Solid modelling research

Large computer
Dedicated system
Limited company
Very expensive
R & D at universities

1950

1960

1970

1980

1990

2000