Introduction to Projection_Sumedha Premi_SITE Meerut_S4

Session – 4

Session Name: Introduction to Projection

Author Name: Sumedha Premi

Department: Mechanical Engineering

Subject/Course: Engineering Drawing / B. Tech.

Ver 1:.01 Introduction to Projection Sumedha Premi, Subharti Institute of Technology & Engineering, Meerut

Session Objectives At the end of this session, the learner will be able to:

Define Engineering Drawing.

Identify the need for Engineering Drawing.

Discuss the advantages of Engineering Drawing.

State the meaning of projection.

Distinguish between different kinds of projection.

Teaching Learning Material

Board and Markers

Presentation Slides

LCD Projector

Sheets of paper with 2D geometric figures drawn on them

3D models of different shapes, a white drawing sheet and a torch

Introduction to Projection Sumedha Premi Subharti Institute of Technology & Engineering, Meerut

Session Plan

Time (in min)

Content Learning Aid

and Methodology

Faculty Approach

Typical Student Activity

Skill and Competency Developed

10 Introduction to Engineering Drawing

Brainstorming Facilitates Explains

Listens Participates

Understanding Intrapersonal Verbal-Linguistic

15 Why is Engineering Drawing Needed?

Game Conducts Questions Explains

Listens Participates Analyzes

Analyzing Intrapersonal Interpersonal Visual Logical Verbal - Linguistic

10 Advantages of Engineering Drawing

Choose and Defend

Facilitates Participates Discusses Identifies

Understanding Interpersonal Logical Verbal-Linguistic

15 Projection and its Types

Demonstration Visual Aids

Facilitates Instructs Explains

Listens Demonstrates Observes Comprehends

Understanding Intrapersonal Visual-Spatial Verbal-Linguistic

10 Conclusion Questions and Answers

Questions Recalls Answers

Remembering Intrapersonal Verbal


Session Inputs

Introduction to Engineering Drawing

‘Drawing’ being a well-known term, the faculty can begin the

session by conducting a brainstorming activity so as to know what

is the basic understating of learners about the term Engineering

Drawing.

Suggested Activity: Brainstorming

We can conduct the brainstorming activity by posing the question-

What do you understand by Engineering Drawing?

Learners can be given one minute time to respond. They can be asked to

share whatever words come to their mind on hearing the term ‘Engineering

Drawing’. Responses from the learners can be listed on the board by the

facilitator.

Sample responses: Drawing of machines and its parts, architects, geometric

figures, set-squares, compass, instrument box, etc.

At the end of the stipulated time, the learners can be asked to stop. We

can then remove the irrelevant responses after providing appropriate

explanation. From the remaining responses, we can try to frame the

definition of Engineering Drawing.

Engineering Drawing: An Engineering Drawing is a type of drawing

that is technical in nature, used to fully and clearly define the

requirements for engineered items. It is usually created in

accordance with standardized conventions.

The purpose of Engineering Drawing is to accurately and

unambiguously capture all the geometric features of a product or

a component so as to convey all the required information that will

allow a manufacturer to produce that component.


Drawings convey the following critical information:

Geometry – The shape of the object represented as views;

how the object will look when it is viewed from various

angles, such as front, top, side etc.

Dimensions – The size of the object.

Tolerance – The allowable variations for each dimension.

Material – It represents what the item is made of.

Finish – It specifies the surface quality of the item.

Why is Engineering Drawing Needed?

We can now move on to a discussion on perception. Through an

activity, we can set the context for explaining the need for

Engineering Drawing.

Suggested Activity: Game

The purpose of this activity is to help the learners understand the need for

Engineering Drawing.

We can ask one of the learners (say learner X) to come onto the dais. We

can give a piece of drawing / image to learner X. It can be one of the

following :

(A) (B) (C)


Learner X can be given a time-duration of about 1 minute to explain the

image verbally to the class. The other learners seated in the class can be

asked to draw the figure as per the instructions / explanation given by

learner X. At the end of the stipulated time, we can ask learner X to draw

the actual figure on the board and then check how many learners were

able to draw the exact image. There will be many learners who would

have drawn the figure differently.

We can repeat the same procedure two or three times by calling different

learners onto the dais.

We can now ask the learners, what could be the reason for differences in

the figures drawn by learners for the same description given by the learner

on dais. The views of the learners can be noted.

The reason for the differences is perception. Each person perceives the

description differently, thereby coming up with different figures.

We can now explain the need for Engineering Drawing.

Perception: Perception is the process of attaining understanding

of sensory information.

Everyone perceives things differently based on their knowledge. A

person’s knowledge creates his or her reality as much as the truth,

because the human mind can only contemplate that to which it

has been exposed.

If the instructions for manufacturing a product are given orally,

then it involves a risk that the product that is going to be

manufactured may not be the desired one.

We know that a picture is worth a thousand words. What we listen

to, we can interpret differently. But, what we see in drawings

cannot be interpreted differently because every single thing

mentioned in drawings has a specific meaning as the drawings

are made in accordance with standardized conventions. Hence,

Engineering Drawing is very much needed to pass on information

accurately and unambiguously.


Advantages of Engineering Drawing

Having discussed what Engineering Drawing is and why it is

needed, we can now discuss its advantages.

Suggested Activity: Choose and Defend

The learners can be formed into two or three groups based on the number

of rows in the class. Each group can be asked to identify the advantages

of Engineering Drawing. The groups can be given 2 minutes for the

discussion. The facilitator, along with the learners, can evaluate (debate

and defend) the advantages mentioned by each group. For each correct

advantage, 2 points can be given and it can be written on the board.

Advantages of Engineering Drawing:

It is created as per standardized conventions. Hence, it can

be easily used across the globe.

All views of a component, along with the sectional views,

can be looked at in one go.

As most of the specifications are symbolized, a lot of

information can be conveyed through a single drawing.

Projection and its Types

Having discussed the fundamentals, we can now explain what

projection is and discuss the different types of projection.

Suggested Activity: Demonstration

We can explain the principle of projection with the help of the following

image along with 3D models, a torch and a white drawing sheet.

We can ask one learner to hold the sheet vertically and another learner to


hold the model in front of the sheet. A third learner can be asked to switch

on the torch and hold it in such a position that light falls on the front side of

the model (the side that is facing the class). The shadow of the model falls

on the sheet. This can be shown to the learners. This shadow is nothing but

the projection.

The terms related to projection like projectors, projection plane, object etc.

can be explained to the learners by showing the following image using a

PPT.

Projection

Principle of Projection: If straight lines are drawn from various

points on the contour of an object to meet a plane, the object is

said to be projected on the plane. The figure formed by joining, in

correct sequence, the points at which the lines meet the plane, is

called a projection of that object. The lines from the object to the

plane are called projectors and the plane on which the

projectors meet, is known as the plane of projection.


Various types of projections can be explained with the help of

images displayed using a PPT.

Orthographic Projection

(A) Isometric Projection (B) Perspective Projection


Oblique Projection

Types of Projection:

Orthographic Projection

Isometric Projection

Oblique Projection

Perspective Projection

Orthographic Projection: When the projectors are parallel to each

other and also perpendicular to the projection plane, the

projection is called orthographic projection. It shows the object as

it looks from the front, right, left, top, bottom or back and are

typically positioned relative to each other according to the rules

of either first-angle or third-angle projection.

Isometric Projection: Isometric projection is a type of pictorial

projection in which the three dimensions of a solid are not only

shown in one view, but their actual sizes can be measured

directly from it. In such projection, the vertical edges are

represented by vertical lines, while horizontal edges are

represented by lines, making 30˚ angles with horizontal.

Oblique Projection: Oblique projection is a type of pictorial

projection in which a three dimensional object is represented on

the projection plane by one view only. In such type of projection,

the third axis is generally at 30˚ or 45˚ or 60˚ with respect to the

two perpendicular axes.


Perspective Projection: Perspective projection is the

representation of an object on a plane surface, called the picture

plane, as it would appear to the eye, when viewed from a fixed

position.

Conclusion

We can conclude the session by revising the key concepts

discussed during the session through a question and answer

activity.

Suggested Activity: Questions and Answers

The following questions can be asked to ensure that the learners have

gained a good understanding of the concepts discussed so far.

What are the advantages of engineering drawing?

What is the basic principle of projection?

What are projectors?

What is projection plane?

Projection is of how many types?

What are the different types of projection?

What is orthographic projection?

What is isometric projection?

What is oblique projection?

What is perspective projection?


Summary In this session, we learnt to:

Define Engineering Drawing.

Identify the need for Engineering Drawing.

Discuss the advantages of Engineering Drawing.

State the meaning of projection.

Distinguish between different kinds of projection.

o Orthographic Projection

o Isometric Projection

o Oblique Projection

o Perspective Projection


Assignment

1. Identify the different methods used for preparing Engineering

Drawings.

2. Identify the advantages of computerized Engineering Drawing over

manual Engineering Drawing.

3. Find which type of projection is generally used in industry for drawings.

4. Study the different kinds of orthographic projections.


References

Engineering Drawing by N. D. Bhatt

http://en.wikipedia.org

http://google.com

Introduction to Projection_Sumedha Premi_SITE Meerut_S4

Documents

Transcript of Introduction to Projection_Sumedha Premi_SITE Meerut_S4