Design and communication graphics ppt

5/21/2018 Design and communication graphics ppt

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DESIGN AND

COMMUNICATION GRAPHIS

DCG S4 ELEC

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DCG-S4ELEC @SOS Technical School by Deny Beny K.

B Y D E N Y B E N Y K .


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DCG Course Outlines

Chapter 1: Basic Technical Graphics

Chapter 2: Projection Systems

Chapter 3: Plane Geometry

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DCG-S4ELEC @SOS Technical School byDeny Beny K.


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What is drawing?

Drawingis the art of representation ofan object by systematic lines on a paper

using appropriate instruments.

Examples: buildings, roads, bridges,

structures, machines, circuit diagrams,computer graphics

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Classification of drawing

Artistic drawing: free hand or modeldrawing

Engineering drawing: Instrumentdrawing

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Drawing Instruments

A drafter: A drafting machine is used by professionaldraftsman to prepare drawings.

A miniature version of drafting machine known asMini Drafter is used to draw horizontal, verticaland inclined lines and also for measuring lines andangles.

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Drawing Instruments: Mini drafter6



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Drawing Instruments: clinograph

Clinograph: Clinograph is an adjustable set squareand is used to draw parallel lines at any inclination.The two sides of clinograph are fixed at 90oand thethird side can be adjusted at any desired angle

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Drawing Instruments: Drawing board

Drawing board: The Drawing Board serves as theworkstation in drawing and is made with a smoothlevel top surface onto which drawing paper is fixedusing clamps, thumbnails (board pins), or usingdrawing tape.

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Drawing Instruments: T-Square

T-Square: It consists of a straight edge or piece anda cross piece or head, also referred to as a stock thatis fixed on to one end of the straight edge.

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Drawing Instruments: Set- Squares

The set-squares are used for drawing straight line except thehorizontal lines which are usually drawn with T-square.

The perpendicular lines or the lines at300, 600and 900to thehorizontal can be drawn by using the set squares.

The perpendicular lines or the lines inclined at 45

0

and 90

0

to the horizontal can be drawn by using the set- squares.

By using two set-squares, angle of 1500, 7500and 1050can bedrawn.

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Drawing Instruments: French curves

French curves: French Curves also referred to asIrregular Curves are used in drawing regular andsmooth curves with varying radius or curvaturethat cannot otherwise be drawn using other

drawing equipment.

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Drawing Instruments: Rubber oreraser

Rubber or eraser: The rubber is used for erasingextra pencil lines.

Erasing shield: Erasing shield is used to protectthe adjacent lines on the drawing when some part of

a line is being erased.

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Drawing Instruments: Instrument box

Instrument box:An Instruments Box containsseveral pairs of compasses and dividers

It contains the following instrument:

Set Square 450450and 300 600

Compass, Divider

Pencil

Rubber

Ruler

Protractor - Semi-circular 1800

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Drawing Instruments: Protractors

Protractors: Protractors are used for measuring orconstructing angle which cannot be obtained by setsquares. Protractor can be flat, circular or semicircular.

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Drawing Instruments: Pencil

Pencil: The pencils are used for preparing thedrawings on the sheets. The accuracy andappearance of drawing depend upon the quality ofthe pencil used. Pencils are of various grades easily

recognized by the letters marked on the pencils.

9H 8H7H 6H 5H 4H 3H 2H H F HB B 2B 3B 4B 5B 6B 7B 8B 9B

Hardest Medium Softest

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DCG-S4ELEC @SOS Technical


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Drawing Instruments: compass

A compass is used for drawing small circles veryaccurately

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Drawing Instruments: Templates


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These are aids used for drawing small features such as circles, arcs,triangular, square and other shapes and symbols used in various scienceand engineering fields


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DRAWING PAPER ORDRAWING SHEET

Drawing paper must (when fixed onto the drawingboard) be aligned such that its top and bottom edgesrun parallel to the straight edge of the T-Square orthe Parallel Straight Edge.

To facilitate the reading and interpretation of thedrawing, it must have margin, title block, parts list,etc


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LAYOUT OF THE DRAWING SHEET


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TYPES OF DRAWING PAPER Formats


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TYPES OF DRAWING PAPER/ SIZES

They are mainly classified as per their sizes from A0to A6.


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Drawing sheet layout

Depending on the shape and size of the object beingrepresented on the drawing, the drawing sheet can

be taken in the Portrait or Landscape position.


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Drawing sheet Title Block

The title block should lie within the drawing space atthe bottom right hand comer of the sheet.

The title block can have a maximum length of 170

mm providing the following information.


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Title Block Information

1. Title of the drawing.

2. Drawing number.

3. Scale.

4. Symbol denoting the method of projection.5. Name of the firm, and

6. Initials of staff who have designed, checked andapproved


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Title Block Information contd


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Title Block Information contd


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Drawing Sheet Layout

General features of a drawing sheet


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Drawing Sheet Layout


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Layout of sheet for class work


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LINES


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What types of lines are shownhere?


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LINES


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Lines


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Lines


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Lettering

Lettering is defined the art of writing the alphabetsA, B, CZ and numbers such as 1, 2, 30 etc,

It is an important part of drawing and is used to

write letters, dimensions, notes and other necessaryinformation required to complete execution ofmachine or structure, etc.


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Feature of lettering

Uniformity

Neatness

Rapidity

All lettering works are done either by freehand ordrawing instruments.


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Height of letters and numerals

The height of letters and numerals recommended fordrawing are

2.5,

3.5,

5,

7,

10,

14

20mm.


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Classification of lettering

Gothic lettering: all the alphabets are of uniformwidth or thickness

Freehand lettering : writing alphabets without the

use of instruments Roman lettering :


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Style of freehand lettering

Vertical or upright freehand lettering

Single stroke vertical freehand lettering

Lower case vertical freehand lettering

Inclined or Italic freehand lettering Single stroke italic freehand

Lower case Italic freehand


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Single stroke gothic lettering- inclined


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Single stroke gothic lettering- vertical


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Spacing of letters

The spacing means the distance which is to be leftbetween the two adjacent letters in all types oflettering

Note: The space between each word should be kept equal to height of

letter

The space between the two lines should be left equal to twicethe height of letter.

The space between the two lines should be kept not less thanhalf or more than one and a half times the height of letter.


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SCALES

The proportion by which we either reduce or increase theactual size of the object on a drawing is known as drawingto scale or simple scale

The scale is actually a measuring stick, graduated withdifferent divisions to represent corresponding actualdistances according to some proportion, thus givingrapidity marking off distance on drawing.

The scales are either flat or triangular and the material usedin their construction may be wood, celluloid, metal, etc.


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Uses of scale

The scales are used to prepare reduced orenlarged size drawings

The scales are used to set off dimensions

The scales are used to measure distancesdirectly.


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Sizes of scale

Full size scale:

Reducing scale:

Enlarging scale:


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Sizes of scale contd

Full size scale

The scale in which the actually measurements of theobject are drawn to the same sizes on the drawing is

known as full size scale.It is written on the stick as under

1:1 drawing made to actual size


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Reducing scale: The scale in which theactual measurements of the object are reducedto some proportion is known as reducing scale.

The standard reducing proportions are: 1:2 Drawing made to one half of the actual size 1:5 drawing made to one fifth of the actual size 1:10 drawing made to one tenth of the actual size 1:20 drawing made to one twentieth of the actual size 1:50 drawing made to one-fiftieth of the actual size 1:100 drawing made to one-hundredth of the actual

size


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Enlarging scale: the scale in which the actualmeasurements of the object are increased in someproportion is known enlarging scale. The standardproportion are:

2:1 drawing made to twice the actual size

5:1 drawing made to five times the actual size

10:1 drawing made to ten times the actual size.


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DIMENSIONNING

To construct an object, its shapes and sizes must beknown.

Drawing must show all the essential details such assizes of the object, distance between surfaces,locations of holes, type of material, number required,etc.

The expression of these information on a drawing by

the use of lines, symbols, figures and notes is knownas dimensioning.


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TYPES OF DIMENSIONING

Size dimensions: The dimensions which indicatevarious sizes of the object such as length, breadth,diameter, etc


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TYPES OF DIMENSIONING contd

Location dimensions: The dimensions whichlocate the position of one feature with respect to theother feature


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Units of dimensioning

Dimension should as far as possible be expressed inone unity only. The recommended unit is millimeter.

Drawing is prepared to scales based on division of10, such as 1 to 2 or 1: 2, 1 to 5 or 1: 5, 1 to 10 or 1: 10.


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Dimensioning

Lettering Proportions


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Lettering practice

Lettering of lower case & capital letters:


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Vertical Lettering


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Inclined lettering


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Spacing


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Pencils

Pencils with leads of different degrees of hardness or gradesare available in the market. The

hardness or softness of the lead is indicated by 3H, 2H, H,HB, B, 2B, 3B, etc. The grade HB

denotes medium hardness of lead used for general purpose.The hardness increases as the value of the numeral beforethe letter H increases. The lead becomes softer, as the valueof the numeral before B increases


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Application of freehand sketching of


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Application of freehand sketching ofcolors using pencils


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Exercises with dimensioning


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Draw this figure with the shown dimensions in mm

Sheet presentation /4 marks

Object drawing & dimensioning /6marks


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PLANE GEOMETRICAL

CONSTRUCTIONS

DCG Term259


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Introduction to geometric construction

This topic is used to learn how to construct

geometrical figures which are used for Engineering

designs and drawings.

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To bisect a straight line

Trace the line AB, straightly

Divide it into two equal parts

Draw a line CD, perpendicular to AB passing in thecenter (E),

Strike the intersecting arcs at C using radius greaterthan one half of AB. A straight line through point C

and D bisects AB.

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Bisect line

AC2/3 of AB What figure is drawn?

A BE

C

D

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To divider a straight line into equal parts

The following procedure illustrates how to divide a line into5 equal parts:

AB is the given line to be divided into 5 equal parts;

Draw a construction line AC at any convenient angle with AB;

On AC mark successively five equal divisions of any convenientangle;

Name the division points as 1,2,3,4 and 5 on AC.

Connect last division point to point B and then from point 2, 3,

4, 5 and 1. Draw line parallel to the B5 to intersect the line ABat point 4, 3, 2 and 1 as shown in fig below. Thus the line ABis divided into five equal parts.

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Contd

Figure

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To divide a straight line into a given


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To divide a straight line into a givennumber of equal parts say 5

1. Draw AC at any angle e to AB. 2. Construct the required number of equal parts of

convenient length on AC like 1,2,3.

3. Join the last point 5 to B 4. Through 4, 3, 2, 1 draw lines parallel to 5B to

intersect AB at 4',3',2' and 1'.

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bi i l


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To bisect a given angle

1. Draw a line AB and AC making the given angle. 2. With centre A and any convenient radius R draw

an arc intersecting the sides at D and E.

3. With centres D and E and radius larger than halfthe chord length DE, draw arcs intersecting at F

4. Join AF,


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To inscribe a square in a given circle

1. With centre 0, draw a circle of diameter D. 2. Through the centre 0, draw two diameters, say AC

and BD at right angle to each other.

3. Join A-B, B-C, C- D, and D-A. ABCD is therequired square.

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To inscribe a regular polygon of any


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g p yg ynumber of sides in a given circle.

1. Draw the given circle with AD as diameter. 2. Divide the diameter AD into N equal parts say 6. 3. With AD as radius and A and D as centres, draw arcs

intersecting each other at G 4. Join G to 2 and extend to intersect the circle at B. 5. Join A-B which is the length of the side of the required

polygon. 6. Set the compass to the length AB and starting from B

mark off on the circumference of the circles, obtaining

the points C, D, etc. The figure obtained by joining the points A,B, C etc., is

the required polygon.

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l f b f id i i l


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Polygon of any number of sides in circle

Construction

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T i ib h i i i l


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To inscribe a hexagon in a given circle.

1. With centre 0 and radius R draw the given circle. 2. Draw any diameter AD to the circle.

3. Using 30 - 60 set-square and through the point Adraw lines A1, A2 at an angle 60

with AD, intersecting the circle at B and F respectively.

4. Using 30 - 60 and through the point D draw lines D1,D2 at an angle 60 with DA, intersecting the circle at Cand E respectively.

By joining A,B,C,D,E,F, and A the required hexagon isobtained.

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) C h b i


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a) Construct hexagon by using a set-square

Construction

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b) C h b i


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b) Construct hexagon by using compass

1. With centre 0 and radius R draw the given circle. 2. Draw any diameter AD to the circle.

3. With centers A and D and radius equal to the

radius of the circle draw arcs intersecting the circlesat B, F, C and E respectively.

4. ABC D E F is the required hexagon.

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To construct a regular figure of given side length


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g g g gand of N sides on a straight line.

1. Draw the given straight line AB.2. At B erect a perpendicular BC equal in length to AB.

3. Join AC and where it cuts the perpendicular bisector of AB,number the point 4.

4. Complete the square ABCD of which AC is the diagonal.S. With radius AB and centre B describe arc AC as shown.

6. Where this arc cuts the vertical centre line number the point 6.

7. This is the centre of a circle inside which a hexagon of side AB can

now be drawn.8. Bisect the distance 4-6 on the vertical centre line.

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C td


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Contd

9. Mark this bisection 5. This is the centre in which a regularpentagon of side AB can now be drawn.

10. On the vertical centre line step off from point 6 a distance equalin length to the distance

5-6. This is the centre of a circle in which a regular heptagon of sideAB can now be drawn.

11. If further distances 5-6 are now stepped off along the verticalcentre line and are numbered consecutively, each will be thecentre of a circle in which a regular polygon can be inscribed with

since of length AB and with a number of sides denoted by thenumber against the centre.

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t ti


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construction75

T i ib q i t i l


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To inscribe a square in a triangle

1. Draw the given triangle ABC.2. From C drop a perpendicular to cut the base AB at D.

3. From C draw CE parallel to AB and equal in length toCD.

4. Draw AE and where it cuts the line CB mark F.

5. From F draw FG parallel to AB.

6. From F draw F J parallel to CD.

7. From G draw GH parallel to CD.8. Join H to 1.

Then HJFG is the required square.

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Constr ction


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Construction77

To draw a tangent to a circle


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To draw a tangent to a circle

(a) At any point P on the circle.1. With O as centre, draw the given circle. P is any

point on the circle at which tangent to be drawn

2. Join O with P and produce it to P so that OP = PP

3. With O and P as centres and a length greater thanOP as radius, draw arcs intersecting

each other at Q.

4. Draw a line through P and Q. This line is therequired tangent that will be perpendicular to OP atP.

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Construction


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Construction79

To draw a tangent to a circle (contd)


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To draw a tangent to a circle (contd)

(b) From any point outside the circle.1. With O as centre, draw the given circle. P is the point

outside the circle from which tangent is to be drawnto the circle

2. Join O with P. With OP as diameter, draw a semi-circle intersecting the given circle at M. Then, theline drawn through P and M is the required tangent.

3. If the semi-circle is drawn on the other side, it willcut the given circle at M. Then the line through Pand M will also be a tangent to the circle from P.

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Construction


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Construction81

Conic Sections


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Conic Sections

Cone is formed when a right angled triangle with anapex and angle is rotated about its altitude as theaxis. The length or height of the cone is equal to thealtitude of the triangle and the radius of the base of

the cone is equal to the base of the triangle. The apexangle of the cone is 2

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Conic Sections contd


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Conic Sections cont d

When a cone is cut by a plane, the curve formedalong the section is known as a conic. For thispurpose, the cone may be cut by different sectionplanes (Fig. b) and the conic sections obtained are

shown in Fig. c, d, and e.

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Circle When a cone is cut by a section plane A-A making an

angle a = 90 with the axis, the section obtained is acircle.

Ellipse

When a cone is cut by a section plane B-B at anangle, a more than half of the apex angle i.e, and

less than 90, the curve of the section is an ellipse.Its size depends on the angle a and the distance ofthe section plane from the apex of the cone.

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Parabola If the angle a is equal to i.e., when the section plane

C-C is parallel to the slant side of the cone. the curveat the section is a parabola. This is not a closed figurelike circle or ellipse. The size of the parabola dependsupon the distance of the section plane from the slantside of the cone.

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Hyperbola If the angle a is less than e (section plane D-D), the

curve at the section is hyperbola. The curve ofintersection is hyperbola, even if a = , provided thesection plane is not passing through the apex of thecone. However if the section plane passes throughthe apex, the section produced is an isoscelestriangle.

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Conic Sections as Loci of a Moving Point


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Conic Sections as Loci of a Moving Point

A conic section may be defined as the locus of a pointmoving in a plane such that the ratio of its distancefrom a fixed point (Focus) and fixed straight line(Directrix) is always a constant.

The ratio is called eccentricity. The line passing through the focus and

perpendicular to the directrix is the axis of the curve.

The point at which the conic section intersects the

axis is called the vertex or apex of the curve. The eccentricity value is less than 1 for ellipse, equal

to I for parabola and greater than 1 for hyperbola

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To draw a parabola with the distance of the focusf h di i


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from the directrix at 50mm89


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ORTHOGRAPHICPROJECTION

90Projections

HOMEWORK ON PROJECTION


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HOMEWORK ON PROJECTION91

Orthographic Projections


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Orthographic Projections

Chapter Contents Introduction

Types of Projections, Method of Obtaining,

Method of Obtaining Top View

First Angle Projection,

Third Angle Projection,

Projection of Points,

Projection of Lines,

Projection of Planes,

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Introduction


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Introduction

Engineering drawing, particularly solid geometry isthe graphic language used in the industry to recordthe ideas and information necessary in the form of

blue prints to make machines, buildings, structures

etc., by engineers and technicians who design,develop, manufacture and market the products.

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Projection


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Projection

As per the optical physics, an object is seen when the lightrays called visual rays coming from the object strike theobserver's eye. The size of the image formed in the retinadepends on the distance of the observer from the object.

If an imaginary transparent plane is introduced such thatthe object is in between the observer and the plane, theimage obtained on the screen is as shown in Fig. below.

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Projection contd


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Projection cont d

This is called perspective view of the object. Here,straight lines (rays) are drawn from various points on thecontour of the object to meet the transparent plane, thusthe object is said to be projected on that plane.

The figure or view formed by joining, in correctsequence, the points at which these lines meet the planeis called theprojectionof the object.

The lines or rays drawn from the object to the plane are

calledprojectors. The transparent plane on which the projections are

drawn is known asplane of projection.

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Types of Projections


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Types of Projections

1. Pictorial projections (i) Perspective projection

(ii) Isometric projection

(iii) Oblique projection

2. Orthographic Projections

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Types of Projections contd


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Types of Projections cont d

Pictorial Projections The Projections in which the description of the object is completely

understood in one view is known as pictorial projection. They havethe advantage of conveying an immediate impression of the generalshape and details of the object, but not its true dimensions or sizes.

Orthographic Projection 'ORTHO' means right angle and orthographic means right angled

drawing. When the projectors are perpendicular to the plane onwhich the projection is obtained, it is known as orthographicprojection.

Reference Plane: In general, two planes are employed for projection and are known as

reference planes or principal planes of projection

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Types of Projections plane contd


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Types of Projections plane cont d

Vertical Plane(VP): The plane which is vertical, also known as frontal plane

since front view is projected on this plane

Horizontal Plane (HP):

The plane which is horizontal but at right angle to theV.P

Auxiliary Plane(AP):

Any other plane, placed at any angles to the principle

planes

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TYPE OF VIEWS


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TYPE OF VIEWS

Front view or elevation Rear view

Top view or plan

Bottom view Right view

Left/side view or Side elevation or profile view

Auxiliary view: The object is projected on anauxiliary plane

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METHOD OF OBTAINING VIEWS


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METHOD OF OBTAINING VIEWS

Glass box method

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METHOD OF OBTAINING VIEWS (contd)


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METHOD OF OBTAINING VIEWS (cont d)

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O O O N NG V WS (co t d)

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( )

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( )

Now imagine that the glass box faces are unfolded

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( )

The following picture shows the Top, the Front and the Right view of the

object

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Quadrants Method Approach


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Q pp

Orthographic projection is also done on theVerticalPlane (VP), the Horizontal Plane (HP)and theProfile Plane (PP) all referred to asprinciple planes,which are defined with reference to the four quadrantsshown in Figure below:

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Quadrants Method Approach of views


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Q pp

The position of the object placed in any one ofthe quadrant is described above

In the first quadrant above H.P and in front of V.P In the second quadrant above H.P and behind of

V.P

In the third quadrant below H.P and behind V.P

In the fourth quadrant below H.P and in front ofV.P

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What is First Angle Projection?


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g j

If you draw its front and left view and present it as inthe figure below then your method of drawing will beFirst Angle Projection.

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S6ELO - Technical Drawing @ SOS

What is third Angle Projection?


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g j

If you draw its front and left view and present it asin the figure below then your method of drawing

will be Third Angle Projection

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1st& 3rdAngle Projection


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g j110


Creating OrthographicProjections


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In creating the orthographic projections, normallyyou will be starting by drawing the Front View anddraw the remaining views ensuring dimensionalconsistency.

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Method of Obtaining Front View


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Imagine an observer looking at the object from aninfinite distance (Fig. below). The rays are parallel toeach other and perpendicular to both the frontsurface of the object and the plane. When theobserver is at a finite distance from the object, therays converge to the eye as in the case of perspectiveprojection. When the observer looks from the frontsurface F or the block, its true shape and size is seen.

When the rays or projectors are extended further

they meet the vertical plane (V.P) located behind theobject. By joining the projectors meeting the plane incorrect sequence the Front view is obtained.

Method of Obtaining Front View


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114

As Front view alone is insufficient for the completedescription of the object, another plane called Horizontalplane (H.P) is assumed such that it is hinged andperpendicular to V.P and the object is in front of the V.Pand above the H.P


Looking from the top, the projection of the top surface isthe Top view (Tv). Both top surface and Top view are of

exactly the same shape and size. Thus, Top view gives theTrue length L and breadth B of the block but not theheight H.



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Four Quadrants


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When the planes of projections are extended beyondtheir line of intersection, they form Four Quadrants.These quadrants are numbered as I, II, III and IV inanticlockwise direction when rotated about reference

line xy

Four Quadrants


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Principles of orthographic projection


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1. View in the direction a = front view

2. View in the direction b = top view

3. View in the direction c = left side view

4. View in the direction d = right side view

5. View in the direction e = bottom view

6. View in the direction f= rear view

Principles of orthographic projection


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1stangle projection


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3rdAngle projection


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Exercises


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Develop the 1stangle accurate dimension projections for

the objects shown in Figures below, with the frontelevation indicated as shown by the thick arrow in eachrespective object. All dimensions are in mm.

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Projection of Points


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Certain number of points form a line; so, a straight line maybe generated by a point moving in space (see c)

Certain number of lines form a plane, so a plane may begenerated by a straight line moving in space (see b)

Certain number of planes form a solid, so a solid may begenerated by a plane moving in space (see a)



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Points in Space A point may lie in space in anyone of the four quadrants. The

positions of a point are:1. First quadrant, when it lies above H.P and in front of V.P.2. Second quadrant, when it lies above HP and behind V.P.

3. Third quadrant, when it lies below H.P and behind V.P.4. Fourth quadrant, when it lies below H.P and in front of V.P.

Knowing the distances of a point from H.P and V.P,projections on H.P and V.P are found by extending the

projections perpendicular to both the planes. Projection onH.P is called Top view and projection on V.P is called Frontview



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Problem1: Point A is 40 mm above HP and 60 mm in front of V.P. Draw its front and topview.

Solution

The pointA lies in the QuadrantI

Notation followed1. Actual points in space are denoted by capital letters A, B, C.

2. Their front views are denoted by their corresponding lower case letters with dashes a1,b1,c1, etc., and their top views by the lower case letters a, b, c etc.3. Projectors are always drawn as continuous thin lines.

Orthographicprojection of apoint in FirstQuadrant



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Problem2:Draw the projections of a pointAlyingon V.P and 70 mm above HP.

Solution



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Prolem3:A Point B is 30 mm above HP and 40mm behind V.P. Draw its projection.

Solution: The point B lies in the II Quadrant



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Problem4:A point C is 40 mm below HP and 30mm behind V.P. Draw its projection

Solution: The point C is in the III Quadrant



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Problem5:A point D is 30 mm below HP and 40mm in front of V.P. Draw its projection.

Solution: The point D is in the IV Quadrant.

Group work


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Draw the orthographic projections of the followingpoints:

a) Point Pis 30 mm. above H.P and 40 mm. in front of V.P

b) Point Qis 25 mm. above H.P and 35 mm. behind V.Pc) Point Ris 32 mm. below H.P and 45 mm behind V.P

d) Point Sis 35 mm. below H.P and 42 mm in front of V.P

e) Point Tis in H.P and 30 mm is behind V.P

f) Point Uis in V.P and 40 mm below H.Pg) PointVis in V.P and 35 mm above H.P

h) PointWis in H.P and 48 mm in front of V.P

Projection of Lines


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The shortest distance between two points is called astraight line.

The projectors of a straight line are drawn thereforeby joining the projections of its end points

The possible projections of straight lines with respect to V.Pand H.P in the first quadrant are as follows:

1. Perpendicular to one plane and parallel to the other.

2. Parallel to both the planes.

3. Parallel to one plane and inclined to the other.

4. Inclined to both the planes.

Line perpendicular to H.P and parallel to V.P


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Note: Only Fig. (c) is drawn on the drawing sheet as a solution.

Line perpendicular to V.P and parallel to H.P.


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Problem:A lineAB50mmlong is perpendicularto V.P and parallel to HP. Its end A is 20 mm in

front of V.P and the line is 40 mm above HP. Drawthe projections of the line.

Solution

Line parallel to both the planes


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Problem:A line CD 30 mm long is parallel to boththe planes. The line is 40 mm above HP and 20 mmin front of V.P. Draw its projection.

Solution

Line parallel to V.P and inclined to HP.


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Problem:A line AB 40 mm long is parallel to v.pand inclined at an angle of 300 to HP. The endAis15 mm above HP and 20 mm in front of v.P. Drawthe projections of the line.

Solution

Projection of Planes


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A plane figure has two dimensions i.e. the length andbreadth. It may be of any shape such as triangular, square,pentagonal, hexagonal, circular etc. The possibleorientations of the planes with respect to the principalplanes H.P and v.p of projection are: Plane parallel to one of the principal planes and perpendicular to the other,

Plane perpendicular to both the principal planes,

Plane inclined to one of the principal planes and perpendicular to the other,

Plane inclined to both the principal planes.

1. Plane parallel to one of the principal planes andperpendicular to the other


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When a plane is parallel to V.P the front view shows the

true shape of the plane. The top view appears as a lineparallel to xy.

Figure a shows the projections of a square plane ABCD, when it is parallel to V.P andperpendicular to H.P.

The distances of one of the edges above H.P and from the V.P are denoted by d1 and d2respectively.

Figure b shows the projections of the plane. Figure c shows the projections of the plane, when its edges are equally inclined to H.P.

1. Plane parallel to one of the principal planes andperpendicular to the other contd


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Figure below shows the projections of acircular plane, parallel to H.P andperpendicular to V.P.

2. Plane perpendicular to both HP and VP


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When a plane is perpendicular to both H.P. and V.P, the projections ofthe plane appear as straight lines. Figure below shows the projectionsof a rectangular plane ABCD, when one of its longer edges is parallel toH.P. Here, the lengths of the front and top views are equal to the truelengths of the edges.

3. Plane inclined to one of the principal planes andperpendicular to the other


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When a plane is inclined to one plane and perpendicular tothe other, the projections are obtained in two stages. Stage 1 Assume the plane is parallel to H.P (lying on H.P) and perpendicular to V.P.

Stage 2 Rotate the plane (front view) till it makes the given angle with H.P.

Plane inclined to both H.P and v.p


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If a plane is inclined to both H.P and V.P, it is said tobe an oblique plane. Projections of oblique planes areobtained in three stages.

Problem :A rectangular plane ABCD inclined to H.P

by an angle e, its shorter edge being parallel to H.P and inclined to v.p by an angle .

Draw its projections.

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