**UNIT 2: GRAPHIC REPRESENTATION AND DESIGN**

3º ESO

TEACHER: MOISÉS LLORENTE

3º ESO

TEACHER: MOISÉS LLORENTE

**unit objectives:**

1. Understanding the importance of standarisation.

2. learning how to apply a scale (up and down) to a drawing.

3. representing objects in the dihedral system (views).

4. representing objects in perspective (cavalier and isometric).

5. dimensioning objects following the standars.

6. using 2d and 3d computer drawing tools.

scales

elevations

perspectives

dimensioning

mongge

2d and 3d editors

**standarisation**

tECHNICAL DRAWING MUST BE A UNIVERSAL LANGUAGE.

PEOPLE ANYWHERE IN THE WORLD SHOULD BE ABLE TO INTERPRET OUR DRAWINGS OR SKETCHES, SO WE NEED TO USE COMMON SYMBOLS.

THANKS TO STANDARISATION, OTHER PEOPLE WILL BE ABLE TO BUILD THE OBJECT WE HAVE DESIGNED WITHOUT EXPLANATIONS.

DEFINITION:

STANDARISATION IS THE SET OF STANDARS THAT REGULATES EVERY ELEMENT OF TECHNICAL DRAWING (FORMATS, LETTERING, DIMENSIONING AND SYMBOLS)

THESE STANDARS ARE AGREED BY AGENCIES.

IN SPAIN, THIS AGENCY IS CALLED AENOR (ASOCIACIÓN ESPAÑOLA DE NORMALIZACIÓN)

STANDARD ELEMENTS IN TECHNICAL DRAWING:

USEFUL CONVENTIONS FOR UNDERSTANDIG DRAWINGS BETTER

1. STANDARDISED SCALES

2. STANDARDISED LINES

3. STANDARDISED DIMENSIONING

**1. STANDARDISED SCALES**

**A**

SCALE

IS THE RELATIONSHIP BETWEEN THE SIZE OF THE DRAWING AND THE ACTUAL (REAL) SIZE OF THE OBJECT.

SCALE

IS THE RELATIONSHIP BETWEEN THE SIZE OF THE DRAWING AND THE ACTUAL (REAL) SIZE OF THE OBJECT.

**IT MEANS... "HOW MANY TIMES IS THE DRAWING BIGGER OR SMALLER THAN THE OBJECT IN THE REAL LIFE?"**

SCALE =

DRAWING

REAL LIFE

THERE ARE THREE TYPES OF SCALES:

1. SCALING DOWN:

THE SIZE OF THE DRAWING IS SMALLER THAN THE OBJECT IN REAL LIFE

2. FULL SCALE:

THE SIZE OF THE DRAWING IS EQUAL TO THE OBJECT IN REAL LIFE (1:1).

3. SCALING UP:

THE SIZE OF THE DRAWING IS BIGGER THAN THE OBJECT IN REAL LIFE

SCALLING DOWN

WE SCALE DOWN TO REPRESENT INSTALLATIONS AND MAPS

TYPICAL SCALES TO SCALE DOWN:

INSTALLATIONS:

1:2, 1:5, 1:10, 1:20, 1:50, 1:100, 1:200

TOPOGRAPHY(MAPS):

1:100, 1:200, 1: 1000, 1:5000, 1:10000, 1:50000...

SCALLING UP

WE SCALE UP TO REPRESENT SMALL OBJECTS IN A DRAWING

TYPICAL SCALES WHEN SCALING UP:

2:1, 5:1, 10:1 AND 20:1

example:

calculate the dimensions we have to use to draw a football field (100 x 70 m) if we use a scale of 1:1000

s =

d

r

SCALE =

DRAWING

REAL LIFE

=

1

1000

=

1

1000

d

r

1. calculate the size in the drawing of the long line:

1

1000

=

d

r

1

1000

=

d

100

d = 10 cm

2. calculate the size in the drawing of the short line:

1

1000

=

d

r

1

1000

=

d

70

d = 7 cm

10 cm

7 cm

scale 1:1000

exercise:

using a graph (squared) paper, draw an object following the next instructions...

1. COUNT 6 SQUARES RIGHT AND THREE SQUARES DOWN FROM THE TOP LEFT CORNER OF THE SQUARED PAPER AND DRAW A POINT. PUT YOUR PEN ON THAT POINT.

2. FROM THERE, START DRAWING LINES FOLLOWING THE NEXT INSTRUCTIONS:

- THREE SQUARES RIGHT, THREE DOWN, FOUR RIGHT, TWO DOWN, ONE LEFT, ONE DOWN, SIXT LEFT, ONE UP, ONE LEFT, ONE UP, ONE RIGHT, FOUR UP.

3. SCALE DOWN THE OBJECT USING A 1:2 SCALE.

4. SCALE UP THE OBJECT USING A 2:1 SCALE.

**2. standardised lines**

**these are the most commonly used:**

THICK (HEAVY) LINE: VISIBLE LINES.

THIN (FINE) LINE: DIMENSION LINES AND AXIS.

FINE DASH-DOTTED LINE: CENTRE LINES.

FINE DASHED LINE: HIDDEN LINES.

**3. DIMENSION LINES**

WHEN WE DIMENSION A FIGURE, WE INDICATE ON THE DRAWING THE REAL MEASUREMENTS THAT ARE NEEDED TO DEFINE IT.

dimension line

measurement

auxiliary lines

dimensioning activity

open your book on page 37 and take a look to the dimensioning examples you have on the top part of the page. notice that some of them are not correct.

using squared paper, copy the following figure and dimension it following the rules you read before. ask your teacher if you don't understand any of them. each square is

5 MM

LONG.

you'll get 5 points per each dimension line you draw correctly. but... you'll lose 5 points pear each one you fail.

REPRESENTATING OBJECTS IN THE DIHEDRICAL SYSTEM. VIEWS

VIEWS IN THE DIHEDRICAL SYSTEM ARE

PROJECTIONS

the effect shown in the drawing is similar to the shadows projected into the walls if you illuminate the object with a torch

**views used to represent an object**

front view

left side

view

right side

view

overhead view

example 1

example 2

example 3

exercise to practise: draw the three main views of the following object

**representing objects in perspective**

we use perspective to view an object in three dimensions (3d)

the most common perspectives are:

cavalier perspective

isometric perspective

CAVALIER PERSPECTIVE

ISOMETRIC PERSPECTIVE

CAVALIER

ISOMETRIC

WHICH IS THE MAIN DIFFERENCE BETWEEN CAVALIER AND ISOMETRIC PERSPECTIVE?

**CAVALIER PERSPECTIVE:**

X AND Z AXES ARE DRAWN WITH A 90º ANGLE

Z

X

90º

Y AXIS IS DRAWN AT A 135º FROM THE OTHER TWO.

Y

135º

135º

**ISOMETRIC PERSPECTIVE:**

ALL THE AXIS ARE SEPARATED BY THE SAME ANGLE (120º)

Z

X

Y

120º

120º

120º