I.E.S. HENRI MATISSE de Paterna
DEPARTAMENT DE TECNOLOGIA
Technology – 3rd ESO
UNIT 1.- TECNICAL DRAWING:
THE REPRESENTATION OF OBJECTS.
1. SKETCH AND PLAN.
A sketch is a freehand drawing which includes informaton about the object such as dimensions
and materials.
However, to draf a plan you need drawing instruments or computer aid design programs as
LibreCAD.
SKETCH
PLAN
ACTIVITIES
a) Complete with the correct words:
A sketch is a ______________ drawing which includes informaton about the object such as
_____________ and ______________.
To draf a plan you need _______________ ______________or _______________ programs as LibreCAD.
b) Draw a sketch from an object you can fnd in the kitchen.
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I.E.S. HENRI MATISSE de Paterna
DEPARTAMENT DE TECNOLOGIA
Technology – 3rd ESO
2. ORTHOGRAPHIC OR MULTIVIEW DRAWING.
Imagine you have and object placed in a corner among three perpendicular planes. If we look
straight ahead at the object from the three points of view of the fgure we will obtain the three
main views of the object.
•
Front view: the view of the object from the front and it is represented in the vertcal plane.
•
Side view: the view of the object from the lef side and it is represented in the lateral plane.
•
Top view: the view of the object from the top and it is represented in the horizontal plane.
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I.E.S. HENRI MATISSE de Paterna
DEPARTAMENT DE TECNOLOGIA
Technology – 3rd ESO
ACTIVITIES
a) Copy the following table into your exercise book, and fll it in by writng the number that
corresponds to each view from the objects drawn.
b) Draw the three views from the kitchen object sketch you did.
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I.E.S. HENRI MATISSE de Paterna
DEPARTAMENT DE TECNOLOGIA
Technology – 3rd ESO
3. ISOMETRIC AND OBLIQUE DRAWINGS.
Both are a three-dimensional representaton of an object.
In isometric drawings, the two axes are 60⁰ to the vertcal axis, and the measurements are a scale
of those measurements on the actual object.
Oblique drawings are based on a system of three coordinated axes. The X and the Z (length and
height) form a right angle, and the Y(width or depth) axis is at 45⁰ to them.
The dimensions represented in the X and Z axes have their actual value or a scale. In the cabinet
drawing, all the edges parallel to the Y axis are reduce by a half.
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I.E.S. HENRI MATISSE de Paterna
DEPARTAMENT DE TECNOLOGIA
Technology – 3rd ESO
ACTIVITIES
a) Draw the next fgures in your exercise book using cabinet perspectve. Afer that, draw the
three views of each fgure.
b) Draw the next fgures in your exercise book using isometric perspectve. Afer that, draw the
three views of each fgure.
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I.E.S. HENRI MATISSE de Paterna
DEPARTAMENT DE TECNOLOGIA
Technology – 3rd ESO
4. SCALE
Most objects cannot be drawn using their real measurements. Sometmes they are too big and do
not ft in the paper or other tmes they are too small. In these cases, we must use the scale to
reduce or enlarge the object represented.
Scale is the rato between the dimensions in a drawing and the actual measurements of the object
represented.
S=
measurements of the object in the drawing
the object ' s actual measurements
Depending on the rato we fnd three types of scales:
•
Reduced scale. It is used to represent large objects. The measurements in the drawing are less
than the object's actual dimensions. Example: S= 1:2.
•
Actual scale. It is used when the object's dimensions allow its actual measurements to be
represented. It is expressed as S=1:1.
•
Enlarged scale. It is used to represent small objects. The measurements in the drawing are
larger than the object's actual dimensions. Example: S= 2:1.
These are the standard scales most commonly used:
REDUCED SCALES
1:5
1:10
1:20
1:50
ENLARGED SCALES
1:100
1:500
1:1000
2:1
5:1
10:1
20:1
50:1
ACTIVITIES
a) Which kind of scale would you use to draw the next objects: reduced, enlarged or actual scale?
A fat plan, a car, a window, a pushpin, a kitchen table, scissors, your home key, a lighter and a screw.
b) Make a top view drawing of a ruler that is 30 cm long and 4cm wide, at scale 1:2.
c)
Determine the scale that should be used for drawing a soccer pitch measuring 70m x 100m, so that
it fts on a DIN A4 paper sheet.
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I.E.S. HENRI MATISSE de Paterna
DEPARTAMENT DE TECNOLOGIA
Technology – 3rd ESO
5. DIMENSIONING.
Dimensioning an object consists of indicatng all of its actual dimensions so these can be
interpreted.
The purpose of dimensioning is to provide a clear and complete descripton of an object. A
complete set of dimensions will permit only one interpretaton needed to construct the part.
Dimensioning should follow these guidelines:
1.
Accuracy: correct values must be given.
2.
Clearness: dimensions must be placed in appropriate positons.
3.
Completeness: nothing must be lef out, and nothing duplicated.
4.
Readability: the appropriate line quality must be used for legibility.
In order to add dimensioning correctly, we must use a series of standardised elements such as:
The dimension line is a thin line, broken in
the middle to allow the placement of the
dimension value, with arrowheads at each
end.
An arrowhead is approximately 3 mm long
and 1 mm wide. That is, the length is
roughly three tmes the width. An
extension line extends a line on the object
to the dimension line. The frst dimension
line should be approximately 12 mm (0.6
in) from the object. Extension lines begin
1.5 mm from the object and extend 3 mm
from the last dimension line.
A leader is a thin line used to connect a dimension
with a partcular area. May also be used to indicate
a note or comment about a specifc area. When
there is limited space, a heavy black dot may be
substtuted for the arrows.
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I.E.S. HENRI MATISSE de Paterna
DEPARTAMENT DE TECNOLOGIA
Technology – 3rd ESO
The dimensions should be placed on the face that describes the feature most clearly. There are
several standards for dimensioning. The most important ones are listed below.
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I.E.S. HENRI MATISSE de Paterna
DEPARTAMENT DE TECNOLOGIA
Technology – 3rd ESO
ACTIVITIES
a) Write down the four dimensioning elements.
b) What are the errors? What standard should they follow?
Correct
Wrong
Correct
Wrong
FIRST
SECOND
THIRD
FOURTH
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I.E.S. HENRI MATISSE de Paterna
DEPARTAMENT DE TECNOLOGIA
Technology – 3rd ESO
c) Draw at actual scale the three views of the fgure and dimension them correctly.
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