Manual Dwg Lecture Notes Ch6 - Copy

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Isometric ProjectionDrawing

GROUP V


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MEMB113 | MANUAL DRAWING | CHAPTER 6

GROUP MEMBERS

Sebastian Bubiru Kevin Kiplangat

Bruno Kisia Emanuel Ogada Dennis Mworia Peter Wanyoike

Gilbert Kamau Samuel Gateru

David Chipinde Ivy Wairimu Josphat Gacheru Abdirahman Abdi

Steve Omondy Esther Macharia

Samuel Maina Eunice Wahome


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Content

Overview

Pictorial projection Parallel projection

projection

Principles of isometric projection

Axes and selection

Isometric lines and planes

Isometric scale

Isometric projection & Isometric drawing

Producing Isometric sketches & drawing

Isometric lines & non-isometric lines

Circles and arcs

Irregular curves


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Axonometric projection

Axonometric projection

Trimetric Dimetric

Isometric


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Principle of Isometric Projections

It is a pictorial orthographic projection ofan object in which a transparent cubecontaining the object is tilted until one ofthe solid diagonals of the cube becomes

perpendicular to the vertical plane and thethree axes are equally inclined to thisvertical plane


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Important Terms


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Lines in Isometric Projection

The following are the relations between the lines in

isometric projection;

The lines that are parallel on the object are parallel inthe isometric projection.

Vertical lines on the object appear vertical in the

isometric projection. Horizontal lines on the object are drawn at an angle of

3 0with the horizontal in the isometric projection.

A line parallel to an isometric axis is called anisometric line and it is fore-shortened to 82%.

A line which is not parallel to any isometric axis iscalled non-isometric line and the extent of Fore-shortening of non-isometric lines are different if theirinclinations with the vertical planes are different.


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Isometric projection

Isometric projection is a true representation of theisometric view of an object

Isometric view is created by rotating the object 45degree about vertical axis, and tilting it forward 35deg 16


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Isometric projection: axes

The 3 axis meet at A,B form equal angles of

120 deg and they are called Isometric Axes OA is vertical, OB is inclined at 30deg to

the right, OC is inclined at 30deg to the left

Any lines parallel to theseIsometric Line

Any planes parallelIsometric Planes


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Selection of Isometric Axes Main purpose of isometric view is to provide a pictorial view

which reveals as much detail as possible

Selection of principal edges is important

Figure shows different isometric views of the same block


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Isometric projection: scale

The tilt causes the edges & planes to

become foreshortened The projected length is approximately 80%

of the true length



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Isometric projection & drawing

Isometric projection & Isometric drawing

Isometric projection: drawn at scale of 0.816 Isometric drawing: drawn at full scale



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Methods of Constructing IsometricDrawing

Box method.

Off-set method.


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Off-set Method

Off-set method of making an isometric

drawing is preferred when the objectcontains irregular curved surfaces. In theoff-set method, the curved feature may beobtained by plotting the points on the

curve, located by the measurements alongIsometric lines. The figure in the next slideillustrates.



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Draw the isometric projection of a rectangle of

100mm and 70mm sides if its plane is (a) Verticaland (b) Horizontal.

To draw the isometric projection of a square plane

Construction

Case

Vertical plane

Draw a line at 30to the horizontal and mark the isometric

length on it.

Draw verticals at the ends of the line and mark the isometriclength on these parallel lines.

Join the ends by a straight line which is also inclined at 30tothe horizontal.

There are two possible positions for the plane.

Isometric Projection of Planes



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Case

Horizontal plane Draw two lines at 30to the horizontal and mark

the isometric length along the line.

Complete the figure by drawing 30inclined lines

at the ends till the lines intersect.Note

(i) The shape of the isometric projection ordrawing of a square is a Rhombus.

(ii) While dimensioning an isometric projection orisometric drawing true dimensional values onlymust be used.



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The figure below shows how the cases canbe executed;


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Non-isometric lines

Non-isometric lines are the lines that are not parallel to any

of the iso-lines.

They are drawn by transferring the distance of X or Y frommulti-view to iso-view, not the actual length itself.

L is orthogonalnot equal to Lin isometric



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Isometric angles & non-iso lines

Example of producingnon-isometric lines.

The position of point Z isobtained in the isometricview, by transferring the

distance of X and Y.



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Iso-circles and arcs: draw

Drawing isometric circles and arcs using

four-centre method



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Iso-circles and arcs: draw

Drawing isometric circles using ordinate

method.



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Drawing iso-circles

To draw an iso-circle,on left plane, Diameter

20mm

(a) Draw centre lines,vertical & 30deg to left.

(b) Draw (construction line)20mm square box.The centre lines shoulddivide each side by half.

(c) Draw straight lines; 1-2 & 1-3 and 2-5 & 2-6.(d) Point 7 is the intersection between line 1-2 & 2-5, and similarly point 8, 1-3 & 2-6 on

the other side.(e) Set your compass to the distance 7-2, draw an arc with centre at point 7, from point 2

to point 5. Do the same on the other side.

(f) Set your compass to the distance 1-2, draw an arc with centre (1), from (2) to (3).

(a)

12

3

4

5

6

7

8

2

5

4

5

6

(b) (c)

(d)(e) (f)



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Irregular curves in isometric Irregular curves in

isometric are

produced bytransferring thecoordinates fromorthogonal view.

A fixed distance is set,

A, and the distance inB direction areobtained.

These values are thentransferred to the

isometric view.



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Producing Isometric Sketches

Isometric drawing starts with isometric

sketches. Begin with defining isometric axis.

Begin sketch by extending axesverticallines, 30deg left & right.



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Producing Isometric Sketches

Sketch an isometric box.

Sketch the view on each faces, startingwith isometric lines.

Add in non-iso lines and other details

Darken all visible lines.



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Iso-circles and arcs: sketch

Sketching iso-circle is simpler than drawing.

Create isometric square, each side=diameter.

Find the centre point and midpoints of each side.

Use the construction lines and point to sketch each quarter of thecircle.



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Sketching isometric cylinder Start by drawing the bounding box.

The front end of the cylinder is sketched using the previous

technique. The far end of the cylinder is a partial iso-circle. Sketch until

meeting the tangent with the two straight lines.



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Producing Isometric drawing

Read the orthogonal drawing carefully,

observe the scale, choose the best point where isometric axes

meet to reveal as much detail as possible

draw an 'isometric box' enclosing the object

draw in light construction lines draw arc & curves in thick, remove excess..

line in 30

right lines

line in 30

left lines

line in vertical lines to complete the view



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Examples of isometric drawings ofdifferent shapes



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Producing Isometric drawing Read multi-view dwg

given.

Observe scale,dimension, proj. angle

Determine front, side &top view.

Try to visualise how the

object looks like.

Start with sketching, donot draw straight away.

If not sure, start withsketching an isometricbox, enclosing thewhole object.

You can label points,lines and surfaces onmulti-view to help

visualisation.


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Isometric assembly: 3D render


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The EndTHANK YOU

Manual Dwg Lecture Notes Ch6 - Copy

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