adzlyanuar © 2004 isometric projection drawing chapter 6

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Isometric Projection Drawing

CHAPTER 6

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MEMB113 | MANUAL DRAWING | CHAPTER 6MEMB113 | MANUAL DRAWING | CHAPTER 6

ContentContent• Overview

– Pictorial projection– Parallel projection– Axonometric projection

• 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

• Oblique projection drawing

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6.16.1 Pictorial projectionPictorial projection• Pictorial projection:

– Not intended to give exact or true view.

– Not intended to transmit dimensions, although sometimes dimension is useful.

– Useful when the information and instructions to be given to non-technical and untrained people.

– Hidden lines are not shown in isometric drawing.

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6.16.1 Parallel projection Parallel projection techniquetechnique

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6.16.1 Axonometric projectionAxonometric projection• axon = axis; metric = measure, in

Greek• Axonometric projection is a parallel

projection technique to create a pictorial drawing of an object by rotating the object on an axis relative to a projection or picture plane

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6.16.1 Axonometric projectionAxonometric projection• Axonometric projection

– Trimetric– Dimetric– Isometric

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6.16.1 Axonometric projectionAxonometric projection

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6.26.2 Isometric projectionIsometric projection• Isometric projection is a true representation

of the isometric view of an object• Isometric view is created by rotating the

object 45 degree about vertical axis, and tilting it forward 35 deg 16’

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6.26.2 Isometric projection: axesIsometric 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 these – Isometric Line

• Any planes parallel – Isometric Planes

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6.26.2 Selection of Isometric AxesSelection 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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6.26.2 Isometric projection: scaleIsometric 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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6.26.2 Isometric projection & Isometric projection & drawingdrawing

• Isometric projection & Isometric drawing– Isometric projection: drawn at scale of

0.816– Isometric drawing: drawn at full scale

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6.26.2 Iso-lines & Iso-planes: Iso-lines & Iso-planes: examplesexamples

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6.36.3 Non-isometric linesNon-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 from multi-view to iso-view, not the actual length itself.

L

L

L is orthogonal not equal to L in isometric

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6.36.3 Isometric angles & non-iso Isometric angles & non-iso lineslines

• Example of producing non-isometric lines.

• The position of point Z is obtained in the isometric view, by transferring the distance of X and Y.

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6.36.3 Iso-circles and arcsIso-circles and arcs• Isometric circles or iso-circle cannot be

simply drawn using compass.• Any iso-circle may lie on either top

plane, left (front) plane or right (profile) plane.

• Iso-circle looks slightly oval and skewed.

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6.36.3 Iso-circles and arcs: drawIso-circles and arcs: draw• Drawing isometric circles and arcs

using four-centre method

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6.36.3 Producing isometric circleProducing isometric circle– Draw centre lines AOB and COD, O is

centre of circle, AO=OB=CO=OD = radius of circle.

– Draw FCG and EDH parallel to AOB, draw FAE and GBH parallel to COD.

– Draw diagonal FOH, mark points J and K where FJ = HK = radius of circle.

– With centre G and rad. R1 = GA, draw an arc between GJ produced at L and GK produced at M. Similarly with centre E.

– With centres J and K and radius R2 = JL and KM, complete the figure.

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6.36.3 Iso-circles and arcs: drawIso-circles and arcs: draw• Drawing isometric circles using

ordinate method.

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6.36.3 Drawing iso-circlesDrawing 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 should divide 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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6.36.3 Irregular curves in isometricIrregular curves in isometric• Irregular curves in

isometric are produced by transferring the coordinates from orthogonal view.

• A fixed distance is set, A, and the distance in B direction are obtained.

• These values are then transferred to the isometric view.

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6.36.3 Producing Isometric Producing Isometric SketchesSketches

• Isometric drawing starts with isometric sketches.

• Begin with defining isometric axis.• Begin sketch by extending axes –

vertical lines, 30deg left & right.

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6.36.3 Producing Isometric Producing Isometric SketchesSketches

• Sketch an isometric ‘box’.• Sketch the view on each faces,

starting with isometric lines.• Add in non-iso lines and other details• Darken all visible lines.

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6.36.3 Iso-circles and arcs: sketchIso-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 the circle.

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6.36.3 Sketching isometric Sketching isometric cylindercylinder

• 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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6.46.4 Producing Isometric Producing Isometric drawingdrawing– 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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6.46.4 Producing Isometric Producing Isometric drawingdrawing

• 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, do not draw straight away.

• If not sure, start with sketching an isometric box, enclosing the whole object.

• You can label points, lines and surfaces on multi-view to help visualisation.

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• You can start drawing, once you’re able to visualise how the object looks like, or finish sketching.

• Start with drawing construction line – draw the iso-box, and fill up with other lines.

• Line in (darken) arcs & circles.

• Line in iso-lines.• Line in all other

lines.

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6.56.5 Isometric dimensionsIsometric dimensions

• Although isometric drawing is not intended to transmit dimension, sometimes dimensions are placed to indicate the size.

• Two types:

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6.56.5 Isometric featuresIsometric features• Common feature shown in isometric drawing.

Screw thread (external)

Fillet and rounds

Isometric section view

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6.66.6 Oblique projection drawingOblique projection drawing• Oblique

projection – parallel projection where the projectors are parallel to each other but not perpendicular to the projection plane

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6.66.6 Oblique projection drawingOblique projection drawing• The actual angle that the projectors

make with the plane is not fixed, but preferably between 30deg – 60deg

• Most common 45 degree

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6.66.6 Oblique projection drawingOblique projection drawing• 3 types:

– Cavalier projection: true length along axis– Cabinet projection: half true length– General: any from half to full true length

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6.66.6 Oblique projection drawingOblique projection drawing• Place complex

surfaces (arcs, holes, irregular curve, etc.) parallel to front plane

• The longest dimension should be parallel to frontal plane

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6.76.7 Producing oblique sketchProducing oblique sketch

• First, sketch the front face.• Project 45 deg line to the back.• For holes, determine the visibility.• Line in all object lines.

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