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Isometric Projection Drawing
DZULKIFLI AWANG, PHD
Chapter 6
Content
• 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
3.1 Pictorial 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.
3.1 Parallel projection technique
3.1 Axonometric 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
3.1 Axonometric projection
• Axonometric projection
– Trimetric
– Dimetric
– Isometric
Axonometric Projections
3.1 Axonometric projection
3.2 Isometric 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’
3.2 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 these – Isometric Line
• Any planes parallel – Isometric Planes
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
Isometric projection: scale
• The tilt causes the edges & planes to
become foreshortened
• The projected length is approximately 80% of the true length
Isometric projection & drawing
• Isometric projection & Isometric drawing
– Isometric projection: drawn at scale of 0.816
– Isometric drawing: drawn at full scale
Isometric Projection vs. Sketch
Isometric projections are foreshortened because the object is tipped
with respect to the viewing plane. Isometric sketches are not usually
foreshortened because they still appear proportionate when showing
the dimensions full size along isometric axis lines. It is easier just to
sketch the full dimension.
Iso-lines & Iso-planes: examples
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 from multi-view to iso-view, not the actual length itself.
L is orthogonal not equal to L in isometric
Isometric angles & non-iso lines
• 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.
Inclined Surfaces in Isometric
Inclined surfaces can not be measured along inclined lines in an isometric
sketch. To locate inclined surfaces you must make measurements along the
isometric axis lines.
Producing Isometric drawing-
Inclined Surfaces in Isometric
Circles in Isometric
• Circles appear as ellispses when
drawn in an isometric sketch.
• To sketch an
isometric circle, locate the center and then sketch the box
that would enclose
the circular shape.
Draw the ellispse tangent to the lines
of the box.
Iso-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.
Ellipses can be in any plane
Producing 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.
Iso-circles and arcs:
• Drawing isometric circles and arcs using
four-centre method
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 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)
1 2
3
4
5
6
7
8
2
5
4
5
6
(b) (c)
(d) (e) (f)
Iso-circles and arcs:
• Drawing isometric circles using ordinate
method.
Drawing isometric circles using ordinate method.
Arcs in Isometric Sketches
Arcs are usually
sketched by
locating their
centers and
then boxing in the enclosing
parallelogram.
Sketch the arc
tangent to the
enclosing box, which is drawn
along isometric
lines.
3.3 Irregular 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.
3.4 Producing Isometric Drawing
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
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, 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.
Producing Isometric drawing
• 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.
Isometric dimensions
• Although isometric drawing is not intended
to transmit dimension, sometimes
dimensions are placed to indicate the size.
• Two types:
Hidden Lines Hidden lines are not usually
shown in isometric sketches
unless they are needed to
show a feature that would be
unclear.
Usually the orientation for
the isometric drawing should be chosen so that hidden
lines aren’t needed.
Holes are assumed to go
completely through the
object unless their depth is
indicated with a note or with
hidden lines.
Isometric features
• Common feature shown in isometric drawing.
Screw thread (external)
Fillet and rounds
Isometric section view
Isometric assembly: 3D render
Isometric exploded assembly
3.5 Oblique projection drawing
• Oblique
projection –
parallel
projection where the projectors
are parallel to
each other but not
perpendicular to the projection
plane
Oblique projection drawing
• The actual angle that the projectors make
with the plane is not fixed, but preferably
between 30deg – 60deg
• Most common 45 degree
Oblique projection drawing
• 3 types:
– Cavalier projection: true length along axis
– Cabinet projection: half true length
– General: any from half to full true length
Oblique projection drawing
• Place complex
surfaces (arcs,
holes, irregular
curve, etc.) parallel to front
plane
• The longest
dimension should be parallel to frontal plane
Producing oblique sketch
• First, sketch the front face.
• Project 45 deg line to the back.
• For holes, determine the visibility.
• Line in all object lines.
End of Topic 3 ISOMETRIC
THANK YOU
Step by Step: Isometric Sketching
Isometric Drawing Exercise
Isometric Drawing Exercise
The following presentation will
demonstrate how to draw isometric
objects using the “box method”.
Isometric Drawing Exercise
When drafting objects freehand, care must
be taken to draw accurately and neatly.
Therefore, all lines should be drawn as a
single line—do not shade any line.
Single line Shaded line
Isometric Drawing Exercise
You will use two different lines to sketch objects:
Construction lines are light lines sketched in as you initially draw the object.
Drawing lines are dark lines which may be used for the initial drawing or which may be created by neatly darkening a construction line.
Isometric Drawing Exercise
To draw an isometric
object using the
box method,
perform the
following steps:
Step 1: Draw a box
around the object
you wish to draw.
Isometric Drawing Exercise
Step 2: Draw a box on your paper, in the
same proportions as the box you drew on
the object, 1½ to 2 times larger than
the original box.
Original box
Proportional box
Isometric Drawing Exercise
Step 3: Look at the front side of the object. Which surface touches the outside of the box?
Step 4: Draw the surface on your box using drawing lines.
Isometric Drawing Exercise
Step 5: Look at the top of the object. Which surface touches the outside of the box?
Step 6: Draw the surface on your box using drawing lines.
Isometric Drawing Exercise
Step 7: Look at the right hand side of the object. Which surface touches the outside of the box? Step 8: Draw the surface on your
box using drawing lines.
Isometric Drawing Exercise
Step 9: Complete
the box by drawing
in the “third lines”.
You may wish to
draw construction
lines then neatly
cover the
construction lines
with drawing lines.
Isometric Drawing Exercise
To complete the Isometric Drawing Exercise,
return to the Sketching and Freehand Drawing
Fundamentals page, open up the Isometric
Drawing Exercise page and print a copy of the
exercise. Your task will be to draw nine
isometric objects freehand, using the box
method as demonstrated in this presentation.
Isometric Drawing Exercise
To complete the exercise, you may divide a
piece of plain white paper (8” x 11”) into
four equal quadrants by lightly creasing the
paper in half horizontally and also in half
vertically. Each object can be sketched into
its own quadrant. You will need three pieces
of paper to complete the exercise.
68 Autumn 2008
The Orthographic Views Sketch
69 Autumn 2008
The Isometric Grid
70 Autumn 2008
Box Object
71 Autumn 2008
Choose and Map a Surface
• Identify the Principal
Surface A
A
72 Autumn 2008
Map Another Surface
• Identify the Inclined
Surface B B
73 Autumn 2008
• Identify Principal
Surface C
C
Map Surface
74 Autumn 2008
D
Map Surface
• Identify Oblique
Surface D
75 Autumn 2008
Map Surface
• Identify Principal
Surface
76 Autumn 2008
Map Surface
• Identify Principal
Surface
77 Autumn 2008
Map Surface
• Identify Principal
Surface
78 Autumn 2008
Notch
Q: What kind of surface
has its characteristic
shape in 2 views?
Inclined Surface This surface would show up as an edge in the 3rd view
79 Autumn 2008
Finished Example
Producing Isometric Sketches
• Isometric drawing starts with isometric
sketches.
• Begin with defining isometric axis.
• Begin sketch by extending axes – vertical
lines, 30deg left & right.
6.3 Producing Isometric Sketches
• 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.
6.3 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 the circle.
6.3 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.
Lect 4 P. 85 Autumn Quarter
Sketching an Isometric of a Hollow Pipe
Lect 4 P. 86 Autumn Quarter
Step 1 - Creating the Base Box
Diameter
Diameter Length
Lect 4 P. 87 Autumn Quarter
Step 2 – Ellipse on Front Face
Lines to Tangent Points
- lines to tangent points
- corner to corner to get center
Tangent Points
Lect 4 P. 88 Autumn Quarter
Step 3 – Ellipse on Front Face
Tangent Points
Sketch in Arcs
Lect 4 P. 89 Autumn Quarter
Step 4 – Ellipse on Back Face and Profile
Draw Tangent Lines for Profile
Complete Visible Part of Back Ellipse
Repeat for ellipse on rear face
Lect 4 P. 90 Autumn Quarter
Step 5 – Ellipse for Hole on Front Face
Create Box for Hole
Sketch Ellipse
• THANK YOU FOR YOUR ATTENTION
• ANY QUESTIONS?