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Chapter 6

Isometric Projection DrawingDZULKIFLI AWANG, PHD

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 nontechnical 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 drawingInclined 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-circles5 2 16

4 To draw an iso-circle, on left plane, Diameter 20mm

(a) 5 2 5




7 (a) Draw centre lines, vertical & 30deg to left. (b) Draw (construction line) 6 8 4 20mm square box. (e) The centre lines should (d) 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).


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 youre 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 LinesHidden 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 arent 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


Step by Step: Isometric Sketching

Isometric Drawing Exercise

Isometric Drawing ExerciseThe following presentation will demonstrate how to draw isometric objects using the box method.

Isometric Drawing ExerciseWhen drafting objects freehand, care must be taken to draw accurately and neatly. Therefore, all lines should be drawn as a single linedo not shade any line.

Single line

Shaded line

Isometric Drawing ExerciseYou 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 ExerciseTo 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 ExerciseStep 2: Draw a box on your paper, in the same proportions as the box you drew on the object, 1 to 2 times larger than the original box.Proportional box Original 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 u


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