Graphical Communication: Lecture 3

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HEF1000 / HES1300 / DEE1243

Graphical Communications

Lecture 3School of Engineering & Science

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TOPICS

Isometric Drawing Oblique Parallel Drawing

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ISOMETRIC DRAWING

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Pictorial Drawing

A three dimensional pictorial is a drawing that shows an objects three principal planes, much as they would be captured by a camera

Sometimes they are called Technical Illustrations

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Types

ObliquesCavalierCabinet

AxonometricsIsometricsDimetricTrimetric

Perspectives

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Types of Axonometrics

Graphical Communication: Lecture 3

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Foreshortening of Cube Edges

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Concept of Isometric Axes

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Isometrics

Axes equally separated (120)

H, W, and D measurements are true size along iso. axes

Angles must be located by coordinates

Circles appear as ellipses on all surfaces

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Isometric Scale

Is used for correct isometric projection.

Allows for the foreshortening of isometric lines.

Is a true representation of the object.

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Isometric Projection vs. Drawing

Isometric projections are foreshortened because the object is tiIsometric projections are foreshortened because the object is tipped pped with respect to the viewing plane. Isometric drawings are not uswith respect to the viewing plane. Isometric drawings are not usually ually foreshortened because they still appear proportionate when showiforeshortened because they still appear proportionate when showing ng the dimensions full size along isometric axis lines. It is easiethe dimensions full size along isometric axis lines. It is easier just to r just to sketch or draw the full dimensionsketch or draw the full dimension.

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Angle for Drawing Isometrics

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Selection of Isometric Axes

Select the view that reveals as much detail as possible.

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Selection of Isometric Axes

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Isometrics Drawing using the Boxing-In Method

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Making an isometric drawing

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Making an isometric drawing

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Inclined Surfaces in Isometric

Inclined surfaces can not be measured along inclined Inclined surfaces can not be measured along inclined lines in an isometric sketch. To locate inclined lines in an isometric sketch. To locate inclined surfaces you must make measurements along the surfaces you must make measurements along the isometric axis lines.isometric axis lines.

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Arcs in Isometric SketchesArcs are usually sketched by locating their centers and Arcs are usually sketched by locating their centers and then boxing in the enclosing parallelogram. Sketch the then boxing in the enclosing parallelogram. Sketch the arc tangent to the enclosing box, which is drawn along arc tangent to the enclosing box, which is drawn along isometric lines.isometric lines.

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Hidden Lines Hidden lines are not Hidden lines are not

usually shown unless usually shown unless they are needed to show they are needed to show an unclear feature.an unclear feature.

The orientation should be The orientation should be chosen so that hidden chosen so that hidden lines arenlines arent needed.t needed.

Holes are assumed to go Holes are assumed to go completely through the completely through the object unless their depth object unless their depth is indicated with a note or is indicated with a note or with hidden lines.with hidden lines.

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Isometric Circles & Angles

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Isometric circlesordinate method

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Isometric Ellipses

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The Isometric Ellipse Template

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Using the Ellipse Template

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Drawing Rounded Corners

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Isometric Ellipse

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1

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Lightly block in the cylinder

Construction of Cylinders

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Construction of Cylinders

Lightly block in the cylinder

Sketch the upper and lower ellipses

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Construction of Cylinders

Lightly block in the cylinder

Sketch the upper and lower ellipses

Connect the ellipses with Tangent lines

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Construction of Cylinders

Lightly block in the cylinder

Sketch the upper and lower ellipses

Connect the ellipses with Tangent lines

Darken the lines

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Oblique Parallel Drawing

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Which is the cube ?

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Were you right?

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Oblique Drawings

Treated the most descriptive or natural view as the front view, and is placed parallel to the plane of projection.

Favored by the furniture manufacturing and cabinetmaking industry.

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Oblique Parallel Projection

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Oblique Drawing Angles

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Types of Oblique Drawings

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Depth Lines

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Cavalier Oblique

Front view true size Receding Axis Angle

(Normally 30, 45 or 60) is Variable

Depth dimension (receding axis) true size

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Cabinet Oblique

Front view true size Receding Axis Angle

(Normally 30, 45 or 60) is Variable

Depth dimension (receding axis) half size

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Side by Side Comparison

Cavalier Oblique Cabinet Oblique

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Unnatural Appearance of Oblique Drawing

Oblique drawings of objects having a lot of depth Oblique drawings of objects having a lot of depth can appear very unnatural due to the lack of can appear very unnatural due to the lack of foreshortening.foreshortening.

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Oblique Drawing Rules 1

Place the object so that the view with the most detail (arcs, circles or irregular face) is parallel to the picture plane.

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Oblique Drawing Rules 2

Place the object so that the longest dimension runs horizontally across the sheet.

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Oblique Drawing Rules 3

Rule 1 has preference as it is easier to draw the irregular face without distortion.

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Oblique Drawing Rules 4

Aim to show the object so that its shape is most clearly presented and is conducive to showing its dimensions.

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Angles in Oblique Angles in front view are drawn true size Other angles must be located using

coordinates Appearance of angles may be distorted

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Circles on the Oblique Face

Drawn true size in front view

Drawn as ellipses on receding planes

Layout using a Rhombus

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Circles on the Oblique Face

The circles are plotted in a similar manner to isometric circles, except that measurements along the 45deg axis are taken from the half size quadrant.

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Cylinders in Oblique

Front and Back surfaces are circular

Sides are drawn as lines tangent to the front and back

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Start Oblique Drawing

Select front view Draw normal features true size on front plane Select convenient angle for receding axes (45

or 30) Draw oblique box: receding axes at selected angle apply appropriate foreshortening

Transfer distances from orthogonal axes along receding axes (scale if required)

Box in other normal features applying offset Join ends to locate non-normal features

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Steps of creating oblique drawing

4 x 4 x 4 Cube in Oblique Representation

CABINET CAVALIER GENERAL

DEPTH = 2 SQUARES

DEPTH = 4 SQUARES

DEPTH = 2 DIAGONALS

Scale = ?

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Steps of creating oblique drawing

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Inclined Surfaces in Oblique

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Oblique vs. Isometric

Circular shapes parallel to the view are Circular shapes parallel to the view are shown true shape in oblique drawing, shown true shape in oblique drawing, making them easy to sketch.making them easy to sketch.

Oblique pictorials are not as realistic as Oblique pictorials are not as realistic as isometric views because the depth can isometric views because the depth can appear very distorted. appear very distorted.

Oblique views cannot usually be Oblique views cannot usually be generated directly from a 3D model generated directly from a 3D model using CAD. using CAD.

Oblique is primarily a sketching Oblique is primarily a sketching technique.technique.

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Reading

BOUNDY, A. W. (2002) Engineering Drawing, NSW, Australia, McGraw-Hill. Chapter 5, pages 197 206.

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End of Lecture!

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