1 Introduction to Projections Four Basic Types Orthographic Projections Axonometric...

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Introduction to ProjectionsFour Basic Types

Orthographic

ProjectionsAxonometric

Oblique

Perspective

Pictorials

Note: An Isometric is special case of an Axonometric

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Introduction to Isometric Projection

• The term Isometric literally means equal measure• All planes are equally or proportionately shortened and tilted• All the major axes (X, Y, Z) are 120 degrees apart

CUBE

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Making an Isometric Sketch

• Defining Axis

30o 30o

60o60o

Isometric Axis

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DepthWidth

Height

Isometric Axis Convention

Making an Isometric Sketch

• Axis Convention

Front view

Choose the longest dimension to be the width (or the depth) for optical

stability

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WidthDepth

Height

Isometric Axis Convention

Making an Isometric Sketch

• Axis Convention

Front view

Choose the longest dimension to be the width or

the depth for optical stability

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Usage of the Grid Paper

Correct orientation Incorrect orientation

Note the alignment of the axes

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The Transformation BetweenThe Isometric Grid & Rectilinear Grid

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Object for Practice

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Blocking in the ObjectBegin with Front Face

Front Face

Height

Width

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Blocking in the ObjectAdd Side Face

Height

Depth

Side Face

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Blocking in the ObjectAdd Top Face

Top Face

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Adding DetailCut Outs – Part 1

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Adding DetailCut Outs – Part 2

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Adding DetailCut Outs – Part 3

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Darken Final LinesPart 4

Note: All visible edges will be darkened

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Sketching a Circle1. Draw a square whose

sides are the diameter of the circle.

2. At the center of each side define the point of tangency for the circle.

3. Draw the diagonals of

the square. 4. Orient the paper so you

can draw equal arcs to construct the circle

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Isometric ellipses

• In an isometric drawing, the object is viewed at an angle, which makes circles appear as ellipses.

• Holes

• Cylinders

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Ellipses Can be in Any of Three Planes

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Sketching an Isometric of a Hollow Pipe

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Step 1 - Creating the Base Box

Diameter

Diameter

Length

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Step 2 – Ellipse on Front Face(Reference Technical Graphics, Section 4.2.7)

Lines to Tangent Points

- Lines to tangent points- Corner to corner to get center

Tangent Points

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Step 3 – Ellipse on Front Face

Tangent Points

Sketch in Arcs

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Step 3 – Ellipse on Back Face and Profile

Draw Tangent Lines for ProfileComplete Visible Part of Back Ellipse

Repeat for ellipse on rear face

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Step 4 – Ellipse for Hole on Front Face

Create Box for Hole

Sketch Ellipse

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Isometric of Hollow Pipe

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• Title Information is required. Avoid labels on the sketch.

• Title block on bottom with your name

• Leave the construction lines – MUCH lighter and thinner than the finished lines

• Include centerlines on isometrics

Tips for Drawing Assignments

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• Do not try to shade drawing – this is not a pencil sketching class.

• Use grid paper. Try to sketch along grid lines. Practice sketching straight lines and curves on a grid sheet.

Tips for Drawing Assignments

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Tips for Pictorial Views• In pictorial views, hidden lines are not

shown unless absolutely required for clarity• Non-visible bottom of a blind hole• Important feature of object not in direct view

• In pictorial views, holes or notches without bottom/end visible should be assumed to go completely through the object.

• Centerlines are to be shown on all isometric pictorials.