Section 2 Drafting Techniques and Skills Chapter 11 Pictorial Drawings Section 2 Drafting Techniques and Skills

Objectives List the three basic types of pictorial drawings and explain the purpose of each. Explain the principles of axonometric projection. Draw isometric, dimetric, and trimetric views. Draw oblique views. © Goodheart-Willcox Co., Inc.

Objectives Draw one-point and two-point perspective views. Describe how pictorial views are created in CAD drafting. © Goodheart-Willcox Co., Inc.

Pictorial Drawing Often used with or in place of multiview drawing. Commonly made for assemblies and piping designs. Widely used in service manuals and training materials. © Goodheart-Willcox Co., Inc.

Types of Pictorial Projections (American National Standards Institute) © Goodheart-Willcox Co., Inc.

Types of Axonometric Projection Isometric Dimetric Trimetric © Goodheart-Willcox Co., Inc.

Isometric Projection Three faces equally inclined to projection plane. Axis angles equal. © Goodheart-Willcox Co., Inc.

Dimetric Projection Two of three faces equally inclined to projection plane. Two axis angles equal. © Goodheart-Willcox Co., Inc.

Trimetric Projection Three faces inclined differently to projection plane. Axis angles all unequal. © Goodheart-Willcox Co., Inc.

Isometric Projection © Goodheart-Willcox Co., Inc.

Principles of Isometric Projection Isometric axes separated by 120. Object faces make up isometric planes. View made up of isometric lines and nonisometric lines. © Goodheart-Willcox Co., Inc.

Comparing Isometric Projection and Isometric Drawing Isometric drawings more common (easier to make). Isometric drawings made with direct measurements. Lines foreshortened in isometric projection. (American National Standards Institute) © Goodheart-Willcox Co., Inc.

Constructing Isometric Drawings Normal surfaces drawn before inclined surfaces. Lines parallel to horizontal axes drawn at 30. Lines parallel to vertical axis drawn vertical. Hidden lines normally omitted. Same principles apply in manual drafting and CAD. © Goodheart-Willcox Co., Inc.

Isometric Drawing Functions in CAD Isometric snap Isoplanes Isometric grid Isometric viewing tools Modeling commands © Goodheart-Willcox Co., Inc.

Isoplane Orientations © Goodheart-Willcox Co., Inc.

Construct an Isometric Drawing with Normal Surfaces © Goodheart-Willcox Co., Inc.

Construct an Isometric Drawing with Normal Surfaces Activate isometric snap. Use Line command and Ortho to draw outer isometric lines. Draw isometric lines to create cut surface. © Goodheart-Willcox Co., Inc.

Construct an Isometric View with Nonisometric Lines © Goodheart-Willcox Co., Inc.

Construct an Isometric View with Nonisometric Lines Activate isometric snap. Use drawing and editing commands to create isometric lines. Use drawing commands and object snaps to create nonisometric lines. © Goodheart-Willcox Co., Inc.

Construct Angles in an Isometric Drawing © Goodheart-Willcox Co., Inc.

Construct Angles in an Isometric Drawing Activate isometric snap. Use Line command to create isometric lines. Use Copy and Line commands to create angle cuts. © Goodheart-Willcox Co., Inc.

Methods Used to Construct Isometric Circles and Arcs Four-center approximate method Coordinate method Isometric ellipse template Ellipse command © Goodheart-Willcox Co., Inc.

Four-Center Approximate Method © Goodheart-Willcox Co., Inc.

Draw Isometric Circles and Arcs Using the Ellipse Command Activate isometric snap and desired isoplane. Enter Ellipse command and enter Isocircle option. Pick ellipse center and drag to specify radius. © Goodheart-Willcox Co., Inc.

Draw Irregular Curves in Isometric Drawings © Goodheart-Willcox Co., Inc.

Draw Irregular Curves in Isometric Drawings © Goodheart-Willcox Co., Inc.

Constructing Isometric Section Views Cutting plane drawn parallel to isometric axis. Section lines normally drawn at 60. © Goodheart-Willcox Co., Inc.

Draw an Isometric Section View © Goodheart-Willcox Co., Inc.

Draw an Isometric Section View Draw isometric outlines and sectioned faces. Draw isometric circles and arcs. Add hatch lines. Use Section Plane command in 3D applications. © Goodheart-Willcox Co., Inc.

Isometric Dimensioning © Goodheart-Willcox Co., Inc.

Alternate Positioning of Isometric Axes Used to clarify important features. Axes must remain oriented at 120. © Goodheart-Willcox Co., Inc.

Centering an Isometric Drawing Locate object center. Locate center point at center of sheet. Locate start point from center parallel to isometric axes. © Goodheart-Willcox Co., Inc.

Advantages and Disadvantages of Isometric Drawings Same scale used on all three axes. Single view sufficient. Less time required than in other pictorial methods. Disadvantages Potential distortion of long objects. © Goodheart-Willcox Co., Inc.

Dimetric Projection Two axes making equal angles drawn at same scale. Third axis drawn at different scale. May be constructed by using revolution or auxiliary view. Approximate dimetric drawings more common. Common scale and axis combinations available. © Goodheart-Willcox Co., Inc.

Constructing a Dimetric Projection © Goodheart-Willcox Co., Inc.

Common Dimetric Axis Angle and Scale Combinations Used to simplify constructions in manual drafting. May be used with polar coordinates and tracking in 2D CAD drawings. Modeling and 3D viewing commands more typical in CAD. © Goodheart-Willcox Co., Inc.

Creating Dimetric Drawings in CAD Model created using 3D drawing commands. View oriented using 3D viewing commands. © Goodheart-Willcox Co., Inc.

Trimetric Projection Axes drawn at three different scales. Approximate trimetric drawings more common. Common scale and axis combinations available. © Goodheart-Willcox Co., Inc.

Constructing a Trimetric Projection © Goodheart-Willcox Co., Inc.

Common Trimetric Axis Angle and Scale Combinations © Goodheart-Willcox Co., Inc.

Constructing Circles in Dimetric and Trimetric Views Ellipse template is used in manual drafting. Auxiliary view method is most appropriate to determine ellipse angles. Ellipse angles for dimetric drawing are equal in two axis planes. Ellipse angles for trimetric drawing differ for each plane. © Goodheart-Willcox Co., Inc.

Construct Circles in a Dimetric or Trimetric Drawing © Goodheart-Willcox Co., Inc.

Advantages and Disadvantages of Dimetric and Trimetric Drawings Number of viewing positions unlimited. Common axis angles and scales simplify construction. Disadvantages Views more difficult to draw than other pictorials. © Goodheart-Willcox Co., Inc.

Oblique Projection Front view projected parallel to projection plane (true size). Projectors parallel to lines of sight. Oblique drawing less time-consuming and more common. © Goodheart-Willcox Co., Inc.

Oblique Drawing Types Cavalier oblique Cabinet oblique General oblique © Goodheart-Willcox Co., Inc.

Cavalier Oblique Receding axis typically oriented at 45. Receding axis and front axes drawn true length. © Goodheart-Willcox Co., Inc.

Cabinet Oblique Receding axis angle varies (30, 45, and 60 typical). Receding axis drawn at half scale. © Goodheart-Willcox Co., Inc.

General Oblique Receding axis angle varies from 0 to 90. Receding axis drawn between half and full scale. © Goodheart-Willcox Co., Inc.

Constructing Angles in Oblique Drawings © Goodheart-Willcox Co., Inc.

Constructing Arcs, Circles, and Curves in Oblique Drawings Features on front plane projected true size. Construction methods required on other planes. Ellipses may be drawn on cavalier oblique planes in CAD. 3D modeling and viewing commands more common in CAD applications. © Goodheart-Willcox Co., Inc.

Constructing Arcs, Circles, and Curves in Oblique Drawings © Goodheart-Willcox Co., Inc.

Selecting Views and Positions for Oblique Drawings To minimize distortion, orient long axes parallel to front plane. To show bottom surfaces, reverse direction of depth axis. © Goodheart-Willcox Co., Inc.

Oblique Dimensioning Conventions Similar to isometric dimensioning. Unidirectional system preferred. © Goodheart-Willcox Co., Inc.

Advantages and Disadvantages of Oblique Drawings Features on front plane can be drawn true size. Different types allow for control over scaling. Disadvantages Receding plane features take longer to draw. Long objects may appear distorted. © Goodheart-Willcox Co., Inc.

Perspective Drawing Most realistic form of pictorial drawing. Types classified by number of vanishing points used. Drawing layout principles more suitable for manual drafting than CAD. 3D modeling and viewing commands used in CAD. © Goodheart-Willcox Co., Inc.

Types of Perspective Drawings (American National Standards Institute) © Goodheart-Willcox Co., Inc.

Perspective Drawing Terms Station point Vanishing points Visual rays Picture plane Horizon line Ground line © Goodheart-Willcox Co., Inc.

Horizon Line Placement © Goodheart-Willcox Co., Inc.

One-Point Perspective Lines converge to single vanishing point. Frontal plane parallel to picture plane. Also called parallel perspective. Commonly used to illustrate interior construction. © Goodheart-Willcox Co., Inc.

Construct a One-Point Perspective Drawing © Goodheart-Willcox Co., Inc.

Construct a One-Point Perspective Drawing (Cont.) © Goodheart-Willcox Co., Inc.

Two-Point Perspective Lines converge to two vanishing points. Object planes inclined to picture plane. Also called angular perspective. Commonly used to illustrate large structures. © Goodheart-Willcox Co., Inc.

Construct a Two-Point Perspective Drawing © Goodheart-Willcox Co., Inc.

Construct a Two-Point Perspective Drawing (Cont.) © Goodheart-Willcox Co., Inc.

Perspective Views of Objects Lying Behind the Picture Plane Extend lines from top view to locate piercing points. Project verticals to ground line to locate true length lines. Draw receding planes and project points from top view. © Goodheart-Willcox Co., Inc.

Drawing Circles in Perspective Views © Goodheart-Willcox Co., Inc.

Construct Circles on Inclined Vertical Perspective Planes Divide front view and transfer points to top view. Project points to perspective view and to vanishing point. Project divisions from picture plane to perspective view. Draw perspective ellipse with template. © Goodheart-Willcox Co., Inc.

Construct Circles on Inclined Horizontal Perspective Planes Divide circle in top view and project points to sides. Project true length vertical “height” line. Project points from picture plane to perspective view. Project receding lines to locate ellipse points. Draw perspective ellipse with template. © Goodheart-Willcox Co., Inc.

Perspective Drawing Instruments Perspective grid Perspective drawing board Irregular curve Ellipse templates © Goodheart-Willcox Co., Inc.

Sketch a Perspective Drawing Locate vanishing points on horizon line. Sketch true length “height” line and receding lines. Sketch vertical lines at half scale to locate frontal planes. Sketch top surface. © Goodheart-Willcox Co., Inc.

CAD-Generated Pictorials Most commonly created as 3D models rather than 2D drawings. Typically made as renderings. 3D viewing commands normally used to orient view. © Goodheart-Willcox Co., Inc.

Review Questions 1. In axonometric projection, the object faces are all _____ to the plane of projection. inclined © Goodheart-Willcox Co., Inc.

Review Questions 2. An isometric drawing is one type of _____ projection. A. axonometric B. perspective C. orthographic D. oblique A. axonometric © Goodheart-Willcox Co., Inc.

Review Questions 3. In an isometric projection, the three drawing axes make equal _____ angles with each other. A. 30 B. 60 C. 90 D. 120 D. 120 © Goodheart-Willcox Co., Inc.

Review Questions 4. In CAD, the isometric drawing planes defined by the direction of the isometric axes are called the _____. isoplanes © Goodheart-Willcox Co., Inc.

Review Questions 5. In an isometric section view, section lines are normally drawn at an angle of _____. 60 © Goodheart-Willcox Co., Inc.

Review Questions 6. Isometric ellipses are drawn using the _____ command. A. Spline B. Section Plane C. Ellipse D. Circle C. Ellipse © Goodheart-Willcox Co., Inc.

Review Questions 7. Which of the following is not used to construct isometric circles in manual drafting? A. Ellipse template B. Trammel method C. Four-center approximate method D. Coordinate method B. Trammel method © Goodheart-Willcox Co., Inc.

Review Questions 8. The frontal plane of a(n) _____ drawing is parallel to the projection plane. A. dimetric B. trimetric C. oblique D. isometric C. oblique © Goodheart-Willcox Co., Inc.

Review Questions 9. A(n) _____ oblique drawing has the receding axis drawn at full scale. cavalier © Goodheart-Willcox Co., Inc.

Review Questions 10. In a(n) _____ perspective drawing, receding lines converge to a single vanishing point. A. one-point B. two-point C. three-point D. angular A. one-point © Goodheart-Willcox Co., Inc.

Review Questions 11. The _____ is an assumed point representing the position of the observer’s eye in a perspective view. A. ground line B. station point C. vanishing point D. picture plane B. station point © Goodheart-Willcox Co., Inc.

Review Questions 12. The vanishing points are located on the _____ in a perspective view. A. ground line B. horizon line C. projection plane D. picture plane B. horizon line © Goodheart-Willcox Co., Inc.

Glossary Axonometric projection Dimetric projection A projection method in which the projectors are perpendicular to the projection plane, but the faces of the object are inclined to the projection plane to achieve a pictorial effect. Dimetric projection A projection method in which two object faces are equally inclined to the plane of projection and two of the object axes make equal angles with each other. © Goodheart-Willcox Co., Inc.

Glossary Foreshortened Isometric axes Isometric grid Drawn shorter than true length. Isometric axes The normal drawing axes separated by equal angles of 120° in an isometric projection. Isometric grid A CAD function used to orient the drawing grid to an isometric pattern to aid in isometric drawing. © Goodheart-Willcox Co., Inc.

Glossary Isometric planes Isometric projection The regular isometric drawing planes used in constructing isometric views. Isometric projection A projection method in which all three principal faces of the object are equally inclined to the projection plane. Also, all three axes make equal angles with each other. © Goodheart-Willcox Co., Inc.

Glossary Isometric snap Isoplanes A CAD function that allows you to draw lines along isometric axes. Isoplanes In CAD applications, the left, right, and top drawing planes defined by the direction of the isometric axes. © Goodheart-Willcox Co., Inc.

Glossary Normal surfaces Oblique projection Surfaces that are parallel to the principal planes of projection. Oblique projection A form of one-plane projection in which the projectors are parallel to each other, but they meet the plane of projection at an oblique angle. © Goodheart-Willcox Co., Inc.

Glossary Perspective drawing Pictorial drawing A pictorial drawing in which receding lines converge at vanishing points on the horizon. Pictorial drawing A realistic, three-dimensional representation showing the width, height, and depth of an object. © Goodheart-Willcox Co., Inc.

Glossary Trimetric projection A projection method in which all three object faces make different angles with the plane of projection and the three object axes make different angles with each other. © Goodheart-Willcox Co., Inc.