Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

1. PublisherThe Goodheart-Willcox Co., Inc.Tinley Park, Illinois Technical Illustration Techniques and Applications PowerPoint by Anthony J. Panozzo

2. Chapter 5 Axonometric Drawing Techniques

3. Learning Objectives • Identify and explain the different types of pictorial and axonometric drawings. • Plan, lay out, and draw isometric views of objects containing normal, inclined, skewed, irregularly curved, and circular surfaces. • Use isometric ellipse templates, isometric protractors, and angle ellipse templates as drawing aids.

4. Learning Objectives • Identify and explain the primary applications of computer-generated axonometric drawings. • Develop drawings using the isometric, dimetric, and trimetric methods of pictorial drawing.

5. Pictorial Drawing • A style used to show all three dimensions of an object in a single view. • Used in technical illustration almost exclusively. • Each pictorial style can be further divided into specific classifications.

6. Pictorial Drawing

7. Axonometric Drawings There are three drawing types. • Isometric • Refers to equal measure. • Dimetric • Refers to two measures. • Trimetric • Refers to three measures.

8. Axonometric Drawings • In an isometric drawing, equal angles (120°) are used between each of the primary axes. • The scales used for each axis are also equal. • In a dimetric drawing, two of the angles used between the primary axes are equal. • Two of the scales for the axes are equal. • In a trimetric drawing, the axis intersections produce three different angles. • Three different scales are used for the axes.

9. Axonometric Drawings

10. Oblique Drawings • An oblique drawing is similar to an axonometric drawing. • A front view is parallel to the projection plane and top and side views are viewed at an oblique angle. • The width and height axes are full scale. • The receding axis scale varies depending on the type of drawing. • The receding axis angle can be any angle between 0 and 90.

11. Oblique Drawings There are three types. • Cavalier oblique • The receding axis is full scale. • Cabinet oblique • The receding axis is half scale. • General oblique • The receding axis is drawn at a scale other than one-half or full size.

12. Oblique Drawings Common receding axis angles and scale factors are typically used.

13. Perspective Drawings • Used to represent what is normally seen from a given viewing point. • Receding axis lines converge to a vanishing point as they recede. • There are three types related to the number of vanishing points. • One-point perspective • Two-point perspective • Three-point perspective

14. Perspective Drawings

15. Applications of Pictorial Drawings • Each style has advantages and limitations. • Select the most appropriate method for a given illustration. • Proper selection enhances viewer understanding and saves drawing time.

16. Axonometric Drawing Applications • Primary use is for rectangular objects with flat plane surfaces. • Curved and irregular shapes are difficult to show because of receding object faces. • Isometric drawings are the most used. • Advantages include ease of layout and scaling. • Disadvantages include a slight oversizing and distortion of proportion. • Dimetric and trimetric views can produce more realism but take longer to draw.

17. Oblique Drawing Applications • Primary use is for objects with circular, cylindrical, or irregular shapes easier to draw with a normal front view. • Also used for objects with one long axis.

18. Perspective Drawing Applications • Primary use is in architectural and interior design. • Very realistic views are used to show a specific viewing location and elevation. • More drawing time is required. • Most suitable for flat-surface objects with rectangular shapes.

19. Advantages of Pictorials • Provide the best way to represent an object. • Simplify what is shown for the viewer. • Quicker to draw than multiview drawings. • Hidden lines are normally excluded. • Placing part labels and notes is much quicker than dimensioning orthographic views.

20. Disadvantages of Pictorials • Present difficulty when dimensions are required for manufacturing. • The viewing angle may cause distortion in the object. • Hidden details may be difficult to visualize. • Complex shapes may be difficult to draw.

21. Isometric Projection • The object is rotated 45 to the frontal plane and tipped forward 35°16 from the horizontal plane. • Horizontal lines are drawn at 30 from the X axis. • In comparison to an isometric drawing, measurements are foreshortened by approximately 82%. • Foreshortening all measurements can make a true-scaled view difficult to draw.

22. Isometric Projection

23. Isometric Drawing • An isometric drawing is made at full scale. • The object is approximately 1.22 times larger than an isometric projection.

24. Isometric Drawing Types • Regular isometric drawing • Horizontal axes are drawn at 30° (most common). • Reversed axis isometric drawing • The orientation of the axes is the exact opposite of the regular axis isometric orientation. • Used to show details on the bottom of an object. • Long axis isometric drawing • Includes a major horizontal axis and two axes inclined at 60°. • Used to show features along one axis.

25. Isometric Drawing Types

26. Object Orientation in Isometric Views • Choose the best view where the desired features are emphasized. • The object should be drawn in its operating position orientation. • Select a different view if the most natural has many hidden features.

27. Drawing Isometric Lines and Nonisometric Lines • Horizontal and vertical isometric lines are always parallel to the isometric axes. • Nonisometric lines are inclined to the isometric axes. • To draw, each endpoint is first plotted on isometric lines. • Plotted points are then connected. • The block-in technique is useful and accurate.

28. Block-in Technique • First, draw an isometric block with light construction lines and the overall dimensions. • “Block in” the individual points of the profile and connect the points with isometric lines until the shape is defined. • Develop all normal isometric lines first, then one nonisometric surface at a time.

29. Block-in Technique • Locate the step features on the front face first. • Locate the corresponding points on the back plane of the block. • Connect the points with isometric lines.

30. Block-in Technique • Nonisometric lines and surfaces require additional steps. • Draw an isometric block with the overall dimensions. • Measure distances on each orthographic view and transfer to points on isometric lines parallel to axis lines on the block. • Connect the points with nonisometric lines. • Nonisometric lines are not true length and cannot be measured directly with a scale.

31. Block-in Technique (Nonisometric Surfaces)

32. Drawing Isometric Arcs, Circles, and Irregular Curves • Circles and arcs appear as ellipses in an isometric drawing. • The coordinate method simplifies the drawing process for arcs. • Points are located on curves using isometric lines as reference lines. • An orthographic view is commonly used to transfer coordinate points.

33. Coordinate Method • First, “block in” the basic object shape. • Identify coordinate points on the curved shape in the orthographic projection. • Transfer coordinates from the orthographic view to the corresponding points in the isometric view. • Connect the points in a smooth curve with an irregular curve or spline. • Locate points on the closest surface first, then background features.

34. Coordinate Method

35. Constructing Isometric Circles • The four-center method is more efficient than the coordinate method. • Plotting coordinates for a circle requires many points to provide a good shape definition. • Using arcs and center points on an isometric plane simplifies the process.

36. Four-Center Method • Locate the center of the isometric circle and draw a square around it with isometric lines. • Locate the midpoint on each side. • Draw lines from the corners to the opposite midpoints. • Draw the ellipse sides using the necessary radii and the corners as the centers. Draw the ends using the necessary radii and the line intersections as the centers. • Check for smoothness before darkening.

37. Four-Center Method • The radius values labeled R1 are for the ellipse sides. • The radius values labeled R2 are for the ellipse ends.

38. Four-Center Method • If the arcs do not meet properly, draw a correction arc. • Reset the compass to the proper radius of the small arc. • Draw arcs from the ends of the large arcs to locate a new center. • Draw the arc.

39. Centering Isometric Views • Regular isometric drawing • Locate the center of the drawing area. • Drop a vertical line from the center point one-half the maximum height of the object. • Draw a 30° line one-half the width of the object. To show the front face on the left, draw to the right. To show the back, draw to the left. • Draw a 30° line one-half the depth of the object in the opposite direction of the line drawn in Step 3. The endpoint is the bottom front or bottom rear corner of the object.

40. Centering Isometric Views

41. Centering Isometric Views • Reversed axis isometric drawing • Locate the center of the drawing area. • Draw a vertical line up from the center point one-half the maximum height of the object. • Draw a 30° line one-half the width of the object. To show the front face on the left, draw to the right. To show the back, draw to the left. • Draw a 30° line one-half the depth of the object in the opposite direction of the line drawn in Step 3. The endpoint is the top front or top rear corner of the object.

42. Centering Isometric Views

43. Centering Isometric Views • Long axis isometric drawing • Locate the center of the drawing area. • Drop a line from the center point one-half the width of the object at a 60° angle to horizontal. To show the front face on the left, draw to the right. To show the back, draw to the left. • Draw a 60° line one-half the object height in the opposite direction of the line drawn in Step 2. • Draw a horizontal line one-half the object depth in the same direction as the line in Step 3. The endpoint is the bottom front or rear of the object.

44. Centering Isometric Views

45. Isometric Drawing Aids • More types of templates are available for isometric drawing than for any other type of drawing. • US Customary and metric sizes are available. • There are three major types of templates. • Isometric ellipse template • Angle ellipse template • Isometric protractor

46. Isometric Ellipse Templates • Made of plastic with precise holes for tracing. • Used to draw ellipses on normal isometric surfaces. • Holes are 22% oversized (no calculations are needed). • Templates are labeled Isometric or 35°16.

47. Angle Ellipse Templates • Used for circular shapes inclined or skewed to the principal projection planes. • Holes are true size. • Use a larger ellipse to compensate for isometric oversizing. • For US Customary sizes, multiply the true size by 1 1/4 (1.25) and round to the closest size available. • For metric sizes, multiply the true size by 1.22 and round to the closest size available.

48. Angle Ellipse Templates • Full sets normally consist of a series of 10 separate templates. • Viewing angles range from 10° (very flat) to 55° (almost circular). • Templates progress in increments of 5°. • Templates are selected for different isometric surfaces with an isometric protractor.

49. Using Isometric Ellipse Templates • Align the proper axis lines with construction lines on the drawing. • The ellipse must have three-axis alignment. • The ellipse center is first aligned with the center of the hole or cylinder. • The ellipse is turned to align with the vertical axis and the appropriate horizontal axis.

50. Using Isometric Ellipse Templates • On vertical surfaces, the minor ellipse axis is parallel to the horizontal axis on the other side of the vertical axis and one axis line is vertical. • On horizontal surfaces, the minor axis is vertical and the major axis is horizontal.