Engineering Graphics Visualization & Design Manual

1. Visualization and Design Engineering Graphics Stephen W. Crown Ph.D.

2. Objective • How to represent a 3-D object effectively on a 2-D drawing surface (pictorials) • How to visualize a 3-D object using solid primitives

3. Overview • Sketching Review • Pictorials • Perspective • Parallel projection • Other Visualization Tools • Solid primitives • Miscellaneous

4. Sketching (review) • Definition • A rough freehand drawing used to document, communicate, and refine ideas developed primarily in the ideation phase of the design process • Follows standard practices • A developed skill • Should be the first step of any CAD or mechanical drawing (including homework assignments)

5. Pictorial Sketches • Definition:A sketch developed for ease of visualization that shows an objects height, width, and depth in a single view • Particularly useful for non-technical audiences • Assembly drawings • Marketing • Helpful in the ideation phase of the design process • How we picture objects in our mind • How we visualize spatial relationships

6. Pictorial Sketches • Parallel Projection • Parallel lines are always drawn parallel • Easy to draw • Often appears distorted • Two common types • Oblique Pictorials • Isometric Pictorials • Perspective Projection • Conveys information about distance and size • Not as common as parallel projection

7. Parallel Projection Pictorials • Oblique Pictorials • The simplest pictorial to sketch • Surfaces which are parallel to the front face are undistorted as in a multiview drawing • Circular features should be placed in the front view if possible • Draw the front face first • Lines which are perpendicular to the front face are drawn at an angle of 30 to 45o

8. Parallel Projection Pictorials • Oblique Pictorials • Cavalier Oblique • Depth is drawn full size • Object looks distorted (depth is exaggerated) • Cabinet Oblique • Depth is drawn to 1/2 of full size • Depth appears more accurate (2/3 is best) • Circular features which are not parallel to the front plane appear elliptical

9. Axonometric Pictorials • Trimetric • no equal angles • gives the most visually pleasing view • Dimetric • Two equal angles • Isometric • Three equal angles (120o) • Height drawn along vertical axis • Width and depth drawn at 30o to horizontal axis • Other orientations (reversed and long axis)

10. Parallel Projection Pictorials • Isometric Pictorials • Most common • Surfaces on all principle planes are distorted • All circles appear as ellipses • Perpendicular lines are drawn at 60 or 1200 angles • Height drawn along vertical axis • Width and depth drawn at 30o to horizontal axis

11. Parallel Projection Pictorials • Isometric Pictorials • Begin drawing by blocking in height, width and depth of entire object. • Continue to block in smaller features • Add curved surfaces last • circles appear as ellipses • lines tangent to arcs locate the edge of curved surfaces • Isometric grid paper is often helpful • follow direction of axis and count intersections • use tracing paper or grid paper with light lines

12. Isometric Projection and Isometric Drawings • Rotate about the Z axis 45o • Rotate about the X axis by an angle of q=sin-1(2/3)½ • An isometric projection is a true size projection • length along projected axes is L*(2/3)½ • An isometric drawing is drawn full scale along axes • objects are increased in size by a factor of (3/2)½

13. Perspective Projection Pictorials • The most difficult to draw • The most visually accurate • The use of vanishing points • One point • Lines of height and width are parallel • Like a “perspective oblique” • Two points • Only lines representing height are parallel • most common perspective view • Three points • No lines are parallel

14. Other Visualization Tools • Solid primitives • Box (Parallelepiped) • Cylinder • Cone • Sphere • Wedge • Extrude a 2-D shape • Revolve a curve about an axis

15. Other Visualization Tools • Operations on solid primitives • Add • assembly • welding • Subtract • drilling • milling/machining • Intersection • only regions where both part are in common are retained • helpful to produce mating parts

16. Other Visualization Tools • Right hand rule • Your thumb, index finger, and middle finger represent the X, Y, and Z axis respectively. • Point your thumb in the positive axis direction and your fingers wrap in the direction of positive rotation

17. Other Visualization Tools • Always rotate parts using full 90 degree rotations • Number vertices in different views of multiview and isometric drawing • Practice