CLASS views from detail on a grid paper. (use appropriate line types to show features) - Optional views. Turn in for grading on class 6 (06/04)

Transcription

1 CLASS 4 Review: - Projections - Orthographic projections Lab: - 3 views from detail on a grid paper. (use appropriate line types to show features) - Optional views. Turn in for grading on class 6 (06/04) Home work: - Multiview Projection Simple (duplicate). Turn in for grading on class 6 (06/04) - Read chapter ORTHOGRAPHIC PROJECTION from the book

2 OBJECTIVES 1. Recognize and sketch the symbol for third-angle projection. 2. List the six principal views of projection. 3. Sketch the top, front, and right-side views of an object with normal, inclined, and oblique surfaces. 4. Understand which views show depth in a drawing showing top, front, and right-side views. 5. Know the meaning of normal, inclined, and oblique surfaces. 6. Transfer depth between the top and right-side views. 7. Label points where surfaces intersect. 2

3 PROJECTIONS!!!

4 Perspective Projection Parallel projection

5 Perspective Projection 5

6 Orthographic Projection (Multiview Projection) 6

7 Orthographic Projection The orthographic projections shows the object as it looks from the front, right, left, top, bottom, or back, and are typically positioned relative to each other according to the rules of either first angle or third angle projection. The origin and vector direction of the projectors (also called projection lines) differs, as explained below. 7

8 Different Viewpoint

9 Orthographic Projection

10 Standard 2D views!!!

11 The Principal Dimensions of an Object!!!

12 The system of views is called multiview projection. Each view provides certain definite information. For example, a front view shows the true shape and size of surfaces that are parallel to the front of the object. Views of Objects

13 Multiview Projection The system of views is called multiview projection. Each view provides certain definite information.

14 The Six Standard Views Any object can be viewed from six mutually perpendicular directions,

15 Revolving the Object to Produce Views Revolving the Object to Produce Views. You can experience different views by revolving an object.

16 Principal Dimensions The three principal dimensions of an object are width, height, and depth. The front view shows only the height and width of the object and not the depth. In fact, any principal view of a 3D object shows only two of the three principal dimensions; the third is found in an adjacent view. Height is shown in the rear, left-side, front, and right-side views. Width is shown in the rear, top, front, and bottom views. Depth is shown in the left-side, top, right-side, and bottom views.

17 Projection Method The outline on the plane of projection shows how the object appears to the observer. In orthographic projection, rays (or projectors) from all points on the edges or contours of the object extend parallel to each other and perpendicular to the plane of projection. The word orthographic means at right angles. Projection of an Object

18 Horizontal and Profile Projection Planes Specific names are given to the planes of projection. The front view is projected to the frontal plane. The top view is projected to the horizontal plane. The side view is projected to the profile plane.

19 The Glass Box One way to understand the standard arrangement of views on the sheet of paper is to envision a glass box. If planes of projection were placed parallel to each principal face of the object, they would form a box.

20 Unfolding the Glass Box To organize the views of a 3D object on a flat sheet of paper, imagine the six planes of the glass box being unfolded to lie flat.!!! Note the six standard views (front, rear, top, bottom, right side, left side).

21 The Glass Box Unfolded Lines extend around the glass box from one view to another on the planes of projection. These are the projectors from a point in one view to the same point in another view.

22 Transferring Depth Dimensions The depth dimensions in the top and side views must correspond point-for-point. When using CAD or instruments, transfer these distances accurately. You can transfer dimensions between the top and side views either with dividers or with a scale. You may find it convenient to use a 45 miter line to project dimensions between top and side views.

23 Necessary Views The top, front, and right-side views, arranged together, are called the three regular views because they are the views most frequently used. A sketch or drawing should contain only the views needed to clearly and completely describe the object.

24 Choice of Front View The view chosen for the front view in this case is the side, not the front, of the automobile.!!! The most descriptive view is chosen as the front view

25 Third Angle Projection USA, Canada First Angle Projection Europe, Asia

26 !!! Third Angle Projection USA, Canada First Angle Projection Europe, Asia

27 Hidden Lines Thick, dark lines represent features of the object that are directly visible. Dashed lines represent features that would be hidden behind other surfaces.

28 Centerlines The centerline pattern is used to: show the axis of symmetry for a feature or part indicate a path of motion show the location for bolt circles and other circular patterns The centerline pattern is composed of three dashes: one long dash on each end with a short dash in the middle.

29 PRECEDENCE OF LINES A visible line always takes precedence over and covers up a centerline or a hidden line when they coincide in a view (A and B). A hidden line takes precedence over a centerline (C).

30 Centerlines continued Centerlines (symbol: ) are used to indicate symmetrical axes of objects or features, bolt circles, and paths of motion.

31 Standard Views of Primitive Solids

32 View Orientation Poor orientation Good orientation

33 Use minimum number of views to describe the object Select the most descriptive views

34 Conventional Practices - Intersections

35 Miter Lines Miter lines are used to transfer depth information. 45 o line drawn from point O!!! O Standard multiviews

36 Fillets, Rounds & Chamfers

37 Top view

38

39 Edge Lines Principal & Inclined 2 Principal lines appear vertical, horizontal or as point views. Inclined lines appear inclined in one view.

40 Edge Lines Oblique Oblique line appears inclined in all views 40

41 Principal Planes Principle planes are parallel to principal orthographic planes

42 Inclined Planes Inclined planes are perpendicular to two opposite orthographic planes.

43 Oblique Planes Oblique planes are neither parallel nor perpendicular to any principal orthographic planes.

44 Type of Planes Oblique Principal Inclined

45 VIEWS OF SURFACES There are terms used for describing a surface s orientation to the plane of projection. The three orientations that a plane surface can have to the plane of projection are normal, inclined, and oblique. Note how a plane surface that is perpendicular to a plane of projection appears on edge as a straight line

46 Edge View of a Plane Principal planes appear in true size in one plane and as an edge view in the other two planes.

47 Ken Youssefi Mechanical and Aerospace Engineering Dept., SJSU 47

48 5/8 Ken Youssefi Mechanical and Aerospace Engineering Dept., SJSU 48

49 Instructions: 1. Draw a Front View. Leave space on the bottom for the name of the view. 2. Project construction lines to the Top and Right Side views. 3. Draw Top view. Draw a Miter Line. Using Miter line transfer measurements to the Right side view. 4. Do not use ruler for taking measurements. 5. Place names (1/8 height) of the views on 5/8 distance form the bottom of each view