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Ch 3
- 1. ORTHOGRAPHIC PROJECTION MULTI-VIEW DRAWING By Mr Leliso H.
- 2. ORTHOGRAPHIC PROJECTION Orthographic projection is a technique that is used to create multi-view drawings, is a system of drawing views of an object using perpendicular projectors from the object to a plane of projection.
- 3. Tuesday, October 22, 2019 3 Multiview Drawing A Multiview drawing is one that shows two or more two-dimensional views of a three- dimensional object. Multiview drawings provide the shape description of an object. When combined with dimensions, multiview drawings serve as the main form of communication between designers and manufacturers.
- 4. Third-angle Projection First-angle Projection First and Third Angle Projections • first Angle – Europe • Third Angle – U.S.
- 5. • Third Angle Projection • First Angle Projection First Versus Third Angle Projection
- 6. Symbols for 1st & 3rd Angle Projection Third angle projection is used in the U.S., and Canada
- 8. Revolving an Object to Produce the Six Basic Views
- 9. The Six Basic Views
- 10. Possible Views Top Front Right SideLeft Side Bottom Back
- 11. Terminology to Relate Views • Adjacent view – A view that is separated by a fold line – The top view is an adjacent view to the front view • Central View – A view that is between two adjacent views – The front view is the central view of the top, front, and right side view • Related views – Two views that are adjacent to a central view – The top and right side view are related views since they are both adjacent to the front view
- 12. Selection of Views • Not all 6 views have to be shown in an orthographic projection drawing. • Details are repeated in the top and bottom, right and left, and the front and back views.
- 13. General Rules for selecting views • The view that best describes the object should be selected as the front view. • Only views that clearly describe the object are used. • Normally the longest dimension is chosen as the width (or depth) • Views that show the least hidden lines should be selected. • The object should be shown in it’s functioning position if possible. • Most common combination of views is to use: – Front, Top, and Side View (should kept aligned) • Any other view different from the Principal Views is called an Auxiliary View.
- 14. Why must views be arranged so that they align? To make it possible for someone to interpret the drawing. TOP LEFT FRONT RIGHT BOTTOM REAR The Standard Arrangement of Views
- 15. The Glass Box Method • Most powerful technique to understand orthographic projections • Suspend the object with transparent strings inside a glass box • Imagine that the object you are going to draw is positioned inside a glass box, so that the large flat surfaces of the object are parallel to the walls of the box. • From each point on the object, imagine a ray, or projector perpendicular to the wall of the box forming the view of the object on that wall or projection plane. • Freeze the view from each direction (each of the six sides of the box) and unfold the box
- 16. There are a total of six glass walls surrounding the object. Each wall represents a projection plane onto which a two- dimensional object view will be created. Animation Example - 1
- 17. Start by focusing only on the front projection plane. A person standing in front of the object would see only the five corners identified in black.
- 18. Projection lines are used to project each corner outward until they reach the projection plane.
- 19. The visible edges of the object are then identified on the projection plane by connecting the projected corners with object lines.
- 20. The orthographic projection process is then repeated on the other projection planes.
- 21. Animation Example - 2
- 27. All three-dimensional objects have: width, height, and depth. Width is associated with an object’s side- to-side dimension. Height is the measure of an object from top-to-bottom. Depth is associated with front-to-back distance. Transferring Dimensions
- 28. Continued…
- 29. Using a Miter Line to Transfer Depth 1. Draw miter line at 45 degrees at a convenient distance to produce the desired view.
- 30. 2. Sketch light lines projecting depth locations for points to miter line and then down into side view as shown.
- 31. 3. Project additional points, surface by surface.
- 32. 4. Draw the view locating each vertex of the surface on the projection and miter line.
- 33. Projection Planes versus Views • Projection planes: – Object formed from projection lines projected perpendicularly onto a projection plane – Planes: Horizontal, frontal, and profile – Each projection plane is perpendicular to adjacent projection planes • Principle views – The object is rotated 90 degrees about the horizontal or vertical axis to give six principle views (top, bottom, front, rear, left, and right side) – Common views: top, front, and right side
- 34. Only use Necessary Views • One view drawings – Sphere (Football) • Two view drawings – Cylindrical parts – Show the circular and rectangular view • Three view drawings – Usually sufficient for all other drawings – Top, front, and right side view
- 35. Additional Examples on Necessary Views A sketch or drawing should only contain the views needed to clearly and completely describe the object. Choose the views that show the shape most clearly, have the fewest hidden lines, and show the object in a usual, stable, or operating position. One view drawing of a shim One view drawing of a connecting rod
- 36. Two-View Drawings • Some objects can be fully described by two views, look for: – Symmetry or Bodies of Rotation Front View Right Side View Front View Right Side
- 38. Hints for Multi-View Sketching • Identify the major features and overall dimensions of the object • Do not use any straight-edge devices as a pencil guide when sketching by hand • Start by drawing bounding boxes with light construction lines. • Keep views aligned while sketching
- 39. • The six standard views are often thought of as produced from an unfolded glass box. • Distances can be transferred or projected from one view to another. • Only the views necessary to fully describe the object should be drawn. Summary
- 40. Review Questions • Based on the lines of sight, orthographic projection drawings are classified as ___________ projections • There are ____ standard principal views of orthographic projections • Each view in an orthographic projection concentrates on ____ dimensions of the object
- 41. A Question… Each of the blocks at right has the same overall dimensions and color. What else do they have in common?
- 42. Answer… They all have identical top views!
- 44. Add Notch in Side View
- 46. Add Sloped Features in Front
- 48. Add Notch in Top View
- 50. Finished object
- 51. COMPARE BEGINNING TO END Tuesday,October22,2019 51
- 52. - EXERCISES Tuesday,October22,2019 52 Take 10 minutes to complete the views