At the conclusion of this unit you should be able to accomplish the following with a 70% accuracy

Transcription

1 7 Multiview Drawing OBJECTIVES At the conclusion of this unit you should be able to accomplish the following with a 70% accuracy 1. explain the importance of mulitview drawing as a communication tool far designers 2. explain the concept of multiview drawing through the use of the transparent box method 3. explain the concept of projection plans 4. use parallel projectors to develop mechanical drawings 5. use the three principle planes orthographic projection to develop mechanical drawing 5.1 frontal 5.2 horizontal 5.3 profile 6. use the six different view of a multiview drawing to develop mechanical drawing

2 Chapter 6 Multiview Drawing front 6.2 top 6.3 right side 6.4 left side 6.5 back 6.6 bottom 7. use three-view drawing to describe the physical shape of an abject 7.1 front 7.2 top 7.3 right wide 8. select the appropriate view(s) to describe the physical appearance of an object with the last amount of hidden lines 8.1 number of views 8.2 selecting of front view 9. apply the concept of paint numbering to the development of mulitview drawings 10. identify the type of plane and line in multiview drawings 11. apply the use of standard lines to multiview drawings 12. apply the rules of line conventions to multiview drawings 13. use standard techniques governing intersecting and overlapping lines in multiview drawing 14. center a multi view drawing 15. develop a three view drawing (given an isometric of an object or idea) based on line quality, correct scale, positioning, centering, and overall neatness of the drawing

3 3 Applied Geometry for Engineering Design General Information Many times pictorial drawings cannot give a full description of an object. Important details on a back, side or bottom surface may be hidden. A product cannot be manufactured without a completely detailed description of it. Because pictorial drawings usually cannot completely describe objects, the multiview drawing system is used to describe them. Multiview (mechanical drawing) is a system of representing three dimensional objects through the arrangement of separate two-dimensional views. These views are arranged in a standard manner, and the system used to construct them is called orthographic projection. If dimensions and specifications are noted on the multiview drawing, it is referred to as a working or detail drawing. The Transparent Box One way to explain and remember orthographic projection is through the use of a transparent box. The six sides of the transparent box are all two dimensional. Each side will provide two dimensions (width, height, or depth) of the three dimensional box. The front and back sides of the box provide the dimensions of width and height. The two sides of the box provide the dimensions of height and depth. And the top and bottom sides of the box provide the dimensions of width and depth. Now rename the front and back, sides, and the top and bottom of the box and call them projection planes. The front and back sides of the box will now be called and located on what is called the frontal projection plane. The two sides of the transparent box will now be renamed and located on what is called the profile plane. The top and bottom sides of the transparent box will now be called and located on what is called the horizontal plane. In each case the planes will contain the same two dimensions as the sides of the box which they replaced (see Figure 7.1). Now imagine that an object is placed within the transparent box. As you look into the box from the front you will see the front of the object through the side of the transparent box. If you were to draw the outline of the object on the side of the box it would be the same as projecting the outline of the object onto the frontal plane. This would give you the width and height of the object on the two dimensional frontal plane. This could be done to the back side of the box by projecting it onto the frontal plane of the transparent box. Each side of the box could be projected in a similar manner. The sides of the object would be traced (or projected) onto the sides (profile projection plane) of the transparent box

4 Chapter 6 Multiview Drawing 4 Figure 7.1 The orthographic transparent box.

5 5 Applied Geometry for Engineering Design and they would give you the dimensions of height and depth of the object. Finally, the top and bottom sides of the object could be traced (or projected) onto the top and bottom sides (horizontal plane) of the box and they would give you the dimensions of width and depth of the object (see Figure 7. 1). Now if the box is torn open and each side (or projection plane) is positioned on a flat surface, the different sides of the abject will describe all three dimensions of the object through separate two dimensional views. This is the basic concept of orthographic projection (sea Figure 7.1). Projection Planes There are three principle planes in orthographic projection: the frontal, profile and horizontal. Each projection plane of an object contains two views of the object. The frontal projection plane describes an object as it would appear if it were viewed from the front or from the back. Thus if a view of an object is from the front or back it is projected on the frontal plane. If a top or bottom view of an object is given then these views are located on the horizontal planes. And if a right or left side view of an object is given then these views are projected onto the profile projection plane. Any view located on a principle plane is called a principle view. Each principle view of an object will show two dimensions of the object (see Figure 7.2). Figure 7.2 The principle planes of orthographic projection.

6 Chapter 6 Multiview Drawing 6 Parallel Projection Each view of an object will be projected, with parallel projectors onto one of the principle projection planes. Parallel projection is the term given to the imaginary lines which are projected at ninety degrees from one side of an object and locate points on the imaginary projection plane. These points locate the outline of the object on the projection plane (see Figure 7.3). Figure 7.3 Parallel projectors. The Frontal Plane The front and back views of an object are projected onto the frontal plane; they are described by the dimensions of width and height (see figure 7.4). Figure 7.4 The frontal plane.

7 7 Applied Geometry for Engineering Design The Horizontal Plane The top and bottom views of an object are projected onto the horizontal plane. They are perpendicular to the frontal plane and are described by the dimensions of width and depth (see Figure 7.5). Figure 7.5 The horizontal plane. The Profile Plane The right and left-side views of an object are projected onto the profile plane. They are perpendicular to both the frontal and horizontal planes, and are described by the dimensions of height and depth (see Figure 7. 6). Figure 7.6 The horizontal plane.

8 Chapter 6 Multiview Drawing 8 The Six View Drawing The maximum number of views which can be located on the principle planes of an object is six. If you imagine an object located in the transparent box, there will be two views on the frontal plane, two views on the horizontal plane, and two views on the profile plane. When the transparent box is unfolded the top view will appear over the front view, the bottom view under the front view, the right-side view to the right of the front view, the left-side view to the left of the front view, and the back view to the left of the left-wide view. It is important that the views are located in this manner and that the projections from all views align both vertically and horizontally with the front view. This allows the dimensions of height, width, and depth to be shown commonly among the views, thus eliminating the need to repeat dimensions. This view arrangement is the standard arrangement used throughout much of the western world (see Figure 7. 7). This system of projection is ref erred to as 3rd angle projection. The system used in many European countries is called 1st angle projection and the arrangement of views may differ somewhat from the system presented here. Figure 7.7 The view drawing.

9 9 Applied Geometry for Engineering Design The Three view Drawing Although through the use of orthographic projection six views can be used to describe an object, most objects are commonly described through the use of the top, front, and right-side views. Many objects can be accurately described with three views since additional views will usually only duplicate information already supplied in one of the principle views ( see Figure 7. 8). Figure 7.8 The three view drawing. Many times an object can be described more accurately by using the front, top, And left-side views. If a left-hand view will describe an object more clearly then the left-side view should be used (see Figure 7.9). Figure 7.9 Use of the left-side view.

10 Chapter 6 Multiview Drawing 10 Some objects may require either more or fewer than three views to properly describe them. If this is true than use the number of views needed to properly describe the object. One and Two View Drawing Many objects can be described through the use of one or two view drawings. If two views completely describe an object than only use two views to describe the object. Cylindrical parts and parts with uniform thicknesses can be described by one view. However, the one view drawing must contain a note which describes the missing view or gives the thickness of the object (see Figure 7.10). Figure 7.10 The one and two view drawings. View Selection The criteria for selection of views in multiview drawing is based on the view which fully describes the object with the fewest number of hidden lines or shows the outside contour of the object in the most descriptive manner. This view will be used as the front view. All other views are than projected from the front view. In Figure 7.11 "A" would be used as the front view because it describes the outside contour of the object (see Figure 7.11).

11 11 Applied Geometry for Engineering Design Figure 7.11 Selection of the front view an object. The front, top, and side views are considered the standard views of many objects. A chair; for example, has a front, top, and side view which can be recognized by everyone. Thus the views describing the chair should properly correspond to the commonly recognized views of the chair (see Figure 7. 12). Figure 7.12 View selection of a chair. Point Numbering If you are having trouble interpreting a multiview drawing of an object a method of numbering points on the object may be helpful in the visualization of it. Figure

12 Chapter 6 Multiview Drawing is an example of point numbering. Each point is labeled on the isometric drawing. These points are then transferred to the multiview drawing. The points which are closest to you (5 & 6 on the front view of Figure 7. 13) will be labeled on the outside of the multiview drawing. The paints which are farthest away from you (7 & 8 on the front view of Figure 7. 13) will be labeled on the inside of the multiview drawing (see Figure 7. 13). Figure 7.13 Point Numbering. Lines and Planes In multiview drawing a line can appear as a point, true length, or foreshortened. A plane can appear as an edge, true size, or foreshortened (see Figure 7.14). Figure 7.14 Lines and planes in multiview drawing.

13 13 Applied Geometry for Engineering Design Standard Lines As mentioned in chapter two, different types of lines with varying line weights will represent various components of an object in multiview drawing. Depending on the paper, different leads are used to produce standard lines. Except for guidelines and construction lines which are drawn very light, all other lines are drawn black. Standard lines are Distinguished by their varying widths and configurations. Designers must know the difference between the standard lines and how to apply them to multiview drawings (see Figure 7. 15) Object Lines Object lines are the most important lines on a multiview drawing. They represent the actual outline of an object. Object lines like all other lines except for construction lines and guidelines should be drawn to appear as black as ink. Their width (.5mm) should be consistent throughout the drawing (see Figure 7.15). Figure 7.15 Standard lines or the alphabet of lines. Hidden Lines Hidden lines as their name implies represent surfaces which cannot be seen in a view of an object but must be shown to represent the object completely. Hidden

14 Chapter 6 Multiview Drawing 14 lines are drawn as short black dashes (118", 3mm) with a small break (1/16", 2mm) lef t between the dashes. Like object lines their width is.5mm (see Figure 7.15). Center lines Center lines are used to locate the center paints for circles and to describe axes of symmetry. They are drawn as alternate long ( 3/4", 19mm to 1 1/2", 38mm) and short (1/8", 3mm) dashes. The space between the dashes should be 1/16" (2mm). When the center paint of a circle is described by center lines the short dashes are intersected. The line weight of center lines is 0.3mm (See Figure 7.15). Although object, hidden, and center lines are the most commonly used type of lines, you should be able to recognize and draw all the other standard lines. These are drawn as they should appear on a drawing in Figure Line conventions Line conventions are the rules which govern overlapping and intersecting lines in multiview drawing. If two lines are located in the same position on a multiview drawing, object lines will take precedence overall other lines. Hidden lines will take precedence over all other lines, followed by center lines if the lines in the same location (see Figure 7.16). Figure 7.16 Line conventions in multiview drawing.

15 15 Applied Geometry for Engineering Design Intersecting lines It is common for lines to overlap and intersect each other in multiview drawings. When this occurs the overlapping and intersecting lines are drawn in a standard manner which is understood by all designers (see figure 7.17). Figure 7.17 Intersecting and overlapping lines techniques. Centering a Multiview Drawing There are many ways to center a multiview drawing. Depending on the number of dimensions and notes needed to explain an object more space may be needed between the views of the drawing. The method explained here will leave equal distance between the front and side views horizontally and the front and top views vertically in a multiview drawing. To center the front and side views of a multiview drawing: 1) determine the horizontal drawing space between the border lines, 2) add the width from the

16 Chapter 6 Multiview Drawing 16 front view to the depth of the side view, 3) subtract the combined distance of the front and side views as determined in step two from the drawing area between borders from step one, 4) divide t his number by three, 5) locate this distance in from either t he left or right hand border line. Use the same procedure to locate the bottom line of the front view or the top line of the top view. The intersection of vertical and horizontal centering lines will be the beginning point of construction for the multiview drawing (see Figure 7.18). Figure 7.18 Centering a multiview drawing. Summary A thorough understanding of orthographic projection and how to apply multiview drawing is essential to designers. Through the use of multiview drawing almost any object idea can be presented. But without the knowledge of how to properly use multiview drawings, the effectiveness of an idea or the description of an object may not be complete or expressed properly.

17 17 Applied Geometry for Engineering Design Technical terns 1. Frontal plane - the projection plane onto which the front and back views of an object are projected and describes the height and width of the object. 2. Horizontal plane - the projection plane onto which the top and bottom views of an object are projected and describes the width and depth of the object. 3. Line conventions - rules which exist concerning overlapping and intersecting lines in multiview drawing. 4. Multiview drawing - a system of representing three dimensional objects through the arrangement of separate two dimensional views of the object. 5. Orthographic projection - the representation of an object with the use of various two dimensional views which are projected onto a projection plane with the use of parallel projectors. 6. Parallel projectors - imaginary lines which are drawn perpendicular to an object and locate a view of the object onto a projection plane. 7. Perpendicular a line or plane which is located 90 degrees to another line or plane. 8. Profile plane - the projection plane onto which the right and left-side views of an object are projected and describes the height and depth of the object. 9. Projection - the concept of projecting or drawing one surface of an object onto a plane. 10. Projection plane - an imaginary plane or surface onto which a view of an object is drawn. 11. Six view drawing - an orthographic projection of an object which describes the object with the use of the front, top, right-side, left-side, back, and bottom views. 12. Standard lines - lines which are universal to the field of mechanical drawing, and represent various surfaces of objects.

18 Chapter 6 Multiview Drawing Three view drawing - an orthographic projection of an object which typically describes the object with the use of a front, top, and side view. 14. Working drawing - a mechanical drawing which contains dimensions and specification notes.

19 19 Applied Geometry for Engineering Design Assignment 5.1 DIRECTIONS: Place the letter from the surface of the object in the multiview drawing onto the corresponding circle on the isometric drawing. The assignment grade will be based upon the correct identification of the surfaces on the isometric drawing (objectives 3, 4, 5, 6, a, 10, & 11). DIRECTIONS: Place the letter from the surface of the object in the isometric drawing onto the carrespand1ng circle on the multiview drawing. The assignment grade will be based upon the correct identification of the surfaces on multiview drawing (objectives 3, 4, 5, 6, 8, 10, & 11).

20 Chapter 6 Multiview Drawing 20 Assignment 5.2 DIRECTIONS: Sketch in the missing lines needed to complete the three-view drawings. The assignment grate will be based upon correct completion of the multiview drawings (objectives 6, B, 10, & 11).

21 21 Applied Geometry for Engineering Design Assignment 5.3 DIRECTIONS: Sketch the correct amount of views needed to completely describe the given objects. The assignment grade will be based upon correct view selection, proper projection techniques, use of standard lines, line conventions and rules governing intersecting and overlapping lines (objectives 5, 6, 7, 9, 10, 11, 12, 13, & 14).

22 Chapter 6 Multiview Drawing 22 Assignment 5.4 DIRECTIONS: Select a scale and draw the following three view drawings by completing the missing view. The assignment grade will be based upon proper. Multiview drawing techniques, line quality, centering and overall neatness (objectives 6, 8, 10, 11, 12, 13, & 14).