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TED 105: Communicating Technical Designs

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1 TED 105: Communicating Technical Designs
Sketching Principles of EngineeringTM Unit 2 - Lesson 2.1 – Sketching TED 105: Communicating Technical Designs Sketching and Shape Description Straight Lines Circles and Arcs Proportions Generating Technical Designs Project Lead The Way, Inc. Copyright 2007

2 Purpose The main purpose of sketching is to convey ideas. Engineers have to use sketches to brainstorm ideas, as well as, to show others what they are working on or what should be designed. Sketches are also used to document measurements from the field before they are produced as solid models on the computer.

3 Sketching Principles of EngineeringTM Unit 2 - Lesson 2.1 – Sketching Freehand Sketching Most original designs are first expressed on medium as a freehand sketch. Used for: Amplifying and clarifying Recording verbal explanations Most original design ideas find their first expression through the medium of a freehand sketch, Freehand sketching is a valuable means of amplifying and clarifying, as well as recording, verbal explanations. Executives sketch freehand daily to explain their ideas to subordinates. Engineers often prepare their designs and turn them over to their detailers or designers in this convenient form as shown in the well-executed sketch of details for a steam locomotive. Freehand sketches are of great assistance to designers in organizing their thoughts and recording their ideas. Sketching is an effective and e conomical means of formulating various solutions to a given problem so that a choice can be made between them at the outset. Often much time can be lost if the designer starts his or her scaled layout before adequate preliminary study with the aid of sketches. Information concerning changes in design or covering replacement of broken parts or lost drawings is usually conveyed through sketches. Project Lead The Way, Inc. Copyright 2007

4 Sketching Principles of EngineeringTM Unit 2 - Lesson 2.1 – Sketching Technical Sketching Engineers’ view: ability to render serviceable sketches greater value than skill to create instrument drawings Freehand sketch should not mean crude and sloppy Freehand sketch should be made with care and attention to proportion, clarity, and line widths. Many engineers consider the ability to render serviceable sketches of greater value to them than skill in instrument drawing. The designer, technician, or engineer will find daily use for this valuable means of formulating, expressing, and recording ideas. The degree of perfection required in a given sketch depends on its use. Sketches hurriedly made to supplement oral description may be rough and incomplete. On the other hand, if a sketch is the medium of conveying important and precise information to engineers, technicians, or skilled workers, it should be executed as carefully as possible under the circumstances. The term "freehand sketch" is too often understood to mean a crude or sloppy freehand drawing in which no particular effort has been made. On the contrary, a freehand sketch should be made with care and with attention to proportion, clarity, and correct line widths. Project Lead The Way, Inc. Copyright 2007

5 Types of Sketches Types of Sketches
Sketching Principles of EngineeringTM Unit 2 - Lesson 2.1 – Sketching Types of Sketches Types of Sketches Since technical sketches are made of three-dimensional objects, the form of the sketch conforms approximately to one of the four standard types of projection, as shown above. In multiview projection, (a), the object is described by its necessary views. Or the object may be shown pictorially in a single view, by axonometric (isometric), oblique, or perspective sketches, (b), (c), and (d), . Project Lead The Way, Inc. Copyright 2007

6 Scale Typically not made to any scale. Correct proportions are needed.
Sketching Principles of EngineeringTM Unit 2 - Lesson 2.1 – Sketching Scale Typically not made to any scale. Correct proportions are needed. Size of sketch: Optional Determined by: Complexity of object Size of paper Small objects may be enlarged to show details clearly. Sketches usually are not made to any scale. Objects should be sketched in their correct proportions as accurately as possible, by eye. However, cross-section paper provides a ready scale (by counting squares) that may be used to assist in sketching to correct proportions. The size of the sketch is purely optional, depending on the complexity of the object and the size of paper available. Small objects are often sketched oversize so as to show the necessary details clearly. Project Lead The Way, Inc. Copyright 2007

7 Do you want to be a good sketcher?
Practice

8 Purpose Proper documentation in a notebook is essential. When proper documentation is made, ideas are not lost and projects can be duplicated. The sketch on the next slide is a sample from a notebook where a sketch was made and notes as well as dimensions have been documented.

9 Proposed Notebook Sample
Size requirements. Shows design details Title Initialed and dated.

10 Sketching Techniques Line Types: Inclined Line Vertical Line
Horizontal Line

11 Sketching Techniques Finding the slope angle of an inclined line:
Equation: tans = RISE/RUN tans = 2/4 tans = .5 s = arctan .5 Run = 4 Rise = 2 Note: Rise and Run units do not matter (As long as the units are the same). You are finding an angle. In the above case, we are counting grid boxes.

12 Sketching Techniques Sketching a Line.

13 Sketching Techniques Sketching an Arc

14 Sketching Techniques Sketching an Arc

15 Sketching Techniques Sketching a Circle 1) Setup the diameter
2) Square in the 3) Sketch diagonals

16 Sketching Techniques Sketching a Circle 4) Identify triangle centers
5) Sketch arcs

17 Sketching Principles of EngineeringTM Unit 2 - Lesson 2.1 – Sketching Size and Proportion Although you have learned to draw lines and arcs, you can not communicate properly until you understand how to sketch with the correct size and proportion. Without proper size and proportion your sketch will not look right. Size: Length, width, height, distance. How big is the object you are sketching? Proportion: If two objects are five feet apart in real life, then those two objects must appear to be five feet apart in your sketch. The most important rule in freehand sketching is keep the sketch in proportion. No matter how brilliant the technique or how well the small details are drawn, if the proportions especially the large overall proportions are bad, the sketch will be bad. First, the relative proportions of the height to the width must be carefully established; then as you proceed to the medium sized areas and the small details, constantly compare each new estimated distance with already established distances. Project Lead The Way, Inc. Copyright 2007

18 Size and Proportion How to create proper size and proportion.
Technique I Using a pencil to measure. Hold your pencil at arms length as you see in Figure 2. Use the top of the pencil and your thumb as a distance for the height of the window. This distance will be used as a reference for sketching the rest of the house as we did in the house on the next slide. Figure 2

19 Size and Proportion How to create proper size and proportion.
Technique I Using a pencil to measure. As you see in the completed house in Figure 3, the units of the numbered dimensions are in windows. You should also notice that the use of graph paper also helps in creating proper size and proportion. Figure 3

20 Size and Proportion How to create proper size and proportion.
Technique II Boxing in the sketch. Figure 4 In Figure 4 we are sketching a chair. We sketch the boxes to the largest outside dimensions of our final object. Notice that light construction lines are also used to help guide us to the proper size and proportion.

21 Size and Proportion How to create proper size and proportion.
Technique II Boxing in the sketch. Figure 5 Finally we use our sketching techniques for drawing arcs, lines and circles to complete our chair in Figure 5. Notice the box we started with is still existent as light construction lines. These are our guides for proportion and size.

22 Alphabet of Lines Technique of Lines
Sketching Principles of EngineeringTM Unit 2 - Lesson 2.1 – Sketching Alphabet of Lines Technique of Lines The chief difference between an instrument drawing and a freehand sketch lies in the character or technique of the lines. A good freehand line is not expected to be as rigidly straight or exactly uniform as an instrument line. While the effectiveness of an instrument line lies in exacting uniformity, the quality of freehand line lies in its freedom and variety. Conventional lines, drawn instrumentally, are shown in Fig The freehand construction line is a very light rough line in which some strokes may overlap. All other lines should be dark and clean-cut. Accent the ends of all dashes, and maintain a sharp contrast between the line thickness. In particular, make visible lines heavy so the outline will stand out clearly, and make hidden lines, centerlines, dimension lines, and extension lines thin. Project Lead The Way, Inc. Copyright 2007

23 Alphabet of Lines Short Break Line: A freehand
drawn line that shows where a part is broken to reveal detail behind the part or to shorten a long continuous part. (See example of Long Break Line on the next slide.) Object Line: Thick lines about .6mm(.032in) that show the visible edges of an object. Hidden Line: Lines used to show interior detail that is not visible from the outside of the part. Center Line: Lines that define the center of arcs, circles, or symmetrical parts. They are half as thick as an object line. Section Lines: Lines are used to define where there is material after a part of the object is cut away. Construction Line: Very lightly drawn lines used as guides to help draw all other lines and shapes properly. Usually erased after being used.

24 Alphabet of Lines Long Break Lines: Break lines are used
to either show detail or as in this case they can be used to shorten very long objects that do not change in detail. Notice that this part is 12” long however we have shortened the drawing with break lines to use our space more efficiently. Dimension Lines: Lines that are used to show distance. Arrows are drawn on the ends to show where the dimension line starts and ends. The actual distance is usually located in the middle of this line to let you know the distance being communicated. Dimension lines are used in conjunction with extension lines to properly dimension objects. Cutting Plane Line: A line used to designate where a part has been cut away to see detail. The arrows should point in the direction that you are looking at the cutout. Extension Lines: Lines used to show where a dimension starts and stops on an object. Used with dimension lines to properly dimension an object. The line is 1/16” away from the part as to not get confused with the object lines Leader Lines: Leader lines are used to show dimensions of arcs, circles and to help show detail. An arrow head is used to point to the part you are dimensioning and the line comes off the arrow point usually at a 45 degree angle. At the end of this line a horizontal line is drawn with a note at the end telling information about what is being pointed at. How many lines from the previous slide can you identify here?

25 Alphabet of lines Phantom Lines: Phantom lines are used
to identify alternate positions that a part my take up. In this example we are using Phantom lines to show that the door handle may only move 45 degrees from it’s horizontal position. How many lines from the previous 2 slides can you identify here?

26 PROJECTIONS Pictorial Isometric Oblique Caviler Cabinet Perspective
Orothographic

27 Pictorial Pictorial sketches are sketches that show height, width, and depth all in one view. There are three common types: Isometric Oblique Perspective

28 are drawn at 30 degrees from
Isometric Note one view shows height width and depth. Width and depth lines are drawn at 30 degrees from the horizon line.

29 Oblique Front view is true size and shape. Width lines are
parallel with the horizon. In Cavalier Oblique depth is full size. This cube has the same height, width and depth dimensions Depth in an oblique pictorial is distorted. Easiest of the pictorials to draw. Depth lines are drawn at an angle with the horizon.

30 Oblique Width lines are parallel with the horizon.
Front view is true size and shape. Width lines are parallel with the horizon. In Cabinet Oblique depth is half size. This allows the view to look more realistic.

31 Perspective Perspective is a way to draw that shows a view of the object in the most realistic way. Vanishing points are used to guide the lines in the object to the horizon line or the horizontal line you see at your line of sight. We will discuss one and two point perspective.

32 One Point Perspective All lines in the depth project
to one point (vanishing point). The location of the vanishing point is based on your line of sight. Note: The vanishing point in this sample is chosen for demonstration.

33 Two Point Perspective In two point perspective
the depth lines converge on one vanishing point (VP2) and the width lines converge on the other vanishing point (VP1).

34 Shading Shading allows us to create a more realistic image by showing how light reflects on the object. We use shading in engineering graphics to show features not easily seen otherwise. There are two main types of shading: Straight Line Stippling

35 Shading (Straight Line)

36 Shading (Stipple Shading)

37 Orthographic (Multiview Drawings)
Pictorial sketches are great for engineers to explain ideas and communicate what the final part will look like to the customer. Unfortunately, pictorial drawings have some disadvantages. Foreshortened views and distorted features do not allow for accurate prototyping. Many times, for parts to be accurately depicted, you need straight on views of each surface.

38 Orthographic (Multiview Drawings)
Sketching Principles of EngineeringTM Unit 2 - Lesson 2.1 – Sketching Orthographic (Multiview Drawings) In order to obtain these straight line views we have a type of drawing called Orthographic Projection also known as Multiview drawings. Orthographic projection is a way to project a view based on a line of sight that is perpendicular to that view. There are six of these views to any object as shown in the next slide. A pictorial drawing or a photograph shows an object as it appears to the observer, but not as it is. Such a picture cannot describe the object fully, no matter from which direction it is viewed, because it does not show the exact shapes and sizes of the several parts. In industry, a complete and clear description of the shape and size of an object to be made is necessary in order to make certain that the object will be manufactured exactly as intended by the designer. In order to provide this information clearly and accurately, a number of views, systematically arranged, are used. This system of views is called multi-view projection. Each view provides certain definite information if the view is taken in a direction perpendicular to a principal face or side of the object. For example, an observer looking perpendicularly toward one face of the object obtains a true view of the shape and size of that side. This view as seen by the observer is shown at (b). (The observer is theoretically at an infinite distance from the object.) An object has three principal dimensions: width, height, and depth, as shown at (a). In technical drawing, these fixed terms are used for dimensions taken in these directions, regardless of the shape of the object. The terms "length" and "thickness" are not used because they cannot be applied in all cases. Note at (b) that the front view shows only the height and width of the object and not the depth. In fact, any one view of a three-dimensional object can show only two dimensions; the third dimension will be found in an adjacent view. Project Lead The Way, Inc. Copyright 2007

39 Orthographic (Multiview Drawings)
The arrows represent the line of sight associated with each view. Use the button below to jump between this view and the ortho view on the next page. ORTHO

40 Orthographic Principal Views
Sketching Principles of EngineeringTM Unit 2 - Lesson 2.1 – Sketching Orthographic Principal Views Note how the views are oriented. Each view is adjacent to the other as if they were unfolded from a 3D shape. Revolving the Object To obtain additional views, revolve the object. First, hold the object in the front-view position. To get the top view (b), revolve the object so as to bring the top of the object up and toward you. To get the right-side view revolve the object so as to bring the right side to the right and toward you. To obtain views of any of the other sides, merely turn the object so as to bring those sides toward you. The top, front, and right-side views, arranged closer together. These are called the three regular views because they are the views most frequently used. An important advantage that a view has over a photograph of an object is that hidden features can be clearly shown by means of hidden lines. The Six Views Any object can be viewed from six mutually perpendicular directions. Thus, six views may be drawn if necessary. These six views are always arranged as shown, which is the American National Standard arrangement of views. The top, front, and bottom views line up vertically, whereas the rear, left-side, front, and right-side views line up horizontally. To draw a view out of place is a serious error, generally regarded as one of the worst mistakes one can make in this subject. Choice of Views A drawing for use in production should contain only those views needed for a clear and complete shape description of the object. These minimum required views are referred to as the necessary views. In selecting views, the drafter should choose those that show best the essential contours or shapes and should give preference to those with the least number of hidden lines. Front, Top and Right views are used most often. You can see how other views resemble these three except they are not as clear due to hidden lines. Click to go back to ISO view. ISO Project Lead The Way, Inc. Copyright 2007

41 Orthographic Angle of Projection
The example you have just seen is shown in the third angle of projection. This is the standard in the United States and Canada. The rest of the world draws in the first angle of projection. The following slides will show how the views are derived and what they look like.

42 Orthographic Spacial Quadrants and Planes
In 3rd angle projection, the projection planes used to create views are as shown in red. Top Front Right Side This sketch shows the quadrants where the angles of projection are made from

43 Orthographic 3rd Angle Projection
Views are projected onto planes that exist on the face of that view. Arrows show the direction of the projection ISO Symbol Back

44 Orthographic Spacial Quadrants and Planes
In 1st angle projection the projection planes used to create the views are as shown in red. Top Front Side

45 Orthographic 1st Angle Projection
Views are projected onto planes that exist on the opposite face of the view you want to display. The arrows show the direction of the projection. ISO Symbol Back

46 Orthographic View Selection
Sketching Principles of EngineeringTM Unit 2 - Lesson 2.1 – Sketching Orthographic View Selection Finding the best view of a part can be difficult. Two or more sides may look like the best solution for a front view. On the next slide is a list of characteristics that you should use in choosing your views. Project Lead The Way, Inc. Copyright 2007

47 Orthographic View Selection
Steps in selecting the front. Most natural position or use. Shows best shape and characteristic contours. Longest dimensions. Fewest hidden lines. Most stable and natural position. Relationship of other views Most contours. Longest side. Least hidden lines. Best natural position.

48 Orthographic View Selection
Most natural position. Longest Dimension Best shape description. No hidden lines.

49 Orthographic View Selection Numbers
Sketching Principles of EngineeringTM Unit 2 - Lesson 2.1 – Sketching Orthographic View Selection Numbers Another decision on view selection you need to make is how many views. You usually do not need more than three but you may only need one or two. The following slides will show when to make a decision between one, and two view drawings. The question often arises: What are the absolute minimum views required? For example, the top view might be omitted, leaving only the front and right-side views. However, it is more difficult to "read" the two views or visualize the object, because the characteristic "Z" shape of the top view is omitted. In addition, one must assume that corners A and B (top view) are square and not filleted. In this example, all three views are necessary. If the object requires only two views, and the left-side and rightside views are equally descriptive, the right-side view is customarily chosen. If contour A were omitted, then the presence of slot B would make it necessary to choose the left-side view in preference to the right-side view. Project Lead The Way, Inc. Copyright 2007

50 One View Selection Two views will be identical Uniform shape.
All dimensions easily shown on one view.

51 One View Selection It is also possible to have one view drawings
of objects that are flat and have even thickness. Gauges and gaskets are two such objects. We have a gauge here on the left.

52 Two View Selection Symmetrical parts. A third view
would be identical to the other views Second view is necessary for depth.

53 Precedence of Lines In multiple view drawings, many times different line types will take up the same space, therefore, we have line precedence. The following is an explanation of which lines exist over others. Object lines over hidden and center. Hidden over center. Cutting plane lines over center lines. The following slide will show an example.

54 Precedence of Lines An object line here takes precedence
over the center line. However we draw short thin lines beyond the object to show there is a center line underneath the object line. Object lines took precedence over the hidden lines you would see from the hole. The center line in the top view would show the depth of the hole as well as the right side view.

55 References Project Lead the Way. Madsen, David A., Shumaker, Terence M., Stark, Catherine, Turpin, J. Lee, Engineering Drawing and Design Second Edition,Delmar Publishers, 1996, ISBN Brown, David, You Can Draw,North Light Books, Cincinnati, Ohio, 1986, ISBN Olivo, Dr. C. Thomas, Olivo, Thomas P., Basic Blueprint Reading and Sketching Sixth Edition, Delmar Publishers Inc., 1993, ISBN

56 References Johnson, Cindy M., Lockhart, Shawna D., Engineering Design Communication, Prentice Hall, 2000, ISBN Spencer, Henry Cecil, Dygdon, John Thomas, Novak, James E; Basic Technical Drawing 6th Edition; Glencoe McGraw Hill; New York, New York,1995, ISBN

57 Do you want to be a good sketcher?
Practice First Slide


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