1. Engineering H191 Engineering Fundamentals and Laboratory I
Lecture 02
Graphics: The Language of Design
Objectives:
Autumn 2008

2. Objectives Understanding graphics as a communication tool
Technical sketching
Projections
Orthographic
Pictorial
Sketching hints
Lettering
Instructor:
Today’s objectives are:
Objectives:
Sketching and Isometric Pictorials - At the end of the session, students should be able to:
Infer that technical drawings are effective tools for communication of technical ideas
Differentiate between multi-view and isometric drawings
Develop isometric sketches of tangible objects on isometric grid sheet
This session briefly highlights materials in Chapter 1 of Bertoline and starts on Chapter 2 – Isometric Sketching and Multiview Drawings.
Just doing a brief overview of first two topics. They are expected to read material in Chapter 2 Sketching and Text to get more details. Will spend most of the time on Introduction to Projections in particular isometric projection.
Autumn 2008

3. How Would You Describe This?
In teams of two, describe using only words
How effective is this approach?
Instructor:
This is an in-class interactive exercise(active learning). Allow students about 5 minutes to discuss with partner and then ask random students to put in words their description. Then ask the class the question shown on the slide.
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4. Three Basic Types of Technical Drawings
Freehand sketches
Instrument drawings
Computer drawings and models
In this class we will focus primarily on Freehand Sketching and Computer Based drawing
CAD programs have replaced much of Instrument drawing process.
Technical sketches are how engineers “think” and communicate with each other. All the way from napkin session at lunch to formal computer based solid models and flow charts.
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5. Introduction to Projections
Present 3-D objects with 2-D media
Two Basic Categories
Orthographic Pictorial
Definitions:
Projection: the process or technique of reproducing a spatial (3-D) object upon a plane or curved (2-D) surface
Orthographic sketches present the object in a series of projections, each one showing only two of the object’s three dimensions.
Pictorial sketches present the object in a single view with all three dimensions represented
Discuss the trade-offs in using any type of projection; some are more realistic, some are easier to draw, and some are easier to interpret by non-technical people
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6. Projections: Four Basic Types
Axonometric
Oblique
Perspective
Orthographic Projections
Course emphasizes on multi-view (orthographic) and isometric (one type of axonometric pictorial) projections only
Multiview projections are a collection of 2-D views
Pictorials are 3-D
Pictorials
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7. Orthographic Projections
Collection of 2D drawings
Accurately represent object
Technical Graphics - Chapter 3
Instructional Objectives:
Represent a 3-D objects in 2-D using 3 principal views of an orthographic projection
Conclude that a dimension (Wd./Ht./Depth) is shared between two views of an orthographic projection
Develop orthographic sketches of simple isometric sketches on rectilinear grid sheet
Questions that are not answered by pictorial presentation:
Does the hole go all the way through the object?
Are there any feature like slots or holes on the back sides of the object?
orthographic projection drawings will answer these and other questions. Multi View drawing is one of the most commonly used graphics tool by Engineers.
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8. Orthographic Projection
By definition for each element of a orthographic projection drawing you only present 2 of the three dimensions. Think of it as an observer look at one face, what do they see.
Any orthographic projection drawing normally has three views… Front view, Top view and side view (Right or left side view)
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9. Defining the Six Principal Views or Orthographic Views
Although any face could be chosen to be the front, once front and two other face are selected all are determined. There are really SIX PRINICPAL VIEWS as defined in the diagram.
Generally do not need all six to fully describe the object. A conventional Engineering Drawing will normally have 2 to 3 views unless it required more views to describe the geometry/ profile.
We know which ones they are on the drawing, because we always present them in the same relationship to each other. I.e. Top above front, right to right of front, etc. This convention is called as the Third angle method.. The other method in which the views can be placed is the First angle method in which the Top view is below front view, Right side view is on left side of front view. For this class we will be following the Third angle convention.
These are often called orthographic projections – because the line of sight is perpendicular to the principal view
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10. Which Views to Present? General Guidelines
Pick a Front View that is most descriptive of object
Normally the longest dimension is chosen as the width (or depth)
Most common combination of views is to use: Front, Top, and Side View
Views other than the Principal Views are called Auxiliary Views (see section 3.15 in the Technical Graphics text)
Pick the views which will help in describing the object with highest clarity.
Explain what is an auxiliary view. Explain that they are drawn to show specific features that are not clear in the Principal views.
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11. Autumn 2008 The Idea is to have them take an object from the table.
Declare front. FRONT View is the MOST DESCRIPTIVE VIEW OF THE OBJECT. The view that gives MORE INFORMATION ABOUT THE OBJECT.
Rotate 90 degrees “up” to get top view.
Rotate Back.
Rotate 90 degrees clockwise to get right side.
This give three principal views commonly used.
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12. Conventional Orthographic Views
Height
Depth
Width
Front View
Top View
Right Side View
Note that the views are placed and aligned in the manner shown in the diagram. Remind the students that they have to follow the above convention for all their home work problems and exam problems.
It is very important to maintain the alignment and correct placement relative to each other.
Means line for top (and bottom) is straight across for both front view and right side view for example.
Same thing between front and top for sides.
Note : The following can be seen from the slide:
Top View and front view have the same width
Front View and Right / Left side view have the same height.
The depth of Top view is same as the width of right/ left side view.
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13. Hidden and Center Lines in Orthographic Projections
Object Lines – represent visible features for an object
Hidden Lines – represent features that cannot be seen in the current view
Note the graphical convention for hidden and centerlines.
Centerlines – represent symmetry and mark the center of circles, the axes of cylinders, and the axes of symmetrical parts, such as bolts
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14. For Example: 1. Visible 2. Hidden 3. Center
From Bertoline: Figure 2.38 / Pg 42
In engineering and technical drawing, it is important that hidden features be represented, so that the reader of the drawing can clearly understand the object.
Thus we need hidden lines to emphasize that those features exist and are hidden in that particular view.
We also need center lines to understand how the features defined in the 2D views translate into 3D.
NOTE: It must be emphasized that hidden lines and center lines are used only on Orthographic projection drawings, never on isometric drawings
Q: Do we need a convention for what line to show if two lines fall on top of each other?
A: Yes! Otherwise features which are more important (eg: visible lines) would be overridden by less important features (eg: hidden lines) and the resulting drawing would be interpreted inaccurately. The next slide shows the convention followed.
2. Hidden
3. Center
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15. Creating the Orthographic Projection Sketch
From Bertoline: Figure 2.45/ Pg 47
The next few slides show how to create a three view sketch. A detailed explanation of this procedure is given in the book. Please urge the students to go through this explanation.
Things to emphasize
The glass box approach. How the object projects itself on the front, top and right side face of the glass box.
The animation shows the glass box approach on a different object.
We also define front-view by width and height, not depth and height
Front View
Right Side View
Top View
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16. Step 1 – Lightly Block Three Views
Use very light lines for drawing in the construction lines
Instructor:
Construction lines are to be drawn lightly, gray vs. black, so that they will not reproduce on a Xerox machine and therefore do not have to be erased.
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17. Step 2 – Lightly Block Major Features
Holes
Arcs
Cutouts
Use very light lines for drawing in the construction lines
Instructor:
Major features include holes, arcs, cutouts, etc. Again, very light lines should be used for the construction lines.
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18. Step 3 – Refine and Locate Features in All Views
Use very light lines for drawing in the construction lines
Instructor:
This slide has darker than acceptable construction lines to allow the students to see the construction lines on an overhead projector in a large room. It should be emphasized that students are required to keep construction lines, MUCH lighter than the object lines.
In our classes the students will typically use the grid paper to determine consistent depths of features between front and side view, not the mitre line. However, the mitre line highlights the depth relationship.
Note that the miter line is an alternative to “counting and measuring” when going from right side to top view. It helps show the connection between the two views. The miter line is not required. If it is used the side and top views must be the same distance from the front view so that a 45 degree mitre line correctly maps the features.
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19. Use very light lines for drawing in the construction lines
Step 4 – Add Final Lines
Use very light lines for drawing in the construction lines
Instructor:
The construction lines on the students’ drawings will be light gray and if the final lines are added and then made darker, the three views should appear.
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20. Completed Sketch Instructor:
Again, the construction lines are left off visual for clarity. Students can leave construction lines if done lightly.
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21. Add Another View Sketch the left side view of the object
Compare your view with the others at your table
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22. Add Another View
Does yours look something like this?
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23. Lettering Notes Lettering Guidelines See Technical Graphics: Chapter 1
Lettering Styles
Shape of characters
Order of drawing strokes of character
Character Uniformity
Spacing
**** should these notes be changed? *****
Will not spend a lot of time on Chap 1, expect students to read and be familiar with material there.
Overview:
Lettering must be neat and readable – Should use all capital letters
Tools
Traditional hand sketching
Computer Aided Drawing (a large industry producing computer packages they may have heard of in H.S. AutoCad, ProEngineer, SolidWorks)
Media (how we record)
Paper – helpful to know about Standard Sizes (Table 1) and Title Blocks
Alphabet of lines - Use Figure 1.41 for examples of line types. Refer back to this when you have questions.
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24. Lettering – Vertical Gothic Font
Instructor:
Tell the students that this guide to doing good lettering is contained in Chapter 1 for their reference.
Tell them that they should use all caps for notes on drawings and the letters should be ~1/8 inch or 3 mm high. The reason for using all caps is that someone could reduce the size of their original drawing on the copy machine. The capital letters can be reduce by 50% and still be readable.
We expect good quality lettering and the lettering to be done in vertical gothic or inclined gothic font.
Please note that – The drawing assignments from Dwg 5 onwards need to have the title block details filled in by hand lettering. TA’s can take of points if it is not followed.
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25. Sketching Tips: General
Relax and draw in a direction comfortable to you
Mark end points of the lines to be sketched and draw between them
Draw long lines as a series of short ones
Use grid paper when available
Follow sketching and text conventions
Do NOT use a straight edge to draw lines!
We will be doing a lot of freehand sketching. T-square, triangles as they may have in H.S. drafting. Do expect neat and clear work. THIS TAKES GOOD TECHNIQUE AND PRACTICE.
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26. Sketching Tips: Construction Lines
Use construction lines
Begin by drawing bounding boxes with construction lines
Make construction lines much lighter and thinner than finished lines
Identify the major features and overall dimensions
Leave construction lines on the sketch
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27. Sketching Tips: Miscellaneous
Do not shade the drawing – this is not pencil sketching
Title information is required
Keep views aligned (very important)
Include centerlines on isometrics
Avoid labels on the sketch
Construct neat circles – change page orientation if needed
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28. Today's Assignment Drawing 1:
Blocks of each kind of which you will sketch will be handed out at each table.
Drawing 2:
Lettering assignment handed out in class.
An additional copy will be in your course packet from Uniprint
Cut out patterns and glue or tape together to make three dimensional solids for visualization practice
Autumn 2008