Lecture #1 EGR 110 – Engineering Graphics

1. Lecture #1 EGR 110 – Engineering Graphics Reading Assignment:Ch. A-D in Engineering Graphics Workbook, Series 1.2 or Series 2 Sketching Assignment:Sketching Assignment #1 Welcome to EGR 110 Engineering Graphics • Syllabus • Group project • Homework • Web page • Office hours • Reminder: Bring memory storage device (disk or flash drive) to each class

2. Lecture #1 EGR 110 – Engineering Graphics • Why does an Engineer need to learn Engineering graphics? • Engineers need to be able to communicate their ideas through drawings and to be able to “read” the drawings of others. • Engineering drawings are not art, but are technical presentations based on a well-defined graphic language (containing rules, symbols, standards, etc.) • Even though most Engineering drawings are created using CAD, the person creating the drawing must still know what rules to use. For example, a CAD program cannot determine the best view for showing a dimension or decide when to use visible lines or hidden lines. • A knowledge of CAD is one of the earliest marketable skills that an Engineering student might possess. Many Engineering students gain valuable experience working with CAD. • Many Engineers use CAD routinely. • Many Engineers will form sketches of drawings and then have CAD operators produce the drawings. However, the sketches must be technically accurate. For example, it would be unreasonable to expect a CAD operator to know how you wish to layout, dimension, annotate, or section a drawing.

3. Lecture #1 EGR 110 – Engineering Graphics • Drawings may be: • Freehand sketches • Mechanical drawings (a rapidly vanishing area) • Computer-Aided Drawings (CAD) • Additionally, CAD drawings may be: • 2D Drawings • 3D Solid Modeling • 3D Parametric Solid Modeling (a more design-oriented approach) Drafting standards There are precise rules for graphical communication. For example, a standard symbol is used to represent a counterbored hole. A key standard is the American National Standard Drafting Manual – Y14. An engineer needs to be familiar with drafting standards in order to communicate effectively. The textbooks used in this course will introduce the student to important drafting standards.

4. Lecture #1 EGR 110 – Engineering Graphics • Sketching • Sketching is perhaps better referred to as freehand drawing. Sketching used by Engineers does not normally refer to artistic renderings such as in creating a portrait. • Instead, sketching simply means freehand drawing without instruments. • Sketches should not be crude, sloppy, or unclear. • Sketches should: • Be clear • Be reasonably proportioned (often to scale using graph paper) • Use proper line widths and types • Follow drafting standards and conventions • Graphpaper is commonly used for sketching. A drawing is easily kept in proportion using graphpaper and is easily drawn to scale.

5. The circle is drawn tangent to the midpoints of the box “Enclosing box” Graph paper Lecture #1 EGR 110 – Engineering Graphics “Enclosing Box” method Mechanical drawings often contain circles, holes, arcs, and ellipses. The “enclosing box” method is commonly used to drawing these features. This is especially useful when using graph paper.

6. Lecture #1 EGR 110 – Engineering Graphics • Examples: Show other examples using an “Enclosing Box”. • A fillet (rounded inside corner) • A semi-circular cutout • A triangular-shaped plate with rounded corners.

7. Lecture #1 EGR 110 – Engineering Graphics • Chapter C: Pictorial Sketches • Pictorial sketches are 2D drawings that give the impression of being 3D. • They are primarily intended for visualization. • They are often not scaled since the lengths of lines may be unscaled in order to give the proper 3D impression. • There are several types of pictorial sketches, including: • Isometric sketches - the most common and the type used in this course and in most engineering courses • Oblique sketches – Most commonly used for cabinet sketches • Perspective sketches - Most commonly used by artists Examples:Sketch a simple example of each type of pictorial.

8. O 30 O 30 Lecture #1 EGR 110 – Engineering Graphics • Isometric Sketching • Isometric sketches use "isometric axes" as shown below. • Isometric sketches are often formed using isometric graph paper (see below). • Note that lines that are parallel in the actual object will still be parallel. • We will begin sketching isometrics next week. • This week we will use given isometrics to sketch multi-view drawings. Isometric Axes Isometric Graph Paper

9. Lecture #1 EGR 110 – Engineering Graphics Chapter D: Orthographic Projection Orthographic projections, or multi-view drawings, are 2D drawings taken from viewpoints from various sides of an imaginary "plastic" box around the object. In orthographic drawings we assume that the "viewer" is at an infinite distance from the object and therefore the lines of projection are parallel. Illustration: The figures below illustrate the difference between a pictorial drawing (isometric) and an orthographic projection (multi-view drawing). Reference: Page D-2 in Engineering Graphics Text and Workbook, Series 1, by Craig & Craig.

10. Lecture #1 EGR 110 – Engineering Graphics The “Plastic Box” A view of an object from a certain direction can be illustrated by placing the object inside a plastic or glass box and then by imagining what the viewer would see on the side of the box from that direction. Illustration: The views of the object inside the plastic box are shown as they would be seen by a viewer at an infinite distance from the box. Reference: Page D-3 in Engineering Graphics Text and Workbook, Series 1, by Craig & Craig.

11. Lecture #1 EGR 110 – Engineering Graphics Illustration: The relationship between the 6 “standard views” can be seen by unfolding the box. For example, the right side view must always be shown to the right of the front view. Reference: Page D-4 in Engineering Graphics Text and Workbook, Series 1, by Craig & Craig.

12. Views Common Dimension Top, Front, Bottom, and Back Front, Left, Right, and Back Top, Left, Right, and Bottom Lecture #1 EGR 110 – Engineering Graphics Illustration: With the box completely unfolded, the relationship between the 6 standard views is clear. Certain views have certain dimensions (height - H, width - W, and depth - D). Fill out the table below. Reference: Page D-4 in Engineering Graphics Text and Workbook, Series 1, by Craig & Craig.

13. Lecture #1 EGR 110 – Engineering Graphics • Standard Layouts for Multi-View Drawings • All 6 standard views are not always needed in multi-view drawings. In general, the minimum number of views that will clearly describe an object are sufficient. To include more views would require additional work and would be redundant. Layouts for multi-view drawings usually consist of one of the following sets of views: • 6 view layout • 3 view layout (top, front, and right views) • 3 view layout (top, front, and left views) • 2 view layout (top and front) • 2 view layout (front and right) • 2 view layout (front and left)

14. 3 Views: Top, Front, and Right 6 Views 2 Views: Front and Left 2 Views: Front and Right 2 Views: Top and Front 3 Views: Top, Front, and Left Lecture #1 EGR 110 – Engineering Graphics Layouts Each layout must keep the views aligned as shown in the 6-view layout.

15. Lecture #1 EGR 110 – Engineering Graphics Linetypes Different types of lines are used to indicate various features or convey information related to the drawing. A complete list of linetypes is shown on page C-6 of the Engineering Graphics Workbook. The three most common line types will be introduced first: Visible lines - used for visible features (edges) on an object Example: Hidden lines - used to illustrate features that cannot be seen on the object Example: Center lines - used to show the centers of holes, arcs, and other features Example:

16. Lecture #1 EGR 110 – Engineering Graphics • Visible lines • Visible lines are solid, continuous lines. Example: • Visible lines can be used to show: • The intersection of 2 surfaces • The edge view of a surface • The contour view of a curved surface Example: Sketch example uses of visible lines.

17. Lecture #1 EGR 110 – Engineering Graphics Hidden lines Hidden lines are continuous dashed lines. Example: They are used to indicate various types of hidden features in objects. Good style should be used for hidden lines as illustrated below (complete in class): 1) When intersecting visible lines 2) When intersecting other hidden lines 3) On corners

18. Lecture #1 EGR 110 – Engineering Graphics Center lines Center lines have alternating short and long continuous, solid lines with long lines on the outside. Examples: Center lines are used to mark centers of holes and arcs, to show polar symmetry of features in an object, and to show circular paths for moving objects. Good style should be used for center lines as illustrated below (complete in class): 1) When to cross visible lines 2) Centerlines in half circles 3) Centerlines in bolt circles 4) Centerlines to indicate paths of motion

19. Lecture #1 EGR 110 – Engineering Graphics Precedence of lines Suppose that two or more types of lines coincide? Which is shown? The following precedence is used: 1) Visible lines (highest precedence) 2) Hidden lines 3) Center line (lowest precedence) Examples:

20. Lecture #1 EGR 110 – Engineering Graphics Examples: Sketch a 3-view layout (top, front, and left) for problem A1-3 in the text.

21. Lecture #1 EGR 110 – Engineering Graphics Examples: Sketch a 3-view layout (top, front, and left) for problem A3-4 in the text.

22. Lecture #1 EGR 110 – Engineering Graphics Examples: Sketch a 3-view layout (top, front, and left) for problem A4-2 in the text.