ELEC 106

FUNDAMENTALS OF ELECTRICAL ENGINEERING

Engineering Drawing

Visualization and Graphics

Graphical communication skills essential for learning most of the concepts in all engineering disciplines

Visualize information and translate it into visual products such as sketches and drawings

Represent a three-dimensional object in a two-dimensional medium

The prevalence of computers intensifies the need for visualization and graphical communication skills

The Theory of Projection

Four specific components: 1) an object 2) an observer 3) a projection plane or picture plane 4) visual rays (lines of sight)The projection plane placed between the

object and the observerVisual rays passing through the plane from

the object to the observer creating a two-dimensional image of the object on the plane

The Theory of Projection

Central perspective: - the size of the image a bit smaller than the true size of the object - due to a finite distance between the observer and the objectOrthographic projection: - the image on the picture plane same size as the object - the visual rays parallel to each other and perpendicular to the picture plane

Central Perspective

Orthographic Projection

Orthographic Projection

Fundamental principle upon which all engineering drawing is based

The “glass box theory”The basis of how a three-dimensional object

can be represented by its two-dimensional orthographic views: top view, front view, side view

Top view: the width and depthFront view: the width and heightSide view: the height and depth

The Glass Box Theory

Orthographic Multi-Views

The Meaning of Lines: Visible Lines

Solid lines (0.7 mm thick) drawn to represent - the edge view of a surface - the intersection of two surfaces - the limiting element of a curved surfaceElements : infinite number of lines drawn

parallel to the axis of the cylinderThe limiting element : the last element that

one can see before the curve begins to turn back on itself

The Meaning of Lines

The Meaning of Lines

The Meaning of Lines

Hidden Lines & Centerlines

Hidden lines - dashed lines (0.5 mm thick) - show the details of the object that appear hidden (i.e., blocked from the observer’s view by the object) Centerlines - solid thin lines (0.35 mm thick) - circular feature - a cross hair with a small + - a small gap (about 1/16 in) place on each side of + with a longer line extending 1/8 in beyond the curve - axis of symmetry - a long line broken in the middle

The Meaning of Lines

Centerlines for Cylindrical Features and Radii

Line Precedence

Visible lines, hidden lines, and centerlines are all the same degree of darkness, but they vary with regard to their thickness.

Orthographic Multi-views

Orthographic Multi-views

Pictorial Sketching

Involves creating a view of the object in which all three dimensions shown

Helps with visualization, i.e., ability to formulate in our mind’s eye what the object looks like

Three types:

Axonometric (isometric) Oblique Perspective

Isometric SketchesQuickest & easiest to draw and most

commonly usedMost common orientation – the observer

looking down on the object (bird’s eye view)Isometric axes: two receding axes measured

30 from the horizontal reference plus a vertical axis

Isometric Grid Paper

Isometric Sketching Example

Sketching Example

Step 1: Generate ‘isometric prism’ to box in the entire object

Step 2: Locate points 1, 2, 3, 4 on the top surface. Then, draw a line connecting 1-2 and 3-4 to create the slot

Step 3: Sketch a vertical construction line through 1, 2, 3, 4. Then, measure 1.5 units down each construction line to locate points 5, 6, 7, 8 for the depth of the slot.

Step 4: Draw a line connecting 1-5, 5-6, 5-7, 3-7, 6-2, and 6-8 to complete the slot.

Step 5: Erase lines 1-3, 2-4, and part 0f 6-8.

Another Example

Another Example

Cylindrical Features in Isometric Sketch

Circle appear as ellipse whose orientation depends on which orthographic view (top, front, side)

How to create an ellipse on the top isometric surface

How to create an ellipse on the front isometric surface

How to create an ellipse on the Right-side isometric surface

Scales

Most technical drawings are drawn to some scale

Drawing scale = the ratio that the drawing has to the real world object or other drawing

Use of scale depends on the size of the drawing media

Common drawing scales used in engineering: full scale (1:1), half scale (1:2), quarter scale (1:4), and tenth scale (1:10)

Isometric Coordinate System

Used when sketching three-dimensional object ontwo-dimensional media without isometric grid