elec 106 fundamentals of electrical engineering engineering drawing
TRANSCRIPT
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