Chapter 2 & 3 Orthographic Projection
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Outline
Principle views Orthographic projection Line types Layers
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The Six Principle Views
The 6 principle views are created by looking at the object, straight on, in the directions indicated.
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Introduction
An orthographic projection represents different sides of an object. 2-D representation of a 3-D object.
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Views of Surfaces
A plane surface that is perpendicular to a plane of projection appears on edge as a straight line
A plane surface that is parallel to a plane of projection appears as rectangle at true size
If a plane is angled to the plane of projection, it appears foreshortened 2 to 3 in projected plane is not equal to 2 to 3 measured on object
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When is something hidden
When an edge is not visible from that view This edge is shown as
hidden line in the right view
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Glass Box Method
The object is placed in a glass box. The sides of the box represent the 6 principle planes.
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Glass Box Method
The image of the object is projected on the sides of the box.
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Glass Box Method
Things to notice!
The projection planes. The projectors. How surfaces A and B are projected.
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Glass Box Method
The box is unfolded creating the 6 principle views.
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Exercise 2-1
Label the 5 remaining principle views with the appropriate view name.
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Name each view. Top
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Name each view.
Top
Right Side
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Name each view.
Top
Right Side
Rear
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Name each view.
Top
Left Side
Right Side
Rear
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Name each view.
Top
Left Side
Right Side
Rear
Bottom
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What are the differences between the Right Side and Left Side views?
Top
Left Side
Right Side
Rear
They are mirror images with one different line type.
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Bottom
What are the differences between the Top and Bottom, and Front and Rear views?
Top
Left Side
Right Side
Rear
Bottom
They are mirror images with different line types.
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Which view(s) have the least amount of hidden or dashed lines?
Top
Front and top views.
Left Side
Right Side
Rear
Bottom
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Standard Views
The standard views used in an orthographic projection are;
Front view Top view Right side view
The remaining 3 views usually dont add any new information.
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Standard Views
When constructing an orthographic projection, we need to include enough views to completely describe the true shape of the part.
Complex part = more views Simple part = less views
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Front View
The front view shows the most features or characteristics of the object.
It usually contains the least amount of hidden lines. The front view is chosen first and the other views are based on the orientation of the front view.
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Line Type and Weight
Line type and line weight provide valuable information to the print reader. For example, line type and weight can answer the following questions.
Is the feature visible or hidden from view? Is the line part of the object or part of a dimension? Is the line indicating symmetry?
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Line Type and Weight
There are four commonly used line types;
continuous hidden center phantom
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Line Type and Weight
Some lines are more important than others. Importance is indicated by line weight or thickness.
The thicker the line, the more important it is.
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Line Types
Visible lines:
Visible lines represent visible edges and boundaries. Continuous and thick (0.5 - 0.6 mm).
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Line Types
Hidden lines:
Hidden lines represent edges and boundaries that cannot be seen. Dashed and medium thick (0.35 - 0.45 mm).
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Line Types
Center lines:
Represent axes of symmetry. Long dash short dash and thin (0.3 mm).
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Line Precedence
If two lines occur in the same place, the line that is considered to be the least important is omitted. Lines in order of precedence/importance are as follows;
Cutting plane line (next week in Sections) Visible line Hidden line Centerline
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Exercise 2-3
Fill the following dotted orthographic projection with the appropriate line types.
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Fill in the visible lines in to top view.
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Fill in the visible lines in to front view.
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Fill in the visible lines in to right side view.
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Fill in the hidden lines in to front, top and right side views.
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View Alignment
The top and front views are aligned vertically and share the same width dimension. The front and right side views are aligned horizontally and share the same height dimension.
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45 deg
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Intersections and Tangencies
a)
b)
Where a curved surface is tangent to a plane surface, no line is drawn When a curved surface intersects a plane surface, an edge is formed
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Intersections and Tangencies
a) b)
A plane surface can intersect or be tangent to a contoured surface When a plane intersects a contoured surface, a line is drawn to represent that edge When a plane surface is tangent to a contoured surface, no line or a thin phantom line is drawn
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Standard Views
How many views do we need to completely describe a sphere?
1 view. A sphere has only one dimension. Its diameter.
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Creating an Orthographic Projection
Choose a front view.
Which view shows the most about the object without any hidden lines?
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Creating an Orthographic Projection
Decide how many views are needed.
How many and which views? 2 Front Top
For procedural reasons, we will continue this example by drawing all 3 standard views.
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Creating an Orthographic Projection
Draw the visible features of the front view.
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Creating an Orthographic Projection
Draw projectors off of the front view.
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Creating an Orthographic Projection
Draw the top view.
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Creating an Orthographic Projection
Project back to the front view.
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Creating an Orthographic Projection
Draw a 45 projector off the front view.
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Creating an Orthographic Projection
Draw projectors over to the 45 line and down.
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Creating an Orthographic Projection
Draw the right side view.
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Creating an Orthographic Projection
Project back if needed.
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Creating an Orthographic Projection
Draw centerlines where necessary.
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Creating an Orthographic Projection
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Completed Drawing
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Exercise 2-4
Fill in the missing lines in the front, right side, and top views.
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1 missing visible line in the front view.
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The right side view has 1 missing visible line and 2 missing hidden lines.
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The top view has 5 missing visible lines and 2 missing hidden lines.
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Exercise 2-5
Fill in the missing lines in the top, front, and right side views.
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The top view has 1 missing visible line. Do you see an error?
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The front view has 4 missing visible lines and 4 missing center lines.
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The right side view has 2 missing hidden lines and 1 missing center line.
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As noted in lecture, these hidden lines should not extend through the entire depth of the object since the large circle only is through the top 1/2
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Exercise 2-8
Shade in the surfaces that will appear in the front, top, and right side views. Estimating the distances, draw the front, top, and right side views. Identify the surfaces with the appropriate letter in the orthographic projection.
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1) Shade in the surfaces of the front view. 2) Draw the front view. 3) Identify the surfaces.
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1) Shade in the surfaces of the right side view. 2) Draw the right side view. 3) Identify the surfaces. Notice the horizontal and vertical projectors.
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1) Shade in the surfaces of the top view. 2) Draw the top view. 3) Identify the surfaces. Notice the 45 deg. projector
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Creating Hidden Lines
Rule 1:
The length of the hidden line dashes may vary slightly as the size of the drawing changes.
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Creating Hidden Lines
Rule 2:
Hidden lines should always begin and end with a dash, Exception: When the hidden line begins or ends at a parallel visible or hidden line.
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Creating Hidden Lines
Rule 3:
Dashes should join at corners.
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Using Center Lines
Center lines represent axes of symmetry.
They are important for interpreting cylindrical shapes.
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Using Center Lines
They are also used to indicate circle of centers, and paths of motion.
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Creating Center Lines
Rule 1:
Center lines should start and end with long dashes.
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Creating Center Lines
Rule 2:
Center lines should intersect by crossing either the long dashes or the short dashes.
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Creating Center Lines
Rule 3:
Center lines should extend a short distance beyond the object or feature.
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Creating Center Lines
Rule 4:
Center lines may be connected within a single view to show that two or more features lie in the same plane. CAUTION! Center lines should not extend
through the space between views .
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Draw the center lines in all the views.
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NOTICE! The small dashes cross in the middle.
NOTICE! The center line connects between features in the same view.
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Using Phantom Lines
Phantom lines uses:
They may also be used to indicate adjacent positions of related parts.
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Using Phantom Lines
Phantom lines uses:
Used to indicate repeated detail.
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Using Phantom Lines
Phantom lines uses:
They are also used to show a change in surface direction produced by fillets and rounds.
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Using Phantom Lines
Phantom lines uses:
Used to indicate alternate positions of moving parts.
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Creating Phantom Lines
Rule 1:
Phantom lines should start and end with a long dash.
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Using Break Lines
Break lines are used to show imaginary breaks in an object.
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Creating Break Lines
There are two types of break lines.
If the distance to traverse is short the series of connecting arcs is used.
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Creating Break Lines
There are two types of break lines.
If the distance is long the thin straight line with a jog is used.
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Chapter 3
Orthographic Projections in AutoCAD
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Introduction
AutoCAD enables you to create different line types and to print using different line weights. Layers are like transparencies, one laid over the top of another.
Each layer contains its own line type. The line color controls the printed line thickness.
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Layers
Lets use layers to organize this drawing.
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The Layers Panel
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The Layer Properties Manager
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Line Type Scale
LTSCALE: Controls the size of the dashes and the spaces between dashes or dots.
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Properties
Properties
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These properties should be controlled through layer properties when possible.
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The Properties Toolbar
If these properties need to be changed, your first action should be to use layer properties.
This creates a much more organized drawing.
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Printing using Pen Widths
Object color is used to control the print thickness of the object.
Access the Page Setup window to assign thickness to the different colors.
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Prints each color black Edit pen thickness
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Choose a color Assign a line weight
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Title Blocks
Every engineering drawing should have both a border and a title block.
Border - defines the drawing area Title block - gives pertinent information
The information that is included depends on the drawing type, field of engineering, and viewing audience.
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Title Block
A title block may include:
Name of drafter Checked by School or Company Drawing title Part name Part number Material of part Number of required parts Sheet number Number of sheets Scale of drawing Date Last revision
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Model and Layout Space
Model Space:
In model space, you draw your design/model at a 1:1 scale.
Layout/Paper Space:
The model is scaled to fit on the paper used to print the drawing (usually 8.5 x 11).
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Model and Layout Space
Viewports:
A viewport is a rectangular window that views the object from a specified line of sight. Layouts can have multiple viewports and different scales/etc.
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Model and Layout Space
Model Space:
Annotations (dimension, text) may be included on 2-D drawings and one view 3-D drawings.
Layout/Paper Space:
Annotations may be included in any view port.
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Model and Layout Space
Model Space:
Annotations will not scale automatically.
Layout/Paper Space:
Annotations will scale automatically if the object is defined as annotative.
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