EF101 Analysis & Skills Module 1.3 Engineering Graphics Terminology and Conventions

EF101 Analysis & SkillsModule 1.3

Engineering GraphicsTerminology and Conventions

Reading Review

• Why are multi-view orthographic projections used?

• What is a disadvantage of multi-view orthographic projections?

• Which type of multi-view projection is used in the United States?

• Name the components that are typically part of a set of working drawings?

Reading Review

• What are construction lines?• What are two types of pictorial sketches

commonly used in freehand sketching?• Which type of 3D projection places the

principal face of an object parallel to the plane of the paper?

• What type of projection results in multiple views?

Design Process / Working Drawings

Sketch Types

Glass Box

Unfolding Glass Box

View Relationships

• Controls the placement of views• Depicted on drawings by the truncated cone symbol• Third Angle

• United States and Great Britain• Top view - above front view.• Right side - right of front view• Same as “Glass box” unfolding

• First Angle• Rest of world• Top view - below front view.• Right side - left of front view

• We will only use third-angle projections in EF101

Projection Types

What can a Line Represent?

• Parallel – appear true size in one view,and as an edge (line) in other views

• Inclined – appear distorted in two views, and as an edge in the view perpendicular to the surface

• Oblique – appear distorted in all three views

Orthographic ProjectionSurface Types

Hidden Lines

• Dashed lines, lighter (thinner) than object lines.

• Used in orthographic projection views to represent edges that are “hidden” from the line of sight for a view.

• Not used in isometric or oblique views.

Hidden Lines Example

CenterlinesLocate the center of circles and the axis of cylindrical features.

1. Object linesdark and thick

2. Hidden linesdark, dashed and thin

3. Centerlinesdark, “long–short–long”, thin

4. Construction linesvery thin and light

Line Types and Precedence

Coordinate System Placement

• Placement of a coordinate system is arbitrary, but once placed you must be consistent in its use.

• AutoCAD’s convention is that the XY plane of the coordinate system represents the view it calls the top view.

• We place a coordinate system on sketches to help us to get used to working with a consistent coordinate system.

Multi-view sketching

• Determine necessary views

• Plan layout, spacing, scale to fit paper

• Develop drawing: block in views, make sure width, height, depth are correct in all views

• Add features in each view.

• Check work

Sketch as an Orthographic

Projection

Isometric sketching

• Use paper in landscape mode• Determine orientation• Determine scale and location to fit object in the

center of the page• Sketch the bounding box• Work from faces and corners• Parallel lines are parallel.• “Connect the dots” i.e. connect known locations.

Sketch as an Isometric Projection