Engineering H191 Engineering Fundamentals And Laboratory I

First-Year Engineering Program

Engineering H191 Engineering Fundamentals and Laboratory I Week 02 Day 02 Projection Systems: Orthographic and Isometric

First-Year Engineering Program

Objectives • • • • • • •

Orthographic Projections View Selection Glass Box Approach First and Third Angle Projections Line Precedence Two View Drawings Tips

AU 2005

2

First-Year Engineering Program

Orthographic Projections • Reference: Technical Graphics, Chap 3: • Advantage – Represent features of an object more accurately • Example Problem

AU 2005

3

First-Year Engineering Program

Orthographic Projections

• Orthographic Projections are a collection of 2-D drawings that work together to give an accurate overall representation of an object. AU 2005

4

First-Year Engineering Program

Defining the Six Principal Views or Orthographic Views

AU 2005

5

First-Year Engineering Program

Which Views to Present? General Guidelines • Pick a Front View that is most descriptive of object • Normally the longest dimension is chosen as the width (or depth) • Most common combination of views is to use: – Front, Top, and Side View • Any other view different from the Principal Views is called an Auxiliary View (see 3.15 in the Technical Graphics text)

AU 2005

6

First-Year Engineering Program

AU 2005

7

First-Year Engineering Program

Glass Box Approach • Most powerful technique to understand orthographic projections • Suspend the object with transparent strings inside a glass box • Freeze the view from each direction (each of the six sides of the box) and unfold the box • Animation illustrates glass-box approach AU 2005

8

First-Year Engineering Program

Glass Box Approach • Available on the FEH website: • http://feh.eng.ohio-state.edu – Lecture Notes – Engineering H191 – Autumn 2005 – Glass Box Animation

AU 2005

9

First-Year Engineering Program

Glass Box Approach

AU 2005

10

First-Year Engineering Program

Glass Box Approach

AU 2005

11

First-Year Engineering Program

Glass Box Approach

AU 2005

12

First-Year Engineering Program

Glass Box Approach

AU 2005

13

First-Year Engineering Program

Glass Box Approach

AU 2005

14

First-Year Engineering Program

Glass Box Approach

AU 2005

15

First-Year Engineering Program

First and Third Angle Projections

Third-angle Projection

First-angle Projection

AU 2005

• •

First Angle – International Third Angle – U.S.

16

First-Year Engineering Program

Conventional Orthographic Views Width

Top View

Front View

AU 2005

Depth

Right Side View

Height 17

First-Year Engineering Program

Is The Orthographic View OK?

AU 2005

18

First-Year Engineering Program

Orthographic Must Be In Projection

AU 2005

19

First-Year Engineering Program

Hidden and Center Lines •

Hidden Line – used to represent features that cannot be seen in the current view

•

Centerlines – used to represent symmetry and to mark the center of circles and the axes of cylinders, and the axes of symmetrical parts, such as cylinders and bolts

AU 2005

20

First-Year Engineering Program

For Example:

1. Visible 2. Hidden 3. Center AU 2005

21

First-Year Engineering Program

Precedence of Lines • Visible lines takes precedence over all other lines 0.6 mm • Hidden lines and cutting plane lines take precedence over center lines 0.3 mm • Center lines have lowest precedence 0.6 mm AU 2005

22

Example:

First-Year Engineering Program

Application of Precedence

AU 2005

23

First-Year Engineering Program

Intersecting Lines in Orthographic Projections Solid Line Intersections

Dashed Line Intersections

Gap Reference – Technical Graphics, Chapter 3 AU 2005

24

First-Year Engineering Program

Two-View Drawings • Some objects can be fully described by two views, look for: – Symmetry or Bodies of Rotation

Front View AU 2005

Right Side View

Front View

Right 25Side

First-Year Engineering Program

Other Two-View Examples

AU 2005

26

First-Year Engineering Program

Summary • Introduced to orthographic projections

• We recommend the software animation exercise introduced in class. Animation can be found on Carmen – Glass Box Theory.

AU 2005

27

First-Year Engineering Program

Review Questions •

Rectilinear grids are used for sketching isometric pictorials … True/False

•

Based on the lines of sight, orthographic projection drawings are classified as ___________ projections

•

There are ____ standard principal views of orthographic projections

•

Each view in an orthographic projection concentrates on ____ dimensions of the object

AU 2005

28

First-Year Engineering Program

Hints for Orthographic Projection Sketching • Identify the major features and overall dimensions of the object • Do not use any straight-edge devices as a pencil guide when sketching by hand • Start by drawing bounding boxes with light construction lines. • Keep views aligned while sketching

AU 2005

29

First-Year Engineering Program

Hints for Orthographic Projection Sketching • Title Information is required – follow conventions • Usage of construction lines is encouraged. – Mandatory for circle or ellipse • Orthographic projection: – Alignment of the views is important! – Will not be graded, if not aligned

AU 2005

30

First-Year Engineering Program

Hints for Orthographic Projection Sketching • Map inclined and oblique faces to all three views • Follow the precedence of lines • Darken all visible, hidden, and center lines

AU 2005

31

First-Year Engineering Program

Sketching a Circle • Draw a square whose sides are the diameter of the circle. • At the center of each side define the point of tangency for the circle. • Draw the diagonals of the square. • Orient the paper so you can draw equal arcs to construct the circle AU 2005

32

First-Year Engineering Program

Today's Assignment • A11 • TG 2.7 and 2.18

AU 2005

33