1. TA 101: Technical Arts 2015-16 II Dr. Prishati Raychowdhury
Department of Civil Engineering
IIT Kanpur
Office: FB 336; Phone: 6692

2. Lecture 7
Isometric Projection

3. Notice regarding AutoCAD
Practice sessions are scheduled on Feb 5th, 6th, 12th, and 13th
AutoCAD laboratory session (LA#7) is scheduled during Feb 22-25th (the week after mid sem)
February 2016
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday 1
LECTURE PM (L7) 3
LECTURE PM (L7) 5
AutoCAD Practice (6-8 pm)
6 AutoCAD Practice (6-8 pm) 7 8
LECTURE PM (L7) 10
LECTURE PM (L7)
12 AutoCAD Practice (6-8 pm)
13 AutoCAD Practice (6-8 pm) 14 15
MID SEM 16 17 18 19 20 21 22
LECTURE PM (L7) 24
LECTURE PM (L7) 26 27 28
AutoCAD LAB: LA#7 (10 am-1 pm)

4. AutoCAD Schedule Practice session SL. No. Section Date Time Venue 1 B1
Feb 5, Friday
6-8 pm
IME autoCAD lab 2 B2 3 B3
Northern Lab 4 B4
Feb 6, Saturday 5 B5 6 B6 7 B7
Feb 12, Friday 8 B8 9 B9 10
B10
Feb 13, Saturday 11
B11 12
B12

5. Notice regarding AutoCAD
AutoCAD labs in NEW CORE LAB are open to all everyday from 8:00 am to 11:00 pm
You are encouraged to go there and practice as per your convenience
You will be given a handout for ready reference to the basic commands of autoCAD
You are requested to go through the document and get familiar with the software
We will spend a couple of lectures to learn about autoCAD

6. AutoCAD Schedule AutoCAD Laboratory Session (LA#7) SL. No. Section Day
Date
Time
Venue 1 B1
Tue
23/02/2016
10 am – 1 pm
IME autoCAD lab 2 B2 3 B3
Northern Lab 4 B4
Mon
22/02/2016 5 B5 6 B6 7 B7
Wed
24/02/2016 8 B8 9 B9 10
B10
Thu
25/02/2016 11
B11 12
B12

7. Review: Axonometric Projection
100 80 20 25 60 50 40 12 x y z x y z
Orthographic Projection
Axonometric Projection
Multiple views required
Shape and size unchanged
Object not rotated, no foreshortening
Better for manufacturing and detailing, not preferred for visualization
Only one view is required; 3 faces are visible in one view
Object rotated twice
Shape distorted
Size foreshortened
Not good for manufacturing, but preferred for visualization

8. Review: Isometric Projection
Equal foreshortening of three mutually perpendicular sides
Foreshortening is about 82%
Obtained by rotating the object 45o about vertical axis and forward tilting it by 35°16’

9. Isometric Projection vs. Isometric View1
0.82 ? ?
0.82
Isometric Projection ?
0.82
Isometric Projection of A
Cube A
Isometric Drawing/View/Sketch
Enlarge by times
1.225
1.0 ? ?
1.0
Isometric Projection ?
1.0
Isometric Projection of B
(Isometric Drawing/View of A)
Cube B

10. Review: Isometric Scale
Isometric Projections:
Isometric lines drawn using isometric scale
Foreshortened (82% of actual length)
Isometric Drawing/View:
Isometric lines drawn using 1:1 scale
No foreshortening, take actual lengths

11. Isometric Projection Basics
Isometric Lines
Isometric planes
120
Isometric Box
30
Isometric Axes

12. Isometric Projection Basics
In an isometric projection (or drawing), distances to be measured only along isometric lines parallel to any of the isometric axes
Any line that does not run parallel to an isometric axis is called a non-isometric line
Non-isometric lines include inclined and oblique lines that cannot be measured directly. They must be created by locating two end points on isometric planes

13. Constructing Isometric Views
Isometric axes can be positioned in a number of ways to create different views of the same object
Regular Isometric
Axes at 30° to horizontal drawn upward from horizontal (Commonly used method)
Reversed Isometric
Axes at 30° to horizontal drawn downward from horizontal

14. Methods for Constructing Isometric Views
Box Method:
Box method is used when the non-isometric lines or their ends lie in isometric planes
The object is assumed to be enclosed in a rectangular box
The ends of the lines for the inclined edges are then located by measuring on or from the outlines of the box
Coordinate or Offset Method:
This method is adopted for objects in which neither non-isometric lines nor their ends lie in isometric planes
Perpendiculars are dropped from each end of the edge to a horizontal or a vertical reference plane

15. Example: Box Envelope Method

16. Example: Without box

17. Another Example 20 40 30 45 10

18. Another Example 20 40 30 45 10

19. Isometric View

20. Procedure: Isometric Projection
Choose the origin as the starting point (does not have to be a point on the object)
Draw the isometric axes from the origin
Draw an isometric box corresponding to the maximum object dimensions
All object edges parallel to the three principal axes are also parallel to the corresponding isometric axes. These object edges are called isometric lines
All the object planes parallel to the three principal planes are called isometric planes
Draw the isometric edges & planes first, locate ‘key points’ in isometric drawing, and then draw non-isometric object lines & planes using the ‘key points’
Hidden lines are generally not drawn

21. Isometric Projection Notes
All isometric lines are foreshortened equally (82%)
All non-isometric lines may or may not foreshorten and foreshortening ratio of such lines may vary disproportionately
Projections of parallel lines will be parallel in isometric view
All measurements can only be marked along isometric lines
Measurement cannot be made on non-isometric lines
Angles specified in degrees do not appear in their true size on isometric drawing
Angles must be laid off with coordinates which are parallel to isometric axes

22. Difference with Orthographic Views
Hidden Lines
Omitted in isometric projections (or drawings) unless absolutely necessary to completely describe the object
Most isometric projections (or drawings) do not have hidden lines

23. Circles and Center Lines
Circles will become ellipse in isometric
Draw ellipse using the four-centre method
Center Lines
Drawn only for showing symmetry or dimensioning
Often not shown when communicating with non-technical people and not for engineering purposes

24. Dimension Lines
Dimension lines, extension lines and lines being dimensioned lie in the same plane
All dimensions and notes to be located outside the view whenever possible

25. Circles in Isometric View
Orthographic View
Isometric View

26. Non-Isometric Lines in Isometric View
Inclined Line F E C E F D C H B D G I B G H A
Isometric Line A I
Orthographic View
Isometric View

27. Angles in Isometric Viewsb
900
900
600 c
600 b
300 a
900
1200
1200 c
600

28. Thank you..