1. Reading Objects Lecture 8 Instructor:
Reading Objects means looking at 2D views and seeing 3D shape. It is also being able to identify the surfaces of 3D objects and how each surface would look in each of its 2D views. We will look at principal, inclined, and oblique planes.
Autumn Quarter

2. Topics For Today Missing lines and views problems
Reading partial drawings
Orthographic Views in Multiview Drawings
AutoCAD 2002 – 2D Lesson 5
Instructor:
3D visualization can be improved by working on missing line and missing view problems and by drawing the pictorial views of an object. We will finish the day by drawing orthographic views using AutoCAD.
Autumn Quarter

3. What a line can represent in a 3-D drawing
E Edge view of a plane surface, and/or
N Intersection of two surfaces, and/or
L Limiting element of a curved surface
Instructor:
When we look at 3D objects we see a series of lines and surfaces both on the pictorial and on the principal views. We can seethe lines as true length, foreshortened, and as a point. With surfaces we can see them true size, as inclined surfaces, or as oblique surfaces. One way of coding lines that we see in orthographic views is shown above. We will look at some examples in the next few slides.
Autumn Quarter

4. Sample E, N, and L’s E N L Instructor:
The hidden lines in the top and right side views are labeled ‘L’. These lines represent the limiting element of the hole that is drilled through the block. The lines labeled E in the front view are the edges of the vertical and horizontal surfaces. Where would we put the E’s in the top and right side views? In the top view, the N’s show the intersection between the bottom of the block and the inclined plane and the surface of the step and the inclined plane.
Autumn Quarter

5. Reading an Object Look for points Look for lines Look for planes
Identify these parts in multiple views and the isometric view.
Instructor:
When reading an object (looking at the pictorial and the orthographic views), it is important to look for points, lines and planes.
Autumn Quarter

6. Principal Planes - If a plane surface appears in true size in one view, it is parallel to the picture plane of that view and it will appear as an edge in adjacent views.
Instructor:
Here is a step block that has the lines labeled with two letters and each letter has a subscript F for front, R for right side, and T for top view. Each of the letters, for example A, label a point. A labels the lower left, front corner in the front view. A is shown first because A is on the front of the object and B is on the back surface. A and B label corners (points) on this object while AB labels a line.
The shaded surfaces shown in the top view on the left are the horizontal surfaces and they are true size. They appear as edges (lines) in the front and right side views. On the right side of this slide the front, vertical surface is shaded. It is shown true size and appears as an edge in the top and right side views.
Horizontal Surfaces – true size in top view
Vertical Surface – true size in front view
Autumn Quarter

7. Planes – Inclined - If a line represents the edge view of a plane surface in one view, that surface will appear as characteristic shape, but not characteristic size, in other views.
Instructor:
In this slide, we are dealing with inclined surfaces or planes. The same labeling scheme is used here as it was in the last slide. In both the left and right side, we see the inclined surface foreshortened (not true size). To the left, we see the inclined surface as an edge (red line) in the front view.
On the right, we see the inclined surface foreshortened in the top and front views and as an edge (red line) in the left side view.
Inclined surface – not true size in either view, true length in edge view.
Autumn Quarter

8. Oblique Planes - An oblique surface will not appear as an edge (line) in any view, but will have “characteristic” shape although not true size in all three views.
Instructor:
Oblique surfaces are always seen as their characteristic shape in the principal views. Auxiliary views would allow the plane to be seen as true size or as an edge. If you were working in CAD, most systems allow the user to indicate three points on a surface and the system rotates the figure so that you can see the oblique plane true size. When locating the corners in an isometric view, the measurements must be made along the axes.
Autumn Quarter

9. In Class Exercise
Given the Top and Front views shown here, how many right side views can you draw?
Instructor:
Have the students work individually, then in pairs to answer this question. Then ask who has the most true right side views.
Hint: Verify by sketching the isometric view
Autumn Quarter

10. Possible Solutions There are many more A B C Instructor:
The three solutions will come in when the mouse is clicked… then the text comes in on the next click.
Ask if the students think there are more solutions each time
Autumn Quarter

11. In Class Exercise Add the missing lines to complete the views
Instructor:
Here is another relatively simple missing line problem. Again, have them work singly and in pairs to solve the problem and then show them the answer.
Autumn Quarter

12. In Class Exercise – Solution
Instructor:
You may want to comment on the line ends… and the drawing conventions. The hidden lines won’t necessarily show up correctly according to the drawing conventions. The vertical hidden line should intersect the horizontal hidden line to show an upside down T. The ends of the horizontal line should intersect the edges of the view with a T turned sideways
Autumn Quarter

13. Today’s Assignment Dwg 15 – MV-1 Missing Views
Draw the missing view for each object
Due at end of class today
Dwg 16 – Lesson 5, Exercise 3 (page 5-28)
Draw 3-View Orthographic from Isometric
Due at beginning of next lecture
Instructor:
The first assignment is a missing view problem to be done as a sketching problem. Have them draw the isometric view as well. You may want to have them do this problem at home rather than in class. Drawing 16 is an exercise to be done on the CAD system where they are given the pictorial with dimensions and asked to do three views.
Autumn Quarter