Technical Illustration essentially is an art and a science of taking orthographic views and creating a three dimensional image.

Exploded isometric drawings help the viewer visualize how all of the parts of a particular model are assembled. Sketching and Drawing Isometrics in an Isometric grid assist the Draftsman in displaying how all of the parts fit together

A Draftsman not only makes the blueprint but their responsibilities also lie in being able to present the print so others can visualize what the model looks like.

Connecting Your Learning

As you work your way through this lesson, you should reflect on the following questions:

Why is an isometric grid used?
How are exploded drawings helpful in technical illustration?
How an ellipse can be used to view circles?
What is circle projection and how it is used to project lines of a hex bolt on an elliptical surface?

The State of Arizona has assembled Drafting standards to make sure that Instruction is thorough and well thought out by the instructor. By clicking on the hyperlink below will upload to your browser window the entirety of these standards. The standards that are addressed in this lesson are below the hyperlink.

1.0 USE BOARD DRAFTING EQUIPMENT, INSTRUMENTS AND MEDIA.

• 1.1 Analyze Drawing surfaces for Drafting
• 1.6 Demonstrate Sheet Setup skills

2.0 DEMONSTRATE SKETCHING, LETTERING, AND LINE SKILLS.

• 2.1 Demonstrate freehand sketching skills for drafting applications.
• 2.2 Demonstrate lettering skills.
• 2.3 Demonstrate line work.

6.0 DEMONSTRATE GEOMETRIC CONSTRUCTIONS

• 6.1 Measure Geometric Constructions.
• 6.2 Develop Geometric Constructions.

8.0 APPLY BOARD DRAFTING SKILLS TO COMPUTER-AIDED DESIGN/DRAFTING (CADD)

• 8.1 Demonstrate computer skills for a CADD system.
• 8.2 Create dimensional CADD entities.
• 8.3 Create 3 dimensional CADD drawings.

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The State of Arizona has also assembled Math standards and many of these apply directly to the vocational subject area of Drafting. Drafting is a very precise discipline and the use of mathematics is integral to design and manufacturing. Below are the math standards that are involved in this lesson

1M-P1. Compare and contrast the real number system and its various subsystems with
regard to their structural characteristics

• PO 2. Compare subsets of the real number system with regard to their properties
  (commutative, associative, distributive, identity, inverse and closure properties)

1M-P2. Construct, interpret and demonstrate meaning for real numbers and absolute

• PO 3. Solve real-world distance problems using absolute value
• PO 4. Determine, among the solutions to a real-world problem, which, if any, is reasonable
• PO 2. Define absolute value as the distance from the origin

4M-P1. Interpret and draw three-dimensional objects

• PO 1. Sketch prisms, pyramids, cones, cylinders and spheres
• PO 2. Classify prisms, pyramids, cones, cylinders and spheres by base shape and lateral surface shape.
• PO 3. Recognize the three-dimensional figure represented by a two-dimensional drawing.
• PO 5. Make a model of a three-dimensional figure from a two-dimensional drawing and make a two-dimensional representation of a three-dimensional object (models and representations include scale drawings, perspective drawings, blueprints or computer simulations)

4M-P4. Deduce properties of, and relationships between, figures from given
assumptions

• PO 1. Find similarities and differences among geometric shapes and designs using a given attribute (e.g., height, area, perimeter, diagonals and angle measurements)
• PO 2. Identify arcs, chords, tangents and secants of a circle
• PO 3. State valid conclusions using given geometric definitions, postulates and theorems
• PO 4. Represent pi as the ratio of circumference to diameter
  

 

Lesson Objectives

1. Draw an Isometric Grid using CADD software.
2. Making threads in isometric view.
3. Sketch Isometric models using an Isometric Grid.
4. Adjust line weights in ACAD for easier viewing of the constructed model.
5. Working with layers in ACAD in order to adjust line weights.
6. Working with colors for visualization enhancement.
7. Maintain approximate proportions using "boxing in" also called the "Glass box Technique"
8. Using a Geometric concept called "Circle Projection" to project the faces of a Hex bolt in isometric view.

Key Terms

"click on the key on any of these terms and it will hyperlink to the course glossary"

isometric	array	ellipse	orthographic
circle projection	hex bolt	unidirectional	aligned
exploded view	line weight	glass box	dimension
threads	proportion	ellipse	Boxing-in

 

Instruction

The following are the models that will be used for Lesson 3:

• Lesson 3: [exploded freehand sketch of Figure 2-15 on page 25 of your text]

For this model you will be drawing the isometric view. You will be using a technique called boxing in or the "glass box technique" in order to proportion the model with reasonable accuracy. It is not important about the dimensions as you will see in the figure, there are not any. In other words this is a free hand sketch and an approximation of what you see in the figure

I will explain this further in the lesson 3 media disc. Please insert the media disk and listen to lesson 3.

*Note: The Lessons are best viewed with real player and you can download the latest version by clicking on the words real player.

Your Text Book and Reading Assignments

Summary and Assessment