It would be great if computer systems were advanced enough to take a mental image of an object, such as the thought of a sports car, and instantly generate it as a three-dimensional computer aided design (CAD) model on a computer screen. Unfortunately, computer systems have not advanced to this point. For now, engineers must continue to express ideas as sketches.
A CAD model can quickly display an engineer’s ideas in a “real” setting. That is, once an engineer has developed a model in CAD, the idea can be shared much more easily.
As is the case with technical sketching, CAD models must begin as sketches of points, lines, or shapes. The major difference between a freehand sketch and a CAD sketch is accuracy. The lines of a CAD sketch can be drawn perfectly straight, with start and end points that occur in exact locations in space. A line may also be given precise length through the use of dimensions. If more than one line is being sketched, they can be made perfectly parallel or perpendicular, or given a specific angle. CAD programs give designers the ability to sketch any kind of geometry, along with the ability to dimension, extend, rotate, mirror, copy, pattern, move, trim, or erase it.
The ability to realize CAD models through sequentially developing geometric sketches is a critical skill that designers in multiple engineering disciplines use to make mental images into money-making products.
; Computer with 3D CAD solid modeling program
; PLTW. bmp graphic image
; CAD files
o Dimensioning Activity
o Trim Practice
o Extend Practice
o Move Practice
o Rotate Practice
o Geometric Constraints
o Project Geometry
o Water Bottle
Project Lead The Way, Inc.
IED – Unit 2 – Lesson 2.1 – Activity 2.1.3 – Making Sketches in CAD – Page 1
In order to effectively use a CAD program as a design tool, a designer must know what sketching tools are available and how they work. This activity will help you to understand and utilize the sketching tools that are common to most CAD programs.
There are 19 exercises in this activity. Many of the exercises require the creation of a new CAD file, and the replication of the images pictured. Other exercises require the manipulation of an already existing file(s). As you finish each exercise, initial the graphic, save the CAD file, document the file name and location on the line provided, and submit this activity to your instructor for evaluation.
1. The spline tool is used to create irregular curves, such as the involute curve on a
gear tooth, or the contour of a car body surface. Create a new CAD file, and use
the spline sketch tool to draw two irregular curves and two closed shapes that
approximate the figures pictured above. Note the locations and number of points
in each spline.
CAD file name and location:
Project Lead The Way, Inc.
IED – Unit 2 – Lesson 2.1 – Activity 2.1.3 – Making Sketches in CAD – Page 2