Tech Directions - February 2008 - (Page 20)

The Solution Solve the problem by following the steps below. (Refer to Figs. 2 and 3.) 1. Sketch the end shape (surface R) on the default construction plane. 2. Extrude the sketch to create the block of material. 3. Create a new construction plane by selecting the front face (surface W) and rotating 45° around line K. 4. Now rotate the new plane 300° around line Q. 5. Place a reference point 1" along line K from its end point. 6. Obtain a true view of the new Fig. 2 R W Q B View E Fig. 3 View B-B 60° B View A-A 60° View E Front view A Side view A construction plane, and draw the dovetail slot in alignment with the point created in step 5. 7. Extrude and cut the dovetail slot. Note that all angles in the solution will vary depending on how the clockwise/counterclockwise software variable is set on your solid modeling software system. between points, lines, and planes, as well as the angles between them. Finding the solution to this sample problem involves the ability to visualize the spatial relationships between the various geometries in the problem. These kinds of personal visual spatial skills are a prerequisite to Final Thoughts The creation of a complex construction plane requiring multiple steps is a pictorial space problem. If you reread my description of the sample problem, you will note that the problem is defined in terms of relationships advanced solid modeling. Not all advanced modeling problems are K the same (e.g., see Fig. 4). There are many different kinds of complex machine features with their own unique space problems. Teaching step-by-step solutions to a variety of advanced solid modeling problems is helpful but not a completely effective way to teach advanced solid modeling skills. When the variables in the problem change, the student will not always be able to rely on step-by-step instructions. The CAD operator must be able to visualize the geometric relationships between the construction planes and the geometry of the machine part being modeled. Descriptive geometry is the science of graphic representation. It allows for the solution of space problems. Many readers will remember their college descriptive geometry class as primarily based on orthographic projection. However, the content of descriptive geometry also includes a study of pictorial space problems. The creation of a complex construction plane requiring multiple steps is a pictorial space problem. The most efficient method for teaching advanced solid modeling skills is to place an emphasis on pictorial space problems. This can be done with paper problems and two-dimensional CAD problems, as well as with three-dimensional CAD problems. The solid modeling Fig. 4 software cannot solve space problems for the CAD operator. Developing the CAD operator’s personal visual spatial skills is the most efficient way to build advanced solid modeling skills. 20 techdirections ◆ FEBRUARY 2008

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Tech Directions - February 2008 Technically Speaking Contents Direct from Washington The News Report Technology’s Past Technology Today Mastering Computers How Engineers Engineer—Lessons from My First Big Engineering Project Tips on Creating Complex Geometry Using Solid Modeling Software Press to Test—Shop-Built BJT Checker Is Easy Cable Television Technician International Technology Education Association Conference—Teaching TIDE with Pride Professional Development Opportunities Product Central Free for the Asking More than Fun

Tech Directions - February 2008

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