5.1 INTRODUCTION

Design problem solving consists of seven stages as illustrated in the previous chapter. From this chapter, we will concentrate on the stages of conceptual design and detaildevelopment of design model.

As three-dimensional parametric modeling techniques have advanced, efforts on engineering designs have shifted more toward visualizing and modeling than the concerns of communication because the means of design communication is nearly automated once the design models are completed. In the past two decades, basic design modeling principles are feature-based technique that has become the gold standard in computer-aided design modeling.

Feature-based design modeling mimics product machining. It bridges the gap between design modeling and manufacturing and intuitively strengthens the concept of design for manufacturing. The introduction of feature-based modeling enhances the relationship between design modeling and manufacturing.

In general, feature-based design modeling is accomplished in two steps: (1) creating the base feature, and (2) adding detail design features to the base feature. Each base feature serves as a piece of stock material, as if a raw material is selected to start for the manufacturing of a product. To create the base feature, two approaches can be employed: generating a simple stock model based on the given options of a specific CAD system (Figure 5-1), or depicting a sketched profile and extruding it (see Figure 5-2).

Figure 5-1: Block and cylinder based models

Figure 5-2: Sketch and extruded base features

The second approach requires knowledge of engineering drafting. It involves specifying a placement plane, sketching, and dimensioning. This could...