Talk about first job.

82 CHAPTER 4 The Design Process and Product Discovery Design is a process—not just building hardware. —Tim Carver, OSU student, 2000 in Fig. 4.1. They are a refinement of the phases in a product’s life cycle Fig. 1.8 that are of concern to the designer. For each phase, there are a series of activities that need to be accomplished. The phases and activities are briefly introduced in this chapter and refined throughout the rest of the book. After this introduction, the first phase, Product Discovery, is explained in detail. This design process, as shown, applies to design of systems, subsystems, assemblies, and components. It applies to new, innovative products and to changes in existing products. Of course, the detail and emphasis will change with the level of decomposition and with the amount of change needed. To help introduce the phases and how they are used at all levels in a product’s decomposition consider the design of a General Electric CT Scanner. Product Discovery Project Planning Product Definition Conceptual Design Product Development Product Support Figure 4.1 The mechanical design process.

4.2 Overview of the Design Process

83 General Electric designs and manufactures many different types of prod- ucts including home appliances, lightbulbs, jet engines, and a host of medical products. One of the products developed by GE’s healthcare business is the CT Scanner shown in Fig, 4.2. The full name of the technology used in this scan- ner is X-ray Computed Tomography CT. CT is a diagnostic imaging technique that can produce solid images of the organs inside patients. A CT system con- sists of a patient table that can be positioned and moved through the bore of the gantry. Beneath the sleek outer casing, the gantry houses a frame that holds an X-ray tube and a detector. The X-ray tube is on the top at the 1 o’clock position in Fig. 4.3 and the arc-shaped detector is on the bottom at the 7 o’clock position. The frame, X-ray tube, and detector rotate around the patient at 120 rpm. This means that there is a centrifugal acceleration on the components of more than 10gs. Thus, the X-ray tube components experience very large radial body loads and covey centrifugal loading to the gantry support of approximately 2000 N of radial force. In order to generate images of organs the tube emits rays that pass through the patient, are sensed by the detector, and are processed by a computer, as shown in Fig. 4.4. To accomplish this, the X-ray tube emits bursts of X-rays. During emission, the tube requires 60–100 kW of power. This power must be transmitted to the rotating tube, where the majority of the power is converted into waste heat that must be transferred out of the gantry. Making the design task even more Figure 4.2 GE CT Scanner. Source: Reprinted with permission of GE Medical.