Related to Electronic Engineering - Essay Example

29 April 2007 Engineering Design Ans a) Quality Function Deployment (QFD) and its Importance in Engineering DesignQuality Function Deployment (QFD) is a set of powerful product development  tools that were developed in Japan to transfer the concepts of quality control from the  manufacturing process into the new product development process. QFD is also defined as a systematic translation or total-quality-management process in which the “voice of the customer” is deployed throughout the R&D, engineering, and manufacturing stages of product development. QDF is used to identify critical customer attributes and to create a specific link between customer attributes and design parameters. Matrices are used to organize information to help marketers and design engineers answer three primary questions: What attributes are critical to our customers? What design parameters are important in driving those customer attributes? What should the design parameter targets be for the new design? For QDF process the organising framework is a planning tool called the “house of Working as a team, design engineers and marketers first establish critical customer attributes for the product. These attributes become the rows of the central matrix of the house of quality. The team may group attributes into broader categories in order to simplify planning and analysis (Wheelwright, 1992).  The key benefits obtained by adopting QFD are given below.  • Reduced time to market    • Reduction in design changes    • Decreased design and manufacturing costs    • Improved quality    • Increased customer satisfaction   Ans 1(b) Let we plot the Fault data of programmable chemical mixer in descending order of fault frequency and plot a Pareto chart as shown in fig. 2. Since the purpose of the Pareto chart is to Fig. 1 Fault data sheet distinguish the “vital few from the trivial many” therefore, from chart it is obvious that only a few bars (representing power systems, control boards, pipelines and Transducers) on the left side of the Pareto chart accounts for most, say 80%, of the problems and required immediate attention to avoid the complete Fig. 2. 3D Pareto Chart failure. If we draw a cumulative line as shown in fig. 3, then the steep slope behavior of line indicates that each successive block contributes an uneven problem area. The bar at the top left side is the most critical problem and should be address at priority basis. Fig. 3. Pareto Chart cumulative line Ans. 1(c) Ans 3(ai) Sinusoidal Test The simplest vibration test which simulates the transportation or mission profile experienced by a product under steady conditions is termed as sinusoidal test. Examples of such vibration includes instruments working on a rattling vehicle or aircraft traveling at cruising speed. The sinusoidal test is performed by programming and controlling the variation factors such as displacement, velocity, acceleration, and force and by creating a sinusoidal vibration profile V=Asin (ωt). The test patterns obtained can be used to test and evaluate a wide variety of applications such as scanners, lenses, cameras, electronic imaging devices, photographic materials, etc. The sinusoidal test Sinusoidal test patterns used in conjunction with an image scanner or micro-densitometer are used for evaluating the modulation transfer function (MTF) of an optical system. Sinusoidal test is carried out by sinusoidal testers. The basic building blocks or components of an industrial electrodynamics vibration system are of an amplifier, a vibration control system, a slip tables, head expanders and fixturing. For large value of ‘g, a sinusoidal testers based on hydraulic mechanism is used while for small value of ‘g, electromagnetic principal based sinusoidal testers are used. Ans 3(aii) Resonance Search Test It is a natural tendency that every object can vibrate with a certain natural frequency called resonance. When an object vibrates with its resonance frequency it absorbs a large amount of energy. This energy is internally dissipated in the form of  vibration of parts relative to each other. These vibration may cause wear and tear and  in the long term result in the damage of the system. PCBs are susceptible to resonance  vibration as shown in the illustration in Fig. 4. A resonance search test is used to identify the resonance frequency of the product or the electronic board. A resonance search involves vibrating the product under test on three of its axis (x, y and z) with controlled vibration, sweeping through a range of vibration frequency and the vibration of its surface are measured with a accelerometer. The frequency which yields the largest amplitude of surface vibration will be the  resonance frequency. Fig. 4 PCB Resonance Vibration Profile Ans 3(aiii) Random Vibration Test Many vibration environments are not related to a specific driving frequency and may have input from multiple sources which may not be harmonically related. Examples may be excitation from turbulent flow as in air flow over a wing or past a car body, or acoustic input from jet engine exhaust, wheels running over a road, etc. With these types of vibrations and many more, it may be more accurate and more interesting to analyze, test and assess the soundness of design in electronic components and systems using different random vibration. Unlike sinusoidal vibration, acceleration, velocity and displacement are not directly related by any specific frequency. Of primary concern in random testing is the complete spectral content of the vibration being measured or generated. In random vibration test, each individual frequency within a given range is excited separately and randomly. The signal fed to the drive amplifier of the vibration  platform is a shaped noise signal. As such it contains every component of frequency  within a given range, each with constant peak amplitude. Shaping is achieved using  filters to achieve a particular frequency spectral shape. Ans 1(aiv) Bump Test References Wheelwright. S. C. and Clark. K. B., 1992, Revolutionizing Product Development, The Free Press, New York. http://www.labworks-inc.com/enginfo/random_vib_test.htm Read More