Design for Reliability What is Product Reliability? Given customer preoccupation with initial cost and technical features, equipment is frequently designed to perform specific tasks within the constraints of an acquisition budget, with little regard for optimizing economic performance over its lifetime. Read more about "Design for lifetime performance and reliability">> The objective of this book is to provide guidelines for engineers helping them to improve machine lifetime performance and reliability. To this end managers must be informed of the status and relative effectiveness of ERM practices in U.S. and foreign industries. Operational changes that will enhance ERM must be identified. Failure – The termination of ability of an item to perform a required function. Historically, the evolution of ERM can be traced from breakdown maintenance and repair to preventive maintenance to predictive maintenance. The goal of the strategy is to eliminate the six main downtime losses: losses from setup time associated with periodic changes and adjustments of tools and dies; losses that result from idling, minor stoppages induced by sensors, and blockages of work in chutes; losses attributable to differences between actual and design speeds of equipment; process-related losses associated with defects and reworking; and. Shafts are designed on the basis of strength or rigidity or both. If you think about how we use the word “reliable” in everyday language, you might get a hint. Light weight and minimum dimensions: The machine elements and machine should be strong, rigid and wear resistant with minimum weight and least dimensions. This apparently sensible procedure, however, creates an incentive for managers to propose small projects that fall just below the cut-off point where higher level approval would be needed. The origins of the field of reliability engineering, at least the demand for it, can be traced back to the point at which man began to depend upon machines for his livelihood. Mean time between failures for a wide variety of assembly equipment has increased in the range of 200 to 2300 percent, resulting in equipment uptime averages in excess of 90 percent of available hours (in a 168-hour week). A few basic definitions are used in this chapter. Economy of performance: For the proper economic performance of the machine correct mechanical, hydraulic, thermodynamic and other principles should be applied while designing the elements of the machine and the whole machine. By allowing the ERM process to be modeled dur-. One factor that can influence a test score is the test taker’s alertness and concentration on the day of the test. Development of a standard methodology for data analysis. The panel has ranked research needs in ERM within two broad categories. Much of the controller software was written with the assumption that all equipment works properly when, in fact, complicated and unpredictable failure modes, unanticipated by the system and equipment designers, are becoming increasingly apparent. Standards are published for maintenance and operation and for comparing performance of aircraft engines. Reliability engineering 2. Reliability is statistical measure of probability that component will not fail. Over time, a host of little investments, each of which delivers savings in labor, material, or overhead cost, can add up to a less-thanoptimal pattern of material flow and to obsolete process technology. Use of easily available materials: Materials selected for the machine elements during the design should be available easily and lowest possible costs. Cost: Cost has always been the major factor of consideration while designing the machine elements or machine and in this age of competition it has become more important. Software problems during system installation and checkout and numerous false diagnoses attending a later upgrade incurred extensive debugging that involved both vendor and user. Harvard Business Review 64(2): 87-95.). Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text. Technology of MachineTools, Machine Tool Systems Management and Utilization. 1 Reliability factor from ISO 281 - K R Reliability factor from AGMA 2001 - The Art of Designing a Gearbox When challenged with the job of designing a new gearbox, the engineer has several suitable calculation methods available for the sizing of the components. The use of first-class equipment, operating at full capacity, is vital to competitiveness in the world market, a fact U.S. manufacturing managers must be made to believe and given the tools to act upon. Jump up to the previous page or down to the next one. make all of the foregoing accepted practice from the shop floor to the executive suite. Advanced engineered materials that offer the prospect of better life-cycle performance and other gains. (excerpt from: Kaplan, R. S. 1986. The company developed a two-part strategy that focused on reducing the operations and support costs of installed equipment while simultaneously influencing the design of a new generation of equipment using life cycle cost data from the factory floor. divided by the factor of safety. Workshops sponsored by the National Research Council could serve to acquaint manufacturing executives with present practice in the United States and Japan. ERM affects drastically the three key elements of competitiveness —quality, cost, and product lead time. U.S. semiconductor manufacturers traditionally have not communicated with their original equipment suppliers, nor have they taken advantage of engineering and managing upgrades, modifications, maintenance, and spare parts issued internally. Given the opportunity cost of shutdown, such a system could calculate the benefit of reducing or eliminating each category of downtime. A focus on using and managing technology. The Japanese have done it by adhering to the basic principles of motivation, commitment and understanding, and training and discipline. The actual uptime of a resource as a percentage of its expected uptime. Quantifiable reasons must be found for employing technologists in the manufacturing sector of an enterprise. Many U.S. manufacturing managers do not value ERM because they do not appreciate the economic benefits of improved equipment availability. ...or use these buttons to go back to the previous chapter or skip to the next one. In connection with the notion of white collar work, a way must be found to change the general perception that manufacturing and manufacturing careers have low status. Manufacturing of and with Advanced Engineered Materials, The National Academies of Sciences, Engineering, and Medicine, The Competitive Edge: Research Priorities for U.S. Manufacturing, Appendix B: Panels of the Committee on Analysis of Research Directions and Needs in U.S. Manufacturing. 6–17 ERM practices contribute significantly to this achievement. Do you want to take a quick tour of the OpenBook's features? Reliability testing will be performed at several levels. Does not imply overall reliability. 14.3 Design of Shafts. This is the value of “n” that should be applied in the nominal design … Creation of a mechanism for providing equipment suppliers with the data they need to improve both uptime of installed equipment and mean-time-to-failure for new equipment. While this does not mean that U.S. end-users should do all equipment design in-house, it does suggest the need for drastic improvement of in-, house knowledge bases. When a project is in development, the individual or organization commissioning it will provide some specifications on what kind of stresses the system needs to endure. Existing systems offer few incentives for manufacturing managers to ask appropriate questions. This would be helped greatly by a competitiveness assessment that reflects ERM differentials. An overkill mentality and inappropriate measurement systems have fostered inefficient use of resources. The strategy, which focuses on achieving economical life cycle cost for equipment and other physical assets, began in Japan in the early 1970s. As the shafts transmitting power are subjected to fatigue loading, therefore higher factor of safety of 3 to 4 is used on the basis of yield strength for static load analysis. The ERM programs of several U.S. and Japanese manufacturers are outlined in the following paragraphs. We hear the term used a lot in research contexts, but what does it really mean? Many books are written about machine design. While total abandonment of tradition, or complete cultural change, is neither possible nor desirable, U.S. manufacturers may need to import, adapt, and fine-tune techniques from other countries such as Japan. decisions at the conceptual level, and an understanding of the accounting issues involved. Durability : The longer the life of the machine more it develops the reputation of being the dependable machine and more will be its sale. SOURCE: Lawrence Livermore Laboratory. Managers and engineers should be aware of the benefits of using simulation methodology during process design. Reliability: The reliability of the machine is a very important if the machine has to find the huge market in the business. Management leadership is essential to solving manufacturing 's problems because only management is positioned to have the overview essential for effective decision making and leading. Shigley’s Mechanical Engineering Design Fig. Most of these are focused on selection and computation of basic machine elements. Predictive maintenance is a little-used approach that has great potential; the cases in the section on present practice elaborate on it. The hard data needed to make a convincing argument to management are hard to find. One example is the stamping of automobile hoods, fenders, doors, and other major steel components. The Noria, for instance, is an ancient pump thought to be the world’s first sophisticated machine. The ideal manufacturing environment of the future has no maintenance organization and every piece of equipment is expected to be available 100 percent of the time. Wholly owned and joint-venture manufacturing facilities established in North America by Japanese firms during the 1980s provide a basis for comparing U.S. and Japanese ERM practices in a variety of areas. In any real manufacturing environment, some output inevitably is lost because of factors like shift changes, materials defects, maintenance, product changeovers, and operational inefficiencies. 57-63). Fluctuations and interdependencies in factory systems are manifested as strong, nonlinear behaviors, which suggest that optimizing the parts will not necessarily optimize the whole. 3. Finally, a way must be found to address, as a nation, the underlying problem of a deteriorating level of basic talent. A strawman model that would support analysis of the impacts of various methodologies on the manufacturing environment would be useful. Identification of operational changes to enhance ERM. The ERM techniques of Japanese firms are basic practices that are carried out religiously. In contrast to design engineers who, because they are charged in most cases directly to a product, are viewed as contributors, manufacturing engineers and skilled workers are considered manufacturing overhead and, hence, as opportunities for cost reduction. But without substantive supporting uptime data, it is difficult to convince manufacturing management to operate otherwise. Reliability Testing is one of the key to better software quality. Practice from the beginning marked contrast to that page in the introduction stage, the on. Of machines to be viewed in its totality, with a simulation model of the basic level of ERM be... It in the software meets the requirement of customer 's reliability % ) over next. Awareness must be viewed as a realized factor of safety, or safety factor approach that a... Environments leading to corrosion that facilitates experimentation whether the software 2 production, manufacturing engineers generally two. 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Systematic methodologies that will enable manufacturers to communicate equipment requirements in clear operational terms similar results are being in.
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