【正文】 individual system， e． g． leaf spring set in a vehicle， it is also termed as a mechanical part． 中英文資料 3 A good machine definitely requires quality individual ponents． Thus， the design of ponents is very important． When designing a machine， on the other hand， engineers invariably find that requirements and constraints of its ponents are interrelated． As a local portion， the ponent is expected to play a certain role on the machine and therefore must be appropriately restrained by the whole system． The design of a gear drive in a speed—reducer， for instance， depends upon not only the strength and stiffness， but also the space available for the gears in the shaft and relation with other transmission drive． This means that the design of the mechanical ponents inevitably requires a whole view in the whole system． Due to relationship between a machine and its ponents， the process of machinery design usually covers interconnected designs of machine， parts， and ponents． Any modification and adjustment in one ponent may considerably affect the designs of other ponents or parts． To present the best possible design solution， the iteration of evaluation， analysis and optimization across all the process seem indispensable． 1． 3 Overview of machinery design This course is primarily concerned with the design of specific ponents of machines or mechanical systems． Competence in this area is basic to the consideration and synthesis of plete machines and systems in subsequent courses and professional practice． It Can be seen that even the design of a single bolt or spring needs the designer’s thorough understanding of the principles and methods of machinery design together with empirical information， good judgment and even a degre3e of ingenuity in order to produce the best product for the society today． It is natural that designing engineers give first consideration to the functional and economic aspects of new products or devices． Machinery design needs to ensure safety and reliability in a prescribed lifetime． To address such a problem conventionally， the technical consideration of the mechanical ponent design is largely centered around two main areas of concerns： (1) strengthstiffnessstability criteria involving the bulk of a solid member and (2) surface phenomena including friction， lubrication， weal7， and environmental deterioration． However， in parison with such relatively straightforward putations as stress and deflection， the design determination of safety and reliability is likely to be an elusive and indefinite matter， plicated by psychological and sociological factors． It must be kept in mind that safety and reliability are inherently relative to each other， and the value judgments must be made with regard to trade—offs between safety， reliability， cost， weight，and so forth． On the other hand， a practical design needs to reflect clearly manufacturability and economy to make sure of the lowest cost as well as the least consumption of energy and materials． Otherwise， the products or devices designed will be of no further engineering or mercial interests． Nowadays， the simultaneous considerations of 中英文資料 4 manufacturing and assembly factors phases including design， manufacturing，inspection， as assembly and other is considered in such a parallel fashion that the quality and cost are best satisfied concurrently． In addition to these traditionally technological and economic considerations fundamental to the design and development of mechanical ponents and systems， the modern engineers have bee increasingly concerned with the broader considerations of sustainability， ecology， aesthetics， ergonomics， maintainability，and overall quality of life． It is clear that a greater than ever engineering effort is being recently devoted to broader considerations relating to the influences of engineered products on people as well as on the environment． The following is a list of general factors for engineers to consider in the design process， which from a different viewpoint shows us a panoramic picture with regard to the designrelated activities and tasks． (1) Cost of manufacturing． Will the selling price be petitive? Are there cheaper ways of manufacturing the machine? Could other materials be used? Are any special tools， dies, jigs， o