,机电技术专业英语,2,Lesson Twenty,Text,Many engineers have as1 their function the designing of products that are to be brought into reality through the processing or fabrication of materials.In this capacity they are a key factor in the material selectionmanufacturing procedure.A design engineer,better than any other person,should known what he or she wants a design to accomplish.He knows what assumptions he has made about service loads and requirements,what service environment the product must withstand,and what appearance he wants the final product to have.In order to meet these requirements he must select and specify the material(s) to be used.In most cases,in order to utilize the material and to enable the product to have the desired form,he knows that certain manufacturing processes will have to be employed.In many instances,the selection of a specific material may,The Roles of Engineers in Manufacturing,Lesson Twenty,dictate what processing must be used.At the same time,when certain processes are to be used,the design may have to be modified in order for the process to be utilized effectively and economically.Certain dimensional tolerances can dictate the processing.In any case,in the sequence of converting the design into reality,such decisions must be made by someone.In most instances they can be made most effectively at the design stage,by the designer if he has a reasonably adequate knowledge concerning materials and manufacturing processes.Otherwise,decisions may be made that will detract from2 the effectiveness of the product,or the product may be needlessly costly.It is thus apparent that design engineers are a vital factor in the manufacturing process,and it is indeed a blessing to the company if they can design for producibility that is,for efficient production.,Lesson Twenty,Manufacturing engineers select and coordinate specific processes and equipment to be used,or supervise and manage their use.Some design special tooling that is used so that standard machines can be utilized in producing specific products.These engineers must have a broad knowledge of machine and process capabilities and of materials,so that desired operations can be done effectively and efficiently without overloading or damaging machines and without adversely affecting the materials being processed.These manufacturing engineers also play an important role in manufacturing. A relatively small group of engineers design the machines and equipment used in manufacturing.They obviously are design engineers and,relative to their products,they have the same concerns of the interrelationship of design,materials,and manufacturing processes.However,they have an even greater concern regarding the properties of the materials that their machines are going to process and the interreaction of the materials and the machines.,Lesson Twenty,Still another group of engineersthe materials engineersdevote their major efforts toward developing new and better materials.They,too,must be concerned with how these materials can be processed and with the effects the processing will have on the properties of the materials. Although their roles may be quite different,it is apparent that a large proportion of engineers must concern themselves with the interrelationship between materials and manufacturing processes.Lowcost manufacture dose not just happen.There is a close and interdependent relationship between the design of a product,selection of materials,selection of processes and equipment,and tooling selection and design.Each of these steps must be carefully considered,planned,and coordinated before manufacturing starts.This lead time,particularly for complicated products,may take months,even years,and the expenditure of large amount of money may be involved.Typically,the lead time for a completely new model of an automobile is about 2 years,for a modern aircraft it may be 4 years.,Lesson Twenty,With the advent of computers and machines that can be controlled by computers,we are entering a new era of production planning3.The integration of the design function and the manufacturing function through the computer is called CAD/CAM(computer aided design/computer aided manufacturing). The design is used to determine the manufacturing process planning and the programming information for the manufacturing processes themselves.Detailed drawings can also be made from the central data base4 used for the design and manufacture,and programs can be generated to make the parts as needed.In addition,extensive computer aided testing and inspection (CATI) of the manufactured parts is taking place.There is no doubt that this trend will continue at everaccelerating5 rates as computers become cheaper and smarter.,Lesson Twenty,New Words and Expressions,Lesson Twenty,Lesson Twenty,Notes,1. have as 意为“把作为” 2. detract from 意为“有损于” 3. production planning 意为“生产规划” 4. central data base 意为“中央数据库” 5. everaccelerating 意为“不断加速的”,Lesson Twenty,Lesson Twenty,参考译文,许多工程师的职责是进行产品设计