1、 英文资料及中文翻译 Process Planning and Concurrent Engineering T. Ramayah and Noraini Ismail ABSTRACT The product design is the plan for the product and its components and subassemblies. To convert the product design into a physical entity, a manufacturing plan is needed. The activity of developing such a p
2、lan is called process planning.It is the link between product design and manufacturing.Process planning involves determining the sequence of processing and assembly steps that must be accomplished to make the product. In the present chapter,we examine processing planning and several related topics.
3、Process Planning Process planning involves determining the most appropriate manufacturing and assembly processes and the sequence in which they should be accomplished to produce a given part or product according to specifications set forth in the product design documentation.The scope and variety of
4、 processes that can be planned are generally limited by the available processing equipment and technological capabilities of the company of plant.Parts that cannot be made internally must be purchased from outside vendors. It should be mentioned that the choice of processes is also limited by the de
5、tails of the product design.This is a point we will return to later. Process planning is usually accomplished by manufacturing engineers.The process planner must be familiar with the particular manufacturing processes available in the factory and be able to interpret engineering drawings.Based on th
6、e planners knowledge,skill, and experience,the processing steps are developed in the most logical sequence to make each part.Following is a list of the many decisions and details usually include within the scope of process planning. .Interpretation of design drawings. The part of product design must
7、 be analyzed (materials,dimensions, tolerances,surface finished,etc.) at the start of the process planning procedure. .Process and sequence. The process planner must select which processes are required and their sequence.A brief description of processing steps must be prepared. .Equipment selection.
8、 In general, process planners must develop plans that utilize existing equipment in the plant.Otherwise, the component must be purchased,or an investment must be made in new equipment. .Tools,dies,molds,fixtures,and gages. The process must decide what tooling is required for each processing step.The
9、 actual design and fabrication of these tools is usually delegated to a tool design department and tool room,or an outside vendor specializing in that type of tool is contacted. .Methods analysis. Workplace layout, small tools, hoists for lifting heavy parts,even in some cases hand and body motions
10、must be specified for manual operations.The industrial engineering department is usually responsible for this area. .Work standards. Work measurement techniques are used to set time standards for each operation. .Cutting tools and cutting conditions. These must be specified for machining operations,
11、often with reference to standard handbook recommendations. Process planning for parts For individual parts,the processing sequence is documented on a form called a route sheet. Just as engineering drawings are used to specify the product design,route sheets are used to specify the process plan.They
12、are counterparts, one for product design,the other for manufacturing. A typical processing sequence to fabricate an individual part consists of: (1) a basic process, (2) secondary processes,(3) operations to enhance physical properties,and (4)finishing operations. A basic process determines the star
13、ting geometry of the workparts. Metal casting, plastic molding,and rolling of sheet metal are examples of basic processes.The starting geometry must often be refined by secondary processes,operations that transform the starting geometry (or close to final geometry).The secondary geometry processes t
14、hat might be used are closely correlated to the basic process that provides the starting geometry.When sand casting is the basic processes,machining operations are generally the second processes.When a rolling mill produces sheet metal,stamping operations such as punching and bending are the seconda
15、ry processes.When plastic injection molding is the basic process,secondary operations are often unnecessary,because most of the geometric features that would otherwise require machining can be created by the molding operation.Plastic molding and other operation that require no subsequent secondary p
16、rocessing are called net shape processes.Operations that require some but not much secondary processing (usually machining) are referred to as near net shape processes.Some impression die forgings are in this category.These parts can often be shaped in the forging operation(basic processes) so that
17、minimal machining (secondary processing) is required. Once the geometry has been established,the next step for some parts is to improve their mechanical and physical properties.Operations to enhance properties do not alter the geometry of the part； instead,they alter physical properties. Heat treati
18、ng operations on metal parts are the most common examples.Similar heating treatments are performed on glass to produce tempered glass.For most manufactured parts,these property-enhancing operations are not required in the processing sequence. Finally finish operations usually provide a coat on the w
19、ork parts (or assembly)surface. Examples included electroplating,thin film deposition techniques,and painting.The purpose of the coating is to enhance appearance, change color,or protect the surface from corrosion, abrasion, and so forth.Finishing operations are not required on many parts；for exampl
20、e, plastic molding rarely require finishing. When finishing is required,it is usually the final step in the processing sequence. Processing Planning for Assemblies The type of assembly method used for a given product depends on factors such as: (1) the anticipated production quantities；(2) complexit
21、y of the assembled product, for example,the number of distinct components；and (3) assembly processes used, for example,mechanical assembly versus welding.For a product that is to be made in relatively small quantities,assembly is usually performed on manual assembly lines.For simple products of a do
22、zen or so components,to be made in large quantities,automated assembly systems are appropriate. In any case,there is a precedence order in which the work must be accomplished.The precedence requirements are sometimes portrayed graphically on a precedence diagram. Process planning for assembly involv
23、es development of assembly instructions,but in more detail .For low production quantities,the entire assembly is completed at a single station.For high production on an assembly line,process planning consists of allocating work elements to the individual stations of the line, a procedure called line
24、 balancing.The assembly line routes the work unit to individual stations in the proper order as determined by the line balance solution.As in process planning for individual components,any tools and fixtures required to accomplish an assembly task must be determined,designed, built, and the workstation arrangement
