1、Process Planning and Concurrent EngineeringT. Ramayah and Noraini IsmailThe 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 plan is called process
2、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.Fundamentals of Mach
3、iningMachining is the manufacturing process in which the size, shape, or surface properties of a pert are changed by removing the excess material. Therefore, machining is a relatively expensive process that should be specified only when high accuracy and good surface finish are required, which, unfo
4、rtunately, are necessary for almost all mating parts.There are five basic types of machine tools to perform machining: lathe or turning machine, drilling or boring machine, milling machine, shaper or planer, and grinder. The first four, referred to as the basic machine tools, are similar in that the
5、y use cutting tools that are sharpened to a predetermined shape, whereas, the cutting edges on a grinding wheel are not controlled.The machining operation is chip formation process which is accomplished through the relative motion of a tool and the work piece, as is done with machine tools. However,
6、 the material removal mechanism my be chemical, electrical, or thermal as in the case of the unconventional processes such as electrochemical machining (ECM), electrical discharge machining (EDM), and laser-beam machining (LBM).The cutting conditions in machining with NC machines usually refer to th
7、ose variables that are changed by the part programmer and that affect the rate of metal removal. They are the cutting speed and the size of cut, which refers to the feed and depth.Process Planning Process planning involves determining the most appropriate manufacturing and assembly processes and the
8、 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 processes that can be planned are generally limited by the available processing equipment and technological capabiliti
9、es 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 details of the product design. This is a point we will return to later.Process planning is usually accomplished by manuf
10、acturing 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 the planners knowledge, skill, and experience, the processing steps are developed in the most logical sequence to make
11、 each part. Following is a list of the many decisions and details usually include within the scope of process planning.Interpretation of design drawing. The part of product design must be analyzed (materials, dimensions, tolerances, surface finished, etc.) at the start of the process planning proced
12、ure.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. In general, process planners must develop plans that utilize existing equipment in the plant. Otherwise, the compon
13、ent 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 actual design and fabrication of these tools is usually delegated to a tool design department and tool room, o
14、r 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 must be specified for manual operations. The industrial engineering department is usually responsible for this
15、area.Work standards. Work measurement techniques are used to set time s .Cutting tools and cutting conditions. These must be specified for machining operations, often with reference to standard handbook recommendations.Process planning for partsFor individual parts, the processing sequence is docume
16、nted 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 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 proce
