CAM, CAD/CAM, AND CIM
We have briefly defined the terms CAM, CAD/CAM, and CIM in our introduction. Let us explain and differentiate these terms more thoroughly here. The term computer integrated manufaclUrlng (CIM) is sometimes used interchangeably with CAM and CAD/CAM.
Although the terms are closely related.our assertion is that CIM possesses a broader meaning than does either CA M or CAD/CAM
Computer Aided Manufacturing
Computer-aided manufacturing (CAM) is defined as the effective use of computer technology in manufacturing planning and control. CAM is most closely associated with functions in manufacturing engineering, such as process planning and numerical control (NC) part programming. With reference to our model of production in Section 13.2, the applications of CAM can be divided into two broad categories:(1) manufacturing planning and (2) manufacturing control. We cover these two categories in Chapters 25 and 26, but Jet us provide a brief discussion of them here 10 complete our definition of CAM.
Manufacturing Planning. CAM applications for manufacturing planning are those in which the computer is used indirectly to support the production function, but there is no direct connection between the computer and the process. The computer is used "offline" to provide information for the effective planning and management of production activities. The following list surveys the important applications of CAM in this category:
Computer-aided process planning (CAPP). Process planning is concerned with the preparation of route sheets that list the sequence of operations and work centers required 10 produce the product and its components. CAPP systems are available today to prepare these route sheets. We discuss CAPP in the following chapter.
Computer-assisted NC part programming. The subject of part programming for NC was discussed in Chapter 6 (Section 6.5). For complex part geometries, computer assisted part programming represents a much more efficient method of generating the control Instructions for the machine tool than manual part programming is.
Computerized machinability data systems. One of the problems in operating a metal cutting machine tool is determining the speeds and feeds that should be used to machine a given work part. Computer programs have been written to recommend the appropriate cutting conditions to use for different materials. The calculations are based on data that have been obtained either in the factory or laboratory that relate tool life to cutting conditions. These machinability data systems are described in.
Development of work standards. The time study department has the responsibility for setting time standards on direct labor jobs performed in the factory. Establishing standards hv direct time study can be a tedious and time-consuming task. There are several commercially available computer packages for setting work standards. These computer programs 'use standard time data that have been developed for basic work elements that comprise any manual task. By summing the limes for the individual element, required to perform a new Job, the program calculates the standard lime for the job. These packages are discussed in
Cost estimating, The task of estimating the cost of a new product has been simplified in most industries by computerizing several of the key steps required to prepare the estimate. The computer is programmed to apply the appropriate labor and overhead rates to the sequence of planned operations for the components of new products. the program then sums the individual component costs from the engineering bill of materials to determine the overall product cost.
Production and inventory planning. The computer has found widespread use in many of the functions in production and inventory planning. These functions include: maintenance of inventory records, automatic reordering of stock items when inventory is depicted. production scheduling, maintaining current priorities for the different production orders, material requirements planning, and capacity planning. We discuss these activities in Chapter 26.
Computer-aided line balancing. Finding the best allocation of work elements among stations on an assembly line is a large and difficult problem if the line is of significant size. Computer programs have been developed to assist in the solution of this problem (Section 17.5.4).
Manufacturing Control. The second category of CAM application is concerned with developing computer systems to implement the manufacturing control function. Manufacturing control is concerned with managing and controlling the physical operations in the factory. These management and control areas include:
Process monitoring and control. Process monitoring and control is concerned with observing and regulating the production equipment and manufacturing processes in the plant. We have previously discussed process control in Chapter 4. The applications of computer process control arc pervasive today in automated production systems. They include transfer lines. assembly systems. NC, robotic>. material handling. and flexible manufacturing systems. All of these topics have been covered III earlier chapters.
Quality control: Qua1ity control includes a variety of approaches to ensure the highest possible quality levels III the manufactured product. Quality control systems were covered in the chapters of Pan IV.
Shop floor control. Shop floor control refers to production management techniques for collecting data from factory operations and using the data to help control production and inventory in the factory. We discuss shop floor control and computerized factory data collection systems in Chapter 26.
Inventory control. Inventory control is concerned with maintaining the most appropriate levels of inventory in the face of two opposing objectives: minimizing the investment and storage costs of holding inventory and maximizing service to customers. Inventory control is discussed in Chapter 26.
Just-in-time production systems. The term just-in-time refers to a production system that is organized to deliver exactly the right number of each component to downstream workstations in the manufacturing sequence just at the lime when that component ts needed. The term applies not only to production operations but 10 supplier delivery operations as well. Just-in-time systems are discussed in Chapter 26.
CAD/CAM is concerned with the engineering functions in both design and manufacturing. Product design, engineering analysis, and documentation of the design (e.g.. drafting) represent engineering activities in design. Process planning, NC part programming, and other activities associated with CAM represent engineering activities in manufacturing.
The CAD/CAM systems developed during the 1970s and early 1980s were designed primarily to address these types of engineering problems. In addition, CAM has evolved to include many other functions in manufacturing, such as material requirements planning, production scheduling, computer production monitoring, and computer process control.
It should also be noted that CAD/CAM denotes an integration of design and manufacturing activities by means of computer systems. The method of manufacturing a product is a direct function of its design. With conventional procedures practiced for so many years in industry, engineering drawings were prepared by design draftsmen and later used by manufacturing engineers to develop the process plan. The activities involved in designing the product were separated from the activities associated with process planning. Essentially a two-step procedure was employed. This was time-consuming and involved duplication of effort by design and manufacturing personnel. Using CAD/CAM technology, it is possible to establish a direct link between product design and manufacturing engineering. ln effect, CAD/CAM is one of the enabling technologies for concurrent engineering (Section 25.3). It is the goal of CAD/CAM not only to automate certain phases of design
and certain phases of manufacturing, but also to automate the transition from design to manufacturing. In the ideal CAD/CAM system, it is possible to take the design specification of the product as it resides in the CAD data base and convert it into a process plan for making the product, this conversion. being done automatically by the CAD/CAM system. A large portion of the processing might be accomplished on a numerically controlled machine tool As part of the process plan, the NC part program is generated automatically by CAD/CAM, The CAD/CAM system downloads the NC program directly to the machine tool by means of a telecommunications network. Hence, under this arrangement, product design, NC programming, and physical production are all implemented by computer.
Computer Integrated Manufacturing
Computer integrated manufacturing includes all of the engineering functions of CAD/CAM, but it also includes the firm's business functions that are related to manufacturing. The ideal CIM system applies computer and communications technology to all of the operational functions and information processing functions in manufacturing from order receipt, through design and production, to product shipment. The scope of OM, compared with the more limited scope of CAD/CAM, is depicted in Figure 24.7.
The CIM concept is that all of the firm's operations related to production are incorporated in an integrated computer system to assist. augment. and automate the operations. The computer system b pervasive throughout the firm, touching all activities that support manufacturing. In this integrated computer system, the output of one activity serves as the input to the next activity, through the chain of events that starts with the sales order and culminates with shipment of the product. The components of the integrated computer system are illustrated in Figure 24.8. Customer orders are initially entered by the company's sales force or directly by the customer into a computerized order entry system. The orders contain the specifications describing the product. The specifications serve as the input to the product design department. New products are designed on a CAD system. The components that comprise the product are designed, the bill of materials is compiled, and assembly drawings are prepared. The output of the design department serves as the input to manufacturing engineering, where process planning. tool design, and similar activities are accomplished to prepare for production. Many of these manufacturing engineering activities are supported by the (1M system. Process planning is performed using CAPP. Tool and fixture design is done on a CAD system, making use of the product model generated during product design. The output from manufacturing engineering provides the input to production planning and control. where material requirements planning and scheduling are performed using the computer system. And so it goes. through each step in the manufacturing cycle. Pull implementation of C1M results in the automation of the information flow through every aspect of the company's organization.
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