Computerization aids in the design of products, their fabrication, and the planning of manufacturing processes. Computerization of manufacturing began with the advent of computers after World War II, mainly in military-related applications. Now it is common in many commercial applications as well. The aerospace, automobile, chemical, electronics, and biomedical industries are among many that rely on computerized manufacturing.
In contemporary applications of computerized manufacturing, the process often begins with computer-aided design, more commonly known as CAD. In CAD, instead of drawing with pencils and a few drafting tools on paper, an engineer uses lines and curves stored in computer memory to produce a drawing that appears on a screen. The finished drawing can also be stored in computer memory.
Sometimes it is not faster to produce a drawing with CAD than it is to draw it by hand, especially when the drawing is in its initial stage. Why use CAD then? There are several advantages. First, a CAD program allows an engineer to "copy and paste" portions of drawing, just as text can be manipulated in word processing, moving them and using them in as many locations on the screen as necessary. Secondly, just as changing numeric values in a spreadsheet cell alters the rest of the spreadsheet accordingly, an engineer can make size changes to a drawing without using pencil and eraser. Another advantage to using CAD even for preliminary drafts is that an engineer can recall previously drawn components from computer memory and use them in the drawing. Finally, CAD allows an engineer to transform a two-dimensional sketch into one that appears to be three-dimensional, and to rotate the image on the screen to evaluate it from different angles. For these reasons, using a CAD program is much more efficient than drawing with pencil on paper.
CAD drawings can be incorporated into a computer-aided engineering (CAE) process. In CAE many hypothetical questions about material behavior can be answered by means of a computerized mechanical analysis of the effect of conditions such as stresses and deformations . CAE also uses visualization techniques such as computer animation to simulate a product's performance under various loads.
Instead of building expensive prototypes , engineers can use CAE software to create numerous computer simulations that help them determine how machines and their parts will behave in different circumstances. CAE is used in many applications, but it is especially important in the aerospace and automobile industries where weight reduction is always a highly sought-after goal of engineering.
After the design and engineering processes are complete, manufacturing involves materials handling and product fabrication. These processes can also be automated by computerized technologies. In technical literature, these technologies are usually referred to as CAM, which is an acronym for computer-aided manufacturing. When computer-aided manufacturing also uses computer-aided design, this is referred to as CAD/CAM.
Computerized materials handling focuses on automated storage and retrieval systems. These systems are automated warehouses where materials are stored on racks. The location of each stored material is registered in a database. Materials can be retrieved by conveyors, monorails, or computerized carts. The database keeps a continuous inventory of materials and their availability.
Fabrication of products and their components is automated by means of flexible manufacturing systems, robots, and embedded computers . The prevailing tendency in manufacturing is to shorten the time between conception of an idea and creation of a finished product so the consumer will get it as quickly as possible. Flexible manufacturing systems help achieve this goal. They often produce parts in small batches, just as they are needed for the rest of the manufacturing process.
Flexible Manufacturing Systems.
A flexible manufacturing system comprises equipment workstations connected by parts delivery routes. Parts are directed along those routes and are treated at the workstations. Each batch of parts might follow a different set of routes and workstations, according to production needs. In this way a manufacturing enterprise can quickly respond to ever-changing market demands and be ahead of the competition.
Delivery routes may employ motorized carts on tracks, or they may use motorized carts that follow wires embedded in the shop floor. Equipment workstations are the islands along delivery routes where tools for parts fabrication, assembly, and inspection are located. Most of those tools are automated and can be reprogrammed if the need arises. Each workstation is usually dedicated to the treatment of groups of similar parts.
Robots. Another approach to the automation of production is the use of industrial robots. Contrary to popular early images of robots, industrial robots do not and should not look like humans. Their main features are multifunctionality and reprogrammability. Paint-spraying robots in the automobile industry do not look at all human, but they help humans by doing their work in an environment that is hostile to human health.
Robots are also employed in the spot welding of automobile bodies. Because of the heat and bright light involved in spot welding, it is difficult for humans to perform this task with consistent quality. Not only is the job adaptable to robotics, it is better suited to computerization than to human performance. Other manufacturing processes suited to the multifunctionality of robots include the automated loading and unloading of heavy objects, the application of adhesives, the assembly of aircraft parts especially with rivets, the drilling and fastening of metal panels, and the sanding of missile wings, to name just a few.
The ability to reprogram a robot is an important advantage of using robots over other types of automated manufacturing equipment. A robot is made up of a controller, a manipulator, and sensors. The controller is a device through which a robot is programmed. Robots employ programs of varying complexity, from programs with multiple "if … then" conditions to artificial intelligence (AI) . An example of artificial intelligence is a program based on an expert system. Such a system is usually construed by gathering information from human experts. Out of this information, a program is developed. It encodes a set of rules mimicking human intuition. The robot is programmed to act according to this set of rules.
The robot's manipulator usually comprises electric, hydraulic, or pneumatic mechanisms that move an industrial robot's arms. An arm has a number of joints that determine its capability to fulfill the numerous functions the robot is designed to perform.
Not all robots are equipped with sensors, but the most versatile are. Of course, robots with sensors usually are much more expensive than those without. Sensors vary depending on tasks. If an industrial robot is used for inspection, its sensors may detect flaws in manufactured parts. A robot used to assemble electronic circuit boards is usually equipped with sensors that enable it to put components into proper places on the board.
Embedded computers are extensively used in many manufacturing applications, especially for the control of production processes. The most advanced of them are linked to sensors and have some kind of networking capability. They might receive remote commands and send this information to enterprise management system databases.
Computer-Aided Process Planning (CAPP)
Detailed planning is needed in order to implement a successful computerized manufacturing project. Once a design is finalized, an engineer prepares a detailed process plan. The plan comprises step-by-step instructions that include how to set up equipment, how to make a part, and last but not least, how to assure quality by inspecting the part after it is made. Routings between equipment workstations must also be determined. The plan is usually supplemented with drawings of the tools necessary to make the part and detailed instructions about how to operate the tools. Process planning is a tedious and time-consuming job. In a manufacturing environment, where it is always desirable to reduce time from idea to finished product, the computer-aided process planning (CAPP) can speed up the planning process and help ward off the competition.
There are two approaches to computer-aided process planning: variant and generative. The variant CAPP system is based on parts classification. As in biological classification, parts to be manufactured are combined into families. Parts that belong to a certain family have similar shapes, attributes, and parameters. They should also have similar production processes. This assumption is true in the majority of cases. The determination of which family a new part belongs to is made either manually by an engineer or by an appropriate artificial intelligence method. Once the family is established, a generic process description can be pulled from the program's database and an engineer may start modifying it to comply with the actual characteristics of the part.
One drawback of the variant CAPP is that the generic family process may not be suitable for a particular new part. The generative CAPP system does not have this drawback because it is based on an entirely different principle than variant CAPP. Instead of retrieving a generic family process and editing it, a process plan is created from scratch by using a set of decision rules that define the selection of proper operations, the sequence of operations, the treatments, the tools, and the delivery routes to be used in creating the part.
Computer Integrated Manufacturing (CIM)
The most advanced computerized manufacturing system is called Computer Integrated Manufacturing, or CIM. The goal of CIM is to combine synergistically all the computerized manufacturing technologies described earlier. At a slightly less comprehensive level, there are many manufacturing enterprises that include islands of automation—materials handling, for example—as well as manufacturing processes that are not automated. Integration of those islands into one system is another approach to CIM.
While integrating computerized manufacturing technologies into CIM, it is important to keep in mind that an enterprise might use different brands of equipment, process controllers, conveyors, robots, and other components. An engineer should always exercise common sense and evaluate profits versus costs while making a decision about what level of computerized manufacturing automation is appropriate in each particular case.
see also Chip Manufacturing; Image Analysis: Medicine; Process Control; Robotics; Robots.
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