|
CAD is an electronic system for designing new parts or products or altering existing ones, replacing drafting traditionally done by hand. The heart of CAD is a powerful desktop computer and graphics software that allow a designer to manipulate geometric shapes. The designer can create drawings and view them from any angle on a display monitor. The computer can also simulate the reaction of a part to strength and stress tests. Using the design data stored in the computer’s memory, manufacturing engineers and other users can quickly obtain printouts of plans and specifications for a part or product. CAD cuts the cost of product development and sharply reduces the time to market for new products. CAD literacy is now a prerequisite for designers, and investments in it are growing rapidly. Many company budgets for CAD are three times what they were in 1990.
The component of CIM that deals directly with manufacturing operations is called computer-aided manufacturing (CAM). CAM systems are used to design production processes and to control machine tools and materials flow through programmable automation. For example, researchers at the Technology/Clothing Technology Corporation are developing a concept to enable clothing manufacturers to create “custom” clothing. The concept involves using a computer scan of a customer’s body and a computer-driven machine to cut the fabric to fit the customer perfectly. Automated custom clothing goes against established apparel industry procedures, whereby companies cut dozens of layers of cloth at the same time to hold down labor costs. However, labor costs account for only 11 percent of the cost of the garment delivered to the customer. Nonvalue-added handling (including inventory costs) after manufacture accounts for 27 percent, which is the cost category that this technology can reduce. It also has the advantage of fostering customization and speedy delivery as competitive priorities. For example, Levi Strauss is already using similar, although more cumbersome, technology for women’s jeans, and its customers are willing to pay a premium.
A CAD/CAM system integrates the design and manufacturing function by translating final design specifications into detailed machine instructions for manufacturing an item. CAD/CAM is quicker, less error prone than humans, and eliminates duplication between engineering and manufacturing. CAD/CAM systems allow engineers to see how the various parts of a design interact with each other without having to build a prototype.
Numerically controlled (NC) machines are large machine tools programmed to produce small- to medium-sized batches of intricate parts. Following a preprogrammed sequence of instructions, NC machines drill, turn, bore, or mill many different parts in various sizes and shapes. The technology was developed in the early 1950s at the Massachusetts Institute of Technology to find more efficient methods of manufacturing jet aircraft for the U.S. Air Force.Currently, NC machines are the most commonly used form of flexible (programmable) automation. Early models received their instructions from a punched tape or card.
Computerized numerically controlled (CNC) machines are usually stand-alone pieces of equipment, each controlled by its own microcomputer. NC and CNC machines rank just after CAD in terms of the most popular CIM technologies.
Robots are more glamorous than NC workhorses. The first industrial robot joined the GM production line in 1961. Industrial robots are versatile, computer-controlled machines programmed to perform various tasks. These “steel-collar” workers operate independently of human control. Most are stationary and mounted on the floor, withan arm that can reach into difficult locations. The robot’s “hand,” sometimes called an end effector or tool, actually does the work. The hand (not shown) can be changed to perform different tasks, including materials handling, spot welding, spray painting, assembly, and inspection and testing. Second-generation robots equipped with sensors that simulate touch and sight have spawned new applications. For example, pick fruit from trees, mix chemicals in laboratories, and handle radioactive materials. The initial cost of a robot depends on its size and function. Other potential costs include modifying both product and process to accommodate the robot, preparing the worksite, installing and debugging the robot, and retraining and relocating workers. Benefits from robot installation include less waste materials, more consistent quality, and labor savings. Robots are the drudges of the workforce, performing highly repetitive tasks without tiring, taking a lunch break, or complaining.
In manufacturing and service industries, the choice of how, when, and by whom materials are handled is an important technological decision. Materials handling covers the processes of moving, packaging, and storing a product. Moving, handling, and storing materials cost time and money but add no value to the product. Therefore, operations managers are always looking for ways to reduce costs by automating the flow of materials to and from an operation. Whether materials handling automation is justifiable depends on the process. When the process experiences low volumes and must provide a high degree of customization, job paths vary and there is little repeatability in materials handling. Such variability means that workers must move materials and equipment in open-top containers, carts, or lift trucks. However, when the process experiences high volumes, line flows, and high repeatability, handling can be automated. In addition, other types of flexible automation are now available for processes that fall between these two extremes. Let’s look at two such technologies: automated guided vehicles and automated storage and retrieval systems
A flexible manufacturing system (FMS) is a configuration of computer-controlled, semi independent workstations where materials are automatically handled and machine loaded. An FMS is a type of flexible automation system that builds on the programmable automation of NC and CNC machines. Programs and tooling setups can be changed with almost no loss of production time for moving from production of one product to the next. Such systems require a large initial investment ($5 to $20 million) but little direct labor to operate. An FMS system has three key components:
- Several computer-controlled workstations, such as CNC machines or robots, that perform a series of operations
- A computer-controlled transport system for moving materials and parts from one machine to another and in and out of the system
- Loading and unloading stations
Workers bring raw materials for a part family to the loading points, where the FMS takes over. Computer-controlled transporters deliver the materials to various workstations where they pass through a specific sequence of operations unique to each part. The route is determined by the central computer. The goal of using FMS systems is to synchronize activities and maximize the system’s utilization. Because automation makes it possible to switch tools quickly, setup times for machines are short. This flexibility often allows one machine to perform an operation when another is down for maintenance and avoids bottlenecks by routing parts to another machine when one is busy
|
Participants