1 Basic Concepts
1 1 Flexibility Flexibility can be expressed in two ways.
The first is the ability of the system to adapt to changes in the external environment, which can be measured by the degree to which the system meets the requirements of the new product; the second is the ability of the system to adapt to internal changes, which can be measured by the ratio of the productivity of the system in the presence of disturbances (e.g., machine breakdowns) to the expected value of productivity in the absence of disturbances. "Flexibility" is relative to "rigidity" in terms of the traditional "rigid" automated production line is mainly to achieve a single species of mass production. Its advantages are high productivity, because the equipment is fixed, so the equipment utilization rate is also very high, the cost of a single product is low. But the price is quite expensive, and can only process one or several similar parts, difficult to cope with multiple varieties of small batch production. With the era of mass production is gradually adapted to the market dynamic changes in the production of replacement, a manufacturing automation system of viability and competitiveness depends largely on whether it can be in a very short development cycle, the production of low-cost, high-quality different varieties of products the ability. Flexibility has occupied a fairly important position. Flexibility mainly includes
1) machine flexibility when the requirements of the production of a series of different types of products, the machine with the product changes and the ease of processing different parts.
2) process flexibility First, the process is unchanged when its own ability to adapt to changes in products or raw materials; Second, the manufacturing system to adapt to changes in products or raw materials to change the degree of difficulty of the corresponding process.
3) Product Flexibility First, the product is updated or completely turned, the system can be very economical and rapid production of new products; Second, the product is updated, the useful characteristics of the old product inheritance and compatibility.
4) maintenance flexibility using a variety of ways to query, deal with the fault, to ensure that the normal production capacity.
5) Flexibility of production capacity The ability to operate the system economically even when the production volume changes. For the manufacturing system to organize production according to the order, this is particularly important.
6) Expansion Flexibility When production needs, you can easily expand the system structure, add modules, the ability to form a larger system.
7) Operational flexibility The ability to use different machines, materials, processes to produce a series of products and the same product, the ability to switch to different processes.
1 2 Flexible Manufacturing Technology Flexible manufacturing technology is a variety of different shapes and shapes of processing objects to achieve the programmed flexible manufacturing and processing of a variety of technologies. Flexible manufacturing technology is a technology-intensive technology group, we believe that all focus on flexibility, adapted to multi-species, small and medium batch (including single product) processing technology are flexible manufacturing technology. At present, according to the size of the division is:
1) Flexible Manufacturing System (FMS)
About the definition of flexible manufacturing system many, authoritative definitions are:
National Bureau of Standards of the United States to the FMS is defined as: "a transmission system linked to a number of devices, transmission devices to the workpiece in other linkage devices sent to the processing equipment, so that the workpiece is sent to a number of equipment. The FMS is defined by the National Bureau of Standards as "a number of devices connected by a transmission system. With a centralized computer controlling the machine tool and the transfer system, a flexible manufacturing system can sometimes process several different parts at the same time. The International Association for Production Engineering Research states that "a flexible manufacturing system is an automated manufacturing system capable of producing any range of product families with minimal human intervention, and the flexibility of the system is usually limited by the product families considered in the design of the system." China's national military standard is defined as "flexible manufacturing system is composed of CNC machining equipment, material transportation and storage devices and computer control systems for automated manufacturing system, which includes a number of flexible manufacturing units, according to the manufacturing task or the production environment changes quickly adjusted for multi-species, small and medium-sized batch production." Simply put, FMS is composed of a number of numerical control equipment, material transportation and storage devices and computer control systems and can be quickly adjusted according to changes in manufacturing tasks and production varieties of automated manufacturing systems.
Currently common composition usually includes four or more fully automated CNC machine tools (machining centers and turning centers, etc.), by the centralized control system and material handling system connected to the case can be achieved without stopping multiple varieties, small and medium batch processing and management. Currently reflects the overall level of the factory FMS is the first generation of FMS, Japan from 1991 to implement the "Intelligent Manufacturing System" (IMS) international development projects, belonging to the second generation of FMS; and the real perfection of the second generation of FMS is expected to be realized after the decade of this century.
2) Flexible Manufacturing Cell (FMC)
FMC was introduced and used in production about 6 to 8 years later than FMS, FMC can be regarded as a smallest scale FMS, FMS is cheap and miniaturized direction of the development of a product, which is composed of 1 to 2 sets of machining centers, industrial robots, CNC machine tools and material delivery storage equipment, which is characterized by achieving Flexibility and automation of a single machine, with the flexibility to adapt to the processing of multiple varieties of products. So far, it has entered the popularization and application stage.
3) Flexible Manufacturing Line (FML)
It is in a single or few varieties of large-volume non-flexible automated line with small and medium batches of many varieties of FMS between the production line. Its processing equipment can be a general-purpose machining centers, CNC machine tools; can also use special machine tools or NC special machine tools, the material handling system is less flexible than the requirements of the FMS, but the productivity is higher. It is a discrete production in the flexible manufacturing system and continuous process of decentralized control system (DCS) as a representative of the characteristics of the realization of the production line flexibility and automation, its technology has become mature, and has entered the practical stage.
4) Flexible Manufacturing Factory (FMF)
FMF is a multi-FMS connected, with automated three-dimensional warehouses, with a computer system for contact, from the order, design, processing, assembly, inspection, delivery to the shipment of the complete FMS. it includes CAD / CAM, and make the computer-integrated manufacturing system (CIMS) into the actual realization of the production system flexibility and automation, the technology has reached maturity, has entered the practical stage. Production system flexibility and automation, and then realize the whole factory-wide production management, product processing and material storage and transportation process of the whole system.FMF is the highest level of automated production, reflecting the world's most advanced automation application technology. It is the automation of manufacturing, product development and business management into a whole, with information flow control material flow of intelligent manufacturing system (IMS) as a representative, which is characterized by the realization of factory flexibility and automation.
2 key technologies used in flexible manufacturing
2.1 computer-aided design
The future development of CAD technology will be introduced into the expert system, so that it has the intelligence to deal with a variety of complex problems. One of the latest breakthroughs in current design technology is the photosensitive stereoforming technology, the new technology is the direct use of CAD data, through the computer-controlled laser scanning system, the three-dimensional digital model into a number of layers of two-dimensional sheet graphics, and according to the two-dimensional sheet graphics of the pool of photosensitive resin liquid surface for optical scanning, was scanned to the liquid surface into a cured plastic, and so on the cycle of operation, scanning and forming layer by layer, and automatically By automatically bonding the layers of cured plastic together, accurate prototypes can be produced within a few hours by simply determining the data. It helps to speed up the development of new products and new structures.
2.2 Fuzzy Control Technology
The practical application of fuzzy mathematics is the fuzzy controller. Recently developed high-performance fuzzy controllers with self-learning function, can be in the control process to continuously obtain new information and automatically adjust the control volume, so that the system performance is greatly improved, especially based on artificial neural network self-learning method has attracted great attention.
2.3 Artificial Intelligence, Expert Systems and Smart Sensor Technology
To date, most of the artificial intelligence used in flexible manufacturing technology refers to rule-based expert systems. Expert systems use expert knowledge and reasoning rules to reason and solve all kinds of problems (e.g., interpretation, prediction, diagnosis, fault finding, design, planning, monitoring, repair, command and control, etc.). Because the expert system can easily combine the facts and proven theories with the knowledge gained through experience, the expert system enhances flexibility for all aspects of flexible manufacturing. In the future, artificial intelligence (including expert system) technology, which is characterized by knowledge intensity and knowledge processing, will play an increasingly important role in flexible manufacturing (especially intelligent). Currently used in the flexible manufacturing of various technologies, it is expected that the most promising development is still artificial intelligence.
It is expected that by the beginning of the 21st century, the scale of the application of artificial intelligence in flexible manufacturing technology will be four times larger than at present. Intelligent Manufacturing Technology (IMT) aims to integrate artificial intelligence into all aspects of the manufacturing process, with the help of simulation of the intelligent activities of experts, to replace or extend the manufacturing environment in the human part of the brain work. In the manufacturing process, the system can automatically monitor its operating status, and can automatically adjust its parameters to achieve the best working condition when stimulated from outside or inside, with self-organizing ability. Therefore, IMT is called the future manufacturing technology of the 21st century. Intelligent flexible manufacturing technology is important to the future of an intelligent and flexible manufacturing technology is the rapid development of the field of intelligent sensor technology. The technology is accompanied by computer applications and artificial intelligence, it makes the sensor has an inherent "decision-making" function.
2 4 Artificial Neural Networks
Artificial Neural Networks (ANN) is a method of simulating the neural networks of intelligent organisms to process information. Therefore, artificial neural network is also a kind of artificial intelligence tool. In the field of automatic control, neural network will soon be listed in the expert system and fuzzy control system, become a component of modern automation system.
3 Flexible Manufacturing Technology Development Trends
3 1 FMC will become the development and application of popular technology
This is because the investment in FMC than the FMS is much less than the economic benefits of similar, more suitable for limited financial resources of small and medium-sized enterprises. At present, many foreign manufacturers will FMC as a development priority.
3 2 development of more efficient FML
Multi-species, high-volume production enterprises such as automotive and tractor factories on the demand for FML caused by the FMS manufacturer's great concern. The use of inexpensive special CNC machine tools to replace general-purpose machining centers will be the development trend of FML.
3 3 towards the direction of multi-functional development
From the simple processing FMS further development to welding, assembly, inspection and sheet metal processing and even casting, forging and other manufacturing processes with a variety of functions FMS.
4 Conclusion
Flexible Manufacturing Technology is the realization of the future of the factory's novel conceptual model and new development trends, is to determine the future of the manufacturing enterprises. It is a strategic initiative to determine the future development of manufacturing enterprises. At that time, intelligent machinery and people will be integrated with each other, flexible and fully coordinated from the acceptance of orders to production and sales of all the activities of the enterprise production and management.
In recent years, flexible manufacturing as a modern industrial production of scientific "philosophy" and factory automation of the advanced model has been internationally recognized, it can be argued that: flexible manufacturing technology is in the automation technology, information technology and manufacturing technology on the basis of the previous enterprise independent of each other's engineering, manufacturing and business management processes. Manufacturing and management processes, in the computer and its software support, constituting a complete and organic system covering the entire enterprise, in order to achieve the dynamic optimization of the overall situation, the overall high efficiency, high flexibility, and thus win the competition to win the intelligent manufacturing technology. It is as the world's manufacturing automation technology development of cutting-edge technology for the future of institutional manufacturing plant provides a grand blueprint, will become the 21st century institutional manufacturing industry's main production model. It realizes the division of virtual networks by ports, MAC addresses, applications, etc., effectively controlling the broadcast traffic of the internal network and improving the security of the internal network.
5 Conclusion
In reality, there are many different types of networks, some support TCP/IP, some follow the OSI standard protocols, each machine's corresponding layer of protocols are different, which layer of the implementation of the connection, you need to use the corresponding network interconnection equipment.
In layman's terms, the second layer of switching refers to the multi-port switching hub line, that is, network switches. Its purpose is to replace the traditional hub, to enhance the effective bandwidth of the network. It is mainly used in LANs. In different or the same type of LAN between the use of bridges (hubs), from the protocol layer belongs to the data link layer of the device, but they are still the method of network connectivity, because the LAN IMP itself does not have a network layer, only in the host site has a network layer or the function of providing network layer services. Unlike bridges, gateways work at the network layer level. This allows for greater flexibility. For example, translating addresses between widely differing networks, etc., but this also results in gateways being slow, so they are generally used for interconnecting WANs or interconnecting LANs to WANs. With the evolution of the network and the emergence of 100M high-speed Ethernet, the delay caused by routers in the communication between network segments is becoming more and more a bottleneck in the transmission of network information [4]. The emergence of Layer 3 switching technology, to solve the large-scale local area networks in the network between the sub-segments of the bottleneck in the transmission of network information, replacing the expensive router, a practical, economical networking technology.
Composition and technical objectives of the flexible center
Through the construction of the flexible center scientific research, the computer application ability and technology processing level in the development of large-scale antenna system reaches the domestic leading level and the international level in the early nineties, and provides a strong guarantee for the completion of the key development tasks.
(1) based on flexible manufacturing technology and system integration technology, through the configuration of advanced CNC machining equipment and computer systems, the use of computer technology as the core of the modern design, manufacturing and management technology, the establishment of a flexible manufacturing center with industry characteristics.
(2)Apply CAD/CAM technology to realize the computer-aided design of key parts of antenna system, and gradually realize the parallelization of the design process of flexible center.
(3)Applying modern information management technology and computer control technology of processing, realizing the flexibilization of manufacturing process of key parts.
(4) through the establishment of network and database cloudy environment, for the realization of the center's operational process of functional interaction, information integration and resource **** enjoyment to create conditions.
(5) Improve the comprehensive strength and modernization level of the unit, and improve the ability to respond to the market.
(6) The overall functional composition of the Flexibility Center is shown in Figure 1, consisting of engineering design system, engineering management system, quality management subsystem, workshop manufacturing subsystem and network database support system.
①Engineering Management Information Subsystem (EMS) realizes project management, technical status management, inventory management, production plan formulation and cost management.
②Quality Information Management Subsystem (QMS) based on Intranet to realize the production process quality information collection, analysis, processing, feedback and quality document management.
③Engineering Design Subsystem (EDS) application based on PDM to realize the feeder key parts CAD/CAPP/CAM integrated design.
④Workshop Manufacturing Subsystem (WMS) to realize the antenna key parts of the CNC machining, CNC equipment, DNC, production plan scheduling and so on. Network database support environment (NET/DB) for EMS, EDS, WMS subsystem operation to provide an integrated environment to provide Intranet services to support the information integration of the flexible center.