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The automobile industry has changed from the traditional single variety and large-scale production mode to the multi-variety, small and medium-sized batch and "variant variable" production mode, and the producer-led production mode has gradually changed to the consumer-led production mode. Flexible manufacturing is a good manufacturing mode to adapt to this change. Flexible manufacturing is a magic word in contemporary automobile production. Over the years. Automobile manufacturers have been chasing the dream of flexible manufacturing of automobiles. The so-called "flexible manufacturing" is an automatic mechanical manufacturing system consisting of an information control system, a material storage and transportation system and a group of numerical control processing equipment, which can flexibly and quickly adapt to the changes of processing objects. Through the "gentle" push of flexible manufacturing. The form of competition among major automobile manufacturers in the automobile market has changed from cost and price-oriented competition to market adaptability, new product launch speed and product personalization-oriented competition, and manufacturers without "flexible manufacturing" ability will be isolated.
1. Flexibility is related to the survival and development of manufacturing automation system.
Flexible manufacturing system (FMS) consists of two subsystems: processing, logistics and information flow, namely, a unified information control system, a material storage and transportation system and a set of numerical control processing equipment. Automatic mechanical manufacturing system that can adapt to the change of machining object. On the basis of processing automation: realize the automation of logistics and information flow.
The so-called flexibility can be manifested in two aspects. First, the ability of the system to adapt to changes in the external environment can be measured by the degree to which the system meets the requirements of new products; Second, the ability of the system to adapt to internal changes can be used in the case of interference (such as machine failure), when the ratio of the productivity of the system to the expected productivity without interference can be measured in meters. "Flexibility" is relative to "rigidity", and the traditional "rigidity" automatic production line mainly realizes batch production of a single variety. Its advantages are high productivity and high equipment utilization rate. Because the equipment is fixed, the cost of a single product is low. But the price is quite expensive, and only one or several similar parts can be added. If you want to get products from other seeds, you must make major adjustments to its structure and reconfigure all elements in the system. The workload and capital investment are usually equivalent to building a new production line. Rigid automatic production line for mass production is only suitable for producing a few varieties of products, but it is difficult to cope with multi-variety and small batch production.
Flexible manufacturing technology is the sum of all kinds of technologies to realize programmed flexible manufacturing for machining objects with different shapes. Flexible manufacturing technology is a technology-intensive group, and any T-plus technology with flexibility as its core and suitable for multi-varieties, small and medium-sized batches (including single products) belongs to flexible manufacturing technology. The technical basis of FMS is group technology. According to the group processing objects, the process flow is determined, and suitable storage and transportation systems are selected for CNC processing equipment and materials such as workpieces and cutters, which are crushed by computers. Therefore, it can be automatically adjusted to realize batch and efficient production of various workpieces in a certain range (that is, it is "flexible"). And can change products in time to meet market demand. The main technical and economic effects of adopting FMS are as follows: the processing of required parts can be arranged in time according to the matching needs of assembly work, and timely production can be realized, thus reducing the inventory of blanks and products in process, occupying working capital accordingly and shortening the production cycle; Improve the utilization rate of equipment, reduce the number of equipment and plant area; Reduce the direct labor force and realize 24-hour continuous "unmanned production" with less supervision; Improve the consistency of product quality.
Nowadays, the world has entered the era of information economy represented by network, knowledge and high technology, and its core is to meet the needs of consumers. With the progress of science and technology and the development of social economy, the market competition is increasingly fierce, the product life cycle is shortened, the upgrading is accelerated, the social consumption level is constantly improved, and the demand is gradually diversified and personalized. The new business environment and new production technology require enterprises to realize continuous innovation in technology, production and management, so the "flexible" development strategy is prevalent all over the world. The so-called "flexible" development strategy means that the manufacturing technology, production mode and management mode of enterprises are flexible, that is, flexible manufacturing, flexible production and flexible management. With the progress of society and the improvement of living standards, the market needs more distinctive personalized products to meet customers' requirements, styles and functions. Fierce market competition forces the traditional mass production mode to change, which requires the improvement of traditional parts production technology. The traditional manufacturing system can no longer meet the market demand for multi-variety and small batch products, so the flexibility of manufacturing system is more and more important to the survival of the system. With the mass production era gradually replaced by the production that adapts to the dynamic changes of the market, the viability and competitiveness of manufacturing automation system largely depend on whether it can produce different kinds of products with lower cost and higher quality in a short development cycle. Flexibility occupies a very important position. next page
2. The content and characteristics of flexible manufacturing system
Flexible manufacturing system has two main characteristics, namely flexibility and automation. The main difference between FMS and traditional single product automatic production line (relatively speaking, it can be called rigid automatic production line, such as automatic production line composed of mechanical, hydraulic automatic machine tools or modular machine tools) is that it is flexible. It is generally believed that flexibility plays a very important role in FMS, and an ideal FMS should have flexibility in many aspects. The main contents and characteristics of flexibility include:
Equipment (machine) flexibility: the processing equipment (machine) in the system has the ability to adapt to the changes of the processing object. Its measurement index is the preparation and replacement time of tools, fixtures and bedding required by processing equipment when the class, family and variety of the processing object change; Exchange and adjustment time of hardware and software; Preparation and adjustment time of processing program; When a series of different types of products are required to be produced, the difficulty of processing different parts changes with the change of products.
Process flexibility: the ability of the system to process a series of workpieces in various ways. The ability to adapt to the changes of products or raw materials when the process flow is unchanged, and the difficulty of changing the corresponding process in the manufacturing system to adapt to the changes of products or raw materials. Process flexibility, also known as processing flexibility or mixed-flow flexibility, is measured by the number of kinds of workpieces processed simultaneously without mass production.
Product flexibility: the system can be transformed into the ability to produce a series of new products economically and quickly. One is the ability of the system to produce new products very economically and quickly after the product is updated or completely turned; The other is the inheritance and compatibility of the useful features of the old product after the product is updated. Product flexibility is also called reaction flexibility. The index to measure product flexibility is the time required for the system to switch from processing one family of workpieces to processing another family of workpieces.
Process flexibility: the ability of the system to change the processing sequence of each workpiece. Its measurement index is the level of real-time artistic decision-making and on-site scheduling of the system.
Maintenance of flexible parts: can query and handle faults in various ways to ensure normal production.
Flexibility of production capacity: the quota and comprehensive ability of the system to adapt to the transformation of production objects. The ability of the system to operate economically when the production capacity changes. This is especially important for manufacturing systems that organize production according to orders.
Batch flexibility: the system can adapt to the cost accounting of different batches. Its measurement index is the minimum running batch of the system to maintain economic benefits.
Flexibility of expansion: the ability of the system to be easily modularized and expanded according to production needs. When production needs, it is easy to expand the system structure and add modules to form a larger system. Its measurement index is the scalable scale and difficulty of the system.
Operational flexibility: the system can handle its local faults and maintain its ability to continue producing the original series of workpieces. The ability to use different machines, materials and technological processes to produce a series of products and the same products, and the ability to switch to different processes. Its measurement index is the degree of productivity decline when the system fails or the time required to deal with the failure.
FMS only multiplies "flexibility" and "automation" to achieve the multiplication effect: it adapts to market demand and is beneficial to multi-variety and small and medium-sized batch production; Improve the utilization rate of machine tools, shorten the auxiliary time, and help reduce production costs; Shorten the production cycle and reduce inventory to improve the market response ability; Improving the level of automation is conducive to improving product quality, reducing labor intensity and improving production environment. FMS is an automatic manufacturing system managed and controlled by computer integration, which only produces small and medium batch, multi-variety and high efficiency parts. It has many standard manufacturing units and CNC machine tools with automatic electronic blanking function. A set of material storage and transportation system, which can transport workpieces and tools between clamping stations of machine tools; FMS is a programmable manufacturing system, including automatic material conveying equipment, which can realize information integration and logistics integration with the support of computer, and can process a variety of parts with similar physical characteristics and processing technology at the same time. Can automatically change tools and workpieces; Internet access is convenient and easy to integrate with other systems; Dynamic scheduling can be carried out, and the logistics path can be dynamically reorganized in the case of local failure. Flexible manufacturing system is a system with complex technology and high degree of automation. It organically combines microelectronics, computer and system engineering, and ideally solves the contradiction between high automation and high flexibility in mechanical manufacturing. At present, the scale of FMS tends to miniaturization and low cost, and it has evolved into a flexible parts manufacturing unit FMC. It may have only one machining center, but it has independent automatic machining capability. Some FMC have automatic transmission and monitoring management functions, and some FMC can also realize 24-hour unmanned operation. FMS used in equipment is called flexible equipment system.
3. The classification of flexible manufacturing system
Flexible manufacturing system refers to a manufacturing system with high degree of automation. Flexible manufacturing refers to a manufacturing system that can adapt to the changes of processing objects with the support of computers. It is a set of numerical control machine tools and other automatic processing equipment organically combined by computer information control system and automatic material storage and transportation system. Flexible manufacturing system consists of three subsystems: processing, logistics and information flow. At present, FMS usually refers to a manufacturing system with high automation and high flexibility in batch cutting. Flexible manufacturing system has the function of parts analysis and grouping with group technology as the core; Intelligent job planning function with microcomputer as the core; With the machining center as the core, the machining function of automatic tool change and workpiece change; Workpiece storage and transportation function with pallet and transportation system as the core; Automatic measurement, positioning and protection functions with various automatic detection devices as the core. next page
With the increasing demand for product diversification, low manufacturing cost and short manufacturing cycle, FMS has developed rapidly, and with the development of microelectronics, computer technology, communication technology, machinery and control equipment, flexible manufacturing technology has matured, and manufacturing automation has entered a new era, that is, computer-based integrated manufacturing (CIMS) era. FMS has become the focus of mechanical manufacturing automation research and development in industrialized countries. According to the size. Flexible manufacturing system FMS can be divided into the following four categories:
Flexible manufacturing unit. FMC is composed of a single machining center with multi-pallet system or less than three CNC machine tools, industrial robots, CNC machine tools and material transportation and storage equipment, which has the flexibility to adapt to a variety of product processing. The unit can automatically change the fixture and tooling as needed to process different workpieces. Flexible manufacturing unit is suitable for processing parts with complex shapes, simple processing procedures, long processing time and small batch. It has great equipment flexibility, but low personnel and processing flexibility. FMC can be regarded as the smallest FMS, which is the product of the development of FMS in the direction of cheapness and miniaturization. Its characteristic is to realize the flexibility and automation of single machine, and it has entered the stage of popularization and application so far.
Flexible manufacturing system. Flexible manufacturing system is a production system based on CNC machine tools or machining centers and equipped with material conveying devices. The system is automatically controlled by an electronic computer and can be used without stopping. Realize multi-variety, medium and small batch processing management. FMS is the most representative manufacturing automation system with flexible manufacturing technology. Flexible manufacturing system is suitable for processing parts with complex shape, many processing procedures and large batch. Its processing and material transfer are flexible, but the flexibility of personnel is still low.
Flexible production line (FML). Flexible production line is a production line between a single or a few large-scale inflexible automatic production lines and FMS. Its processing equipment can be ordinary processing centers and CNC machine tools. You can also use a special machine tool or a special CNC machine tool, which requires less flexibility for the material handling system than FMS, but has higher productivity. Flexible automatic production line is a production line composed of several adjustable machine tools (mostly special machine tools) and automatic conveying devices. This production line can process a large number of parts with different specifications. The flexible automatic production line with low flexibility is close to the automatic production line for mass production in terms of parts energy; The flexible automatic production line with high flexibility is close to the flexible manufacturing system for small batch and multi-variety production. It is represented by flexible manufacturing system in discrete production and distributed control system in continuous production. Its characteristic is to realize the flexibility and automation of the production line, and the technology is becoming more and more mature, so far it has entered the practical stage.
Flexible manufacturing factory (FMF). FMF connects multiple FMS, communicates with a computer system through an automated warehouse, and uses a complete FMS from ordering, design, addition, assembly, inspection, transportation to delivery. It includes CAD/CAM, and puts computer integrated manufacturing system (CIMS) into practice, realizing the flexibility and automation of production system, and then realizing the whole process of production management, product processing and material storage and transportation. FMF has the highest level of automation production, which embodies the most advanced automation application technology in the world. It integrates manufacturing automation, product development and management, and is represented by Intelligent Manufacturing System (IMS) with information flow controlling logistics. Its characteristic is to realize the flexibility and automation of the factory.
4. The composition of flexible manufacturing system
Flexible manufacturing system is an automatic mechanical manufacturing system, which consists of a unified information control system, a material storage and transportation system and a group of numerical control processing equipment, and can adapt to the transformation of objects. One of the achievements of the reform and opening up in recent years is that China has become a "manufacturing power" and a "world factory" in the world, and has made remarkable achievements. However, we should see that our products are still "made in China" rather than "made in China", and one of the measures to change this situation is to vigorously promote the development of FMS. A typical flexible manufacturing system consists of numerical control processing equipment, material storage and transportation system and information control system (specifically, the towel center management computer: logistics control device; Automated warehouse; Unmanned transport platform; Manufacturing unit; Central tool library; Fixture station; Information transmission network; Attached workbench). In order to realize the flexibility of manufacturing system, FMS must include the following components:
Automatic machining system: Automatic machining system refers to a system that processes parts with similar size (not necessarily the same shape), weight, material and technology on one or several CNC machine tools or special machine tools. The equipment used in FMS is determined by the type of workpiece to be machined, mainly including machining center, turning center, CNC lathe, milling machine, grinder and gear machining machine tool. Used to automatically complete various sequential processing.
Logistics system: used to realize the automatic supply and loading and unloading of workpieces and fixtures, as well as the automatic transmission, transportation and storage of working procedures. It consists of a variety of transportation devices, including various conveyor belts, automatic guided vehicles, industrial robots, tracks, turntables, manipulators and special lifting conveyors. The system that completes the supply and transmission of workpieces and tools is the main component of flexible manufacturing system.
Computer information control system: refers to a system that collects, processes and feeds back all kinds of information needed in the process of processing and transportation, and controls machine tools or transportation equipment at different levels through electronic computers or other control devices (hydraulic and pneumatic devices, etc.). ). It is used to process all kinds of information of flexible manufacturing system and output the information needed to control the automatic operation of CNC machine tools and material systems. Generally, a three-level (equipment level, workstation level and unit level) distributed computer control system is adopted. Cell-level control system (cell controller) is the core of FMS.
System software: refers to an indispensable part to ensure the effective management of flexible manufacturing system through electronic computers. Including design, planning, production control, system supervision and other software. Flexible manufacturing system is suitable for small and medium batch production with annual output of 1 0,000-100,000 pieces. It is used to ensure that the flexible manufacturing system can effectively adapt to the management, control and optimization of small and medium-sized batch and multi-variety production, including design planning software, production process analysis software, production process scheduling software, system management and monitoring software, etc.
The overall function of flexible center consists of engineering design system, engineering management system, quality management subsystem, workshop manufacturing subsystem and network database support system. The project management information subsystem (EMS) realizes project management, technical status management, inventory management, production planning and cost management. Quality information management subsystem (QMS) realizes the collection, analysis, processing, feedback and quality file management of production process quality information based on Intranet. The application of engineering design subsystem realizes the integrated design of key parts CAD/CAPP/CAM based on PDM. Workshop manufacturing subsystem (WMS) realizes NC machining of key parts, DNC of NC equipment, production planning and scheduling, etc. NET/DB provides an integrated environment for the operation of EMS and EDS. WMS subsystem provides intranet services and supports information integration of flexible center. next page
A typical flexible manufacturing system consists of numerical control processing equipment, material storage and transportation system and information control system. Processing equipment is mainly machining center and CNC lathe. The former is used to process box and plate parts, while the latter is used to process shaft and plate parts. FMS used in the production of medium-to-large-batch and few varieties often adopts replaceable headstock and centers to obtain higher production efficiency.
The materials transported by the storage and processing system include blanks, workpieces, tools, fixtures, inspection tools and chips. There are two ways to store materials: pallet warehouse with plane layout and truss warehouse with large storage capacity. Generally, the blank is first loaded into the fixture on the pallet by workers and stored in a specific area of the automatic warehouse, and then sent to the designated upper position by the automatic handling system according to the instructions of the material management computer. Fixed-track trolley and conveying raceway are suitable for FMS with equipment arranged in process sequence, while the order of conveying materials by automatic guiding trolley has nothing to do with the arrangement position of equipment, which has great flexibility. Industrial robots can carry and load and unload workpieces for 1-4 machine tools in a limited range. For larger workpieces, automatic pallet Replacement (APC) is usually used to transport them, and robots walking on the track can also be used to transport and load and unload the workpieces at the same time. The worn tools can be taken out from the tool magazine one by one for replacement, or the tool magazine full of tools to be replaced can be replaced with a spare sub-tool magazine. The jaws of lathe chuck, special fixture and spindle box of special machining center can also be automatically replaced. The chip conveying and processing system is a necessary condition for the continuous and normal operation of Wang Bao FMS. Generally, the economic structure scheme is selected according to the chip shape, removal amount and treatment requirements.
There are many structural forms of FMS information control system, but generally a hierarchical system with group control mode is adopted. The first stage is the computer numerical control device (CNC) of each process equipment to realize the control of each processing process; The second level is the group control computer, which is responsible for bringing great attention to the third-level computer factory. It will be the development trend of FML to replace the ordinary machining center with a special CNC machine tool with low price.
It is developing in the direction of multi-function and its application scope is gradually expanding. Multifunctional FMS, which integrates welding, assembly, inspection, sheet metal processing, casting and forging, is further developed on the basis of simple addition FMS. FMS is a novel conceptual model and a new development trend to realize the future factory, and it is also a strategic measure to determine the future development of manufacturing enterprises. The application scope is gradually expanding, such as the batch adaptation scope and variety adaptation specification of metal cutting FMS, such as FMS suitable for single piece production and FML suitable for batch production. On the other hand, FMS has developed from the initial metal cutting to the whole mechanical manufacturing field such as metal hot working and assembly. And quickly penetrated into electronics, food, medicine, chemical industry and other industries.
Developing towards modularization and integration. In order to help FMS manufacturers organize production, reduce costs, and help users to purchase the equipment in the system in stages and selectively, and gradually expand and integrate into a more powerful system, FMS software and hardware are developing in the direction of modularization. Combined with computer aided design and manufacturing system, different modules are designed by using the typical process data of the original product series to form various modular flexible systems with logistics and information flow. On the other hand, the computer integrated manufacturing system realizes the automation of the whole production process from product decision-making, product design, cattle production to sales, especially the automation at the management level. In this large system, flexible manufacturing system is only a part of it. In order to ensure the reliability and economy of the system, its main components can be standardized and modularized. Add parts conveying module, including induction line guide trolley conveying and track trolley conveying; Tool transport and exchange module, including tool exchange robot and tool transport mode with two * * * transport carts. Use different combinations of modules. Different forms of flexible manufacturing system are formed by logistics and information flow, and all the processing processes with different requirements are automatically completed. It is the basic trend of manufacturing automation to integrate FMS with modular structure and CIMS with FMS as the basic module.
Developing towards miniaturization and unitization. Early FMS emphasized scale. However, the resulting R has high cost, great technical difficulty, complex system and poor reliability, which is not conducive to rapid promotion. In order to let more small and medium-sized enterprises adopt flexible manufacturing technology, FMS develops from large-scale complex system to economical, reliable, easy to manage and flexible miniaturization and unitization, that is, to FMC or FMM. The emergence of FMC and FMM has been widely recognized by users. Flexible manufacturing system will develop flexible manufacturing cells and small FMS with various technological contents in the future; Perfecting the function of flexible manufacturing system; Expand the work done by FMS, and combine it with computer aided design and manufacturing technology (CAD/CAM) to develop towards fully automatic T-plant. The single technical performance and system performance have been continuously improved. The single technical performance and system performance are continuously improved, such as adopting various new technologies to improve the machining accuracy and efficiency of machine tools; Comprehensive use of advanced detection means, network, database and artificial intelligence technology, improve the self-diagnosis, self-debugging, self-repair, self-accumulation and self-learning capabilities of all units and systems of FMS, and make them have self-feedback, self-compensation and self-adaptive control capabilities for temperature change, vibration, tool wear, workpiece shape and surface quality; Advanced control methods and computer platform technology are adopted to realize the self-coordination, self-reconstruction and early warning functions of FMS.
Accelerate the development of flexible manufacturing cells and small FMS with various process contents. Because the investment of FMC is much less than that of FMS, the effect is similar, and it is more suitable for small and medium-sized enterprises with limited financial resources. The development trend of FML application in multi-variety and mass production is to replace the general machining center with a special numerical control machine tool with low price; In order to improve the automation function of FMS, the work done by FMS has expanded from simple mechanical processing in the early stage to comprehensive fields such as welding, assembly, inspection, sheet metal processing and even casting and forging. In addition, FMS is combined with computer aided design and manufacturing technology (CAD/CAM) to develop into a fully automated factory.
Flexible manufacturing technology is a novel conceptual model and new development trend to realize the future factory, and it is also a strategic measure to determine the future development of manufacturing enterprises. By then, intelligent machinery and people will be integrated with each other, flexibly and comprehensively coordinating all activities of enterprises from accepting orders to production and sales.