Flexible automation is the combination of mechanical technology and electronic technology, that is, a new generation of automation with mechatronics. Its processing program is flexible and changeable, also known as variable programming automation. With the development of science and technology, human society requires higher and higher functions and quality of products, the cycle of product upgrading is shorter and shorter, and the complexity of products is higher and higher, which challenges the traditional mass production mode. This challenge not only poses a threat to small and medium-sized enterprises, but also puzzles large and medium-sized state-owned enterprises. Because, under the mass production mode, flexibility and productivity are contradictory. As we all know, only a single variety, large quantities, special equipment, stable technology and high efficiency can constitute economies of scale; On the other hand, the equipment specificity of multi-variety and small batch production is low, and the process is difficult to be stable under the condition of similar processing forms, and the production efficiency is bound to be affected. In order to improve the flexibility and production efficiency of manufacturing industry at the same time, shorten the production cycle and reduce the cost of products under the premise of ensuring product quality, and finally make small and medium-sized batch production compete with large-scale production, flexible automation system came into being.
Since the birth of 1954 MIT's first CNC milling machine, flexible automation entered the practical stage of production in the early 1970s. For decades, the application of single-machine CNC machine tools has gradually developed to machining centers, flexible manufacturing units, flexible manufacturing systems and computer integrated manufacturing systems, which has made flexible automation develop rapidly.
The content of flexible automation:
Flexible automation came into being in 1950s, which is the automation combining mechanical technology and electronic technology. Based on hardware and supported by software, the required control can be realized by changing the program, so it is flexible and changeable, realizing the flexibility and efficiency of the manufacturing process, and suitable for multi-variety, small and medium-sized batch production. Including CNC machine tools, machining centers, industrial robots, flexible manufacturing units, flexible manufacturing systems, etc.
A, CNC machine tools
Numerical control machine tool (NC) is a machine tool that uses information (program instructions) in the form of digital codes to control tools to perform automatic machining according to a given working program, motion speed and trajectory. The machining process of parts by CNC machine tools is carried out in strict accordance with the parameters and actions specified in the machining program. It is an efficient automatic or semi-automatic machine tool. Compared with ordinary machine tools, when the processing object changes, it is generally only necessary to change the numerical control program, which shows good adaptability and can greatly save the production preparation time. CNC machine tools have high accuracy and rigidity, and can choose favorable processing dosage, with high productivity, which is generally 3 ~ 5 times that of ordinary machine tools. For the processing of some complex parts, the production efficiency can be improved by ten times or even dozens of times. The use of CNC machine tools is beneficial to the development of computer control and management of production, and creates conditions for the automation of production process.
Second, the processing center
Machiningcenter (MC) is a more complex, more widely used and more efficient CNC machine tool, which is formed by adding tool magazine and automatic tool changing device on the basis of ordinary CNC machine tools. With the tool magazine and automatic tool changer, turning, milling, boring, reaming, tapping and copying can be completed on one machine tool. Therefore, the machine tool in the machining center has the advantage of centralized working procedures, which can effectively shorten the adjustment time and handling time, reduce the inventory of WIP and improve the machining quality. Machining center is often used in production occasions with complex parts, multi-process processing and medium production batch.
Modern machining centers are developing in the direction of multi-coordinate, multi-station, polyhedron machining and reassembly (replacing headstock and other components), such as turning and milling machining centers, milling and boring machining centers, pentahedron machining centers, five-coordinate (multi-coordinate) machining centers, etc., and numerical control systems are also developing in the direction of openness, distribution, adaptive control, multi-level hierarchical control, networking and integration. Therefore, numerical control processing can not only be used for single piece and small batch production,
Thirdly, flexible manufacturing unit.
Flexiblemanufacturingcell (FMC) is a kind of variable machining cell, which consists of a single computer-controlled machining center or numerical control machine tool, annular (circular, angular or rectangular) pallet conveying device or robot. The cutting monitoring system is adopted to realize automatic machining and continuous production, and there is no need to stop and replace the workpiece. It is the basic unit of flexible manufacturing system.
Flexible manufacturing unit is more flexible than a single CNC machine tool or machining center, and can realize more kinds of supporting machining. According to the Japanese practice, flexible manufacturing units can generally process 2 1.3 kinds of parts every day, and the processing time for assembling products to complete 50 kinds of parts is 2.34 days, while using machining centers can only complete the same task, and it takes 23.9 days to complete 50 kinds of parts. Flexible manufacturing unit can run continuously for 24 hours, and machining center can only work for18 hours. The operation utilization rate of flexible manufacturing unit is 65,438+0.5 times that of MC. Compared with the system investment of machining center, the investment of flexible manufacturing unit that completes the same task can save 17.34%, and the number of operators is only 82.67% of that of MC.
Compared with flexible manufacturing system, the main advantages of flexible manufacturing unit are: small floor space, uncomplicated system structure, low cost, low investment, high reliability and simple use and maintenance. Therefore, flexible manufacturing cell is one of the main development directions of flexible manufacturing system, which is welcomed by various enterprises.
Fourthly, flexible manufacturing system.
1, the concept, characteristics and application scope of flexible manufacturing system
Flexiblemanufacturingsystem (FMS) is a manufacturing system consisting of several (at least two) machining centers or CNC machine tools, automatic loading and unloading devices, storage and transportation systems, etc. There is no fixed processing sequence and rhythm. Under the centralized control of computer and its software system, the workpiece and fixture can be adjusted and replaced without stopping, thus realizing machining automation.
Compared with the traditional rigid automatic production line, it has the following outstanding features:
(1) has a high degree of flexibility, can realize the processing of different "types" of parts with different technological requirements, and can automatically replace workpieces, fixtures, cutters and automatically clamp, and has powerful system software functions.
(2) High degree of automation, stability and reliability, which can realize long-term unattended automatic continuous work (such as continuous work for 24 hours).
(3) Improve equipment utilization and reduce auxiliary time such as adjustment and preparation for termination.
(4) High productivity.
(5) Reduce direct labor costs and improve economic benefits.
Flexible manufacturing system is widely used. If the parts are large in batch and few in variety, special machine tool lines or automatic production lines can be used. If the parts are produced in small batches and have many varieties, it is suitable to use CNC machine tools or general machine tools; The middle section is suitable for the processing of flexible manufacturing system.
2. Types of flexible manufacturing systems
Flexible manufacturing system is a general term with many types, which can be divided into flexible manufacturing unit, flexible production line and flexible production line. Flexible manufacturing cells have been discussed before, and now they are divided into flexible manufacturing lines and flexible production lines.
Flexible manufacturing production line (FML) consists of two or more machining centers, numerical control machine tools or flexible manufacturing units. Equipped with automatic conveying device (track, trolley or robot), automatic workpiece loading and unloading device (pallet exchange or robot) and automatic warehouse, it has computer hierarchical control function, data management function, production planning and scheduling management function and real-time monitoring function.
FlexibleTransmissionLine (FTL) is composed of several machining centers. However, the material system does not use highly automated automatic transport vehicles, industrial robots and automatic warehouses, but uses loading and unloading devices used in automated production lines, such as various feeding troughs. Instead of pursuing a high degree of flexibility and automation, it is economical and practical. This flexible manufacturing system is also called quasi-flexible manufacturing system.
3. Composition and structure of flexible manufacturing system
Flexible manufacturing system consists of three parts: material system, energy system and information system, and each system is composed of many subsystems.
The main processing equipment of FMS is machining center and CNC machine tool. At present, milling and boring machining centers (vertical and horizontal) and turning machining centers account for the majority, generally consisting of 3 ~ 6 sets. Flexible manufacturing system commonly used conveyor belts, trackless (trackless) transport vehicles, walking industrial robots, etc. , you can also use some special transmission devices. In the flexible manufacturing system, multiple conveying devices can be used at the same time to form a composite conveying network. The conveying modes can be straight line, ring and mesh. The storage equipment of flexible manufacturing system can use three-dimensional warehouse and stacker, and can also use plane warehouse and pallet station. Tray is a walking fixture, which is equipped with a workpiece fixture, and the workpiece is clamped on the workpiece fixture. The pallet, the workpiece fixture and the workpiece are conveyed integrally by the conveying device, and the pallet is clamped on the workbench of the machine tool. The pallet station can also play the role of temporary storage, and it is set near the machine tool to play a buffering role. Warehouse can be divided into blank library, parts library, tool library and fixture library, among which tool library has two kinds: centralized management center tool library and special tool library scattered beside each machine tool. In addition to the main processing equipment, there should also be cleaning workstations, deburring workstations and inspection workstations in the flexible manufacturing system, which are all flexible working units.
Flexible manufacturing system has the unique flexibility of manufacturing different products, which can produce different products without changing the hardware structure of the system, thus adapting to market changes and shortening the research and development cycle of new products; With the help of computer, the auxiliary processing time of flexible manufacturing system is greatly reduced, which can significantly improve the utilization rate of machine tools, up to 75% ~ 90%; Due to the combination of working procedures, the clamping times and the number of machine tools used are reduced, the equipment cost is reduced, the inventory of products in the system is reduced, the working cycle time is shortened, and the production cycle is shortened; The control, management and transmission of the system are all carried out under the computer, which reduces the number of operators.
According to the statistics of FMS, the processing cost can be reduced by 50%, the production area can be reduced by 40%, the productivity can be increased by 50%, and the work-in-process can be reduced by 80%. The main disadvantages of flexible manufacturing system are: large system investment and long payback period; The system structure is complex, and the requirements for operators are very high; The complex structure makes the reliability of the system poor.
Five, group technology
Group technology developed from group processing in 1950s to group technology in 1960s, and group production units and assembly lines appeared, and its scope also expanded from simple machining to the whole product manufacturing process. After 1970s, the combination of group technology with computer technology, numerical control technology, similarity theory, methodology and system theory developed into group technology.
The essence of group technology is to group the parts produced in small and medium batches according to their structural and technological similarities, which is equivalent to expanding the batch of parts. Therefore, technologies similar to mass production can be adopted to achieve the purpose of improving productivity and economic benefits. Group technology is the viewpoint of applied systems engineering, which regards the design, manufacture and management in multi-variety and small batch production as a whole production system, unifies and coordinates all aspects of the production system, and comprehensively applies group technology to obtain the best comprehensive economic benefits. The application of group technology can promote the standardization of part design and avoid unnecessary repeated design and diversified design in product design; In product manufacturing, it can promote the standardization, standardization and generalization of process design, reduce repetitive work, realize group processing and application of group fixtures, and improve production efficiency and system flexibility; In production management, it can shorten the production cycle, simplify the operation plan, reduce the number of products in process, improve the utilization rate of personnel and equipment, improve quality and reduce costs.
1, basic principle
Group technology is a comprehensive technology involving many disciplines. Its theoretical basis is similarity and its core is group technology. At present, it has the characteristics of computer-aided group technology.
Group technology is to make parts with similar size, shape and technology into a part family (group) and manufacture them according to the process of the part family, so as to expand the batch, reduce the variety, and facilitate the adoption of efficient production methods, thus improving labor productivity and opening up a way to improve the economic benefits of multi-variety and small-batch production.
Similarity of parts in geometry, size, functional components, accuracy, materials, etc. It is basically similar. On the basis of basic similarity, the similarity derived from production, operation and management such as manufacturing and assembly is called secondary similarity or derivative similarity. Therefore, the second similarity is the development of basic similarity, which has important theoretical significance and practical value.
The basic principle of group technology shows that the similarity of parts is the basic condition to realize group technology. Process similarity means that the same process method can be used for processing, similar fixtures can be used for clamping, and similar fixtures can be used for testing. Part classification and coding system is an important tool to realize group technology. Group technology is to reveal and use basic similarity and secondary similarity, so that industrial enterprises can get unified data and information, and change single-piece small batch production into batch production.
2, group technology implementation and production organization form
1) Implementation steps of group technology
The implementation steps of grouping process are as follows:
(1) Group and classify the product parts according to the part classification coding system.
(2) Using computer-aided process design to formulate the group processing technology of parts.
(3) Design group process equipment, such as group fixture, group cutter and group measuring tool.
(4) Design group process equipment, such as group fixture, group cutter and group measuring tool.
(5) Build a group processing production line and design a group conveying device, a group loading and unloading device, a warehouse, etc.
2) Production organization form of group technology
The production organization forms of group technology can be basically divided into three categories.
(1) Independent group processing machine tools or flexible manufacturing units for group processing are mainly used for parts with simple shapes and large similarities, which can be completed on one machine tool.
(2) The mixed production line of group machining and general machining is mainly used in the case that the parts are complex and have little similarity, and multiple machine tools are needed to complete all the processes. Those that can be processed in groups are processed by group processing machine tools, and those that cannot be processed in groups are processed by ordinary machine tools or even special machine tools to form a mixed production line (segment).
(3) Group processing production line or flexible manufacturing system for group processing This is the highest organizational form of group processing, and all processes of parts are processed in groups.
3. Parts classification and coding system
The concept and function of (1) part classification and coding system. The classification and coding of parts is to describe the geometric shape, size and technological characteristics of parts with numbers, that is, the digitalization of parts features.
In group technology, the function of part classification and coding system is not to describe the characteristics of parts completely, but to classify and group parts to form part families for group processing. Therefore, as long as the information in the part classification and coding system can meet the needs of describing the group classification of parts, it is impossible to deduce the complete shape, size and tolerance of parts from the part classification and coding.
(2) Part features to be described by the part classification and coding system and their extraction. Part classification is based on the characteristics of parts, which can be generally divided into three aspects:
(1) structural features, geometric shapes, dimensions, structural functions, blank types, etc.
(2) Process characteristics, blank shape, machining accuracy, surface roughness, machining methods, materials, positioning and clamping methods and machine tool types.
(3) Production organization and planning characteristics, processing batch, manufacturing resources, process routes across workshops and sections, inter-factory cooperation, etc.
(3) The structure of parts classification and coding system. The characteristics of parts are represented by corresponding symbols, which can be described by corresponding links in the classification and coding system. The classification and coding system of parts can be divided into multi-level and single-level according to the number of classification links. At present, the multi-level classification and coding system is widely used, and each level is described by multiple classification links.
The coding of parts is a mathematical description, and each part has an identification code, which is the part number or drawing number of the part. In order to distinguish, the identification codes of parts are unique and cannot be repeated. Among the classification codes of parts, there are classification codes, which were put forward during the implementation of group technology and can be repeated. Parts with the same classification code show that they are similar and can be classified into one category, that is, part family (group).
① Overall structure. Part classification and coding system mostly adopts tabular form, which consists of horizontal classification and vertical classification.
The horizontal classification link is called code position, which is mainly used to describe the macro information classification of parts such as type, shape, size, process elements, materials, precision, blank and so on. Its digits are between 4 and 80, and the commonly used digits are 9 to 2 1. The more code bits, the more detailed the content can be described, but the more complicated the structure.
The vertical classification link is called code domain or code value, which is mainly used to describe the hierarchical and more detailed structural information in macro information. Generally, it is 10, which is represented by numbers from 0 to 9, and the specific number of digits depends on the need.
4, group process design
Group process design is based on the classification and grouping of parts, and there are basically four methods.
(1) typical parts processing method. In a part family (group), one of the parts that can contain all the surface elements of this group of parts is selected as a representative part of this family (group), which is called a typical part or sample, and the technological process of the typical part is formulated, that is, the group technological process of this part family (group), and then the specific technological process of each part of this family (group) is generated by the group technological process through deletion and other treatments.
(2) Composite parts technology. The idea of composite parts method is to design composite parts that can represent the characteristics of a family (group) according to each family (group), and formulate the process flow of composite parts, that is, the group process flow of each part of a family (group), and then the specific process flow of each part of the family (group) is generated by processing such as deletion.
(3) Typical process route method. Select the process route of a part from the part family (group), which can include the process routes of all parts and take it as a typical group process of the part group.
(4) Composite process route method. When it is impossible to directly select a routing from each part in a part family (group) to generate a routing that includes all parts in the group, the composite routing method can be used. After the parts are grouped, the process route of each part in the part family (group) is made first, and they are combined to form an imaginary process route, which is the most complex and comprehensive, including the process routes of all parts in the group, that is, the group process route.
The main measures and benefits of flexible automation, using flexible automation, can improve the flexibility and productivity of manufacturing system and obtain economic benefits. The main measures to achieve this goal are as follows:
(1) Automatic delivery and supply of tools and workpieces.
(2) With the help of computer, the rational use of machine tools and job scheduling can be realized.
(3) Computer monitoring of manufacturing process.
(4) Preventive maintenance and overhaul of machine tools and conveying systems. Through the above measures, we can achieve:
1) Improve the utilization rate of machine tools;
2) Change the machining task without stopping the machine;
3) Multi-machine nursing;
4) man-machine separation;
5) No one runs the night shift.
Therefore:
(1) It can be processed according to the batch required for assembly, reducing the cost of work-in-process and storage;
(2) Shorten the production cycle and realize the organization of production according to the delivery date;
③ Make full use of tool life and reduce tool cost;
(4) reduce product cost;
⑤ Respond quickly to the market.