Under normal circumstances, only the production with single variety, large batch, special equipment, stable process and high efficiency can form 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.
First, advantages
After a group of 1 machine tools with high equipment utilization rate are incorporated into the flexible manufacturing system, the output is several times higher than that when this group of machine tools work separately.
2. Using flexible automation system to reduce WIP can reduce WIP by about 80%.
3. The production capacity is relatively stable.
4. Flexible operation
5. The product has strong adaptability.
Second, composition
1, automatic processing system
2. Logistics system Logistics system refers to a system composed of legendary belts, tracks, turntables, manipulators and other transportation devices to complete the supply and transmission of workpieces and tools. It is the main component of flexible manufacturing system.
3. Information system
4. Software system Software system is an indispensable part to ensure the effective management of flexible manufacturing system by electronic computer, 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 1000~ 100000 pieces.
Third, the type
1, Flexible Manufacturing Unit (FMC) Flexible manufacturing unit is a kind of unit with some characteristics of flexible manufacturing system developed on the basis of manufacturing unit. Usually, it consists of 1~3 CNC machine tools or machining centers, with parts buffering, tool changing and pallet automatic tool changing devices, and workpiece storage and transportation devices. It has the flexibility to process a variety of products, and can be regarded as the basic unit of FMS, and also as the smallest FMS, which is the product of the development of FMS in the direction of cheapness and miniaturization.
2. flexible automatic line A flexible automatic line is a production line consisting of a plurality of adjustable machine tools (mostly special machine tools) connected together by a mobile conveying device. 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 performance; The flexible automatic production line with high flexibility is close to the flexible manufacturing system for small batch and multi-variety production.
3.FMF Flexible Manufacturing Factory (FMF) connects multiple FMS, uses an automated warehouse and communicates with a computer system, and uses a complete FMS from ordering, design, processing, assembly, inspection, transportation to delivery. It includes job flexibility (CAD/CAM), and the flexible automation of production system is realized by computer integrated manufacturing system.
Fourth, key technologies.
1, computer-aided design
2. Fuzzy control technology The practical application of fuzzy mathematics is fuzzy controller. The recently developed high-performance fuzzy controller has self-learning function, which can continuously acquire new information and automatically adjust the control quantity during the control process, thus greatly improving the system performance.
3. Artificial intelligence, expert system and intelligent sensor technology Most of the artificial intelligence used in FMS refers to rule-based expert systems.
4. Artificial neural network technology
Flexible manufacturing system (FMS) is an automatic mechanical manufacturing system, which is composed 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 change of processing objects.
The technical basis of FMS is group technology, which determines the process flow according to the processing objects, selects the corresponding NC processing equipment and the storage and transportation system of materials such as workpieces and knives, and is controlled by computer, so it can be automatically adjusted, realize batch efficient production of various workpieces in a certain range (that is, "flexibility"), and replace products in time to meet market demand.
FMS has two functions: manufacturing and partial production management, so it can improve production efficiency in an all-round way. The process scope of FMS is constantly expanding, which can include blank manufacturing, machining, assembly and quality inspection. FMS, which was put into use in the mid-1980s, is mainly used for cutting, stamping and welding.
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.
1967, British Moleyns Company first developed "System 24" according to the basic concept of FMS proposed by Williamson. Its main equipment is six multi-process CNC machine tools with modular structure. The goal was to realize 24-hour continuous processing under unattended conditions, but it was not completed due to economic and technical difficulties.
In the same year, White Sunstrand Company built Omniline I system, which consists of eight machining centers and two multi-spindle drilling machines. Workpieces are loaded in fixtures on pallets and transported and processed between machine tools in a fixed order and at a certain rhythm. This kind of flexible automation equipment is suitable for small variety and mass production, and it is similar to the traditional automation production line in form, so it is also called flexible automation production line. Japan, the former Soviet Union, Germany, etc. FMS was also developed from the late 1960s to the early 1970s.
1976, Fanuc Japan exhibited a Flexible Manufacturing Cell (FMC) consisting of machining centers and industrial robots, which provided an important equipment form for the development of FMS. Flexible manufacturing unit (FMC) is generally composed of 1 ~ 2 CNC machine tools and material conveying devices. It has an independent workpiece storage station and unit control system, which can automatically load and unload workpieces on the machine tool and even automatically detect workpieces. It can realize the continuous production of limited processes and is suitable for multi-variety and small batch production applications.
In the late 1970s, FMS made great progress in technology and quantity, and entered the practical stage in the early 1980s. Among them, FMS composed of 3 ~ 5 devices is the most, but there are also larger systems put into use.
1982, Fanuc company of Japan built an automatic motor processing workshop, which consists of 60 flexible manufacturing units (including 50 industrial robots) and a three-dimensional warehouse, with two automatic guided trolleys to transport blanks and workpieces, and an unmanned motor assembly workshop, which can run continuously for 24 hours.
This kind of automatic unmanned workshop is an important step towards computer-integrated automation factory. At the same time, a number of economical FMS with only the basic characteristics of FMS have emerged, but the degree of automation is not perfect, which makes the design ideas and technical achievements of FMS widely used.
A typical flexible manufacturing system consists of numerical control processing equipment, material storage and transportation system and information control system. Machining center and CNC lathe are mainly used as processing equipment. The former is used to process box and plate parts, while the latter is used to process shaft and plate parts. In order to obtain higher production efficiency, machining centers with replaceable headstock are often used in FMS produced in medium, large quantities and few varieties.
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 station 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, or robots walking on the track can 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. Chip conveying and processing system is a necessary condition to ensure the continuous and normal operation of 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 process; The second stage is the group control computer, which is responsible for distributing the production plan and numerical control instructions of the third stage computer to the numerical control devices of the first stage related equipment, and at the same time reporting their operation information to the superior computer; The third stage is the main computer (control computer) of FMS, whose function is to make production and operation plans, manage the running state of FMS and manage all kinds of data; The fourth level is the management computer of the whole factory.
Software with perfect performance is the basis of realizing FMS function. In addition to the system software supporting computer work, there are more specialized application software developed according to the use requirements and user experience, generally including control software (control machine tools, material storage and transportation systems, inspection devices and monitoring systems) and planning management software (scheduling management, quality management, inventory management, tooling management, etc.). ) and data management software (simulation, retrieval and various databases).
In order to ensure the continuous and automatic operation of FMS, it is necessary to monitor the tool and cutting process. Possible methods include: measuring the current output power of the spindle motor of the machine tool or the torque of the spindle; Pick up the tool breakage signal with a sensor; The contact probe is used to directly measure the change of the cutting edge size of the tool or the machined surface size of the workpiece; Accumulate and calculate the cutting time of tools, and manage the tool life. In addition, the contact probe can also be used to measure the thermal deformation of the machine tool and the installation error of the workpiece, and make corresponding compensation.
According to the relationship between machine tools and handling systems, flexible manufacturing systems can be divided into linear, circular, network and unit types. Most manufacturing systems with few kinds of workpieces and low flexibility requirements adopt linear layout. Although the processing order cannot be changed, it is easy to manage. The unit type is flexible and easy to expand, but the program design of scheduling job is more complicated.
Flexible manufacturing system will develop flexible manufacturing cells and small FMS with various technological contents in the future; Improve the automation function of FMS; Expand the work content completed by FMS and combine it with computer aided design and manufacturing technology (CAD/CAM) to develop into a fully automatic factory.