Flexible Manufacturing System

Abbreviated as FMS, it is a set of CNC machine tools and other automated process equipments. It is an organic combination of computer information control system and material automatic storage and transportation system. The flexible manufacturing system consists of three subsystems: processing, logistics, and information flow.

The flexible manufacturing system consists of a unified information control system, a material storage and transportation system, and a set of digital control processing equipment. The flexible manufacturing system can be adapted to the processing object transformation. The English abbreviation is FMS.

The process technology of FMS is based on group technology. It determines the process according to the group of processing objects, selects the appropriate NC storage equipment and the storage and transportation system for workpieces, tools and other materials, and is controlled by the computer, so it can be automatically adjusted and implemented. A batch of multiple workpieces in a range of efficient production (ie, "flexible"), and can change the product in time to meet market demand.

FMS has both the functions of processing and manufacturing and part of production management, so it can comprehensively improve production efficiency. The scope of FMS's process is continuously expanding and can include rough manufacturing, machining, assembly and quality inspection. Most of the FMS put into use in the mid-1980s were used for cutting and for stamping and welding.

The main technical and economical effect of adopting FMS is that: According to the matching needs of assembly operations, the required parts can be processed in a timely manner to achieve timely production, thereby reducing the inventory of roughs and work-in-process, and the corresponding occupation of working capital, and shortening the production cycle; Improve the utilization of equipment, reduce the number of equipment and plant area; reduce the direct labor force, under the care of a few people can achieve continuous 24-hour continuous "unmanned production"; improve the consistency of product quality.

In 1967, Mollings of the United Kingdom developed the "System 24" for the first time based on Williamson's basic concept of FMS. Its main equipment is six multi-stage CNC machine tools with modular structure. The goal is to realize continuous 24-hour day and night processing under unattended conditions, but in the end it was not completed due to economic and technical difficulties.

In the same year, White Sternstrand of the United States established the Omniline I system. It consists of eight machining centers and two multi-axis drilling machines. The workpieces are mounted on jigs in the trays, and are held in fixed intervals in the machine tool. Transfer and processing. This kind of flexible automation equipment is suitable for use in low-variety, high-volume production, and is similar in form to a conventional automatic production line, so it is also called a flexible automatic line. Japan, the former Soviet Union, and Germany also carried out the development of FMS in the late 1960s and early 1970s.

In 1976, Japanese FANUC exhibited a flexible manufacturing unit (FMC) consisting of a machining center and industrial robots, which provided an important form of equipment for the development of FMS. Flexible manufacturing unit (FMC) is generally composed of 1 or 2 CNC machine tools and material conveying devices. There are independent workpiece storage stations and unit control systems. They can automatically load and unload workpieces on the machine, and even automatically detect the workpieces. Continuous operation of finite processes can be realized. Production, suitable for many varieties of small batch production applications.

At the end of the 1970s, FMS made great progress in terms of technology and quantity. In the early 1980s, it had entered a practical stage, in which FMS consisting of 3 to 5 devices was the most, but there were also large-scale systems put into use.

In 1982, Japan FANUC built an automated motor processing plant consisting of 60 flexible manufacturing units (including 50 industrial robots) and a three-dimensional warehouse. Two automatic guided trolleys transported blanks and workpieces. Unmanned motor assembly workshops, they can run 24 hours in a row.

This automated and unattended plant is an important step towards the realization of computer-integrated automation plants. At the same time, a number of economical FMSs that only have basic features of FMS but whose degree of automation is not perfect have emerged, making the design ideas and technical achievements of FMS popularized.

A typical flexible manufacturing system consists of digitally controlled processing equipment, material storage systems, and information control systems. The processing equipment mainly uses machining centers and CNC lathes. The former is used to process box and board components, while the latter is used to machine shaft and disk components. FMS used in medium and high-volume and small-scale production often uses a machining center that can replace the headstock to achieve higher production efficiency.

The materials handled by the storage and handling system include blanks, workpieces, knives, fixtures, gages, and swarf; the methods for storing materials include flat-arranged pallet magazines, as well as ramp-type stereoscopic warehouses with large storage capacities.

The blanks are generally first loaded into fixtures on the pallets by the workers, stored in specific areas in the automated warehouse, and then sent by the automated handling system to the designated workstations according to the instructions of the materials management computer. Fixed-track trolleys and conveyor raceways are suitable for arranging the FMS of the equipment in the process sequence. The order in which the materials are automatically guided by the trolley is independent of the arrangement position of the equipment, and has greater flexibility.

Industrial robots can transport and load workpieces to and from 1 to 4 machine tools within a limited range. For larger workpieces, they are often transferred using automatic pallet exchange (APC), and robots that walk on rails can also be used to complete the workpiece. The transfer and loading and unloading.

A worn tool can be removed from the magazine one by one, or a spare magazine can replace the magazine full of the tool to be changed. The jaws of lathe chucks, special jigs, and headstocks in special machining centers can also be replaced automatically. The chip transportation and processing system is a necessary condition for ensuring the continuous and normal operation of the FMS. Generally, the economical structural scheme is selected according to the shape of the chip, the amount of removal and the processing requirements.

The structure of the FMS information control system is composed of many forms, but generally, a hierarchical system of group control is generally used. The first level is the computer numerical control device (CNC) of each process equipment, which realizes the control of each mouthwork process; the second level is the group control computer, and is responsible for assigning information such as the production plan and numerical control instructions from the third-level computer to the In the first level, the numerical control devices related to the equipment report their operational status information to the superior computer. The third level is the FMS host computer (control computer). Its function is to formulate the production operation plan and implement the management of the FMS operating status. And all kinds of data management; the fourth level is the whole plant management computer.

The well-performed software is the basis for implementing the FMS function. In addition to the system software that supports the computer work, the number is more specialized application software developed according to the use requirements and user experience, and generally includes the control software (control machine tools, material storage and transportation Systems, inspection devices and monitoring systems), 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 automatic operation of the FMS, the tool and the cutting process must be monitored. The methods that may be used include measuring the current output of the spindle motor of the machine tool or the torque of the spindle; using the sensor to pick up the broken signal of the tool; using the contact probe to directly Measure the change of the tool's cutting edge size or the workpiece's processing surface size; cumulatively calculate the cutting time of the tool for tool life management. In addition, contact probes can be used to measure machine tool thermal deformation and workpiece mounting errors and compensate accordingly.

Flexible manufacturing systems can be classified into linear, cyclic, network, and unit types based on the relationship between the machine tool and the handling system. The manufacturing system with fewer types of workpieces and less flexible requirements adopts a straight line layout. Although the processing sequence cannot be changed, it is easy to manage. The unit type has a large flexibility and is easy to expand, but the scheduling of the scheduling operation is more complicated.

In the future, the flexible manufacturing system will develop flexible manufacturing units and small-sized FMS with various technological contents; improve the automation functions of FMS; expand the operations content completed by FMS, and combine it with CAD/CAM technology. Fully automated factory development.