The machine tool networking project is to build a workshop level distributed control network at the equipment level (CNC machine tool), collect machine tool data and other production data in real time, realize the effective management of CNC programs and related production factors (part drawings, processing technology, tool holder and measuring tool list, etc.), and realize the visual display of machine tool status, etc., which will lay a good foundation for the effective establishment of the next MES platform, Therefore, it is implemented first.
Overview of machine tool networking project
The implementation of the machine tool networking project provides technical support for the effective management and control of the equipment level. As the information of the underlying equipment, it is the basic means of implementing digital manufacturing, the foundation of the company’s implementation of digital manufacturing technology, and plays an important role in the construction of the company’s digital chemical plant.
The machine tool networking project generally includes four systems: DNC (distributed numerical control network) system, MDC (manufacturing data collection) system, NC (numerical control digital control for short) program management system and visual data display system.
（1） The core function is DNC (distributed numerical control network) system. DNC system is a system for intelligent networked management of production equipment and stations. The DNC system adopted in the machine tool networking project has given a deeper and broader meaning than the traditional industrial DNC (program transmission): it can not only network all CNC CNC processing equipment, but also manage the PLC work center of the automatic production line and all other common stations and measuring stations.
The network connection scheme adopted by the DNC System: each CNC equipment in the workshop is equipped with a “serial port networking device”. Through the serial port networking device in each CNC equipment, the program transmission data stream, barcode transmission data stream and MDC signal feedback data stream of the CNC equipment are summarized into a TCP / IP protocol data transmission line, and then summarized into the company’s intranet through the internal light cabinet in the workshop. Advantages of the scheme: regardless of the distance between the CNC equipment, the most direct network wiring method can be used to solve the problem no matter how far the equipment is separated, and the transmission is stable. It is suitable for enterprises with discrete workshop equipment. The DNC server can also be far away from the workshop site. Disadvantages of the scheme: each serial port networking device needs to be equipped with an IP address, which wastes network IP resources.
The barcode use scheme adopted by the DNC System: each CNC equipment is equipped with a barcode gun, and the operator can call the program by scanning the barcode with the barcode gun at the machine tool end. The method is to add the corresponding barcode next to the program name (the program name is associated with the task information such as parts and processes) on the existing dispatch list. During the production process, the equipment operator scans the bar code with the bar code scanning gun according to the actual situation. The scanned command can be transmitted to the server through the DNC network. At this time, the server will automatically send the relevant programs and production factors (part drawings, processing technology, tool holder and measuring tool list, etc.) to the field equipment. At this time, the field operator only needs to press the “receive” button on the equipment control system.
（2） MDC system is a set of flexible methods to collect real-time status data (including equipment, personnel and production tasks) on the production site, store them in databases such as access, SQL or Oracle, and based on the advanced lean manufacturing management concept, A system that intuitively reflects the detailed manufacturing data and production status of the workshop at present or in a certain period of time in the past through reports and charts.
The MDC system helps the production department of the enterprise to make scientific and effective decisions and help the enterprise to improve the production process by providing real workshop data reports and charts to decision makers.
The entire system network of MDC system solution is based on DNC and TCP / IP network of machine tool networking project. The system adopts a variety of production data collection methods: standard bar code collection, equipment PLC automatic data collection, and international standard OPC interface automatic collection.
The MDC system can monitor the real-time working status of the machine tool (including clamping, debugging, processing, shutdown, idle, etc.) through the production data collected in real time, and generate a graph report to facilitate the scheduling personnel to arrange the production plan; Analyze and generate reports on productivity, working time, equipment utilization rate, production trend and production plan execution, etc., to help decision makers responsible for production and equipment management answer many difficult problems in field manufacturing, thus helping to improve and optimize the production process.
（3） NC (numerical control) program management system.
The NC program management system can realize the management of NC program preparation, uploading, review, proofreading, approval, version upgrading, overwriting and renaming, backup, processing site call and other processes. In addition, the system can also centralize the management of the NC program and its documentation to better ensure the synchronization of the two. The production factors (part drawings, processing technology, tool holder and measuring tool list, etc.) can be centrally managed, safely stored, shared by departments and easily consulted. Lay a foundation for paperless management of workshop process, eliminate or reduce some paper document management, and improve efficiency.
（4） Visual data display
Based on the realization of real-time data collection of machine tools, the three-dimensional modeling of machine tools in the workshop is carried out to display the status of machine tools in real time. By dynamically browsing this interface, the user can easily understand the production status of the whole workshop, locate a specified equipment, and query the production details of this equipment.
The workshop is also equipped with display equipment such as large screen and touch screen to display the equipment status, machine tool startup rate and part completion rate in real time. The touch screen industrial control computer configured next to each CNC equipment can also be used as a supplementary and standby means for data collection of MDC system. The equipment operator can also use it to query whether the on-site data feedback is correct or not, and use it to query and browse the processing operation instructions (procedures, drawings, tool lists, clamping diagrams, etc.) in a paperless manner on the site.
Application system integration
As a highly business management system, MES (Manufacturing Execution System) needs numerous data support from the bottom. All field related data such as work orders, parts, processes, equipment and personnel are first collected through the integration of dnc-mdc system to obtain the real data related to field production. The data are customized classified and summarized through various integration methods and finally fed back to MES.
During integration, dnc-mdc system will receive production tasks from MES system. When a new production task is identified, the new production task and the corresponding part information and process information are first established in the dnc-mdc system, and then sent to the site in the form of work order (work order). Finally, the equipment operator scans the bar code on the work order to realize the NC program call and task tracking, and feed back the progress of the task to the MES in real time (for example, the actual start and end time of the work order and other data).
Implementation difficulties
The NC program is complex and diverse: the main production mode is to take the workshop processing personnel as the production center, supplemented by the technical development department. Almost all NC program management takes place on the workshop site. This leads to a large number of NC programs stored in the machine tool. The new and old products of our company overlap alternately, which also leads to the complexity and diversity of NC programs in the machine tool. Only the processing personnel know the processing content of each program.
To sum up, the management scheme adopted by the machine tool networking project is to file all NC programs in the field equipment to the NC program management system server through the DNC network for effective management. Therefore, three management measures are proposed:
1. NC program naming must comply with the NC program naming rules uniformly formulated by the company.
2. Add the standard name of the NC program to the internal remarks of the program, so that when the program is processed and sent back to the DNC server for backup and unified management, the DNC system will automatically save the standard name of the remarks.
3. On the basis of completing the first two measures, the NC program solidified in the field NC equipment shall be backed up and exported step by step. It is managed and deployed by the NC program management system.
The implementation of the machine tool project has achieved the following objectives:
1. DNC System: a distributed control network covering the machining workshop is established to realize the effective calling, stable and effective transmission and online processing of NC programs, and the effective transmission of tool compensation parameter files from the tool setter to the machine tool.
2. MDC system: realize the effective collection of real-time data of CNC machine tools and other production data, and provide the collected data to the decision-makers for reference and analysis in the form of reports or statistical charts. The data collected at the same time can effectively guide the production scheduling and management of MES platform in the future.
3. NC program management system: it realizes unified process management of NC programs and unified management of NC programs and their associated production element files in the system.
4. Visual data display: on the basis of realizing the data collection of machine tools, the three-dimensional modeling of the machine tools in the workshop is carried out, and the equipment status, equipment startup rate, part completion rate, etc. are effectively displayed through the on-site display screen, the touch screen beside the CNC equipment and the PC terminal of the relevant management personnel.
To sum up, the construction of the machine tool networking project is the basis for the implementation of digital manufacturing technology and plays a pivotal role in the construction of digital chemical plants.