With the continuous development of science and technology, manufacturing enterprises have also experienced several changes, from the actual development point of view, each change has brought a significant improvement in the level of manufacturing, reflecting the leading role of science and technology, the study believes that manufacturing enterprises to intelligent development roughly through the following four stages: manual operations→ automated assembly operations→ digital network operations→ networked intelligent operations.
From the perspective of historical development law, with the continuous progress of science and technology, the change of manufacturing enterprises is also an inevitability, from the perspective of a large development cycle, the research believes that the current development of manufacturing enterprises is in the third stage of digital network operation development period, that is, the stage of deep integration of informatization and industrialization, and is initially exploring networked intelligent operations.
1 Digital factory concept
Digital factory is with the development of digital simulation technology and virtual reality technology, which realizes the optimization and improvement of factory product development, manufacturing production and service through virtual planning and simulation optimization of real industrial production, which is the application embodiment of modern industrialization and information integration. With the continuous change of product demand, the speed of product cycle upgrading, and the continuous application of emerging information technologies such as 3D printing, Internet of Things, cloud computing, and big data, in order to shorten the research and development cycle, reduce production costs, and improve the quality and efficiency of enterprise products, advanced manufacturing enterprises have begun to pay more and more attention to the construction of digital factories, such as SAIC, Haier, Huawei, Siemens and other manufacturing enterprises have begun to build their own digital factories to support enterprises to achieve new breakthroughs and development.
As the best combination of informatization and industrialization, it is of great significance to study how to build digital factories and how to achieve seamless connection between virtual design and physical equipment, which is of great significance to drive the deep integration and development of informatization and industrialization and the development of smart factories in the future. The digital factory has broad and narrow concepts, and the content involved varies according to the perspective of the analysis.
This paper digital factory combined with the actual situation of domestic discrete manufacturing enterprises (such as weapons, aerospace and other fields of some manufacturing enterprises), is based on the core manufacturing enterprises in the generalized digital factory, while meeting their own production and management tasks, they need to have product research and development capabilities and after-sales service guarantee capabilities, so the "digital factory" in this paper is not only the concept of production, it is extended forward to design, backward to service, while covering enterprise management, including product development and design process, manufacturing process, The whole life cycle of products such as enterprise management process and service assurance process.
2 Digital factory architecture
The planning, construction, operation, optimization and improvement of digital factories is the process of deepening the integration of enterprise informatization and industrialization. In this process, the digital world and the physical world continue to iterate, supporting the continuous improvement and enhancement of the PDCA cycle in various links such as product design, manufacturing, and operation management. The digital factory construction architecture of this paper is constructed from two dimensions: product life cycle and system level, and realizes the interactive iteration between the digital world and the physical world.
1) Product life cycle: a chain collection composed of a series of interrelated value creation activities such as product design, process planning, manufacturing, and service assurance. Activities in the life cycle are interrelated and influence each other.
2) System hierarchy: This paper proposes a four-layer structure of the digital factory construction system hierarchy from bottom to top:
(1) Equipment resources and control layer: including sensors, instrumentation, bar codes, radio frequency identification, machines, machinery and devices, as well as electricity, gas energy facilities and other hardware equipment, as well as programmable logic controller (PLC), data acquisition and monitoring control system (SCADA), distributed control system (DCS) and fieldbus control system (FCS) and other control systems closely related to hardware equipment, which is the technical basis for production activities of enterprises.
(2) Database layer: including design, process, manufacturing, management, test, standard system library (including digital management standards, test and test standards, design standards, STEP standards (product information exchange standards)), etc. Each type of database has its own basic database and knowledge base. As the second layer of the digital factory system framework, it provides the most basic data support for the digital factory.
(3) Management: including product data management (PDM) for the design department, process tooling management for the process department, manufacturing execution system (MES) for the production department, energy management system for the logistics department, etc.
(4) Collaboration layer: including product lifecycle management (PLM), enterprise resource planning system (ERP), supply chain management system (SCM) and customer relationship management system (CRM), etc., and through the Internet to share information to achieve collaboration between various departments within the enterprise and collaboration between different enterprises in the industrial chain. The schematic diagram of building the two-dimensional system architecture of the digital factory from the product life cycle and system level is shown in Figure 1.
Figure 1 Schematic diagram of the two-dimensional system architecture of digital factory construction
3 Three core functional elements and three key technologies for digital factory construction
3.1 The three core functional elements are interconnection, system integration, and data information integration
1) Interconnection: The core of the digital factory is connection, which closely connects equipment, production lines, factories, suppliers, products, and customers. The digital factory adapts to the development trend of the Internet of Everything, and forms a network of ubiquitous sensors, embedded terminal systems, production testing equipment, and information systems through information systems, so that production equipment, equipment and products, and digital world (virtual world) and physical world can be interconnected, so that machines, working parts, systems and people continue to maintain digital information exchange through the network.
(1) Interconnection between production equipment. The interconnection between production equipment is the interconnection of stand-alone equipment, the interconnection of stand-alone equipment of different types and functions constitutes a production line, the interconnection between different production lines constitutes a digital workshop, the interconnection of a digital workshop constitutes a digital factory, and the interconnection of digital factories in different regions, industries and enterprises forms a digital manufacturing system alliance with ubiquitous manufacturing capabilities.
(2) Interconnection of equipment and products. The ability to communicate between the product and the production equipment allows the operator to know at all times what stage the product is currently in and what will be done next, as well as when the product will be manufactured.
(3) The interconnection of virtual and reality. Connect physical devices to the Internet through information means, so that physical devices have functions such as computing, communication, control, and remote collaboration, so as to realize the integration of the virtual network world and the real physical world.
2) System integration: The digital factory forms a network of physical equipment such as sensors, embedded terminal systems, control systems, production and processing detection through information means, so that people and people, people and equipment, equipment and equipment, and services and services can be interconnected, so as to realize horizontal integration, vertical integration, and end-to-end integration of the future value chain.
(1) Horizontal integration: refers to a kind of resource integration realized by enterprises through information networks, including networking between production line equipment and equipment, between production lines and production lines, between workshops and workshops, and between factories and factories, which is the physical basis for realizing digital factories. It is also the basis for the future sharing of resources between enterprises.
(2) Vertical integration: refers to the integration of internal information flow of the enterprise, the use of unified database and software platform to manage equipment resource data and production process data, product data and other information, so that the interoperability of major equipment and key information consistency is solved, data or information can be top-down and bottom-up effective flow, thereby laying the foundation for the next big data analysis and advanced intelligent decision-making.
(3) End-to-end integration of the value chain: refers to the creation of the value chain around the whole life cycle of the product, and realizes the management and service of the whole life cycle of the product from product design, manufacturing, logistics and distribution, use and maintenance through the integration of different enterprise resources in the value chain. It integrates the entire cycle of analyzing the needs of the product manufacturer, obtaining orders, supply chain and manufacturing, logistics delivery, revenue acquisition, after-sales service and obtaining new orders.
3) Data information integration: On the basis of system integration and communication, the use of cloud computing, big data and other new generation information technology, under the premise of ensuring information security, to achieve collaborative sharing of data information, mainly including the following three types of data information:
(1) Product data information: including data information at all stages of the product life cycle. All kinds of data information of products are transmitted, processed and processed, making product life cycle management possible, personalized services possible, product management throughout its life course, and users able to participate in various activities of product design and processing.
(2) Operation data information: including the data of the production line and production equipment within the enterprise, which can be used to monitor the equipment itself in real time and feed back to the production process, so that the production control and management are optimized; It also includes external data of enterprises such as economic operation, industry, market competitors, etc., through the data collection and analysis of procurement, warehousing, sales, distribution and other supply chain links, it can reduce inventory, dynamically adjust production, improve and optimize the supply chain.
(3) Industry chain data information: including customers, suppliers, partners and other data information. By understanding the data information of competition factors in each link of the industrial chain such as technology development, production operations, procurement and sales, internal and external logistics, it provides information for enterprise managers and participants to view the value chain, so that enterprises have the opportunity to transform more links in the value chain into strategic advantages of enterprises.
3.2 The three key technologies are modeling technology, simulation technology and single data source technology
1) Modeling technology: The biggest feature of the digital factory is that product design and production can be carried out virtually in the digital space, so that not only the feasibility of product design can be simulated and verified, but also the manufacturability and manufacturing cost estimation analysis of new products can be carried out in advance. In order to realize the above functions, it is first necessary to establish a digital model based on various elements of model definition technology (MBD technology), and this paper divides the digital factory element model into seven parts according to function: product design, factory layout, process planning, production simulation, virtual assembly, test verification and energy management on the basis of the 6 types of models proposed by Cai Min et al., as shown in Figure 2.
Figure 2 Schematic diagram of the functional model of the digital factory
2) Simulation technology: simulation optimization is the core value of the digital factory, according to the established digital model and simulation system to give simulation results and various prediction data, analyze various problems and potential optimization solutions that may occur in the digital factory, and then optimize product design and production process. In the digital factory manufacturing process, the application of simulation technology mainly includes: simulation for product design, including the static and dynamic performance of products; Simulation for manufacturing process includes machining process simulation, assembly process simulation and inspection process simulation; Simulation for other parts of the enterprise includes manufacturing management process simulation, as well as factory/shop floor layout, production line layout simulation, etc.
3) Single data source technology: In the whole life cycle of the product, there are various data file lists (BOMs) for different departments and purposes, and the idea of a single data source is to carefully organize different data into a logical single data source, and establish strict constraints, so as to effectively solve the problem of data redundancy and data inconsistency between different departments. In the whole life cycle of the product, according to the stage and department of data generation can be divided into design BOM, process BOM, manufacturing BOM, procurement BOM, sales BOM, service BOM and other data, each data BOM is uniquely determined by the product type, application field and product life cycle, of which the design BOM belongs to the most original BOM file, can be regarded as the single data source of the product, which condenses the creative work of product design engineers, Various other BOMs are converted on its basis and combined with information from their application fields.
4 Digital factory construction content
This paper proposes to divide the digital factory construction content into four parts: R&D design digitalization, production and manufacturing digitalization, enterprise management digitalization, and support and guarantee digitalization, and the schematic compass diagram is shown in Figure 3.
Figure 3 Block diagram of digital factory construction
4.1 Digitalization of R&D design
Product R & D personnel design products according to needs, obtain relevant data and three-dimensional models of products, and carry out management optimization and improvement until the final product design scheme is determined. It mainly includes three stages: product design, process planning and virtual test verification. Among them, product design focuses on the construction conditions of digital product models or principle prototypes and the digital verification methods of product performance and functions, mainly including computer-aided design (CAD), computer-aided engineering analysis (CAE), computer-aided operation (CAO, including knowledge base, basic database and expert system, etc.).
Process planning focuses on the construction of computer-aided product process planning and tooling design, computer-aided process dynamic simulation and analysis optimization, special process equipment optimization design and other conditions, mainly including computer-aided process planning (CAPP), computer-aided tooling design, reverse engineering (RE, such as rapid prototyping systems), digital process simulation and verification (including dynamic assembly simulation, assembly process simulation, human-machine process simulation, welding process simulation, stamping process simulation, machining process simulation, assembly accuracy and tolerance simulation, etc.), as well as line layout and simulation, station layout and simulation, logistics simulation, etc. Virtual test verification focuses on establishing virtual test and verification (VT&E) conditions, that is, establishing a digital environment with virtual prototype as the standard to simulate the real physical test process, and conducting one or more virtual test tests, and making reasonable analysis of the data obtained through the test to assess and evaluate the performance of complex products, and then provide solid support for physical verification; and the establishment of a test data management system (TDM) for virtual test data and real test data management.
4.2 Digitalization of manufacturing
Involving the whole process from the beginning of feeding to the final completion of the product, the digitalization of production and manufacturing can realize the optimization, monitoring and management of the production process to improve manufacturing quality and efficiency. It mainly builds the following four aspects.
1) The digitalization of manufacturing resources mainly includes the digital transformation of existing equipment and the introduction of advanced CNC intelligent equipment. The digital transformation of existing equipment is mainly through the use of PLC, CNC (computer numerical control system) system and other digital peripherals to replace and upgrade the original machine tool electrical system. The introduction of advanced CNC intelligent equipment includes the purchase of CNC machining equipment (turning-milling compound automatic processing units, etc.), industrial robots (welding robots, etc.).
2) The digitalization of the production process takes the manufacturing execution system (MES) as the core, including computer-aided manufacturing (CAM), rapid prototyping (RPM), and distributed numerical control (DNC) network integration, digital detection, production scheduling command center, etc.
3) Quality control digitalization focuses on the construction of computer-aided quality management (CAQ), computer-aided testing (CAT) and other means. The digitalization of quality control in the production and manufacturing process needs to be considered in conjunction with the quality control in the digitalization of enterprise management. This part of the construction focuses on quality inspection and control in the production and manufacturing process, focusing on solving through the MES system.
4) The digitalization of material control focuses on the establishment of logistics control conditions such as automated warehouses, automatic distribution transmission devices (AGVs), and public resource positioning, so as to realize the automation, digitalization and intelligence of the logistics process.
4.3 Digitalization of enterprise management
Use information technology and management technology in the field of enterprise management to improve the level of enterprise management and business efficiency. It includes two parts: the digitalization of intra-enterprise management and the digitalization of inter-enterprise management.
1) Enterprise management digitalization Establish a product-oriented PLM and an ERP enterprise management digital framework with material flow as the main line, assist the corresponding office automation OA, quality information system QIS, test data management system TDM, product data management PDM (TDM and PDM system focus on product development and design digitalization stage), contract management system, human resource management system, financial management system, equipment management system, knowledge management system, enterprise portal platform, Data decision-making support system and other conditional means.
2) Inter-enterprise management digitalization On the basis of the digitalization of intra-enterprise management, the digitalization of related businesses, processes and shared resources between enterprises is further realized, so that enterprises have the ability to participate in supply chain digital management and agile manufacturing. Focus on the construction of supply chain management system SCM, customer relationship management CRM, and e-commerce intelligent BI and other content.
4.4 Support and ensure digitalization
As the supporting conditions of the digital factory, it is the supporting environment and operating conditions of the digital factory, which needs to be carried out synchronously with the digital conditions of product development, manufacturing, and enterprise management. It mainly constructs the following six aspects.
1) Infrastructure: (1) Network foundation: including remote network construction and local LAN construction, remote network construction includes network construction between different enterprises and different locations of the enterprise. Local LAN construction currently includes confidential networks, industrial Internet (also known as Internet of Things, including energy Internet), Internet and so on. (2) Data center/disaster recovery center: including computer room construction, hardware servers for R&D, production and management of various application systems, high-performance computing cluster systems, and data storage and backup software and hardware configurations. (3) General control center: the information center of the digital factory, the information system reflecting the operation status of the enterprise is centrally monitored and managed in the general control center, so as to realize the synchronous improvement of information system management efficiency and management quality.
2) Database and standard specifications: database construction according to the needs of product development, the establishment of design, process, manufacturing, testing and other links of product special database, as well as relational database, file database, real-time database and other general commercial database systems, such as Oracle database, SQL Server database, and database management system. The construction of standards and specifications is based on the national informatization related standard system, according to the company-level informatization standard system, establish a digital factory standard system library (including digital management standards, testing and testing standards, design standards, product information exchange standards, etc.). The construction of the standard and specification system has a strong customized nature, and there is no ready-made fixed mode of commercial software.
3) Information security: ensure the stable operation of network security, focusing on the construction of information security protection systems such as physical security, information security, operational security and confidentiality management for secret-related networks; Build industrial firewall IFW, industrial communication gateway, industrial control network security monitoring and auditing system, security monitoring platform, industrial control network security defense platform, industrial information security online monitoring and early warning platform, industrial Internet trusted computer active immunization platform for industrial Internet.
4) Energy security: with the construction of the energy Internet as the information operation carrier, combined with the virtual simulation of the energy management model, through the construction of the energy management system EMS, the comprehensive use of computer technology, database technology, network technology, instrument control technology, the detailed use of various energy (power supply, water supply, gas supply, heating, etc.) required for digital factory operation online monitoring, dynamic analysis, real-time control of energy consumption, in order to find energy consumption weaknesses in time, dynamic energy adjustment, to achieve "real-time measurement", " Data Processing" and "Remote Control" and other functions.
5) Service guarantee: the rear technical support personnel should use remote communication technology to guide the equipment operation or maintenance personnel in front to eliminate the fault of the equipment and quickly restore the performance of the equipment; The focus includes remote diagnosis and maintenance services (such as building a remote diagnosis system with maintenance support machines), visual maintenance services (such as building interactive electronic technical manuals IETM), maintenance knowledge services (such as training, or company portal), portable maintenance auxiliary equipment, maintenance service management, etc.
6) System integration: By building a digital factory integration support platform for R&D design, manufacturing, and operation and management (the use of software interface APIs and protocols can make various software systems have interoperability), effectively support the integration of all stages of the digital factory, so that the functional systems of the enterprise work together. From the current development trend, the study believes that R&D-based enterprises can establish an integrated platform with PDM as the core, manufacturing as the core enterprises can establish an integration platform with ERP+MES as the core, and R&D and manufacturing hybrid enterprises can establish an integrated platform with PLM as the core to realize the integration of product life cycle.
5 Concluding remarks
Digital factory construction is a comprehensive and systematic project that affects the entire enterprise and its supply chain ecosystem. The interconnection, system integration, data information integration and product life cycle integration to be realized by the construction of digital factories connect people, equipment, products and environmental elements in all aspects, digital, data and information are everywhere, and decisions and actions are distributed to employees at all levels of the enterprise. Therefore, the construction of digital factories, in addition to facing technical challenges, faces more management challenges such as organization, culture, process and human resources, and especially requires enterprises to strengthen the cultivation of compound information talents.