Abstract: This paper describes the meaning, composition and development of virtual manufacturing technology, analyzes the machining process simulation which plays an important role in virtual manufacturing, and proposes the system structure, development status and existing problems of machining process simulation, and discusses turning. Process simulation and its possibilities for implementation.
Keywords: virtual manufacturing; turning process simulation; physical simulation
1 Introduction
The development of manufacturing industry has continuously put forward new requirements for product performance, specifications and varieties. The life cycle of products is getting shorter and shorter, and the development time of new products is the decisive factor. VMT Virtual Manufacturing Technology can simulate the entire process from product design, manufacturing to assembly, analyze and predict problems that may arise during the design and manufacturing process, and propose improvements to achieve the entire process from development to manufacturing. Optimize to achieve the goal of reducing product life cycle, reducing development risks and improving economic efficiency. The machining process simulation plays an important role in virtual manufacturing. It effectively creates and optimizes the various processing information in the process system composed of machine tool-workpiece-tool, which creates favorable conditions for the intelligent realization of the actual machining process. At the same time it is also an important means of studying the processing.
2, virtual manufacturing technology
2.1 The composition of the virtual manufacturing system From the perspective of product development, virtual manufacturing is actually a complete simulation of the entire process from design to manufacturing and assembly on the computer, running through the entire life cycle of the product. Virtual manufacturing consists of the following five phases:
The conceptual design phase includes kinematic analysis and kinematics simulation of the product.
â— The detailed design stage refers to the simulation of the entire machining process of the product, including the geometric simulation process for verifying the geometric parameters and interference of the workpiece, the physical simulation process for predicting and analyzing various physical parameters during the machining process, and the product. Assembly process simulation.
â— Processing and manufacturing stages include plant design, manufacturing shop design, production planning and operation planning, and design of controllers at all levels.
â— Test the realness of the simulator.
â— Training and maintenance phase training simulator, including the training process for operators and 2D maintenance of products.
Virtual manufacturing can be divided into the following levels of work: factory level, workshop level, scheduling level, specific processing and various manufacturing units. Therefore, virtual manufacturing technology can simulate the entire production activities of existing enterprises, and can simulate the design of equipment layout and logistics system of future enterprises, and work at all levels of production and manufacturing to shorten the product life cycle and improve design and manufacturing efficiency. Best purpose.
2.2 Development of Virtual Manufacturing Technology As a manufacturing technology for the 21st century, VMT has attracted the attention of scholars at home and abroad since its inception. The current research focus is mainly on the theoretical research of this technology and the attempt to construct and practice the simulation environment at all levels. Theoretical research includes the discussion of the VMT/VMS concept, the composition of the virtual manufacturing system, the composition of the model in the whole system, the modeling method and the integration of the model. In terms of practical experiments, the design of virtual factories and virtual workshops and the scheduling and information processing of various equipments at the factory level and workshop level, and the simulation of each specific processing process and processing unit are realized from the laboratory perspective. At the same time, some companies have already carried out VMT work and achieved results.
In China, VMT technology has also received great attention. The model modeling method, production process simulation, control and other aspects have done a lot of research work. At the same time, neural network and artificial intelligence technology are introduced into the VMS process, and a virtual factory-level and workshop-level design and scheduling system is established, such as Tsinghua University's "Factory Scheduling Simulation Environment FASE" for manufacturing shop scheduling problems, "Integrated Manufacturing System Software IMSS" and "Processing Process Simulator MPS" for manufacturing shop design, analysis modeling and simulation.
3. Mechanical process simulation
3.1 Current Status and Existing Problems of Machining Process Simulation There are two main situations in the current machining process simulation: one is to simulate the change process of various factors within a specific cutting process from the perspective of metal cutting, and study its cutting. Mechanism for production and research applications; the other is to process process simulation as part of the system, with a focus on constructing a complete virtual manufacturing system. The simulation methods of the two methods are the same, that is, the continuous change model is first established for the machine-added process system, and then the continuous model is discretized into discrete points by mathematical discrete method, and the machining process is simulated by analyzing the physical factors of these discrete points. .
Since the machining process simulation is still in its infancy, the following problems still exist:
(1) The simulation has few processing forms, and the research scope is narrow. Among the many types and forms of cutting processing, the current simulation mainly focuses on milling and grinding. Even in these two processing methods, the simulation is limited to a narrow range. For example, milling is mostly a simulated rod milling cutter and an end milling cutter, and this simulation system can't do anything for other kinds of milling cutters (such as milling cutters for forming surface). The reason is that there are many kinds of machining, there are many processing forms such as car, milling, planing, grinding, boring, etc. On the other hand, the machining theory is complex, and the processing models of different machining methods and tool shapes are quite different. At the same time, most of the current simulation systems carry out geometric simulation, that is, the tool path trajectory, the interference check of the workpiece and the tool, etc., which is called NC Verification. However, in the machining process, geometric verification is only a prerequisite, and more important are the physical forces that determine the factors in the cutting process, such as cutting force, tool vibration and tool wear.
(2) The physical simulation process considers the ideal cutting state and has a large gap with the actual cutting process. In the current simulation system, a large number of hypothetical factors are pre-set, such as setting the process system rigidity to meet the requirements, no vibration; processing material structure Uniform, no hard spots and other defects; no wear and tear on the tool; no change in cutting elements. This assumed ideal state cannot take into account random disturbances during the cutting process, such as material changes caused by hard spots of the workpiece, changes in depth of cut caused by vibration, etc., so that the simulation system cannot truly reflect the actual cutting process.
(3) Simulation means to limit the development of simulation system The development of computer technology is closely linked with the simulation technology. In the past, due to the limitation of computer hardware and software, the simulation time is very long. The coding workload is large, the program is readable and the maintenance is poor, which brings difficulties for the simulation work. At present, the application of C++ language and object-oriented method development simulation system has become a development trend.
The above problems have attracted the attention of researchers. The future machining simulation system will develop in the direction of fast operation, facing multiple processing forms and more in line with actual conditions.
3.2 The structure of the machining process simulation system In the virtual manufacturing process, the detailed design phase of the product is actually the simulation of the mechanical machining process of the product, that is, the analysis of various information in the process system composed of the machine tool-workpiece-tool. Forecast, it includes both geometric simulation and physical simulation. Geometric simulation includes tool path trajectory verification, interference check of workpieces with machine tools and tools. Physical simulation includes analysis and prediction of various physical factors, including cutting force, tool wear, cutting vibration, cutting temperature, workpiece surface roughness, etc. . At the same time, geometric simulation, physical simulation and its various elements have a close relationship, such as tool path trajectory and interference, cutting force directly affects vibration, workpiece surface quality, tool wear and so on.
3.3 Research Objectives and Methods of Numerical Control Turning Process Simulation Turning processing is one of the most widely used processing methods at present. Therefore, it has important theoretical research and practical application value for the simulation of CNC turning machining process.
The turning simulation will simulate and predict the changes of geometric and physical factors in various machining operations such as outer circle, end face, chamfer, thread and curve, and establish a simulation system for turning machining. . The simulation system should have the following features:
(1) Establish a perfect CNC turning simulation system for CNC lathes, provide reliable and optimized NC code for the actual production process, and realize intelligent processing of turning.
At present, the application of CNC lathes and economical CNC lathes in China is becoming more and more popular. It is very practical to get a reliable and optimized NC code before processing. In the past, NC codes were often verified in a trial-and-error manner. This method was time-consuming and labor-intensive. On the other hand, the materials used for trial cutting were often made of wood and plastic, so that although the accuracy of the NC code in geometric information can be verified, The key physical factors such as cutting force, vibration, and surface quality of the workpiece during the cutting process are unknown. The turning simulation system can solve the above problems. At the same time, some parameters in the NC code are modified to further reduce the cutting force, improve tool durability and productivity, and optimize the NC code. In this way, the NC code can be confirmed for practical processing applications, so that the simulation system has the ability of self-learning and adjustment, and the flexibility of the simulation is improved to achieve the purpose of intelligent processing.
(2) Establish a simulation system for the actual machining process, comprehensively consider various interference factors in the actual machining, so that the simulation process highly reflects the actual production process.
In the actual processing process, the process system is subject to various factors and influences, and the physical quantities related to cutting also change due to changes in various cutting conditions. Therefore, in order to be able to realistically simulate the machining situation in the turning process, the turning simulation system should fully consider these actual changes and random disturbances, so that the simulated physical quantities are really close to the actual situation. These influencing factors mainly include cutting vibration caused by machine rigidity and cutting force or workpiece eccentricity. The workpiece structure is not uniform with random interference caused by hard spots, the change of cutting amount during cutting and the influence of tool wear on the cutting process.
(3) Because of the process of verifying and optimizing the NC code, the simulation system can greatly avoid various abnormal phenomena that may occur during the actual machining process, simplify the detection and diagnosis equipment in the actual machining process, and improve the processing safety and Economic benefits. At the same time, the simulation system can realistically simulate the turning process, and can be used as a soft machine tool for training and maintenance of CNC machine tools.
Keywords: virtual manufacturing; turning process simulation; physical simulation
1 Introduction
The development of manufacturing industry has continuously put forward new requirements for product performance, specifications and varieties. The life cycle of products is getting shorter and shorter, and the development time of new products is the decisive factor. VMT Virtual Manufacturing Technology can simulate the entire process from product design, manufacturing to assembly, analyze and predict problems that may arise during the design and manufacturing process, and propose improvements to achieve the entire process from development to manufacturing. Optimize to achieve the goal of reducing product life cycle, reducing development risks and improving economic efficiency. The machining process simulation plays an important role in virtual manufacturing. It effectively creates and optimizes the various processing information in the process system composed of machine tool-workpiece-tool, which creates favorable conditions for the intelligent realization of the actual machining process. At the same time it is also an important means of studying the processing.
2, virtual manufacturing technology
2.1 The composition of the virtual manufacturing system From the perspective of product development, virtual manufacturing is actually a complete simulation of the entire process from design to manufacturing and assembly on the computer, running through the entire life cycle of the product. Virtual manufacturing consists of the following five phases:
The conceptual design phase includes kinematic analysis and kinematics simulation of the product.
â— The detailed design stage refers to the simulation of the entire machining process of the product, including the geometric simulation process for verifying the geometric parameters and interference of the workpiece, the physical simulation process for predicting and analyzing various physical parameters during the machining process, and the product. Assembly process simulation.
â— Processing and manufacturing stages include plant design, manufacturing shop design, production planning and operation planning, and design of controllers at all levels.
â— Test the realness of the simulator.
â— Training and maintenance phase training simulator, including the training process for operators and 2D maintenance of products.
Virtual manufacturing can be divided into the following levels of work: factory level, workshop level, scheduling level, specific processing and various manufacturing units. Therefore, virtual manufacturing technology can simulate the entire production activities of existing enterprises, and can simulate the design of equipment layout and logistics system of future enterprises, and work at all levels of production and manufacturing to shorten the product life cycle and improve design and manufacturing efficiency. Best purpose.
2.2 Development of Virtual Manufacturing Technology As a manufacturing technology for the 21st century, VMT has attracted the attention of scholars at home and abroad since its inception. The current research focus is mainly on the theoretical research of this technology and the attempt to construct and practice the simulation environment at all levels. Theoretical research includes the discussion of the VMT/VMS concept, the composition of the virtual manufacturing system, the composition of the model in the whole system, the modeling method and the integration of the model. In terms of practical experiments, the design of virtual factories and virtual workshops and the scheduling and information processing of various equipments at the factory level and workshop level, and the simulation of each specific processing process and processing unit are realized from the laboratory perspective. At the same time, some companies have already carried out VMT work and achieved results.
In China, VMT technology has also received great attention. The model modeling method, production process simulation, control and other aspects have done a lot of research work. At the same time, neural network and artificial intelligence technology are introduced into the VMS process, and a virtual factory-level and workshop-level design and scheduling system is established, such as Tsinghua University's "Factory Scheduling Simulation Environment FASE" for manufacturing shop scheduling problems, "Integrated Manufacturing System Software IMSS" and "Processing Process Simulator MPS" for manufacturing shop design, analysis modeling and simulation.
3. Mechanical process simulation
3.1 Current Status and Existing Problems of Machining Process Simulation There are two main situations in the current machining process simulation: one is to simulate the change process of various factors within a specific cutting process from the perspective of metal cutting, and study its cutting. Mechanism for production and research applications; the other is to process process simulation as part of the system, with a focus on constructing a complete virtual manufacturing system. The simulation methods of the two methods are the same, that is, the continuous change model is first established for the machine-added process system, and then the continuous model is discretized into discrete points by mathematical discrete method, and the machining process is simulated by analyzing the physical factors of these discrete points. .
Since the machining process simulation is still in its infancy, the following problems still exist:
(1) The simulation has few processing forms, and the research scope is narrow. Among the many types and forms of cutting processing, the current simulation mainly focuses on milling and grinding. Even in these two processing methods, the simulation is limited to a narrow range. For example, milling is mostly a simulated rod milling cutter and an end milling cutter, and this simulation system can't do anything for other kinds of milling cutters (such as milling cutters for forming surface). The reason is that there are many kinds of machining, there are many processing forms such as car, milling, planing, grinding, boring, etc. On the other hand, the machining theory is complex, and the processing models of different machining methods and tool shapes are quite different. At the same time, most of the current simulation systems carry out geometric simulation, that is, the tool path trajectory, the interference check of the workpiece and the tool, etc., which is called NC Verification. However, in the machining process, geometric verification is only a prerequisite, and more important are the physical forces that determine the factors in the cutting process, such as cutting force, tool vibration and tool wear.
(2) The physical simulation process considers the ideal cutting state and has a large gap with the actual cutting process. In the current simulation system, a large number of hypothetical factors are pre-set, such as setting the process system rigidity to meet the requirements, no vibration; processing material structure Uniform, no hard spots and other defects; no wear and tear on the tool; no change in cutting elements. This assumed ideal state cannot take into account random disturbances during the cutting process, such as material changes caused by hard spots of the workpiece, changes in depth of cut caused by vibration, etc., so that the simulation system cannot truly reflect the actual cutting process.
(3) Simulation means to limit the development of simulation system The development of computer technology is closely linked with the simulation technology. In the past, due to the limitation of computer hardware and software, the simulation time is very long. The coding workload is large, the program is readable and the maintenance is poor, which brings difficulties for the simulation work. At present, the application of C++ language and object-oriented method development simulation system has become a development trend.
The above problems have attracted the attention of researchers. The future machining simulation system will develop in the direction of fast operation, facing multiple processing forms and more in line with actual conditions.
3.2 The structure of the machining process simulation system In the virtual manufacturing process, the detailed design phase of the product is actually the simulation of the mechanical machining process of the product, that is, the analysis of various information in the process system composed of the machine tool-workpiece-tool. Forecast, it includes both geometric simulation and physical simulation. Geometric simulation includes tool path trajectory verification, interference check of workpieces with machine tools and tools. Physical simulation includes analysis and prediction of various physical factors, including cutting force, tool wear, cutting vibration, cutting temperature, workpiece surface roughness, etc. . At the same time, geometric simulation, physical simulation and its various elements have a close relationship, such as tool path trajectory and interference, cutting force directly affects vibration, workpiece surface quality, tool wear and so on.
3.3 Research Objectives and Methods of Numerical Control Turning Process Simulation Turning processing is one of the most widely used processing methods at present. Therefore, it has important theoretical research and practical application value for the simulation of CNC turning machining process.
The turning simulation will simulate and predict the changes of geometric and physical factors in various machining operations such as outer circle, end face, chamfer, thread and curve, and establish a simulation system for turning machining. . The simulation system should have the following features:
(1) Establish a perfect CNC turning simulation system for CNC lathes, provide reliable and optimized NC code for the actual production process, and realize intelligent processing of turning.
At present, the application of CNC lathes and economical CNC lathes in China is becoming more and more popular. It is very practical to get a reliable and optimized NC code before processing. In the past, NC codes were often verified in a trial-and-error manner. This method was time-consuming and labor-intensive. On the other hand, the materials used for trial cutting were often made of wood and plastic, so that although the accuracy of the NC code in geometric information can be verified, The key physical factors such as cutting force, vibration, and surface quality of the workpiece during the cutting process are unknown. The turning simulation system can solve the above problems. At the same time, some parameters in the NC code are modified to further reduce the cutting force, improve tool durability and productivity, and optimize the NC code. In this way, the NC code can be confirmed for practical processing applications, so that the simulation system has the ability of self-learning and adjustment, and the flexibility of the simulation is improved to achieve the purpose of intelligent processing.
(2) Establish a simulation system for the actual machining process, comprehensively consider various interference factors in the actual machining, so that the simulation process highly reflects the actual production process.
In the actual processing process, the process system is subject to various factors and influences, and the physical quantities related to cutting also change due to changes in various cutting conditions. Therefore, in order to be able to realistically simulate the machining situation in the turning process, the turning simulation system should fully consider these actual changes and random disturbances, so that the simulated physical quantities are really close to the actual situation. These influencing factors mainly include cutting vibration caused by machine rigidity and cutting force or workpiece eccentricity. The workpiece structure is not uniform with random interference caused by hard spots, the change of cutting amount during cutting and the influence of tool wear on the cutting process.
(3) Because of the process of verifying and optimizing the NC code, the simulation system can greatly avoid various abnormal phenomena that may occur during the actual machining process, simplify the detection and diagnosis equipment in the actual machining process, and improve the processing safety and Economic benefits. At the same time, the simulation system can realistically simulate the turning process, and can be used as a soft machine tool for training and maintenance of CNC machine tools.
Food grade phosphate refers to a group of phosphates that are used in the food industry as food additives. These phosphates are typically derived from phosphoric acid and are used for various purposes such as pH adjustment, flavor enhancement, moisture retention, and texture improvement in food products.
Food grade phosphates are commonly used in processed meats, poultry products, seafood, baked goods, and dairy products. They can help improve the texture and juiciness of meat products, prevent the formation of ice crystals in frozen foods, and act as a leavening agent in baked goods.
Some common types of food grade phosphates include sodium phosphate, potassium phosphate, and calcium phosphate. These phosphates are generally recognized as safe (GRAS) by the U.S. Food and Drug Administration (FDA) when used in accordance with good manufacturing practices.
However, excessive consumption of food grade phosphates may have health implications, especially for individuals with kidney problems. Therefore, it is important to consume foods containing food grade phosphates in moderation and as part of a balanced diet.
Food Grade Phosphate
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