Latest Trends in Physical Simulation Technology for Machining
Virtual machining technology (virtual machining) has been established for a long time. With the advancement of science and technology, 3D computer aided design has been widely used in product design. In terms of engineering operation design, process design, and product assembly level, computer aided development is required. Technology, especially in computer-aided engineering (cae), uses finite element method (fem) to pre-analyze and study the structure associated with product performance, thermal conductivity, and programming techniques that use computer-aided manufacturing to determine the tool trajectory. All of them have penetrated into all areas of the project and are used effectively.
The development trend of cutting simulation technology includes two aspects. One is to develop nc simulation software to display the tool movement trajectory and determine whether the tool, tool holder and workpiece and their fixtures interfere.
In the endmilling process, the most basic task is to remove the part of the machined material passing through the envelope of the cutting edge of the tool, so that the remaining part becomes the processed surface. The software used to complete this type of processing should include the following: coordination of tools, tool chucks, workpieces, fixtures, etc., the composition of the spindle of the machine tool and its workable range, and can realistically simulate the actions of the machine tool and tool. Especially in recent years, due to the increasing number of five-axis cutting machining, the importance of performing nc simulation before actual machining has become increasingly prominent. In this type of nc simulation software, there are a lot of software with extremely excellent performance, such as the processing efficiency can be calculated from the metal removal volume; according to the metal removal volume to determine whether the cutting process has an overload; if the load is fixed, due to the high feed rate When an overload occurs, the simulation software can adjust the feedrate to prevent overload and shorten the cutting time.
Another development trend of the machining simulation technology is to study the physical phenomena in the analytical machining process, such as the heat generated by plastic deformation of the material being processed. The tool cutting edge removes unwanted materials and forms a machined surface on the workpiece. This series of cutting processes is simulated by a computer. There are few products that can achieve this ideal goal. The "advantedge" of the third wave systems company is a software product that uses the finite element method to perform special optimization analysis on the cutting process. Compared with the finite element method package used for structural analysis, the greatest advantage is that the user interface is excellent, and the machining technicians Easy to parse. The "deform" of the American scientific forming technologies company is a finite element analysis package for plastic deformation processing such as forging, which has recently been transferred to cutting processing.
The cutting process is the deformation process of the plastic deformation and plastic deformation of the chip and the processed material. Compared with the plastic deformation such as stamping and forging, the deformation speed (deformation per unit time) is very large. The resulting plastic deformation energy and the front blade The energy generated by friction on the surface will cause heat, which will cause the temperature to rise significantly. The tool tip will destroy the processed material and separate it into chips and processed surfaces in a continuous and narrow range. This is a remarkable feature of the cutting process. And these phenomena have complex interactions with each other.
If the finite element analysis method is used, the following should be entered: Physical characteristics such as the material properties to be machined and the friction state; Boundary conditions such as cutting conditions and tool shape. Through the finite element analysis of the stiffness equation, it is possible to output cutting force, shear angle, cutting temperature, and other quantitative parameters with the characteristics of the chip generation state. In this process, it is not necessary to establish a mathematical model or make assumptions. According to the results of the finite element analysis, it is also easy to visualize the physical quantities such as chip formation process, stress, and deformation.
To obtain high-precision analytical results, the most important input content is the material characteristics that reflect the stress-deformation relationship of the processed material, and the acquisition of the material characteristics is an extremely laborious task. In the future, with the increase of computer power, the physical simulation technology of this cutting process will gradually become popular. The key to rapid spread is whether it can provide users with the material properties of the material being processed in time.
On-demand development of cutting simulation technology software
At present, many scientists and technicians are conducting research on the most basic cutting technology in production engineering. The purpose of most of these studies is to make predictions on the processing process while clarifying the processing phenomena. If these research contents realize the computer software of the system, it means that a cutting simulation technology software can be formed. For example, the laboratories of the School of Mechanical Engineering at Tokyo University of Agriculture and Technology are conducting several researches on predictive software related to machining simulation technology. The process flow and practical simulation use horizontal and vertical matching research systems. The horizontal direction corresponds to the product design to the processing process. In the longitudinal direction, the practicality is better. Downward is not only practical, but also includes the processing phenomenon. Analyze and implement visualizations.
1. Cutting condition selection system using tool information database and analytical simulation technology
In the actual cutting process, the recommended cutting conditions provided by the tool factory should not be copied, but the trial cutting should be repeated to correct the cutting conditions based on the specific conditions of the machine tool, the tool system, and the workpiece chucking. At the same time, the effective reference data accumulated in the past processing should be input into the database. While effectively using these data, the cutting conditions can be optimized with the help of analytical methods; for new cutting processing without reference data, it should be developed. Related to this cutting conditions selection system. In this system, vibration, machining accuracy, tool temperature rise, tool life, residual stress, etc. are set as analytical contents. On the basis of analysis, the best tool can be selected and cutting conditions can be adjusted.
The data of this system is roughly divided into three parts: tool information data, tool system composition, and cutting conditions. In the cutting conditions can accumulate effective cutting technology parameters.
This article intends to use illustrations to show the optimum milling efficiency for flat-end mills and to optimize the shape error on the sides. Select the desired tool and tool holder based on the database to predict the machining error caused by the bending of the end mill and the tool holder and the rotation change of the combined part of the chuck and spindle taper. The cutting force is predicted using the cutting force at the tool tip multiplied by the cutting force resistance mode. This is the easiest method, but it has obtained good results in which the cutting force waveform agrees with the measured value. Calculate the amount of tool deflection caused by the cutting force at each moment, and connect it to the displacement of the cutting edge that forms the machined surface to obtain the shape of the processed surface. Compared with the calculation of the large-scale finite element method, the calculation time is very small. By inputting the tool information and the cutting condition information, the machining error can be easily simulated.
Although the database already has the actual conditions of cutting and processing, people still hope to further reduce the processing error and improve the processing efficiency. The examples show that it is entirely possible to correct the cutting conditions with this simulation and to achieve optimization.
2. Tool temperature during end mill machining
In recent years, high-speed milling has become commonplace. It has been known from experience that it is suitable for milling conditions with small depth of cut and large feed. It is difficult to grasp the best conditions. Milling is different from turning, in which the former is an interrupted cutting. During the machining process, the temperature rise and cooling of the tool are repeated at high speed. Since the heat conduction to the tool - chip contact part is intermittent, must be based on this feature to resolve the tool temperature changes. The amount of heat transfer has a great influence on the prediction accuracy, but it does not require large-scale calculations related to the deformation and thermal analysis of the chip generation state, so the analytical results can be quickly obtained. The combination of cutting speed, depth of cut, and feed will affect the maximum temperature. When the machining efficiency is constant, increasing the feed speed will reduce the tool temperature. The decrease in temperature will often increase the feed rate to the limit and increase the feed rate. The surface will become rough. Therefore, if the relationship between roughness and temperature can be well balanced, it is possible to select a cutting condition that balances the two.
3. Physical Simulation of Cutting Process Using Finite Element Method
In the physical simulation of the cutting process using the finite element method, the input as the cutting condition includes: cutting speed, cutting thickness, tool rake angle, tool relief angle, and workpiece material characteristics. After analyzing these parameters, the output results of physical properties such as cutting force, chip shape, temperature distribution on tool and chip, stress distribution, deformation distribution, and residual stress distribution can be obtained.
This simulation is also applicable to special cutting conditions such as dynamic cutting. The wave removal process of cutting the wave surface and the waveform generation process of the cutting edge vibration show that the shear angle becomes smaller and the deformation is concentrated and large deformation occurs during the thinning of the chip thickness. In this kind of dynamic cutting process, the shear angle changes. Correspondingly, the size of the deformation range generated by the chip also changes, so the cutting force is not proportional to the cutting thickness of the tool tip. From the shear angle change map corresponding to the change in the cutting thickness of the cutting edge, it can be seen that even if the cutting edge thickness is the same, the amplitude at which the amplitude increases is larger than the shear angle at which the amplitude decreases, and the convexity below the lissajou figure is convex. Half moon shape. Based on this analysis result, it becomes possible to visualize and understand the phenomenon, and a more practical high-precision approximate analysis method is developed.
In addition, the machining of composite metal materials with different material properties and machining such as ultrasonic vibration cutting in which the tool is discontinuously cut while vibrating in the cutting direction can be analyzed using physical simulation techniques. From the analytical example when ferrite and pearlite are distributed in layers, it can be seen that the state of curling of the chips varies greatly due to the different locations of the layers. If the analysis results of the physical simulation can be effectively applied in the material design, it is possible to perform chip treatment without chipbreakers. The reduction of cutting force in ultrasonic vibration cutting is because the vibration frequency of vibration cutting is much higher than the natural vibration frequency of the tool—the material system being processed. The cutting force obtained by this analysis is the force intermittently acting between the tool and the chip, and it is assumed that there is no influence of other factors such as friction reduction, and the cutting force is the same as the normal cutting.
The development trend of cutting simulation technology includes two aspects. One is to develop nc simulation software to display the tool movement trajectory and determine whether the tool, tool holder and workpiece and their fixtures interfere.
In the endmilling process, the most basic task is to remove the part of the machined material passing through the envelope of the cutting edge of the tool, so that the remaining part becomes the processed surface. The software used to complete this type of processing should include the following: coordination of tools, tool chucks, workpieces, fixtures, etc., the composition of the spindle of the machine tool and its workable range, and can realistically simulate the actions of the machine tool and tool. Especially in recent years, due to the increasing number of five-axis cutting machining, the importance of performing nc simulation before actual machining has become increasingly prominent. In this type of nc simulation software, there are a lot of software with extremely excellent performance, such as the processing efficiency can be calculated from the metal removal volume; according to the metal removal volume to determine whether the cutting process has an overload; if the load is fixed, due to the high feed rate When an overload occurs, the simulation software can adjust the feedrate to prevent overload and shorten the cutting time.
Another development trend of the machining simulation technology is to study the physical phenomena in the analytical machining process, such as the heat generated by plastic deformation of the material being processed. The tool cutting edge removes unwanted materials and forms a machined surface on the workpiece. This series of cutting processes is simulated by a computer. There are few products that can achieve this ideal goal. The "advantedge" of the third wave systems company is a software product that uses the finite element method to perform special optimization analysis on the cutting process. Compared with the finite element method package used for structural analysis, the greatest advantage is that the user interface is excellent, and the machining technicians Easy to parse. The "deform" of the American scientific forming technologies company is a finite element analysis package for plastic deformation processing such as forging, which has recently been transferred to cutting processing.
The cutting process is the deformation process of the plastic deformation and plastic deformation of the chip and the processed material. Compared with the plastic deformation such as stamping and forging, the deformation speed (deformation per unit time) is very large. The resulting plastic deformation energy and the front blade The energy generated by friction on the surface will cause heat, which will cause the temperature to rise significantly. The tool tip will destroy the processed material and separate it into chips and processed surfaces in a continuous and narrow range. This is a remarkable feature of the cutting process. And these phenomena have complex interactions with each other.
If the finite element analysis method is used, the following should be entered: Physical characteristics such as the material properties to be machined and the friction state; Boundary conditions such as cutting conditions and tool shape. Through the finite element analysis of the stiffness equation, it is possible to output cutting force, shear angle, cutting temperature, and other quantitative parameters with the characteristics of the chip generation state. In this process, it is not necessary to establish a mathematical model or make assumptions. According to the results of the finite element analysis, it is also easy to visualize the physical quantities such as chip formation process, stress, and deformation.
To obtain high-precision analytical results, the most important input content is the material characteristics that reflect the stress-deformation relationship of the processed material, and the acquisition of the material characteristics is an extremely laborious task. In the future, with the increase of computer power, the physical simulation technology of this cutting process will gradually become popular. The key to rapid spread is whether it can provide users with the material properties of the material being processed in time.
On-demand development of cutting simulation technology software
At present, many scientists and technicians are conducting research on the most basic cutting technology in production engineering. The purpose of most of these studies is to make predictions on the processing process while clarifying the processing phenomena. If these research contents realize the computer software of the system, it means that a cutting simulation technology software can be formed. For example, the laboratories of the School of Mechanical Engineering at Tokyo University of Agriculture and Technology are conducting several researches on predictive software related to machining simulation technology. The process flow and practical simulation use horizontal and vertical matching research systems. The horizontal direction corresponds to the product design to the processing process. In the longitudinal direction, the practicality is better. Downward is not only practical, but also includes the processing phenomenon. Analyze and implement visualizations.
1. Cutting condition selection system using tool information database and analytical simulation technology
In the actual cutting process, the recommended cutting conditions provided by the tool factory should not be copied, but the trial cutting should be repeated to correct the cutting conditions based on the specific conditions of the machine tool, the tool system, and the workpiece chucking. At the same time, the effective reference data accumulated in the past processing should be input into the database. While effectively using these data, the cutting conditions can be optimized with the help of analytical methods; for new cutting processing without reference data, it should be developed. Related to this cutting conditions selection system. In this system, vibration, machining accuracy, tool temperature rise, tool life, residual stress, etc. are set as analytical contents. On the basis of analysis, the best tool can be selected and cutting conditions can be adjusted.
The data of this system is roughly divided into three parts: tool information data, tool system composition, and cutting conditions. In the cutting conditions can accumulate effective cutting technology parameters.
This article intends to use illustrations to show the optimum milling efficiency for flat-end mills and to optimize the shape error on the sides. Select the desired tool and tool holder based on the database to predict the machining error caused by the bending of the end mill and the tool holder and the rotation change of the combined part of the chuck and spindle taper. The cutting force is predicted using the cutting force at the tool tip multiplied by the cutting force resistance mode. This is the easiest method, but it has obtained good results in which the cutting force waveform agrees with the measured value. Calculate the amount of tool deflection caused by the cutting force at each moment, and connect it to the displacement of the cutting edge that forms the machined surface to obtain the shape of the processed surface. Compared with the calculation of the large-scale finite element method, the calculation time is very small. By inputting the tool information and the cutting condition information, the machining error can be easily simulated.
Although the database already has the actual conditions of cutting and processing, people still hope to further reduce the processing error and improve the processing efficiency. The examples show that it is entirely possible to correct the cutting conditions with this simulation and to achieve optimization.
2. Tool temperature during end mill machining
In recent years, high-speed milling has become commonplace. It has been known from experience that it is suitable for milling conditions with small depth of cut and large feed. It is difficult to grasp the best conditions. Milling is different from turning, in which the former is an interrupted cutting. During the machining process, the temperature rise and cooling of the tool are repeated at high speed. Since the heat conduction to the tool - chip contact part is intermittent, must be based on this feature to resolve the tool temperature changes. The amount of heat transfer has a great influence on the prediction accuracy, but it does not require large-scale calculations related to the deformation and thermal analysis of the chip generation state, so the analytical results can be quickly obtained. The combination of cutting speed, depth of cut, and feed will affect the maximum temperature. When the machining efficiency is constant, increasing the feed speed will reduce the tool temperature. The decrease in temperature will often increase the feed rate to the limit and increase the feed rate. The surface will become rough. Therefore, if the relationship between roughness and temperature can be well balanced, it is possible to select a cutting condition that balances the two.
3. Physical Simulation of Cutting Process Using Finite Element Method
In the physical simulation of the cutting process using the finite element method, the input as the cutting condition includes: cutting speed, cutting thickness, tool rake angle, tool relief angle, and workpiece material characteristics. After analyzing these parameters, the output results of physical properties such as cutting force, chip shape, temperature distribution on tool and chip, stress distribution, deformation distribution, and residual stress distribution can be obtained.
This simulation is also applicable to special cutting conditions such as dynamic cutting. The wave removal process of cutting the wave surface and the waveform generation process of the cutting edge vibration show that the shear angle becomes smaller and the deformation is concentrated and large deformation occurs during the thinning of the chip thickness. In this kind of dynamic cutting process, the shear angle changes. Correspondingly, the size of the deformation range generated by the chip also changes, so the cutting force is not proportional to the cutting thickness of the tool tip. From the shear angle change map corresponding to the change in the cutting thickness of the cutting edge, it can be seen that even if the cutting edge thickness is the same, the amplitude at which the amplitude increases is larger than the shear angle at which the amplitude decreases, and the convexity below the lissajou figure is convex. Half moon shape. Based on this analysis result, it becomes possible to visualize and understand the phenomenon, and a more practical high-precision approximate analysis method is developed.
In addition, the machining of composite metal materials with different material properties and machining such as ultrasonic vibration cutting in which the tool is discontinuously cut while vibrating in the cutting direction can be analyzed using physical simulation techniques. From the analytical example when ferrite and pearlite are distributed in layers, it can be seen that the state of curling of the chips varies greatly due to the different locations of the layers. If the analysis results of the physical simulation can be effectively applied in the material design, it is possible to perform chip treatment without chipbreakers. The reduction of cutting force in ultrasonic vibration cutting is because the vibration frequency of vibration cutting is much higher than the natural vibration frequency of the tool—the material system being processed. The cutting force obtained by this analysis is the force intermittently acting between the tool and the chip, and it is assumed that there is no influence of other factors such as friction reduction, and the cutting force is the same as the normal cutting.
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