Electrode loss compensation method for electrical discharge layered milling based on temperature field simulation

Abstract

A method for predicting and compensating electrode wear in electrical discharge milling (EDM) relates to the fields of special machining and intelligent manufacturing. In existing technologies, electrodes continuously wear under the discharge action during EDM, leading to gradual changes in electrode shape and affecting machining accuracy. Furthermore, accurate prediction and effective compensation of electrode wear are difficult to achieve. This invention provides a solution: obtaining the discharge parameters, electrode material parameters, and workpiece material parameters of the EDM process; establishing a single-pulse discharge temperature field calculation model for EDM; applying discharge energy to the discharge channel region with a high energy density at the center and gradually decreasing energy density at the periphery; obtaining the electrode material removal volume and the workpiece material removal volume; calculating the electrode wear rate; and compensating the electrode movement trajectory based on the electrode wear rate and the scanning volume principle of EDM. This method can be used for electrode wear prediction and compensation control during EDM.

Description

Technical Field

[0001] It falls under the category of special processing, specifically involving electrical discharge machining (EDM) layer milling. Background Technology

[0002] With the rapid development of aerospace, precision mold manufacturing, medical devices, and high-end equipment manufacturing, an increasing number of high-hardness, high-strength, and difficult-to-machine materials are being widely used in engineering practice. Because these materials typically possess high strength, hardness, and wear resistance, traditional machining methods are significantly limited in terms of processing efficiency, machining quality, and tool life, making it difficult to meet the precision manufacturing requirements of complex structural parts. Against this backdrop, electrical discharge machining (EDM) technology, due to its independence from material mechanical properties and its ability to machine high-hardness conductive materials, has gradually become an important means of machining complex structural parts and is widely used in mold manufacturing, precision parts machining, and the manufacturing of complex cavity structures.

[0003] Electrical discharge machining (EDM) is a special machining method that uses pulsed discharges between an electrode and a workpiece to generate instantaneous high temperatures, causing localized melting and vaporization of the workpiece material, thereby removing the material. During the discharge process, high-temperature plasma is generated within the discharge channel. The heat generated by the discharge acts on both the workpiece and electrode materials, resulting in material removal while also causing some wear on the electrode. Especially in EDM milling, by planning the electrode movement trajectory, complex three-dimensional structures can be machined using electrodes of simple shapes, significantly improving the flexibility and versatility of machining. However, at the same time, the electrode is continuously subjected to discharge heat during machining, causing its shape to gradually change, thus significantly affecting machining accuracy.

[0004] To reduce the impact of electrode wear on machining accuracy, existing research typically employs empirical models or experimental statistical methods to estimate electrode wear. For example, empirical formulas based on machining electrical parameters are used to predict electrode wear rates, or electrode wear under different machining conditions is measured multiple times in experiments, allowing for some compensation in the CNC program. Additionally, some studies correct electrode shape changes through online measurement or offline detection to reduce the impact of electrode wear on final machining accuracy. However, these methods usually rely on extensive experimental data, have poor model universality, and are difficult to apply to different materials, different discharge conditions, and complex machining paths. Furthermore, since electrical discharge machining is essentially a transient thermophysical process, the temperature field distribution generated by the discharge directly affects the material removal process of the workpiece and electrode; relying solely on empirical models cannot accurately reflect the formation mechanism of electrode wear during actual machining.

[0005] In recent years, some studies have begun to use numerical simulation methods to analyze the discharge temperature field during electrical discharge machining (EDM). By establishing a heat conduction model, the transfer process of discharge energy between the electrode and the workpiece can be simulated, thereby predicting material removal. However, existing research mainly focuses on the thermal analysis of a single discharge process, and does not adequately consider the changes in electrode morphology during continuous machining. This makes it difficult to achieve dynamic prediction and machining compensation of electrode wear, especially in EDM layer milling, where the machining trajectory is complex and the discharge conditions change frequently, making the electrode wear pattern even more complex. Current technologies struggle to achieve high-precision prediction and compensation.

[0006] In summary, existing technologies have the drawback of making it difficult to accurately predict electrode wear during EDM layer milling and thus achieve effective compensation. Summary of the Invention

[0007] To address the shortcomings of existing technologies in accurately predicting electrode wear during electrical discharge machining (EDM) and effectively compensating for it, the present invention provides the following technical solution: A method for compensating electrode loss in electrical discharge machining (EDM) layered milling based on temperature field simulation includes: The discharge parameters, electrode material parameters, and workpiece material parameters of electrical discharge milling are obtained, and a calculation model of the temperature field of a single pulse discharge in electrical discharge milling is established based on the discharge parameters, electrode material parameters, and workpiece material parameters. The step of loading the discharge energy into the discharge channel region according to the distribution pattern of high energy density at the center and gradually decreasing energy density at the periphery to obtain the discharge temperature field distribution result is as follows: Based on the discharge temperature field distribution results, the temperature of the calculation region is solved step by step over time, and the regions where the electrode material and workpiece material reach the melting condition are determined. The steps of obtaining the electrode material removal volume and workpiece material removal volume are obtained by deleting the calculation units that reach the melting condition. The steps for calculating the electrode loss rate based on the electrode material removal volume and the workpiece material removal volume; The steps are as follows: Based on the electrode loss rate and combined with the scanning volume principle of electrical discharge milling, the electrode motion trajectory is compensated and calculated to obtain the compensated electrode motion trajectory. The steps are to generate a machining program based on the compensated electrode motion trajectory and perform electrical discharge milling.

[0008] Furthermore, a preferred embodiment is provided, in which the calculation model of temperature field of single pulse discharge in electrical discharge milling is established by establishing a three-dimensional calculation model that simultaneously includes the electrode region and the workpiece region, and a discharge channel region is set between the electrode region and the workpiece region as an energy input region.

[0009] Furthermore, a preferred embodiment is provided in which the discharge energy is applied to the discharge channel region in a distribution pattern of high energy density at the center and gradually decreasing energy density at the periphery, including maximizing the energy density in the central region of the discharge channel and gradually decreasing it with increasing distance from the discharge center to simulate the energy distribution inside the discharge channel.

[0010] Furthermore, a preferred embodiment is provided, in which the time-step temperature solution includes setting an energy input boundary in the discharge channel region, setting a convective heat dissipation boundary on the surface in contact with the working fluid, and setting the boundary away from the discharge region as an adiabatic boundary to obtain the temperature field distribution results of a single pulse discharge in electrical discharge milling.

[0011] Furthermore, a preferred embodiment is provided, in which determining the region where the electrode material and the workpiece material have reached the melting condition includes determining the temperature of each calculation unit during the time-step temperature solution process and deleting calculation units whose temperature has reached or exceeded the material melting temperature to simulate the material removal process.

[0012] Furthermore, a preferred embodiment is provided, in which the calculation of electrode loss rate includes statistically analyzing the volume of electrode material removed and the volume of workpiece material removed, and calculating the proportional relationship between the volume of electrode material removed and the volume of workpiece material removed to obtain the electrode loss rate.

[0013] A device for compensating electrode loss in electrical discharge machining (EDM) based on temperature field simulation is also provided, comprising: The module obtains the discharge parameters, electrode material parameters, and workpiece material parameters of electrical discharge milling, and establishes a single-pulse discharge temperature field calculation model for electrical discharge milling based on the discharge parameters, electrode material parameters, and workpiece material parameters. The module loads the discharge energy into the discharge channel region according to the distribution pattern of high energy density at the center and gradually decreasing energy density at the periphery to obtain the discharge temperature field distribution result. Based on the discharge temperature field distribution results, the temperature of the calculation area is solved step by step over time, and the areas where the electrode material and workpiece material reach the melting condition are determined. The modules for obtaining the electrode material removal volume and workpiece material removal volume are obtained by deleting the calculation units that reach the melting condition. A module for calculating electrode loss rate based on the electrode material removal volume and the workpiece material removal volume; A module that calculates the compensation for the electrode motion trajectory based on the electrode loss rate and the scanning volume principle of electrical discharge milling to obtain the compensated electrode motion trajectory. A module that generates a machining program based on the compensated electrode motion trajectory and performs electrical discharge milling.

[0014] A computer storage medium is also provided for storing a computer program, which, when read by the computer, executes the method.

[0015] A computer is also provided, including a processor and a storage medium, wherein the computer executes the method when the processor reads a computer program stored in the storage medium.

[0016] A computer program product is also provided, which, when executed, implements the method described.

[0017] The advantages of the technical solution provided by this invention are as follows: Establishing a theoretical model of the temperature field of a single discharge in electrical discharge milling (EDM) can describe the heating process of the electrode and workpiece materials from the perspective of the discharge energy transfer mechanism, thus providing a basic computational framework for subsequent electrode wear prediction. This feature stems from the steps of establishing the theoretical model of the temperature field of a single pulse discharge in EDM. By transforming the discharge thermal process into a computable temperature field problem, electrode wear analysis no longer relies on traditional empirical formulas or experimental statistical data, but is based on the energy transfer law during the discharge process. Compared with existing offline compensation methods that rely on a large number of experiments to build databases, this method can reveal the electrode material removal mechanism at the theoretical level, improving the interpretability and applicability of electrode wear prediction.

[0018] Simplifying the heat source of a single-pulse discharge into a Gaussian heat source and applying it to the workpiece and electrode surfaces allows for a more accurate description of the spatial distribution of discharge energy within the discharge channel. This characteristic stems from the step of establishing a Gaussian heat source model. By employing a Gaussian distribution function to simulate the concentrated distribution of discharge energy in the discharge region, the temperature field simulation more closely matches the energy density changes during the actual discharge process. Compared to the traditional model that simply equates the discharge heat source to a uniform heat source, this approach more accurately reflects the temperature gradient difference between the discharge center and edge regions, thereby improving the accuracy of the simulation of material melting and removal processes.

[0019] By setting reasonable boundary and initial conditions, the temperature field simulation results can be ensured to conform to the actual EDM environment. This feature stems from setting the discharge channel region as a hot-loaded surface, other regions as convective heat transfer surfaces, and the remaining surfaces as adiabatic surfaces, and setting the initial temperature to room temperature. This introduces the heat transfer factors of the discharge medium and the heat dissipation factors of the environment into the calculation model, enabling the simulation process to reflect the thermal balance between the heat input of the discharge region and the heat dissipation of the external medium during the actual processing. Compared with the simplified model that ignores the influence of environmental heat dissipation, this significantly improves the realism of the temperature field calculation results.

[0020] Setting separate thermophysical property parameters for the workpiece and electrode materials ensures that the simulation calculations accurately reflect the thermal response behavior of different materials under high-temperature conditions. This feature stems from the step of setting material thermophysical property parameters. By introducing parameters such as thermal conductivity, density, specific heat capacity, and latent heat of phase change, the simulation model can reflect the thermal conductivity and phase change characteristics of different materials under high-temperature discharge environments, thereby accurately describing the material melting and vaporization processes. Compared to traditional calculation methods that only consider a single material parameter or simplify material properties, this improves the accuracy of material removal prediction.

[0021] Differentiated meshing of the model region can improve computational efficiency while maintaining computational accuracy. This feature stems from the step of dividing the area near the heat source into a fine mesh and the area farther from the heat source into a coarse mesh. This allows for higher computational accuracy in areas with drastic temperature gradient changes, while reducing the number of computational units in areas with smaller temperature changes. Thus, while maintaining the accuracy of the temperature field solution, the computational load is reduced, which can significantly improve simulation efficiency compared to uniform meshing.

[0022] By solving the temperature field and employing the element birth and death technique to remove elements with temperatures exceeding the melting point, the actual material removal process during electrical discharge machining (EDM) can be simulated. This feature stems from the model solving and element removal steps. By setting the solution time step based on the pulse width and deleting elements with temperatures exceeding the material's melting point during the calculation, the simulation model can dynamically reflect the material melting and removal process caused by discharge. This enables numerical simulation of the discharge pit formation process, providing a more accurate reflection of the material removal mechanism compared to methods that rely solely on empirical formulas to estimate material removal.

[0023] Predicting electrode wear rate by calculating the ratio of electrode to workpiece removal unit volume enables quantitative prediction of electrode wear. This feature stems from the step of calculating material removal volume based on temperature field simulation results. By statistically analyzing the volumes of the electrode and workpiece removed units during the simulation and calculating their ratio, the electrode wear rate is obtained. This transforms the complex discharge thermal process into a quantifiable electrode wear index, significantly reducing experimental costs compared to methods relying on numerous experiments to determine electrode wear rate.

[0024] Designing electrode motion paths based on the scanning volume principle enables machining compensation for electrode wear. This feature stems from the step of designing electrode motion paths based on the predicted electrode wear rate. By combining the scanning volume characteristics of EDM machining, the predicted electrode wear is incorporated into the electrode trajectory planning, allowing the electrode to automatically compensate for dimensional changes caused by wear during machining, thereby ensuring consistency between the machining trajectory and the target shape.

[0025] Electrode wear compensation can be achieved in actual machining by converting the compensated electrode motion path into a CNC program for EDM layer milling. This feature stems from the step of converting the compensation path into CNC code and performing the machining, allowing the theoretically predicted electrode wear compensation strategy to be directly applied to the CNC machine tool machining process. This achieves electrode wear compensation without adding a complex sensor system, which reduces equipment complexity and improves the engineering application feasibility of the system compared to online compensation technology that requires visual inspection or online measurement systems.

[0026] It is applicable to precision machining operations where electrode wear is predicted and compensated during electrical discharge milling. Attached Figure Description

[0027] Figure 1 This is a flowchart of an electrical discharge milling electrode loss compensation method based on temperature field simulation. Figure 2 This is a schematic diagram of the temperature field simulation principle for electrical discharge milling. Figure 3 This is a thermophysical property curve of Ti-6Al-4V; Figure 4 This is a graph showing the thermal properties of tungsten. Figure 5 This is a schematic diagram of the electrode loss compensation method for electrical discharge milling based on temperature field simulation. Figure 6 This is a comparison of white light interferometer 3D scanning images of straight grooves machined by electrical discharge milling with and without compensation. Detailed Implementation

[0028] To make the advantages and benefits of the technical solution provided by the present invention clearer, the technical solution provided by the present invention will now be described in further detail with reference to the accompanying drawings, specifically: Implementation Method 1: This implementation method provides a method for compensating electrode loss in electrical discharge machining (EDM) layered milling based on temperature field simulation, including: The discharge parameters, electrode material parameters, and workpiece material parameters of electrical discharge milling are obtained, and a calculation model of the temperature field of a single pulse discharge in electrical discharge milling is established based on the discharge parameters, electrode material parameters, and workpiece material parameters. The step of loading the discharge energy into the discharge channel region according to the distribution pattern of high energy density at the center and gradually decreasing energy density at the periphery to obtain the discharge temperature field distribution result is as follows: Based on the discharge temperature field distribution results, the temperature of the calculation region is solved step by step over time, and the regions where the electrode material and workpiece material reach the melting condition are determined. The steps of obtaining the electrode material removal volume and workpiece material removal volume are obtained by deleting the calculation units that reach the melting condition. The steps for calculating the electrode loss rate based on the electrode material removal volume and the workpiece material removal volume; The steps are as follows: Based on the electrode loss rate and combined with the scanning volume principle of electrical discharge milling, the electrode motion trajectory is compensated and calculated to obtain the compensated electrode motion trajectory. The steps are to generate a machining program based on the compensated electrode motion trajectory and perform electrical discharge milling.

[0029] Furthermore, the calculation model for the temperature field of a single pulse discharge in electrical discharge milling is established by creating a three-dimensional calculation model that simultaneously includes the electrode region and the workpiece region, and setting a discharge channel region between the electrode region and the workpiece region as an energy input region.

[0030] Furthermore, the discharge energy is applied to the discharge channel region in a distribution pattern where the energy density is high at the center and gradually decreases at the periphery. This includes maximizing the energy density in the central region of the discharge channel and gradually decreasing it with increasing distance from the discharge center to simulate the energy distribution inside the discharge channel.

[0031] Furthermore, the time-step temperature solution includes setting an energy input boundary in the discharge channel region, setting a convective heat dissipation boundary on the surface in contact with the working fluid, and setting the boundary far from the discharge region as an adiabatic boundary to obtain the temperature field distribution results of a single pulse discharge in electrical discharge milling.

[0032] Furthermore, determining the region where the electrode material and workpiece material reach the melting condition involves judging the temperature of each calculation unit during the time-step temperature solution process and deleting calculation units whose temperature reaches or exceeds the material melting temperature to simulate the material removal process.

[0033] Furthermore, calculating the electrode loss rate involves statistically analyzing the volume of electrode material removed and the volume of workpiece material removed, and then calculating the ratio between the two volumes to obtain the electrode loss rate.

[0034] A device for compensating electrode loss in electrical discharge machining (EDM) based on temperature field simulation is also provided, comprising: The module obtains the discharge parameters, electrode material parameters, and workpiece material parameters of electrical discharge milling, and establishes a single-pulse discharge temperature field calculation model for electrical discharge milling based on the discharge parameters, electrode material parameters, and workpiece material parameters. The module loads the discharge energy into the discharge channel region according to the distribution pattern of high energy density at the center and gradually decreasing energy density at the periphery to obtain the discharge temperature field distribution result. Based on the discharge temperature field distribution results, the temperature of the calculation area is solved step by step over time, and the areas where the electrode material and workpiece material reach the melting condition are determined. The modules for obtaining the electrode material removal volume and workpiece material removal volume are obtained by deleting the calculation units that reach the melting condition. A module for calculating electrode loss rate based on the electrode material removal volume and the workpiece material removal volume; A module that calculates the compensation for the electrode motion trajectory based on the electrode loss rate and the scanning volume principle of electrical discharge milling to obtain the compensated electrode motion trajectory. A module that generates a machining program based on the compensated electrode motion trajectory and performs electrical discharge milling.

[0035] A computer storage medium is also provided for storing a computer program, which, when read by the computer, executes the method.

[0036] A computer is also provided, including a processor and a storage medium, wherein the computer executes the method when the processor reads a computer program stored in the storage medium.

[0037] A computer program product is also provided, which, when executed, implements the method described.

[0038] Implementation Method Two: This implementation method is a further detailed description of the technical solution provided in Implementation Method One, specifically: First, a single-pulse discharge temperature field calculation model is established during the electrical discharge milling (EDM) process to describe the energy transfer process between the electrode and the workpiece during discharge, and to provide basic data for subsequent material removal behavior analysis. Specifically, during EDM, a certain discharge gap is maintained between the electrode and the workpiece. When a voltage is applied by the pulse power supply, a discharge channel is formed in the working fluid medium, instantaneously releasing a large amount of energy and forming high-temperature plasma, thereby generating extremely high temperatures in localized areas on the electrode and workpiece surfaces. To perform calculation and analysis of this process, a three-dimensional calculation model containing both the electrode and workpiece regions is established in a numerical calculation environment, with the discharge channel region set between them as the heat input location. By loading the energy of a single pulse discharge, the energy diffuses into the electrode and workpiece interior within the discharge region. This method constructs a single-pulse discharge temperature field calculation model, thereby obtaining the temperature changes of the electrode and workpiece interior at different time stages during the discharge process. This temperature field distribution result serves as the basic input for subsequent material melting and removal judgments.

[0039] After establishing a single-discharge temperature field calculation model, the spatial distribution of discharge energy within the discharge region is described to more closely approximate the concentrated energy distribution characteristics during actual discharge. Specifically, the discharge heat source is configured with a distribution pattern of high energy density in the central region and gradually decreasing energy density in the peripheral region. This maximizes energy input in the discharge center region, while gradually decreasing energy input with increasing distance from the discharge center, thus simulating the actual physical phenomenon of highly concentrated energy within the discharge channel and gradual attenuation at the edges. Simultaneously, based on the operating characteristics of the pulse power supply, the heat source's application time is controlled, ensuring that energy is only input into the material during the pulse duration. Energy input ceases after the pulse ends, allowing the temperature field to enter a natural diffusion and heat dissipation phase. This method yields the complete process of temperature change within the material over time during a single-pulse discharge, providing input data for subsequent material melting determination.

[0040] After setting up the discharge heat source, the boundary conditions of the computational model are configured to simulate the heat exchange process in a real electrical discharge machining (EDM) environment. Specifically, the material surface where the discharge channel region is located is set as the energy input boundary, allowing discharge energy to enter the electrode and workpiece from this region. Simultaneously, the areas where the outer surfaces of the electrode and workpiece contact the working fluid are set as convective heat dissipation boundaries, enabling the material to dissipate heat through the working fluid during machining, thus simulating the actual heat removal process by the working fluid. Boundaries far from the discharge region are set as adiabatic boundaries to reduce unnecessary energy loss and improve computational efficiency. Furthermore, in the initial state of the model, the overall temperature of the electrode and workpiece is set to the ambient temperature, allowing the calculation to begin from a stable initial state. These boundary condition settings ensure that the temperature field calculation results more closely approximate the heat conduction and dissipation conditions in a real machining process, thereby improving the reliability of the simulation results.

[0041] After setting the boundary conditions, the thermophysical parameters of the electrode and workpiece materials are configured to ensure that the temperature field calculation reflects the thermal response characteristics of different materials under high-temperature discharge conditions. Specifically, parameters such as material density, thermal conductivity, and temperature change rate per unit mass of material after absorbing heat are set for both the electrode and workpiece materials in the model. Furthermore, the phase transition energy required for the material to reach its melting temperature is set, enabling the model to reflect the process of the material gradually transitioning from a solid to a molten state under high-temperature conditions. By introducing the influence of material phase transition energy, the model can accurately describe the phase transition phenomenon that occurs when the material reaches the melting condition during the calculation process, providing an accurate basis for subsequent material removal judgments.

[0042] After setting the material parameters, the entire computational domain is meshed to improve computational efficiency while maintaining accuracy. Specifically, in the region near the discharge heat source, where the temperature gradient is large, this area is divided into smaller computational cells to improve the accuracy of temperature change calculations. Conversely, in areas farther from the discharge region, where temperature changes are relatively gradual, larger computational cells are used to reduce the overall number of computational cells and thus reduce computation time. After meshing, the model is solved step-by-step. By calculating the temperature change of each computational cell during a single pulse discharge, the complete temperature field evolution process is obtained. This temperature field result serves as the input data for material removal decisions.

[0043] After obtaining the temperature field calculation results, the material removal behavior is judged and material deletion is performed based on the material melting conditions to simulate the gradual removal of material during electrical discharge machining. Specifically, after each time step calculation is completed, the temperature of all calculation units is judged. When the temperature of a calculation unit reaches or exceeds the melting temperature of the material, the calculation unit is considered to have melted and been removed by the process. By deleting the unit from the calculation model, the process of material gradually forming pits during discharge is simulated. During continuous time step calculations, by continuously judging and deleting units that meet the conditions, the morphology of the discharge pits formed by a single discharge can be gradually obtained. At the same time, the material volume information corresponding to the deleted units is recorded, and this volume information is used as input data for electrode loss calculation.

[0044] After obtaining the material removal volume data, the electrode wear rate is calculated to describe the degree of electrode material wear during the electrical discharge machining (EDM) process. Specifically, by statistically analyzing the total volume of electrode material removed in a single discharge cycle and the total volume of workpiece material removed, the proportional relationship between the electrode material removal volume and the workpiece material removal volume is calculated to obtain the electrode wear rate. This wear rate reflects the degree of electrode wear during machining and can be used to describe the variation law of electrode wear under different machining parameters. The wear rate result serves as the input for subsequent machining trajectory compensation calculations.

[0045] After obtaining the electrode wear rate, the electrode movement trajectory is compensated based on the electrode scanning volume principle during electrical discharge milling, thereby reducing the impact of electrode wear on machining accuracy. Specifically, during electrical discharge milling, the electrode scans the workpiece layer by layer according to a preset trajectory. As the electrode continuously wears during machining, its actual machining dimensions gradually change. Therefore, based on the predicted electrode wear rate, the position of the electrode in the machining trajectory is corrected, enabling the electrode to automatically compensate for dimensional changes caused by wear during movement, thus maintaining stable machining dimensions. By introducing electrode wear compensation during the trajectory planning stage, the entire machining process can maintain high machining accuracy even with gradual electrode wear.

[0046] After electrode motion trajectory compensation is completed, the compensated electrode motion trajectory is converted into a machining program that can be recognized by the CNC machine tool, and then the actual machining is performed on the EDM equipment. Specifically, corresponding CNC machining instructions are generated based on the compensated electrode motion path, and the machining program is input into the control system of the EDM equipment, so that the equipment drives the electrode to move according to the compensated trajectory and performs layered milling. Through the above method, electrode wear can be predicted and compensated during the actual machining process, thereby improving the machining accuracy and stability of EDM milling of complex structural parts without relying on a complex online measurement system.

[0047] Implementation Method 3, in conjunction with Appendix Figure 1-6 This embodiment describes the technical solution provided above in further detail through specific examples. Specifically: The following description, in conjunction with Figure 1, further illustrates this embodiment.

[0048] like Figure 1 As shown, the electrode loss compensation method for electrical discharge milling based on temperature field simulation includes the following steps: Step 1: Establish a theoretical model of the temperature field of a single discharge in electrical discharge milling; Step 2: Establish a Gaussian heat source model; Step 3: Set boundary conditions and initial conditions; Step 4: Set material properties; Step 5: Mesh the model; Step 6: Model Solving and Element Removal; Step 7: Predict electrode loss rate based on temperature field simulation; Step 8: Design the electrode motion path based on the principle of electrode loss compensation based on scanning volume; Step 9: Electrical discharge milling to compensate for electrode wear.

[0049] The specific implementation of this embodiment is described in detail below with reference to specific examples. For the workpiece material and tool electrode material, this embodiment is applicable to conductive materials with uniform composition, such as elemental metals and alloys. In this specific example, Ti-6Al-4V is used as the workpiece material and tungsten as the tool electrode material. For the simulation software, this embodiment can use finite element analysis software such as ANSYS APDL, Abaqus, and Comsol. In this specific example, ANSYS APDL software is used as an example.

[0050] Step 1: Establish a theoretical model of the temperature field of a single discharge in electrical discharge milling: like Figure 1 As shown, in the process of electrical discharge machining (EDM) layer milling, the rotating tool electrode moves along a set path under the control of the servo system. When the workpiece and the bottom surface of the tool electrode gradually approach each other and reach the size of the discharge gap, a discharge plasma channel is formed between them under the action of the pulse power supply. The released energy generates extremely high heat, which is quickly conducted to the inside of the workpiece and the tool electrode, causing some of the material of the workpiece and the tool electrode to melt or vaporize. This molten material is carried away by the working medium, thus forming discharge pits on the workpiece and the tool electrode. Continuous discharge will form a large number of such discharge pits. These discharge pits overlap each other, causing the material on the workpiece and the tool electrode to be removed, thereby achieving subtractive manufacturing and causing electrode wear.

[0051] Material removal during the discharge process is the result of the interaction of multiple physical fields, such as temperature field, flow field, and electromagnetic field, but the most important driving force for material removal is the temperature field. Therefore, this embodiment establishes a temperature field simulation model for a single discharge in electrical discharge milling. To facilitate mathematical modeling and simulation analysis, the following assumptions are made: (1) Each single-pulse discharge generates only one discharge channel, which can be approximated as a cylinder; (2) No material removal occurs during the heating process; the volume of material removed is calculated based on the temperature distribution only after the simulation is completed. (3) Heat transfer includes heat conduction and heat convection, while heat radiation is ignored; (4) The applied heat source is approximately a Gaussian heat source, and the radius of the discharge channel is a 6σ interval of the Gaussian heat flux density; (5) Considering the latent heat of the material, the change in energy is equal to the change in enthalpy.

[0052] Temperature field simulation models were established for both the workpiece and the tool electrode. Since both the discharge channel and the discharge pit are centrally symmetric, a quarter-scale model (cubic model) was used to simplify the calculation. The model dimensions were determined by the size of the heat-affected zone. For this specific example, considering the significant difference in discharge pit size between roughing and finishing, two different model sizes were established. For roughing, the model side length was set to 40 μm, and for finishing, the model side length was set to 15 μm.

[0053] Step 2: Establish a Gaussian heat source model: The heat generated by the discharge is applied to the workpiece and tool electrode surfaces, approximating a normal distribution. Therefore, a Gaussian heat flux density is used for simulation, and the discharge channel radius is the 6σ interval of the Gaussian heat flux density. Since the discharge channel radius expands continuously in the initial stage of discharge and then tends to stabilize, the radius of the heat source varies with time. The simulation parameters include discharge voltage, peak current, and pulse width. The time-varying Gaussian heat flux density used for the heat source is: (1) In the formula, The surface heat flux density varies with time and space; The energy distribution coefficient is set to 0.4 for roughing and 0.2 for tool electrode, and 0.2 for finishing. This is the discharge voltage; This is the peak current; The discharge channel radius varies with time. In this specific example, the discharge channel radius gradually increases within the first 2 μs of discharge, then remains constant until the discharge ends. The discharge channel radius within the first 2 μs is given by the following formula: (2) To prevent non-convergence caused by excessive discharge energy due to an initially small discharge channel radius during simulation, and to conserve computational resources, the discharge channel radius is discretized. In this specific example, a discharge channel radius value is taken every 0.2 μs and used as the discharge channel radius for the previous time period.

[0054] Step 3: Set boundary conditions and initial conditions: like Figure 5As shown, one vertex of the cube model is set as the center point of the heat source loading, and the face adjacent to this vertex is set as the upper surface of the workpiece or the lower surface of the tool electrode, serving as the working plane. A Gaussian heat flux density is applied within the discharge channel radius on the workpiece plane, as shown in formula (1). The other areas on this plane are set as heat exchange surfaces, and heat is transferred between them and the discharge medium through thermal convection, as described by the following formula: (3) In the formula, The thermal conductivity of the material varies with temperature; The convective heat transfer coefficient between the material surface and the discharge medium; The surface temperature of the material; Let be the temperature of the discharge medium. In this model, the discharge medium is considered a fluid that can quickly carry away heat for heat dissipation. Set the temperature to 20°C. This is the normal vector. Other surfaces in the simulation model are located inside the material and outside the heat-affected zone; they are assumed not to exchange heat with the external environment and are set as thermally insulated, controlled by the following equations. (4) Inside the cube model, heat is transferred via thermal conduction. According to Fourier's law of heat conduction, the heat conduction formula is as follows: (5) In the formula, This refers to the specific heat capacity of the material as it changes with temperature. The density of the material varies with temperature.

[0055] Step 4: Set material properties: To perform physical field simulations, material properties need to be set. In temperature field simulations, the thermal conductivity, specific heat capacity, and density of the material need to be set. These three physical quantities all change with the material temperature; therefore, thermophysical property curves varying with temperature are used as material properties. In this specific example, the workpiece material is Ti-6Al-4V, with an elemental composition of Ti (89.405%), Al (6%), V (4%), Fe (0.3%), C (0.08%), O (0.15%), N (0.05%), and H (0.015%). Its thermophysical properties are calculated using ProCast. In electrical discharge machining (EDM), the material removal mechanism is melting and vaporization; therefore, the melting point of the material needs to be determined. In this specific example, the melting point of Ti-6Al-4V is 1660°C, while the melting point of tungsten is 3410°C. Near the melting point of a material, a significant endothermic phenomenon occurs. If this phenomenon is defined using specific heat capacity, it will result in abrupt changes, easily leading to calculation non-convergence. Therefore, latent heat is used instead. In this specific example, the latent heat of fusion of Ti-6Al-4V is 320.76 kJ / kg, while that of tungsten is 284.49 kJ / kg. The thermophysical property curves of Ti-6Al-4V and tungsten are shown below. Figure 3 and Figure 4 As shown. The working medium is kerosene, and its convective heat transfer coefficient with the material is 8000 W / (m²·K).

[0056] Step 5: Mesh the model: Since the model is a cube, using a hexahedral mesh effectively reduces mesh planning and computational costs. In this specific example, two models with different dimensions were established: one for roughing and one for finishing. For roughing, the element edge length was set to 0.25 μm, and for finishing, it was set to 0.1 μm. Because the heat transfer methods inside and on the surface of the model differ, the definitions of the element properties also differ. Taking ANSYS APDL software as an example, the surface containing the model's working plane is defined as the "SURF152" 3-D surface thermal effect element. This element is defined by 4 to 9 nodes and material properties, with an additional node (not on the element) used for convection or radiation effects. Because the model uses a hexahedral mesh, no intermediate nodes are needed; therefore, the "SURF152" 3-D surface thermal effect element in this model has 5 nodes. This element can apply variable loads and consider surface effects, thus simulating the Gaussian heat source load within the discharge channel and thermal convection outside the discharge channel, where the discharge channel radius and Gaussian heat flux density both change with temperature. The other elements of the model are defined as “SOLID70” 3-D solid thermal elements. These elements have heat conduction capabilities in three directions, eight nodes, and only one degree of temperature freedom on each node. They can be used for three-dimensional static or transient thermal analysis and can achieve uniform heat flow transfer.

[0057] Step Six: Model Solving and Element Removal: The solution calculation of this model is divided into three parts: heating process, isothermal process, and cooling process. Taking a pulse width of 10 μs and a pulse interval of 10 μs as an example, the heating process is from the beginning to 2 μs. During this time, the discharge channel expands, and the Gaussian heat flux density is calculated using a changing discharge channel radius, which is given by formula (2). The isothermal process is from 2 μs to 10 μs, and the Gaussian heat flux density is calculated using a constant discharge channel radius. The cooling process is from 10 μs to 20 μs, and no heat flux density is applied.

[0058] After cooling, element death and birth techniques are used to remove elements. If material is added to (or removed from) the model, the corresponding element in the model "exists" (or disappears). The element death and birth option is used to kill or reactivate the selected element in this case. In this model, the life or death state of an element is determined by the element temperature calculated in the simulation. Taking ANSYS APDL software as an example, the ESEL command is used to select elements whose temperature exceeds their melting point, and then the EKILL command is used to "kill" them, which multiplies their thermal conductivity matrix by a very small factor, the default value of which is 1×10. -6 This birth-death unit technology simulates the effect of molten material being removed.

[0059] Step 7: Predict electrode loss rate based on temperature field simulation: like Figure 5 As shown, in the simulation model after solving the workpiece and tool electrode, the volume removed is measured. The ratio of the volume removed from the tool electrode to that removed from the workpiece is the electrode wear rate, which is calculated by the following formula: (6) In the formula, Electrode loss rate, The volume removed by the tool electrode. The volume removed from the workpiece.

[0060] Step 8: Design the electrode motion path based on the principle of electrode loss compensation for scanning volume: Electrode wear is compensated based on the volume of material removed. When the volume of electrode wear reaches a preset value, axial compensation is performed. The tool electrode then performs electrical discharge milling on the workpiece according to a pre-set toolpath to machine the desired part contour. Starting from the machining start point, when the workpiece material removal volume reaches ΔV, the electrode performs axial length compensation. That is, upon reaching the compensation point, the electrode performs axial feed with a feed distance of ΔZ until all layers are machined. The compensated toolpath is then coded into G-code and applied to the electrical discharge milling process.

[0061] Step 9: Electrical discharge milling with electrode wear compensation. Electrical discharge machining (EDM) is performed based on the compensated toolpath, and the result is compared with the result without compensation. In this specific example, the comparison diagram is as follows. Figure 6 As shown in the figure, the desired machining depth is 240 μm. The machining depth without compensation is only 185.21 μm, with an error of 19.22%. However, the machining depth after compensation reaches 231.34 μm, which is close to the desired value, with an error of 3.61%. This indicates that this embodiment achieves high-precision machining of electrical discharge layer milling.

[0062] Beneficial effects: This embodiment proposes a temperature field simulation-based electrode loss compensation method for electrical discharge milling (EDM). This method considers the energy flow of the discharge and the thermal properties of the material, establishing a temperature field simulation model of the EDM discharge for both the workpiece and the electrode material. This model allows for the prediction of electrode loss in principle, and the predicted electrode loss is used to design an electrode motion path that considers electrode loss compensation. This method is then applied to EDM layer milling. Compared to existing EDM layer milling electrode loss compensation methods, this embodiment does not require complex online detection equipment and systems. Therefore, compared to online electrode loss compensation methods, this embodiment offers advantages such as low investment cost and high reliability. Furthermore, this embodiment does not require extensive basic process testing. Compared to traditional offline electrode loss compensation methods based on process databases, this embodiment saves on testing costs and time, and is easier to apply to other materials. Therefore, this embodiment achieves relatively reliable high-precision EDM layer milling with simple equipment at a lower testing cost and time cost, contributing to environmentally friendly green manufacturing.

[0063] The above description of several specific embodiments further details the technical solution provided by the present invention in order to highlight the advantages and benefits of the technical solution provided by the present invention. However, the above-described specific embodiments are not intended to limit the present invention. Any reasonable modifications and improvements to the present invention, combinations of embodiments, and equivalent substitutions based on the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for compensating electrode loss in electrical discharge machining (EDM) layered milling based on temperature field simulation, characterized in that, include: The discharge parameters, electrode material parameters, and workpiece material parameters of electrical discharge milling are obtained, and a calculation model of the temperature field of a single pulse discharge in electrical discharge milling is established based on the discharge parameters, electrode material parameters, and workpiece material parameters. The step of loading the discharge energy into the discharge channel region according to the distribution pattern of high energy density at the center and gradually decreasing energy density at the periphery to obtain the discharge temperature field distribution result is as follows: Based on the discharge temperature field distribution results, the temperature of the calculation region is solved step by step over time, and the regions where the electrode material and workpiece material reach the melting condition are determined. The steps of obtaining the electrode material removal volume and workpiece material removal volume are obtained by deleting the calculation units that reach the melting condition. The steps for calculating the electrode loss rate based on the electrode material removal volume and the workpiece material removal volume; The steps are as follows: Based on the electrode loss rate and combined with the scanning volume principle of electrical discharge milling, the electrode motion trajectory is compensated and calculated to obtain the compensated electrode motion trajectory. The steps are to generate a machining program based on the compensated electrode motion trajectory and perform electrical discharge milling.

2. The method for compensating electrode loss in EDM layered milling based on temperature field simulation according to claim 1, characterized in that, Establishing a calculation model for the temperature field of a single pulse discharge in electrical discharge milling includes establishing a three-dimensional calculation model that simultaneously includes the electrode region and the workpiece region, and setting a discharge channel region between the electrode region and the workpiece region as an energy input region.

3. The method for compensating electrode loss in EDM layered milling based on temperature field simulation according to claim 1, characterized in that, The discharge energy is applied to the discharge channel region in a distribution pattern where the energy density is high at the center and gradually decreases at the periphery. This includes maximizing the energy density in the central region of the discharge channel and gradually decreasing it with increasing distance from the discharge center to simulate the energy distribution inside the discharge channel.

4. The method for compensating electrode loss in EDM layered milling based on temperature field simulation according to claim 1, characterized in that, The time-step temperature solution involves setting an energy input boundary in the discharge channel region, setting a convective heat dissipation boundary on the surface in contact with the working fluid, and setting the boundary far from the discharge region as an adiabatic boundary to obtain the temperature field distribution results of a single pulse discharge in electrical discharge milling.

5. The method for compensating electrode loss in EDM layered milling based on temperature field simulation according to claim 1, characterized in that, Determining the region where the electrode material and workpiece material reach melting conditions involves judging the temperature of each calculation unit during the time-step temperature solution process and deleting calculation units whose temperature reaches or exceeds the material melting temperature to simulate the material removal process.

6. The method for compensating electrode loss in EDM layered milling based on temperature field simulation according to claim 1, characterized in that, Calculating the electrode loss rate involves statistically analyzing the volume of electrode material removed and the volume of workpiece material removed, and then calculating the ratio between the two volumes to obtain the electrode loss rate.

7. A device for compensating electrode loss in electrical discharge machining (EDM) layered milling based on temperature field simulation, characterized in that, include: The module obtains the discharge parameters, electrode material parameters, and workpiece material parameters of electrical discharge milling, and establishes a single-pulse discharge temperature field calculation model for electrical discharge milling based on the discharge parameters, electrode material parameters, and workpiece material parameters. The module loads the discharge energy into the discharge channel region according to the distribution pattern of high energy density at the center and gradually decreasing energy density at the periphery to obtain the discharge temperature field distribution result. Based on the discharge temperature field distribution results, the temperature of the calculation area is solved step by step over time, and the areas where the electrode material and workpiece material reach the melting condition are determined. The modules for obtaining the electrode material removal volume and workpiece material removal volume are obtained by deleting the calculation units that reach the melting condition. A module for calculating electrode loss rate based on the electrode material removal volume and the workpiece material removal volume; A module that calculates the compensation for the electrode motion trajectory based on the electrode loss rate and the scanning volume principle of electrical discharge milling to obtain the compensated electrode motion trajectory. A module that generates a machining program based on the compensated electrode motion trajectory and performs electrical discharge milling.

8. A computer storage medium for storing computer programs, characterized in that, When the computer program is read by the computer, the computer executes the method of claim 1.

9. A computer, comprising a processor and a storage medium, characterized in that, When the processor reads the computer program stored in the storage medium, the computer executes the method of claim 1.

10. A computer program product, as a computer program, is characterized by: When the computer program is executed, it implements the method of claim 1.

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