A high-precision workpiece spindle design method based on force-thermal coupling analysis

Abstract

The application discloses a high-precision workpiece spindle design method based on force-thermal coupling analysis, and belongs to the technical field of workpiece shaft transmission and thermal management of machining equipment. The method comprises the following steps: constructing a workpiece shaft force-thermal coupling model, obtaining material attribute parameters, machining parameters and environmental temperature parameters of the workpiece shaft, quantifying the coupling correlation of cutting force, temperature and shaft deformation through finite element iterative calculation; collecting stress data and temperature data of the workpiece shaft in real time; comparing the stress data with a preset stress threshold value and the temperature data with a preset temperature threshold value respectively, and judging whether the stress of the workpiece shaft exceeds the preset stress threshold value and whether the temperature exceeds the preset temperature threshold value; when the temperature exceeds the preset temperature threshold value, adjusting the machining parameters of the workpiece shaft to reduce the heat generated by friction; when the stress exceeds the preset stress threshold value, finely adjusting the shaft positioning of the workpiece shaft through a thermal deformation compensation algorithm to disperse the load. The application improves the operation stability and machining precision of the workpiece shaft.

Description

Technical Field

[0001] This invention relates to the field of workpiece shaft transmission and thermal management technology for machining equipment, specifically to a high-precision workpiece spindle design method based on force-thermal coupling analysis, applicable to scenarios such as machine tools and machining centers that require high-precision workpiece rotation. Background Technology

[0002] The workpiece axis is a core component of machining equipment such as machine tools and machining centers, and its operating accuracy directly determines the machining quality of the workpiece. During the operation of the workpiece axis, cutting forces, torque, and other force loads, along with thermal effects such as cutting heat and frictional heat, work together to cause deformation of the workpiece axis, thus affecting machining accuracy. In addition, in most cutting machining scenarios, cutting fluid continuously flows over the surface of the workpiece axis. The flow of cutting fluid not only carries away some heat, but its viscous dissipation also generates additional heat sources. At the same time, the pressure of the cutting fluid flow field acts on the surface of the workpiece axis, forming a fluid-structure interaction effect.

[0003] Existing technologies primarily improve performance by modifying the workpiece shaft structure (such as enhancing shaft strength and optimizing connection methods). In terms of control strategies, traditional designs typically treat force loads and thermal effects in isolation, calculating static deformation caused by force loads and thermal deformation caused by thermal effects separately, then linearly superimposing them to obtain the total deformation. This approach fails to consider the coupled feedback relationship between force loads, thermal effects, and deformation: deformation of the workpiece shaft under stress alters the fit clearance and contact state, thus exacerbating local frictional heat generation; thermal deformation, in turn, changes the stress distribution within the workpiece shaft, further affecting the deformation state; simultaneously, changes in the cutting fluid flow field alter the convective heat transfer intensity and viscous heat dissipation distribution, thereby affecting the temperature and structural fields. This coupling effect leads to decreased machining accuracy and accelerated shaft wear, necessitating targeted optimization solutions.

[0004] Therefore, there is an urgent need in this field for a high-precision operation optimization method for workpiece shafts that can comprehensively consider the coupled feedback relationship between force load, thermal effect and cutting fluid flow field. Summary of the Invention

[0005] This invention aims to solve the technical problems of decreased machining accuracy, increased shaft wear, and insufficient operational stability caused by the coupling of force load, frictional heat, and thermal deformation during the operation of existing workpiece shafts. By precisely controlling the force-thermal coupling, the operational stability and machining accuracy of the workpiece shaft are improved without altering the original core structure of the workpiece shaft.

[0006] To achieve the above objectives, this invention provides a high-precision workpiece spindle design method based on force-thermal coupling analysis, comprising the following steps: Constructing a workpiece spindle force-thermal coupling model. The model is constructed by acquiring the material properties, machining parameters, and ambient temperature parameters of the workpiece spindle. Using these parameters as input parameters, finite element iterative calculations are performed to quantify the coupling relationship between cutting force, temperature, and spindle deformation. Real-time acquisition of stress and temperature data of the workpiece spindle. Comparing the stress and temperature data with preset stress and temperature thresholds to determine whether the workpiece spindle temperature and stress exceed the preset thresholds, and combining this with the workpiece spindle force-thermal coupling model for analysis and calculation to obtain the stress and temperature distribution fields of the workpiece spindle under the current working conditions. When the temperature exceeds the preset temperature threshold, the machining parameters of the workpiece spindle are adjusted to reduce frictional heat generation. When it is determined that the stress exceeds the preset stress threshold, the axis positioning of the workpiece shaft is finely adjusted by a thermal deformation compensation algorithm based on the stress distribution field and the temperature distribution field to distribute the load.

[0007] Furthermore, the material property parameters include elastic modulus, thermal conductivity, density, specific heat capacity, and coefficient of thermal expansion. The machining parameters include depth of cut, feed rate, rotational speed, and cutting force. The ambient temperature parameter is the temperature value of the working environment in which the workpiece shaft is located.

[0008] Furthermore, the finite element iterative calculation includes establishing a finite element model of the workpiece shaft and the cutting fluid domain, using the cutting fluid inlet velocity and inlet temperature as flow field boundary conditions, the cutting force as structural force load boundary conditions, and the cutting heat, frictional heat, and viscous heat dissipation as temperature field thermal load boundary conditions. Displacement continuity, velocity continuity, temperature continuity, heat flux continuity, and stress equilibrium conditions are applied to the fluid-structure interaction interface. In the nth iteration step, the flow field governing equations are solved to obtain the current cutting fluid velocity field and pressure field. Based on the current cutting fluid velocity field, viscous heat dissipation is calculated, incorporated into the total heat source term, and then the temperature field governing equations are solved to obtain the current temperature distribution field. Based on the current temperature distribution field, thermal strain is calculated, and then substituted into the thermoelastic constitutive equation and geometric equations to solve the force equilibrium equations to obtain the current stress distribution field and displacement field. Based on the current displacement field, the geometry of the fluid-structure interaction interface is updated, the mesh of the flow field domain is recalculated, and the boundary conditions for the flow field solution are updated. The iteration process determines whether the stress distribution field, temperature distribution field, and flow field each satisfy a preset convergence condition. If they are satisfied, the iteration ends, and the current stress distribution field, temperature distribution field, flow field distribution, and displacement field are output. If they are not satisfied, the iteration returns to continue until the preset convergence condition is met. The preset convergence condition is: in two consecutive iterations, the relative change in the stress field is less than 1%, the change in the temperature field is less than 0.5 degrees Celsius, and the relative change in the flow field velocity is less than 5%.

[0009] Furthermore, the stress data is obtained by converting strain data collected by a strain sensor installed on the cutting end of the workpiece shaft based on the elastic modulus of the workpiece shaft material; the temperature data is collected by a temperature sensor installed on the bearing portion of the workpiece shaft.

[0010] Furthermore, the preset stress threshold is 220 MPa, and the preset temperature threshold is 75 degrees Celsius. The preset stress threshold is determined based on the yield strength of the workpiece shaft material combined with a preset safety factor, and the preset temperature threshold is determined based on the maximum allowable operating temperature of the bearing.

[0011] Furthermore, when it is determined that the temperature of the workpiece shaft exceeds the preset temperature threshold or the stress of the workpiece shaft exceeds the preset stress threshold, a load reduction warning signal is generated and issued.

[0012] Furthermore, after fine-tuning the shaft system positioning of the workpiece shaft through the thermal deformation compensation algorithm, the stress data and temperature data of the workpiece shaft are collected again in real time and judged again; if the stress still exceeds the preset stress threshold, the fine-tuning is repeated until the stress does not exceed the preset stress threshold or the maximum allowable number of compensations is reached; wherein, the fine-tuning displacement of the shaft system positioning is provided with a maximum compensation amount upper limit, and when the fine-tuning displacement exceeds the maximum compensation amount upper limit, a load reduction warning signal is generated and issued.

[0013] Furthermore, adjusting the machining parameters of the workpiece axis includes reducing the rotational speed of the workpiece axis, wherein the rotational speed is set to a minimum allowable speed; when the rotational speed drops to the minimum allowable speed and the temperature still exceeds the preset temperature threshold, a shutdown protection is triggered.

[0014] The beneficial effects achievable by this invention include: Its innovation lies in a dynamic control strategy based on force-thermal coupling, rather than structural improvements to the workpiece shaft, thus effectively circumventing the technical barriers of existing structural patents. By constructing a force-thermal coupling model of the workpiece shaft and performing dynamic control based on the model output, thermal deformation and force load concentration during workpiece shaft operation can be reduced, machining accuracy and stability can be improved, and the service life of the workpiece shaft and supporting components can be extended. The system device of this invention is easy to integrate and can be directly used for upgrading and retrofitting existing equipment without modifying the core structure of the workpiece shaft, demonstrating promising prospects for industrial applications. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a schematic diagram of the workpiece axial force thermal coupling optimization device.

[0016] Figure 2 The simulation results are shown in the figure before the optimization of the workpiece axial force thermal coupling.

[0017] Figure 3 The simulation results are shown in the figure after the workpiece axial force thermal coupling optimization. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0019] Example 1 This embodiment 1 provides a high-precision workpiece spindle optimization method based on force-thermal coupling analysis. This method can be executed by the high-precision workpiece spindle optimization system based on force-thermal coupling analysis described below. Figure 1 As shown, it includes the following steps: Step S1, construct the workpiece shaft force-thermal coupling model: obtain the material property parameters, machining parameters and ambient temperature parameters of workpiece shaft 1, use the material property parameters, machining parameters and ambient temperature parameters as input parameters, and quantify the coupling relationship between cutting force, temperature and shaft deformation through finite element iterative calculation; Step S2: Real-time acquisition of stress and temperature data for workpiece shaft 1; Step S3: Compare the stress data with a preset stress threshold and the temperature data with a preset temperature threshold to determine whether the temperature of workpiece shaft 1 exceeds the preset temperature threshold and whether the stress of workpiece shaft 1 exceeds the preset stress threshold. Combine the workpiece shaft force-thermal coupling model for analysis and calculation to obtain the stress distribution field and temperature distribution field of workpiece shaft 1 under the current working condition. Step S4: When it is determined that the temperature exceeds the preset temperature threshold, adjust the machining parameters of the workpiece shaft 1 to reduce the heat generated by friction. Step S5: When it is determined that the stress exceeds the preset stress threshold, the axis positioning of the workpiece shaft 1 is finely adjusted by the thermal deformation compensation algorithm according to the stress distribution field and the temperature distribution field to distribute the load. Step S6: When it is determined that the temperature of the workpiece shaft 1 exceeds the preset temperature threshold or the stress of the workpiece shaft 1 exceeds the preset stress threshold, a load reduction warning signal is generated and issued. The above steps S1 to S5 constitute a complete force-thermal coupling state monitoring and control process; after the control is completed in step S4 or step S5, return to step S2 to continue to collect stress data and temperature data of workpiece shaft 1 in real time, thus forming a closed-loop control process of "collection - judgment - control - re-collection".

[0020] Example 2 like Figure 1 As shown, Embodiment 2 provides a high-precision workpiece spindle optimization system based on force-thermal coupling analysis, including a sensing module 9, a data processing module 10, and an execution module 11. The workpiece spindle 1 is supported in the housing by a front bearing 2 and a rear bearing 3. One end of the workpiece spindle 1 is the cutting end 5, and the other end is the driving end connected to the driving device.

[0021] The sensing module 9 is used to collect stress and temperature data of the workpiece shaft 1 in real time. Specifically, the sensing module 9 includes a strain sensor 8 and a temperature sensor 7. The strain sensor 8 is installed at the cutting end 5 of the workpiece shaft 1 and at the front bearing 2 and the rear bearing 3, and is used to collect the stress data. The temperature sensor 7 is installed at the bearing portion of the workpiece shaft 1. Specifically, the temperature sensor 7 includes a first temperature sensor installed at the front bearing 2 and a second temperature sensor installed at the rear bearing 3, and is used to collect temperature data of the workpiece shaft 1.

[0022] The data processing module 10 is communicatively connected to the sensing module 9. The data processing module 10 stores a preset stress threshold, a preset temperature threshold, and a workpiece axial force thermal coupling model. The workpiece axial force thermal coupling model is a model constructed through finite element iterative calculations to quantify the coupling relationship between cutting force, temperature, and shaft deformation. The data processing module 10 is used to analyze and calculate based on the stress data and temperature data, combined with the workpiece axial force thermal coupling model, and generates a control command when it determines that the stress of the workpiece shaft 1 exceeds the preset stress threshold or the temperature of the workpiece shaft 1 exceeds the preset temperature threshold.

[0023] Preferably, the data processing module 10 is an industrial computer or embedded controller, which internally stores the kernel of the finite element analysis software and the parameters of the force-thermal coupling model. The finite element analysis software adopts the ANSYS Workbench platform or the OpenFOAM open source platform.

[0024] Furthermore, the data processing module 10 is also used to: generate a load reduction warning command when it is determined that the stress of the workpiece shaft 1 exceeds a preset stress threshold or the temperature of the workpiece shaft 1 exceeds a preset temperature threshold; the execution module 11 is also used to execute the load reduction warning command and issue a load reduction warning signal.

[0025] The preset stress threshold is 220 MPa, and the preset temperature threshold is 75 degrees Celsius.

[0026] The execution module 11 is communicatively connected to the data processing module 10 and is used to receive and execute the control commands. The control commands include machining parameter adjustment commands, shaft positioning fine-tuning commands, and load reduction warning commands. Preferably, the execution module 11 includes a speed regulator 12 and a positioning fine-tuning mechanism 13. The speed regulator 12 is used to execute the speed adjustment in the machining parameter adjustment commands, and the positioning fine-tuning mechanism 13 is used to execute the shaft positioning fine-tuning commands.

[0027] Its working principle is as follows: The sensing module 9 collects stress and temperature data of the workpiece shaft 1 in real time and transmits them to the data processing module 10; the data processing module 10 compares the real-time collected stress data with the preset stress threshold and the temperature data with the preset temperature threshold to determine whether the stress and temperature of the workpiece shaft 1 exceed the threshold. Combined with the workpiece shaft force-thermal coupling model, the module performs finite element iterative calculation with the processing parameters and the real-time collected temperature data as boundary conditions to obtain the flow field distribution, stress distribution field and temperature distribution field under the current working condition; when it is determined that the threshold is exceeded, a corresponding control command is generated; the execution module 11 receives and executes the control command to realize the dynamic control of the force-thermal coupling state.

[0028] It should be further explained that the core of this invention lies in constructing the workpiece axial force thermal coupling model. This model comprehensively considers the bidirectional coupling of the cutting fluid flow field, temperature field, and structural field, and its basic governing equations are as follows: (a) Governing equations for the flow field; The flow of cutting fluid on the surface of workpiece shaft 1 is controlled by the following Navier-Stokes equations: ; in, This refers to the density of the cutting fluid, expressed in kilograms per cubic meter. This is the cutting fluid velocity vector, in meters per second. Time, in seconds; For gradient operators; This refers to the cutting fluid pressure, measured in Pascals. This refers to the dynamic viscosity of the cutting fluid, measured in Pascals per second. This is a volume force vector, with units of Newtons per cubic meter.

[0029] Under the assumption of steady-state cutting fluid flow The above equation simplifies to: ; (ii) Control equations for the temperature field in the cutting fluid domain; The temperature distribution in the cutting fluid domain is governed by the following temperature field equations considering convection: ; in, This refers to the density of the cutting fluid, expressed in kilograms per cubic meter. The specific heat capacity of the cutting fluid at constant pressure is expressed in joules per kilogram of Kelvin. This refers to the temperature field of the cutting fluid, expressed in Kelvin or degrees Celsius. This is the cutting fluid velocity vector, derived from the flow field equations, and its unit is meters per second. For gradient operators; This refers to the thermal conductivity of the cutting fluid, measured in watts per meter Kelvin. For viscous heat dissipation, the unit is watts per cubic meter.

[0030] Under steady-state operating conditions The above equation simplifies to: ; (III) Control equations for the temperature field in the solid domain of the workpiece shaft; The temperature distribution field of workpiece shaft 1 is controlled by the following heat conduction equation: ; in, The density of the material of workpiece shaft 1 is expressed in kilograms per cubic meter. The isobaric specific heat capacity of the material of workpiece shaft 1 is expressed in joules per kilogram Kelvin. Temperature field of the workpiece shaft, in Kelvin or degrees Celsius; Time, in seconds; For gradient operators; Here is the thermal conductivity of the material of workpiece shaft 1, in watts per meter Kelvin; For cutting heat, Both are frictional heat, and their units are watts per cubic meter. Under steady-state conditions, The equation simplifies to .

[0031] (iv) Heat source coupling mechanism; The volumetric heat source includes cutting heat. Frictional heat and viscous heat dissipation The viscous heat dissipation is generated by the viscous dissipation of the cutting fluid flow field, and the calculation formula is: ; in, This is the temperature-dependent dynamic viscosity of the cutting fluid, expressed in Pascal-seconds. Temperature field, measured in Kelvin or degrees Celsius; " indicates a double dot product operation.

[0032] (v) Structural field governing equations; The stress distribution field of workpiece shaft 1 is controlled by the following force balance equations: ; in, is the stress tensor, measured in Pascals; This is a volume force vector, with units of Newtons per cubic meter. During the workpiece's shaft movement, the main volume force is centrifugal force.

[0033] The strain-displacement relationship of workpiece shaft 1 is described by the following geometric equation: ; in, The strain tensor is dimensionless; This is a displacement vector, with units in meters.

[0034] The material constitutive relation of workpiece shaft 1 is described by the following thermoelastic constitutive equation: ; ; in, It is a fourth-order elastic tensor, with units of Pascals; The thermal strain tensor is dimensionless. Here is the coefficient of thermal expansion of the material of workpiece shaft 1, in Kelvin; Temperature field of the workpiece shaft; The reference temperature is the temperature under no thermal stress conditions, usually taken as the ambient temperature parameter, and the unit is Kelvin or Celsius.

[0035] (vi) Fluid-structure interaction interface conditions; At the fluid-structure interaction interface That is, the interface between the workpiece shaft 1 surface and the cutting fluid must meet the following coupling conditions: Displacement continuity: ; Continuous speed: ; Temperature continuity: ; Continuous heat flux: ; Stress balance: ; in, This represents the displacement of the flow field side interface, in meters; This represents the displacement of the structural field-side interface, in meters. This is the initial interface position, in meters; The velocity at the flow field side interface is expressed in meters per second. The temperature of the flow field side interface. The values ​​represent the structural field-side interface temperature, all in Kelvin or degrees Celsius. The thermal conductivity of the cutting fluid, The value represents the thermal conductivity of the workpiece shaft material, with units of watts per meter Kelvin. The stress at the flow field side interface consists of flow field pressure and viscous stress, and its unit is Pascal. It is the normal unit vector of the fluid-structure interaction interface, pointing from the structural domain to the flow field domain; The stress at the structural field-side interface is expressed in Pascals.

[0036] The above interface conditions constitute a complete coupling closed loop: the flow field pressure acts on the workpiece shaft surface to produce structural deformation (displacement / velocity coupling); the flow field velocity determines the convective heat transfer intensity on the workpiece shaft surface through the conditions of temperature continuity and heat flux continuity, affecting the workpiece shaft temperature field (temperature / heat flux coupling); the workpiece shaft temperature field affects the structural field through thermal strain (thermoelastic coupling); structural deformation changes the geometric boundary of the flow field, thereby affecting the flow field distribution (displacement coupling).

[0037] (vii) Finite element iterative calculation method; Based on the above governing equations, the specific steps of the finite element iterative calculation are as follows: The first step is to establish a finite element model of the workpiece shaft 1 and the cutting fluid domain. The inlet velocity and temperature of the cutting fluid are used as the flow field boundary conditions, the cutting force as the structural force load boundary conditions, and the cutting heat, frictional heat, and viscous heat dissipation as the temperature field thermal load boundary conditions. At the fluid-structure interaction interface... The conditions of continuous displacement, continuous velocity, continuous temperature, continuous heat flux, and stress equilibrium are applied.

[0038] The second step, in the In the next iteration, the flow field control equations are solved to obtain the current cutting fluid velocity field. and pressure field .

[0039] The third step is to determine the current cutting fluid velocity field. Calculate viscous heat dissipation , into total heat source item Then, the governing equations for the temperature field in the cutting fluid domain are solved to obtain the current cutting fluid temperature distribution field. Then, solve the governing equations for the temperature field in the solid domain of the workpiece shaft to obtain the current temperature distribution field of the workpiece shaft. .

[0040] The fourth step is to determine the current workpiece shaft temperature distribution field. Calculate thermal strain Then, substituting the thermoelastic constitutive equation and geometric equation, the force equilibrium equation is solved to obtain the current stress distribution field. and displacement field .

[0041] Fifth step, based on the current displacement field Update the fluid-structure interaction interface The geometry is determined, the mesh of the flow field domain is recalculated, and the boundary conditions for the flow field solution are updated.

[0042] Step 6: Determine whether the stress distribution field, temperature distribution field, and flow field each satisfy a preset convergence condition. If satisfied, the iteration ends, and the current stress distribution field, temperature distribution field, flow field distribution, and displacement field are output; if not satisfied, return to step 2 and proceed to step 6. The next iteration.

[0043] Preferably, the preset convergence condition is: when the relative change in the stress field is less than one percent, the change in the temperature field is less than 0.5 degrees Celsius, and the relative change in the flow field velocity is less than five percent in two adjacent iterations, it is determined to be converged.

[0044] In the above iterative calculation process, a complete coupling feedback is formed between the flow field, temperature field, and structural field. Flow velocity affects convective heat transfer and viscous heat dissipation, temperature affects material properties and thermal strain, thermal strain affects stress distribution and structural displacement, and structural displacement changes the geometric boundary of the flow field, thus affecting the flow field distribution. Through the above finite element iterative calculation, the coupling relationship between cutting force, temperature, and shaft deformation can be accurately quantified.

[0045] After constructing the workpiece axial force-thermal coupling model, stress and temperature data of workpiece shaft 1 are collected in real time.

[0046] Specifically, strain sensors 8 are installed at the cutting end 5 of the workpiece shaft 1, as well as at the front bearing 2 and the rear bearing 3. Temperature sensors 7 are installed at the bearing locations of the workpiece shaft 1. The strain sensors 8 collect strain data of the workpiece shaft 1 in real time, and convert the strain data into stress data based on the elastic modulus of the workpiece shaft 1 material. The temperature sensors 7 collect temperature data of the workpiece shaft 1 in real time. The strain sensors 8 and the temperature sensors 7 constitute a sensing module 9, used for online monitoring of the force-thermal coupling state.

[0047] Preferably, the strain sensor 8 is a resistance strain gauge, which is attached to the outer circumferential surface of the cutting end 5 of the workpiece shaft 1. The temperature sensor 7 can be a type K thermocouple, which is a nickel-chromium / nickel-silicon thermocouple, and is installed on the outside of the bearing part of the workpiece shaft 1.

[0048] Based on the stress data and temperature data, and combined with the workpiece axial force thermal coupling model, analysis and calculation are performed to determine whether the temperature of workpiece shaft 1 exceeds a preset temperature threshold and whether the stress of workpiece shaft 1 exceeds a preset stress threshold.

[0049] Specifically, the real-time collected stress data is compared with a preset stress threshold, and the real-time collected temperature data is compared with a preset temperature threshold to determine whether the stress and temperature of workpiece shaft 1 exceed the threshold. At the same time, using the processing parameters and the real-time collected temperature data as boundary conditions, the workpiece shaft force-thermal coupling model is solved in the forward direction according to the above-mentioned finite element iterative calculation method to obtain the flow field distribution, stress distribution field and temperature distribution field of workpiece shaft 1 under the current working condition, providing a data basis for the thermal deformation compensation algorithm.

[0050] The preset stress threshold is 220 MPa, and the preset temperature threshold is 75 degrees Celsius. The preset stress threshold is determined based on the yield strength of the workpiece shaft 1 material combined with a preset safety factor, and the preset temperature threshold is determined based on the maximum allowable operating temperature of the bearing. When the stress exceeds 220 MPa, the safety margin of the workpiece shaft 1 is insufficient, and the operating accuracy and reliability decrease significantly; when the temperature exceeds 75 degrees Celsius, the bearing lubrication performance decreases significantly, and wear intensifies.

[0051] When the temperature of workpiece shaft 1 exceeds the preset temperature threshold, the machining parameters of workpiece shaft 1 are adjusted to reduce frictional heat generation.

[0052] Specifically, when the temperature of the workpiece shaft 1 exceeds the preset temperature threshold of 75 degrees Celsius, the data processing module 10 generates a machining parameter adjustment instruction, and the execution module 11 receives and executes the adjustment instruction.

[0053] The adjustment instructions include at least one of the following: reducing the rotational speed of the workpiece shaft 1 to reduce the relative motion speed of the shaft friction pair, thereby reducing the rate of frictional heat generation; adjusting the cutting parameters, such as reducing the depth of cut and reducing the feed rate, to reduce the cutting force and thus reduce the generation of cutting heat, i.e., adjusting the matching ratio between the rotational speed and the cutting parameters; and simultaneously reducing the rotational speed and adjusting the cutting parameters.

[0054] Preferably, the speed adjustment is provided with a minimum safe speed limit. When the speed drops to the minimum allowable speed and the temperature still exceeds the threshold, the data processing module 10 triggers a shutdown protection command, and the execution module 11 performs shutdown protection to avoid equipment damage.

[0055] When the stress on workpiece shaft 1 is determined to exceed the preset stress threshold, the shaft system positioning of workpiece shaft 1 is finely adjusted through a thermal deformation compensation algorithm to distribute the load.

[0056] Specifically, when the stress on the workpiece shaft 1 exceeds the preset stress threshold of 220 MPa, the data processing module 10 generates a shaft positioning fine-tuning instruction, and the execution module 11 receives and executes the shaft positioning fine-tuning instruction.

[0057] The basic principle of the thermal deformation compensation algorithm is as follows: based on the current stress distribution field and temperature distribution field output by the workpiece axial force thermal coupling model, the shaft positioning offset caused by thermal deformation is calculated. ,in The displacement field at the current temperature, The displacement field is at the reference temperature. Then, the positioning fine-tuning mechanism 13 is driven by the execution module 11 to generate a reverse fine-tuning displacement. This compensates for positioning errors caused by thermal deformation, thereby dispersing concentrated stress to a larger load-bearing area.

[0058] The specific execution steps of the thermal deformation compensation algorithm are as follows: Step 1: Extract the current temperature field from the workpiece axial force thermal coupling model. and reference temperature field .

[0059] Step 2: Call the finite element solver to calculate the current temperature field. Displacement field under and reference temperature field Displacement field under During the calculation, the temperature field is input as a thermal load boundary condition into the thermoelastic constitutive equation, and the displacement vectors of each node are obtained by solving the equation.

[0060] Step 3, calculate the offset Offset It is a vector, containing axial offset components. and radial offset component .

[0061] Step 4, based on the offset Generate reverse fine-tuning displacement command Fine-tuning displacement commands include axial fine-tuning displacement commands. and radial fine-tuning displacement command .

[0062] Step 5: The data processing module 10 sends the fine-tuning displacement command to the execution module 11, and the execution module 11 drives the positioning fine-tuning mechanism 13 to move according to the command. The positioning fine-tuning mechanism 13 includes a servo motor and a ball screw transmission mechanism, or a piezoelectric ceramic actuator, used to achieve axial and radial position adjustment with micron-level precision.

[0063] Step six: After fine-tuning, sensor module 9 re-collects stress and temperature data, and data processing module 10 performs threshold judgment again to verify whether the stress has dropped below the preset stress threshold. If it still does not meet the standard, steps one through five are repeated until the stress meets the requirements or the maximum allowable number of compensations is reached.

[0064] Preferably, the shaft positioning fine-tuning is achieved by adjusting the preload or axial position of the front bearing 2 or the rear bearing 3. The shaft positioning fine-tuning displacement has a maximum compensation limit. When the calculated fine-tuning displacement exceeds the maximum compensation limit, the data processing module 10 generates a load reduction warning command to prompt the operator to intervene or trigger the automatic load reduction program.

[0065] When it is determined that the temperature of workpiece shaft 1 exceeds the preset temperature threshold or the stress of workpiece shaft 1 exceeds the preset stress threshold, a load reduction warning signal is generated and issued.

[0066] Specifically, when the data processing module 10 determines that the stress of the workpiece shaft 1 exceeds a preset stress threshold of 220 MPa or the temperature of the workpiece shaft 1 exceeds a preset temperature threshold of 75 degrees Celsius, it generates a load reduction warning command; the execution module 11 receives and executes the load reduction warning command and issues a load reduction warning signal.

[0067] Preferably, the load reduction warning signal includes at least one of the following forms: audible and visual alarm signal, display screen prompt signal, and remote monitoring alarm signal.

[0068] Example 3 Using the above method and system, force-thermal coupling optimization simulation verification was performed on the workpiece shaft of a certain type of machining center.

[0069] The simulation conditions are as follows: the workpiece shaft 1 is made of 40Cr steel with an elastic modulus of 206 GPa, a thermal conductivity of 45 W / m Kelvin, a density of 7850 kg / m³, a specific heat capacity of 460 J / kg Kelvin, and a coefficient of thermal expansion of [missing information]. Per Kelvin. Cutting force: 5000 Newtons; Rotation speed: 3000 rpm; Ambient temperature: 25°C; Cutting fluid: water-based, density: 1000 kg / m³, dynamic viscosity: 0.001 Pascal-second, inlet flow rate: 5 m / s, inlet temperature: 20°C; Preset stress threshold: 220 MPa; Preset temperature threshold: 75°C.

[0070] Based on the aforementioned finite element iterative calculation method, a finite element model of the workpiece shaft 1 and the cutting fluid domain was established in the ANSYS Workbench finite element analysis software platform. Cutting force was used as the structural force load boundary condition, cutting heat, frictional heat, and viscous heat dissipation were used as the temperature field thermal load boundary condition, and the cutting fluid inlet velocity and inlet temperature were used as the flow field boundary condition at the fluid-structure interaction interface. The conditions of displacement continuity, velocity continuity, and stress equilibrium are applied, and an iterative solution is performed. The simulation results are as follows: Figure 2 and Figure 3 As shown.

[0071] The simulation results before optimization are as follows: Without using the force-thermal coupling optimization method of this invention, the maximum stress of workpiece shaft 1 is 285 MPa, exceeding the preset stress threshold of 220 MPa, and the highest temperature is 92 degrees Celsius, exceeding the preset temperature threshold of 75 degrees Celsius. The stress concentration area is located at the mounting positions of the front bearing 2 and the rear bearing 3, and the highest temperature area is located at the cutting end 5. The cutting fluid flow field forms eddies at the cutting end 5, leading to local heat transfer deterioration.

[0072] The optimized simulation results are as follows: Using the force-thermal coupling optimization method of this invention, by adjusting the rotation speed to 2400 rpm, reducing the depth of cut and feed rate, and fine-tuning the shaft positioning, the maximum stress on workpiece shaft 1 is reduced to 195 MPa, lower than the preset stress threshold of 220 MPa, and the highest temperature is reduced to 68 degrees Celsius, lower than the preset temperature threshold of 75 degrees Celsius. The stress distribution is more uniform, the temperature gradient is significantly reduced, and the cutting fluid flow field tends to be stable.

[0073] The simulation results show that the present invention can effectively reduce thermal deformation and force load concentration during the operation of the workpiece shaft through precise control of force-thermal coupling, improve the stability of machining accuracy, and extend the service life of the workpiece shaft and supporting components.

[0074] Example 4 The above methods and systems were applied to optimize the workpiece axis movement of a certain type of CNC lathe.

[0075] The specific implementation steps are as follows: First, a strain sensor 8 is installed at the cutting end 5 of the workpiece shaft 1, and a temperature sensor 7 is installed at the bearing portion of the workpiece shaft 1. The sensor signal lines are then connected to the data processing module 10. A flow meter and a thermometer are installed at the cutting fluid supply line to monitor the cutting fluid flow field parameters.

[0076] The second step involves setting the stress threshold to 220 MPa and the temperature threshold to 75 degrees Celsius in the data processing module 10, and loading the pre-built workpiece axial force thermal coupling model.

[0077] The third step is to start the machine tool for processing. The sensing module 9 collects stress and temperature data of the workpiece shaft 1 in real time and transmits them to the data processing module 10.

[0078] In the fourth step, the data processing module 10 analyzes and calculates the received stress and temperature data in conjunction with the workpiece axial force-thermal coupling model to determine in real time whether the stress and temperature of the workpiece shaft 1 exceed the threshold.

[0079] Fifth, when the temperature exceeds 75 degrees Celsius, the data processing module 10 generates a machining parameter adjustment command, and the execution module 11 reduces the spindle speed and adjusts the cutting parameters to reduce the cutting force, thereby reducing frictional heat generation and cutting heat generation. If the speed drops to the minimum allowable speed and the temperature still exceeds the threshold, a shutdown protection is triggered.

[0080] Step 6: When the stress exceeds 220 MPa, the data processing module 10 generates a shaft positioning fine-tuning command. The execution module 11 then fine-tunes the shaft positioning by adjusting the preload of the front bearing 2 or the rear bearing 3, dispersing the concentrated stress to a larger load-bearing area. If the fine-tuning displacement exceeds the maximum compensation limit, a load reduction warning command is generated.

[0081] Step 7: When the temperature exceeds 75 degrees Celsius or the stress exceeds 220 MPa, the data processing module 10 generates a load reduction warning command, and the execution module 11 issues an audible and visual alarm signal to alert the operator.

[0082] Actual processing verification shows that after adopting the method and system of this invention, the temperature rise and stress peak of the workpiece shaft are significantly reduced, the stability of processing accuracy is significantly improved, and the wear rate of the shaft system is significantly reduced.

[0083] The system device of the present invention is easy to integrate and can be directly used for upgrading and transforming existing equipment without changing the core structure of the workpiece shaft. It has good industrial application prospects and promotion value.

Claims

1. A high-precision workpiece spindle design method based on force-thermal coupling analysis, characterized in that, Includes the following steps: A workpiece axial force-thermal coupling model is constructed as follows: the material property parameters, machining parameters, and ambient temperature parameters of the workpiece shaft are obtained, and the material property parameters, machining parameters, and ambient temperature parameters are used as input parameters. The coupling relationship between cutting force, temperature, and shaft deformation is quantified through finite element iterative calculation. The stress and temperature data of the workpiece shaft are collected in real time. The stress data is compared with a preset stress threshold, and the temperature data is compared with a preset temperature threshold to determine whether the temperature of the workpiece shaft exceeds the preset temperature threshold and whether the stress of the workpiece shaft exceeds the preset stress threshold. The stress distribution field and temperature distribution field of the workpiece shaft under the current working condition are obtained by combining the force-thermal coupling model of the workpiece shaft for analysis and calculation. When it is determined that the temperature exceeds the preset temperature threshold, the machining parameters of the workpiece shaft are adjusted to reduce the heat generated by friction. When it is determined that the stress exceeds the preset stress threshold, the axis positioning of the workpiece shaft is finely adjusted by a thermal deformation compensation algorithm based on the stress distribution field and the temperature distribution field to distribute the load.

2. The high-precision workpiece spindle design method based on force-thermal coupling analysis according to claim 1, characterized in that, The material properties parameters include elastic modulus, thermal conductivity, density, specific heat capacity, and coefficient of thermal expansion; the machining parameters include depth of cut, feed rate, rotational speed, and cutting force; and the ambient temperature parameter is the temperature value of the working environment in which the workpiece shaft is located.

3. The high-precision workpiece spindle design method based on force-thermal coupling analysis according to claim 1, characterized in that, The finite element iterative calculation includes the following steps: A finite element model of the workpiece shaft and the cutting fluid domain is established. The inlet velocity and inlet temperature of the cutting fluid are used as the flow field boundary conditions, the cutting force is used as the structural field force load boundary conditions, and the cutting heat, frictional heat and viscous heat dissipation are used as the temperature field heat load boundary conditions. The conditions of continuous displacement, continuous velocity, continuous temperature, continuous heat flux and stress balance are applied on the fluid-structure interaction interface. In the In the next iteration, the flow field control equations are solved to obtain the current cutting fluid velocity field. and pressure field The flow field governing equations are the steady-state Navier-Stokes equations: ； in, This refers to the density of the cutting fluid, expressed in kilograms per cubic meter. This is the cutting fluid velocity vector, in meters per second. For gradient operators; This refers to the cutting fluid pressure, measured in Pascals. This refers to the dynamic viscosity of the cutting fluid, measured in Pascals per second. This is a volume force vector, with units of Newtons per cubic meter; Based on the current cutting fluid velocity field Calculate the viscous heat dissipation of the cutting fluid domain. ,in, Indicates the current cutting fluid temperature The dynamic viscosity of the cutting fluid is as follows: "" indicates a double dot product operation; then, the control equations for the temperature field in the cutting fluid domain are solved to obtain the current cutting fluid temperature distribution field. The temperature field control equation for the cutting fluid domain is a steady-state convective heat transfer equation: ； in, This refers to the temperature field of the cutting fluid, expressed in Kelvin or degrees Celsius. The specific heat capacity of the cutting fluid at constant pressure is expressed in joules per kilogram of Kelvin. This refers to the thermal conductivity of the cutting fluid, measured in watts per meter Kelvin. For viscous heat dissipation, the unit is watts per cubic meter; Solve the governing equations of the workpiece shaft solid domain temperature field to obtain the current workpiece shaft temperature distribution field. The temperature field control equation for the solid domain of the workpiece shaft is a steady-state heat conduction equation: ； in, Temperature field of the workpiece shaft, in Kelvin or degrees Celsius; The density of the workpiece shaft material is expressed in kilograms per cubic meter. The specific heat capacity under constant pressure of the workpiece shaft material, expressed in joules per kilogram Kelvin. The thermal conductivity of the workpiece shaft material is expressed in watts per meter Kelvin. For cutting heat, Both are frictional heat, and their units are watts per cubic meter. Based on the current workpiece shaft temperature distribution field Calculate thermal strain Then, substituting the thermoelastic constitutive equation and geometric equation, the force equilibrium equation is solved to obtain the current stress distribution field. and displacement field The force balance equation is: The geometric equation is: The thermoelastic constitutive equation is: , ;in, For stress tensor, It is a volume force vector. For strain tensor, It is a displacement vector. It is a fourth-order elastic tensor. For thermal strain tensor, The coefficient of thermal expansion of the workpiece shaft material. The reference temperature is taken from the ambient temperature parameter; Based on the current displacement field The geometry of the fluid-structure interaction interface is updated, the mesh of the flow field domain is recalculated, and the boundary conditions for the flow field solution are updated; the fluid-structure interaction interface condition is: displacement continuity. Continuous speed Temperature continuous Continuous heat flux Stress balance ;in, This represents the displacement of the flow field side interface. This represents the displacement of the structural field-side interface. This is the initial interface position. The velocity at the flow field side interface, The temperature of the flow field side interface. The values ​​represent the structural field-side interface temperature, all in Kelvin or degrees Celsius. The thermal conductivity of the cutting fluid, The value represents the thermal conductivity of the workpiece shaft material, with units of watts per meter Kelvin. The stress at the flow field side interface consists of flow field pressure and viscous stress, and its unit is Pascal. The normal unit vector of the fluid-structure interaction interface points from the structural domain to the flow field domain. Time, in seconds; The stress at the structural field-side interface is expressed in Pascals. Determine whether the stress distribution field, the workpiece shaft temperature distribution field, and the flow field satisfy the preset convergence conditions. If they are satisfied, the iteration ends, and the current stress distribution field, temperature distribution field, flow field distribution, and displacement field are output. If they are not satisfied, return to continue iterating until the preset convergence conditions are satisfied. The preset convergence conditions are: in two adjacent iterations, the relative change of the stress field is less than 1%, the change of the temperature field is less than 0.5 degrees Celsius, and the relative change of the flow field velocity is less than 5%.

4. The high-precision workpiece spindle design method based on force-thermal coupling analysis according to claim 1, characterized in that, The stress data is obtained by converting strain data collected by a strain sensor installed on the cutting end of the workpiece shaft based on the elastic modulus of the workpiece shaft material; the temperature data is collected by a temperature sensor installed on the bearing part of the workpiece shaft.

5. The high-precision workpiece spindle design method based on force-thermal coupling analysis according to claim 1, characterized in that, The preset stress threshold is 220 MPa, and the preset temperature threshold is 75 degrees Celsius; wherein, the preset stress threshold is determined based on the yield strength of the workpiece shaft material combined with a preset safety factor, and the preset temperature threshold is determined based on the maximum allowable operating temperature of the bearing.

6. The high-precision workpiece spindle design method based on force-thermal coupling analysis according to claim 1, characterized in that, Also includes: When it is determined that the temperature of the workpiece shaft exceeds the preset temperature threshold or the stress of the workpiece shaft exceeds the preset stress threshold, a load reduction warning signal is generated and issued.

7. The high-precision workpiece spindle design method based on force-thermal coupling analysis according to claim 1, characterized in that, Also includes: After fine-tuning the shaft system positioning of the workpiece shaft using the thermal deformation compensation algorithm, the stress and temperature data of the workpiece shaft are collected again in real time and the judgment is made again. If the stress still exceeds the preset stress threshold, the fine-tuning is repeated until the stress does not exceed the preset stress threshold or the maximum number of allowable compensations is reached; wherein, the fine-tuning displacement of the shaft positioning is provided with a maximum compensation limit, and when the fine-tuning displacement exceeds the maximum compensation limit, a load reduction warning signal is generated and issued.

8. The high-precision workpiece spindle design method based on force-thermal coupling analysis according to claim 1, characterized in that, Adjusting the machining parameters of the workpiece axis includes reducing the rotational speed of the workpiece axis, which has a minimum allowable rotational speed; when the rotational speed drops to the minimum allowable rotational speed and the temperature still exceeds the preset temperature threshold, a shutdown protection is triggered.

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