CN115329631A - Laser cutting thermal error compensation method based on digital twinning - Google Patents

Laser cutting thermal error compensation method based on digital twinning Download PDF

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CN115329631A
CN115329631A CN202210908952.8A CN202210908952A CN115329631A CN 115329631 A CN115329631 A CN 115329631A CN 202210908952 A CN202210908952 A CN 202210908952A CN 115329631 A CN115329631 A CN 115329631A
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heat
cutting
boundary
thermal
thermal deformation
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路畅
费继友
苏永振
吕玉涛
孟祥忠
陈永明
刘鲁铭
田建明
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PLA Army Academy of Artillery and Air Defense
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
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    • G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
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    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
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    • G06F—ELECTRIC DIGITAL DATA PROCESSING
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Abstract

A laser cutting thermal error compensation method based on digital twinning comprises the following steps: s1, establishing a laser heat source model; s2, establishing a thermal deformation theoretical model; setting deformation boundary conditions through three basic modes of heat conduction, heat convection and heat radiation, and describing thermal deformation through thermal expansion; s3, establishing a finite element model; establishing a finite element model according to boundary conditions of the finite element model and parameters of a workpiece, verifying the rationality of the finite element model by using manufacturer recommended parameters, and generating a discretized real-time processing data set when the judgment is reasonable; s4, predicting thermal deformation in the cutting process by taking the discrete real-time processing data set as a training data set of a machine learning algorithm to generate a thermal deformation prediction cloud picture; s5, cutting; and driving virtual and real information transmission through a digital twinning technology, and compensating the cutting speed in real time according to the size of the cutting thermal deformation. This application can reduce joint-cutting department heat altered shape volume, rationally avoids thermal error, improves laser cutting precision.

Description

Laser cutting thermal error compensation method based on digital twinning
Technical Field
The invention belongs to the technical field of laser cutting, and particularly relates to a laser cutting thermal error compensation method based on digital twinning.
Background
Laser cutting is widely used with high speed and high precision, and the overall precision is determined by machine tool performance, laser performance, workpiece properties, machining parameters and machining phenomena, as shown in fig. 1. The machine tool performance and the attenuation period of the laser generator are long, and the machine tool performance and the attenuation period are difficult to study as main characterization factors of real-time machining precision. When the material of the workpiece is constant, the machining parameters and the thermal phenomenon in the cutting process play a decisive role in the machining precision. During cutting, the surface temperature field and the structural field of the workpiece form a solid-heat coupling, so that a thermal expansion phenomenon is generated, and the cutting speed is a determining factor of the heat absorption of the workpiece. Therefore, the cutting speed is selected as a main characteristic factor and compensation parameter of the laser cutting precision variation.
Most of the existing laser cutting parameter optimization schemes are empirical models, cutting speed is adjusted according to a large number of processing results, cutting precision is further improved, time and labor are consumed, economic cost is high, and the influence of the change of the motion state of a laser generator on a time dimension on cutting seams is not fully considered.
Disclosure of Invention
In order to reduce time and economic cost and improve the precision of laser cutting, the invention provides a laser cutting thermal error compensation method based on digital twinning, and the specific scheme is as follows:
a laser cutting thermal error compensation method based on digital twinning comprises the following steps:
s1, establishing a laser heat source model;
s2, establishing a thermal deformation theoretical model; setting boundary conditions of deformation through three basic modes of heat conduction, heat convection and heat radiation, and describing thermal deformation through thermal expansion according to the boundary conditions;
s3, establishing a finite element model; establishing a model according to boundary conditions of the finite element model and parameters of the workpiece, verifying the rationality of the finite element model by using factory recommended parameters, and generating a discretized real-time processing data set when the judgment is reasonable;
s4, predicting thermal deformation in the cutting process by taking the discrete real-time processing data set as a training data set of a machine learning algorithm to generate a thermal deformation prediction cloud picture;
s5, cutting; and driving virtual and real information transmission through a digital twinning technology, and compensating the cutting speed in real time according to the size of the cutting thermal deformation.
Specifically, step S5 also generates a visualized thermo-graphic digital model.
Specifically, the heat source model in step S1 is specifically as follows:
the heat flux density of the laser heat source is expressed as
Figure BDA0003773428190000027
Figure BDA0003773428190000021
In the formula q m The maximum heat flow at the center of the heat source, P is the total power of the heat source, K is the heat source concentration coefficient, and (X, Y) is the distance between the point (X, Y) and the maximum heat source point in the X direction and the Y direction.
Specifically, the boundary conditions for deformation set by three basic ways of heat conduction, heat convection and heat radiation are specifically as follows:
Figure BDA0003773428190000022
the first type of boundary condition is used for describing temperature distribution on the system boundary, gamma is a boundary range, T is temperature, and T is time; wherein T + Γ1 Constant, is a steady state condition, and when T (Γ, T) is expressed as a function of time, is an unsteady state heat source; the second class of boundary conditions describes whether heat flows in or out of the boundary, q s Is heat flux density of, wherein
Figure BDA0003773428190000023
Is the direction of the normal outside the system boundary; when in use
Figure BDA0003773428190000024
When, it is an adiabatic boundary; when the temperature is higher than the set temperature
Figure BDA0003773428190000025
When the constant value is constant, the constant heat flow boundary is formed; when in use
Figure BDA0003773428190000026
When the time-dependent function is adopted, the boundary is a non-constant heat flow boundary; the third type of boundary condition is used for describing the heat exchange between the system and the outside, k is the heat conduction coefficient, epsilon is the surface emissivity, sigma is the Stefan-Boltzmann constant, T amb Is ambient temperature.
Specifically, the formula describing the amount of thermal deformation by thermal expansion is as follows:
ε＝αT(T-T ref )
where ε is the thermal deformation, α is the thermal expansion secant coefficient, which is related to the material to be processed, T is the input temperature, which is derived from finite element temperature field simulation, T ref Is the process ambient temperature.
The invention has the beneficial effects that:
(1) And establishing a laser heat source model according to the Gauss law, and establishing a thermal deformation theoretical model according to the Fourier law. Secondly, establishing a visual finite element simulation model, verifying the rationality of the finite element model by using technical parameters recommended by a manufacturer, simulating to generate a discretized real-time processing data set, and then optimizing the processing parameters by using the finite element data set which accords with the actual processing as a training data set of a machine learning algorithm. Virtual and real information transmission is driven through a digital twinning technology, a hybrid model of model driving and data driving is constructed to perform high-approximation simulation and real-time compensation of cutting speed, thermal deformation of a cutting joint is reduced, thermal errors are reasonably avoided, and laser cutting precision is improved.
(2) By means of the visual characteristics of the finite element model, an operator can observe the cutting progress in real time, the rejection rate is reduced, and the working efficiency is improved.
(3) In the working process of the laser cutting machine, the cutting speed has time-varying property, particularly in the initial and end stages, and a full-period speed optimization strategy is established by means of the mapping capacity of a digital twinning technology on the time-varying property.
(4) The visualized thermal deformation digital model is generated, so that an operator can observe the cutting progress in real time and can monitor the thermal deformation condition in real time.
Drawings
Fig. 1 is a structural diagram of a laser cutting thermal error compensation method based on digital twinning according to the present invention.
FIG. 2 is a heat source model.
Fig. 3 is a simulated cloud of thermal deformation at a certain moment at the cutting seam.
Detailed Description
As shown in fig. 1, a method for compensating a thermal error of laser cutting based on digital twinning is characterized by comprising the following steps:
s1, establishing a laser heat source model; the heat source has the maximum flow at the intersection point and decreases towards the periphery based on a Gaussian model;
specifically, the heat source model is as follows:
as shown in fig. 2, the laser cutting device has a complex structure, and is not in contact with the workpiece except for the bracket for fixing the workpiece during the processing, so that the simulation result is not greatly influenced. Therefore, the mechanical part is reasonably simplified into a laser heat source. The laser is not a uniform heat source and the heat flux density is expressed as
Figure BDA0003773428190000041
Figure BDA0003773428190000042
In the formula q m The maximum heat flow of the heat source center, P is the total power of the heat source, and K is the heat source concentration coefficient. The heat flow density at any point (x, y) is related to its distance from the central maximum heat source point, i.e. the closer to the central point the greater the heat flow density, and the rate at which the heat flow density increases is related to the heat source concentration coefficient.
S2, establishing a thermal deformation theoretical model; setting boundary conditions of deformation through three basic modes of heat conduction, heat convection and heat radiation, and describing thermal deformation through thermal expansion according to the boundary conditions;
the boundary conditions for deformation are set by three basic ways of heat conduction, heat convection and heat radiation as follows:
Figure BDA0003773428190000051
the first kind of boundary conditions is used to describe the temperature distribution on the system boundary, where Γ is the boundary range, T is the temperature, and T is the time. Wherein T- Γ1 Constant, it is a steady state condition, and when T (Γ, T) is expressed as a function of time, it is an unsteady state heat source. The second class of boundary conditions describes whether heat flows in or out of the boundary, q s Is heat flux density of, wherein
Figure BDA0003773428190000055
Is the normal direction outside the system boundary. When in use
Figure BDA0003773428190000052
When the temperature of the water is higher than the set temperature,is an adiabatic boundary; when the temperature is higher than the set temperature
Figure BDA0003773428190000053
When the current is constant, the current is a constant heat current boundary; when in use
Figure BDA0003773428190000054
As a function of time, a non-constant thermal current boundary. In the cutting process, the laser heat source moves along a cutting track according to the cutting speed, changes along time and is an unsteady non-constant heat flow boundary. The third type of boundary condition is used for describing the heat exchange between the system and the outside, k is the heat conduction coefficient, epsilon is the surface emissivity, sigma is the Stefan-Boltzmann constant, T amb Is ambient temperature.
The thermal deformation is described by the boundary conditions through thermal expansion as follows:
in the laser cutting process, a heat source moves at a high speed, the part of a cutting seam is heated, severe expansion occurs at the moment of heating, and deformation also occurs simultaneously. The elastic deformation caused by thermal expansion is generated at the cutting seams, the duration is short, and the heat source is gradually recovered after passing through. When the thermal stress of the heated region exceeds the material yield limit, however, plastic deformation occurs, and this partial deformation has a great influence on the processing accuracy.
ε＝αT(T-T ref )
Where ε is the thermal deformation, α is the thermal expansion secant coefficient, which is related to the material to be processed, T is the input temperature, which is derived from finite element temperature field simulation, T ref Is the process ambient temperature.
S3, establishing a finite element model; establishing a model according to boundary conditions of the finite element model and parameters of the workpiece, verifying the rationality of the finite element model by using factory recommended parameters, and generating a discretized real-time processing data set when the judgment is reasonable;
s4, predicting the thermal deformation in the cutting process by taking a limited metadata set which accords with actual processing as a training data set of a machine learning algorithm to generate a thermal deformation prediction cloud picture shown in figure 3;
s5, cutting; and driving virtual and real information transmission through a digital twinning technology, compensating the cutting speed in real time according to the cutting thermal deformation amount to generate a visual thermal deformation digital model, and generating a compensated thermal deformation cloud picture.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims (5)

1. A laser cutting thermal error compensation method based on digital twinning is characterized by comprising the following steps:
s1, establishing a laser heat source model;
s2, establishing a thermal deformation theoretical model; setting boundary conditions of deformation through three basic modes of heat conduction, heat convection and heat radiation, and describing thermal deformation through thermal expansion according to the boundary conditions;
s3, establishing a finite element model; establishing a model according to boundary conditions of the finite element model and parameters of the workpiece, verifying the rationality of the finite element model by using factory recommended parameters, and generating a discretized real-time processing data set when the judgment is reasonable;
s4, predicting thermal deformation in the cutting process by taking the discrete real-time processing data set as a training data set of a machine learning algorithm to generate a thermal deformation prediction cloud picture;
s5, cutting; and driving virtual and real information transmission through a digital twinning technology, and compensating the cutting speed in real time according to the size of the cutting thermal deformation.
2. The digital twinning-based laser cutting thermal error compensation method as claimed in claim 1, wherein step S5 further generates a visualized thermo-deformation digital model.
3. The method for compensating the laser cutting thermal error based on the digital twinning as claimed in claim 1, wherein the heat source model in the step S1 is as follows:
the heat flux density formula of the laser heat source is
Figure FDA0003773428180000011
Figure FDA0003773428180000012
In the formula q m The maximum heat flow of the heat source center, P is the total power of the heat source, K is the heat source concentration coefficient, and (X, Y) is the distance between a point (X, Y) and the maximum heat source point in the X direction and the Y direction.
4. The method for compensating the thermal error of the laser cutting based on the digital twinning as claimed in claim 1, wherein the boundary conditions of the deformation are set by three basic modes of heat conduction, heat convection and heat radiation as follows:
Figure FDA0003773428180000021
the first type of boundary condition is used for describing temperature distribution on the system boundary, gamma is a boundary range, T is temperature, and T is time; wherein T is Γ1 Constant, is a steady state condition, and when T (Γ, T) is expressed as a function of time, is an unsteady state heat source; the second type of boundary condition describes whether there is heat flowing into or out of the boundary, q s Is heat flow density, wherein
Figure FDA0003773428180000022
Is the direction of the normal outside the system boundary; when the temperature is higher than the set temperature
Figure FDA0003773428180000023
Then, it is an adiabatic boundary; when in use
Figure FDA0003773428180000024
When it is constant, it is constantA heat flow boundary; when in use
Figure FDA0003773428180000025
When the time-dependent function is adopted, the boundary is a non-constant heat flow boundary; the third class of boundary conditions is used to describe the heat exchange between the system and the outside world, k is the heat transfer coefficient, ε is the surface emissivity, σ is the Stefan-Boltzmann constant, T amb Is ambient temperature.
5. The digital twin-based laser cutting thermal error compensation method as claimed in claim 1, wherein the formula describing the amount of thermal deformation through thermal expansion is as follows:
ε＝αT(T-T ref )
wherein ε is the amount of thermal deformation, α is the coefficient of secant thermal expansion, which is related to the material being processed, T is the input temperature, which is derived from finite element temperature field simulation, T ref Is the process ambient temperature.
CN202210908952.8A 2022-07-29 2022-07-29 Laser cutting thermal error compensation method based on digital twinning Pending CN115329631A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116493777A (en) * 2023-05-12 2023-07-28 济南奥镭数控设备有限公司 Numerical control cutting machine remote control system based on intelligent operation

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116493777A (en) * 2023-05-12 2023-07-28 济南奥镭数控设备有限公司 Numerical control cutting machine remote control system based on intelligent operation
CN116493777B (en) * 2023-05-12 2024-03-29 济南奥镭数控设备有限公司 Numerical control cutting machine remote control system based on intelligent operation

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