A process parameter configuration method for laser-assisted machining

Abstract

The present application relates to a kind of process parameter configuration methods for laser-assisted machining, specifically comprising the following steps: S1: establishing the three-dimensional transient workpiece temperature model of laser-assisted machining process;S2: with workpiece machining surface quality as constraint, establish the temperature boundary condition of machined surface, determine the selection threshold of laser power;S3: with the preheating temperature of material to be removed and the working temperature of tool as constraint, establish the temperature boundary condition of cutting contact area, determine the selectable interval of laser-tool offset distance;S4: the mapping relationship of the boundary of laser-tool offset distance selectable interval and laser power is fitted, and the selection atlas of laser power and laser-tool offset distance is constructed;S5: based on the selection atlas constructed in S4, the process parameters of laser-assisted machining are configured.The present application provides a quick and reliable process parameter configuration method for laser-assisted machining, not only ensures the machined surface quality, but also avoids the thermal fatigue damage of tool, which helps to improve machining efficiency.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of laser-assisted machining, and more particularly relates to a process parameter configuration method for laser-assisted machining. BACKGROUND

[0002] With the rapid development of aircraft carriers and aviation industry in China, advanced materials such as composite materials, ultra-high strength steel and high-temperature alloy are widely used. However, the above-mentioned materials have poor machinability, and there are bottleneck problems such as low machining efficiency and difficult control of surface quality in traditional machining. Laser-assisted machining is a kind of hybrid machining technology, which opens up a new way for efficient machining of difficult-to-machine materials. The principle is to use the thermal effect of high-energy beam to soften the material to be removed, thereby improving its cutting performance. Laser-assisted machining not only improves the machining efficiency, but also helps to improve the machining surface quality and prolong the tool life, and has broad application prospects.

[0003] The process parameter configuration of laser-assisted machining has a significant impact on its machining efficiency and surface quality. Selecting appropriate laser power and laser-tool offset distance is the key to the process parameter configuration of laser-assisted machining. If the laser power is too large, it is easy to deteriorate the machined surface quality. If the laser power is too small or the laser-tool offset distance is too large, the material to be removed is not softened enough, which affects the machining efficiency. In addition, too small laser-tool offset distance can easily cause thermal fatigue damage to the tool.

[0004] Currently, the process parameters of laser-assisted machining are usually configured by trial cutting method, which needs to carry out cutting test and machining surface quality test, and has the problems of low efficiency and high cost. It is necessary to propose a more simple, efficient and low-cost process parameter configuration method. SUMMARY

[0005] In view of the deficiencies and improvement needs of the prior art, the present application provides a process parameter configuration method for laser-assisted machining. The purpose is to construct a selection map of laser power and laser-tool offset distance, and realize rapid and reliable process parameter configuration.

[0006] The present application realizes the above-mentioned purpose through the following technical solutions:

[0007] A process parameter configuration method for laser-assisted machining, specifically comprising the following steps:

[0008] S1: establishing a three-dimensional transient workpiece temperature model of the laser-assisted machining process;

[0009] S2: based on the three-dimensional transient workpiece temperature model established in step S1, establishing a machined surface temperature boundary condition with the workpiece machining surface quality as the constraint, and determining the selection threshold of the laser power;

[0010] S3: on the basis of steps S1 and S2, establishing a cutting contact area temperature boundary condition with the preheating temperature of the material to be removed and the tool working temperature as constraints, and determining a selectable interval of the laser-tool offset distance;

[0011] S4: repeating step S3 for each laser power, fitting a mapping relationship between the boundary of the laser-tool offset distance selectable interval and the laser power, and constructing a selection atlas of the laser power and the laser-tool offset distance;

[0012] S5: configuring the process parameters of the laser-assisted machining based on the selection atlas constructed in S4.

[0013] As a further optimization scheme of the present application, S1 establishes a three-dimensional transient workpiece temperature model of the laser-assisted machining process, and solves it by using the finite difference method. The heat conduction equation of the laser-assisted machining process is expressed as follows:

[0014]

[0015] Wherein, T is the temperature of the workpiece, t is the time, q is the heat source intensity of the laser. ρ, c and k are the density, specific heat capacity and thermal conductivity of the workpiece material, respectively, and x, y and z are the coordinates of the internal points of the workpiece.

[0016] As a further optimization scheme of the present application, S2 establishes a machined surface temperature boundary condition with the machining surface quality as a constraint:

[0017] T m_p (x m ,y m ,z m )<T p

[0018] Wherein, T m_p is the peak temperature of the machined surface, T p is the microstructure transformation temperature of the workpiece material, x m , y m and z m are the coordinates of any point on the machined surface.

[0019] As a further optimization scheme of the present application, S3 establishes two cutting contact area temperature boundary conditions with the preheating temperature of the material to be removed and the tool working temperature as constraints, respectively. The two cutting contact area temperature boundary conditions are used to determine the upper boundary and the lower boundary of the laser-tool offset distance selectable interval.

[0020] As a further optimization scheme of the present application, the cutting contact area temperature boundary condition established in S3 with the preheating temperature of the material to be removed as a constraint is expressed as follows:

[0021] T c_ave(x c ,y c ,z c )≥T s

[0022] wherein T c_ave is the average preheating temperature of the material to be removed, T s is the critical temperature corresponding to the sharp reduction of the material strength, x c , y c and z c are the coordinates of any point in the contact area.

[0023] As a further optimization scheme of the present application, the temperature boundary condition of the contact area established in S3 with the tool working temperature as the constraint is expressed as follows:

[0024] T c_max (x c ,y c ,z c )≤T t

[0025] wherein T c_max is the highest preheating temperature of the material to be removed, and T t is the heat-resistant temperature of the tool.

[0026] As a further optimization scheme of the present application, the mapping relationship between the upper and lower boundaries of the selectable interval of the laser-tool offset and the laser power in S4 is fitted as follows:

[0027]

[0028]

[0029] wherein l l and l u are the lower and upper boundaries of the selectable interval of the laser-tool offset, P is the laser power, and c0, c1, c2, c3, c4 and c5 are constant coefficients.

[0030] As a further optimization scheme of the present application, S4 combines the boundary condition of the machined surface temperature, the boundary condition of the contact area temperature and the geometric constraint condition to construct the selection atlas of the laser power and the laser-tool offset, which is expressed as a function as follows:

[0031] max[l0,l l (P)]≤l(P)≤l u (P)

[0032] wherein l0 is the critical laser-tool offset corresponding to the non-interference of the laser beam and the tool, and l is the final selectable laser-tool offset.

[0033] The present application has the beneficial effects of:

[0034] The present application constructs a selection atlas of laser power and laser-tool offset distance, provides a quick and reliable process parameter configuration method for laser-assisted machining, ensures the machined surface quality, avoids the thermal fatigue damage of the tool, and helps to improve the machining efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A flow chart of the method of the present application is shown in Figure 1.

[0036] Figure 2 A schematic diagram of laser-assisted machining is shown in Figure 2.

[0037] Figure 3 A calculation result of temperature distribution in the cutting contact area is shown in Figure 3.

[0038] Figure 4 A boundary fitting curve of the laser-tool offset distance selectable interval is shown in Figure 4.

[0039] Figure 5 A selection atlas of laser power and laser-tool offset distance is shown in Figure 5. DETAILED DESCRIPTION

[0040] The present application will be further described in detail below with reference to the accompanying drawings. It is necessary to point out here that the following detailed description is only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above application content.

[0041] As shown in Figure 1, the present embodiment provides a process parameter configuration method for laser-assisted machining, which specifically comprises the following steps: Figure 1

[0042] (1) Establishing a three-dimensional transient workpiece temperature model of the laser-assisted machining process

[0043] In the laser-assisted machining process (taking milling machining as an example), the laser beam is irradiated in front of the tool and is synchronously fed with the tool, as shown in Figure 2. In order to simplify the model, the influence of the cutting heat source on the workpiece temperature is ignored. Therefore, the heat conduction equation of the laser-assisted machining process can be expressed as follows: Figure 2

[0044] In the formula, T is the temperature of the workpiece, t is the time, q is the heat source intensity of the laser. ρ, c and k are the density, specific heat capacity and thermal conductivity of the workpiece material, respectively. x, y and z are the coordinates of the internal points of the workpiece.

[0045]

[0046] ​​The finite difference method is used to solve the heat conduction equation to obtain the three-dimensional transient workpiece temperature distribution in the laser-assisted machining process.

[0047] (2) Establishing the machined surface temperature boundary condition

[0048] Based on the three-dimensional transient workpiece temperature model established in step (1), the machined surface temperature boundary condition is established with the constraint that the machined surface workpiece material does not undergo microstructure transformation:

[0049] T m_p (x m ,y m ,z m )<T p

[0050] In the formula, T m_p is the peak temperature of the machined surface, T p is the microstructure transformation temperature of the workpiece material. x m , y m and z m are the coordinates of any point on the machined surface.

[0051] According to the machined surface temperature boundary condition, the selection threshold of the laser power can be determined, which is about 952 W. To ensure the quality of the machined surface, the laser power should be selected to be less than the threshold.

[0052] (3) Establishing the temperature boundary condition of the cutting contact area

[0053] On the basis of steps (1) and (2), the temperature distribution of the cutting contact area is calculated. For easy visual display, it is transformed into the cylindrical coordinate system, and the result is shown in Figure 3 Two cutting contact area temperature boundary conditions are established with the constraints of the preheating temperature of the material to be removed and the tool working temperature, respectively. Among them, the cutting contact area temperature boundary condition established with the constraint of the preheating temperature of the material to be removed is expressed as follows:

[0054] T c_ave (x c ,y c ,z c )≥T s

[0055] In the formula, T c_ave is the average preheating temperature of the material to be removed, T s is the critical temperature corresponding to the sharp decrease of material strength. x c , y c and z c are the coordinates of any point in the cutting contact area.

[0056] The temperature boundary condition of the cutting contact area established by taking the tool working temperature as a constraint is expressed as follows:

[0057] T c_max (x c ,y c ,z c )≤T t

[0058] In the formula, T c_max is the highest preheating temperature of the material to be removed, and T t is the heat-resistant temperature of the tool.

[0059] According to the above two temperature boundary conditions of the cutting contact area, the upper boundary and the lower boundary of the laser-tool offset selectable interval can be determined respectively.

[0060] (4) Fitting the mapping relationship between the boundaries of the laser-tool offset selectable interval and the laser power

[0061] Under the premise that the selected threshold of the laser power is not exceeded, the laser power is traversed, step (3) is repeated, and the laser-tool offset selectable interval under each laser power condition is obtained. According to the obtained laser power and the upper and lower boundary data of the laser-tool offset selectable interval, the mapping relationship between the upper and lower boundaries of the laser-tool offset selectable interval and the laser power is fitted respectively:

[0062]

[0063]

[0064] In the formula, l l and l u are the lower boundary and the upper boundary of the laser-tool offset selectable interval respectively, and P is the laser power. c0, c1, c2, c3, c4 and c5 are constant coefficients.

[0065] The fitting results of the constant coefficients c0, c1, c2, c3, c4 and c5 are -141.8, -0.328, 29.12, 0.07722, 0.8503 and 3.245 respectively. According to the fitted mapping relationship, the change of the boundaries of the laser-tool offset selectable interval with the laser power is shown in FIG. 1. Figure 4

[0066] (5) Constructing the selection atlas of the laser power and the laser-tool offset

[0067] ​In the laser-assisted machining process, the laser beam should not be directly irradiated on the tool. Therefore, the process parameter configuration of laser-assisted machining should meet the corresponding geometric constraint condition, that is, the laser-tool offset distance should be greater than its critical value. According to the geometric relationship of laser-assisted machining, the critical value is about 10 mm. Combined with the temperature boundary conditions of the machined surface and the cutting touch area, and the geometric constraint condition, the selection atlas of laser power and laser-tool offset distance is constructed, and the function expression is as follows:

[0068] max[l0, l l (P)]≤l(P)≤l u (P)

[0069] In the formula, l0 is the critical laser-tool offset distance corresponding to the laser beam and the tool without interference, and l is the final laser-tool offset distance that can be selected.

[0070] The final selection atlas of laser power and laser-tool offset distance is shown in FIG. 1. Figure 5 The figure shows the range of laser power and laser-tool offset distance that can be selected under the constraints of the machined surface temperature, the cutting touch area temperature and the geometric constraint condition.

[0071] (6) Configuration of process parameters of laser-assisted machining

[0072] According to the selection atlas constructed in step (5), the laser power and the laser-tool offset distance are determined, and combined with the cutting parameters recommended by the tool manufacturer, the process parameter configuration of laser-assisted machining is realized.

[0073] The above-described embodiments only express one embodiment of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of protection of the present application.

Claims

1. A method for configuring process parameters for laser-assisted processing, characterized in that: Specifically, the following steps are included: S1: Establish a three-dimensional transient workpiece temperature model for laser-assisted machining; S2: Based on the three-dimensional transient workpiece temperature model established by S1, the boundary conditions of the processed surface temperature are established with the workpiece surface quality as a constraint, and the selection threshold of laser power is determined. S3: Based on S1 and S2, the temperature boundary conditions of the cutting area are established with the preheating temperature of the material to be removed and the working temperature of the tool as constraints, and the selectable range of laser-tool offset is determined. S4: Iterate through each laser power, repeat S3, fit the mapping relationship between the boundary of the selectable range of laser-tool offset and laser power, and construct the selection spectrum of laser power and laser-tool offset; S5: Based on the selection map constructed in S4, configure the process parameters for laser-assisted processing; The temperature boundary conditions of the processed surface established in S2 are expressed as follows: T m_p (x m ,y m ,z m )<T p Among them, T m_p T represents the peak temperature of the machined surface. p x is the microstructure transformation temperature of the workpiece material. m y m and z m Let be the coordinates of any point on the machined surface; In S3, two temperature boundary conditions for the cutting contact area are established, with the preheating temperature of the material to be removed and the working temperature of the tool as constraints. The two temperature boundary conditions for the cutting contact area are used to determine the upper and lower boundaries of the selectable range of laser-tool offset.

2. The method for configuring process parameters for laser-assisted processing according to claim 1, characterized in that: In step S1, a three-dimensional transient workpiece temperature model for the laser-assisted machining process is established and solved using the finite difference method. The heat conduction equation for the laser-assisted machining process is expressed as follows: Where T is the temperature of the workpiece, t is the time, q is the heat source intensity of the laser, ρ, c and k are the density, specific heat capacity and thermal conductivity of the workpiece material, respectively, and x, y and z are the coordinates of points inside the workpiece.

3. The method for configuring process parameters for laser-assisted processing according to claim 1, characterized in that: The temperature boundary condition of the contact region established in S3 with the preheating temperature of the material to be removed as a constraint is expressed as follows: T c_ave (x c ,y c ,z c )≥T s Among them, T c_ave T represents the average preheating temperature of the material to be removed. s x is the critical temperature at which the strength of a material decreases sharply. c y c and z c Let be the coordinates of any point within the contact area.

4. The method for configuring process parameters for laser-assisted processing according to claim 3, characterized in that: The temperature boundary condition of the contact region established in S3 with the tool operating temperature as a constraint is expressed as follows: T c_max (x c ,y c ,z c )≤T t Among them, T c_max T is the highest preheating temperature of the material to be removed. t This refers to the heat resistance temperature of the cutting tool.

5. The method for configuring process parameters for laser-assisted processing according to claim 4, characterized in that: The mapping relationship between the upper and lower boundaries of the selectable laser-tool offset range in S4 and the laser power is expressed as follows: Among them, l l and l u These represent the lower and upper boundaries of the selectable range of laser-tool offset, respectively. P is the laser power, and c0, c1, c2, c3, c4, and c5 are constant coefficients.

6. The method for configuring process parameters for laser-assisted processing according to claim 5, characterized in that: In step S4, the selection spectrum of laser power versus laser-tool offset is constructed by combining the temperature boundary conditions of the processed surface, the temperature boundary conditions of the cutting area, and the geometric constraints. The function is expressed as follows: max[l0,l l (P)]≤l(P)≤l u (P) Where l0 is the critical laser-tool offset at which the laser beam and the tool do not interfere, and l is the final selectable laser-tool offset.

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