CN115647625A - Technological parameter configuration method for laser-assisted machining - Google Patents

Abstract

The invention relates to a technological parameter configuration method for laser-assisted machining, which specifically comprises the following steps: s1: establishing a three-dimensional transient workpiece temperature model in a laser-assisted machining process; s2: establishing a temperature boundary condition of a processed surface by taking the quality of the processed surface of the workpiece as a constraint, and determining a selection threshold of laser power; s3: establishing a temperature boundary condition of a contact area by taking the preheating temperature of the material to be removed and the working temperature of the cutter as constraints, and determining a selectable interval of the laser-cutter offset distance; s4: fitting the mapping relation between the boundary of the laser-cutter offset distance selectable interval and the laser power, and constructing a selection map of the laser power and the laser-cutter offset distance; s5: and configuring the technological parameters of the laser-assisted machining based on the selection map constructed in the S4. The invention provides a rapid and reliable technological parameter configuration method for laser-assisted machining, which not only ensures the quality of the machined surface, but also avoids the thermal fatigue damage of the cutter, and is beneficial to improving the machining efficiency.

Description

A process parameter configuration method for laser-assisted processing

technical field

The invention belongs to the field of laser-assisted processing, and more specifically relates to a process parameter configuration method for laser-assisted processing.

Background technique

With the rapid development of my country's aircraft carrier and aviation industry, advanced materials such as composite materials, ultra-high-strength steel, and high-temperature alloys are widely used. However, the machinability of the above-mentioned materials is poor, and there are bottleneck problems such as low processing efficiency and difficult control of surface quality in traditional processing. Laser-assisted machining is a hybrid machining technique that opens up a new avenue for efficient machining of difficult-to-machine materials. The principle is to use the thermal effect of the high-energy beam to soften the material to be removed by heating, thereby improving its cutting performance. Laser-assisted processing can not only improve the processing efficiency, but also help to improve the quality of the processed surface and prolong the life of the tool, so it has broad application prospects.

The process parameter configuration of laser-assisted processing has a significant impact on its processing efficiency and surface quality. Selecting the appropriate laser power and laser-tool offset is the key to the configuration of laser-assisted machining process parameters. If the laser power is selected too large, it is easy to deteriorate the quality of the processed surface. If the laser power is too small or the laser-tool offset is too large, the material to be removed will not be softened enough, which will affect the processing efficiency. In addition, choosing too small laser-tool offset is likely to cause thermal fatigue damage of the tool.

At present, the method of trial cutting is usually used to configure the process parameters of laser-assisted processing, and it is necessary to carry out cutting tests and machined surface quality testing tests, which have prominent problems such as low efficiency and high cost. It is necessary to propose a more simple, efficient and low-cost process parameter configuration method.

Contents of the invention

Aiming at the deficiencies and improvement needs of the prior art, the present invention provides a process parameter configuration method for laser-assisted processing. Its purpose is to construct a selection map of laser power and laser-tool offset distance to realize fast and reliable configuration of process parameters.

The present invention achieves the above object through the following technical solutions:

A process parameter configuration method for laser-assisted processing, specifically comprising the following steps:

S1: Establish a three-dimensional transient workpiece temperature model for laser-assisted processing;

S2: Based on the three-dimensional transient workpiece temperature model established in step S1, and taking the processed surface quality of the workpiece as a constraint, establish the boundary condition of the processed surface temperature, and determine the selection threshold of the laser power;

S3: On the basis of steps S1 and S2, with the preheating temperature of the material to be removed and the working temperature of the tool as constraints, establish the temperature boundary condition of the contact area, and determine the optional interval of the laser-tool offset distance;

S4: Traverse each laser power, repeat step S3, fit the mapping relationship between the boundary of the optional range of laser-tool offset distance and laser power, and construct a selection map of laser power and laser-tool offset distance;

S5: Based on the selection map constructed in S4, configure the process parameters of the laser-assisted processing.

As a further optimization solution of the present invention, the S1 establishes a three-dimensional transient workpiece temperature model in the laser-assisted machining process, and uses the finite difference method to solve it. The heat conduction equation of the laser-assisted machining process is expressed as follows:

Among them, T is the temperature of the workpiece, t is the time, and 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.

As a further optimization scheme of the present invention, the S2 is constrained by the quality of the processed surface, and the temperature boundary condition of the processed surface is established:

T _{m_p} (x _m ,y _m ,z _m )＜T _p

Among them, T _{m_p} is the peak temperature of the machined surface, T _p is the microstructure transition temperature of the workpiece material, x _m , y _m and z _m are the coordinates of any point on the machined surface.

As a further optimization solution of the present invention, the S3 is constrained by the preheating temperature of the material to be removed and the working temperature of the tool respectively, and establishes two temperature boundary conditions of the contact area. Two temperature boundary conditions in the contact area are used to determine the upper boundary and lower boundary of the optional range of laser-tool offset distance respectively.

As a further optimization scheme of the present invention, the temperature boundary condition of the tangential contact area 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

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 in material strength, x _c , y _c and z _c are the coordinates of any point in the contact area.

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

T _{c_max} (x _c ,y _c ,z _c )≤T _t

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.

As a further optimization scheme of the present invention, the mapping relationship between the upper and lower boundaries of the optional interval of the fitted laser-tool offset in S4 and the laser power:

Among them, l _l and l _u are the lower boundary and upper boundary of the optional laser-tool offset range respectively, P is the laser power, and c ₀ , c ₁ , c ₂ , c ₃ , c ₄ and c ₅ are constant coefficients.

As a further optimization scheme of the present invention, the S4 combines the processed surface temperature boundary conditions, the contact area temperature boundary conditions and geometric constraints to construct a selection map of laser power and laser-tool offset distance, and the function expression is as follows:

max[l ₀ ,l _l (P)]≤l(P)≤l _u (P)

In the formula, l ₀ is the critical laser-tool offset corresponding to no interference between the laser beam and the tool, and l is the final alternative laser-tool offset.

The beneficial effects of the present invention are:

The invention builds a selection map of laser power and laser-tool offset distance, provides a fast and reliable process parameter configuration method for laser-assisted processing, not only ensures the quality of the processed surface, but also avoids thermal fatigue damage of the tool, which is helpful To improve processing efficiency.

Description of drawings

Fig. 1 is a method block diagram of the present invention;

Figure 2 is a schematic diagram of laser-assisted processing;

Figure 3 is the calculation result of the temperature distribution in the contact area;

Fig. 4 is the boundary fitting curve of the optional interval of laser-tool offset;

Figure 5 is the selection map of laser power and laser-tool offset distance.

Detailed ways

The application will be described in further detail below in conjunction with the accompanying drawings. It is necessary to point out that the following specific embodiments are only used to further illustrate the application, and cannot be interpreted as limiting the protection scope of the application. The above application content makes some non-essential improvements and adjustments to this application.

As shown in Figure 1, this embodiment provides a method for configuring process parameters for laser-assisted processing, which specifically includes the following steps:

(1) Establish a three-dimensional transient workpiece temperature model for laser-assisted processing

During laser-assisted machining (taking milling as an example), the laser beam is irradiated in front of the tool and fed synchronously with it, as shown in Figure 2. 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:

In the formula, T is the temperature of the workpiece, t is the time, and 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 points inside the workpiece.

Using the finite difference method to solve the above heat conduction equation, the three-dimensional transient workpiece temperature distribution of the laser-assisted machining process can be obtained.

(2) Establish the temperature boundary condition of the processed surface

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

T _{m_p} (x _m ,y _m ,z _m )＜T _p

In the formula, T _{m_p} is the peak temperature of the machined surface, and T _p is the microstructure transition temperature of the workpiece material. x _m , y _m and z _m are the coordinates of any point on the machined surface.

According to the boundary conditions of the processed surface temperature, the selection threshold of laser power can be determined, which is about 952W. In order to ensure the quality of the processed surface, the laser power should be selected less than this threshold.

(3) Establish temperature boundary conditions in the contact area

On the basis of steps (1) and (2), calculate the temperature distribution in the contact area. For the convenience of intuitive display, it is transformed into a cylindrical coordinate system, and the result is shown in Figure 3. Taking the preheating temperature of the material to be removed and the working temperature of the tool as constraints respectively, two temperature boundary conditions of the contact area are established. Among them, the temperature boundary condition of the contact area established 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

In the formula, _{Tc_ave} is the average preheating temperature of the material to be removed, and _Ts is the critical temperature corresponding to the sharp decrease in material strength. x _c , y _c and z _c are the coordinates of any point within the tangent area.

The temperature boundary condition of the contact area established with the working temperature of the tool as a constraint is expressed as follows:

T _{c_max} (x _c ,y _c ,z _c )≤T _t

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.

According to the above two temperature boundary conditions of the contact area, the upper boundary and lower boundary of the optional interval of laser-tool offset distance can be determined respectively.

(4) Fitting the mapping relationship between the boundary of the optional range of laser-tool offset and laser power

On the premise that the selection threshold of the laser power is not exceeded, each laser power is traversed, and step (3) is repeated to obtain the optional range of the laser-tool offset distance under each laser power condition. According to the obtained laser power and the upper and lower boundary data of the laser-tool offset optional interval, respectively fit the mapping relationship between the upper and lower boundaries of the laser-tool offset optional interval and the laser power:

In the formula, l _l and l _u are the lower boundary and upper boundary of the optional range of laser-tool offset, respectively, and P is the laser power. c ₀ , c ₁ , c ₂ , c ₃ , c ₄ and c ₅ are constant coefficients.

The fitting results of constant coefficients c ₀ , c ₁ , c ₂ , c ₃ , c ₄ and c ₅ are -141.8, -0.328, 29.12, 0.07722, 0.8503 and 3.245, respectively. According to the fitted mapping relationship, the boundary of the optional interval of the laser-tool offset distance varies with the laser power as shown in Figure 4.

(5) Construct the selection map of laser power and laser-tool offset distance

During laser-assisted machining, direct irradiation of the laser beam on the tool should be avoided. Therefore, the process parameter configuration of laser-assisted processing should meet the corresponding geometric constraints, that is, the laser-tool offset distance should be greater than its critical value. According to the geometry of laser-assisted processing, the critical value is about 10mm. Combining the temperature boundary conditions of the processed surface, the temperature boundary conditions of the contact area and the geometric constraints, the selection map of laser power and laser-tool offset distance is constructed. The function expression is as follows:

max[l ₀ ,l _l (P)]≤l(P)≤l _u (P)

In the formula, l ₀ is the critical laser-tool offset corresponding to no interference between the laser beam and the tool, and l is the final alternative laser-tool offset.

The finally obtained selection map of laser power and laser-tool offset distance is shown in Fig. 5. The figure shows the range of laser power and laser-tool offset distance that can be selected under the temperature constraints of the processed surface, the temperature constraints of the contact area and the geometric constraints.

(6) Configure the process parameters of laser-assisted processing

Determine the laser power and laser-tool offset according to the selection map constructed in step (5), and combine the cutting parameters recommended by the tool manufacturer to realize the process parameter configuration of laser-assisted processing.

The above-mentioned embodiment only expresses one implementation mode of the present invention, and its description is relatively specific and detailed, but it should not be understood as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims (8)

1. A technological parameter configuration method for laser-assisted machining is characterized by comprising the following steps: the method specifically comprises the following steps:

s1: establishing a three-dimensional transient workpiece temperature model in a laser-assisted machining process;

s2: based on the three-dimensional transient workpiece temperature model established in the S1, establishing a machined surface temperature boundary condition by taking the quality of a machined surface of the workpiece as a constraint, and determining a selection threshold of laser power;

s3: on the basis of S1 and S2, establishing a temperature boundary condition of a contact cutting area by taking the preheating temperature of the material to be removed and the working temperature of the cutter as constraints, and determining a selectable interval of laser-cutter offset distance;

s4: traversing each laser power, repeating S3, fitting the mapping relation between the boundary of the laser-cutter offset distance selectable interval and the laser power, and constructing a selection map of the laser power and the laser-cutter offset distance;

s5: and configuring the technological parameters of the laser-assisted machining based on the selection map constructed in the S4.

2. The method for configuring the process parameters for laser-assisted machining according to claim 1, wherein: in the step S1, a three-dimensional transient workpiece temperature model of the laser-assisted machining process is established and solved by adopting a finite difference method, and a heat conduction equation of the laser-assisted machining process is expressed as follows:

wherein T is the temperature of the workpiece, T is 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.

3. The method for configuring process parameters for laser-assisted machining according to claim 1, characterized in that: the machined surface temperature boundary conditions established in S2 are expressed as follows:

T _{m_p} (x _m ,y _m ,z _m )＜T _p

wherein, T _{m_p} Is the peak temperature, T, of the machined surface _p Is the microstructure transition temperature, x, of the workpiece material _m 、y _m And z _m Coordinates of any point on the machined surface.

4. The method for configuring process parameters for laser-assisted machining according to claim 3, characterized in that: and in the step S3, two temperature boundary conditions of the contact area are established by respectively taking the preheating temperature of the material to be removed and the working temperature of the cutter as constraints, and are respectively used for determining the upper boundary and the lower boundary of the laser-cutter offset distance selectable interval.

5. The method for configuring process parameters for laser-assisted machining according to claim 4, wherein: the temperature boundary condition of the contact cutting area established by taking the preheating temperature of the material to be removed as the constraint in the step S3 is represented as follows:

T _{c_ave} (x _c ,y _c ,z _c )≥T _s

wherein, T _{c_ave} Is the average preheating temperature, T, of the material to be removed _s For a sharp decrease in the strength of the material, corresponding to the critical temperature, x _c ，y _c And z _c The coordinates of any point in the contact area.

6. The method for configuring process parameters for laser-assisted machining according to claim 5, wherein: the temperature boundary condition of the contact area established by taking the working temperature of the cutter as the constraint in the step S3 is expressed as follows:

T _{c_max} (x _c ,y _c ,z _c )≤T _t

wherein, T _{c_max} Is the maximum preheating temperature, T, of the material to be removed _t The temperature resistance of the cutter is shown.

7. The method for configuring process parameters for laser-assisted machining according to claim 6, wherein: the mapping relation between the upper and lower boundaries of the laser-tool offset distance selectable interval and the laser power in the step S4 is represented as follows:

wherein l _l And l _u Respectively the lower boundary and the upper boundary of the laser-cutter offset distance selectable interval, P is the laser power, c ₀ 、c ₁ 、c ₂ 、c ₃ 、c ₄ And c ₅ Is a constant coefficient.

8. The method for configuring process parameters for laser-assisted machining according to claim 7, wherein: and in the step S4, a selection map of the laser power and the laser-cutter offset distance is constructed by combining the temperature boundary condition of the processed surface, the temperature boundary condition of the contact area and the geometric constraint condition, and the function expression is as follows:

max[l ₀ ,l _l (P)]≤l(P)≤l _u (P)

wherein l ₀ The critical laser-tool offset distance corresponding to the condition that the laser beam and the tool do not interfere with each other, and l is the final optional laser-tool offset distance.

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