Laser cutting control method and system for CNC machine tools

Abstract

The present application relates to the field of laser cutting technology, and in particular to a laser cutting control method and system for CNC machine tools, the method comprising: determining the cutting difficulty of each position point in the material to be cut according to the correlation between material characteristics and cutting quality; selecting multiple cutting points, constructing an objective function according to the weight of each cutting point, taking each cutting point when the objective function takes the minimum value as the first path, and the weight is positively correlated with the curvature of the cutting point; obtaining the heat-affected area and heat-affected degree of each cutting point; calculating the cutting margin according to the heat-affected degree of the heat-affected area where the cutting point is located; adjusting the cutting point according to the cutting margin to obtain the second path, and performing laser cutting according to the second path. The technical solution of the present application can improve the accuracy of laser cutting.

Description

Technical Field

[0001] The present application relates to the field of laser cutting technology, and in particular to a laser cutting control method and system for a CNC machine tool. Background Art

[0002] Laser cutting is a non-contact processing method that uses a laser cutting head to focus the laser on the surface of the material for thermal processing to complete the cutting of the material. With the development of laser cutting technology, laser cutting can be used to cut more and more materials and achieve good cutting results.

[0003] At present, a patent application document with publication number CN116944700A discloses a detection and control method and system for laser cutting, the method comprising: obtaining parameter data of a material to be cut; extracting cutting material characteristic data and cutting requirement data from the parameter data of the material to be cut, and obtaining cutting material characteristic data and cutting requirement data; generating laser cutting parameters for the cutting material characteristic data according to the cutting requirement data, thereby obtaining laser cutting parameter data; constructing a simulation model for the parameter data of the material to be cut, obtaining a simulation model of the material to be cut, and selecting the minimum loss cutting point for the simulation model of the material to be cut according to the cutting requirement data, and obtaining cutting point selection data; performing laser cutting operations according to the laser cutting parameter data and the cutting point selection data.

[0004] The above method extracts key cutting material characteristic data and cutting requirement data from the parameter data of the material to be cut. Although it can adapt the cutting process to the characteristics of different materials, the above method ignores the influence of laser heat on the material to be cut during the cutting process, resulting in differences between the cut shape and the target shape, and the laser cutting accuracy is low. Summary of the invention

[0005] In order to solve the technical problem of low precision of laser cutting of CNC machine tools, the present application provides a laser cutting control method and system for CNC machine tools, which can improve the precision of laser cutting.

[0006] In a first aspect of the present application, a laser cutting control method for a CNC machine tool is provided, the control method comprising: determining the cutting difficulty of each position point in the material to be cut according to the correlation between the material characteristics and the cutting quality, the material characteristics including thickness, hardness and surface quality; selecting multiple cutting points, constructing an objective function according to the weight of each cutting point, taking each cutting point when the objective function takes the minimum value as the first path, the weight is positively correlated with the curvature of the cutting point, and the objective function for:

[0007] ; is the Hu moment of the target shape, is the Hu moment of the cutting area surrounded by the cutting points, is the surface quality in the cutting area, is the number of cutting points, Cut point The weight of Cut point The number of cutting points is the same as the number of contour points of the target shape; the heat affected area and the degree of heat influence of each cutting point are obtained; the cutting margin is calculated according to the degree of heat influence of the heat affected area where the cutting point is located; the cutting point is adjusted according to the cutting margin to obtain a second path, and laser cutting is performed according to the second path; the cutting point Cutting allowance for:

[0008] ; is the initial margin, To include the cutting point The total heat affected area, Heat affected area Middle cutting point Distance to the regional center, Heat affected area The degree of thermal influence, is a Gaussian function.

[0009] Firstly, the cutting difficulty of each position point in the material to be cut is calculated according to the correlation between material characteristics and cutting quality. The greater the cutting difficulty, the worse the cutting quality of the position point after cutting. Multiple cutting points are selected in the material to be cut, and the number of cutting points is the same as the number of contour points in the target shape. The closed area surrounded by multiple cutting points is the cutting area. The objective function is constructed by comprehensively considering the shape consistency, internal surface quality and cutting difficulty of the cutting area to measure the cutting effect of multiple cutting points. Each cutting point when the objective function takes the minimum value is taken as the first path. Furthermore, considering the influence of laser heat on the cutting area during laser cutting, the heat-affected area and the degree of heat influence of each cutting point are calculated. The heat-affected area and the degree of heat influence are related to the laser power and the dwelling time of the cutting point. The cutting margin is calculated according to the degree of heat influence of multiple heat-affected areas where the cutting point is located. The cutting points in the first path are adjusted according to the cutting margin to obtain the second path. The second path can eliminate the influence of the heat generated by the laser at each cutting point on the material to be cut, avoid deformation of the shape of the cutting area due to heat, and improve the accuracy of laser cutting.

[0010] Preferably, the method for obtaining the correlation between material characteristics and cutting quality includes: collecting arbitrary material characteristics and cutting quality at multiple position points in the historical cutting process to obtain a material characteristic sequence and cutting quality; and using the Pearson correlation coefficient between the material characteristic sequence and the cutting quality as the correlation between the material characteristics and the cutting quality.

[0011] The correlation between each material feature and the cutting quality is obtained according to the material feature sequence and cutting quality in the historical cutting process. When the correlation value is greater than 0, it means that the cutting quality increases with the increase of the material feature; when the correlation value is less than 0, it means that the cutting quality decreases with the increase of the material feature. This can accurately quantify the influence of each material feature on the cutting quality.

[0012] Preferably, the location point Difficulty of cutting for: , is the number of material characteristics, Material characteristics Relevance of cutting quality, For location point Material characteristics The value of .

[0013] For material features In terms of The larger the value, the better the material characteristics. You can click on the location Get better cutting quality, position point The cutting difficulty is relatively small, so The opposite number of The obtained location point The cutting difficulty of each position can be accurately determined by combining all material characteristics. The greater the cutting difficulty, the worse the cutting quality at the corresponding position.

[0014] Preferably, the method of obtaining the heat affected zone and degree of heat influence of each cutting point includes: determining the laser power and dwell time of the cutting point according to the thickness and hardness in the material characteristics; the heat affected zone is a circular area with the cutting point as the center and a radius of a preset radius; the degree of heat influence is the product of the laser power and the dwell time.

[0015] Preferably, the cutting point Preset radius for: ; is the initial radius, The length of stay.

[0016] For any cutting point, the longer the dwell time at the cutting point is, the farther the heat diffuses. Therefore, the preset radius should be increased to expand the heat-affected zone of the cutting point and improve the accuracy of subsequent cutting allowances.

[0017] Preferably, adjusting the cutting point according to the cutting allowance includes: obtaining the tangent direction of any cutting point, and taking the direction perpendicular to the tangent direction and pointing to the outside of the cutting area as the target direction of each cutting point; translating each cutting point along the direction corresponding to the target direction by the distance of the cutting allowance to obtain a second path.

[0018] The larger the cutting allowance, the greater the distance the cutting point is moved to eliminate the heat generated by the laser at each cutting point that will affect the material to be cut, avoid deformation of the cutting area, and make the cut shape consistent with the target shape.

[0019] In a second aspect of the present application, a laser cutting control system for a CNC machine tool is provided, comprising a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, a laser cutting control method for a CNC machine tool according to the first aspect of the present application is implemented.

[0020] The technical solution of this application has the following beneficial technical effects:

[0021] Firstly, the cutting difficulty of each position point in the material to be cut is calculated according to the correlation between material characteristics and cutting quality. The greater the cutting difficulty, the worse the cutting quality of the position point after cutting. Multiple cutting points are selected in the material to be cut, and the number of cutting points is the same as the number of contour points in the target shape. The closed area surrounded by multiple cutting points is the cutting area. The objective function is constructed by comprehensively considering the shape consistency, internal surface quality and cutting difficulty of the cutting area to measure the cutting effect of multiple cutting points. Each cutting point when the objective function takes the minimum value is taken as the first path. Furthermore, considering the influence of laser heat on the cutting area during laser cutting, the heat-affected area and the degree of heat influence of each cutting point are calculated. The heat-affected area and the degree of heat influence are related to the laser power and the dwelling time of the cutting point. The cutting margin is calculated according to the degree of heat influence of multiple heat-affected areas where the cutting point is located. The cutting points in the first path are adjusted according to the cutting margin to obtain the second path. The second path can eliminate the influence of the heat generated by the laser at each cutting point on the material to be cut, avoid deformation of the shape of the cutting area due to heat, and improve the accuracy of laser cutting. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] By reading the detailed description below with reference to the accompanying drawings, the above and other purposes, features and advantages of the exemplary embodiments of the present application will become easy to understand. In the accompanying drawings, several embodiments of the present application are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0023] Figure 1 is a flow chart of a laser cutting control method for a CNC machine tool according to an embodiment of the present application;

[0024] Figure 2 It is a structural block diagram of a laser cutting control system for a CNC machine tool according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0026] It should be understood that when the terms "first", "second", etc. are used in the claims, specification and drawings of the present application, they are only used to distinguish different objects, rather than to describe a specific order. The terms "include" and "comprise" used in the specification and claims of the present application indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their collections.

[0027] According to a first aspect of the present application, the present application provides a laser cutting control method for a CNC machine tool. Figure 1 FIG. 1 is a flow chart of a laser cutting control method for a CNC machine tool according to an embodiment of the present application. Figure 1 As shown, the laser cutting control method for a CNC machine tool includes steps S101 to S105, which are described in detail below.

[0028] S101, determining the cutting difficulty of each position point in the material to be cut according to the correlation between the material characteristics and the cutting quality, wherein the material characteristics include thickness, hardness and surface quality.

[0029] In one embodiment, the purpose of laser cutting is to cut a target shape from the material to be cut. During the cutting process, various material characteristics will affect the cutting quality. The cutting quality is related to the smoothness of the cut surface. The greater the smoothness of the cut surface, the higher the cutting quality.

[0030] Specifically, one position point corresponds to multiple material characteristics, and the material characteristics include thickness, hardness and surface quality; the method for obtaining the correlation between material characteristics and cutting quality includes: in the historical cutting process, collecting arbitrary material characteristics and cutting quality of multiple position points to obtain material characteristic sequence and cutting quality; using the Pearson correlation coefficient of the material characteristic sequence and cutting quality as the correlation between the material characteristics and cutting quality.

[0031] The value range of the Pearson correlation coefficient is When the value of the Pearson correlation coefficient is greater than 0, it means that the cutting quality increases with the increase of material characteristics; when the value of the Pearson correlation coefficient is less than 0, it means that the cutting quality decreases with the increase of material characteristics.

[0032] It should be noted that the cutting quality can be manually marked by those skilled in the art. The thickness and hardness of the material characteristics can be directly measured by sensors; the surface quality can be obtained using the grayscale image of the material to be cut. Specifically, the pixel value of any position point in the grayscale image is obtained, and the difference between the average pixel value in the neighborhood of the position point 8 and the average pixel value of the grayscale image is used as the surface quality of the position point. The larger the difference, the worse the surface quality. Among them, the neighborhood of the position point 8 includes 8 position points adjacent to the position point.

[0033] In one embodiment, after obtaining the correlation between the material characteristics and the cutting quality, the cutting difficulty of each position point can be calculated. The greater the cutting difficulty, the worse the cutting quality of the position point. Difficulty of cutting for: , is the number of material characteristics, Material characteristics Relevance of cutting quality, For location point Material characteristics The value of .

[0034] Understandably, for material characteristics In terms of The larger the value, the better the material characteristics. You can click on the location Get better cutting quality, that is, only from the material characteristics Look, location point The cutting difficulty is relatively small, so The opposite number of The obtained location point The cutting difficulty; the corresponding , the cutting difficulty of each position point can be accurately judged. The greater the cutting difficulty, the worse the cutting quality at the corresponding position point.

[0035] S102, selecting multiple cutting points, constructing an objective function according to the weight of each cutting point, and taking each cutting point when the objective function takes a minimum value as the first path, wherein the weight is positively correlated with the curvature of the cutting point.

[0036] In one embodiment, multiple cutting points are selected in the material to be cut, and the number of the cutting points is the same as the number of contour points of the target shape. The multiple cutting points enclose a closed area, which is the cut area. In order to make the cutting area the same as the target shape, an objective function needs to be constructed to evaluate the cutting effect of the multiple cutting points.

[0037] Specifically, the objective function for:

[0038] ; is the Hu moment of the target shape, is the Hu moment of the cutting area surrounded by the cutting points, is the surface quality in the cutting area, is the number of cutting points, Cut point The weight of Cut point Difficulty of cutting.

[0039] Among them, Hu moment is an image feature with translation, rotation and scale invariance, which can stably obtain the shape characteristics of the target shape and the cutting area. Ability to constrain the consistency between the cutting area and the target shape; is the surface quality in the cutting area, Used to constrain the cutting area to have better surface quality; It is used to constrain the cutting difficulty of all cutting points to be the minimum, among which, the cutting point Weight It is positively correlated with the curvature of the cutting point. The larger the curvature of the cutting point, the more the laser needs to change the cutting direction at that position. The cutting complexity at that position is greater, and a larger weight should be assigned to that position so that the objective function pays more attention to the cutting point with a larger curvature.

[0040] It can be understood that since the Hu moment is a kind of invariance in translation, rotation and scale, even if the cutting area surrounded by the cutting points is different from the target shape in translation, rotation and scale, It is still a small value. However, the effect we want is that the cut area and the target shape can have differences in translation and rotation, but no scale difference is allowed. Therefore, when using While constraining the consistency between the cutting area and the target shape, the number of cutting points is limited to be the same as the number of contour points of the target shape. The size consistency between the cutting area and the target shape is constrained by limiting the number of cutting points.

[0041] Among them, the cutting point Weight for: , Cut point In other embodiments, the cutting point can be directly The curvature of Weight .

[0042] In one embodiment, the plurality of cutting points are continuously updated by using an optimization algorithm, and each cutting point when the objective function takes the minimum value is used as the first path. The number of cutting points in the first path is the same as the number of contour points in the target shape. The material to be cut is cut along the first path, and a cutting area consistent with the target shape can be obtained with the minimum cutting difficulty, and the cutting area has a good surface quality.

[0043] S103, obtaining the heat affected area and heat affected degree of each cutting point.

[0044] In one embodiment, when the material to be cut is cut along the first path, a cutting area with the same target shape can be obtained. However, in the actual cutting process, the heat generated by the laser at each cutting point will affect the material to be cut, causing the shape of the cutting area to be deformed due to heat. In order to improve the cutting accuracy, a cutting margin needs to be allocated to each cutting point.

[0045] Before allocating a cutting margin to each cutting point, the heat affected area and degree of heat influence of each cutting point need to be calculated. The heat affected area and degree of heat influence are related to the heat generated by the laser at the cutting point; specifically, obtaining the heat affected area and degree of heat influence of each cutting point includes: determining the laser power and dwell time of the cutting point according to the thickness and hardness in the material characteristics; the heat affected area is a circular area with a preset radius centered at the cutting point; the degree of heat influence is the product of the laser power and the dwell time.

[0046] The preset radius is 1. In other embodiments, the preset radius can also be adaptively adjusted according to the dwell time. The longer the dwell time is, the farther the heat diffuses. In this case, the preset radius should be increased to expand the heat affected area of ​​the cutting point. Preset radius for:

[0047] ; is the initial radius, The length of stay.

[0048] It can be understood that the laser power can be set to remain unchanged, and each cutting point can be cut by controlling the dwell time. According to the mapping relationship between thickness, hardness and dwell time, the thickness and hardness in the material characteristics are input into the mapping relationship to obtain the dwell time required to cut the cutting point, and then the laser power and dwell time of each cutting point can be obtained.

[0049] S104, calculating the cutting allowance according to the degree of heat influence of the heat-affected zone where the cutting point is located.

[0050] In one embodiment, after obtaining the heat affected area and heat affected degree of each cutting point, the cutting margin of each cutting point is calculated. For example, get the value containing the cut point All heat affected areas and at the cutting point Calculate the cutting point in the heat affected zone Cutting allowance .

[0051] Specifically, the cutting point Cutting allowance for: ; is the initial margin, To include the cutting point The total heat affected area, Heat affected area Middle cutting point Distance to the regional center, Heat affected area The degree of thermal influence, is a Gaussian function.

[0052] The initial margin is set to 0. Since the heat affected area is a circular area, the heat affected area Middle cutting point Distance to regional center Cut point To heat affected area The distance from the center of the circle; is a Gaussian function, which is used to Normalized to values ​​between 0 and 1.

[0053] In this way, when calculating the cutting allowance of any cutting point, the degree of thermal influence of the heat-affected zones of all cutting points on the cutting point is taken into consideration, and the cutting allowance of each cutting point is accurately calculated to avoid deformation of the shape of the cutting area due to heat.

[0054] S105, adjusting the cutting point according to the cutting margin to obtain a second path, and performing laser cutting according to the second path.

[0055] In one embodiment, adjusting the cutting point according to the cutting margin includes: obtaining the tangent direction of any cutting point, and taking the direction perpendicular to the tangent direction and pointing to the outside of the cutting area as the target direction of each cutting point; translating each cutting point along the direction corresponding to the target direction by the distance of the cutting margin to obtain a second path.

[0056] In this way, a cutting margin is allocated to each cutting point in the first path to eliminate the influence of the heat generated by the laser at each cutting point on the material to be cut, avoid deformation of the shape of the cutting area due to heat, and improve cutting accuracy.

[0057] The technical principle and implementation details of a laser cutting control method for a CNC machine tool of the present application are introduced above through specific embodiments. Firstly, the cutting difficulty of each position point in the material to be cut is calculated according to the correlation between material characteristics and cutting quality. The greater the cutting difficulty, the worse the cutting quality of the position point after cutting. Multiple cutting points are selected in the material to be cut, and the number of cutting points is the same as the number of contour points in the target shape. The closed area surrounded by multiple cutting points is the cutting area. The objective function is constructed by comprehensively considering the shape consistency, internal surface quality and cutting difficulty of the cutting area to measure the cutting effect of multiple cutting points. Each cutting point when the objective function takes the minimum value is taken as the first path. Furthermore, considering the influence of laser heat on the cutting area during laser cutting, the heat-affected area and the degree of heat influence of each cutting point are calculated. The heat-affected area and the degree of heat influence are related to the laser power and the dwelling time of the cutting point. The cutting margin is calculated according to the degree of heat influence of multiple heat-affected areas where the cutting point is located. The cutting points in the first path are adjusted according to the cutting margin to obtain the second path. The second path can eliminate the influence of the heat generated by the laser at each cutting point on the material to be cut, avoid deformation of the shape of the cutting area due to heat, and improve the accuracy of laser cutting.

[0058] According to the second aspect of the present application, the present application also provides a laser cutting control system for a CNC machine tool. Figure 2 1 is a block diagram of a laser cutting control system for a CNC machine tool according to an embodiment of the present application. Figure 2As shown, the system 50 includes a processor and a memory, the memory stores computer program instructions, and when the computer program instructions are executed by the processor, a laser cutting control method for a CNC machine tool according to the first aspect of the present application is implemented. The system also includes other components well known to those skilled in the art, such as a communication bus and a communication interface, whose settings and functions are known in the art, so they are not described here.

[0059] In the present application, the aforementioned memory may be any tangible medium containing or storing a program that can be used by or in combination with an instruction execution system, system or device. For example, a computer-readable storage medium may be any appropriate magnetic storage medium or magneto-optical storage medium, such as a resistive random access memory RRAM (Resistive Random Access Memory), a dynamic random access memory DRAM (Dynamic Random Access Memory), a static random access memory SRAM (Static Random-Access Memory), an enhanced dynamic random access memory EDRAM (Enhanced Dynamic Random Access Memory), a high-bandwidth memory HBM (High-Bandwidth Memory), a hybrid memory cube HMC (Hybrid Memory Cube), etc., or any other medium that can be used to store the required information and can be accessed by an application, a module, or both. Any such computer storage medium may be part of a device or accessible or connectable to a device. Any application or module described in this application may be implemented by computer-readable / executable instructions stored or otherwise maintained by such a computer-readable medium.

[0060] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A laser cutting control method for a CNC machine tool, characterized in that: The control method comprises: determining the cutting difficulty of each position point in the material to be cut according to the correlation between the material characteristics and the cutting quality, wherein the material characteristics include thickness, hardness and surface quality; Select multiple cutting points, construct an objective function based on the weight of each cutting point, and use each cutting point when the objective function takes the minimum value as the first path. The weight is positively correlated with the curvature of the cutting point. for: ; is the Hu moment of the target shape, is the Hu moment of the cutting area surrounded by the cutting points, is the surface quality in the cutting area, is the number of cutting points, Cut point The weight of Cut point The number of cutting points is the same as the number of contour points of the target shape; Obtain the heat affected area and heat impact degree of each cutting point, including: determining the laser power and dwell time of the cutting point according to the thickness and hardness in the material characteristics; the heat affected area is a circular area with the cutting point as the center and a preset radius; the heat impact degree is the product of the laser power and the dwell time; Calculating a cutting margin according to the degree of heat influence of the heat-affected zone where the cutting point is located; adjusting the cutting point according to the cutting margin to obtain a second path, and performing laser cutting according to the second path; Cutting Point Cutting allowance for: ; is the initial margin, To include the cutting point The total heat affected area, Heat affected area Middle cutting point Distance to the regional center, Heat affected area The degree of thermal influence, is a Gaussian function.

2. A laser cutting control method for a CNC machine tool according to claim 1, characterized in that: Methods for obtaining the correlation between material characteristics and cutting quality include: In the historical cutting process, any material characteristics and cutting quality at multiple locations are collected to obtain the material characteristic sequence and cutting quality; The Pearson correlation coefficient between the material feature sequence and the cutting quality is used as the correlation between the material feature and the cutting quality.

3. The laser cutting control method for a CNC machine tool according to claim 1, characterized in that: Location Point Difficulty of cutting for: , is the number of material characteristics, Material characteristics Relevance of cutting quality, For location point Material characteristics The value of .

4. The laser cutting control method for a CNC machine tool according to claim 1, characterized in that: Cutting Point Preset radius for: ; is the initial radius, The length of stay.

5. The laser cutting control method for a CNC machine tool according to claim 1, characterized in that: The adjusting the cutting point according to the cutting margin comprises: Get the tangent direction of any cutting point, and take the direction perpendicular to the tangent direction and pointing to the outside of the cutting area as the target direction of each cutting point; Each cutting point is translated along the direction corresponding to the target direction by the distance of the cutting margin to obtain a second path.

6. The laser cutting control method for a CNC machine tool according to claim 1, characterized in that: Cutting Point Weight for: , Cut point The curvature.

7. A laser cutting control system for a CNC machine tool, characterized in that: The invention comprises a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, a laser cutting control method for a numerically controlled machine tool according to any one of claims 1 to 6 is implemented.

Images