Laser processing control method and system for preventing laser overburning

Abstract

The application discloses a kind of laser processing control method and system for preventing laser overburning, its method includes mutation region identification;Degree of mutation judgment;Laser processing parameter adjustment condition and control node insertion condition and method;Normal direction smooth reconstruction between control nodes;Normal vector group coupling engraving path and matching laser processing parameter generate laser head processing control instruction;The control method and system significantly reduce the overburning incidence rate of path corner structure through path optimization and dynamic power regulation, control ablation depth fluctuation, improve the consistency of engraved line width, meet the laser processing precision requirement;The path optimization algorithm is simple and efficient, and the path re-planning time is short;And after path optimization, the continuity of laser processing is improved, the engraving speed of complex curved surface is improved, and through the normal optimization of laser head, the laser processing system can process steep curved surface with a radius of curvature of 50mm or even larger, and can support laser processing of various ship materials such as carbon steel and aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of laser processing technology, specifically to a laser processing control method and system for preventing laser overheating. Background Technology

[0002] Laser three-dimensional structural line marking technology is a processing method that uses a laser beam to scan a predetermined path on the surface of a workpiece to form a mark. Its working principle is as follows: the control system generates a marking path based on a three-dimensional model and drives the laser head to dynamically adjust its spatial pose and process parameters (such as power and frequency) so that the laser energy forms a precise etching trajectory on the material surface.

[0003] This technology has significant problems in the processing of complex spatial curved surfaces: 1) At the corners of the path or the workpiece structure, the laser beam experiences a sudden change in direction, leading to energy accumulation, causing local overburning and disrupting the consistency of the engraved line width. For structural corners, the laser head reduces its cutting rate to change direction and performs adaptive attitude adjustment. The cutting speed of the laser beam is coupled with the rotation and movement of the laser head, resulting in poor consistency of the laser beam cutting speed at the corner. Some existing technologies typically use the method of interrupting the cutting program to adjust the laser head attitude when cutting at structural corners. Obviously, although this method solves the overburning problem, it will lead to discontinuous processing. For path corners, traditional solutions use fixed-parameter rounded corner processing paths or empirical power reduction, but they cannot simultaneously achieve energy balance control and real-time interference avoidance. Moreover, oversimplifying the path will reduce the engraving accuracy and make it difficult to meet the processing requirements of high-value-added workpieces. 2) In the dynamic engraving of three-dimensional curved surfaces, the path planning also needs to consider collision and interference issues. Due to the lag in the adjustment of the laser head tilt angle, it is easy for the laser head or laser beam to collide with the workpiece surface or non-processed curved surfaces or cause optical interference. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects in the prior art and provide a laser processing control method and system for preventing laser overburning, so as to overcome one or more problems caused by the limitations and defects of related technologies to a certain extent.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A laser processing control method for preventing laser overheating includes the following steps:

[0007] S1. Adaptively generate the marking path and path control points based on the workpiece's three-dimensional curved surface, and analyze and identify the marking path; preset the threshold P for the rate of change of the normal angle within a unit step, and based on the rate of change of the normal angle within a unit step... Search and identify abrupt change regions in the path normal direction to determine the surface corner structure and triangular corner structure;

[0008] S2. Preset the control threshold M of the normal angle within a unit step size, perform local analysis on the path control point sequence of the mutation region, and determine its mutation degree based on the change rate threshold P and the control threshold M.

[0009] S3 At the same time, while maintaining the original path normal vector set, adjust the laser processing parameters. At the same time, control nodes are inserted at the front and rear ends of the mutation region to pre-adjust the attitude of the laser head when entering the mutation region, delay the adjustment of the attitude after the laser head leaves the mutation region, and set the process compensation amount to adjust the laser processing parameters within the interval of the two control nodes.

[0010] S4. Smoothly reconstruct the normal direction between the two control nodes, and use an interpolation algorithm to generate a set of normal vectors for a smooth transition, so that the laser head attitude changes smoothly through the abrupt change region.

[0011] S5. Imprint the path coupling normal vector group and match it with the corresponding laser processing parameters for binding output.

[0012] Furthermore, the path recognition in step one also includes the recognition of sharp corner structures on the path. A recognition step size is set, and processing point A (one recognition step size in front of processing point B) and processing point C (one recognition step size in back of processing point B) are read progressively to construct a horizontal vector. and Calculate the angle between vectors If the angle between the vectors If the angle is less than the critical angle, then processing point B is picked up.

[0013] Furthermore, extended compensation nodes are inserted to avoid energy concentration in sharp-corner structures along the path, and compensation amounts are set along... The vector extends outward from processing point B to compensation point D, along... The vector extends outward from processing point B to compensation point E, generating a new path. .

[0014] Furthermore, step S2 also includes path-by-path point analysis to identify redundant path points, when When a mutation region is searched, if the distance between adjacent path control points is less than the preset redundancy distance, or if a path control point deviates from the path direction and the deviation angle is less than the preset redundancy angle, it is determined to be a redundant path point and deleted.

[0015] Furthermore, the criteria for determining regions where the normal direction abruptly changes are: the rate of change threshold P is 3° / step, and the control threshold M is 5° / step; after smooth reconstruction in step S3, the attitude adjustment rate of the laser head within the abrupt change region is... satisfy: .

[0016] Furthermore, the adjustment of laser processing parameters includes the adjustment of the scanning speed, which is determined linearly based on the rate of change of the angle. Adjustments will be made accordingly, with a maximum downward adjustment of 60% of the original value and a maximum upward adjustment of 120% of the original value.

[0017] Furthermore, path identification also includes the identification of interference paths. This involves searching for potential interference regions where the cumulative tilt angle change is greater than or equal to a preset risk angle and where the normals exhibit dense changes. The actual interference situation in each potential interference region is confirmed. If a potential interference region exists where there is a risk of mechanical interference to the laser head or a risk of beam path intersection, the laser head tilt angle at the path control points at both ends of the potential interference region is read. and The tilt angles of both are compensated by the rated gradient change to reduce the cumulative tilt angle change within the potential interference region until the potential interference region is free from interference risk. The laser head correction tilt angle at the path control points at both ends of the potential interference region is then determined. and .

[0018] Furthermore, if the potential interference region of the mutation is located between control nodes, the attitude adjustment rate from the path control points at both ends of the potential interference region to the control nodes needs to be adjusted. If the attitude adjustment rate exceeds 5° / mm, the position of the control node is adjusted, and the final output is the control command output with the corrected normal vector group coupled to the path.

[0019] A laser processing system includes a laser, a motion system, a control system, and a monitoring module. The laser is a fiber laser with narrow spectrum, high beam quality, and high reflection resistance. Its laser wavelength is 1060-1080 nm, spot size is 5-7 mm, and response rate is less than 20 μs. The laser generation, output energy, and pulse frequency are controlled by MOPA hierarchical control technology. The laser is mounted on the motion system. The control system generates control commands based on the processing path of the coupled normal vector to control the motion system and controls the laser output based on the matched process parameter information. The monitoring module monitors the position of the laser in real time and feeds back to the control system to achieve closed-loop control of laser processing.

[0020] Compared with the prior art, the laser processing control method and system for preventing laser overburning of the present invention have the following beneficial effects:

[0021] This control method and system significantly reduces the overburn rate of path corner structures through path optimization and dynamic power adjustment, controls the fluctuation of ablation depth, improves the consistency of the engraved linewidth, and meets the accuracy requirements of laser processing. The path optimization algorithm is simple and efficient, and the path replanning time is short. Moreover, the path optimization improves the continuity of laser processing, increases the engraving speed of complex curved surfaces, and through laser head normal optimization, this laser processing system can handle steep curved surfaces with a curvature radius of 50mm or even larger, and can support the laser processing of various marine materials such as carbon steel and aluminum alloys. Attached Figure Description

[0022] Figure 1 This is a control flowchart of the laser processing control method of the present invention;

[0023] Figure 2 A comparative diagram of the original path normal vector set and the normal vector set after inserting control points and smoothing reconstruction in the mutation region; where Y is the original path normal vector set and X is the reconstructed normal vector set;

[0024] Figure 3 A schematic diagram of the path leading out of the sharp corner structure;

[0025] Figure 4 A schematic diagram of laser head adjustment at the entry end of the potential interference region of abrupt change;

[0026] Figure 5 A schematic diagram of laser head adjustment at the exit end of the potential interference region of abrupt change;

[0027] Figure 6 A schematic diagram of redundant path points that deviate from the path;

[0028] Figure 7 This is a schematic diagram of the components of a laser processing system. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely the best embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] To address the issue of overburning in corner areas during laser processing, this embodiment provides a laser processing control method to prevent laser overburning, such as... Figure 1 As shown, it includes the following content and steps:

[0031] S1. Load the imprinted image onto the three-dimensional curved surface of the workpiece, adaptively generate the imprinting path, and generate path control points based on the path step size and key nodes of the path.

[0032] Search and identify regions where the path normal direction changes abruptly: A preset threshold P for the rate of change of the normal angle within a unit path length is used; in this embodiment, P is set to 3° / step. The 3D imprinted path is searched and calculated based on the path control points to calculate the rate of change of the normal angle within a unit step length. Identify regions of abrupt changes in normal and the rate of change of normal angle. Corner structures with a step size greater than 3° include identifying and locking curved corner structures and triangular corner structures as triggering conditions for subsequent laser processing parameter adjustments;

[0033] S2. Further preset the control threshold M for the normal angle within a unit step size. In this embodiment, it is set to 5° / step size. Perform local analysis on the path point sequence of the mutation region to further distinguish the degree of mutation in the mutation region. For mutation regions exceeding the control threshold M, identify and delete redundant path points that have little impact on path control accuracy, reduce the dwell time of the laser head on redundant path points, and analyze each path point to determine if the path distance between it and its adjacent path point at the front end is less than the preset redundancy distance, or if the path control point deviates from the path direction, such as... Figure 6 As shown, when path control point G deviates from the path vectors established by its preceding and following adjacent path control points I and J, respectively... and And its deviation vector and The deviation angle between ,as well as and The deviation angle between When all the values ​​are less than the preset redundancy angle, the path point is deleted as a redundant path point. In this embodiment, the redundancy distance is 0.1mm and the redundancy angle is set to 5°. Removing redundant path points can reduce the accumulation of processing energy in the abrupt change region and provide spatial redundancy for the subsequent smooth transition of normals.

[0034] S3. Adjust processing parameters and smooth normals in regions with abrupt changes in normals. When the degree of change is within acceptable limits, the original path normal direction can be maintained. At this point, it is assumed that the adaptively generated normal direction group transitions smoothly enough, and only the laser processing parameters are adjusted.

[0035] At that time, based on experience, control nodes w and t are inserted at certain distances at the front and rear ends of the mutation region, respectively, such as... Figure 2 As shown, the attitude of the laser head entering the UV abrupt change region is pre-adjusted, the attitude of the laser head after exiting the UV abrupt change region is delayed, and the laser processing parameters within the two control node intervals are adjusted by setting the process compensation amount.

[0036] S4. Smoothly reconstruct the normal direction of the path between two control nodes containing abrupt changes in normal direction. An interpolation algorithm is used to reconstruct the attitude sequence between control nodes. If the normal direction of the abrupt change in normal direction is continuously changing, the abrupt change in normal direction is considered to be a curved corner structure, and the interpolation algorithm used is the Slerp algorithm. If the normal direction of the abrupt change in normal direction is step or discontinuous, the abrupt change in normal direction is considered to be a triangular corner structure, and the interpolation algorithm used is the cubic spline interpolation algorithm. Thus, a set of smoothly transitioning normal vectors is generated along the path between the two control nodes.

[0037] After smooth reconstruction, calculate the attitude adjustment rate of the laser head in the region of abrupt change in normal. ,when It is assumed that the laser head's attitude changes smoothly through the abrupt change region, if Then repeat step 2, extending the control node by one path step, until the attitude adjustment rate meets the smooth transition requirement. If so, adjust the control nodes accordingly.

[0038] S5. Couple the smoothed and reconstructed normal vector group to the new path after removing redundant path points, bind the output laser head's running trajectory and attitude to generate laser head processing control commands, and ensure the continuity of laser engraving processing.

[0039] In this embodiment, path recognition also includes the recognition of sharp corner structures on the path, i.e., path plane corners with small angles. Using a contour analysis algorithm, a recognition step size is set to n path steps, where n is set based on the arc length of the small-radius rounded corner to ignore the influence of the sharp corner's small-radius rounded corner structure in the index. Processing point A, located one recognition step size from the front end of processing point B, and processing point C, located one recognition step size from the rear end of processing point B, are read step by step to construct a horizontal vector. and Calculate the angle between vectors If the angle between the vectors If the angle is less than the critical angle, processing point B will be picked up. In this embodiment, the critical angle is set to 150°.

[0040] like Figure 3 As shown, the handling of sharp-corner structures in the path involves adding an extraction and introduction path. This avoids energy focusing effects caused by excessively sharp corners while maintaining constant laser beam power / frequency parameters, omitting parameter adaptation and adjustment steps, and improving the ease and reliability of operation. To simplify the design and calculation of the extraction and introduction path, a fixed compensation amount is set, typically 0.1mm-0.3mm, along... The vector is extended outward from processing point B by a compensation amount to compensation point D, increasing the lead-out path. ,along The vector is extended outward from processing point B by a compensation amount to compensation point E, increasing the introduced path. Therefore, the original path of the sharp-angled structure of the path Extend and generate new paths .

[0041] It needs further explanation that, specifically, the process compensation for abrupt changes includes compensation for scanning speed, laser power, and pulse period. Specifically, the adjustment of scanning speed is related to the angle change rate. The relationship is linear, with the maximum downward adjustment being 60% of the original value and the maximum upward adjustment being 120% of the original value. When the abrupt change region is a region of dense normals, i.e., the rate of change of angle... When the value is negative, the scan speed should be reduced; conversely, in areas with sparse normals, the scan speed should be increased. At the same time, maintain the original scanning speed. The scanning speed is 80% of the original scanning speed. The scanning speed is 60% of the original scanning speed. The scanning speed is 120% of the original scanning speed. At the same time, the laser power is dynamically adjusted, that is, the output laser power is reduced or increased accordingly, and the pulse period is extended or shortened for adaptive compensation to ensure that the laser focus and scanning speed are stably matched.

[0042] In this embodiment, in areas with dense and abrupt changes in normals where the cumulative change in tilt angle is large, generally when the change is greater than 75°, the laser head deflects excessively, which can easily lead to interference risks. In order to prevent dynamic interference between the laser head and the workpiece surface, or interference between the laser beam and the unprocessed surface, it is also necessary to identify potential interference areas. Potential interference areas can be quickly searched by calculating the cumulative change in tilt angle of the abrupt area. After completing the path planning, the actual interference situation of the potential interference area is confirmed based on the processing trajectory and beam path of the laser head determined by the path and its normal vector.

[0043] If there is a risk of mechanical interference between the laser head and the workpiece surface, or a risk of the beam path intersecting with a non-marked position, then the laser head tilt angle at the path control points at both ends of the potential interference region caused by abrupt path changes should be read. and The cumulative change in tilt angle between the two is compensated by the rated gradient until the interference risk area is removed from the interference risk area, such as... Figure 4 and Figure 5 As shown, the change in the original dip angle of the OQ region is , The normal angle is gradually decreased by a gradient of 1°. The normal angle is gradually increased in increments of 1°. When the laser head tilt angle at point O decreases by 15°, = -15°, the laser head tilt angle at point Q increases by 15°. = +15°, then the change in the normal tilt angle after correction in the OQ mutation region is: The change is reduced by 30° compared to the original, which significantly reduces the attitude change of the laser head in the potential interference region of abrupt change, and the potential interference region of abrupt change is removed from the interference risk.

[0044] If the potential interference region of a mutation is located within the control node interval, the change in the tilt angle of points O and Q increases the cumulative adjustment amount of the tilt angle between the control node and the path control points at both ends of the potential interference region of a mutation. This may cause the attitude adjustment rate in this transition region to exceed 5° / mm. In this case, the position of the control node should be adjusted outward to make the attitude adjustment rate in this transition region meet the technical requirements or adapt to the OQ mutation region. Finally, the output is the control command output with the corrected normal vector coupled path.

[0045] This embodiment also provides a laser processing system, such as Figure 7 As shown, it includes a laser, a motion system, a control system, and a monitoring module. The control system includes a display unit, a main control unit, a motion control unit, and an engraving control unit; wherein,

[0046] The main control unit intelligently analyzes the imprinting path and path control points automatically generated by the 3D system, automatically optimizes and smooths the imprinting path, and generates the imprinting trajectory and process parameter information of the coupled normal vector. The imprinting path command and attitude adjustment command are sent to the motion control unit, and the process parameter information is sent to the imprinting control unit. At the same time, the imprinting path and process parameters are synchronized to the display unit.

[0047] The motion control unit synchronously triggers the motion system's moving motor and attitude adjustment motor; the marking control unit triggers the laser to generate a laser beam with specified power and pulses. The laser is a fiber laser with narrow spectrum, high beam quality and anti-high reflection characteristics. Its laser wavelength is 1060-1080nm, the spot size is 5-7mm, and the response rate is less than 20μs. Its laser generation, output energy and pulse frequency are controlled by MOPA graded control technology.

[0048] The monitoring module monitors the position of the laser in real time and feeds back to the control system to achieve closed-loop control of laser processing.

[0049] Through the above description of the embodiments, those skilled in the art can clearly understand that the various embodiments of this application can be implemented by means of software or software combined with necessary general-purpose hardware platforms, and of course, they can also be implemented by hardware functions. Based on this understanding, the technical solution of this application, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. The software product is stored in a storage medium and includes several instructions to cause a computer device, such as including but not limited to a personal computer, server, or network device, to execute all or part of the steps of the method described in any embodiment of this application.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A laser processing control method to prevent laser overheating, characterized in that, Includes the following steps: S1. Generate an engraving path and path control points adaptively based on the three-dimensional curved surface of the workpiece, and identify and analyze the engraving path; The threshold value P for the rate of change of the normal angle within a unit step size is preset, and the rate of change of the normal angle within a unit step size is used as the basis for this. Search and identify abrupt change regions in the path normal direction to determine the surface corner structure and triangular corner structure; S2. Set a control threshold M for the normal angle within a unit step size, perform local analysis on the sequence of path control points in the mutation region, and determine the degree of mutation based on the rate of change threshold P and the control threshold M. S3 At the same time, maintain the normal vector group of the engraving path and adjust the laser processing parameters; At the same time, control nodes are inserted at the front and rear ends of the mutation region to pre-adjust the attitude of the laser head when entering the mutation region, delay the adjustment of the attitude after the laser head leaves the mutation region, and set the process compensation amount to adjust the laser processing parameters within the interval of the two control nodes. S4. Smoothly reconstruct the normal direction between the two control nodes, and use an interpolation algorithm to generate a group of normal vectors with a smooth transition, so that the laser head attitude changes smoothly through the abrupt change region; S5. The engraving path is coupled with the normal vector group and matched with the corresponding laser processing parameters for binding output.

2. The laser processing control method for preventing laser overheating according to claim 1, characterized in that: The path recognition in step one also includes the recognition of sharp corner structures in the path. A recognition step size is set, and processing points A (before and after B, the recognition step size is increased) and C (before and after B, the recognition step size is increased) are read progressively to construct a horizontal vector. and Calculate the angle between vectors If the included angle of the vectors If the angle is less than the critical angle, then the processing point B is picked up.

3. The laser processing control method for preventing laser overheating according to claim 2, characterized in that: Insert extension compensation nodes to avoid energy concentration in the path's sharp corner structure, and set the compensation amount along... The vector extends outward from processing point B to compensation point D, along... The vector extends outward from processing point B to compensation point E, generating a new path. .

4. The laser processing control method for preventing laser overheating according to claim 1, characterized in that: Step S2 also includes analyzing and identifying redundant path points one by one, when When the mutation region is searched, if the distance between adjacent path control points is less than a preset redundancy distance, or if the path control point deviates from the path direction and the deviation angle is less than a preset redundancy angle, then it is determined to be a redundant path point and deleted.

5. The laser processing control method for preventing laser overheating according to claim 4, characterized in that: The criteria for determining the abrupt change region of the normal direction change are: the rate of change threshold P is 3° / step, and the control threshold M is 5° / step; after smooth reconstruction in step S3, the attitude adjustment rate of the laser head within the abrupt change region. satisfy: .

6. The laser processing control method for preventing laser overheating according to claim 5, characterized in that: The adjustment of the laser processing parameters includes the adjustment of the scanning speed, which is based on the angle change rate. Linear adaptive adjustment is performed, with a maximum downward adjustment of 60% of the original value and a maximum upward adjustment of 120% of the original value.

7. The laser processing control method for preventing laser overburning according to claim 5 or 6, characterized in that: Path identification also includes the identification of interference paths. This involves searching for abrupt potential interference regions where the cumulative tilt angle change is greater than or equal to a preset risk angle and where the normals exhibit dense changes. The actual interference situation of each abrupt potential interference region is confirmed. If any abrupt potential interference region exists that poses a risk of mechanical interference to the laser head or a risk of beam path intersection, the laser head tilt angle at the path control points at both ends of the abrupt potential interference region is read. and The tilt angles of both are compensated by the rated gradient change, reducing the cumulative tilt angle change within the potential interference region until the potential interference region is free from interference risk. The laser head correction tilt angle at the path control points at both ends of the potential interference region is then determined. and .

8. The laser processing control method for preventing laser overheating according to claim 7, characterized in that: If the potential interference region of mutation is located between the control nodes, the attitude adjustment rate of the path control points at both ends of the potential interference region to the control node needs to be adjusted. If the attitude adjustment rate exceeds 5° / mm, the position of the control node is adjusted, and finally the output is a control command coupled with the imprinted path using the corrected normal vector group.

9. A laser processing system for implementing the laser processing control method according to any one of claims 1 to 8, characterized in that: The system includes a laser, a motion system, a control system, and a monitoring module. The laser is a fiber laser with narrow spectrum, high beam quality, and high reflection resistance. Its laser wavelength is 1060-1080nm, spot size is 5-7mm, and response rate is less than 20μs. The laser generation, output energy, and pulse frequency are controlled by MOPA hierarchical control technology. The laser is mounted on the motion system. The control system generates control commands based on the processing path of the coupled normal vector to control the motion system and controls the output of the laser based on the matched process parameter information. The monitoring module monitors the position of the laser in real time and feeds back to the control system to achieve closed-loop control of laser processing.

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