A laser sanding composite polishing and polishing layer thickness self-adaptive adjusting method and device

Abstract

The present application relates to a kind of laser sanding composite polishing and polishing layer thickness self-adapting adjustment method and device, belong to the field of precision surface processing, the device of the present application includes visual camera detection module, short pulse ablation laser system, long pulse heat softening laser system, mechanical sanding polishing module and electric control system.Self-adapting adjustment method includes: preset parameter and scan workpiece profile and thickness;Short pulse laser removes hard oxide skin and hard point, long pulse laser softens matrix;Flexible sanding and synchronous acquisition sand belt wear morphology;Closed-loop PID system automatically fine-tunes laser power, feed depth and sanding contact pressure.The present application realizes the differential treatment of different polishing allowance area, greatly improves workpiece surface flatness, size consistency and processing yield, and is suitable for metal plate, composite row material, section bar, die steel and other precision surface polishing.

Description

Technical Field

[0001] This invention belongs to the field of precision surface processing technology, specifically relating to a laser sand grinding composite grinding and an adaptive adjustment method and device for grinding layer thickness, which is applicable to precision surface grinding of workpieces such as metal plates, copper-aluminum composite strips, profiles, mold steel and aluminum alloy components. Background Technology

[0002] In industrial production, workpieces such as metal sheets, copper-aluminum composite bars, mold steel, and aluminum alloy components all require surface grinding during processing to remove oxide layers, burrs, unevenness, and machining allowances, thereby obtaining finished products that meet dimensional accuracy and surface quality requirements. Surface grinding technology has wide applications in aerospace, automotive manufacturing, electronic components, and building profiles, and the grinding quality directly affects the processing accuracy of subsequent processes and the performance of the final product.

[0003] Currently, the surface grinding technologies widely used in industrial sites mainly include the following technical routes: (1) Traditional mechanical sanding technology, which adopts a mechanical grinding method with fixed pressure and fixed feed, and removes materials through mechanical friction between the sand belt or grinding wheel and the workpiece surface. The core equipment of this technical solution includes a sand belt wheel, annular sand belt, grinding floating seat and drive motor. The operator sets the sand belt speed and contact pressure according to experience, and the workpiece passes through the grinding station at a fixed speed. This solution has a simple equipment structure and low cost, but for workpieces with large differences in surface condition, the fixed process parameters cannot achieve adaptive adjustment, resulting in poor surface quality consistency after grinding; (2) Laser-assisted grinding technology, which uses laser to pre-treat the workpiece surface, softens the material or removes the surface oxide layer through the laser thermal effect, and then performs mechanical grinding. This technical solution improves grinding efficiency to a certain extent, but existing laser-assisted grinding solutions mostly use continuous lasers or single-pulse lasers. When a continuous laser acts on the surface of a workpiece, it will generate a large area of ​​high-temperature hot recast layer, causing the workpiece to expand and deform as a whole, making it difficult to control the subsequent sanding accuracy. A single-pulse laser is difficult to meet the two different processing requirements of removing hard oxide layers and softening the substrate at the same time. (3) Adaptive grinding technology, which detects the surface state of the workpiece through sensors and dynamically adjusts the grinding parameters according to the detection results. For example, Chinese patent application with publication number CN201911065339 proposes a grinding equipment and grinding method for composite material components, which scans the surface of the component in real time through a laser feedback device and transmits data to the controller to dynamically adjust the grinding path and thickness. However, this solution only focuses on the adjustment of the grinding path and thickness, does not involve the composite process of laser pretreatment and mechanical sanding, and does not consider the influence of sand belt wear on grinding accuracy. For example, Chinese patent application CN202010630442X proposes a laser additive manufacturing system and method based on closed-loop control. Although it involves the concept of closed-loop control, its application scenario is laser additive manufacturing repair, rather than surface grinding, and the technical solutions are fundamentally different.

[0004] The existing technology has the following shortcomings and defects: (1) The thickness of the polished layer depends on manual adjustment based on experience, and lacks an online detection closed-loop mechanism. In the process of traditional mechanical sanding equipment, operators control the amount of polishing by visual inspection and manual adjustment, which cannot achieve real-time accurate measurement and automatic feedback adjustment of the thickness. This open-loop control method results in poor thickness consistency. In the same batch of workpieces, the thickness of the polished layer at different locations may fluctuate greatly, which can easily lead to problems such as over-polishing that damages the substrate or under-polishing that leaves defects.

[0005] (2) Mechanical grinding alone is weak in removing hard spots and dense oxide layers on the surface. Metal workpieces usually have defects such as oxide scale with high hardness, local hard spots and welding spatter. The hardness of these defect areas is much higher than that of the base material. Mechanical grinding is extremely inefficient when dealing with these areas and can easily lead to rapid wear or even breakage of the abrasive belt, which increases the cost of consumables and downtime.

[0006] (3) Ignoring the changes in grinding allowance caused by abrasive belt wear. During use, the abrasive grains of the abrasive belt will gradually wear off and fall off, resulting in a decrease in the effective cutting ability of the abrasive belt. Under fixed process parameters, as the abrasive belt wear intensifies, the actual grinding removal amount gradually decreases, resulting in inconsistent grinding layer thickness of workpieces processed before and after the same batch, which seriously affects the dimensional accuracy of mass production.

[0007] (4) The surface of the workpiece is uneven, and the fixed process parameters cannot be adapted to local differences. The actual workpiece surface often has varying degrees of unevenness. Larger grinding allowance is required for raised areas, while smaller grinding allowance is required for recessed areas. The fixed parameter grinding method cannot be differentiated according to the local surface morphology, resulting in insufficient grinding of raised areas and excessive grinding of recessed areas, making it difficult to unify the surface roughness and dimensional accuracy of the finished product.

[0008] (5) Lack of automatic detection and adaptive adjustment mechanism, resulting in low yield rate in mass production. Existing grinding equipment relies heavily on manual intervention. Operators need to frequently stop the machine to check the workpiece size and manually adjust the process parameters. This not only results in high labor intensity and low production efficiency, but also makes it difficult to avoid adjustment errors caused by human factors. The degree of automation is low and it is difficult to meet the needs of large-scale precision machining.

[0009] In summary, existing grinding technologies have significant shortcomings in terms of precise thickness control, removal of hard defects, abrasive belt wear compensation, local adaptive processing, and automation. There is an urgent need for a comprehensive technical solution that can achieve laser pretreatment combined with mechanical abrasive grinding, online detection of grinding layer thickness, and closed-loop adaptive adjustment. Summary of the Invention

[0010] To address the problems of uncontrollable grinding layer thickness, uneven grinding allowance, low precision of manual adjustment, difficulty in removing hard spot defects, low efficiency of single grinding methods, and poor surface consistency in existing technologies, this invention provides a laser sand grinding composite grinding method and device for adaptive adjustment of grinding layer thickness.

[0011] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for laser abrasive grinding composite grinding and adaptive adjustment of grinding layer thickness, comprising the following steps: Step S1. Preset the target data of the workpiece to be polished in the electronic control system. The target data includes the thickness of the polishing layer in a single pass, the allowable thickness tolerance, the laser power range, the belt speed and the initial contact pressure. Step S2. The workpiece to be polished is transported to the processing station. The front surface contour and initial thickness of the workpiece to be polished are scanned by the vision camera detection module. Polishing motion data is generated based on the collected front surface contour and initial thickness. The polishing motion data includes the polishing motion trajectory and the polishing thickness data of the motion trajectory nodes. Step S3. The workpiece to be polished is pre-treated by laser using a dual-channel partitioned pulsed laser system. First, the short-pulse ablation laser system of the dual-channel partitioned pulsed laser system removes the hard oxide scale on the surface of the workpiece according to the polishing motion trajectory. Then, the substrate is softened by low heat using the long-pulse thermal softening laser system of the dual-channel partitioned pulsed laser system. Step S4. The surface of the workpiece to be polished after laser pretreatment is uniformly and flexibly polished by the mechanical sand grinding module. At the same time, the wear morphology of the abrasive particles on the sand belt is synchronously collected by the built-in micro-splitter optical path of the vision camera detection module so as to adjust the sand belt feed and sand grinding contact pressure in real time. Step S5. Compare the grinding motion data during the grinding process with the target data in real time. If the data exceeds the tolerance range, the laser power, laser softening area, feed depth and sanding pressure are automatically fine-tuned through the closed-loop PID adaptive adjustment system to achieve continuous adaptive constant thickness grinding.

[0012] Furthermore, the vision camera detection module includes a laser displacement sensor, a line scan camera, and a thickness test probe; the laser displacement sensor is used to collect the surface contour data of the workpiece to be polished in real time, the line scan camera is used to acquire a two-dimensional morphological image of the surface of the workpiece to be polished, and the thickness test probe is used to measure the reference thickness of the workpiece before polishing and the remaining thickness after polishing, and to calculate the thickness of the layer removed in a single polishing based on the reference thickness before polishing and the remaining thickness after polishing.

[0013] Furthermore, the short-pulse ablation laser system has a laser wavelength of 1030 nm, a pulse width of 200 fs to 100 ps, ​​a power of 15 W to 60 W, a frequency of 200 kHz to 3 MHz, a single pulse energy of 1 to 15 μJ, and a defocusing amount of -0.1 mm to 0.6 mm; the long-pulse thermal softening laser system has a laser wavelength of 1064 nm, a pulse width of 200 ns to 1000 ns, a power of 40 to 200 W, a frequency of 20 kHz to 500 kHz, a single pulse energy of 0.2 to 1.5 mJ, and a defocusing amount of 0.4 mm to 1.2 mm.

[0014] Furthermore, the step of using a dual-channel partitioned pulsed laser system to perform laser pretreatment on the workpiece to be polished also includes partitioning the workpiece according to the polishing allowance of different areas on the surface of the workpiece. For areas with large allowance, the softening distance of the long-pulse thermal softening laser is extended while the short-pulse ablation laser and the long-pulse thermal softening laser are turned on simultaneously. For areas with small allowance, only the short-pulse ablation laser is turned on. The small allowance areas include hard oxide scale areas, protruding defect areas, and local hard spot areas.

[0015] Furthermore, the mechanical sanding and polishing module includes a sanding belt wheel, an annular sanding belt, a sanding floating seat, a variable frequency speed control motor, and a buffer and shock absorption assembly; the sanding belt has a mesh size of 80# to 1200#; the vision camera detection module has a built-in miniature beam splitter, which synchronously collects the wear morphology of the abrasive particles on the sanding belt surface during the sanding process, and synchronously changes the sanding belt feed rate and the sanding down pressure according to the sanding belt wear amount and the workpiece morphology change.

[0016] Furthermore, the closed-loop PID adaptive adjustment system adopts an incremental PID control algorithm, using the deviation between the target grinding layer thickness and the actual grinding layer thickness as the control input, and the sanding contact pressure, feed speed, laser power, and sanding belt speed as the control output; the control cycle of the closed-loop PID adaptive adjustment system is 10ms to 50ms, the controllable adjustment range of the single grinding layer thickness is 0.01mm to 0.5mm, and the thickness control accuracy is less than or equal to ±0.05mm.

[0017] Furthermore, it also includes step S6, after continuously and adaptively grinding the workpiece to be ground to a constant thickness, automatically unloading the qualified workpiece, and the electronic control system stores each set of thickness parameters and process parameters to realize batch process traceability.

[0018] Furthermore, the dual-channel partitioned pulsed laser system is independently installed on a small translation slide, and the short-pulse ablation laser system and the long-pulse thermal softening laser system are independently adjusted to adjust their horizontal distance from the belt grinding zone.

[0019] Secondly, the present invention also provides a laser sanding composite grinding and grinding layer thickness adaptive adjustment device, comprising: The vision camera detection module is used to scan the surface contour and initial thickness of the workpiece to be polished, generate polishing motion data, and simultaneously collect the wear morphology of abrasive particles on the surface of the abrasive belt. Short-pulse ablation laser systems are used to scan and ablate the surface of workpieces to be polished, removing protruding defects and localized hard spots. The long-pulse thermal softening laser system is used to soften the substrate of the workpiece to be ground with low heat to reduce grinding resistance; the short-pulse ablation laser system and the long-pulse thermal softening laser system are respectively independently mounted on a small translation slide, and can be independently adjusted in terms of horizontal distance from the belt grinding zone. The mechanical sanding and polishing module is used to perform uniform and flexible sanding on the surface of workpieces after laser pretreatment. The electronic control system is communicatively connected to the vision camera detection module, the short-pulse ablation laser system, the long-pulse thermal softening laser system, and the mechanical sanding and polishing module. The electronic control system has a built-in closed-loop PID adaptive adjustment system, which is used to compare the polishing motion data with the target data in real time during the polishing process, and automatically fine-tune the laser power, laser softening area, feed depth, and sanding downward contact pressure when the tolerance range is exceeded.

[0020] Furthermore, the vision camera detection module includes a laser displacement sensor, a line scan camera, and a thickness test probe; the laser displacement sensor is used to collect workpiece surface contour data in real time, the line scan camera is used to acquire two-dimensional morphological images of the workpiece surface, and the thickness test probe is used to measure the reference thickness of the workpiece before grinding and the remaining thickness after grinding, and to calculate the thickness of the layer removed in a single grinding operation based on the reference thickness before grinding and the remaining thickness after grinding.

[0021] The beneficial effects of this invention are as follows: This invention offers the following technical advantages: Through a composite pretreatment using a dual-long-short-pulse dual-laser system, the short-pulse laser effectively removes hard oxide scale and localized hard spots from the surface, while the long-pulse laser softens the substrate with low heat to reduce grinding resistance, thus avoiding the problems of hot recasting and thermal deformation caused by continuous lasers. By employing online morphology detection, real-time acquisition of abrasive belt wear morphology, and real-time acquisition of workpiece thickness, combined with a closed-loop PID adaptive adjustment system, real-time detection and automatic fine-tuning of the grinding thickness are achieved. The controllable adjustment range of the single grinding layer thickness is 0.01mm to 0.5mm, with a thickness control accuracy of less than or equal to ±0.05mm. Furthermore, the design of independently mounting the dual-laser system on a translation slide allows for differentiated processing of different grinding allowance areas, significantly improving workpiece surface flatness, dimensional consistency, and processing yield. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of the laser sand grinding composite grinding and the adaptive adjustment method for grinding layer thickness of the present invention; Figure 2 This is a schematic diagram of the overall structure of the laser sanding composite grinding and grinding layer thickness adaptive adjustment device of the present invention. Detailed Implementation

[0023] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed 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 based on the above application content.

[0024] like Figure 1 As shown, the laser sanding composite grinding and the adaptive adjustment method for grinding layer thickness of the present invention specifically includes the following steps: Step S1. Preset the target data of the workpiece to be polished in the electronic control system. The target data includes the thickness of the polishing layer in a single pass, the allowable thickness tolerance, the laser power range, the belt speed and the initial contact pressure.

[0025] In this embodiment, the thickness of a single grinding layer is set according to the workpiece material and processing requirements, ranging from 0.01 mm to 0.5 mm. The allowable thickness tolerance is set according to the processing accuracy requirements, preferably ±0.05 mm. The laser power range is set according to the working range of the short-pulse ablation laser system and the long-pulse thermal softening laser system, respectively. The abrasive belt rotation speed is set according to the abrasive belt mesh size and the workpiece material. The initial contact pressure is set according to the workpiece material and the abrasive belt mesh size, ranging from 50 N to 200 N.

[0026] Step S2. The workpiece to be polished is transported to the processing station. The front surface contour and initial thickness of the workpiece to be polished are scanned by the vision camera detection module. Polishing motion data is generated based on the collected front surface contour and initial thickness. The polishing motion data includes the polishing motion trajectory and the polishing thickness data of the motion trajectory nodes.

[0027] In this embodiment, the vision camera detection module is the core detection unit of the invention, integrating multiple detection methods to achieve comprehensive perception of the workpiece surface condition. This module includes a laser displacement sensor, a line scan camera, and a thickness testing probe. The laser displacement sensor is used to acquire workpiece surface contour data in real time. Its working principle is based on laser triangulation, projecting a laser beam onto the workpiece surface and receiving the reflected light to calculate the height information of each point on the workpiece surface, thereby constructing a three-dimensional contour map of the workpiece surface. The line scan camera is used to acquire two-dimensional topographic images of the workpiece surface. Through high-speed line scan imaging technology, surface images are acquired line by line during workpiece movement, stitched together to form a complete surface topographic map, which can be used to identify surface defect types (such as oxide scale, cracks, pits, etc.) and their distribution locations. The thickness testing probe is used to measure the absolute thickness of the workpiece, employing contact or non-contact measurement methods, measuring the workpiece thickness before and after grinding, thereby accurately calculating the thickness of the layer removed in a single grinding operation.

[0028] In this embodiment, the vision camera detection module also incorporates a miniature beam splitter, which can simultaneously acquire the abrasive wear morphology of the abrasive belt surface during the sanding process. Its working principle involves introducing a beam splitter into the optical path of the vision camera, allowing the camera to observe both the workpiece surface and the abrasive belt surface through the reflected light path. Image analysis of the abrasive grain morphology on the abrasive belt surface can assess the wear state of the abrasive belt, including the degree of abrasive grain flattening, detachment, and clogging, providing data support for abrasive belt wear compensation strategies.

[0029] It should be noted that in this embodiment, the grinding motion trajectory can be optimized according to the undulation of the surface contour, with increased grinding for raised areas and reduced grinding for recessed areas.

[0030] Step S3. The workpiece to be polished is pre-treated by laser using a dual-channel partitioned pulsed laser system. First, the short-pulse ablation laser system of the dual-channel partitioned pulsed laser system removes the hard oxide scale on the surface of the workpiece according to the polishing motion trajectory. Then, the long-pulse thermal softening laser system of the dual-channel partitioned pulsed laser system is used to perform low-temperature softening on the substrate.

[0031] This embodiment employs a dual-channel partitioned pulsed laser system for laser pretreatment of the workpiece to be polished. It should be noted that this dual-channel partitioned pulsed laser system includes a short-pulse ablation laser system and a long-pulse thermal softening laser system. The short-pulse ablation laser system scans and ablates the workpiece surface, removing protruding defects, localized hard spots, and hard oxide scale. The short-pulse laser uses galvanometer scanning, and the scanning speed is calculated based on the laser repetition frequency and the single-pulse ablation diameter, ensuring that the overlap rate of adjacent pulses is not less than 50%. Then, the long-pulse thermal softening laser system performs low-temperature softening treatment on the ablated substrate material. The long-pulse laser also uses galvanometer scanning, with its scanning path parallel to and offset from the short-pulse laser's scanning path by a certain distance to ensure the uniformity of the softened area. Both laser systems automatically adjust the laser power and scanning speed based on the polishing thickness data at each node in the polishing motion data, achieving differentiated processing for each partitioned area.

[0032] The short-pulse ablation laser system employs an ultrashort-pulse laser with a wavelength of 1030 nm, a pulse width ranging from 200 fs (femtoseconds) to 100 ps (picoseconds), a power of 15 W to 60 W, a frequency of 200 kHz to 3 MHz, a single-pulse energy of 1 to 15 μJ, and a defocusing depth of -0.1 mm to 0.6 mm. Short-pulse lasers possess extremely short pulse widths and extremely high peak power densities. Their interaction mechanism with materials primarily involves multiphoton absorption and optical breakdown effects caused by avalanche ionization. When an ultrashort-pulse laser acts on the workpiece surface, laser energy is deposited on the material surface in a very short time, causing instantaneous vaporization or plasmaification of the material, achieving a so-called "cold processing" effect. This means that the heat-affected zone is extremely small during material removal, and there is no significant thermal damage to the surrounding substrate material. This characteristic makes short-pulse lasers particularly suitable for removing hard oxide scale, localized hard spots, and protruding defects from workpiece surfaces without causing thermal impact on the substrate material.

[0033] The long-pulse thermal softening laser system employs a long-pulse laser with a wavelength of 1064 nm, a pulse width ranging from 200 ns to 1000 ns, a power of 40 to 200 W, a frequency of 20 kHz to 500 kHz, a single-pulse energy of 0.2 to 1.5 mJ, and a defocusing amount of 0.4 mm to 1.2 mm. The pulse width of a long-pulse laser is significantly longer than that of a short-pulse laser, and its interaction mechanism with materials is primarily a photothermal effect. When a long-pulse laser acts on the workpiece substrate, the laser energy is absorbed by the material and converted into heat energy, causing the surface temperature of the material to rise and producing a localized thermal softening effect. By precisely controlling the laser power and the interaction time, the surface material of the workpiece can be softened below the phase transition temperature, reducing the yield strength and hardness of the material, thereby significantly reducing the grinding resistance of subsequent mechanical sanding. Compared with continuous lasers, long-pulse lasers achieve heat diffusion and cooling through pulse intervals, avoiding the formation of large-area high-temperature hot-recast layers and overall thermal expansion deformation, thus enabling effective control of subsequent sanding accuracy.

[0034] It should be noted that in this embodiment, the short-pulse ablation laser system and the long-pulse thermal softening laser system are independently mounted on a small translational slide. The two laser systems can be independently adjusted in terms of their horizontal distance from the belt grinding zone, rather than moving synchronously as a single laser head as in traditional methods. This independent adjustment design allows the system to perform differentiated processing based on the grinding allowance of different areas of the workpiece. For areas with large allowances, i.e., areas requiring significant grinding removal, the softening distance of the long-pulse thermal softening laser can be extended to increase the softening area. Simultaneously, both optical paths are fully open, meaning the short-pulse ablation laser and the long-pulse thermal softening laser operate simultaneously to maximize the pretreatment effect. For areas with minimal allowances, including hard oxide scale areas, raised defect areas, and localized hard spots, only the short-pulse ablation laser is activated for precise removal, avoiding excessive thermal impact from the long-pulse laser on these areas.

[0035] Step S4. The surface of the workpiece to be polished after laser pretreatment is uniformly and flexibly polished by the mechanical sanding module. At the same time, the wear morphology of the abrasive particles on the surface of the sanding belt is synchronously collected by the built-in micro-splitter optical path of the vision camera detection module, so as to adjust the sanding belt feed and sanding downward contact pressure in real time.

[0036] In this embodiment, the mechanical sanding and grinding module includes a sanding belt wheel, an annular sanding belt, a sanding floating seat, a variable frequency speed-regulating motor, and a shock-absorbing assembly. The sanding belt wheel is driven by the variable frequency speed-regulating motor, causing the annular sanding belt to rotate at high speed to grind the workpiece surface. The sanding belt rotates at high speed under the drive of the variable frequency speed-regulating motor, and the sanding floating seat provides flexible contact pressure through elastic elements (such as gas springs or hydraulic cylinders), allowing the sanding belt to adapt to the slight undulations of the workpiece surface and avoid localized over-grinding or under-grinding. The shock-absorbing assembly consists of a damper and elastic elements, configured to absorb vibrations generated during the sanding process and improve the surface quality. The variable frequency speed-regulating motor achieves stepless speed adjustment through an electronic control system. The speed adjustment range is set according to the required sanding belt linear speed, allowing the sanding belt linear speed to be continuously adjustable within the range of 5 m / s to 30 m / s. During the sanding process, the micro-splitter optical path built into the vision camera detection module synchronously collects abrasive wear morphology data on the sanding belt surface. The electrical control system synchronously adjusts the abrasive belt feed rate and abrasive contact pressure based on the abrasive belt wear and workpiece morphology changes. The abrasive belt grit is selected according to the workpiece material and surface quality requirements: 80# to 240# abrasive belts are used for roughing, 240# to 600# abrasive belts are used for semi-finishing, and 600# to 1200# abrasive belts are used for finishing.

[0037] Step S5. Compare the grinding motion data during the grinding process with the target data in real time. If the data exceeds the tolerance range, the laser power, laser softening area, feed depth and sanding pressure are automatically fine-tuned through the closed-loop PID adaptive adjustment system to achieve continuous adaptive constant thickness grinding.

[0038] In this embodiment, the vision camera detection module measures the remaining thickness of the workpiece after grinding using a thickness testing probe, and calculates the actual thickness of the layer removed in a single grinding pass. The actual grinding layer thickness is compared with the target grinding layer thickness. If the deviation exceeds the tolerance range, the closed-loop PID adaptive adjustment system employs an incremental PID control algorithm, using the deviation between the target and actual grinding layer thickness as the control input, and the sanding pressure, feed speed, laser power, and sanding belt speed as the control output. The control cycle of the closed-loop PID adaptive adjustment system is 10ms to 50ms, the controllable adjustment range of the single grinding layer thickness is 0.01mm to 0.5mm, and the thickness control accuracy is less than or equal to ±0.05mm. Specifically, when the actual grinding layer thickness is greater than the target value plus the tolerance, it indicates over-grinding; the system reduces the sanding pressure and laser power while increasing the feed speed. When the actual grinding layer thickness is less than the target value minus the tolerance, it indicates under-grinding; the system increases the sanding pressure and laser power while decreasing the feed speed. Constant thickness grinding is achieved through continuous adaptive adjustment.

[0039] Step S6. Finished Product Discharge and Data Storage: Qualified workpieces are automatically discharged. The electronic control system stores each set of thickness and process parameters, including workpiece number, grinding position coordinates, target thickness, actual thickness, laser power, abrasive belt speed, contact pressure, feed speed, and abrasive belt wear status, enabling batch process traceability. When the actual thickness at three or more consecutive measurement points continuously exceeds the tolerance range, the system triggers an alarm and suspends processing.

[0040] To better understand the technical solution of this embodiment, a copper-aluminum composite strip is used as the workpiece to be polished. The long-pulse thermal softening laser has a power of 100-120W, a frequency of 200kHz, a single-pulse energy of 1mJ, and a defocusing amount of 1mm. The short-pulse ablation laser has a power of 40-50W, a frequency of 800kHz, a single-pulse energy of 15uJ, and a defocusing amount of -0.3mm. A 320# abrasive belt is used. The preset target polishing layer thickness is 0.05mm, with a tolerance of ±0.05mm. An online laser displacement sensor collects the contour in real time, and a PID closed-loop system automatically adjusts the grinding pressure to 50-200N and the feed speed to 50-300mm / min. After laser pre-etching to remove surface oxide hard spots and softening the substrate, the finished polished layer has a uniform thickness, with no over- or under-grinding, and a surface roughness Ra≤0.8μm.

[0041] like Figure 2 As shown, this embodiment also provides a laser sanding composite grinding and grinding layer thickness adaptive adjustment device 200, including: The vision camera detection module 201 is used to scan the surface contour and initial thickness of the workpiece to be polished, generate polishing motion data, and simultaneously collect the wear morphology of abrasive particles on the surface of the abrasive belt. The short-pulse ablation laser system 202 is used to scan and ablate the surface of the workpiece to be polished, removing protruding defects and local hard spots. The long-pulse thermal softening laser system 203 is used to perform low-heat softening on the substrate of the workpiece to be ground in order to reduce grinding resistance; the short-pulse ablation laser system and the long-pulse thermal softening laser system are respectively independently installed on a small translation slide, and can be independently adjusted in terms of horizontal distance from the belt grinding area. Mechanical sanding and polishing module 204 is used to perform uniform and flexible sanding on the surface of a workpiece after laser pretreatment. The electronic control system 205 is communicatively connected to the vision camera detection module, the short-pulse ablation laser system, the long-pulse thermal softening laser system, and the mechanical sanding and polishing module. The electronic control system has a built-in closed-loop PID adaptive adjustment system, which is used to compare the polishing motion data with the target data in real time during the polishing process, and automatically fine-tune the laser power, laser softening area, feed depth, and sanding downward contact pressure when the tolerance range is exceeded.

[0042] In this embodiment, the vision camera detection module includes a laser displacement sensor, a line scan camera, and a thickness testing probe. The laser displacement sensor is used to acquire workpiece surface contour data in real time, the line scan camera is used to acquire two-dimensional topographic images of the workpiece surface, and the thickness testing probe is used to measure the reference thickness of the workpiece before grinding and the remaining thickness after grinding, and calculate the thickness of the layer removed in a single grinding operation based on the reference thickness before grinding and the remaining thickness after grinding. It should be noted that the modules or systems corresponding to the adaptive adjustment device in this embodiment correspond to the corresponding modules or systems in the aforementioned embodiments. For example: In this embodiment, the vision camera detection module 201 is the core detection unit of the invention, integrating multiple detection methods to achieve comprehensive perception of the workpiece surface condition. This module includes a laser displacement sensor, a line scan camera, and a thickness testing probe. The laser displacement sensor is used to acquire workpiece surface contour data in real time. Its working principle is based on laser triangulation, which projects a laser beam onto the workpiece surface and receives the reflected light to calculate the height information of each point on the workpiece surface, thereby constructing a three-dimensional contour map of the workpiece surface. The line scan camera is used to acquire two-dimensional topographic images of the workpiece surface. Through high-speed line scan imaging technology, surface images are acquired line by line during workpiece movement and stitched together to form a complete surface topographic map, which can be used to identify surface defect types (such as oxide scale, cracks, pits, etc.) and their distribution locations. The thickness testing probe is used to measure the absolute thickness of the workpiece, employing contact or non-contact measurement methods to measure the workpiece thickness before and after grinding, thereby accurately calculating the thickness of the layer removed in a single grinding operation.

[0043] The short-pulse ablation laser system 202 employs an ultrashort-pulse laser with a wavelength of 1030 nm, a pulse width ranging from 200 fs (femtoseconds) to 100 picoseconds (picoseconds), a power of 15 W to 60 W, a frequency of 200 kHz to 3 MHz, a single-pulse energy of 1 to 15 μJ, and a defocusing depth of -0.1 mm to 0.6 mm. Short-pulse lasers possess extremely short pulse widths and extremely high peak power densities. Their interaction mechanism with materials is primarily based on multiphoton absorption and optical breakdown effects caused by avalanche ionization. When the ultrashort-pulse laser acts on the workpiece surface, laser energy is deposited on the material surface in a very short time, causing the material to instantly vaporize or plasmaize, achieving the so-called "cold processing" effect. This means that the heat-affected zone is extremely small during material removal, and there is no significant thermal damage to the surrounding substrate material. This characteristic makes short-pulse lasers particularly suitable for removing hard oxide scale, localized hard spots, and protruding defects from workpiece surfaces without causing thermal impact on the substrate material.

[0044] The long-pulse thermal softening laser system 203 employs a long-pulse laser with a wavelength of 1064 nm, a pulse width ranging from 200 ns to 1000 ns, a power of 40 to 200 W, a frequency of 20 kHz to 500 kHz, a single-pulse energy of 0.2 to 1.5 mJ, and a defocusing amount of 0.4 mm to 1.2 mm. The pulse width of a long-pulse laser is significantly longer than that of a short-pulse laser, and its interaction mechanism with materials is primarily a photothermal effect. When a long-pulse laser acts on the workpiece substrate, the laser energy is absorbed by the material and converted into heat energy, causing the surface temperature of the material to rise and producing a localized thermal softening effect. By precisely controlling the laser power and the interaction time, the surface material of the workpiece can be softened below the phase transition temperature, reducing the yield strength and hardness of the material, thereby significantly reducing the grinding resistance of subsequent mechanical sanding. Compared with continuous lasers, long-pulse lasers achieve heat diffusion and cooling through pulse intervals, avoiding the formation of large-area high-temperature hot-recast layers and overall thermal expansion deformation, thus enabling effective control of subsequent sanding accuracy.

[0045] The mechanical sanding and grinding module 204 includes a sanding belt wheel, an annular sanding belt, a grinding floating seat, a variable frequency speed-regulating motor, and a shock-absorbing assembly. The sanding belt wheel is driven by the variable frequency speed-regulating motor, causing the annular sanding belt to rotate at high speed, grinding the workpiece surface. The sanding belt rotates at high speed under the drive of the variable frequency speed-regulating motor, and the grinding floating seat provides flexible contact pressure through elastic elements (such as gas springs or hydraulic cylinders), allowing the sanding belt to adapt to the slight undulations of the workpiece surface, avoiding localized over-grinding or under-grinding. The shock-absorbing assembly consists of dampers and elastic elements, configured to absorb vibrations generated during the sanding process, improving the surface quality. The variable frequency speed-regulating motor achieves stepless speed adjustment through an electronic control system. The speed adjustment range is set according to the required sanding belt linear speed, allowing the sanding belt linear speed to be continuously adjustable within the range of 5m / s to 30m / s.

[0046] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A laser-assisted sanding composite grinding method and an adaptive adjustment method for grinding layer thickness, characterized in that, Includes the following steps: Step S1. Preset the target data of the workpiece to be polished in the electronic control system. The target data includes the thickness of the polishing layer in a single pass, the allowable thickness tolerance, the laser power range, the belt speed and the initial contact pressure. Step S2. The workpiece to be polished is transported to the processing station. The front surface contour and initial thickness of the workpiece to be polished are scanned by the vision camera detection module. Polishing motion data is generated based on the collected front surface contour and initial thickness. The polishing motion data includes the polishing motion trajectory and the polishing thickness data of the motion trajectory nodes. Step S3. The workpiece to be polished is pre-treated by laser using a dual-channel partitioned pulsed laser system. First, the short-pulse ablation laser system of the dual-channel partitioned pulsed laser system removes the hard oxide scale on the surface of the workpiece according to the polishing motion trajectory. Then, the substrate is softened by low heat using the long-pulse thermal softening laser system of the dual-channel partitioned pulsed laser system. Step S4. The surface of the workpiece to be polished after laser pretreatment is uniformly and flexibly polished by the mechanical sand grinding module. At the same time, the wear morphology of the abrasive particles on the sand belt is synchronously collected by the built-in micro-splitter optical path of the vision camera detection module so as to adjust the sand belt feed and sand grinding contact pressure in real time. Step S5. Compare the grinding motion data during the grinding process with the target data in real time. If the data exceeds the tolerance range, the laser power, laser softening area, feed depth and sanding pressure are automatically fine-tuned through the closed-loop PID adaptive adjustment system to achieve continuous adaptive constant thickness grinding.

2. The laser-assisted sanding composite grinding and the method for adaptive adjustment of grinding layer thickness according to claim 1, characterized in that, The vision camera detection module includes a laser displacement sensor, a line scan camera, and a thickness test probe. The laser displacement sensor is used to collect the surface contour data of the workpiece to be polished in real time. The line scan camera is used to acquire a two-dimensional morphological image of the surface of the workpiece to be polished. The thickness test probe is used to measure the reference thickness of the workpiece before polishing and the remaining thickness after polishing, and to calculate the thickness of the layer removed in a single polishing operation based on the reference thickness before polishing and the remaining thickness after polishing.

3. The laser-assisted sanding composite grinding and the method for adaptive adjustment of grinding layer thickness according to claim 2, characterized in that, The short-pulse ablation laser system has a laser wavelength of 1030 nm, a pulse width of 200 fs to 100 ps, ​​a power of 15 W to 60 W, a frequency of 200 kHz to 3 MHz, a single pulse energy of 1 to 15 μJ, and a defocusing amount of -0.1 mm to 0.6 mm; the long-pulse thermal softening laser system has a laser wavelength of 1064 nm, a pulse width of 200 ns to 1000 ns, a power of 40 to 200 W, a frequency of 20 kHz to 500 kHz, a single pulse energy of 0.2 to 1.5 mJ, and a defocusing amount of 0.4 mm to 1.2 mm.

4. The laser-assisted sanding composite grinding and the adaptive adjustment method for grinding layer thickness according to claim 3, characterized in that, The step of using a dual-channel partitioned pulsed laser system to perform laser pretreatment on the workpiece to be polished further includes partitioning the workpiece according to the polishing allowance of different areas on the surface of the workpiece. For areas with large allowance, the softening distance of the long-pulse thermal softening laser is extended while the short-pulse ablation laser and the long-pulse thermal softening laser are turned on simultaneously. For areas with small allowance, only the short-pulse ablation laser is turned on. The small allowance areas include hard oxide scale areas, protruding defect areas, and local hard spot areas.

5. The laser abrasive grinding composite grinding and the method for adaptive adjustment of grinding layer thickness according to claim 4, characterized in that, The mechanical sanding and polishing module includes a sanding belt wheel, an annular sanding belt, a sanding floating seat, a variable frequency speed control motor, and a buffer and shock absorption assembly; the sanding belt has a mesh size of 80# to 1200#; the vision camera detection module has a built-in miniature beam splitter, which synchronously collects the wear morphology of the abrasive particles on the surface of the sanding belt during the sanding process, and synchronously changes the sanding belt feed rate and the sanding downward contact pressure according to the amount of sanding belt wear and the changes in workpiece morphology.

6. The laser sanding composite grinding and grinding layer thickness adaptive adjustment method according to claim 1, characterized in that, The closed-loop PID adaptive adjustment system adopts an incremental PID control algorithm, using the deviation between the target grinding layer thickness and the actual grinding layer thickness as the control input, and the sanding contact pressure, feed speed, laser power, and sanding belt speed as the control output. The control cycle of the closed-loop PID adaptive adjustment system is 10ms to 50ms, the controllable adjustment range of the single grinding layer thickness is 0.01mm to 0.5mm, and the thickness control accuracy is less than or equal to ±0.05mm.

7. The laser sanding composite grinding and grinding layer thickness adaptive adjustment method according to claim 1, characterized in that, It also includes step S6, which involves continuously and adaptively grinding the workpiece to be ground to a constant thickness, automatically unloading the qualified workpiece, and storing each set of thickness parameters and process parameters in the electronic control system to achieve batch process traceability.

8. The laser sanding composite grinding and grinding layer thickness adaptive adjustment method according to claim 3, characterized in that, The dual-channel partitioned pulsed laser system is independently installed on a small translation slide, and the short-pulse ablation laser system and the long-pulse thermal softening laser system are independently adjusted to adjust their horizontal distance from the belt grinding zone.

9. A laser-assisted sanding composite grinding and grinding layer thickness adaptive adjustment device, characterized in that, include: The vision camera detection module is used to scan the surface contour and initial thickness of the workpiece to be polished, generate polishing motion data, and simultaneously collect the wear morphology of abrasive particles on the surface of the abrasive belt. Short-pulse ablation laser systems are used to scan and ablate the surface of workpieces to be polished, removing protruding defects and localized hard spots. The long-pulse thermal softening laser system is used to soften the substrate of the workpiece to be ground with low heat to reduce grinding resistance; the short-pulse ablation laser system and the long-pulse thermal softening laser system are respectively independently mounted on a small translation slide, and can be independently adjusted in terms of horizontal distance from the belt grinding zone. Mechanical sanding and polishing module, used to perform uniform and flexible sanding on the surface of workpieces after laser pretreatment; The electronic control system is communicatively connected to the vision camera detection module, the short-pulse ablation laser system, the long-pulse thermal softening laser system, and the mechanical sanding and polishing module. The electronic control system has a built-in closed-loop PID adaptive adjustment system, which is used to compare the polishing motion data with the target data in real time during the polishing process, and automatically fine-tune the laser power, laser softening area, feed depth, and sanding downward contact pressure when the tolerance range is exceeded.

10. The laser sanding composite grinding and grinding layer thickness adaptive adjustment device according to claim 9, characterized in that, The vision camera detection module includes a laser displacement sensor, a line scan camera, and a thickness test probe. The laser displacement sensor is used to collect workpiece surface contour data in real time, the line scan camera is used to acquire two-dimensional morphological images of the workpiece surface, and the thickness test probe is used to measure the reference thickness of the workpiece before grinding and the remaining thickness after grinding, and to calculate the thickness of the layer removed in a single grinding operation based on the reference thickness before grinding and the remaining thickness after grinding.

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