Adaptive focusing laser cutting device and control method thereof
Patent Information
- Application Number
- CN202611085255.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-21
- Publication Date
- 2026-11-03
AI Technical Summary
Traditional laser cutting equipment cannot adapt to the physical undulations and heat accumulation differences of the sheet material, resulting in inconsistent cutting quality and problems such as incomplete cutting, burnt edges, or excessively wide kerfs.
An adaptive focusing laser cutting control method is adopted, which adjusts the focus position through real-time ranging and closed-loop calculation, and combines the speed curvature linkage continuous focusing function and lens thermal drift compensation to achieve dynamic focus adjustment.
It improves the consistency of cutting quality, prevents overheating and through-cutting problems, ensures the stability and smoothness of the focal point, and reduces the risk of parameter coupling during the debugging process.
Smart Images
Figure CN123025013A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of laser cutting technology, and in particular to an adaptive focusing laser cutting device and its control method. Background Technology
[0002] Laser cutting is a technique that uses a high-power-density laser beam to irradiate the material being processed, causing it to rapidly melt, vaporize, or reach its ignition point. Simultaneously, a high-speed gas stream coaxial with the laser beam blows away the molten material, thus achieving the cutting process. During laser cutting, the focal point is a key parameter determining the cutting quality indicators such as kerf width, surface roughness, the size of the heat-affected zone, and whether the cut is complete.
[0003] Traditional laser cutting equipment typically uses a fixed focal length or manual focusing method, determining the focal height before cutting by manual trial cuts or with the aid of a focusing platform. This approach has the following drawbacks in practical applications: First, it cannot adapt to the physical undulations of the board itself. Non-metallic boards often have warping, thickness tolerance, and placement height differences. During the cutting process, the fixed focus will deviate from the ideal position due to changes in the height of the board surface, resulting in defects such as incomplete cutting, burnt edges, or excessively wide cuts.
[0004] Second, it cannot compensate for the differences in heat accumulation caused by different motion trajectories. When cutting different graphic contours of the same plate, straight sections usually pass through at a higher speed and have less heat accumulation; while in areas such as arcs and sharp corners, the cutting head decelerates, causing the laser to act at the same position for a longer time, and the heat accumulation increases sharply. The fixed focus cannot be dynamically adjusted according to this difference, which can easily cause problems such as slag buildup in high-speed sections and overheating in low-speed sections. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides the following technical solution: An adaptive focusing laser cutting control method includes the following steps: S1. The laser distance sensor acquires the measurement distance D between itself and the upper surface of the processed material in real time. meas In conjunction with the nominal focal length f0 of the focusing lens of the laser cutting head and the pre-calibrated position grid geometric compensation amount Obtain the reference focus height ; S2. Real-time reading of the instantaneous linear velocity v of the cutting head, the radius of curvature R of the current motion trajectory, the current continuous processing time t, the current laser output power P, and the focal length compensation coefficient Cmat corresponding to the current effective processing material; S3. Input the instantaneous linear velocity v and the radius of curvature R into the preset velocity-curvature linkage continuous focusing function to calculate the dynamic focus compensation value ΔZdyn. The function outputs the compensation value monotonically and continuously according to v and R. When the speed is low or the radius of curvature is small, the output is a positive value to move the focus down to increase the spot size, reduce the power density, and prevent overburning. When the speed is high and the radius of curvature is large, the output is a negative value to move the focus up to increase the energy density and ensure through-cutting. S4. Combine the reference focusing height, process dynamic focus compensation value, focal length compensation value, and lens thermally induced focus drift compensation value based on the current continuous processing time t and laser output power P. By superimposing the data, the target focal position can be obtained. ; S5 drives the Z-axis lifting assembly to adjust the focus to the target focus position in real time.
[0006] As an improvement to the above technical solution, the velocity curvature linkage continuous focusing function in step S3 is calculated as follows: First, the radius of curvature R is mapped through a mapping function. It is converted into a speed correction factor, where R0 is a reference radius of curvature preset according to the processed material; Secondly, calculate the equivalent speed. vbase is the preset minimum base speed; at last, The dynamic focus compensation value of the process is calculated according to the following conditions: Where Vmax is the maximum operating speed of the machine tool, k is the curve steepness coefficient, v0 is the preset compensation zero-point equivalent speed, and Dmax is the maximum compensation amplitude.
[0007] As an improvement to the above technical solution, the lens thermal-induced focus drift compensation value in step S4 Initialized to zero at the start of each cutting task, the rate of change thereafter is described by the following differential equation: ;in τ is the maximum drift under full-power steady-state conditions, τ is the thermal time constant of the lens, and Pmax is the maximum output power of the laser.
[0008] As an improvement to the above technical solution, the multi-material adaptive focusing database stores at least the focal length compensation coefficients for acrylic, wood, leather, and foam.
[0009] As an improvement to the above technical solution, it also includes: the pre-calibrated position grid geometric compensation amount mentioned in step S1. The process dynamic focus compensation value ΔZdyn is obtained by bilinear interpolation from the X / Y grid compensation table pre-stored in the controller. The calibration of this geometric compensation amount is performed independently.
[0010] As an improvement to the above technical solution, it also includes an automatic focus calibration step performed during the initialization phase: driving the Z-axis lifting assembly to make the measured value of the laser rangefinder equal to the focal length f0 of the focusing lens, and recording this position as the focus origin; the pre-calibrated position grid geometric compensation amount It is a static error compensation table for the Z-axis obtained by full-frame grid calibration based on the focusing origin.
[0011] As an improvement to the above technical solution, the radius of curvature R is calculated and provided in real time by the interpolator of the X / Y axis motion mechanism through the vector cross product method of adjacent interpolation points, and the instantaneous linear velocity v, the current coordinate (x,y) and the current laser output power P are output synchronously by the same interpolator.
[0012] An adaptive focusing laser cutting machine includes a frame, an X-axis motion mechanism, a Y-axis motion mechanism, a Z-axis lifting assembly, a laser cutting head, a laser range sensor, and a controller. The laser cutting head has a focusing lens, the laser range sensor is rigidly fixed to the laser cutting head and moves synchronously with it, and the controller is configured to execute the adaptive focusing laser cutting control method described above.
[0013] The beneficial effects of this invention are: By using real-time ranging and closed-loop calculation of the reference focus height, the focus can follow the actual undulations of the board surface, eliminating the adverse effects of board warping and placement height differences on focus accuracy and improving the consistency of the whole board cutting. By using a speed-curvature linkage continuous focusing function, automatic differential focusing is achieved on different cutting trajectories of the same material. In high-speed straight sections, the focus is moved upward to increase energy density and ensure cut-through; in low-speed circular arc and sharp corner sections, the focus is moved downward to increase the light spot, reduce power density, and prevent overheating. This fundamentally solves the technical defect that traditional fixed focus cannot adapt to dynamic trajectory changes. The introduction of the concept of equivalent speed and the exponential curvature correction factor makes the compensation under different curvature radii continuous and smooth; at the same time, the minimum reference speed protection mechanism avoids the overcompensation problem caused by the low equivalent speed at sharp turns, thus ensuring the stability of Z-axis motion. By independently calibrating and linearly superimposing machine tool geometric error compensation and process dynamic compensation, the compensation amounts from two different physical sources can be calibrated and maintained separately, reducing the risk of parameter coupling during the debugging process. A first-order dynamic model is used to independently compensate for the thermally induced focus drift of the lens. This model can accurately describe the drift state when the power changes and the drift fall process during the shutdown and cooling stage. The compensation amount is scaled according to the power ratio, avoiding the double counting problem of process dynamic compensation and ensuring the focus stability during long-term processing. Attached Figure Description
[0014] Figure 1 This is a schematic diagram of the overall structure of the present invention. Detailed Implementation
[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0016] Example 1 See Figure 1 An adaptive focusing laser cutting machine includes a frame 1, an X-axis motion mechanism 2, a Y-axis motion mechanism 3, a Z-axis lifting assembly 4, a laser cutting head 5, a laser rangefinder 6, and a controller. The laser cutting head 5 has a built-in focusing lens with a nominal focal length f0 = 50.8 mm. The laser rangefinder 6 is a triangulation laser displacement sensor, rigidly fixed to the side of the cutting head, with the ranging spot coinciding with the cutting spot and a sampling frequency of 200 Hz. The Z-axis lifting assembly 4 is driven by a linear motor and equipped with an absolute grating ruler, with a closed-loop bandwidth of 50 Hz and a control cycle of 20 ms. The controller contains non-volatile memory that stores an X / Y grid compensation table and a multi-material adaptive focusing database.
[0017] The working process of this cutting machine embodies all the steps of the adaptive focusing laser cutting control method of the present invention, as detailed below: Step S1: Obtaining the reference focus height First, automatic focusing calibration is performed. The controller drives the Z-axis lifting assembly 4 to make the measured value of the laser rangefinder 6 equal to the nominal focal length f0 of the focusing lens. This Z-axis position is recorded as the focusing origin. This calibration process automatically eliminates fixed offsets such as sensor mounting bias and lens mounting reference surface deviation. Then, a laser interferometer is used to perform grid calibration on the entire machine tool surface to obtain the X / Y grid compensation table δ. pos (x, y) is stored in non-volatile memory. After the cutting begins, within each 20 ms control cycle, the mean filter is applied to four samples of the sensor's 200 Hz output to obtain the effective measurement distance D. meas Simultaneously, based on the current position coordinates (x, y), bilinear interpolation is performed in the X / Y grid compensation table to obtain the geometric compensation amount δ. pos(x, y), the reference focus height is calculated using the formula The calculation of the reference height, the calibration of this geometric compensation amount and the process dynamic compensation can be carried out independently without interference; Step S2: Reading motion and material parameters The interpolator of the X / Y axis motion mechanism calculates the radius of curvature R of the current trajectory in real time in each interpolation cycle (1 ms) based on the vector cross product method of three adjacent interpolation points. At the same time, it outputs the instantaneous linear velocity v, the current coordinate (x,y), the current laser output power P, and the continuous processing time t of this cutting task. The controller reads the interpolator's shared memory in batches and performs median filtering every 20 ms to obtain effective motion parameters. In the machining process, material selection instructions are pre-inserted at the starting positions of different material regions. When the controller executes such instructions, it immediately retrieves the parameter set corresponding to the current material thickness combination from the built-in multi-material adaptive focusing database, including: focal length compensation value C. mat Reference radius of curvature R0, maximum compensation amplitude D max Compensation zero-point equivalent velocity v0, curve steepness coefficient k, minimum reference velocity v base Maximum steady-state thermal drift at full power The database stores at least the corresponding parameters for acrylic, wood, leather, and foam at different thicknesses, and the thermal time constant τ of the lens. Each parameter is pre-calibrated through cutting experiments. R0 is generally set to 2 to 5 times the minimum radius of curvature in the common cutting pattern of the material. Step S3: Calculation of process dynamic focus compensation value The controller executes a speed-curvature linked continuous focusing function, and the calculation process is as follows: First, calculate the velocity correction factor based on the current radius of curvature R and the reference radius of curvature R0: ; The function α→0 as R→0 and α→1 as R→∞, and its first and second derivatives are continuous throughout its domain; then, the equivalent velocity is calculated. ,: v is the equivalent velocity (m / min); v is the instantaneous linear velocity (m / min); v base For the preset minimum reference speed (m / min), a minimum reference speed v is introduced. base It can be guaranteed that the equivalent speed will not be less than v when the radius of curvature approaches zero (sharp turn). base To avoid the compensation value being locked in the maximum downward shift state due to excessively low equivalent speed, and to prevent overcompensation, Finally, the equivalent velocity is substituted into the S-shaped function to calculate the dynamic focus compensation value of the process: ; Among them, D max v* is the maximum compensation amplitude (mm); v* is the equivalent velocity (m / min); v0 is the preset compensation zero-point equivalent velocity (m / min), when v*=v0 =0; V max The maximum operating speed of the machine tool is (m / min); k is the curve steepness coefficient. The larger the value of k, the steeper the transition of the S-curve near the zero point. The range of this function is (-D). max +D max It is continuously monotonic throughout the entire velocity range, with no hard clamping points. Approaching v base Time ΔZ dyn Approaching +D max This lowers the focal point to increase the beam size, reduce power density, and prevent overheating; Approaching V max Time ΔZ dyn Approaching-D max This causes the focal point to shift upwards, increasing energy density and ensuring complete penetration. Step S4: Multi-source compensation superposition and thermal drift compensation The lens expands thermally after absorbing laser energy, causing the focal point to drift along the optical axis. This invention employs a first-order dynamic model to independently compensate for this thermal drift, unlike process dynamic compensation. The thermal drift compensation value ΔZ is set at the start of each cutting task. T Initialize to zero. Thereafter, for each control cycle, update according to the following recursive formula:
[0018] The thermal drift compensation value (mm) for the kth control cycle; The compensation value (mm) for the previous cycle; T ctrl To control the period (s), in this embodiment, T ctrl =0.02s; τ is the thermal time constant of the lens (s); P represents the maximum thermal drift (mm) under full-power steady-state conditions; P represents the current laser output power (W); P max The maximum output power of the laser (W); The model has the following characteristics: in steady state, the compensation amount scales proportionally to the power, and the drift is halved when the power is halved; when the power changes abruptly, it smoothly approaches the new steady state with a time constant τ to avoid instantaneous jumps; when the machine is shut down for cooling, the compensation amount automatically decreases exponentially. The final target focus position is obtained by linearly superimposing the compensation terms:
[0019] Among them, Z targetZ represents the target focal point position (mm). base Reference focusing height (mm); The dynamic focus compensation value for the process (mm); This is the focal length compensation value (mm). This is the thermal drift compensation value (mm) at the current moment; Step S5: Z-axis synchronous execution The laser rangefinder has a sampling frequency of 200 Hz and a control cycle of 20 ms. Both are aligned via a hardware synchronization trigger signal, ensuring that the D signal used in each control cycle is consistent. meas This is the latest sampled value. The controller calculates Z. target Subsequently, position commands are sent to the Z-axis servo drive via the EtherCAT bus. The 50 Hz closed-loop bandwidth matches the 20 ms control cycle, and the command update frequency is coordinated with the mechanical response time, avoiding command accumulation and overshoot. The grating ruler provides real-time feedback on the actual position, forming a full closed-loop control. The above steps are repeated in each control cycle to achieve real-time adaptive adjustment of the focal position throughout the entire range.
[0020] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.
Claims
1. An adaptive focusing laser cutting control method, characterized in that, Includes the following steps: S1. The laser distance sensor acquires the measurement distance D between itself and the upper surface of the processed material in real time. meas In conjunction with the nominal focal length f0 of the focusing lens of the laser cutting head and the pre-calibrated position grid geometric compensation amount Obtain the reference focus height ; S2. Real-time reading of the cutting head's instantaneous linear velocity v, the radius of curvature R of the current motion trajectory, the current continuous processing time t, the current laser output power P, and the focal length compensation coefficient C corresponding to the current effective processing material. mat ; S3. Input the instantaneous linear velocity v and radius of curvature R into the preset velocity-curvature linkage continuous focusing function, and calculate the dynamic focus compensation value ΔZ. dyn The function outputs compensation values monotonically and continuously based on v and R. When the speed is low or the radius of curvature is small, it outputs positive values to shift the focus downward to increase the spot size, reduce the power density, and prevent overheating. When the speed is high and the radius of curvature is large, it outputs negative values to shift upward to increase the energy density and ensure penetration. S4. Combine the reference focusing height, process dynamic focus compensation value, focal length compensation value, and lens thermally induced focus drift compensation value based on the current continuous processing time t and laser output power P. By superimposing the data, the target focal position can be obtained. ; S5 drives the Z-axis lifting assembly to adjust the focus to the target focus position in real time.
2. The adaptive focusing laser cutting control method according to claim 1, characterized in that: The velocity curvature linkage continuous focusing function mentioned in step S3 is calculated as follows: First, the radius of curvature R is mapped through a mapping function. The velocity is converted into a velocity correction factor, where R0 is a reference radius of curvature preset according to the processed material; secondly, the equivalent velocity is calculated. ;v base The preset minimum reference speed; finally, The dynamic focus compensation value of the process is calculated according to the following conditions: ； Among them, V max Where k is the maximum operating speed of the machine tool, v0 is the curve steepness coefficient, and D is the preset compensation zero-point equivalent speed. max This represents the maximum compensation amplitude.
3. The adaptive focusing laser cutting control method according to claim 1, characterized in that: The lens thermally induced focus drift compensation value mentioned in step S4 Initialized to zero at the start of each cutting task, the rate of change thereafter is described by the following differential equation: ;in P represents the maximum drift under full-power steady-state conditions, τ is the lens thermal time constant, and P max This represents the maximum output power of the laser.
4. The adaptive focusing laser cutting control method according to claim 2, characterized in that: The multi-material adaptive focusing database stores at least the focal length compensation coefficients for acrylic, wood, leather, and foam.
5. The adaptive focusing laser cutting control method according to claim 1, characterized in that: Also includes: The pre-calibrated position mesh geometric compensation amount mentioned in step S1 The process dynamic focus compensation value ΔZ is obtained by bilinear interpolation from the X / Y grid compensation table pre-stored in the controller. dyn The calibration of the geometric compensation amount and the calibration of the geometric compensation amount are performed independently.
6. The adaptive focusing laser cutting control method according to claim 1, characterized in that: It also includes an automatic focus calibration step performed during the initialization phase: driving the Z-axis lifting assembly to make the measured value of the laser rangefinder equal to the focal length f0 of the focusing lens, and recording this position as the focus origin; the pre-calibrated position grid geometric compensation amount It is a static error compensation table for the Z-axis obtained by full-frame grid calibration based on the focusing origin.
7. The adaptive focusing laser cutting control method according to claim 1, characterized in that: The radius of curvature R is calculated and provided in real time by the interpolator of the X / Y axis motion mechanism through the vector cross product method of adjacent interpolation points. The instantaneous linear velocity v, the current coordinate (x,y) and the current laser output power P are output synchronously by the same interpolator.
8. An adaptive focusing laser cutting machine, comprising a frame, an X-axis motion mechanism, a Y-axis motion mechanism, a Z-axis lifting assembly, a laser cutting head, a laser rangefinder sensor, and a controller, wherein the laser cutting head has a focusing lens, and the laser rangefinder sensor is rigidly fixed to the laser cutting head and moves synchronously with it, characterized in that... The controller is configured to perform the adaptive focusing laser cutting control method as described in any one of claims 17.