A device and method for laser precision machining

Abstract

The present invention discloses a device for laser precision machining, comprising a photoelectric sensor array frame, a laser head is arranged at the center of the photoelectric sensor array frame, a processing platform is arranged directly below the laser head, a processing workpiece is arranged on the processing platform, a laser beam emitted by the laser head through a laser light outlet is vertically irradiated onto the processing workpiece, the laser beam ablates the processing workpiece to generate a plasma radiation light signal; a three-degree-of-freedom translation stage is arranged below the processing platform. The present invention also discloses a processing method for a device for laser precision machining, and the present invention solves the problem in the current industry that the laser focus position cannot be automatically and accurately followed.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser processing, and relates to a device for laser precision processing. The present invention also relates to a processing method of the device. Background Art

[0002] In recent years, high-power lasers have been widely used in special processing industries due to their many excellent properties. With the development of society and technological progress, the market and customers have put forward higher requirements for the precision of high-power laser processing. The precision of high-power laser processing is closely related to the position of the focus of the high-power laser. When a high-power laser beam is used to perform processing operations such as cutting / engraving / welding on a metal workpiece, keeping the surface of the workpiece to be processed always in the focal plane of the laser beam (referred to as "follow focus") is a key technology to ensure processing accuracy. It should be noted that the "focus" mentioned in the present invention is more accurately the optimal ablation position point of the laser for the processed material, which refers to a certain position away from the laser head with the best ablation depth and effect, rather than a focus in a purely optical sense.

[0003] Existing focus-following methods can be divided into modeling method and distance measurement method according to their working principles. The modeling method calculates the preset value of the stage lifting based on the model of the workpiece to be processed, so this method cannot adapt to the workpiece size tolerance; the distance measurement method is currently the most commonly used, and it is based on the principle of capacitance or laser triangulation to keep the distance between the focal plane and the surface to be processed unchanged, so this method is not suitable for surfaces with large curvature. The above methods are all based on the premise that the focal length of the laser lens group remains unchanged, and ignore the errors caused by the "thermal lens" effect of the strong laser, so they cannot adapt to the laser power regulation that needs to be constantly changed during the processing process. Summary of the invention

[0004] The purpose of the present invention is to provide a device for laser precision machining, which solves the problem in the current industry that the laser focus position cannot be automatically and accurately followed.

[0005] The object of the present invention is also to provide a processing method of a device for laser precision processing.

[0006] The technical solution adopted by the present invention is a device for laser precision processing, including a photoelectric sensor array frame, a laser head is arranged at the center of the photoelectric sensor array frame, a processing platform is arranged directly below the laser head, a processing workpiece is arranged on the processing platform, a laser beam emitted by the laser head through a laser light outlet is vertically irradiated onto the processing workpiece, and the laser beam ablates the processing workpiece to generate a plasma radiation light signal; a three-degree-of-freedom translation stage is arranged below the processing platform.

[0007] The first technical solution adopted by the present invention is also characterized in that:

[0008] The photoelectric sensor array frame includes a circular frame, which is evenly divided into four arc frames. Two arc frames located on the same diagonal line are respectively provided with a wide bandgap ultraviolet sensor and a silicon photoelectric sensor. A camera is provided on the side of the frame facing the workpiece, and the camera, the wide bandgap ultraviolet sensor and the silicon photoelectric sensor are located on the same side of the frame; the wide bandgap ultraviolet sensor and the silicon photoelectric sensor are respectively connected to an adder, an integrator, an ADC processor and a microcontroller in sequence, and the microcontroller is also connected to the camera.

[0009] Four grooves are evenly arranged on the circular frame, and the four grooves divide the circular frame into four arc frames.

[0010] The laser head is connected to the frame body via four bolts on all sides, and the four bolts are embedded in the four grooves.

[0011] Pressure buffer pads are provided at the contact points between the four bolts and the laser head.

[0012] The second technical solution adopted by the present invention is: a processing method of a device for laser precision processing, which specifically includes the following steps:

[0013] Step 1, drive the processing platform downward to the lowest position of the processing platform through the three-degree-of-freedom translation stage, fix the laser head at the center of the photoelectric sensor array frame, set the expected value of the wide bandgap ultraviolet sensor to collect data during the processing as Ex1, the allowable error as Err1, the expected geometric size of the laser spot photographed by the camera as R, the minimum step length in the X direction during processing as Dx, and the minimum step length in the Z direction as Dz; set the minimum signal value of the wide bandgap ultraviolet sensor to pmin, the minimum signal value of the silicon photoelectric sensor to smin, and the maximum moving length of the processing platform along the positive direction of the z axis to L during processing;

[0014] Step 2: The laser head emits a laser beam through the laser light outlet to irradiate the workpiece, and the laser beam ablates the workpiece to generate a plasma radiation visible light signal and a plasma radiation ultraviolet light signal. The camera captures the laser spot on the surface of the workpiece, the silicon photoelectric sensor collects the plasma radiation visible light signal, and the wide bandgap ultraviolet sensor collects the plasma radiation ultraviolet light signal and sends them to the microcontroller. The processing platform moves upward by L, then stops and turns to move downward.

[0015] Step 3, laser beam ablation processing workpiece, wide bandgap ultraviolet sensor collects plasma radiation ultraviolet light signal during processing, plasma radiation ultraviolet light signal passes through adder, integrator, ADC processor in turn to obtain current plasma ultraviolet light radiation value Lnow, and sends it to microcontroller 20, if |Lnow – Ex1|≤ Err1, processing platform stops descending; if |Lnow – Ex1|>Err1, processing platform continues to descend;

[0016] Step 4, perform real-time focus tracking on the workpiece 5 during the machining process;

[0017] Step 5, repeat Step 4 until the machining is completed, turn off the laser, and the device returns to the starting point.

[0018] The characteristics of the second technical solution of the present invention also lie in:

[0019] The specific process of Step 4 is as follows:

[0020] 4.1, the laser beam processes the workpiece, the three-degree-of-freedom translation stage steps in the X direction with a displacement Dx according to the machining requirements, the wide-bandgap ultraviolet sensor collects the ultraviolet light signal of the plasma radiation during the machining process, and the ultraviolet light signal of the plasma radiation sequentially passes through the adder, integrator, and ADC processor to obtain the current plasma ultraviolet light radiation value Lnow, which is sent to the microcontroller 20. If |Lnow – Ex1| ≤ Err1, repeat Step 4.1; if |Lnow – Ex1| > Err1, execute Step 4.2.

[0021] 4.2, the microcontroller controls the machining platform to displace a distance Dz in the positive z-axis direction. If |Lnow – Ex1| gradually decreases, the machining platform displaces Dz in the positive z-axis direction; if |Lnow – Ex1| does not decrease, the machining platform displaces Dz in the negative z-axis direction, and repeat Step 4.2 until |Lnow – Ex1| ≤ Err1; if Lnow < pmin, execute Step 4.3.

[0022] 4.3, select and turn on the silicon photoelectric sensor, collect the ultraviolet light radiation signal Lnow generated by ablation at this time; adjust the height of the machining platform to make Lnow > pmin, turn off the silicon photoelectric sensor, and execute Step 4.2. If Lnow < smin, execute Step 4.4;

[0023] 4.4, use the camera 27 to transmit the image data back to the microcontroller 20, judge the geometric size of the laser spot, adjust the movement of the machining platform to make the geometric size of the laser spot equal to R, and execute Step 4.3.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. The device for laser precision machining of the present invention utilizes the solar-blind characteristics of the wide-bandgap photoelectric sensor on the photoelectric sensor array frame device to respond to the ultraviolet component of the plasma generated by laser ablation, processes the measured signal through an integral adder circuit, and records and processes the plasma radiation intensity value, thereby achieving the purpose of precise focusing according to the relationship between the intensity value and the defocus amount. The system can adapt to changes in laser power, workpiece tolerance, temperature changes, ambient light changes, and low-frequency vibrations, and can be used for precise focusing. The system of the present invention has the advantages of high precision and high adaptability.

[0026] 2. The present invention provides a processing method for a device for laser precision processing. Based on the strong negative correlation between the intensity of the ultraviolet component of plasma radiation during laser ablation of a plate and the defocus amount, a photoelectric sensor is used to collect the intensity values ​​at different positions and to follow the focal position of the laser in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a device for laser precision machining of the present invention;

[0028] Figure 2 It is a bottom view of a photoelectric sensor array frame in a device for laser precision machining of the present invention;

[0029] Figure 3 It is a radiation signal processing frame in a device for laser precision machining of the present invention;

[0030] Figure 4 It is a structural schematic diagram of a three-degree-of-freedom translation stage in a device for laser precision machining of the present invention;

[0031] Figure 5 This is a view obtained by processing an embodiment of a processing method of a device for laser precision processing of the present invention.

[0032] 1. Laser head, 2. Laser light outlet, 3. Laser beam, 4. Processing platform, 5. Processing workpiece, 6. Plasma, 8. Bolt, 9. Pressure buffer pad, 10. Photoelectric sensor array frame, 12. Wide bandgap ultraviolet sensor, 15. Silicon photoelectric sensor, 17. Adder, 18. Integrator, 19. ADC processor, 20. Microcontroller, 22. Power signal bus;

[0033] 23. Three-degree-of-freedom translation platform, 23-1. X-direction displacement platform, 23-2. Z-direction displacement platform, 23-3. Y-direction displacement platform;

[0034] 24. Frame, 27. Camera. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] The present invention provides a device for laser precision machining, such as Figure 1~2 As shown, it includes a photoelectric sensor array frame 10, a laser head 1 is arranged at the center of the photoelectric sensor array frame 10, a processing platform 4 is arranged directly below the laser head 1, and a processing workpiece 5 is arranged on the processing platform 4. The laser head 1 emits a laser beam 3 through a laser light outlet 2 to irradiate the processing workpiece 5, and the laser beam 3 ablates the processing workpiece 5 to generate plasma 6 to radiate light signals.

[0037] The photoelectric sensor array frame 10 includes a circular frame 24, which is evenly divided into four arc frames. Two arc frames located on the same diagonal line are respectively provided with a wide bandgap ultraviolet sensor 12 and a silicon photoelectric sensor 15. A camera 27 is provided on the side of the frame 24 facing the workpiece. The camera 27, the wide bandgap ultraviolet sensor 12 and the silicon photoelectric sensor 15 are located on the same side of the frame; Figure 3 As shown, the wide bandgap ultraviolet sensor 12 and the silicon photoelectric sensor 15 are respectively connected to an adder 17 , an integrator 18 , an ADC processor 19 and a microcontroller 20 in sequence, and the microcontroller 20 is also connected to a camera 27 .

[0038] The four sides of the laser head 1 are connected to the frame 24 via four bolts 8 , respectively. Pressure buffer pads 9 are provided at the contact points between the four bolts 8 and the laser head 1 .

[0039] The wide bandgap ultraviolet sensor 12 collects the ultraviolet radiation light signal of the plasma 6 processed in different directions, and accumulates the ultraviolet radiation signal at the same time through the adder 17, calculates the ultraviolet radiation intensity under the unit pulse through the integrator 18, collects the signal at a fixed time interval, collects the integration result through the ADC processor 19, and transmits the collected result to the microcontroller 20. In the process of following the focus, it is possible that the ultraviolet radiation light signal is too small because the distance between the laser focus and the processing plane (hereinafter referred to as the defocus amount) is too large. At this time, the silicon photoelectric sensor 15 is selected to collect the radiation light signal of the plasma 6 processed in different directions. The collected signal passes through the adder 17, the integrator 18, and the ADC processor 19. When the signals received by the silicon photoelectric sensor 15 and the wide bandgap ultraviolet sensor 12 are both less than the threshold, the image signal of the camera 27 is read, the geometric size of the laser spot is photographed, and the collected result is transmitted to the microcontroller 20.

[0040] like Figure 4As shown, a three-degree-of-freedom translation platform 23 is provided below the processing platform 4, and a power signal bus 22 provides working power to the three-degree-of-freedom translation platform 23, the photoelectric sensor array frame 10, and the camera 27. The power signal bus 22 transmits the displacement distance signal of the processing platform 4, the plasma radiation signal on the photoelectric sensor array frame 10, and the image signal of the camera 27, as well as the movement signal of the processing platform 4. The method for high-precision focus-following processing of a workpiece curved surface using a strong laser beam is as follows. The three-degree-of-freedom translation platform 23 includes an X-direction displacement platform 23-1, a Z-direction displacement platform 23-2, and a Y-direction displacement platform 23-3.

[0041] Step 1, adjust the processing platform 4 to move downward to the lowest position of the processing platform 4, and fix the photoelectric sensor array frame 10 on the laser head. Set the expected value of the data collected by the wide bandgap ultraviolet sensor 12 during the processing to Ex1, the allowable error to Err1, the expected geometric size of the laser spot photographed by the camera 27 to R, the minimum step length in the X direction during processing to Dx, the minimum step length in the Z direction to Dz, the minimum signal value of the wide bandgap ultraviolet sensor 12 during processing to pmin, the minimum signal value of the silicon photoelectric sensor 15 to smin, and the maximum moving length of the processing platform along the positive direction of the z axis to L.

[0042] Step 2, the laser head 1 emits a laser beam 3 through the laser light outlet 2 to irradiate the workpiece 5, and the laser beam 3 ablates the workpiece 5 to generate a light signal radiated by the plasma 6. The camera 27 captures the laser spot on the surface of the workpiece 5, the silicon photoelectric sensor 15 collects the visible light signal radiated by the plasma 6, and the wide bandgap ultraviolet sensor 12 collects the ultraviolet light signal radiated by the plasma 6 and sends it to the microcontroller 20. The processing platform 4 moves upward by L, then stops and turns to move downward.

[0043] Step 3, the laser beam 3 ablates the workpiece 5, the wide bandgap ultraviolet sensor 12 collects the ultraviolet light signal radiated by the plasma 6 during the processing, and obtains the current plasma ultraviolet light radiation value Lnow through the adder 17 and the integrator 18 ADC processor 19, and sends it to the microcontroller 20. If |Lnow – Ex1|<= Err1, the processing platform 4 stops descending; if |Lnow –Ex1|>Err1, the processing platform 4 continues to descend.

[0044] Step 4, real-time focus in laser processing, includes the following steps:

[0045] 4.1. The laser beam 3 processes the workpiece 5. The three-degree-of-freedom translation stage 23 steps in the X direction with a displacement Dx according to the processing requirements. The adder 17, integrator 18, and ADC processor 19 obtain the current plasma ultraviolet light radiation value Lnow and send it to the microcontroller 20. If |Lnow – Ex1| <= Err1, repeat step 4.1; if |Lnow – Ex1| > Err1, execute step 4.2.

[0046] 4.2. The microcontroller 20 controls the processing platform 4 to displace a distance Dz in the positive z-axis direction. If |Lnow – Ex1| decreases, displace Dz in the positive direction; if it does not decrease, displace Dz in the negative z-axis direction, and repeat step 4.2 until |Lnow – Ex1| <= Err1. If Lnow < pmin, execute step 4.3.

[0047] 4.3. Gate the silicon photoelectric sensor 15 to collect the plasma ultraviolet light radiation signal Lnow generated by ablation at this time; adjust the height of the processing platform 4 so that Lnow > pmin, turn off the silicon photoelectric sensor 15, and execute step 4.2. If Lnow < smin, execute step 4.4.

[0048] 4.4. Use the camera 27 to transmit the image data back to the microcontroller 20, judge the geometric size of the laser spot, adjust the movement of the processing translation stage 4 so that the geometric size of the laser spot is equal to R, and execute step 4.3

[0049] Step 5. Repeat step 4 until the processing is completed, turn off the laser, and the device returns to the starting point.

[0050] Embodiment

[0051] Select a laser head of the GSS-FIB-20 model, whose laser wavelength is 1064 nm, the beam quality M2 < 2, the minimum line width is 0.01 mm, set the average optical power of the laser head to 5 W, the repetition working frequency is 20 kHz, and each output laser pulse is for continuous processing. The ablation trace is determined according to the processing requirements of the processing material. The tested ablation trace is a straight line, which can ensure that the plasma radiation intensity generated by laser ablation reaches the threshold of the signal collected by the sensor; The wide-bandgap photoelectric sensor of the present invention selects an LTK-G3535SGH type photodiode, the camera selects a WX605 type high-speed industrial camera, selects a 304 stainless steel material with a concave surface as the workpiece, and the microcontroller selects an STM32F407ZGT6.

[0052] When starting the test, adjust the processing plane to the lowest point of the electric stage, and then turn on the laser head to prepare for focus processing. First, the electric stage moves to complete the traversal of the UV signal. And determine the position of the laser focus, and then start the focus processing of the workpiece, where the displacement X is 2.5um, and the electric stage moves at a uniform speed according to the processing requirements until the processing is completed. Turn off the laser head and return the device.

[0053] After processing, the thickness uniformity and ablation depth of the processed straight lines are compared. Figure 5 It can be observed that the straight lines processed on the target material are uniform in thickness, and the ablation depth of the straight lines processed with different surface roughness under the laser is basically at a depth of 4μm. The results show that the targets with different surface roughness processed under this system can reach the precise focal plane position, achieving the purpose of high precision.

Claims

1. A processing method for a device for laser precision processing, characterized in that: The device comprises a photoelectric sensor array frame, a laser head is arranged at the center of the photoelectric sensor array frame, a processing platform is arranged directly below the laser head, a processing workpiece is arranged on the processing platform, a laser beam emitted by the laser head through a laser light outlet is vertically irradiated onto the processing workpiece, and the laser beam ablates the processing workpiece to generate a plasma radiation light signal; a three-degree-of-freedom translation platform is arranged below the processing platform; The photoelectric sensor array frame includes a circular frame body, which is evenly divided into four arc frames, two arc frames located on the same diagonal line are respectively provided with a wide bandgap ultraviolet sensor and a silicon photoelectric sensor, a camera is provided on the side of the frame body facing the workpiece, and the camera, the wide bandgap ultraviolet sensor and the silicon photoelectric sensor are located on the same side of the frame body; the wide bandgap ultraviolet sensor and the silicon photoelectric sensor are respectively connected with an adder, an integrator, an ADC processor and a microcontroller in sequence, and the microcontroller is also connected with the camera; The frame body is evenly provided with four grooves, and the four grooves divide the circular frame body into four arc frames; The laser head is connected to the frame body by four bolts on each side, and the four bolts are embedded in four grooves; Pressure buffer pads are provided at the contact points between the four bolts and the laser head; The method specifically comprises the following steps: Step 1, drive the processing platform downward to the lowest position of the processing platform through the three-degree-of-freedom translation stage, fix the laser head at the center of the photoelectric sensor array frame, set the expected value of the wide bandgap ultraviolet sensor to collect data during the processing as Ex1, the allowable error as Err1, the expected geometric size of the laser spot photographed by the camera as R, the minimum step length in the X-axis direction during processing as Dx, and the minimum step length in the Z-axis direction as Dz; set the minimum signal value of the wide bandgap ultraviolet sensor to pmin, the minimum signal value of the silicon photoelectric sensor to smin, and the maximum moving length of the processing platform along the positive direction of the Z axis to L during processing; Step 2: The laser head emits a laser beam through the laser light outlet to irradiate the workpiece, and the laser beam ablates the workpiece to generate a plasma radiation visible light signal and a plasma radiation ultraviolet light signal. The camera captures the laser spot on the surface of the workpiece, the silicon photoelectric sensor collects the plasma radiation visible light signal, and the wide bandgap ultraviolet sensor collects the plasma radiation ultraviolet light signal and sends them to the microcontroller. The processing platform moves upward along the Z axis by L, then stops and turns to move downward. Step 3: The wide bandgap ultraviolet sensor collects the ultraviolet light signal of the plasma radiation during the ablation process. The ultraviolet light signal of the plasma radiation passes through the adder, the integrator, and the ADC processor in sequence to obtain the current plasma ultraviolet light radiation value Lnow, which is sent to the microcontroller. If |Lnow – Ex1|≤ Err1, the processing platform stops descending; if |Lnow – Ex1| > Err1, the processing platform continues to descend; Step 4, real-time focusing of the workpiece during the processing; Step 5, repeat step 4 until the processing is completed, turn off the laser, and press Enter.

2. The processing method of a device for laser precision processing according to claim 1, characterized in that: The specific process of step 4 is as follows: Step 4.1, the laser beam processes the workpiece to be machined. The three-degree-of-freedom translation stage steps in the X-axis direction by Dx according to the machining requirements. The wide-bandgap ultraviolet sensor collects the ultraviolet light signal of the plasma radiation during the machining process. The ultraviolet light signal of the plasma radiation is successively obtained as the current plasma ultraviolet light radiation value Lnow through an adder, an integrator, and an ADC processor, and is sent to the microcontroller. If |Lnow – Ex1| ≤ Err1, repeat Step 4.1; if |Lnow – Ex1| > Err1, execute Step 4.2; Step 4.2, the microcontroller controls the machining platform to displace Dz in the positive z-axis direction. If |Lnow – Ex1| gradually decreases, the machining platform displaces Dz in the positive z-axis direction; if |Lnow – Ex1| does not decrease, the machining platform displaces Dz in the negative z-axis direction, and repeat Step 4.2 until |Lnow – Ex1| ≤ Err1; if Lnow < pmin, execute Step 4.3; Step 4.3, select and turn on the silicon photoelectric sensor to collect the ultraviolet light radiation value Lnow of the plasma generated by ablation at this time; adjust the height of the machining platform to make Lnow > pmin, turn off the silicon photoelectric sensor, and execute Step 4.

2. If Lnow < smin, execute Step 4.4; Step 4.4, use the camera to transmit the image data back to the microcontroller, judge the geometric size of the laser spot, adjust the movement of the machining platform to make the geometric size of the laser spot equal to R, and execute Step 4.3.

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