CN-116100170-B - Ultrafast laser high-quality efficient inclined hole machining method

CN116100170BCN 116100170 BCN116100170 BCN 116100170BCN-116100170-B

Abstract

The invention provides an ultrafast laser high-quality and high-efficiency inclined hole processing method, which is characterized in that multiple pulse ablation thresholds under an inclined workpiece are calculated through ablation pit results under different pulse energies, and are combined with energy density equations under different focal depths to further obtain ablation depth equations of different focal depths on an inclined plane, different processing methods and processing parameters are designed from the inlet, middle and outlet stages of the inclined hole, and the feeding depth of each stage is calculated through the ablation depth equations of different focal depths and the scanning times. The method combines theoretical calculation with actual technology, and establishes an ablation depth prediction model in the inclined hole machining process by calculating ablation depth equations of different focal depths on an inclined plane, so that a high-quality and efficient machining method and machining parameters of the inclined hole are further determined, and different scanning modes and machining parameters are selected in three stages of an inlet, a middle and an outlet, so that the problems of poor hole wall quality, poor process stability, low machining efficiency and the like of the inclined hole can be effectively solved.

Inventors

DONG ZHIGANG
BAO YAN
MA HONGBIN
YANG FENG
MA GUANGYI
KANG RENKE

Assignees

大连理工大学

Dates

Publication Date: 20260505
Application Date: 20221110

Claims (3)

1. The method for processing the inclined hole by using the ultrafast laser with high quality and high efficiency is characterized by comprising the following steps of: S1, establishing an ablation depth prediction model of an inclined workpiece, which specifically comprises the steps of performing multiple pulse ablation experiments on the workpiece with the inclination angle theta, and calculating multiple pulse ablation thresholds under the inclined workpiece through ablation pit results under different pulse energies E p The multi-pulse ablation threshold represents a critical value of material removal, and an ablation depth equation of different focal depths on the inclined plane is further obtained by combining energy density equations of different focal depths; S2, determining a processing method and processing parameters of the inclined hole, and designing different processing methods and processing parameters from an inlet stage, a middle stage and an outlet stage of the inclined hole, wherein the inlet stage adopts lower pulse energy E p1 and fewer scanning times N 1 to perform spiral line surface scanning processing; Multiple pulse ablation threshold under the inclined workpiece The calculation of (1) comprises the following steps: controlling laser to perform multiple pulse ablation experiments on an inclined workpiece, and measuring the ablation pit diameter D of different laser energy under multiple pulses by changing the laser single pulse energy E p ; The peak energy density in the oblique cross section of the gaussian beam is given by: In the formula, Is the peak energy density on the surface, N is the number of pulses, Is the radius of the girdle; The relationship between laser ablation pit diameter and laser energy density is as follows: In the formula, For ablation threshold, the relation between multi-pulse energy and ablation pit diameter can be deduced from equations (1) and (2), which are as follows: Drawing an experimental data scatter diagram according to the formula (3) and performing linear fitting to obtain that the square of the multipulse energy logarithm and the ablation pit diameter meets the linear relation, so as to calculate a multipulse ablation threshold; the energy density equation under different focal depths is specifically determined by an energy density formula which is distributed along the radial direction and obeys Gaussian function and the determined spot radius size, namely the energy density which is far away from the center of the spot in the radial direction Determined by the following formula: In a focused laser system, the light spot radius is changed along the propagation direction of a light beam, any section on the central axis is in a hyperbolic form, and the light spot radius is far away from the focal distance z in the propagation direction Determined by the following formula: In the formula, For the rayleigh length of the laser system, it is determined by: In the formula, Is the laser wavelength; The energy density equations at different depths of focus can be obtained from equations (4), (5) and (6), which are as follows: The ablation depth equation of different focal depths on the inclined plane can be determined according to the theoretical ablation depth of laser irradiated to each position of the ablation surface by the following logarithmic function, and is divided into a negative defocus formula and a positive defocus formula: Wherein H f 、H b respectively represents the ablation depth under the conditions of negative defocus and positive defocus and is used for predicting the processing depth under different defocus states, Is the negative defocus ablation depth coefficient, Is the positive defocus ablation depth coefficient, In order to achieve a laser energy density, Is a multipulse ablation threshold, wherein the ablation depth coefficient is used for measuring the ablation depth through a positive and negative defocus test and combining the laser energy density And a multipulse ablation threshold The laser energy is subjected to Gaussian distribution, when the processing depth deepest of different focal depths is r is 0, namely, the central axis position is the ablation depth deepest position in the spot area, and the ablation depth equation can be simplified by setting the depth as the ablation depth of different focal depths:
2. The ultra-fast laser high-quality and high-efficiency inclined hole processing method according to claim 1, wherein the method further comprises the following steps of: s3, performing three-stage machining parameter test verification of the inlet, the middle and the outlet of the inclined hole in S2, performing parameter correction, and finally performing integral inclined hole machining test verification, wherein the working procedure and the parameters are proper, and then performing actual machining.
3. The ultra-fast laser high-quality and high-efficiency inclined hole machining method according to claim 1, wherein the step S2 is specifically: The laser focusing position is positioned at the intersection position of the central axis of the round hole and the inclined plane, spiral line surface scanning processing with lower pulse energy E p1 and less scanning times N 1 is adopted, the processing surface is the inclined plane and is positioned at different focal depth positions of laser, so that the processing depth is different, the inclination angle between the processing bottom surface and the horizontal plane is gradually reduced, when the inclination angle change rate is less than 10%, the focusing point is axially fed, the feeding depth is a p1 , the size can be obtained through ablation depth equation of different focal depths and the scanning times N 1 , and then the steps are repeatedly carried out, and the processing bottom surface is near the horizontal plane after S 1 times of feeding processing is carried out; The middle stage comprises the steps of adopting higher pulse energy E p2 and more scanning times N 2 to perform spiral line surface scanning, axially feeding a focusing point when the ablation depth change rate is less than 5%, obtaining the feeding depth a p2 according to ablation depth equations of different focal depths and the scanning times N 2 , repeating the steps, and reaching the outlet part of the inclined hole when the bottom surface is about to be penetrated after performing S 2 times of feeding processing; And in the outlet stage, spiral line processing is carried out by adopting lower pulse energy E p3 , and the pitch of the feeding spiral line is obtained according to ablation depth equations of different focal depths.

Description

Ultrafast laser high-quality efficient inclined hole machining method Technical Field The invention relates to the field of special machining, in particular to an ultrafast laser high-quality efficient inclined hole machining method. Background In modern manufacturing industry, a large number of inclined micro holes are processed, such as oil spray holes of an internal combustion engine, air film cooling holes on a combustion chamber of an aeroengine, guide vanes and the like, and a large number of dense, discrete and small-diameter straight holes and inclined hole arrays are required to be processed on the wall surfaces of material components such as high-generation single crystals, ceramic matrix composite materials and the like. However, there is no high-quality and high-efficiency technical solution in the aspect of precision micro-machining of micro-holes, and with the development of laser technology, ultra-fast laser with high power and high beam quality appears, and because of the extremely short action time and extremely high light intensity density, thermal damage and mechanical damage in the material machining process can be reduced to a great extent, the laser machining quality is greatly improved, and the method has been widely used for precision micro-hole machining of various materials. However, the ultra-fast laser has the precision problems of taper, blind holes and the like in the processing of the inclined holes, and the problems of cracking, chipping, partial flaking, poor quality of the walls of the inlet and the outlet of the inclined holes, low processing efficiency, poor processing stability and the like can occur at the inlet and the outlet of the inclined holes. In the method, compared with the traditional mechanical processing, the damage to a material can be effectively reduced, but the access of the hole is still damaged due to laser ablation, in the method, the method for intelligently processing the special-shaped hole by using annular rotary laser is disclosed in the patent CN 112008262A, intelligent three-dimensional modeling is carried out according to the spatial structure of the hole to be processed, then control algorithm design and code generation are carried out, system control program codes are generated, finally an optical path module controls the spatial annular rotation of the laser beam, the edge processing quality of the hole is ensured, but only the optimization of a processing path is considered, and the processing parameters are not further changed to improve the hole quality and efficiency. The above problems greatly limit the practical application of the ultrafast laser processing technology for tilting small holes. Therefore, a method for processing the inclined holes with ultra-fast laser with high quality and high efficiency is needed, which can ensure that the damage of an access opening is reduced in the ultra-fast laser processing process, the quality of the hole wall is improved, and the processing efficiency is improved on the premise of high processing quality. Disclosure of Invention According to the technical problems, the method for processing the inclined holes by the ultrafast laser with high quality and high efficiency is provided. The invention can realize the laser processing of high-quality inclined small holes with different angles and different curved surfaces on different materials, adopts a mode of combining theoretical calculation with an actual process, proposes three-section processing of the inclined hole, selects different scanning modes and processing parameters from three stages of an inlet, a middle and an outlet of the inclined hole for processing, solves the problems of poor quality of a hole wall, poor process stability and the like of the inclined hole, improves the processing quality and the hole making efficiency of the inclined hole, and has high processing stability and self-adaption degree. The invention adopts the following technical means: An ultrafast laser high-quality and high-efficiency inclined hole processing method comprises the following steps: S1, establishing an ablation depth prediction model of an inclined workpiece, which specifically comprises the steps of performing multiple pulse ablation experiments on the workpiece with the inclination angle theta, and calculating multiple pulse ablation thresholds under the inclined workpiece through ablation pit results under different pulse energies E pThe multi-pulse ablation threshold represents a critical value of material removal, and an ablation depth equation of different focal depths on the inclined plane is further obtained by combining energy density equations of different focal depths; S2, determining a machining method and machining parameters of the inclined hole, and designing different machining methods and machining parameters from an inlet stage, a middle stage and an outlet stage of the inclined hole, wherein the inlet stage adopts lower pulse ener