A method of suppressing laser manufacturing taper

Abstract

The application discloses a method for inhibiting laser manufacturing taper, comprising the following steps: using preset light parameters to perform normal incidence reciprocating scanning subtractive machining on a target profile to be machined to a preset depth, or additive deposition to a predetermined thickness, for a feature section of the target profile, ensuring that the light movement track is parallel to the feature section, and ensuring the uniformity of the light movement track at least in the direction parallel to the feature section; under the condition of the preset light parameters, quantifying the taper surface orthographic projection width L caused by the cross section taper of the machined structure, the orthographic projection direction being consistent with the laser incidence direction; for the test piece, determining the steady-state scanning speed v of the light track by using a formula, the direction of v being at an angle of θ with the target profile, a being the absolute value of the acceleration in the process that the scanning movement of the machining head reaches the steady-state speed v from the speed 0 or decreases from the steady-state speed v to 0, and k being a dimensionless coefficient; and taking the steady-state scanning speed v as the steady-state scanning speed for formal workpiece machining. The total deposition energy is spatially homogenized.

Description

Technical Field

[0001] This application relates to the field of laser processing technology, and in particular to a method for suppressing laser manufacturing taper. Background Technology

[0002] Laser processing boasts advantages such as material universality, non-contact stress, cross-scale processing, and high process flexibility. In particular, the rapidly developing short-pulse and ultra-short-pulse laser processing has gained widespread application due to its unique advantages. For example, as the average power of industrial-grade ultra-short-pulse lasers (also known as ultrafast lasers) approaches the kilowatt level, its application is rapidly expanding towards macroscopic laser manufacturing: laser cutting, laser milling, and laser reduction deposition have been among the first applications, and are now being used in aerospace, weaponry, and electronics industries for cutting thin-walled, hard, and brittle materials, laser milling of superhard materials, flexible circuit pattern deposition, and 3D printing.

[0003] Despite the numerous advantages of short-pulse and ultrashort-pulse laser processing, the inherent Gaussian distribution of their radial energy leads to an unavoidable taper problem in structures formed during normal-incidence subtractive or additive manufacturing. This issue also exists in other types of laser processing. The taper problem directly affects the accuracy of the structure and the processing limits. For example, in laser subtractive manufacturing, the taper results in through-holes with a large inlet and a small outlet, easily causing the hole diameter to exceed tolerances. When the inlet width of the kerf is limited, the taper problem may directly prevent the material from being cut through. Similarly, in laser additive manufacturing of fine metal patterns, the radial Gaussian distribution of the beam energy will result in a curved trapezoidal cross-section instead of a rectangle. Current methods for suppressing the taper problem in laser processing generally fall into two categories: shaping the natural Gaussian beam into a beam with a uniform radial energy distribution using optoelectronic devices, or using a processing system with at least four axes of linkage to compensate for the taper through oblique beam incidence. These methods have inherent advantages, but they also have drawbacks such as requiring additional hardware or being relatively complex to implement.

[0004] Therefore, there is a need to develop a simple, high-precision, and low-cost method for taper suppression or even elimination, that is, a method that can achieve significant taper suppression or even elimination without relying on a four-axis or more-axis linkage machining system or without beam shaping of the natural Gaussian beam. Summary of the Invention

[0005] This application provides a method to suppress or even eliminate the taper in structural manufacturing. The purpose is to address the natural processing taper problem of radially Gaussian distributed pulsed lasers. Without relying on additional hardware costs such as radial beam energy homogenization or multi-degree-of-freedom linkage oblique incidence taper elimination, the method utilizes the natural over-deposition defect of energy caused by under-scanning speed at the start and stop points of the light trajectory to quantitatively and directionally compensate for the under-deposition of Gaussian beam edge energy, thereby achieving spatial homogenization of total deposition energy.

[0006] In a first aspect, a method for suppressing taper in laser manufacturing is provided, comprising:

[0007] Step 1: Using preset light parameters, perform reciprocating scanning subtractive processing on the target contour to be processed to a preset depth, or additive deposition to a predetermined thickness. For the characteristic structural segment of the target contour, ensure that the light trajectory is parallel to the characteristic structural segment, and ensure the uniformity of the light trajectory parallel to the characteristic structural segment at least.

[0008] Step 2: Under the preset optical parameters, quantify the orthographic projection width L of the processed structure caused by the cross-sectional taper, with the orthographic projection direction consistent with the laser incident direction;

[0009] Step 3, for the specimen, use the formula The steady-state scanning speed v of the light trajectory is determined, the angle between the direction of v and the target contour is θ, a is the absolute value of the acceleration of the processing head scanning motion from speed 0 to steady-state speed v, or from steady-state speed v to 0, and k is a dimensionless coefficient.

[0010] Step 4: Use the steady-state scanning speed v obtained in Step 3 as the steady-state scanning speed for the actual workpiece machining.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, step 4 includes:

[0012] Check whether the taper of the target structure of the test piece meets the requirements. If it does not, jump to step 1 or step 3 until the taper of the cross section meets the requirements, and use the steady-state scanning speed v that meets the requirements for the manufacturing of the formal workpiece.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the jump to step 1 includes:

[0014] Using different optical parameters than in the previous iteration, the target contour to be processed is subjected to normal incident reciprocating scanning subtractive processing to a preset depth, or additive deposition to a predetermined thickness.

[0015] In conjunction with the first aspect, in some implementations of the first aspect, the jump to step 3 includes:

[0016] The trajectory parameters used on the specimen are different from those in the previous iteration, including at least one of the following: θ, k, v.

[0017] In conjunction with the first aspect, in certain implementations of the first aspect, the method satisfies at least one of the following:

[0018] The workpiece material to be processed is a solid material;

[0019] The laser is a pulsed laser, with a single pulse duration of <100ms;

[0020] The range of θ is defined as 0 < θ ≤ 90°;

[0021] The value of k ranges from [0.5, 1.5].

[0022] Secondly, a method for suppressing taper in laser manufacturing is provided, including:

[0023] The workpiece is processed according to the steady-state scanning speed v and preset optical parameters, wherein the steady-state scanning speed v satisfies The angle between the direction of v and the target contour is θ, a is the absolute value of the acceleration of the processing head scanning motion from speed 0 to steady-state speed v, or from steady-state speed v to 0, k is a dimensionless coefficient, where L is the width of the cone surface orthogonal projection of the feature structure segment of the target contour due to the cross-sectional taper under the preset light parameters, the feature structure segment is scanned to a preset depth by normal incidence reciprocating scanning direction, or to a predetermined thickness by normal incidence reciprocating additive deposition, the light motion trajectory of the feature structure segment is parallel to the feature structure segment, and the light motion trajectory has uniformity.

[0024] Thirdly, a laser-manufactured workpiece is provided, which is prepared by the method described in any of the implementations of the first to second aspects above.

[0025] Fourthly, a laser manufacturing apparatus is provided, the laser manufacturing apparatus being used to perform the method as described in any of the implementations of the first to second aspects described above.

[0026] Compared with the prior art, the solution provided in this application has at least the following beneficial technical effects:

[0027] (1) The present invention provides a method for suppressing laser manufacturing taper. Compared with existing methods such as energy radial distribution homogenization after beam spatial shaping and multi-degree-of-freedom linkage oblique incidence taper elimination, it does not require the use of optoelectronic devices to flatten the top of the spatial Gaussian beam, nor does it require a four-axis or more-axis linkage processing system. It is an economical method.

[0028] (2) The present invention provides a method for suppressing laser manufacturing taper, which is to quantitatively and directionally compensate for the excessive deposition of light energy at the edge of the Gaussian beam by utilizing the natural underscan speed at the start and stop points of the light trajectory to achieve spatial homogenization of the total deposition energy and thus suppress taper. It utilizes the natural defects of the light parameters and the natural defects of the light motion trajectory control in the laser manufacturing system to cleverly achieve the effect of "using defects to cure defects". It is a simple but precise method.

[0029] (3) The present invention provides a method for suppressing taper in laser manufacturing, and gives a quantitative calculation formula for setting the steady-state scanning speed. The proposed method is applicable to various laser subtractive and laser additive manufacturing methods such as laser cutting, laser milling, laser rotary cutting for hole making, and laser deposition. Moreover, the taper suppression method is universal for different types of materials, and the degree of taper compensation can be flexibly adjusted as needed. Therefore, this method is also a flexible and universal method. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a method for suppressing laser manufacturing taper according to the present invention.

[0031] Figure 2 The image shows a near-zero cone structure with a machining depth of 0.6 mm after applying the present invention.

[0032] Figure 3 This is a top-view micrograph of the structure with a processing depth of 0.3 mm before the application of this invention. Detailed Implementation

[0033] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0034] Figure 1 This is a schematic flowchart of a method for suppressing taper in laser manufacturing provided by the present invention. The specific steps are as follows.

[0035] Step 1: Consider the light trajectory parallel to the target contour feature structure, and ensure the uniformity of the light trajectory at least in the segment parallel to the feature structure. On the specimen, use preset light parameters and other processing parameters to perform normal incident reciprocating scanning subtractive processing to a preset depth, or additive deposition to a predetermined thickness on the feature structure of the target contour to be processed.

[0036] Specifically, the laser energy of the processing system is turned on, and the relative positions and orientations of the various components of the processing system are adjusted. To eliminate the defects caused by the inherent motion characteristics of the optical trajectory, i.e., the under-scanning speed at the start and stop points of the trajectory leading to over-deposition and over-processing of energy, and to expose the taper caused solely by optical parameter defects (i.e., a Gaussian beam that is strong in the middle and weak at the edges), a light trajectory parallel to the target contour feature structure is considered. This ensures the uniformity of the light trajectory at least in the segment parallel to the feature structure. Then, using preset optical parameters and other processing parameters, a reciprocating subtractive machining process is performed on the workpiece using normal incident light on the feature structure of the target contour to be processed, either to a preset depth or to additive deposition to a predetermined thickness. The workpiece material is a solid material. The laser used is a pulsed laser with a single duration of <100ms.

[0037] Step 2: Quantify the orthographic projection width L of the conical surface caused by the taper of the structure section being processed, that is, at the point of maximum processing depth or maximum deposition thickness, measure the maximum offset from the preset processing contour caused by the taper.

[0038] Specifically, the orthographic projection width L of the conical surface caused by the taper of the processed structure's cross-section is calculated, which is the maximum offset from the preset processing contour caused by the taper at the point of maximum processing depth or maximum deposition thickness. The orthographic projection direction is consistent with the laser incident direction.

[0039] Step 3: For the test piece, use the proposed formula to set the steady-state scanning speed v of the light trajectory, the angle between the direction of v and the target contour is θ, and set other light parameters and processing parameters to start processing until the preset operation is completed.

[0040] The steady-state scanning speed v of the optical trajectory is quantized and set according to the following calculation method:

[0041]

[0042] Where L is the maximum offset from the preset processing contour caused by the taper at the maximum processing depth or the maximum deposition thickness in step 2; k is a dimensionless variable parameter with a value near 1, ranging from [0.5, 1.5], usually set to 1; the physical meaning of kL is: the effective length required to achieve the optimal taper suppression effect by using the underscan speed compensation at the start and stop points of the optical trajectory—considering that L cannot be determined very precisely, or even if it can be determined precisely but the length of the optical trajectory < v is exactly equal to L, it will not always produce the optimal taper compensation effect; a is the absolute value of the acceleration of the processing head scanning motion from speed 0 to steady-state speed v, or from steady-state speed v to 0; θ is the angle between the trajectory direction and the target contour in step 3, with the value range of θ set to 0 < θ ≤ 90°.

[0043] Step 4: Check if the taper of the target structure of the test piece meets the requirements: If not, jump to step 1 or step 3 until the cross-sectional taper meets the requirements, and use the output results for the manufacturing of the formal workpiece.

[0044] In some embodiments, the process can initially proceed to step 3, and the trajectory parameters (including θ, k, and v) in step 3 can be adjusted as needed. Step 3 can be used to adapt the optical trajectory parameters to the optical parameters given a fixed optical parameter set. If the cross-sectional taper still does not meet the requirements after multiple adjustments to the trajectory parameters, the process can proceed to step 1, and the optical parameters can be changed, for example, by adjusting the peak flux of the spatial Gaussian spot. Proceeding to step 1 helps to eliminate problems introduced by unsuitable optical parameters.

[0045] Specifically, based on the dimensions and precision of the structure, an optical microscope, vernier calipers, or other measuring methods are selected to check whether the taper of the target structure of the test piece meets the requirements. If it does not meet the requirements, proceed to step 2 and adjust the parameters in step 3 according to the requirements until the cross-sectional taper meets the requirements. The output results are then used for the manufacturing of the final workpiece.

[0046] The following is a further explanation with reference to specific embodiments:

[0047] The material being processed is a synthetic polycrystalline diamond with a thickness of 2mm and an area of ​​22mm×22mm. After processing, a periodic array of square pillars with dimensions of 0.3mm×0.3mm×0.6mm and a total area of ​​10mm×10mm needs to be left on it. The blind cavity between adjacent square pillars has a size of 0.3mm×0.3mm×0.6mm.

[0048] The laser in CNC laser processing equipment can emit a Gaussian beam with a center wavelength of 532nm. After optical path transmission and focusing by the scanning head lens, it is projected onto the workpiece surface, generating a single-pulse sequence with a duration of 15ps and an adjustable pulse frequency of 0.1MHz to 2MHz. The peak flux of the generated spatial Gaussian spot can reach up to 10J / cm². 2 Press "1 / e" 2 The diameter of the focused spot, defined by the Gaussian spot diameter, is approximately 60 μm. The scanning galvanometer head used has a scanning acceleration of a = 51000 m / s². 2 This is an inherent property of the processing head.

[0049] First, consider the light trajectory parallel to the target contour feature structure to ensure the uniformity of the light trajectory parallel to the feature structure segment. Then, using preset light parameters and other light trajectory parameters, perform normal incident reciprocating scanning milling on the specimen to the feature structure of the target contour to be processed to the preset depth. Record key parameters, including pulse peak flux F0, the equivalent number of light spots n on a single spot position, the pulse repetition frequency f, and the number of scanning milling layers N.

[0050] Secondly, the orthographic projection width L of the conical surface caused by the cross-sectional taper was quantified. Measurements of the cross-sectional taper showed an average taper of 16.5°. This means that at a machining depth of 0.6 mm, the orthographic projection width L of the conical surface would be approximately tan(16.5°) × 0.6 mm ≈ 0.178 mm. Further investigation revealed that although the machining taper changes continuously with the machining depth (i.e., the conical surface is not a strictly flat plane), the average taper of the formed conical surface remains stable between 14-17° at machining depths of 0.2 mm, 0.4 mm, and 0.6 mm. Therefore, to significantly reduce workload, it is not necessary to machine to a depth of 0.6 mm before evaluating the taper and the corresponding L. Instead, the orthographic projection width L of the conical surface at a machining depth of 0.6 mm can be calculated based on the taper angle at a depth of 0.2 mm.

[0051] Next, the steady-state scanning speed v of the optical trajectory is set using the proposed formula. Since the acceleration of the scanning galvanometer used is a = 51000 m / s²,... 2 The width of the cone's orthographic projection is L = 0.178 mm, and the angle between the preset trajectory velocity v direction and the target contour is θ = 45°, which can be calculated using the formula... (Taking k as a typical value of 1), we obtain v = 5.05 m / s. At the same time, we continue to use the key parameters from the first step, including the pulse peak flux F0, the equivalent number of light spots n on a single spot position, the pulse repetition frequency f, and the number of layers N for scanning milling, to ensure that the contribution of the taper factor caused by the Gaussian beam distribution characteristics remains unchanged.

[0052] Finally, an optical microscope was used to inspect whether the taper of the target structure of the test piece met the requirements. Observation revealed that the taper of the cross-section was less than 1° (the taper of each square platform was distributed between 0° and 2°), meaning the precision of the machined structure was very close to that of a 0.3mm × 0.3mm × 0.6mm square column, fully meeting the product's manufacturing requirements, and no further iterative refinement to eliminate the taper was necessary. Therefore, the output results were used for the manufacturing of the final workpiece. A partial view of the machined component is shown below. Figure 2 As shown.

[0053] As can be seen, the preset target of 0.3mm×0.3mm×0.6mm arrayed square pillars has been achieved, and no obvious graphitization or other defects are observed on the near-zero cone surfaces of each square platform. This demonstrates that the proposed method achieves good shape and property control in the fabrication of small array structures.

[0054] In contrast, if the overcut caused by the underscan speed at the start and stop points of the optical trajectory is not compensated for by the present invention, the "strong in the middle and weak at both ends" characteristic of the Gaussian beam will result in an average taper of up to 16.5° as described above. Therefore, when processing a square prism with a preset target size of 0.3mm × 0.3mm × 0.3mm, what is actually produced is a frustum with a depth of 0.3mm, an entrance size of 0.3mm × 0.3mm, and a bottom size of 0.48mm × 0.48mm. Figure 3 As shown. Furthermore, the presence of the conical surface intercepts the pulse energy that is continuously incident in order to reach the preset processing depth. This causes the already formed conical surface to bear energy that should not be there, which directly leads to the graphitization of the diamond conical surface.

[0055] As a common method, the present invention provides a method for suppressing taper in laser manufacturing, which obviously has good universality: it utilizes the energy over-deposition defect caused by the natural underscan velocity at the start and stop points of the light trajectory to quantitatively and directionally compensate for the under-deposition of energy at the edge of the spot caused by the Gaussian beam, thus achieving spatial homogenization of the total deposited energy. Since the physical essence of laser milling, laser cutting, and laser additive manufacturing is the interaction between laser energy and matter, once the spatial homogenization of the total deposited energy is achieved, suppressing or even completely eliminating taper becomes a natural and inevitable result. Therefore, the present invention also has the characteristics of simplicity and reliability, and can directly use existing popular equipment without adding any additional hardware conditions to achieve taper suppression or even elimination, making it an economical and easy-to-implement method.

[0056] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A method for suppressing taper in laser manufacturing, characterized in that, include: Step 1: Using preset light parameters, perform reciprocating scanning subtractive processing on the target contour to be processed to a preset depth, or additive deposition to a predetermined thickness. For the characteristic structural segment of the target contour, ensure that the light trajectory is parallel to the characteristic structural segment, and ensure the uniformity of the light trajectory parallel to the characteristic structural segment at least. Step 2: Under the preset light parameters, calculate the orthographic projection width of the conical surface of the feature structure segment caused by the cross-sectional taper. L That is, at the point of maximum processing depth or maximum deposition thickness, the maximum offset caused by the taper from the preset processing contour is measured, and the orthographic projection direction is consistent with the laser incident direction. Step 3, for the specimen, use the formula Determine the steady-state scanning speed of the light motion trajectory. v , v The angle between the direction and the target contour is θ , θ The range of values ​​is defined as 0 < θ ≤ 90°. a The scanning motion of the processing head reaches a steady-state speed from 0. v or steady-state velocity from v The absolute value of the acceleration during the process of decreasing to 0. k =1, kL The physical meaning is: the effective length required to achieve the optimal cone suppression effect by using the underscan velocity compensation at the start and stop points of the light motion trajectory; Step 4: Check if the taper of the target structure of the test piece meets the requirements. If not, proceed to step 1 or step 3 until the cross-sectional taper meets the requirements, and then set the steady-state scanning speed that meets the requirements. v Used for the manufacture of actual workpieces; among them, The jump to step 1 includes: Using different optical parameters than in the previous iteration, the target contour to be processed is subjected to normal incident reciprocating scanning subtractive processing to a preset depth, or additive deposition to a predetermined thickness. The jump to step 3 includes: The trajectory parameters used on the specimen are different from those in the previous iteration, including at least one of the following: θ , k .

2. The method according to claim 1, characterized in that, The method satisfies at least one of the following: The workpiece material to be processed is a solid material; The laser is a pulsed laser, with a single pulse duration of <100ms.

3. A laser-manufactured workpiece, characterized in that, The laser-manufactured workpiece is prepared by the method described in any one of claims 1 to 2.

4. A laser manufacturing device, characterized in that, The laser manufacturing equipment is used to perform the method as described in any one of claims 1 to 2.

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