CN104759760A - Laser processing method of surface array microstructure of point cloud description curve workpiece - Google Patents

Abstract

The invention provides a surface array microstructure laser processing method for a curved surface workpiece described by a point cloud, comprising: using a reverse engineering method to measure and model the shape of a free curved surface workpiece to be processed, and to design graphics for the surface array microstructure based on the point cloud described curved surface Layout; then plan the laser etching processing path for the design graphics, adjust the spatial orientation of the laser processing head relative to the free-form surface workpiece according to the tangent plane where the processing path is located, the geometric center point, and the corresponding external normal vector, so that the laser beam is along the normal direction Shoot to the free-form surface workpiece, and perform laser etching of geometric lines one by one. The layout design of the surface array microstructure graphics of the present invention has nothing to do with the curvature distribution and change of the free-form surface, and is compatible with various types of free-form surfaces. The calculation scale is stable and convergent, and the layout efficiency is high; the surface array microstructure is completely eliminated. The layout and processing errors of the graphics ensure the accuracy and stability of the laser etching process quality.

Description

Surface Array Microstructure Laser Machining Method of Point Cloud Describing Curved Surface Workpieces

technical field

The invention belongs to the technical field of laser processing, and in particular relates to a surface array microstructure laser processing method for a curved surface workpiece described by a point cloud.

Background technique

In the field of mechanical industry and electronic industry, it is often necessary to prepare array microstructures on the surface of the formed free-form surface workpiece. Microstructure refers to the tiny topological shape of the surface with a surface shape accuracy of submicron level and surface roughness of nanometer level with specific functions. The most important feature of microstructure is the functionality of its structure. For example, the surface structure of microstructure surface optical components determines the reflection, transmission or diffraction performance of light, which is convenient for optical designers to optimize the optical system, reduce weight and reduce volume. Another feature is that they generally have a large aspect ratio, which is different from the traditional surface parameters and statistical properties.

Due to the irregularity, non-rotation and non-extensibility of the shape of the surface workpiece, it is generally difficult to accurately describe it with mathematical equations. Usually, a series of discrete value points, that is, scattered point cloud data, are used to describe the free-form surface model. Among them, the scattered point cloud data can be obtained directly from measuring the size by using the reverse engineering method and making it into a 3D model, and then discretizing it in the CAD/CAM system.

Laser etching belongs to the category of laser removal in laser processing, and it can also be called evaporation processing. It is based on the thermophysical effect of the physical state change caused by the interaction between the laser and the processed material, and the comprehensive result of various energy changes. The main factors affecting the processing quality depend on parameters such as the wavelength of the laser, laser power density, beam quality, focusing state, and the physical properties of the processed material itself. The laser beam initially passes through the focusing lens and irradiates the workpiece at the focal plane, causing the surface temperature of the processed material to rise rapidly. When the temperature rises to close to the evaporation temperature of the material, the laser will start to remove the material. At this time, the solid metal undergoes a strong phase change. First, the metal begins to melt, and then part of it begins to vaporize. As the temperature continues to rise, the metal vapor carries the liquid phase material and violently splashes out from the bottom of the liquid phase at a very high speed, thereby exposing the new surface of the bottom to the laser beam, thereby continuously producing melting, evaporation and spraying. splash. Through this continuous irradiation, melting-evaporation, sputtering, and irradiation, until the required laser etching depth is reached or the entire workpiece material is penetrated. At the same time, the laser beam moves according to the set speed and path, and the required laser etching structure can be obtained.

In the prior art, there are generally two methods for processing surface array microstructures for the shape of curved workpieces. The first method is to conduct offline virtual design based on the theoretical workpiece model and then process the actual workpiece online. However, since any free-form surface workpiece has machining tolerances during the processing of its free-form surface shape, this method does not consider the actual workpiece. The error between the external dimension and the theoretical workpiece model, the processing error is relatively large. The second method is to conduct offline virtual layout and design based on surface array microstructure graphics, and then process the actual workpiece online. There are large deviations in layout and processing.

Contents of the invention

The present invention aims at the deficiencies of the above-mentioned prior art, and provides a surface array microstructure laser processing method for a curved surface workpiece described by a point cloud with small processing error, good accuracy and high stability.

The present invention is achieved through the following technical solutions:

A surface array microstructure laser processing method for point cloud description of a curved surface workpiece, comprising the following steps:

(1) Fixed clamping and positioning of the free-form surface workpiece; based on the spatial XYZ rectangular coordinate system, the external dimensions of the free-form surface workpiece surface are measured by reverse engineering methods, and the surface model based on the description of the scattered point cloud data is obtained, that is, the surface described by the point cloud; , the maximum spatial distance between adjacent points in the scattered point cloud data is not greater than the preset value α, and ΔDist>α, ΔAngle>D/α; ΔDist is the maximum distance error value of the periodic array microstructure layout, ΔAngle is the periodicity The maximum angular error value of the array microstructure layout, D is the space linear distance between the respective geometric center points of any two unit microstructures in the periodic array microstructure;

(2) Initialize the vertex set as an empty set; and on the point cloud description surface, take two initial points P ₀ (x ₀ , y ₀ , z ₀ ) and P ₁ (x ₁ , y ₁ , z ₁ ), Make the spatial straight-line distance Dist_P of two points P ₀ and P ₁ satisfy the relationship D-ΔDist<Dist_P<D+ΔDist, and mark P ₀ and P ₁ as "unexpanded" and add them to the vertex set;

(3) Take any point P _i marked as "unextended" in the vertex set, and perform N equal division expansion operations on the point cloud description surface to obtain M expansion points P _j ; N is 3, 4, 5 or 6 , j=1～M;

Among them, the meaning of the N equal division expansion operation is: according to the point P _i and an adjacent point P _i+1 of the point P _i that is marked as "unexpanded", search for the point cloud data in the point cloud description surface. Take the extension point P _j so that the following conditions are met: 1) The distance Dist_P _j between P _i and P _j needs to satisfy the relationship D-ΔDist<Dist_P _j <D+ΔDist; 2) The line connecting the two points P _i and P _j and The angle angle between the line connecting two points P _i and P _i+1 satisfies 2kπ/N-ΔAngle<angle<2kπ/N+ΔAngle, and k is a positive integer less than or equal to N;

(4) Mark the M expansion points P _j obtained in step (3) as "unexpanded" and add them to the vertex set, mark P _i as "extended"; calculate P _j and all other points in the vertex set respectively If there is at least one space distance value smaller than D/2 in all obtained space line distance values, it indicates that P _j is a redundant point, and it is deleted from the vertex set;

(5) Repeat steps (3)-(4), until there is no point marked as "unexpanded" in the vertex set;

(6) For all points P _t in the vertex set obtained in steps (2)-(5), calculate and obtain the tangent plane K _t and the external normal vector V _t of the point cloud description surface position where P _t is located; t is greater than 2 an integer of

(7) In the XYZ Cartesian coordinate system of the space where the point cloud describes the curved surface, arbitrarily select a space reference vector;

(8) On all tangent planes K _t , with its corresponding P _t point as the geometric center point, a design graph G _t of a unit microstructure is correspondingly arranged, and the same corresponding feature of the design graph on all tangent planes is satisfied The included angle between the edge line and the projection line of the spatial reference vector on _Kt is a fixed value;

(9) Perform laser etching processing path planning on all the design graphics G _t obtained in step (8), and obtain the corresponding laser etching processing path set R _t , R _t consists of several geometric lines located on the tangent plane K _t constitute.

(10) For all laser etching processing path sets R _t , according to the tangent plane K _t , the geometric center point P _t and the corresponding external normal vector V _t , pass through the starting point P _st of each geometric line in R _t , Make a parallel line V _st parallel to the V _t direction, search for the point P st _' closest to V _st in the point cloud data describing the surface of the point cloud, and calculate the spatial distance d _s between P _st and P _st '; similarly, after The end point P _tt of each geometric line in R _t is a parallel line V _tt parallel to the direction of V _t , search for the point P _{tt ' closest to V tt} in the point cloud data of the point cloud describing the curved surface, and calculate _{P tt and} The spatial distance d _t of P _tt ';

(11) For all the laser etching processing path sets R _t , adjust the spatial orientation of the laser processing head relative to the free-form surface workpiece according to the tangent plane K _t , the geometric center point P _t and the corresponding external normal vector V _t , so that the laser The beam shoots to the workpiece on the free-form surface along the V _t direction, that is, the optical axis of the focused laser beam emitted by the focusing objective lens of the laser processing head is parallel to V _t ;

(12) Select any unprocessed geometric line in R _t , and translate the laser processing head so that the focused laser beam emitted by the focusing objective lens passes through the starting point of the geometric line, and the focus of the beam is located on the free-form surface workpiece surface or has defocus quantity;

(13) Turn on the laser;

(14) Translate the laser processing head so that the focus of the beam moves from the starting point to the end point along the trajectory of the geometric line at a certain scanning speed, and at the same time make the distance between the focusing objective lens and the free-form surface workpiece along the V _i direction evenly adjusted during the moving process The size of d _t -d _s , that is, to ensure that the focus of the beam is always on the surface of the free-form surface workpiece or has a defocus amount during the traveling process; after reaching the end point, mark the geometric line as processed;

(15) Randomly select an unprocessed geometric line in R _t as the next processing line, if there is no next processing line, it indicates that all the geometric lines in R _t have been processed, and turn to step (18) ; If there is a next processing line, then judge whether the next processing line is connected end-to-end with the processed geometric lines in the step (14), if so, then proceed to the step (17); otherwise enter the step (16);

(16) Turn off the laser; translate the laser processing head so that the focused laser beam emitted through the focusing objective lens passes through the starting point of the next processing line, and the focus of the beam is located on the free-form surface workpiece surface or has a defocus amount; return to step (13);

(17) Translate the laser processing head so that the focused laser beam emitted by the focusing objective lens passes through the starting point of the next processing line, and the focus of the beam is located on the free-form surface workpiece surface or has a defocus amount; return to step (14);

(18) END.

The present invention has following beneficial effect:

1. The present invention uses the reverse engineering method to measure and model the shape of the free-form surface workpiece to be processed, and based on the point cloud to describe the surface model to design the graphic layout of the surface array microstructure, online measurement, design and processing are carried out in the same coordinate system, compared with the traditional The method completely eliminates the error problem between the actual dimensions of the workpiece and the theoretical workpiece model, and the design pattern of the array microstructure adopts a parallel projection method, which is completely consistent with the beam translation of laser processing (the essence of laser beam translation processing is the parallel projection of light rays), thus It also completely eliminates the layout and processing errors of surface array microstructure graphics.

2. Although the present invention uses reverse engineering equipment to measure free-form surface workpieces, the subsequent layout design and processing are all processed directly based on point cloud data, eliminating the need for surface fitting processing and greatly reducing the amount of calculation;

3. The layout and design of the surface array microstructure graphics of the present invention has nothing to do with the curvature distribution and change of the free-form surface, and is compatible with various types of free-form surfaces. The calculation scale is stable and convergent, and the layout efficiency is high;

4. The surface array microstructure graphic layout method of the present invention, the layout accuracy is directly related to the point cloud data accuracy measured by reverse engineering, and has the advantages of predictability and controllability, especially it can be flexibly controlled according to needs and specific applications, and the point cloud can be reasonably planned The amount of data, to further optimize the amount of calculation;

5. The surface array microstructure graphics layout method of the present invention satisfies that the included angles between the same corresponding feature edge of the design graphics on all tangent planes and the projection line of the space reference vector on _Ki are fixed values, thereby ensuring The spatial orientation of all array microstructures is as neat as possible. If the function of the periodic array microstructure is a frequency selective surface, then the spatial reference vector is consistent with the direction of the incident electromagnetic wave, which is very accurate, flexible and easy to adjust;

6. The present invention expands the operation through N equal divisions (N can be one of 3, 4, 5, or 6), so that the graphic layout of the periodic array microstructure can be designed as one of 120, 90, 72, and 60 degrees of staggered arrangement , not limited to the traditional 60-degree stagger;

7. The laser etching process of the surface array microstructure of the present invention can effectively ensure that the beam focus is always located on the surface of the free-form surface workpiece during the processing or has a certain amount of defocus according to the process requirements. Various "approximate focus" laser processing methods on the surface are a brand-new "accurate focus" laser processing method, which ensures the accuracy and stability of the laser etching process quality.

Detailed ways

The present invention will be described in further detail below in combination with specific embodiments.

The present invention provides a surface array microstructure laser processing method for curved surface workpieces described by point clouds, which can be used to arrange and prepare periodic array microstructures on the surface of a given free-form surface workpiece with a smooth surface; wherein, the composition The periodic unit spacing between the unit microstructures of the periodic array microstructure is D; the periodic unit spacing is defined as the space linear distance between the respective geometric center points of any two unit microstructures. Preset the maximum distance error value ΔDist (ΔDist is a real number greater than 0) and the maximum angle error value ΔAngle (ΔAngle is a real number greater than 0, and the unit is generally expressed in radians) in the periodic array microstructure layout.

The surface array microstructure laser processing method of the above-mentioned point cloud description curved surface workpiece specifically includes the following steps:

(1) Fixed clamping and positioning of the free-form surface workpiece; based on the spatial XYZ rectangular coordinate system, the external dimensions of the free-form surface workpiece surface are measured by reverse engineering methods, and the surface model described based on the scattered point cloud data is obtained. The following will be based on the scattered point cloud data. The described surface model is referred to as point cloud description surface. Among them, the accuracy of the surface described by the point cloud is controlled by the measurement accuracy of the reverse engineering method and the point density. The maximum spatial distance between adjacent points in the scattered point cloud data obtained by setting the measurement parameters of the 3D reverse engineering equipment is not greater than The value of α (α is a real number greater than 0, which can be set arbitrarily according to the needs), and requires ΔDist>α, ΔAngle>D/α, which means to ensure that the "N equal division expansion operation" of the points in the subsequent steps can be found Corresponding extension point;

(2) Initialize the vertex set as an empty set; and on the point cloud description surface, take two initial points P ₀ (x ₀ , y ₀ , z ₀ ) and P ₁ (x ₁ , y ₁ , z ₁ ), Make the spatial straight-line distance Dist_P of two points P ₀ and P ₁ satisfy the relationship D-ΔDist<Dist_P<D+ΔDist, and mark P ₀ and P ₁ as "unexpanded" and add them to the vertex set;

(3) Take any point P _i marked as "unextended" in the vertex set, and perform N equal-division expansion operations on the point cloud description surface (N is 3, 4, 5 or 6), and obtain M expansion points P _j (j=1~M);

Among them, the meaning of the N equal division expansion operation is: according to the point P _i and an adjacent point P i ₊₁ marked as "unexpanded" of the point P _i (obviously, the two points P _i and P _i+1 Space straight-line distance is greater than D-ΔDist, less than D+ΔDist), search for the extension point P _j (j=1~M) in the point cloud data of the point cloud description surface, so that the following conditions are met: 1) P _i , P The distance Dist_P _j between the two points of _j needs to satisfy the relationship D-ΔDist<Dist_P _j <D+ΔDist; 2) The angle between the line connecting the two points P _i and P _j and the line connecting the two points P _i and P _i+1 Satisfy 2kπ/N-ΔAngle<angle<2kπ/N+ΔAngle, k is a positive integer less than or equal to N;

(4) Mark the M expansion points P _j obtained in step (3) as "unexpanded" and add them to the vertex set, mark P _i as "extended"; calculate P _j and all other points in the vertex set respectively If there is at least one space distance value smaller than D/2 in all obtained space line distance values, it indicates that P _j is a redundant point, and it is deleted from the vertex set;

(5) Repeat steps (3)-(4), until there is no point marked as "unexpanded" in the vertex set;

(6) For all points P _t (t is an integer greater than 2) in the vertex set obtained in steps (2)-(5), calculate and obtain the tangent plane K _t and the external method of the position of the point cloud describing the surface where P _t is located Vector V _t (that is, K _t is perpendicular to V _t );

(7) In the XYZ Cartesian coordinate system of the space where the point cloud describes the surface, arbitrarily select a spatial reference vector (if the function of the periodic array microstructure is a frequency selective surface, then the spatial reference vector is consistent with the direction of the incident electromagnetic wave);

(8) On all tangent planes K _t , with its corresponding P _t point as the geometric center point, a design graph G _t of a unit microstructure is correspondingly arranged, and the same corresponding feature of the design graph on all tangent planes is satisfied The angle between the sideline (the feature sideline refers to any line segment that constitutes the design graphic G _i ) and the projection line of the space reference vector on K _t is a fixed value (that is, the rotation orientation of the design graphic around the P _t point is limited angle, to ensure that the spatial orientation of all array microstructures is as neat as possible);

(9) Perform laser etching processing path planning for all design graphics G _t (t=0～n, n is an integer greater than 2) obtained in step (8), and obtain a corresponding laser etching processing path set R _t ( t=0~n, n is an integer greater than 2), R _t is composed of several geometric lines located on the tangent plane K _t , and the geometric lines can be straight lines or curved lines.

Among them, laser etching processing path planning is defined as: according to the laser beam focus spot size and power density (combined to determine the etching line width and etching depth of a single scan), determine the graphic outline and laser beam focus spot The scanning path of the internal filling line, obviously, the scanning path here is the geometric line on the corresponding tangent plane K _i .

(10) For all laser etching processing path sets R _t (t=0~n, n is an integer greater than 2), according to the tangent plane K _t where it is located, the geometric center point P _t and the corresponding external normal vector V _t , After passing through the starting point P _st of each geometric line in R _t , draw a parallel line V _st parallel to the direction of V _t , search for the point P st _' closest to V _st in the point cloud data describing the surface of the point cloud, and calculate P _st and the spatial distance d _s of P _st '; similarly, through the end point P _tt of each geometric line in R _t , make a parallel line V _tt parallel to the direction of V _t , and search for the distance in the point cloud data of the point cloud describing the curved surface V _tt the nearest point P _tt ', and calculate the spatial distance d _t between P _tt and P _tt ';

(11) For all laser etching processing path sets R _t (t=0~n, n is an integer greater than 2), according to the tangent plane K _t , the geometric center point P _t and the corresponding external normal vector V _t , Adjust the spatial orientation of the laser processing head relative to the free-form surface workpiece, so that the laser beam shoots toward the free-form surface workpiece along the V _t direction, that is, the optical axis of the focused laser beam emitted by the focusing objective lens of the laser processing head is parallel to V _t ;

(12) Select any unprocessed geometric line in R _t , translate the laser processing head so that the focused laser beam emitted by the focusing objective lens passes through the starting point of the geometric line, and the focus of the beam is located on the surface of the free-form surface or according to the process requirements There is a certain amount of defocus;

(13) Turn on the laser;

(14) Translate the laser processing head so that the focus of the beam moves from the starting point to the end point along the trajectory of the geometric line at a certain scanning speed, and at the same time make the distance between the focusing objective lens and the free-form surface workpiece along the V _i direction evenly adjusted during the moving process The size of d _t -d _s , that is, to ensure that the focus of the beam is always on the surface of the free-form surface workpiece or has a certain amount of defocus according to the process requirements; after reaching the end point, mark the geometric line as processed;

(15) Randomly select an unprocessed geometric line in R _t as the next processing line, if there is no next processing line, it indicates that all the geometric lines in R _t have been processed, and turn to step (18) ; If there is a next processing line, then judge whether the next processing line is connected end-to-end with the processed geometric lines in the step (14), if so, then proceed to the step (17); otherwise enter the step (16);

(16) Turn off the laser; translate the laser processing head so that the focused laser beam emitted by the focusing objective lens passes through the starting point of the next processing line, and the focus of the beam is located on the surface of the free-form surface workpiece or has a certain amount of defocus according to the needs of the process; return to the step ( 13);

(17) Translate the laser processing head so that the focused laser beam emitted by the focusing objective lens passes through the starting point of the next processing line, and the focus of the beam is located on the surface of the free-form surface workpiece or has a certain amount of defocus according to the needs of the process; return to step (14);

(18) END.

It will be obvious to those skilled in the art that the present invention may be modified in various ways and such modifications are not to be regarded as departing from the scope of the present invention. All such modifications obvious to those skilled in the art are intended to be included within the scope of this claim.

Claims (1)

1. some cloud describes a surface array micro-structural laser processing for curve surface work pieces, it is characterized in that, comprises the steps:

(1) fixing clamping and positioning free curve surface work pieces; Based on space X YZ rectangular coordinate system, adopt reverse engineering approach to measure the appearance and size on free curve surface work pieces surface, obtain the surface model described based on scattered point cloud data, namely put cloud and describe curved surface; Wherein, in scattered point cloud data, the maximum space distance of consecutive points is not more than the value α preset, and Δ Dist > α, Δ Angle > D/ α; Δ Dist is cyclic array micro-structural layout maximum distance error value, Δ Angle is the maximum angle error amount of cyclic array micro-structural layout, and D is the air line distance between the respective geometric center point of any two elementary microstructures in cyclic array micro-structural;

(2) vertex set is initialized as empty set; And describe on curved surface at a cloud, get two initial point P ₀(x ₀, y ₀, z ₀) and P ₁(x ₁, y ₁, z ₁), make P ₀, P ₁the air line distance Dist_P of 2 and periodic cells space D meet relation D-Δ Dist < Dist_P < D+ Δ Dist, by P ₀, P ₁all be labeled as " expansion " and add vertex set;

(3) get in vertex set that any one is labeled as the some P of " expansion " _i, describe on curved surface at a cloud and carry out minute extended operations such as N, obtain M extension point P _j; N gets 3,4,5 or 6, j=1 ~ M;

Wherein, the implication of N etc. points of extended operations is: according to a P _iand some P _ione adjacent and be labeled as the some P of " expansion " _i+1, describe at a cloud in the cloud data of curved surface to search for seek and get extension point P _j, make satisfied following condition: 1) P _i, P _jthe distance Dist_P of 2 _jdemand fulfillment relation D-Δ Dist < Dist_P _j< D+ Δ Dist; 2) P _i, P _j2 lines and P _i, P _i+1angle angle between 2 lines meets 2k π/N-Δ Angle < angle < 2k π/N+ Δ Angle, and k is the positive integer being less than or equal to N;

(4) M extension point P step (3) obtained _j, be all labeled as " expansion " and add vertex set, by P _ibe labeled as " expanding "; Calculate P respectively _jwith the air line distance of point every other in vertex set, if there is at least one space length value in all air line distance values obtained to be less than D/2, then show P _jbe redundant points, it is deleted from vertex set;

(5) step (3)-(4) are repeated, until vertex set does not exist the point being labeled as " expansion ";

(6) there is a P in the institute in the vertex set obtained step (2)-(5) _t, calculate and try to achieve P _tpoint cloud describes the section K of surface location _twith outer-normal direction V _t; T be greater than 2 integer;

(7) describe in the space X YZ rectangular coordinate system at curved surface place at a cloud, select a space reference vector arbitrarily;

(8) at all section K _ton, with the P of its correspondence _tpoint is the design configuration G of geometric center point, a corresponding arrangement elementary microstructure _t, and meet the same character pair sideline of the design configuration on all sections and space reference vector at K _ton projection line between angle be fixed value;

(9) to all design configuration G that step (8) obtains _tcarry out the planning of laser ablation machining path, obtain corresponding laser ablation machining path set R _t, R _tsection K is positioned at by some _ton geometry lines form.

(10) to all laser ablation machining path set R _t, according to the section K at its place _t, geometric center point P _tand corresponding outer-normal direction V _t, through R _tin the starting point P of each geometry lines _st, do and V _tthe parallel lines V that direction is parallel _st, Searching point cloud describes distance V in the cloud data of curved surface _stnearest some P _st', and calculate P _stand P _st' space length d _s; Same, through R _tin the terminal P of each geometry lines _tt, do and V _tthe parallel lines V that direction is parallel _tt, Searching point cloud describes distance V in the cloud data of curved surface _ttnearest some P _tt', and calculate P _ttand P _tt' space length d _t;

(11) to all laser ablation machining path set R _t, according to the section K at its place _t, geometric center point P _tand corresponding outer-normal direction V _t, the dimensional orientation of the relative free curve surface work pieces of adjustment laser Machining head, makes laser beam along V _tdirection directive free curve surface work pieces, namely makes laser focusing bundle optical axis and the V of the focusing objective len outgoing of laser Machining head _tparallel;

(12) at R _tany untreated geometry lines of middle selection, translation laser Machining head makes laser focusing bundle through focusing objective len outgoing through the starting point of these geometry lines, and beam focus is positioned at free curve surface work pieces surface or has defocusing amount;

(13) laser is opened;

(14) translation laser Machining head, makes beam focus be advanced to terminal translation by starting point with the track of certain sweep speed along these geometry lines, makes focusing objective len and free curve surface work pieces along V in traveling process simultaneously _ithe distance in direction adjusts d uniformly _t-d _ssize, namely ensures that beam focus is positioned at free curve surface work pieces surface all the time or has defocusing amount in traveling process; After reaching home, mark these geometry lines for processed;

(15) at R _tin select arbitrarily a untreated geometrical line bar as next processing lines, if there are not next processing lines, then show R _tin all processed mistake of geometry lines, proceed to step (18); If there are next processing lines, then judge next processing lines whether with finished geometry lines tandem array in step (14), if so, then proceed to step (17); Otherwise enter step (16);

(16) laser is closed; Translation laser Machining head makes the laser focusing bundle through focusing objective len outgoing pass the starting point of next processing lines, and beam focus is positioned at free curve surface work pieces surface or has defocusing amount; Return step (13);

(17) translation laser Machining head makes the laser focusing bundle through focusing objective len outgoing pass the starting point of next processing lines, and beam focus is positioned at free curve surface work pieces surface or has defocusing amount; Return step (14);

(18) terminate.