System and method for variable speed laser forming continuous gradient materials

Abstract

The present application relates to the technical field of laser selective melting additive manufacturing, and provides a system and method for variable-speed laser forming of continuous gradient material, the system comprising a powder laying module for laying a gradient powder layer on a workbench; a laser module for emitting laser beams with different scanning speeds on the gradient powder layer on the workbench according to regions; a control module for dividing a powder bed into a plurality of rows and columns of feature rectangles, selecting feature rectangles within a two-dimensional contour of a printed part slice as feature rectangles to be printed, assigning printing parameters to each feature rectangle to be printed, arranging the printing direction and sequence of the feature rectangles to be printed, and controlling the laser module and the powder laying module. The method utilizes the above system. Compared with existing devices, the present application can dynamically adjust laser scanning parameters to match the material properties of the powder bed, achieve excellent metallurgical densification effect, and fill the gaps in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of selective laser melting additive manufacturing technology, and particularly relates to a system and method for forming continuous gradient material by variable speed laser. BACKGROUND

[0002] With the development of science and technology and the progress of society, people's requirements for the performance of materials are increasing, and traditional single materials or ordinary composite materials have been difficult to meet these needs. Continuous gradient material is a new type of composite material, whose composition and structure change continuously within the material. Such material is composed of two or more materials with different properties, and there is no obvious interface between them. The seamless connection is achieved through the gradual transition of composition. This continuously changing structure enables the material to better exhibit the characteristics of various materials, while avoiding the risk of damage caused by interface problems. The characteristics of continuous gradient material make it have a wide application prospect in many fields such as nuclear energy, electronics, optics, chemistry, electromagnetism, and biomedicine. At present, it has high use value and broad application prospect in many fields such as aerospace, biomedicine, energy engineering, mechanical engineering, electromagnetism, and nuclear engineering. At the same time, the preparation of gradient material is also an international frontier technology.

[0003] Additive manufacturing, as a new manufacturing method, has the unique advantage of building point by point and layer by layer, and is used to prepare continuous gradient material. Among them, the selective laser melting technology has high precision and excellent performance and is widely used.

[0004] At present, the method for preparing continuous gradient material by selective laser melting technology is to use single laser parameters to scan the gradient powder bed. However, it is found in practice that in the gradient powder layer, the melting point, density, and laser absorption rate of the material change with the composition, and the corresponding laser processing parameters and scanning process also change. Therefore, the traditional single laser parameter scanning process cannot realize the metallurgical densification of the specific gradient powder layer. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a system and method for forming continuous gradient material by variable speed laser, which can be used to form continuous gradient material by different selective laser melting equipment, adjust the laser scanning speed according to the physical properties of different powders in the gradient layer, and realize the metallurgical densification of the gradient powder layer.

[0006] The present application adopts the following technical solutions:

[0007] On the one hand, the present application provides a system for forming continuous gradient material by variable speed laser, which comprises a powder laying module, a laser module, a control module, and a workbench:

[0008] The powder laying module is configured to lay a gradient powder layer on the worktable, and a region where the gradient powder layer is located is a powder bed;

[0009] The laser module is configured to emit laser beams with different scanning speeds on the gradient powder layer on the worktable according to regions;

[0010] The control module is configured to divide the powder bed into a plurality of rows and a plurality of columns of feature rectangles, select feature rectangles located in a two-dimensional contour of a slice of the printed part as feature rectangles to be printed, assign print parameters to each feature rectangle to be printed, arrange print directions and sequences of the feature rectangles to be printed, and control the laser module and the powder laying module.

[0011] The control module is in control connection with the powder laying module and the laser module.

[0012] According to any possible implementation of the above, further provided is an implementation, wherein the control module comprises a powder bed division unit, a feature rectangle selection unit, a parameter setting unit, and a path planning unit.

[0013] The powder bed division unit is configured to divide the entire powder bed into a plurality of rows and a plurality of columns of feature rectangles arranged closely.

[0014] The feature rectangle selection unit is configured to select, according to slice analysis of the printed part, feature rectangles located in a two-dimensional contour of a slice as feature rectangles to be printed, and delete other feature rectangles located outside the two-dimensional contour of the slice.

[0015] The parameter setting unit is configured to set a laser scanning speed according to a composition characteristic of a powder layer of each feature rectangle to be printed.

[0016] The path planning unit is configured to arrange a laser scanning sequence of the feature rectangles, and realize planning of a scanning path.

[0017] The powder bed division unit, the feature rectangle selection unit, the parameter setting unit, and the path planning unit are integrated in a controller or a computer.

[0018] According to any possible implementation of the above, further provided is an implementation, wherein a width of the feature rectangle is equal to a laser scanning pitch, and the laser performs single scanning on each feature rectangle only once.

[0019] According to any possible implementation of the above, further provided is an implementation, wherein a length of the feature rectangle is determined through experiments according to a composition characteristic and a gradient distribution of the gradient powder layer, and a fine adjustment of the laser scanning speed is realized by adjusting the length of the feature rectangle.

[0020] According to any possible implementation manner above, further provided is an implementation manner, wherein the control module further comprises a user input interface for inputting powder composition information and adjusting laser scanning parameters.

[0021] In another aspect, the application also provides a method for forming a variable-speed laser-shaped continuous gradient material, which uses the system described above, and the method comprises:

[0022] S1, slicing of a part to be printed: slicing analysis is performed on a part to be printed to generate a two-dimensional contour of the slice;

[0023] S2, division of a powder bed: the entire powder bed is divided into multiple rectangular regions in multiple rows and multiple columns, each rectangular region is a feature rectangle and corresponds to a specific position of the powder bed;

[0024] S3, selection of a feature rectangle: according to the two-dimensional contour of the slice, a feature rectangle located inside the two-dimensional contour is selected as a to-be-printed feature rectangle, and feature rectangles outside the two-dimensional contour are deleted;

[0025] S4, parameter setting and distribution: laser scanning parameters are distributed to each to-be-printed feature rectangle according to the composition of the gradient material;

[0026] S5, optimization of printing order: a printing order is set for each to-be-printed feature rectangle, so that the laser scanning path is as continuous as possible and continuously changes along the gradient direction of the powder bed;

[0027] S6, gradient powder laying: a scraper scrapes the gradient powder into the specified position of the workbench to complete the gradient layer laying;

[0028] S7, laser melting forming: the laser module is turned on, and the to-be-printed feature rectangle is scanned according to the set scanning path and laser scanning parameters, so as to realize the melting forming of the continuous gradient material of the layer;

[0029] S8, repeating steps S3-S7 until the part printing is completed.

[0030] According to any possible implementation manner above, further provided is an implementation manner, wherein a “gradient material-laser scanning parameter” database is first established, corresponding laser scanning parameters are determined through experiments according to the composition and proportion of different gradient materials, and are stored in the database, and in step S4, the control module directly reads the laser scanning parameters from the database according to the composition and proportion of the gradient material.

[0031] According to any possible implementation manner above, further provided is an implementation manner, in step S4, the scanning speed of the compositions at both ends of the gradient material is manually input through the user input interface of the control module, and the parameter setting unit automatically distributes laser scanning parameters to each to-be-printed feature rectangle by using linear interpolation.

[0032] According to any possible implementation manner described above, further provided is an implementation manner, when two adjacent layers are printed, the laser scanning direction is rotated, an acute angle θ formed by the long side of the feature rectangle and a straight line where the powder gradient direction is located is changed, and residual stress generated by printing is reduced.

[0033] According to any possible implementation manner described above, further provided is an implementation manner, the acute angle θ formed by the long side of the feature rectangle and the straight line where the powder gradient direction is located is 0°-90°.

[0034] The present application has the following beneficial effects:

[0035] By precisely controlling the laser scanning speed and path, combining the intelligent segmentation of the powder bed by the computer system and the printing parameter assignment of the feature rectangle, continuous change of the laser scanning speed in the printing process is realized, so that the laser energy and the powder characteristics are optimally matched, the continuous gradient material is more efficiently built, and finally the densification of the continuous gradient material is realized. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Fig. 1 shows the working principle diagram of the laser variable speed of the present application.

[0037] Figure 2 Fig. 2 shows the powder bed segmentation and scanning path diagram of Example 1.

[0038] Figure 3 Fig. 3 shows the feature rectangle selection diagram of Example 1 to be printed.

[0039] Figure 4 Fig. 4 shows the feature rectangle arrangement mode diagram of Example 2.

[0040] Figure 5 Fig. 5 shows the powder bed segmentation and scanning path diagram of Example 2.

[0041] Figure 6 Fig. 6 shows the feature rectangle selection diagram of Example 2 to be printed.

[0042] Figure 7 Fig. 7 shows the physical diagram of the existing technology using a single laser scanning parameter to form a part.

[0043] Figure 8 Fig. 8 shows the physical diagram of the complex part formed by the system and method of the present application using the variable speed laser to form the continuous gradient material.

[0044] In the figure: 1, initial speed of single-channel variable speed laser; 2, feature rectangle; 3, parallel gradient direction; 4, workbench; 5, powder bed; 6, final speed of single-channel variable speed laser; 7, laser module; 8, scanning path; 9, two-dimensional contour; 10, included angle between the laser scanning direction and the gradient direction. DETAILED DESCRIPTION

[0045] The specific embodiments of the present application will be described in detail below with reference to specific drawings. It should be noted that the technical features described in the following embodiments or combinations of technical features should not be considered in isolation, and they can be combined with each other to achieve better technical effects.

[0046] The system for forming continuous gradient material by variable speed laser in the embodiment of the present application comprises a powder laying module, a laser module 7, a control module and a workbench 4:

[0047] The powder laying module is used for laying a gradient powder layer on the workbench 4, and the area where the gradient powder layer is located is a powder bed;

[0048] The laser module 7 is used for emitting laser beams with different scanning speeds on the gradient powder layer on the workbench 4 according to areas;

[0049] The control module is used for dividing the powder bed into a plurality of rows and a plurality of columns of feature rectangles 2, selecting feature rectangles 2 within a two-dimensional contour 9 of a printed part slice as to-be-printed feature rectangles, assigning print parameters to each to-be-printed feature rectangle 2, arranging the print direction and sequence of the to-be-printed feature rectangles 2, and controlling the laser module 7 and the powder laying module;

[0050] The control module is in control connection with the powder laying module and the laser module 7 respectively.

[0051] In one specific embodiment, the control module comprises a powder bed division unit, a feature rectangle selection unit, a parameter setting unit and a path planning unit;

[0052] The powder bed division unit is used for dividing the entire powder bed into a plurality of rows and a plurality of columns of closely arranged feature rectangles 2;

[0053] The feature rectangle selection unit selects feature rectangles 2 located inside a slice two-dimensional contour 9 as to-be-printed feature rectangles according to slice analysis of a printed part, and deletes other feature rectangles 2 located outside the slice two-dimensional contour;

[0054] The parameter setting unit sets the laser scanning speed according to the composition characteristics of the powder layer of each to-be-printed feature rectangle 2;

[0055] The path planning unit is used for arranging the laser scanning sequence of the feature rectangles 2 to realize the planning of the scanning path;

[0056] The powder bed division unit, the feature rectangle selection unit, the parameter setting unit and the path planning unit are integrated in a controller or a computer.

[0057] In one embodiment, the width of the feature rectangle 2 is equal to the laser scanning pitch, and the laser performs a single pass on each feature rectangle 2.

[0058] In one embodiment, the length of the feature rectangle 2 is determined according to the composition characteristics of the gradient powder layer and the gradient distribution, and the numerical range can be determined by experiments; and the fine adjustment of the laser scanning speed is achieved by adjusting the length of the feature rectangle 2.

[0059] In one embodiment, the control module further comprises a user input interface for inputting powder composition information and adjusting laser scanning parameters.

[0060] In one embodiment, the method for continuously forming a gradient material by variable speed laser forming uses the system described above, and the method comprises the following steps:

[0061] S1, slicing the part to be printed: slicing analysis is performed on the part to be printed to generate a two-dimensional contour 9 of the slice;

[0062] S2, powder bed segmentation: the entire powder bed is divided into multiple rectangular regions in multiple rows and multiple columns, each rectangular region being a feature rectangle 2 and corresponding to a specific position of the powder bed;

[0063] S3, feature rectangle 2 selection: according to the two-dimensional contour 9 of the slice, the feature rectangles 2 located inside the two-dimensional contour 9 are selected as the feature rectangles to be printed, and the feature rectangles 2 outside the two-dimensional contour 9 are deleted;

[0064] S4, parameter setting and distribution: according to the composition of the gradient material, laser scanning parameters are assigned to each feature rectangle 2 to be printed;

[0065] S5, printing order optimization: the printing order of each feature rectangle 2 to be printed is set so that the laser scanning path 8 is as continuous as possible and continuously changes along the gradient direction of the powder bed;

[0066] S6, gradient powder laying: the doctor blade lays the gradient powder into the designated position of the workbench 4 to complete the gradient layer laying;

[0067] S7, laser melting forming: the laser module 7 is turned on, and the feature rectangle 2 to be printed is scanned according to the set scanning path 8 and laser scanning parameters, so as to realize the melting forming of the continuous gradient material of the layer;

[0068] S8, repeat steps S3-S7 until the part printing is completed.

[0069] In one specific embodiment, a "gradient material-laser scanning parameter" database can be first established, laser scanning parameters corresponding to different gradient material compositions and proportions are determined through experiments and stored in the database, and in step S4, the control module reads the laser scanning parameters from the database according to the composition and proportion of the gradient material.

[0070] In one specific embodiment, in step S4, the scanning speeds (initial speed 1 and final speed 6) of the compositions at both ends of the gradient material are manually input through the user input interface of the control module, and the parameter setting unit automatically assigns laser scanning parameters to each to-be-printed feature rectangle 2 using linear interpolation.

[0071] In one specific embodiment, when printing adjacent two layers, the laser scanning direction is rotated, and the acute angle θ formed by the long side of the feature rectangle and the straight line on which the powder gradient direction lies is changed to reduce the residual stress generated by printing.

[0072] In one specific embodiment, the acute angle θ formed by the long side of the feature rectangle and the straight line on which the powder gradient direction lies is 0°-90°.

[0073] Technical principles of the present application:

[0074] The melting point difference is an important factor affecting the printing of gradient materials, and it is more advantageous to print gradient materials with a large melting point difference (such as Cu and Fe). The powder with a high melting point requires higher energy input, which requires higher laser power and / or lower scanning speed; the powder with a low melting point requires lower energy input, which requires smaller laser power and / or higher scanning speed. In the gradient powder layer, the powders at different positions require different energy inputs, and the laser scanning speed needs to be gradually increased from the low melting point end to the high melting point end.

[0075] In addition to the melting point difference, the absorption efficiency of the material to the laser also affects the printing effect. The absorption rate of the powder to the laser directly affects the energy absorbed by the powder. If the laser absorption rate is too low, most of the energy will be reflected, and even if the input energy of the laser meets the powder melting requirement, the powder cannot be effectively melted. Therefore, for materials with a large difference in laser absorption rate (the laser absorption rate of Cu is very low), even if the melting point difference is not large, different energy inputs are required, and variable speed scanning can achieve gradually changing energy input on the gradient powder layer.

[0076] In practice, frequent and rapid changes in laser power can negatively impact the lifespan of the laser. Lasers require time to stabilize their output during power changes; frequent and rapid changes can lead to overheating or damage to internal components, shortening the laser's lifespan. Furthermore, when the number of feature rectangles in the gradient direction is large, the laser must continuously and rapidly change its power, which will have some negative effects. Therefore, under current technological conditions, power control is not recommended. However, the possibility of directly controlling the laser power as technology advances cannot be ruled out.

[0077] like Figure 1 As shown, the control module cuts a powder bed of a certain width along the gradient direction 3 into n feature rectangles 2. The width of the powder bed and the width of the feature rectangles 2 together determine the value of n, and the width of the feature rectangles 2 is the laser scanning interval. For each feature rectangle 2, the laser scanning path 8 scans along the longer side, and each feature rectangle 2 is scanned only once. Given an initial speed 1 and a final speed 6, the control module assigns a laser scanning speed value to each feature rectangle based on the value of n, causing the laser scanning speed to continuously gradient from the initial speed 1 to the final speed 6. Next, the control module adjusts the scanning direction and printing order of each feature rectangle 2 to achieve continuous laser scanning and scan path planning, ultimately realizing controllable variable-speed laser scanning along the powder bed gradient direction.

[0078] Example 1

[0079] The length of powder bed 5 is a, the width is b, the side parallel to the gradient direction 3 is the length of powder bed 5, and the side perpendicular to the gradient direction 3 is the width of powder bed 5; the length of the longer side of feature rectangle 2 is n, and the length of the shorter side of feature rectangle 2 is m; the laser scanning direction is parallel to the longer side of feature rectangle 2; the longer side of feature rectangle 2 is parallel to the gradient direction 3.

[0080] like Figure 2 As shown, the control module divides the powder bed 5 into several closely arranged feature rectangles 2. In each row parallel to the gradient direction 3, the number of feature rectangles is... In each column perpendicular to the gradient direction, the number of feature rectangles is... like Figure 1 As shown, for each row of feature rectangles parallel to gradient direction 3, the initial input velocity 1-1 is v1, and the final input velocity 6-1 is v. D Then the scanning speed of the x-th feature rectangle in gradient direction 3 will be set to v. x v x It can be determined by relation (1):

[0081]

[0082] Then, the control module adjusts the scanning direction and scanning sequence of the feature rectangle 2, realizes the continuous scanning of the laser and the planning of the scanning path 8-1, and finally, as shown in Figure 3 , the control module retains the feature rectangle 2 located inside the two-dimensional contour according to the two-dimensional contour 9-1 information of the model, and deletes the feature rectangle 2 located outside the two-dimensional contour.

[0083] Preferably, the short side length m of the feature rectangle 2 can be changed, and the value of m is the scanning interval in the printing parameters.

[0084] Preferably, the long side length n of the feature rectangle 2 can be changed, and different n values can be set according to the different properties of the powder to change the fineness of the change of the laser scanning speed. The smaller the n value is, the smoother the change of the laser scanning speed is.

[0085] Preferably, in addition to the simple linear change of the laser scanning speed, in some application scenarios, other nonlinear change functions can be used to adjust the laser scanning speed according to the specific properties of the powder to further improve the forming effect.

[0086] Embodiment 2

[0087] In the actual additive manufacturing process, in order to reduce the stress generated by printing, the laser scanning direction needs to be rotated after each layer is printed, at this time, the feature rectangle 2 forms an acute angle 10 with the straight line where the gradient direction is located, as shown in Figure 4 . At this time, as shown in Figure 5 , the feature rectangles will be closely arranged to fill a parallelogram, one pair of parallel sides of the parallelogram is parallel to the gradient direction and coincides with one pair of parallel sides of the powder bed 5, and the length of the parallelogram parallel to the gradient direction is the minimum value that meets the above conditions. The feature rectangles in several rows and several columns are closely arranged to fill the parallelogram, and from left to right, they are the first column, the second column, the third column, …, the xth column, and from bottom to top, they are the first row, the second row, the third row, …, the yth row. The speed of the xth column and the yth row will be set as v xy ,v xy which can be determined by the relationship (2):

[0088]

[0089] Where a is the length of the side of the powder bed 5 parallel to the gradient direction 3, b is the length of the side of the powder bed 5 perpendicular to the gradient direction 3; n is the longer side length of the feature rectangle 2, and m is the shorter side length of the feature rectangle 2; v s and v eThe best scanning speeds of the powders at the two ends of the gradient powder bed, respectively. After assigning the parameter values to each feature rectangle, the control module adjusts the scanning direction and scanning order of the feature rectangle 2 to realize continuous scanning of the laser and planning of the scanning path 8-2. Finally, as shown in Figure 6 Fig. 9-2, the control module retains the feature rectangle 2 located inside the two-dimensional contour and deletes the feature rectangle 2 located outside the two-dimensional contour according to the two-dimensional contour 9-2 information of the model.

[0090] Example 3

[0091] When printing the gradient material with Cu10Sn and SS316 at the two ends, respectively, the system and method of the present application are used to input the best process parameters of Cu10Sn and the best process parameters of SS316, respectively, and the process parameters include the laser scanning speed. A complex part is formed by inputting different laser energy densities to different powder bed regions, as shown in Figure 8 Fig. 9-2, the control module retains the feature rectangle 2 located inside the two-dimensional contour and deletes the feature rectangle 2 located outside the two-dimensional contour according to the two-dimensional contour 9-2 information of the model.

[0092] Comparative Example

[0093] When printing the gradient material with Cu10Sn and SS316 at the two ends, respectively, the system and method of the present application are used to input the best process parameters of Cu10Sn and the best process parameters of SS316, respectively, and the process parameters include the laser scanning speed. A complex part is formed by inputting different laser energy densities to different powder bed regions, as shown in Figure 7 Fig. 9-2, the control module retains the feature rectangle 2 located inside the two-dimensional contour and deletes the feature rectangle 2 located outside the two-dimensional contour according to the two-dimensional contour 9-2 information of the model.

[0094] Comparison Figure 8 and Figure 7 It can be seen that the present application has significant advantages when forming gradient materials with large differences in melting point or large differences in laser absorption rate: high forming quality, high strength, and the ability to form complex parts.

[0095] The present application uses modeling to assign printing parameters to feature rectangles and select feature rectangles by using a control module, so that the scanning speed of the laser continuously changes in the composition gradient direction of the powder bed, so that the laser energy density adapts to the powder layer properties, and realizes complete densification and alloying process control of the gradient powder layer. Compared with existing devices, the present application can dynamically adjust the laser scanning parameters to match the material properties of the powder bed, achieve excellent metallurgical densification effect, and fill the gaps in the prior art.

[0096] Although several embodiments of the present application have been described herein, those skilled in the art will understand that changes can be made to the embodiments described herein without departing from the spirit of the present application. The above examples are only exemplary and should not be used as a limitation on the scope of the present application.

Claims

1. A system for variable speed laser forming of a continuously graded material, the system comprising: The system comprises a powder laying module, a laser module, a control module and a workbench: The powder laying module is configured to lay a gradient powder layer on the workbench, and the area where the gradient powder layer is located is a powder bed; The laser module is configured to emit laser beams with different scanning speeds on the gradient powder layer on the workbench according to areas; The control module is configured to divide the powder bed into multiple rows and multiple columns of feature rectangles, select feature rectangles within a two-dimensional contour of a printed part slice as to-be-printed feature rectangles, assign printing parameters to each to-be-printed feature rectangle, arrange the printing direction and sequence of the to-be-printed feature rectangles, and control the laser module and the powder laying module; The control module is in signal connection with the powder laying module and the laser module respectively; The control module comprises a powder bed division unit, a feature rectangle selection unit, a parameter setting unit and a path planning unit; The powder bed division unit is configured to divide the entire powder bed into multiple rows and multiple columns of closely arranged feature rectangles; The feature rectangle selection unit selects feature rectangles located inside a two-dimensional contour of a printed part slice as to-be-printed feature rectangles according to slice analysis, and deletes feature rectangles located outside the two-dimensional contour; The parameter setting unit sets laser scanning speed and laser power according to the composition characteristics of the powder layer of each to-be-printed feature rectangle; The path planning unit is configured to arrange the laser scanning sequence of the feature rectangles, and realize planning of the scanning path; The powder bed division unit, the feature rectangle selection unit, the parameter setting unit and the path planning unit are integrated in a controller or a computer; The width of the feature rectangle is equal to the laser scanning pitch, and the laser performs single scanning on each feature rectangle only once; the length of the feature rectangle is determined through experiments according to the composition characteristics and gradient distribution of the gradient powder layer; and fine adjustment of the laser scanning speed is realized by adjusting the length of the feature rectangle; The modeling is combined with the control module to assign printing parameters to the feature rectangles and select the feature rectangles, so that the scanning speed of the laser continuously changes in the composition gradient direction of the powder bed.

2. The system for variable speed laser forming of continuously graded materials of claim 1, wherein, The control module further comprises a user input interface for inputting powder composition information and adjusting laser scanning parameters.

3. A method of variable speed laser forming a continuously graded material, characterized by, The method uses the system according to any one of claims 1-2, and the method comprises: S1, printed part slice: performing slice analysis on a part to be printed to generate a two-dimensional contour of the slice; S2, powder bed division: dividing the entire powder bed into multiple rows and multiple columns of rectangular areas, each rectangular area being a feature rectangle and corresponding to a specific position of the powder bed; S3, feature rectangle selection: selecting feature rectangles located inside the two-dimensional contour of the slice as to-be-printed feature rectangles according to the two-dimensional contour of the slice, and deleting feature rectangles outside the two-dimensional contour; S4, parameter setting and distribution: distributing laser scanning parameters to each to-be-printed feature rectangle according to the gradient material composition; S5, printing sequence optimization: setting a printing sequence for each to-be-printed feature rectangle, so that the laser scanning path is continuous and continuously changes along the gradient direction of the powder bed; S6, gradient powder laying: a doctor blade lays gradient powder into a specified position of the workbench to complete gradient layer laying; S7, laser melting forming: turn on the laser module, scan the to-be-printed feature rectangle according to the set scanning path and laser scanning parameters, and realize the melting forming of the continuous gradient material of the layer; S8, repeat steps S3-S7 until the part printing is completed; In step S4, the scanning speed of the components at both ends of the gradient material is manually input through the user input interface of the control module, and the parameter setting unit automatically assigns laser scanning parameters to each to-be-printed feature rectangle by using linear interpolation method; The printing parameter assignment of the feature rectangle and the selection of the feature rectangle by using the modeling and the control module make the scanning speed of the laser continuously change in the component gradient direction of the powder bed.

4. The method of claim 3, wherein, When printing adjacent two layers, the laser scanning direction is rotated, the acute angle θ formed by the long side of the feature rectangle and the straight line where the powder gradient direction is located is changed, and the residual stress generated by printing is reduced.

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