Printing path optimization method based on selective laser melting

Abstract

The invention discloses a printing path optimization method based on selective laser melting. Obtaining a three-dimensional model of the workpiece, and performing slicing operation on the three-dimensional model to obtain a slicing file; generating a filling path according to the graph contour of each layer in the slice file, performing complexity judgment on each layer of filling path by taking the number of inflection points in the filling path as a criterion, and determining a filling mode of the current filling path based on a judgment result; storing the filling paths and the corresponding filling modes in brother nodes of the balanced binary tree; performing path optimization on the printing sequence of each layer of graph contour by using an improved ant colony algorithm; and traversing the balanced binary tree to obtain a filling path, and printing the workpiece in combination with the contour path. According to the invention, the scanning path of the laser is optimized, so that the manufacturing efficiency and the printing quality of selective laser melting are improved.

Description

Technical Field

[0001] The invention relates to the technical field of selective laser melting, and in particular to a printing path optimization method based on selective laser melting. Background Art

[0002] Selective Laser Melting (SLM) technology is an additive manufacturing (AM) process that uses a laser beam to melt metal powder layer by layer to build complex three-dimensional structures. SLM technology is widely used in high-end manufacturing fields such as aerospace, medical devices, and automobile manufacturing because it can manufacture high-precision and high-complexity metal parts. However, the printing path planning in the SLM process has a crucial impact on the quality, manufacturing efficiency, and cost of the final product. Optimizing the printing path aims to reduce manufacturing time, improve surface quality, control heat input, and reduce residual stress and deformation. Optimizing the path can significantly improve the efficiency of the SLM process and the quality of the finished product, thereby promoting the industrial application of this technology.

[0003] To solve the printing path optimization problem, the researchers improved the ant colony algorithm and used the principle of ant foraging to optimize the contour path, shortening the jump distance of the laser when scanning the contour; they also improved the traditional filling method and adopted a method that meets the process preparation requirements for workpieces of different complexity. Commonly used scanning methods include parallel line scanning, serpentine scanning, checkerboard scanning, etc.

[0004] However, with the increasing complexity and sophistication of product design in the fields of aviation, aerospace, and medical, the structures of parts have become more complex in terms of internal and external geometry, and the requirements for manufacturing precision have become more stringent, making the above-mentioned optimization methods unable to meet the needs in terms of optimization efficiency or adaptability.

[0005] Therefore, how to provide a laser scanning path optimization method that can improve the efficiency of selective laser melting printing is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a printing path optimization method based on selective laser melting to optimize the scanning path of the laser, thereby improving the manufacturing efficiency of selective laser melting.

[0007] The present invention provides a printing path optimization method based on selective laser melting, comprising the following steps:

[0008] S1: obtaining a three-dimensional model of a workpiece, and performing a slicing operation on the three-dimensional model to obtain a slicing file;

[0009] S2: Generate a filling path according to the graphic outline of each layer in the slice file, use the number of inflection points in the filling path as a criterion to judge the complexity of each layer of the filling path, and determine the filling method of the current filling path based on the judgment result, wherein the filling method is a specific path pattern for filling the inside of the graphic outline of each layer;

[0010] S3: storing the filling path and the corresponding filling method in a brother node of the balanced binary tree;

[0011] S4: Using the improved ant colony algorithm to optimize the printing order of each layer of graphic contour;

[0012] S5: traverse the balanced binary tree to obtain a filling path, and print the workpiece in combination with the contour path.

[0013] Preferably, the step of determining the complexity of each layer of the filling path using the number of inflection points in the filling path as a criterion in S2 includes:

[0014] S21: setting an inflection point critical value according to the complexity of the filling path in the three-dimensional model of the workpiece;

[0015] S22: Determine whether the number of inflection points in the filling path is greater than a critical value, if so, select the first filling method, if not, select the second filling method; wherein,

[0016] The first filling method includes one or more of the following: checkerboard scanning filling, cross filling, and honeycomb filling;

[0017] The second filling method includes one or more of the following: parallel line scanning filling and serpentine scanning filling.

[0018] Preferably, the balanced binary tree is as follows from the root node downwards:

[0019] The first layer where the root node is located is used to store the workpiece slice file name, the second layer is used to store the layer number of the printed layer, the third layer is used to store the graphic outline information of the layer where the parent node is located, and the fourth layer is used to store the fill path and corresponding fill method of the corresponding layer.

[0020] Preferably, it also includes: during the filling process, performing data insertion, deletion or rotation operations on the left and right subtrees in the balanced binary tree according to the printing progress and requirements, and making the absolute value of the balance factor after the operation meet the constraint conditions; at the same time, updating and storing the laser scanning path information, and performing a filling scan for the next layer of printing path.

[0021] Preferably, the method further includes: in the filling process, optimizing the stepping logic of the pixels in the linear scan line by using the Bresenham algorithm, determining the position of the next pixel by increasing the step length, and generating a linear pixel printing sequence.

[0022] Preferably, the method further includes: in the filling process, fitting and optimizing the printing path of the pixel points in the curve scanning line using the Bezier curve, and generating a curve pixel point printing sequence by optimizing the position of the control point and calculating the fitting error.

[0023] Preferably, each layer in the slice file includes multiple graphics, and the printing order of the multiple graphic contours of each layer is optimized by using an improved ant colony algorithm.

[0024] Preferably, the step of optimizing the printing order of multiple graphic outlines of each layer by using the improved ant colony algorithm in S4 includes:

[0025] S41: Read the coordinates of the two-dimensional contour points of multiple graphic contours in the current layer of the slice file and initialize the distance matrix;

[0026] S42: Initialize the parameters of the ant colony algorithm, and initialize the path records and the coordinates of the unvisited points in combination with the distance matrix;

[0027] S43: Initialize the greedy algorithm solution to the initial solution, create a list to store the coordinates of the currently unvisited points and create an ant_paths array P to store the path of each ant;

[0028] S44: Determine the relationship between Greedy_alpha and Cumsum(P). If Greedy_alpha is large, the greedy strategy is adopted. Otherwise, the roulette strategy is adopted. P is the probability of judging that an ant moves to the next point in the ant colony algorithm.

[0029] S45: Update the pheromone matrix and calculate the current optimization path;

[0030] S46: Repeat S42-S45 until the maximum number of iterations is reached, and find the optimal path based on the optimized path of each round of iteration.

[0031] Compared with the prior art, it has the following beneficial effects:

[0032] The present invention proposes a printing path optimization method based on selective laser melting. First, a filling method with higher adaptability is selected by setting the complexity. The appropriate filling strategy can be automatically selected according to different parts of the workpiece, which helps to improve printing quality and efficiency.

[0033] Secondly, the path information and scanning mode are stored in a subtree of the balanced binary tree, and the balance factor is used to ensure that each scanning path matches the scanning mode. During the filling process, the Bresenham algorithm and Bezier curve are used to optimize the filling to further improve the printing accuracy and smoothness.

[0034] Finally, the improved ant colony algorithm is used to optimize the contour path and shorten the jump distance of the single-layer scanning laser.

[0035] In summary, the optimized printing path of the present invention reduces the jump distance of the laser and improves the filling scanning rate and printing quality of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on the provided drawings without creative work.

[0037] Figure 1 A flow chart of a printing path optimization method based on selective laser melting provided in an embodiment of the present invention;

[0038] Figure 2 A two-dimensional cross-sectional view of a manufactured structural member provided for one embodiment of the present invention;

[0039] Figure 3 A three-dimensional model diagram of a manufacturing structure provided in an embodiment of the present invention;

[0040] Figure 4 A processing path diagram for manufacturing a structural part provided in a certain embodiment of the present invention;

[0041] Figure 5 A flowchart for executing a printing path optimization method based on selective laser melting provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] like Figure 1As shown, the printing path optimization method based on selective laser melting disclosed in the embodiment of the present invention includes the following steps: S1: obtaining a three-dimensional model of a workpiece, and slicing the three-dimensional model to obtain a slicing file; S2: generating a filling path according to the graphic contour of each layer in the slicing file, and judging the complexity of each layer of the filling path based on the number of inflection points in the filling path, and determining the filling method of the current filling path based on the judgment result, and the filling method is a specific path pattern for filling the inside of each layer of the graphic contour; S3: storing the filling path and the corresponding filling method in the brother node of the balanced binary tree; S4: using the improved ant colony algorithm to optimize the path of the printing order of each layer of the graphic contour; S5: traversing the balanced binary tree to obtain the filling path, and printing the workpiece in combination with the contour path.

[0044] In one embodiment, the three-dimensional model of the workpiece is an STL model, which is sliced ​​in Magics to generate a slice file in SLC format.

[0045] In this embodiment, the SLC slice file in S1 is imported, and each slice layer can be controlled and displayed separately, and the control method includes dragging. The slice status of each layer can be checked by dragging the layer slider on the host computer main interface.

[0046] In one embodiment, the step of determining the complexity of each layer of filling path by using the number of inflection points in the filling path as a criterion in S2 includes:

[0047] S21: setting an inflection point critical value according to the complexity of the filling path in the three-dimensional model of the workpiece;

[0048] S22: Determine whether the number of inflection points in the filling path is greater than a critical value, if so, select the first filling method, if not, select the second filling method; wherein,

[0049] The first filling method includes one or more of the following: checkerboard scanning filling, cross filling, honeycomb filling, which is suitable for the printing process of workpieces with higher complexity;

[0050] The second filling method includes one or more of the following: parallel line scanning filling, serpentine scanning filling, and is suitable for the printing process of workpieces with lower complexity.

[0051] In this embodiment, Figure 2-3 As shown, the two-dimensional model of the workpiece contains rectangles, semicircular arcs, and irregular crescent-shaped figures. The critical value is set to 3 based on the determination of the complexity of the filling path. The cube and the stretching parts adopt the checkerboard scanning method, and the semicircular and crescent-shaped prints choose the serpentine scanning method.

[0052] In one embodiment, the step of storing the filling path and the corresponding filling method in the brother node of the balanced binary tree in S3 includes: the left child node stores the filling path, and the right child node stores the corresponding filling method. After the laser scans a certain section of the path, the current filling status will be displayed in the two-dimensional preview view of the host computer. After the scanning is completed, the subtree is deleted, and the height difference is ensured by using the balance factor limit so that the corresponding path and filling method match.

[0053] In this embodiment, the balanced binary tree is as follows from the root node downwards:

[0054] The first layer where the root node is located is used to store the workpiece slice file name, the second layer is used to store the layer number of the printed layer, the third layer is used to store the graphic outline information of the layer where the parent node is located, and the fourth layer is used to store the fill path and corresponding fill method of the corresponding layer.

[0055] In this embodiment, the height of the balanced binary tree is defined as 4, the root node stores information such as the slice file name, and the child nodes store layer information, path complexity information, and filling method. During the filling process, the constraint condition that the absolute value of the balance factor does not exceed 1 is used to ensure that the filling method and the path information are perfectly matched.

[0056] In one embodiment, it also includes: during the filling process, data insertion, deletion or rotation operations are performed on the left and right subtrees in the balanced binary tree according to the printing progress and requirements, and the absolute value of the balance factor after the operation satisfies the constraint conditions; at the same time, the laser scanning path information is updated and stored, and a filling scan of the next layer of printing path is performed.

[0057] During the specific execution, the laser scans and fills the corresponding path in a certain node, then deletes the node in the balanced binary tree, and uses the balance factor to ensure that each path has a corresponding filling method.

[0058] In one embodiment, Figure 5 As shown, it also includes: during the filling process, the stepping logic of the pixel points in the straight scan line is optimized using the Bresenham algorithm, the position of the next pixel is determined by increasing the step size, and a straight line pixel point printing sequence is generated, thereby improving the calculation efficiency of the straight line pixel points.

[0059] In this embodiment, the Bresenham algorithm mainly avoids floating point operations, reduces multiplication operations, and introduces decision variables to determine the pixel position of the next step:

[0060] Determine the filling method: determine the straight line information in the path according to the corresponding filling method of each layer in S2.

[0061] Initialize variables: determine the starting point of the filling path and calculate the difference between the horizontal and vertical coordinates, determine the direction of each increment (step length) and initialize the decision variable ρ.

[0062] Iteratively generate filling path points: determine the coordinates of the next filling path point based on the decision variable ρ and update the decision variable.

[0063] Generate straight lines for scan paths: Generate path segments based on calculated path points to optimize the straight line portions in the selected area laser melting fill path.

[0064] In one embodiment, Figure 5 As shown, it also includes: in the filling process, using Bezier curves to fit and optimize the printing path of pixel points in the curve scanning line, generating a curve pixel point printing sequence by optimizing the position of the control point and calculating the fitting error, so that the curve filling is smoother, the filling density is more uniform and the printing time is reduced.

[0065] In this embodiment, a set of control points are defined using a Bezier curve, and the curve path in the filling process is optimized by sampling scan line data, selecting control points, and calculating fitting errors:

[0066] Selection of curve control points: Select and adjust the position of control points according to the outline of the printed workpiece and the filling strategy in S4

[0067] Selection of the number of curve segments: According to the printing accuracy requirements, select an appropriate number of curve segments to balance the calculation complexity and path smoothness.

[0068] Path smoothing: On the generated Bezier curve, further smooth the path to reduce the sharp acceleration and deceleration of the print head and improve the printing quality.

[0069] This embodiment achieves the following goals:

[0070] Plane filling path optimization: When printing plane filling, use Bezier curves to generate smooth filling paths, reduce the number of acceleration and deceleration times of the print head, and improve surface quality.

[0071] Surface filling path optimization: When printing complex surfaces, use Bezier curves to generate surface filling paths to ensure uniform filling density and reduce printing defects.

[0072] Local path optimization: In local areas that require special precision, Bezier curves are used to optimize local paths to improve printing accuracy and surface quality.

[0073] In one embodiment, each layer in the slice file includes multiple graphics, and the printing sequence of the multiple graphic outlines of each layer is optimized by using an improved ant colony algorithm.

[0074] In one embodiment, the step of optimizing the printing order of multiple graphic outlines of each layer by using the improved ant colony algorithm in S4 includes:

[0075] S41: Perform environment preparation and timing function operations, read the coordinates of the two-dimensional contour points of multiple graphic contours in the current layer of the slice file and initialize the distance matrix; when executing specifically, Figure 2-4 A center point is extracted from each graphic contour in each layer of the two-dimensional model, and the coordinate information of the center point is imported into the distance matrix.

[0076] S42: Initialize the parameters of the ant colony algorithm, set the pheromone matrix and the distance matrix to initialize the path records and the coordinates of the unvisited points; in the specific execution, the ant colony algorithm parameters and the value of Greedy_alpha are set as shown in Table 1 below:

[0077] Table 1 Experimental parameters of improved algorithm

[0078] Number of ants num_ants 50 Number of iterations num_iterations 200 Pheromone initialization value pheromone_initial 1 Pheromone volatility factor pheromone_decay 0.1 Pheromone importance factor alpha 1 Heuristic function importance factor beta 5 Greedy algorithm weight factor greedy_alpha 0.3

[0079] S43: Initialize the greedy algorithm solution as the initial solution, create a list to store the coordinates of the currently unvisited points and create an ant_paths array P to store the path of each ant; in the specific execution, use the greedy strategy to select the initial point, combine the pre-processing path of the laser to select the processing starting point, and the array is used to store the ant's path.

[0080] S44: Determine the relationship between Greedy_alpha and Cumsum(P). If Greedy_alpha is large, the greedy strategy is adopted, otherwise the roulette strategy is adopted, where P is the probability of the ant moving to the next point in the ant colony algorithm; in the specific execution, the specific parameters use the values ​​shown in Table 1, where the value of the weight factor is 0.3, which is used to determine the strategy of the ant colony's next move. Improve the slow convergence speed of the ant colony algorithm and the problem that the greedy strategy easily falls into the local optimal solution and cannot be backtracked.

[0081] S45: Update the pheromone matrix and calculate the current optimization path;

[0082] S46: Repeat S42-S45 until the maximum number of iterations is reached, and the optimal path is obtained based on the optimized path of each iteration; in the specific execution, when the number of loops reaches 200 set by num_iterations, the length of the optimal path in 200 times is counted in combination with the function in S45.

[0083] S47: Data two-dimensional visualization, using the timing function to record the processing time; during specific execution, the contour path diagram optimized by the improved ant colony algorithm is shown in the figure below. Figure 4 shown.

[0084] The above is a detailed introduction to a printing path optimization method based on selective laser melting provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technicians in this field, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0085] In this article, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

Claims

1. A printing path optimization method based on selective laser melting, characterized in that: The steps include: S1: obtaining a three-dimensional model of a workpiece, and performing a slicing operation on the three-dimensional model to obtain a slicing file; S2: Generate a filling path according to the graphic outline of each layer in the slice file, use the number of inflection points in the filling path as a criterion to judge the complexity of each layer of the filling path, and determine the filling method of the current filling path based on the judgment result, wherein the filling method is a specific path pattern for filling the inside of the graphic outline of each layer; S3: storing the filling path and the corresponding filling method in a brother node of the balanced binary tree; S4: using the improved ant colony algorithm to optimize the contour path of the printing order of each layer of graphic contour; S5: traverse the balanced binary tree to obtain a filling path, and print the workpiece in combination with the contour path.

2. The printing path optimization method based on selective laser melting according to claim 1, characterized in that: The step of determining the complexity of each layer of the filling path using the number of inflection points in the filling path as a criterion in S2 includes: S21: setting an inflection point critical value according to the complexity of the filling path in the three-dimensional model of the workpiece; S22: Determine whether the number of inflection points in the filling path is greater than a critical value, if so, select the first filling method, if not, select the second filling method; wherein, The first filling method includes one or more of the following: checkerboard scanning filling, cross filling, and honeycomb filling; The second filling method includes one or more of the following: parallel line scanning filling and serpentine scanning filling.

3. The printing path optimization method based on selective laser melting according to claim 1, characterized in that: The balanced binary tree is as follows from the root node downwards: The first layer where the root node is located is used to store the workpiece slice file name, the second layer is used to store the layer number of the printed layer, the third layer is used to store the graphic outline information of the layer where the parent node is located, and the fourth layer is used to store the fill path and corresponding fill method of the corresponding layer.

4. The printing path optimization method based on selective laser melting according to claim 1, characterized in that: Also includes: During the filling process, data insertion, deletion or rotation operations are performed on the left and right subtrees of the balanced binary tree according to the printing progress and requirements, and the absolute value of the balance factor after the operation satisfies the constraint conditions; at the same time, the laser scanning path information is updated and stored, and the filling scan of the next layer of printing path is performed.

5. The printing path optimization method based on selective laser melting according to claim 1, characterized in that: Also includes: During the filling process, the Bresenham algorithm is used to optimize the stepping logic of the pixels in the linear scan line, and the position of the next pixel is determined by increasing the step size to generate a linear pixel printing sequence.

6. The printing path optimization method based on selective laser melting according to claim 1, characterized in that: Also includes: During the filling process, the Bezier curve is used to fit and optimize the printing path of the pixel points in the curve scan line. By optimizing the position of the control point and calculating the fitting error, the curve pixel point printing sequence is generated.

7. The printing path optimization method based on selective laser melting according to claim 1, characterized in that: Each layer in the slice file includes multiple graphics, and the printing sequence of the multiple graphic outlines of each layer is optimized by using an improved ant colony algorithm.

8. The printing path optimization method based on selective laser melting according to claim 7, characterized in that: The step of using the improved ant colony algorithm to optimize the printing order of multiple graphic outlines of each layer in S4 includes: S41: Read the coordinates of the two-dimensional contour points of multiple graphic contours in the current layer of the slice file and initialize the distance matrix; S42: Initialize the parameters of the ant colony algorithm, and initialize the path records and the coordinates of the unvisited points in combination with the distance matrix; S43: Initialize the greedy algorithm solution to the initial solution, create a list to store the coordinates of the currently unvisited points and create the ant_paths array to store the path of each ant; S44: Determine the relationship between Greedy_alpha and Cumsum(P). If Greedy_alpha is large, the greedy strategy is adopted. Otherwise, the roulette strategy is adopted. P is the probability of judging that an ant moves to the next point in the ant colony algorithm. S45: Update the pheromone matrix and calculate the current optimization path; S46: Repeat S42-S45 until the maximum number of iterations is reached, and find the optimal path based on the optimized path of each round of iteration.

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