Micro-area 3D printing forming method

Abstract

The invention relates to the technical field of metal 3D printing, and discloses a micro-region 3D printing forming method in order to solve the technical problems of part upwarp, performance reduction and the like caused by large heat accumulation in the printing process due to too short scanning line segments of a micro-region, an entity filling region is divided into a region A and a region B, and the area of the region A is larger than that of the region B; the area B comprises an area C of the tip, a plurality of sub-areas are divided in the area A, filling lines are set for the sub-areas and the area B respectively, included angles exist between the filling lines of the adjacent sub-areas and the filling lines of the sub-areas adjacent to the area B, and overlapping areas are arranged. And the included angle lambda between the filling line in the region B and the horizontal edge is 0-30 degrees or 150-180 degrees. A deflection angle of 5 degrees to 60 degrees exists in the sub-areas of the upper printing layer and the lower printing layer which are adjacent to each other, and deflection of 1 mm to 10 mm exists in the X-axis direction and the Y-axis direction. And by optimizing a scanning strategy, the heat enrichment phenomenon is reduced, and the printing quality of a micro area and the stability of product performance are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of metal 3D printing, and in particular to a micro-area 3D printing forming method. Background Art

[0002] Laser selective melting forming technology (3D printing) is based on the principles of layer-by-layer slicing, linear filling, layer-by-layer scanning and stacking. For any part with specific geometric features, its three-dimensional geometric structure must first be converted into a series of two-dimensional plane graphics through slicing software, and then these two-dimensional graphics are filled according to a specific algorithm. After that, the laser scans line by line and layer by layer according to the set filling path under computer control, combined with the process of layer-by-layer powder laying and layer-by-layer sintering, and finally generates a complete three-dimensional entity.

[0003] 3D printing technology is particularly suitable for the rapid manufacture of parts with complex structures. However, in actual engineering applications, the feasibility of the 3D printing process must be fully considered when forming three-dimensional structures. For example, when placing parts, hanging positions should be avoided as much as possible to reduce the generation of sharp edges and corners. After the parts are adjusted and placed and sliced, sharp corners often appear in the two-dimensional plane graphics. For such sharp corners, traditional 3D printing software often generates a large number of short filling lines when filling, especially line segments less than 1 mm in length. When the laser beam scans along these short filling lines, the adjacent short filling lines will be scanned continuously in a very short time due to the extremely fast scanning speed. Due to the extremely high energy of the laser beam, heat accumulates rapidly in these tiny areas, and there is a lack of sufficient heat dissipation time between adjacent short filling lines, resulting in heat concentration in the sharp corners, which in turn causes the area to bulge above the powder spreading plane. As the problem worsens, it may cause serious warping of the parts, affecting product performance, and may make it impossible to smoothly carry out subsequent powder spreading operations. This problem limits the development and application of 3D printing technology. Summary of the invention

[0004] The purpose of the present invention is to provide a micro-area 3D printing forming method to solve the technical problems such as part warping and performance degradation caused by the short scanning line segment of the micro-area during the laser selective melting forming process, which leads to a large amount of heat accumulation during the printing process.

[0005] To achieve the above object, the present invention provides a micro-area 3D printing forming method, wherein a three-dimensional digital model of a structure with a formed angle adjusted is imported into a laser selective melting forming software, and sliced ​​according to a predetermined thickness d to form a plurality of printed layers for laser sintering; the printed layers are formed with an out-of-bounds area where the upper layer exceeds the lower layer, a solid filling area located in the middle of each layer as a main structure, and an upper surface area located on the other side of the solid filling area, and a scanning strategy for the solid filling area is set:

[0006] The solid filling area is divided into area A and area B. The area of ​​area A is larger than that of area B. Area B includes area C located at the sharp top. The angle of area C is defined as θ, θ<45°; the length of area B is defined as L1, 1mm<L1<10mm; the division of area B can effectively identify the tiny area in the middle solid filling area to avoid dense and short filling lines in the area. At the same time, by defining the value of L1, the area of ​​the tiny area is reduced, the forming time of the laser beam in area B is shortened, and the forming efficiency is improved. In this way, the forming quality of the tiny area can be ensured without reducing the printing efficiency.

[0007] By dividing the A region into multiple sub-regions and reducing the length of the internal filling line, the heat accumulation during laser sintering is reduced and the stress during the forming process is reduced.

[0008] Filling lines are set in the sub-area and area B respectively. There is an angle between the filling lines of adjacent sub-areas and the sub-area adjacent to area B, and there is an overlapping area of ​​the filling lines. The overlapping area effectively avoids the shrinkage of the filling lines during scanning, prevents the discontinuity of the scanning lines, and thus reduces forming defects such as holes and cracks.

[0009] The angle between the fill line in the B region and the horizontal edge is defined as λ, 0°<λ<30° or 150°<λ<180°; by defining the angle λ, the phenomenon of short scanning lines in the B region is effectively avoided, especially at the tip of the B region.

[0010] There is a deflection angle between the sub-areas of the upper and lower adjacent printing layers, and the deflection angle ranges from 5° to 60°;

[0011] The sub-areas of the upper and lower adjacent slice layers also have an offset distance of 1mm to 10mm in the X-axis and Y-axis directions to avoid complete overlap of the filling lines, thereby reducing the generation of forming defects such as pores, inclusions and microcracks during the printing process.

[0012] By re-dividing the filling area of ​​the middle entity of the tiny area, the problem of short and dense filling lines in the tip area in the traditional filling strategy was successfully solved. Most of the area is divided into area A, while area B occupies a smaller area. The further subdivision of area A divides the filling lines into multiple independent sub-areas, reducing the scanning length of the laser beam in each sub-area, thereby reducing the stress generated during the printing process and reducing the risk of deformation and cracks. Although the scanning directions of these sub-areas are different, the overlap of some areas avoids the problem of isolated forming caused by stress and achieves effective combination between different areas. In addition, the filling lines in area A do not overlap between adjacent layers, but are staggered, so that the filling defects of the upper layer can be repaired during the printing process of subsequent layers. For the design of area B, the angle setting between the filling line and the horizontal line effectively eliminates the phenomenon of short and dense filling lines. For the tip area, a single or multiple longer filling lines are designed to avoid feature loss caused by insufficient laser beam coverage. The setting of the laser delay parameter ensures that the occasional short filling lines have enough time to dissipate heat, reducing heat accumulation. By partitioning the middle solid filling area, the laser sintering parameters of area A and area B can be adjusted separately to ensure fast and efficient forming of area A. At the same time, since the area of ​​area B is small, even if the laser delay is set, it will not significantly affect the overall forming efficiency. This method avoids the significant reduction in efficiency when adjusting the laser delay or sintering parameters in the entire solid filling area, and successfully achieves a balance between forming efficiency and forming quality in a small area.

[0013] Preferably, the predetermined thickness d ranges from 0.01 to 0.2 mm.

[0014] Preferably, the sub-region is in the shape of a regular hexagon; the side length L2 of the regular hexagon is defined as 5mm<L2<50mm.

[0015] Furthermore, if θ<2°, the short filling line in the C region is cancelled and filled with a long filling line, and the long filling line is not parallel to other filling lines in the B region, so as to effectively reduce the accumulation of heat.

[0016] Furthermore, in area B, if the length of two or more adjacent filling lines is less than 2 mm, the laser delay strategy is enabled:

[0017] After the laser beam completes scanning of a short filling line, the galvanometer deflects to the next filling line, and the laser delays for k milliseconds. After the delay, the laser scans along the filling line again; the delay process continues until the entire scanning of area B is completed to optimize the laser scanning stability, prevent overheating and forming defects, reduce heat accumulation, and reduce the occurrence of warping and poor metallurgy.

[0018] Furthermore, the spacing of the filling lines in the sub-area is defined as t1, 0.01<t1<0.3mm; the spacing of the filling lines in the B area is defined as t2, 0.01<t2<0.3mm.

[0019] Furthermore, supports are added in the out-of-bounds area to avoid heat accumulation due to improper parameter settings. By setting supports, heat can be effectively transferred to the forming substrate and dissipated through the substrate, thereby avoiding heat accumulation.

[0020] Preferably, the width of the overlapping area ranges from 0.01 mm to 0.2 mm.

[0021] The micro-area 3D printing forming method provided by the present invention has the following advantages:

[0022] The present invention solves the problem of product warping and performance degradation caused by short scanning line segments and heat enrichment in the micro-area during laser selective melting forming by secondary division of the solid filling area in the middle of the micro-area. By dividing the solid filling area into area A and area B, and further subdividing area A, the length and direction of the scanning line are optimized, the heat accumulation in the laser sintering process is reduced, and the stress and deformation risk in the forming process are reduced. For the special design of area B, by defining the angle between the filling line and the horizontal line, the phenomenon of dense and short filling lines is effectively avoided, especially at the tip, the long filling line design prevents the loss of features. At the same time, the setting of the laser delay parameter provides sufficient heat dissipation time for the short filling line, reducing heat enrichment. There is an offset and angle misalignment between the filling lines between the upper and lower adjacent printing layers, which further reduces the generation of forming defects such as holes, inclusions and microcracks. This method ensures fast and efficient sintering of area A, and the delay setting of area B will not significantly affect the forming efficiency due to its small area, taking into account both the forming efficiency and the forming quality of the micro-area. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A three-dimensional diagram of the inclined triangular structure provided by the present invention;

[0024] Figure 2 A schematic diagram of the forming and placement angles of the triangular structure provided by the present invention;

[0025] Figure 3 A cross-sectional view of a triangular structure provided by the present invention;

[0026] Figure 4 A schematic diagram of the sliced ​​layers of the triangular structure provided by the present invention;

[0027] Figure 5 The present invention provides Figure 4 Model diagram after slicing and layering abstraction;

[0028] Figure 6 A partition boundary diagram for the abstract model provided by the present invention;

[0029] Figure 7 The present invention provides Figure 6 A top view of the N+1th layer partitioning strategy;

[0030] Figure 8 A top view of the filling line form in the middle solid filling area of ​​the N+1th layer provided by the present invention;

[0031] Fig. 9 This is a top view of the filling line form in the middle solid filling area of ​​the N+2th layer provided by the present invention.

[0032] In the figure: 10, triangle; 11, sharp tiny area; 21, first out-of-bounds area; 22, first dividing line; 23, upper surface area; 24, second dividing line; 25, solid filling area. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] The present invention is described by taking an inclined sharp triangular structure as an example, which is defined as a triangular body 10. Figure 1 As shown, one side of the triangle 10 is a sharp triangle, which is tilted upward. For the convenience of explanation, according to the structural characteristics of the parts, the present invention adopts vertical forming, such as Figure 2 shown. Figure 3 The cross-sectional view of the triangle 10 is shown. It should be pointed out that this is only a schematic illustration and does not mean that the shape of the product must be this. The shape of the sharp micro-area can be square, circular, triangular, hexagonal, irregular or any other micro-area. As long as it can form an area of ​​dense short lines after filling, it meets the definition of the present invention. The illustrations shown in the present invention are only schematic diagrams and do not represent the actual graphic size, precision and other proportional relationships.

[0035] See also Figure 2 When the triangle 10 is sliced ​​in the horizontal direction, a plurality of sharp micro-areas are formed, especially at the tip portion indicated by arrow 1 . Figure 3 The cross-sectional view clearly shows the sharp tiny area formed after the dissection of the triangle 10 structure, further highlighting the feature indicated by arrow 1.

[0036] The three-dimensional digital model of the triangle 10 with the formed angle adjusted is imported into the laser selective melting forming software, such as Magics software, and then sliced ​​according to a specific thickness d. In this way, a slice file based on the layer thickness d can be obtained, and the thickness of each layer is d, and its two-dimensional shape is the two-dimensional geometric shape enclosed by the part contour. The layered schematic diagram is shown in FIG. Figure 4 As shown, the layer thickness d ranges from 0.01 to 0.2 mm. Figure 4 It does not represent the actual shape of the part. The figure takes 5 layers as an example to show the shape of each layer after slicing.

[0037] After the part is directly layered by thickness d in the slicing software, each layer will form a sharp edge, because the part is actually composed of a series of triangular facets. When the layering software recognizes it, the sharp edges will be blunted to form right-angled edges. Therefore, the actual state of the part after layering is a step shape with a specific thickness d. The abstracted state is as follows: Figure 5 shown.

[0038] Define the part layer that has been formed as the Nth layer, and the next layer to be printed as the N+1th layer. In the area enclosed by the slice contour of each layer, part of the N+1th layer will exceed the boundary of the Nth layer. This part of the area is defined as the "out-of-bounds area", and its width is defined as W. Figure 6 As shown in the figure, the mark 21 is the out-of-bounds area, its width is D, and the calculation formula is D = d / tanγ (in this case, only one layer of thickness d is used for calculation). If multiple layers are used for calculation, then D = d / tan(arctanH / L); H = N*D (where N = 1, 2, 3, 4, 5...); tanβ = H / L.

[0039] Due to the various structural forms of different parts, the placement of the forming angle may make the surface facing the substrate a flat surface, a stepped surface or a curved surface. If the slices are sliced ​​according to the layer thickness d, the size of the out-of-bounds area of ​​each layer will be different. Through the above formula, the out-of-bounds area width of different structural micro-areas can be adjusted by defining the angle β.

[0040] exist Figure 6 In the figure, the out-of-bounds area 21 indicates the out-of-bounds area of ​​the N+1th layer to be printed beyond the boundary of the already formed Nth layer; the first dividing line 22 indicates the dividing line between the N+1th layer and the Nth layer slices; the upper surface area 23 refers to the upper surface area of ​​the N+1th layer; the second dividing line 24 indicates the dividing line between the N+1th layer and the Nth layer upper surface area; the solid filling area 25 indicates the solid filling area inside the N-1th layer. Through the first dividing line 22 and the second dividing line 24, the slice shape of each layer can be set as the upper surface area, the middle solid filling area and the out-of-bounds area in combination with the above formula.

[0041] In conventional settings, the areas of the upper surface area 23 and the out-of-bounds area 21 are relatively small, especially the out-of-bounds area 21. Although its width D range can be defined, its overall size is usually small, and the internal filling lines are short and dense. When the laser beam scans along the filling lines of the out-of-bounds area, due to the low laser power and moderate scanning speed, the spacing between the filling lines is generally large. Therefore, even if the laser beam quickly completes the scanning of the current filling line, it is not easy to cause a high concentration of heat in a small area in a short time. This makes the aforementioned problems, such as high points, warping or poor sintering, usually not occur. In addition, supports are generally added to the out-of-bounds area 21. If heat is enriched due to improper parameter settings, the supports can effectively transfer heat to the forming substrate and dissipate it through the substrate, thereby avoiding heat accumulation.

[0042] The present invention aims to reduce the phenomenon that the conventional out-of-bounds area 21 is generally set to be smaller in size and the internal filling line is generally shorter. By increasing the value of N, the width of the out-of-bounds area can be adjusted, thereby affecting the effective length of its filling line, and optimizing the effective length of the filling line in the out-of-bounds area of ​​the triangular micro-area. In addition, a laser delay parameter k (in milliseconds) is defined. When the length of the filling line is less than 2 mm and the lengths of two or more adjacent filling lines are less than 2 mm, the laser delay function will be enabled. When the laser beam scans a short filling line, after each filling line is completed, the laser will delay k milliseconds without emitting light, and then continue scanning, thereby reducing heat accumulation and reducing the occurrence of phenomena such as warping and poor metallurgy.

[0043] For the upper surface area, since the lower part is already formed solid, even if there are dense short filling lines, the heat can be effectively transferred to the substrate through the lower solid. By optimizing the sintering parameters such as laser power, laser scanning speed and filling line spacing, heat enrichment can usually be avoided. Therefore, this area rarely has abnormal conditions in actual applications, so it is not emphasized.

[0044] The present invention focuses on solving the problem of the middle solid filling area, which is the main part of the part sintering during the 3D printing process and occupies most of the area of ​​each slice. When setting parameters, the form, strategy and laser sintering parameters of the filling line seriously affect the product quality. Regardless of the shape of the three-dimensional entity, there are usually sharp corners in the two-dimensional slice contour, especially Figure 3 The sharp triangle area shown. During the filling process, the sharp corners are often filled with short lines less than 1mm in length. When the laser beam scans these short lines quickly, a large amount of heat will accumulate in a short period of time, and there is a lack of time for the heat to dissipate between adjacent short lines. This heat accumulation will cause high points to form in the sharp corners, further causing warping, thus affecting product performance and making it impossible to complete the powder spreading operation.

[0045] Due to the large area of ​​the intermediate solid filling area, higher laser power, lower scanning speed and smaller filling line spacing are required during laser sintering to ensure that the powder is sintered into a dense entity. In this process, short filling lines in sharp areas are prone to heat accumulation and lack of dissipation channels. More importantly, these sharp areas are often connected longitudinally between multiple layers. The enrichment of heat in each layer may cause the high points to gradually increase, eventually forming obvious bulges or warping, which may cause scraper wear and affect the powder spreading operation, resulting in forming failure.

[0046] The traditional solution is to adjust the laser sintering parameters, but no matter how the parameters are adjusted, it is still difficult to coordinate the perfect sintering of the whole area with the controlled protrusion of the sharp corner area. This problem seriously restricts the application of 3D printing technology and becomes a key problem that needs to be solved. Therefore, the present invention proposes a 3D printing forming method for a small area.

[0047] Import the slice file into the laser selective melting forming software, set the scanning strategy, laser power, laser scanning speed, layer thickness, overlap rate and other sintering parameters for each slice layer, and then form the printing program of the part. After the program is saved, import it into the printing device of the corresponding size.

[0048] Taking the intermediate entity filling scanning strategy of the N+1th layer as an example, the processing of the out-of-bounds area 21 and the upper surface area 23 has been described in the previous text and will not be repeated here. Figure 7 to Figure 9 shown.

[0049] See also Figure 7 , showing the partitioning strategy of the middle solid filling area. The area is divided into two parts, area A and area B. Area A is larger and occupies most of the area, while area B is smaller and also contains the sharp top area C of the middle solid filling area. It should be noted here that Figure 7 The area division in the figure is for illustration only, and the actual area may be different. The angle θ between the top of area B and area C is less than 45°, and the length L1 of area B is between 1 mm and 10 mm. Based on this, the formula can be used to identify and define the tiny area in the solid filling area in the middle of each slice.

[0050] Subsequently, the A region is divided twice. The present invention uses regular hexagons for division to form multiple hexagonal regions, and the hexagon length L2 is between 5 mm and 50 mm. The A region can also be divided into various other shapes. The division of the A region is intended to reduce the length of the internal filling line, thereby reducing the heat accumulation during laser sintering and reducing the stress during the forming process.

[0051] The division of area B can effectively identify the tiny area of ​​the middle solid filling area to avoid dense and short filling lines in the area. At the same time, by defining the value of L1, the area of ​​the tiny area is reduced, the forming time of the laser beam in area B is shortened, and the forming efficiency is improved. In this way, the forming quality of the tiny area can be ensured without reducing the printing efficiency.

[0052] Figure 8 The fill line form of the middle solid fill area of ​​the triangle N+1 layer is shown. The fill line of area A is located at Figure 7 The spacing between the filling lines in the divided hexagons is t1, ranging from 0.01 to 0.3 mm. The filling lines in adjacent hexagons have different directions, and the angle formed in the clockwise direction is 5 to 180 degrees. When the laser beam scans the filling line, the laser power is set to 50 to 500W, and the laser scanning speed is 100 to 10000mm / s. Figure 7 The defined hexagon length L2 significantly shortens the length of the scan line in area A, thereby effectively improving the internal stress during the forming process. In addition, there is a certain overlap between the edges of the filling lines in adjacent hexagons, with an overlap size of 0.01 to 0.2 mm. This overlap effectively avoids the shrinkage of the filling line during scanning, prevents the scanning line from being discontinuous, and thus reduces forming defects such as holes and cracks.

[0053] The fill lines in area B form a whole, completely filling Figure 8 The entire triangular area shown is shown as the dotted line in the figure. The filling line spacing is t2, which is also between 0.01 and 0.3 mm. The angle between the filling line and the horizontal edge is λ, and the range of λ is 0° to 30° and 150° to 180°. By defining the angle λ, the phenomenon of short scanning lines in area B is effectively avoided, especially at the tip of area B. When the angle θ is less than 10°, a large number of short filling lines with a length of less than 0.5 mm may be formed, especially when t2 is small, it is more likely to produce dense short scanning lines. At the same time, the filling line portion of area B will cross the dividing line J and overlap with the filling line portion of area B, with an overlapping size of 0.01 to 0.2 mm. This design also effectively avoids shrinkage during scanning and reduces forming defects.

[0054] Fig. 9The filling line form of the middle solid filling area of ​​the N+2 layer of the triangle is shown. Hexagonal partitioning is still used in area A, but the size of the hexagon can be consistent with the hexagon of the N+1 layer, or it can be larger or smaller. Although the size range of L2 remains unchanged, the hexagon of the N+2 layer is rotated clockwise by a certain angle relative to the N+1 layer, ranging from 5 to 60°. In addition, the hexagon of the N+2 layer can be moved a certain distance along the X-axis and Y-axis directions, with a moving distance of 1 to 10 mm. This design can avoid complete overlap with the filling line of the N+1 layer when filling the N+2 layer, thereby reducing the occurrence of forming defects such as pores, inclusions and microcracks during the printing process.

[0055] The filling line of the N+2 layer does not overlap with the N+1 layer, which is used to reduce the occurrence of forming defects such as pores, inclusions and microcracks during the printing process.

[0056] In the N+2th layer, the fill line of area A is also filled in Figure 7 In the divided hexagon, the filling line spacing is t1, ranging from 0.01 to 0.3 mm. The laser power and scanning speed when the laser beam is scanned along the filling line are consistent with the above.

[0057] The filling line in area B is rotated clockwise in the same direction as the N+1th layer by a certain angle ranging from 5° to 30°. At this time, the filling line in area B no longer fills the entire triangular area as a whole, but covers most of area B, and the tip is filled separately by a longer filling line. Fig. 9 As shown by the dotted line P in the figure. The filling line spacing t2 ranges from 0.01 to 0.3 mm, and the angle ω between the filling line and the horizontal edge is between 0° to 30° and 150° to 180°. By defining the angle ω, the formation of short scanning lines in the B area is effectively avoided, especially at the tip.

[0058] If the angle between the filling line and the horizontal edge does not meet the above requirements, or the tip of area B is too sharp and the angle θ is less than 2°, the area will no longer be filled with short lines, but will be replaced by long filling lines. The long filling line is not parallel to other filling lines in area B, such as Fig. 9 As shown by the arrow P in the figure. This design can effectively reduce the accumulation of heat.

[0059] In addition, define the laser delay parameter k (in milliseconds). When scanning the filling line in area B, if the length of the filling line is less than 2mm and there are two or more adjacent filling lines with a length less than 2mm, the laser delay function is enabled. After the laser beam completes the scanning of a short filling line, when it is deflected to the next filling line through the galvanometer, the laser delays for k milliseconds and no light is emitted during this period. After the delay is over, the laser scans along the current filling line again. This process is repeated until the scanning of area B is completed. By defining the filling line length and the laser delay parameter k, the buffer time after the laser beam scanning provides an opportunity for heat dissipation, effectively reducing heat accumulation, thereby reducing the occurrence of warping and poor metallurgy when scanning small areas.

[0060] Through the above definition, the filling line area division of the micro area and the setting of the filling line filling strategy are realized. The main purpose is to identify the upper surface area, the middle solid filling area and the lower surface area by dividing the different areas of each layer of slice contour. Since the accumulation of a large amount of heat in a short time is the key factor affecting the continuous forming of the micro area, and the upper surface area has little effect on it, the present invention does not focus on this.

[0061] For the out-of-bounds area of ​​a tiny region, considering that the externally added process support can effectively accelerate the heat dissipation, the formula in step 5 is usually used to define the range of the out-of-bounds area and the strategy of laser light delay to balance the heat.

[0062] The focus is on the intermediate entity filling area. By secondary division of the intermediate entity filling area of ​​the tiny area, the problem of short and dense filling lines at the tip caused by the conventional filling line filling strategy is eradicated. Most of the area is divided into area A, and a very small part is area B. Repartitioning area A so that its filling lines are divided into unconnected sub-areas helps to shorten the length of the laser beam scanning along the filling lines of the sub-areas, thereby reducing the stress during the printing process and reducing the risk of deformation and cracking. Although the partitions are divided and the scanning line directions between the partitions are different, there is still some overlap, which avoids isolated forming due to stress and realizes the organic combination of separation and unification. In addition, between adjacent layers, the filling line partitions of area A do not overlap at all, but are cross-dislocated, so that the forming defects in a certain layer can be sintered again and eliminated in the printing of subsequent layers.

[0063] For the design of area B, by defining the angle between the filling line and the horizontal line, the possibility of dense and short filling lines is completely eliminated. At the same time, the design of single or multiple long filling lines at the tip avoids the loss of features caused by the lack of laser beam scanning. The definition of laser delay parameters allows the occasional short filling lines to increase the time for heat dissipation during the laser scanning process, thereby reducing heat enrichment.

[0064] By dividing the middle solid filling area twice, the laser sintering parameters of the A and B areas can be adjusted separately to ensure fast and efficient sintering of the A area. Since the area of ​​the B area is relatively small, even if the laser delay is set, it will not significantly affect the forming efficiency. This method effectively avoids the significant decrease in forming efficiency caused by laser delay or sintering parameter adjustment of the entire middle solid filling area, and successfully achieves a win-win situation of forming efficiency and forming quality of small areas.

[0065] After scanning, the forming chamber is lowered by one layer thickness, the scraper spreads the powder, and then the laser beam continues to scan and print each layer of the part using the above strategy until the part is completely formed. Through the above series of measures, efficient and smooth printing of small areas is achieved.

[0066] In summary, the micro-area 3D printing forming method provided by the present invention has the following advantages:

[0067] The present invention solves the problem of product warping and performance degradation caused by short scanning line segments and heat enrichment in the micro-area during laser selective melting forming by secondary division of the solid filling area in the middle of the micro-area. By dividing the solid filling area into area A and area B, and further subdividing area A, the length and direction of the scanning line are optimized, the heat accumulation in the laser sintering process is reduced, and the stress and deformation risk in the forming process are reduced. For the special design of area B, by defining the angle between the filling line and the horizontal line, the phenomenon of dense and short filling lines is effectively avoided, especially at the tip, the long filling line design prevents the loss of features. At the same time, the setting of the laser delay parameter provides sufficient heat dissipation time for the short filling line, reducing heat enrichment. There is an offset and angle misalignment between the filling lines between the upper and lower adjacent printing layers, which further reduces the generation of forming defects such as holes, inclusions and microcracks. This method ensures fast and efficient sintering of area A, and the delay setting of area B will not significantly affect the forming efficiency due to its small area, taking into account both the forming efficiency and the forming quality of the micro-area.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A micro-area 3D printing forming method, wherein a three-dimensional digital model of a structure with a formed angle adjusted is imported into a laser selective melting forming software for slicing, and a printing layer including an out-of-bounds area, a solid filling area and an upper surface area is generated, characterized in that: Set the scanning strategy for solid fill areas: The solid filling area is divided into area A and area B. The area of ​​area A is larger than that of area B. Area B includes area C located at the sharp top. The angle of area C is defined as θ, θ<45°; the length of area B is defined as L1, 1mm<L1<10mm; Divide area A into multiple sub-areas; Fill lines are set in the sub-areas and area B respectively, and the fill lines of adjacent sub-areas and the sub-areas adjacent to area B have angles, and the fill lines have overlapping areas; Define the angle between the fill line and the horizontal edge in area B as λ, 0°<λ<30° or 150°<λ<180°; There is a deflection angle between the sub-areas of the upper and lower adjacent printing layers, and the deflection angle ranges from 5° to 60°; There is also an offset distance of 1mm to 10mm between the sub-areas of the upper and lower adjacent printing layers in the X-axis and Y-axis directions.

2. The micro-area 3D printing forming method according to claim 1, characterized in that: The thickness d of the slice ranges from 0.01 to 0.2 mm.

3. The micro-area 3D printing forming method according to claim 1, characterized in that: The sub-area is in the shape of a regular hexagon; the side length L2 of the regular hexagon is defined as 5mm<L2<50mm.

4. The micro-area 3D printing forming method according to claim 1, characterized in that: If θ<2°, the C region is filled with a long filling line, and the long filling line intersects with other filling lines in the B region.

5. The micro-area 3D printing forming method according to claim 1, characterized in that: In area B, if the length of two or more adjacent filling lines is less than 2 mm, the laser delay strategy is enabled: After the laser beam completes scanning a short filling line, the galvanometer deflects to the next filling line, and the laser delays for k milliseconds. After the delay, the laser scans along the filling line again; the delay process continues until the entire scan of area B is completed to optimize the laser scanning stability and prevent overheating and forming defects.

6. The micro-area 3D printing forming method according to claim 1, characterized in that: The spacing of the filling lines in the sub-area is defined as t1, 0.01<t1<0.3mm; the spacing of the filling lines in the B area is defined as t2, 0.01<t2<0.3mm.

7. The micro-area 3D printing forming method according to claim 1, characterized in that: Support is also added in the out-of-bounds area.

8. The micro-area 3D printing forming method according to claim 1, characterized in that: The width of the overlapping area ranges from 0.01 mm to 0.2 mm.

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