CN117428210B - Multi-laser selective fusion lapping method - Google Patents

Abstract

The invention relates to a multi-laser selective melting and overlapping method, which includes the following steps: providing two or more lasers; determining the part of the part to be printed that is in the laser overlapping area and the width of the laser overlapping area; according to the part to be printed According to the actual usage conditions and stress characteristics, clarify the stress direction and/or stress magnitude in the laser overlap area, and divide the part of the part to be printed in the laser overlap area into two or more grids; divide the mesh into Grids are assigned to lasers in such a way that the laser assigned to any one of all grids is different from the laser assigned to the grid adjacent to the grid; and the laser assigned to the grid is assigned to the laser in the grid. The scan path within the grid is set to a zigzag pattern. The above-mentioned multi-laser selective melting and overlapping method can effectively reduce the internal stress of additive manufacturing products in the laser overlapping area, and improve the consistency of the structure and mechanical properties of parts in the multi-laser overlapping area and the single laser scanning area.

Description

Multi-laser selective melting and overlapping method

Technical field

The invention relates to a multi-laser selective melting and overlapping method. More specifically, the present invention relates to a multi-laser selective melting and lapping method that reduces internal stress.

Background technique

As a representative of metal additive manufacturing technology, selective laser melting (SLM) technology can realize integrated high-precision forming of complex metal parts, and has the characteristics of liberating design, short manufacturing cycle, high material utilization rate, cost reduction and weight reduction, and surface expression ability. It has strong advantages and is widely used in aircraft and spacecraft. At present, domestic and foreign companies such as AVIC, Aerospace Science and Industry, China Shipbuilding Industry Corporation, GE, Airbus, and Safran have begun to use selective laser melting products on a large scale.

In recent years, in order to further break through the limitations of selective laser melting technology in terms of production speed, manufacturing cost, and formable part size, new selective laser melting equipment generally uses two or more lasers in one device to print the entire printing plane. It is divided into multiple molding areas and molded separately, so the printing speed can be doubled and the printing range can be expanded.

Currently, selective laser melting equipment equipped with multiple lasers usually adopts a relatively simple hard transition method. As shown in Figure 1, there is shown an overlap region 2 formed between the shaping regions 1 of the two lasers. This process determines that there is a natural overlap phenomenon in the overlap area 2 between the forming area 1 of the two lasers. Therefore, when forming large-size parts, the overlap between lasers often has a width of 1mm. ~50mm overlap area 2 (i.e., the overlapping portion of the forming area 1 scanned by different laser heads). In this overlapping area 2, there are obvious differences in the metallographic structure, local properties, and macroscopic appearance of the formed body compared with the non-overlapping area.

Specifically, the misalignment of the laser beam causes dimensional errors and edge misalignment at the seams. As a result, the formed large-size parts have obvious differences in the macro surface morphology and microstructure of the overlapping area 2 and the non-overlapping area. The non-uniformity leads to discontinuity in the structure of the overlap area 2 and an increase in internal stress. It is easy for stress concentration to cause crack initiation and expansion, which in turn causes parts to fail before their designed service life, limiting related applications.

Especially for large-size additively manufactured parts for civil aircraft, due to the product design criteria of long service life, full process control, high reliability, and consistency of civil aircraft, the material and manufacturing process of the product must be included in the forming process of the parts. Maintaining a high degree of stability and consistency, only on this basis can we achieve consistency and stability of the material's microstructure and mechanical properties, effectively reduce local stress and defects in the product, and improve the long-term reliability of large-size civil aircraft additive manufacturing parts. sex.

In view of the above problems, the present invention proposes a multi-laser selective melting and overlapping method, which effectively reduces the internal stress of additive manufacturing products in the laser overlapping area and improves the structure of the parts in the multi-laser overlapping area and the single laser scanning area. and the consistency of mechanical properties to better meet the consistency requirements of large-size parts for process and product material properties, thereby solving the above shortcomings.

Contents of the invention

The object of the present invention is to provide a multi-laser selective melting and overlapping method to improve the consistency of the structure and mechanical properties of parts in the multi-laser overlapping area and the single laser scanning area.

According to a first aspect of the present invention, it relates to a multi-laser selective melting and lapping method, which includes the following steps:

(i) Provide two or more lasers;

(ii) Determine the part of the part to be printed that is within the laser overlap area and the width of the laser overlap area;

(iii) According to the actual operating conditions and stress characteristics of the parts to be printed, clarify the stress direction and/or stress magnitude in the laser overlap area, and divide the part of the parts to be printed in the laser overlap area into two or two parts. More than one grid;

(iv) Assign grids to lasers in such a way that any one of the grids is assigned a laser that is different from the laser allocated to a grid adjacent to that grid; and

(v) Set the scanning path of the laser assigned to the grid to a zigzag within the grid.

In the case of only two lasers, "any one of all the grids is assigned a laser different from the laser allocated to the grid adjacent to it" is a kind of intersection similar to a chess board. Arrangement such that the first laser is assigned to a certain grid and the second laser is assigned to four other grids adjacent to this grid.

In the case where there are three or more lasers, "the laser allocated to any grid in all grids is different from the laser allocated to the grid adjacent to the grid" is not limited to the aforementioned checkerboard intersection. layout.

For example, in the case of three lasers, if the first laser is assigned to a certain grid, the second laser or the third laser may be assigned to four other grids adjacent to the grid. In the case where there are four lasers, when the first laser is assigned to a certain grid, any one of the second laser, the third laser, and the fourth laser can be assigned to the grid adjacent to the grid. For the other four grids, it is enough as long as the laser allocated to any one grid in all grids is different from the laser allocated to the grid adjacent to this grid. The total number of above allocations will grow exponentially as the number of lasers increases.

The term "zigzag" describes a common pattern of travel of a laser beam's scan path within a grid. Specifically, the laser beam moves back and forth within the grid, and each movement is offset by a certain angle from the previous movement, thus forming a path similar to the Chinese character "中" in the grid.

The above technical solution effectively avoids problems such as large temperature gradients and uneven internal stress distribution caused by too long a single laser scanning path, and improves the tissue uniformity and surface flatness of the overlapping area.

In a preferred embodiment, in step (ii), the width of the laser overlap area is determined based on the size of the part to be printed and/or the stress level in the laser overlap area.

Specifically, the width of the laser overlap area is related to the size of the equipment forming chamber, the size of the parts, and the stress distribution under actual working conditions. The width of the laser overlap area is preferably 2 to 20 mm. The larger the size of the part, the larger the width of the laser overlap area; the greater the stress on the tissue in the laser overlap area, the larger the width of the laser overlap area. That is to say, the width of the laser overlap area is directly proportional to the size of the part to be printed and/or the amount of stress in the laser overlap area.

In yet another preferred embodiment, in step (iii), the parallel line direction of the grid forms an angle of 30 to 60 degrees with the stress direction. More preferably, the parallel line direction of the grid forms an angle of 45 degrees with the stress direction.

In another preferred embodiment, in step (iii), the area of the grid is 0.04~1mm ² , the individual area of the grid is proportional to the stress in the laser overlap area, and the number of grids is proportional to the laser The stress magnitude in the overlap area is inversely proportional to the relationship.

Specifically, "the single area of the grid is proportional to the stress in the laser overlap area" means that the area with greater stress has a smaller number of grids, and the area with smaller stress has a smaller number of grids. more. For example, for a material whose local stress is 40% of the tensile strength in the XY direction of the material, the area of a single grid is preferably 0.16mm ² ; for a material where the local stress is 50% of the tensile strength in the XY direction of the material, the area of a single grid The area of a single grid is preferably 0.25mm ² ; for a material where the local stress is 60% of the tensile strength in the XY direction of the material, the area of a single grid is preferably 0.36mm ² .

In another preferred embodiment, in step (v), the angle between the scanning paths of two adjacent grids in the grid is between 45° and 135°.

As mentioned previously, the scan paths of the lasers assigned to the grid are set up in a zigzag pattern within the grid. The above-mentioned scanning path angle is a further limitation on the zigzag scanning path. For example, the scanning path angle of two adjacent grids in the grid is preferably between 75° and 105°.

Preferably, in step (v), the starting point of the scanning path within the grid is opposite to the end point of the scanning path within an adjacent grid of the grid.

Preferably, in step (v), the laser overlap area adopts a layered staggered scanning method, in which the scanning path of each layer rotates clockwise or counterclockwise at a predetermined angle, wherein the predetermined angle is 2° to 5°.

The multi-laser selective melting and overlapping method according to the present invention can obtain the following advantages:

(i) By allocating the area, the problems of large temperature gradient and uneven internal stress distribution caused by a single long laser scanning path are effectively avoided, and the tissue uniformity and surface flatness of the overlapping area are improved;

(ii) By designing the scanning path, unfusion defects and residual stress at the checkerboard junction of the overlap area can be reduced, and deformation and cracking can be reduced.

Description of drawings

In order to further illustrate the technical effects of the multi-laser selective melting and lapping method according to the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, wherein:

Figure 1 shows the overlap region formed between the interface regions formed by two lasers;

Figure 2 shows a layout diagram of area allocation in the multi-laser selective melting and lapping method according to the present invention;

Figure 3 shows a design diagram of the scanning path in the multi-laser selective melting and lapping method according to the present invention;

Figure 4 shows a layout diagram of area allocation in the multi-laser selective melting and lapping method according to the first embodiment of the present invention;

Figure 5 shows a design diagram of the scanning path in the multi-laser selective melting and lapping method according to the first embodiment of the present invention;

Figure 6 shows a layout diagram of area allocation in the multi-laser selective melting and lapping method according to the second embodiment of the present invention;

Figure 7 shows a design diagram of the scanning path in the multi-laser selective melting and lapping method according to the second embodiment of the present invention;

Figure 8 shows a layout diagram of area allocation in the multi-laser selective melting and lapping method according to the third embodiment of the present invention; and

FIG. 9 shows a design diagram of the scanning path in the multi-laser selective fusion splicing method according to the third embodiment of the present invention.

Reference signs:

1 forming area;

11-14 first to fourth forming areas;

2 Laser overlap area;

3 grid;

31-39 Grids 1 to 9.

Detailed ways

Each step of the multi-laser selective melting and overlapping method according to the present invention and its technical effects will be described below with reference to the accompanying drawings.

It should be understood that the embodiments described in this specification only cover some, but not all, of the embodiments of the present invention. Based on the embodiments recorded in the specification, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings commonly understood by those skilled in the technical field belonging to the present invention. The terms used in the description of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The terms "including" and "having" and any variations thereof in the description and claims of the present invention and the above description of the drawings are intended to cover a non-exclusive inclusion. As used in this embodiment and the appended claims, the singular forms "a," "the" and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise.

Based on the same understanding of orientation, in the description of the present invention, the orientation or positional relationship indicated by the terms "inside", "outside", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only In order to facilitate the description of the present invention and simplify the description, it is not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be construed as a limitation of the present invention.

Figures 2 and 3 illustrate the general principles for allocating areas and designing scanning paths in the multi-laser selective melting and overlapping method according to the present invention.

The multi-laser selective melting and overlapping method according to the present invention includes the following steps:

(i) Provide two or more lasers;

(ii) Determine the part of the part to be printed that is within the laser overlap area and the width of the laser overlap area;

(iii) According to the actual operating conditions and stress characteristics of the parts to be printed, clarify the stress direction and/or stress magnitude in the laser overlap area, and divide the part of the parts to be printed in the laser overlap area into two or two parts. More than one grid;

(iv) Assign grids to lasers in such a way that any one of the grids is assigned a laser that is different from the laser allocated to a grid adjacent to that grid; and

(v) Set the scanning path of the laser assigned to the grid to a zigzag within the grid.

As shown in Figure 2, when there are two lasers, according to the multi-laser selective melting and overlapping method of the present invention, a cross arrangement such as a checkerboard is used to allocate lasers to each grid. The overlapping area 2 shown in Figure 2 is divided into 3×5 grids 3, where the first row of 5 grids 3 is assigned to the first laser in sequence from left to right (indicated by a pattern of multiple diagonal lines) , the second laser (represented by a pattern of multiple squares), the first laser, the second laser and the first laser, the second row of 5 grids 3 are assigned to the second laser, the first laser, Second laser, first laser, first laser, and so on. In summary, the first laser and the second laser are assigned to the respective grids in such a way that any one of all the grids is assigned a laser that is different from the laser assigned to the grid adjacent to this grid.

As shown in Figure 3, after allocating lasers to each grid, design the scanning path of the laser in each grid. The solid line with an arrow represents the scanning path and direction of the first laser in the grid. The dotted line with an arrow indicates the scanning path and direction of the second laser in the grid. Overall, the scanning path of the laser assigned to the grid within the grid is set in a zigzag shape, wherein the angle between the scanning paths of two adjacent grids is between 45° and 135°, preferably between 75° and 75°. ° to 105°. In addition, the scan path can be further designed such that the starting point in the grid is opposite to the end point of the scan path in the adjacent grid.

On the other hand, if the overlapping area 2 is composed of multiple stacked layers of materials, a layered staggered scanning method can be used between each layer, that is, the scanning path of each layer is clockwise compared with the adjacent layer. Or rotate counterclockwise by a certain angle, which is preferably 2° to 5°. This can reduce unfusion defects and residual stress at the checkerboard junction in the overlap area, reducing deformation and cracking. The track spacing between scanning paths is 1-1.5 times the spot diameter to ensure a certain remelting area and reduce the probability of unfusion and poor fusion defects.

(First Embodiment)

Figures 4 and 5 respectively show schematic diagrams of area allocation and scanning path design in the multi-laser selective melting and overlapping method according to the first embodiment of the present invention.

A first embodiment according to the present invention relates to a distribution and scanning scheme of dual lasers in the overlap area when forming Ti-6Al-4V parts with SLM equipment. The overlap area 2 is between the first shaping area 11 of the first laser and the second shaping area 12 of the second laser. Since the local working condition stress of the above-mentioned parts in the overlap area 2 is 50% of the tensile strength in the X-Y direction of the material, the side length of a single square grid is designed to be 0.5mm. The allocated grid is arranged in a 3×6 format, that is, three rows and six columns. The subscript number of X represents the column of the grid, and the subscript number of Y represents the row of the grid.

As shown in Figure 4, X ₂ Y _1, X ₁ Y _2, X ₃ Y _2, X ₂ Y _3, X ₁ Y _4, X ₃ Y _4, X ₂ Y _{5, X 1} Y _{6 ,} These nine grids are assigned to the first laser ₍ represented _by a pattern of multiple squares), X ₁ Y _1, X ₃ Y _{1 , X 2} Y _{2 ,} The nine grids _4, X ₁ Y _5, X ₃ Y _5, X ₂ Y ₆ are assigned to the second laser (represented by a pattern of multiple diagonal lines). It can be seen that the laser allocated to any one grid among all grids is different from the laser allocated to the grid adjacent to the grid.

Figure 5 shows the scanning paths designed for each grid 31, 32, 33 and 34. It can be seen that the solid line with arrows represents the scanning path and direction of the first laser, and the dotted line with arrows represents the scanning path and direction of the second laser. Scanning path and direction, wherein the scanning path of the second laser in the first grid 31 and the scanning path of the first laser in the second grid 32 form an included angle of 135°, and the first laser in the second grid 32 The scanning path in and the scanning path of the second laser in the third grid 33 form an included angle of 135°, and the scanning path of the second laser in the third grid 33 and the scanning path of the first laser in the fourth grid 34 The scanning path forms an included angle of 45°, and the scanning path of the first laser in the fourth grid 34 and the scanning path of the second laser in the first grid 31 form an included angle of 45°.

In addition, the layers in the overlapping area are rotated clockwise by 2°, and the track spacing between scanning paths is 1 times the spot diameter.

(Second Embodiment)

Figures 6 and 7 respectively show schematic diagrams of area allocation and scanning path design in the multi-laser selective melting and overlapping method according to the second embodiment of the present invention.

The second embodiment according to the present invention relates to the distribution and scanning scheme of four lasers in the overlapping area when forming AlMgScZr parts for SLM equipment. The overlapping area 2 is between the first shaping area 11 of the first laser, the second shaping area 12 of the second laser, the third shaping area 13 of the third laser and the fourth shaping area 14 of the fourth laser. Since the local working stress of the above-mentioned parts in the overlap area 2 is 60% of the tensile strength in the X-Y direction of the material, the side length of a single square grid is designed to be 0.6mm. The allocated grid is arranged in a 3×3 format, that is, three rows and three columns. The subscript number of X represents the column of the grid, and the subscript number of Y represents the row of the grid.

As shown in Figure 6, the three grids X ₁ Y _1, X ₃ Y _{2, and} X ₂ Y ₃ are assigned to the first laser (represented by a pattern of multiple squares), X _{3 Y 1,} The two grids ₂ are assigned to the second laser (represented by a pattern of multiple diagonal lines), and the two grids X ₃ Y _{3 and} X ₂ Y ₁ are assigned to the third laser (represented by a pattern of multiple rhombuses). Represented), the two grids X ₁ Y _{3 and} X ₂ Y ₂ are assigned to the fourth laser (represented by multiple brick-shaped patterns). It can be seen that the laser allocated to any one grid among all grids is different from the laser allocated to the grid adjacent to the grid.

Figure 7 shows the scanning paths designed for each grid 31, 32, 33, 34, 35, 36, 37, 38 and 39. It can be seen that the solid line with an arrow represents the scanning path and direction of the first laser. , the dot-dash line with arrows represents the scanning path and direction of the second laser, the dotted line with arrows represents the scanning path and direction of the third laser, and the double-dash line with arrows represents the scanning path and direction of the fourth laser, where, The scanning path of the second laser in the first grid 31 and the scanning path of the third laser in the second grid 32 form an included angle of 135°. The scanning path of the third laser in the second grid 32 is in contact with the first grid. The scanning path of the laser in the third grid 33 forms an included angle of 135°, and the scanning path of the first laser in the third grid 33 and the scanning path of the second laser in the fourth grid 34 form an included angle of 135°. angle, the scanning path of the second laser in the fourth grid 34 and the scanning path of the fourth laser in the fifth grid 35 form an included angle of 135°, and the scanning path of the fourth laser in the fifth grid 35 is equal to The scanning path of the first laser in the sixth grid 36 forms an included angle of 90°, and the scanning path of the first laser in the sixth grid 36 and the scanning path of the third laser in the seventh grid 37 form an included angle of 90°. , the scanning path of the third laser in the seventh grid 37 and the scanning path of the first laser in the eighth grid 38 form an included angle of 135°, and the scanning path of the first laser in the eighth grid 38 The path forms an included angle of 45° with the scanning path of the fourth laser in the ninth grid 39 .

In addition, the layers in the overlapping area are rotated 3° clockwise, and the track spacing between scanning paths is 1.3 times the diameter of the spot.

(Third Embodiment)

Figures 8 and 9 respectively show schematic diagrams of area allocation and scanning path design in the multi-laser selective melting and overlapping method according to the third embodiment of the present invention.

A first embodiment according to the present invention relates to a distribution and scanning scheme of dual lasers in the overlapping area when forming AlSi10Mg parts with SLM equipment. The parts to be printed form irregular patterns in the laser overlap area 2 between the first forming area 11 of the first laser and the second forming area 12 of the second laser. Since the local working condition stress of the above-mentioned parts in the laser overlap area 2 is 50% of the tensile strength in the X-Y direction of the material, the side length of a single complete square grid is designed to be 0.5mm. The allocated grid is arranged in a 3×5 format, that is, three rows and five columns, and some grids have irregular areas. The subscript number of X represents the column of the grid, and the subscript number of Y represents the row of the grid.

As shown in Figure 8, seven grids X ₂ Y _1, X ₁ Y _2, X ₃ Y _2, X ₂ Y _3, X ₁ Y _4, X ₃ Y _4, X ₂ Y ₅ are assigned to the first Laser (represented by a pattern of multiple squares), X ₁ Y _1, X ₃ Y _1, X ₂ Y ₂ , X ₁ Y 3, X ₃ Y _3, X ₂ Y _{4, X 1} Y _5, X ₃ Y ₅ These eight grids are assigned to the second laser (represented by a pattern of multiple diagonal lines). It can be seen that the laser allocated to any one grid among all grids is different from the laser allocated to the grid adjacent to the grid.

Figure 9 shows the scanning paths designed for each grid 31, 32, 33 and 34. It can be seen that the solid line with arrows represents the scanning path and direction of the first laser, and the dotted line with arrows represents the scanning path and direction of the second laser. Scanning path and direction, wherein the scanning path of the second laser in the first grid 31 and the scanning path of the first laser in the second grid 32 form an included angle of 135°, and the first laser in the second grid 32 The scanning path in and the scanning path of the second laser in the third grid 33 form an included angle of 135°, and the scanning path of the second laser in the third grid 33 and the scanning path of the first laser in the fourth grid 34 The scanning path forms an included angle of 45°, and the scanning path of the first laser in the fourth grid 34 and the scanning path of the second laser in the first grid 31 form an included angle of 45°.

In addition, the layers in the overlapping area are rotated counterclockwise by 5°, and the track spacing between scanning paths is 1.5 times the diameter of the spot.

Although the steps and technical effects of the multi-laser selective melting and lapping method according to the present invention have been described above in combination with several preferred embodiments and drawings, those of ordinary skill in the art should realize that the above examples are only It is used for illustration and should not be used as a limitation of the present invention. Therefore, modifications and variations can be made to the present invention within the spirit and scope of the claims, and these modifications and variations will fall within the scope of the claims of the present invention.

Claims (6)

1. A multi-laser selective fusion lap joint method comprises the following steps:

(i) Providing two or more lasers;

(ii) Determining the part of the part to be printed in the laser lapping area (2) and the width of the laser lapping area (2), wherein the width of the laser lapping area (2) is determined according to the size of the part to be printed and/or the stress in the laser lapping area (2), the width of the laser lapping area (2) is 2-20 mm, and the width of the laser lapping area (2) is in direct proportion to the size of the part to be printed and/or the stress in the laser lapping area (2);

(iii) According to the actual use working condition and stress characteristics of the part to be printed, the stress direction and/or the stress size in the laser overlap region (2) are defined, the part of the part to be printed in the laser overlap region (2) is divided into two or more grids (3), wherein the parallel line direction of the grids (3) forms an included angle of 30-60 degrees with the stress direction, and the area of the grids (3) is 0.04-1 mm ² The grid is [ ]3) Is proportional to the stress level in the laser lap zone (2), the number of the grids (3) being inversely proportional to the stress level in the laser lap zone (2);

(iv) -assigning the grids (3) to the lasers in such a way that any one of the grids (3) is assigned a different laser than the one assigned to the grid adjacent to that grid; and

(v) The scanning paths of the lasers distributed by the grids (3) in the grids (3) are arranged in a zigzag shape, namely, laser beams move back and forth in the grids, each movement and the previous movement are offset by a travel route with a certain angle, and the included angle of the scanning paths of two adjacent grids in the grids (3) is between 45 degrees and 135 degrees.

2. A multiple laser selective fusion splicing method according to claim 1, characterized in that the parallel line direction of the grid (3) is at an angle of 45 degrees to the stress direction.

3. The multiple laser selective fusion splicing method according to claim 1, wherein the scan path angle of two adjacent grids of the grids (3) is between 75 ° and 105 °.

4. The multiple laser selective melt lap method of claim 1, wherein in step (v), the start of said scan path within said grid (3) is opposite the end of said scan path within an adjacent grid of said grid (3).

5. The multiple laser selective melt lap method of claim 1, wherein in step (v), said laser lap area (2) is scanned in a layered staggered scan pattern wherein the scan path of each layer is rotated clockwise or counterclockwise by a predetermined angle, wherein said predetermined angle is 2 ° to 5 °.

6. The multiple laser selective melt lap method of claim 1, wherein in step (v), the track spacing between the scan paths in said grid (3) is 1-1.5 times the spot diameter.