Selective laser additive forming method for curved-surface grid part

Abstract

A selective laser additive forming method for a curved-surface grid part comprises the steps that S1, the printing direction is adjusted, and it is guaranteed that the included angle between the grid surface and a substrate is larger than the self-forming angle; s2, all acute angles in the grid holes need to be chamfered; s3, the joints of the overhanging bosses on the curved surface and the curved surface need to be chamfered, compensation edges need to be added to the surface of the opposite side, and rib-shaped supports are added to the bottoms of the overhanging bosses on the curved surface; s4, tree-shaped supports are added to the lower portions of the curved-surface special-shaped rib plates; s5, dot matrixes are applied to the two sides of the joint of the curved surface and the substrate. Self-forming of the grid structure in the selective laser additive manufacturing process is achieved, subsequent machining of the grid structure is not needed, and the surface roughness meets the specific process requirement; the curved surface grid structure is free of cracking in the selective laser material adding process, and molded surface deformation is controlled; the efficiency of manufacturing the curved surface grid structure through selective laser additive manufacturing can be improved, and the scheme cost and the machine cost are reduced.

Description

Technical Field

[0001] The invention relates to a laser selective area additive forming method for a curved surface grid part, and belongs to the field of additive forming design. Background Art

[0002] The grid structure is a special aerodynamic control structure. Compared with the traditional structure, the grid structure has a smaller chord length, the grid pressure center is very close to the hinge axis and is less affected by the angle of attack. Therefore, the hinge torque is smaller, which reduces the requirements for the actuator and allows the use of a lighter and smaller steering mechanism. At the same time, the grid structure is easy to fold, which reduces the spatial volume of the grid structure layout. In addition, the flow separation of the grid structure is later than that of the flat plate structure, which is conducive to maintaining lift at a large angle of attack. Compared with the conventional flat plate structure, the grid structure layout has a larger drag. It can be said that reducing drag and improving lift-to-drag ratio are the key to the study of the aerodynamic characteristics of the grid structure. The main measures to reduce the drag of the grid structure are to change the cross-sectional shape of the grid structure, reduce the thickness of the frame and the grid bars, such as the swept grid structure layout, the grid structure layout with a local swept angle, and the curved grid structure layout. Compared with the conventional grid wing layout, these grid structure layout forms have a certain drag reduction effect under supersonic conditions, but the structure is more complex.

[0003] Laser selective additive manufacturing technology has high forming accuracy and fine structure, and is very suitable for the manufacture of curved grid parts. Patent CN20241037698 discloses an integrated additive manufacturing method for grid wings / rudders, which uses MIG coaxial wire feeding for additive manufacturing. During the process of adding the grid wall, the wire and the grid wall have the same inclination angle relative to the vertical direction, and the wire always remains relative to the grid wall; during the process of adding reinforcement ribs, the wire and the reinforcement ribs remain relative to each other in the vertical direction. Patent CN202310631510.8 discloses an automatic generation method and system for the optimal path for additive manufacturing of grid-type parts. By inputting the path to be printed into the computer, the one-stroke path design scheme for the grid-type structure is directly calculated and output. For structures that cannot be drawn in one stroke, we will add the least auxiliary lines on the basis of the original structure to obtain a path that can be completed in one stroke, and finally achieve a non-stop additive manufacturing process. Patent CN201980047587 discloses a self-supporting grid structure and provides an additively manufactured structure, which includes a self-supporting grid structure formed by multiple unit cells. Patent CN202410751353.9 discloses an additive method for thin-walled parts with curved surface features, in which the thin-walled parts with curved surface features are sliced ​​and layered at equal intervals according to the arc length distance, and the obtained slice plane is divided into printing points at equal intervals according to the arc length distance. When the print head prints each printing point, the direction of the print head is parallel to the normal vector at each printing point. By calculating the normal vector at each printing point, the angle increment of the normal vector at each printing point along the v and u directions and its moving arc length are obtained, and then the print head and the positioner are controlled according to the transformation law of the normal vector, and the print head and the positioner are transformed and coordinated to achieve parallelism between the normal vector at each printing point. Patent CN202410029297.8 discloses a curved surface additive path planning method, device and medium based on array plane slicing. A plane normal vector is selected in a three-dimensional model, and multiple slicing planes are constructed based on the plane normal vector and a preset initial offset; a reference offset curve in the slicing plane is determined; the reference offset curve is offset in the slicing plane with a preset slicing layer thickness as the offset spacing to obtain a local additive path in each of the slicing planes; starting from the bottom of the three-dimensional model, the local additive paths are connected to form a global additive reciprocating path.

[0004] Among the disclosed methods, grids manufactured based on arc additive manufacturing often have poor surface quality and require subsequent machining. If the grid unit size is small and cannot be machined, the aerodynamic characteristics of the grid will deteriorate. Other methods mainly focus on self-forming structure design or slicing algorithms and path planning of additive processes, and do not involve the design of overall dimensional control solutions. Summary of the invention

[0005] The technical problem solved by the present invention is: in view of the problem that the existing technology lacks a complete grid structure color-enhanced dimensional shape control design method, a laser selective additive forming method for curved grid parts is proposed.

[0006] The present invention solves the above technical problems by the following technical solutions:

[0007] A laser selective area additive forming method for a curved surface grid part, comprising:

[0008] Preset the printing direction of the curved grid structure and set the sharp angle of the grid hole according to the requirements of the curved grid additive forming;

[0009] Set the angle of the connection between the overhanging boss and the surface part on the surface grid;

[0010] A compensating ridge structure is provided on the other side of the curved surface portion at the connection between the overhanging boss and the curved surface portion;

[0011] A rib-shaped structure is added at the connection between the bottom of the overhanging boss and the curved surface part for support;

[0012] A tree-shaped support structure is provided at the lower part of the special-shaped rib plate of the curved surface part;

[0013] A lattice structure is arranged at both sides of the connection between the curved surface part and the component substrate;

[0014] Additive printing is performed according to the designed curved grid structure.

[0015] The method for determining the printing direction of the curved grid structure is:

[0016] Determined by the angle formed by the curved grid surface and the part substrate, the angle is not less than 55°;

[0017] The angle formed by the surface of the curved grid and the component substrate is greater than the self-forming angle, and the self-forming angle is determined according to the forming material used in the curved grid structure.

[0018] The sharp angles in the grid holes are set as rounded corners, and the radius of the rounded corners is set to 0.4 times the grid feature size of the curved grid structure.

[0019] The angle at the connection between the overhanging boss on the curved grid and the curved surface part is set to a chamfer, and the chamfer is set to an upper limit of the angle according to the requirements of the curved grid additive forming.

[0020] The center position of the compensation ridge structure and the position of the connection between the overhanging boss on the curved surface and the curved surface part are set to be symmetrical on the front and back sides, and the connection position between the compensation ridge structure and the other side of the curved surface part is transitionally processed.

[0021] The transition processing of the connection position between the compensation edge structure and the other surface of the curved part is achieved by setting a transition bevel and a transition fillet; the transition bevel height between the compensation edge structure and the connection position is the compensation edge structure height, the transition bevel angle is 45°, and the fillet radius between the compensation edge structure and the connection position is determined according to the compensation edge structure material.

[0022] One end of the rib structure penetrates into the curved surface part, and the other end is connected to the bottom of the overhanging boss. The length of the rib structure penetrating into the curved surface part is the thickness of the forming material used for the curved grid structure.

[0023] The rib structure sintering design adopts solid support parameter sintering as the sintering parameter, the laser power of the solid support parameter sintering is set to 220W, and the scanning speed is set to 2500mm / s.

[0024] The lattice structure is set to a body-centered cubic type or a face-centered cubic type, and the envelope size and rod diameter of the lattice structure are set according to the position of the connection between the curved surface part and the component substrate; the lattice structures on both sides of the connection between the curved surface part and the component substrate are fork-shaped combined and connected.

[0025] The tree-shaped support structure includes a trunk and branches, the number of which is 1 and 5 respectively. The diameter of the top of the trunk is 0.5 mm, the diameter of the bottom of the trunk is 0.8 mm, the diameter of the top of the branch is 0.2 mm, the diameter of the bottom of the branch is 0.3 mm, and the interval between the branches is 1.5 mm.

[0026] The advantages of the present invention compared with the prior art are:

[0027] The present invention provides a method for laser selective additive manufacturing of a curved grid part, which realizes the self-forming of the grid structure during the laser selective additive manufacturing process. The grid structure does not require subsequent machining, and the surface roughness meets specific process requirements. It can ensure that the curved grid structure has no cracks during the laser selective additive manufacturing process, control surface deformation, and improve the efficiency of laser selective additive manufacturing of the curved grid structure, thereby reducing the cost of the solution and the machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of a curved grid part provided by the present invention;

[0029] Figure 2 A schematic diagram of the fillet of a local curved surface grid provided by the present invention;

[0030] Figure 3 A schematic diagram of a process for adding material to a suspended boss on a curved surface provided by the present invention;

[0031] Figure 4 A schematic diagram of a rib-shaped support for a suspended boss on a curved surface provided by the present invention;

[0032] Figure 5A schematic diagram of the lower tree-shaped support of the curved special-shaped rib plate provided by the present invention;

[0033] Figure 6 A schematic diagram of the dot matrix on both sides of the connection between the curved surface and the substrate provided by the present invention. DETAILED DESCRIPTION

[0034] A method for laser selective additive forming of curved grid parts, the steps include: S1, adjusting the printing direction to ensure that the angle between the grid surface and the substrate is greater than the self-forming angle; S2, all sharp angles in the grid holes need to be rounded; S3, the connection between the overhanging boss on the curved surface and the curved surface needs to be rounded, and the other side surface needs to add a compensating edge, and a rib-shaped support is added to the bottom of the overhanging boss on the curved surface; S4, a tree-shaped support is added to the lower part of the curved special-shaped rib plate; S5, a dot matrix is ​​applied on both sides of the connection between the curved surface and the substrate. The present invention realizes the self-forming of the grid structure in the process of laser selective additive, the grid structure does not need subsequent machining, and the surface roughness meets the specific process requirements; the curved grid structure does not crack during the process of laser selective additive, and the deformation of the profile is controlled; it can improve the efficiency of laser selective additive manufacturing of curved grid structures and reduce the cost of solutions and machines.

[0035] Laser selective additive manufacturing method for curved grid parts, the specific method is as follows:

[0036] Preset the printing direction of the curved grid structure and set the sharp angle of the grid hole according to the requirements of the curved grid additive forming;

[0037] Set the angle of the connection between the overhanging boss and the surface part on the surface grid;

[0038] A compensating ridge structure is provided on the other side of the curved surface portion at the connection between the overhanging boss and the curved surface portion;

[0039] A rib-shaped structure is added at the connection between the bottom of the overhanging boss and the curved surface part for support;

[0040] A tree-shaped support structure is provided at the lower part of the special-shaped rib plate of the curved surface part;

[0041] A lattice structure is arranged at both sides of the connection between the curved surface part and the component substrate;

[0042] Additive printing is performed according to the designed curved grid structure.

[0043] The method for determining the printing direction of the curved grid structure is:

[0044] Determined by the angle between the curved grid surface and the part substrate, the angle is not less than 55° ； ;

[0045] The angle formed by the surface of the curved grid and the component substrate is greater than the self-forming angle, and the self-forming angle is determined according to the forming material used in the curved grid structure.

[0046] The sharp corners inside the grid holes are set to be rounded, and the rounding radius is set to 0.4 times the grid feature size of the curved grid structure.

[0047] The angle of the connection between the overhanging boss and the curved surface part on the curved surface grid is set to a fillet, and the fillet is set to an upper limit of the angle according to the requirements of the curved surface grid additive forming.

[0048] The center position of the compensation edge structure and the connection position of the overhanging boss on the curved surface and the curved surface part are set to be symmetrical on the front and back sides, and the connection position between the compensation edge structure and the other side of the curved surface part is transitionally processed.

[0049] The transition processing of the connection position between the compensation edge structure and the other surface of the curved part is achieved by setting the transition bevel and the transition fillet; the transition bevel height between the compensation edge structure and the connection position is the compensation edge structure height, the transition bevel angle is 45°, and the fillet radius between the compensation edge structure and the connection position is determined according to the compensation edge structure material.

[0050] One end of the rib structure penetrates into the curved surface portion, and the other end is connected to the bottom of the overhanging boss. The length of the rib structure penetrating into the curved surface portion is the thickness of the forming material used for the curved grid structure.

[0051] The rib structure sintering design uses solid support parameter sintering as the sintering parameter. The laser power of solid support parameter sintering is set to 220W, and the scanning speed is set to 2500mm / s.

[0052] The lattice structure is set to a body-centered cubic type or a face-centered cubic type, and the envelope size and rod diameter of the lattice structure are set according to the position of the connection between the curved surface part and the part substrate; the lattice structures on both sides of the connection between the curved surface part and the part substrate are fork-shaped combined and connected.

[0053] The tree-shaped support structure includes a trunk and branches, the number of which is 1 and 5 respectively.

[0054] The following is further described in conjunction with the accompanying drawings and preferred embodiments of the specification:

[0055] In the current embodiment, the laser selective additive forming method of the curved grid 2 part, in the specific design structure completion example, the structural design includes the overhanging boss 11, the grid 2 area 2, the special-shaped rib plate 3, the grid unit fillet 4, the compensation edge structure 5, the rib support structure 6, the tree support structure 7, and the lattice structure 8;

[0056] The design steps are as follows:

[0057] S1, adjusting the printing direction to ensure that the angle between the surface of the grid 2 and the substrate is greater than the self-forming angle;

[0058] S2, all sharp corners inside grid 2 holes need to be rounded;

[0059] S3, the connection between the overhanging boss 1 on the curved surface and the curved surface needs to be rounded, and the other side surface needs to add a compensating edge. A rib-shaped support is added to the bottom of the overhanging boss 1 on the curved surface, such as Figure 4 As shown;

[0060] S4, add a tree-shaped support at the bottom of the curved special-shaped rib plate 3, such as Figure 5 As shown;

[0061] S5, dot matrix is ​​applied on both sides of the connection between the curved surface and the substrate, such as Figure 6 shown.

[0062] The self-forming angle in S1 varies according to the forming material, e.g. Figure 1 The curved grid 2 part shown is made of stainless steel, and the angle between the surface of the workpiece grid 2 and the substrate is ≥55°.

[0063] All sharp corners in grid 2 holes in S2 need to be rounded, such as Figure 2 As shown, the radius is 0.4×grid 2 feature size, grid 2 feature size is 3 mm, and the fillet radius is R1.2.

[0064] The fillet at the connection between the overhanging boss 1 on the curved surface in S3 is as large as possible while meeting the requirements of the installation area, and the fillet radius is R3.

[0065] The center position of the compensation edge 5 in S3 corresponds to the connection between the overhanging boss 1 on the curved surface and the curved surface, such as Figure 3 As shown, the width is 1 mm, the height is 0.6 mm, and the compensating edge 5 makes a transition with the curved surface.

[0066] The rib support 6 added at the bottom of the overhanging boss 1 on the curved surface in S3 has a thickness of 0.4 mm, a spacing of 1 mm, a notch of 0.3 mm, an angle of 55°, a tooth height of 0.6 mm, a tooth spacing of 0.5 mm, and a depth of penetration into the part body equals the thickness of a layer of the laser-selected additive material.

[0067] The rib support 6 added to the bottom of the overhanging boss 1 on the curved surface in S3 is sintered using the solid support parameters.

[0068] The tree-shaped support 7 added to the lower part of the curved special-shaped rib plate 3 in S4 has a trunk top diameter of 0.5 mm, a trunk bottom diameter of 0.8 mm, a branch top diameter of 0.2 mm, a branch bottom diameter of 0.3 mm, and 5 branches on the trunk with a spacing of 1.5 mm.

[0069] The tree-shaped support 7 added to the lower part of the curved special-shaped rib plate 3 in S4 is sintered using the solid support parameter.

[0070] The lattice is applied on both sides of the connection between the curved surface in S5 and the substrate, and the types of the lattice units 8 include but are not limited to body-centered cubic and face-centered cubic.

[0071] The dot matrix applied on both sides of the connection between the curved surface in S5 and the substrate has an envelope size of 5 mm and a rod diameter of 0.5 mm.

[0072] The dot matrix 8 applied on both sides of the connection between the curved surface in S5 and the substrate has a regular hexagonal rod diameter.

[0073] The dot matrix 8 applied on both sides of the connection between the curved surface in S5 and the substrate is combined in a rough fork shape.

[0074] The dot matrix 8 applied on both sides of the connection between the curved surface in S5 and the substrate adopts the solid support parameter sintering.

[0075] Solid part parameters sintering, laser power 250W, scanning speed 900mm / s.

[0076] Solid support parameters sintering, laser power 220W, scanning speed 2500mm / s.

[0077] The compensation edge 5 makes a transition with the curved surface, which is composed of a bevel + a fillet. The height of the transition bevel between the compensation edge 5 and the curved surface is the height of the compensation edge 5. The transition bevel angle between the compensation edge 5 and the curved surface is 45°, and the transition fillet radius between the transition bevel and the curved surface is R0.6.

[0078] Sintering parameters of solid parts, depending on the material,

[0079] Titanium alloy, laser power 250W-350W, scanning speed 1000mm / s-1750mm / s;

[0080] High temperature alloy, laser power 200W-300W, scanning speed 800mm / s-1200mm / s;

[0081] Aluminum alloy, laser power 300W-380W, scanning speed 900mm / s-1600mm / s;

[0082] Stainless steel, laser power 220W-300W, scanning speed 800mm / s-1000mm / s.

[0083] Solid support parameters sintering, depending on the material,

[0084] Titanium alloy, laser power 150W-250W, scanning speed 2000mm / s-2750mm / s;

[0085] High temperature alloy, laser power 200W-300W, scanning speed 2000mm / s-2750mm / s;

[0086] Aluminum alloy, laser power 300W-380W, scanning speed 900mm / s-1600mm / s;

[0087] Stainless steel, laser power 220W-300W, scanning speed 1800mm / s-2500mm / s.

[0088] The compensation edge 5 makes a transition with the curved surface, which is composed of a bevel + a fillet. The height of the transition bevel between the compensation edge 5 and the curved surface is the compensation edge height. The transition bevel angle between the compensation edge and the curved surface is ≤45°. The transition fillet radius between the transition bevel and the curved surface is ≥(0.5×compensation edge height).

[0089] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0090] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A laser selective additive manufacturing method for curved grid parts, characterized in that include: Preset the printing direction of the curved grid structure and set the sharp angle of the grid hole according to the requirements of the curved grid additive forming; Set the angle of the connection between the overhanging boss and the surface part on the surface grid; A compensating ridge structure is provided on the other side of the curved surface portion at the connection between the overhanging boss and the curved surface portion; A rib-shaped structure is added at the connection between the bottom of the overhanging boss and the curved surface part for support; A tree-shaped support structure is provided at the lower part of the special-shaped rib plate of the curved surface part; A lattice structure is arranged at both sides of the connection between the curved surface part and the component substrate; Additive printing is performed according to the designed curved grid structure.

2. The method for laser selective additive manufacturing of a curved grid part according to claim 1, characterized in that: The method for determining the printing direction of the curved grid structure is: Determined by the angle formed by the curved grid surface and the part substrate, the angle is not less than 55°; The angle formed by the surface of the curved grid and the component substrate is greater than the self-forming angle, and the self-forming angle is determined according to the forming material used in the curved grid structure.

3. The method for laser selective additive manufacturing of a curved grid part according to claim 1, characterized in that: The sharp angles in the grid holes are set as rounded corners, and the radius of the rounded corners is set to 0.4 times the grid feature size of the curved grid structure.

4. The method for laser selective additive manufacturing of a curved grid part according to claim 1, characterized in that: The angle at the connection between the overhanging boss on the curved grid and the curved surface part is set to a chamfer, and the chamfer is set to an upper limit of the angle according to the requirements of the curved grid additive forming.

5. The method for laser selective additive manufacturing of a curved grid part according to claim 1, characterized in that: The center position of the compensation ridge structure and the position of the connection between the overhanging boss on the curved surface and the curved surface part are set to be symmetrical on the front and back sides, and the connection position between the compensation ridge structure and the other side of the curved surface part is transitionally processed.

6. The method for laser selective additive manufacturing of a curved grid part according to claim 5, characterized in that: The transition processing of the connection position between the compensation edge structure and the other surface of the curved part is achieved by setting a transition bevel and a transition fillet; the transition bevel height between the compensation edge structure and the connection position is the compensation edge structure height, the transition bevel angle is 45°, and the fillet radius between the compensation edge structure and the connection position is determined according to the compensation edge structure material.

7. The method for laser selective additive manufacturing of a curved grid part according to claim 1, characterized in that: One end of the rib structure penetrates into the curved surface part, and the other end is connected to the bottom of the overhanging boss. The length of the rib structure penetrating into the curved surface part is the thickness of the forming material used for the curved grid structure.

8. The method for laser selective additive manufacturing of a curved grid part according to claim 1, characterized in that: The rib structure sintering design adopts solid support parameter sintering as the sintering parameter, the laser power of the solid support parameter sintering is set to 220W, and the scanning speed is set to 2500mm / s.

9. The method for laser selective additive manufacturing of a curved grid part according to claim 1, characterized in that: The lattice structure is set to a body-centered cubic type or a face-centered cubic type, and the envelope size and rod diameter of the lattice structure are set according to the position of the connection between the curved surface part and the component substrate; the lattice structures on both sides of the connection between the curved surface part and the component substrate are fork-shaped combined and connected.

10. The method for laser selective additive manufacturing of a curved grid part according to claim 1, characterized in that: The tree-shaped support structure includes a trunk and branches, the number of which is 1 and 5 respectively. The diameter of the top of the trunk is 0.5 mm, the diameter of the bottom of the trunk is 0.8 mm, the diameter of the top of the branch is 0.2 mm, the diameter of the bottom of the branch is 0.3 mm, and the interval between the branches is 1.5 mm.

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