An electric arc wire feeding additive manufacturing method for complex curved surface structure based on equal arc length slicing

Abstract

The application discloses a kind of complex curved surface structural member electric arc fuse additive manufacturing methods based on equal arc length slice, for maximum inclination angle exceeding 45 °, and the outer wall profile can be enclosed by circular segment ring structure piece, the application proposes equal arc length slice forming strategy, is based on the three-dimensional model of part, in the center line section, extract the outer wall profile envelope curve formed by circular segment fitting, along the outer wall envelope curve, the arc length is equal to the segmentation cutting, at each cutting point, construct a radius line through the segmentation point and the center, make the radius line rotate around the center line of part model, form rotation surface, generate additive manufacturing track with this surface as segmentation surface to the part model layering slice, obtain structural member by electric arc fuse additive manufacturing.The method effectively improves the forming stability and material utilization of this kind of complex parts, and significantly shortens production cycle and reduces cost.

Description

Technical Field

[0001] This invention belongs to the field of metal additive manufacturing technology, specifically relating to an arc-wire additive manufacturing method for complex curved surface structures based on equal arc length slices. The complex curved surface structure is a ring structure with a maximum tilt angle exceeding 45° and an outer wall contour that can be enveloped by a circular arc segment, which has the advantage of rapid prototyping. Background Technology

[0002] Arc-wire additive manufacturing technology uses a high-temperature electric arc to heat a welding wire, forming molten metal droplets that are then deposited layer by layer to create three-dimensional solid parts. This technology employs an electric arc heat source to melt the wire, offering advantages such as high deposition efficiency, shorter deposition cycles, and lower production costs. It is suitable for additive manufacturing of large, complex structural components in any spatial path.

[0003] Currently, there are three main slicing methods in arc wire additive manufacturing: the first is the traditional unidirectional equal-thickness slicing method, which slices the part model along the construction direction with equal slice thickness. This method is simple and easy to apply, but it often requires support structures when forming complex parts, and it suffers from a step effect, low processing efficiency, large processing allowance, and high processing cost. The second is the unidirectional adaptive slicing method, which considers the shape of the part along the construction direction to change the layer thickness. This method improves the surface finish of the part, reduces processing time, and increases forming efficiency, but it has high requirements for the shape of the part structure and has certain problems with forming overhang structures. The third is the multidirectional slicing method, which decomposes the part into multiple sub-parts, each with its own specific slicing direction. This method has less dependence on support structures and can realize the construction of complex parts, but the path planning is complex and prone to introducing cumulative errors. For ring-shaped structural parts with an inclination angle exceeding 45°, the above-mentioned slicing method is difficult to effectively adapt to the geometric characteristics of the inclination ring structure. During the forming process, the molten pool is significantly affected by gravity, which can easily cause the molten pool to flow and collapse, seriously threatening the stability of the forming process and the geometric accuracy and surface quality of the final part.

[0004] The core of solving the problems of poor forming stability and easy collapse of the molten pool in the process of electric arc wire additive manufacturing of inclined ring structures lies in overcoming the adverse effects of gravity on the molten pool and achieving controllable, stable, and precise material deposition at any position in space. Currently, research results on stable forming of inclined structure electric arc wire additive manufacturing mainly fall into two categories. One category involves adding support components, such as the invention patent application CN1 1 6673577 A, which discloses an electric arc additive manufacturing method suitable for inclined structural parts. This method ensures the quality of the inclined surface and the stability of the forming process by introducing a support structure, but it suffers from the problem that the support structure is difficult to completely remove and may remain inside the formed part. The other category utilizes magnetic force to balance the gravity of the molten pool, such as the invention patent application CN1 18123183 A, which discloses a method and device for unsupported inclined structures in electric arc additive manufacturing based on bidirectional magnetic assistance. This technology can effectively ensure the forming quality and accuracy of the inclined structure, but its device is relatively complex.

[0005] Therefore, it is particularly urgent to propose an electric arc wire additive manufacturing method that requires no support components or magnetic auxiliary devices and is simple and convenient to operate for inclined ring-shaped structural components. Summary of the Invention

[0006] Purpose of the invention: To address the problems of difficult path planning, uneven cladding layer, and unstable process in the forming of complex curved surfaces such as inclined ring structures, this invention provides an arc wire additive manufacturing method suitable for inclined ring structure parts. Through the equal arc length slicing strategy, it has the advantages of high deposition efficiency, low manufacturing cost, stable forming process, and "near net-shape forming".

[0007] Technical Solution: To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] An additive manufacturing method for complex curved surface structures based on equal-arc-length slicing using electric arc wire innovatively proposes an equal-arc-length slicing strategy: Based on the 3D model of the part, an outer wall contour envelope curve formed by fitting circular arc segments is extracted within its centerline section. The extracted outer wall contour envelope curve is then segmented into equal-length segments. This radius line is rotated around the centerline 3 of the part model to form a surface of revolution 13. This surface is used as a dividing surface to slice the part model into layers, generating an additive manufacturing trajectory. For example... Figure 1 As shown, the specific steps include:

[0009] Step 1: For the 3D digital model of a complex curved surface structure, extract the outer wall contour envelope curve formed by fitting circular arc segments within the cross-section passing through the model's centerline. Then, divide the extracted outer wall contour envelope curve into segments of equal arc length. The size of each equally divided arc is (…). LThe arc length is selected based on the actual arc-fused wire additive manufacturing process parameters. Due to the difficulty of direct measurement and equal arc length division, the arc length is calculated using the following formula ( L The corresponding central angle () The size is achieved by equally dividing the central angle to divide the arc length:

[0010]

[0011] In the formula Central angle (unit: radians) Arc length (unit: millimeters). The radius of the arc at that point (in millimeters).

[0012] At each dividing point, establish a plane representing the outer contour envelope curve of that point. This plane is a surface of revolution formed by the radius line connecting the dividing point to the center of the circle and perpendicular to the envelope curve, with the foot of the perpendicular at the dividing point. Using this surface of revolution as the dividing plane, the part model is sliced ​​into layers. Figure 2 As shown.

[0013] Step 2: Within the cross-section passing through the model's centerline, treat each slice as a rectangular cross-section and record the height of the center point of that rectangular cross-section. h Horizontal distance from the center point to the center line of the model s and the angle between the short side of the rectangular cross-section and the vertical direction. α (i.e., inclination angle), inclination angle α This directly determines the angle at which the machine tool table needs to be tilted during the deposition process to match the welding torch posture, such as Figure 3 As shown. The recorded data h , s , α The data is input into the machine tool control system to generate the additive manufacturing trajectory, such as... Figure 4 As shown, the direction of the welding torch is always strictly aligned with the tangent direction of the additive manufacturing trajectory, ensuring that the welding torch is always aimed at the surface of the growing deposition layer at the optimal angle.

[0014] Step 3: Deposit two metal cladding layers on the substrate as a base to help prevent the soldering gun from touching the substrate during subsequent deposition, while also filling part of the bottom of the structure.

[0015] Step 4: An arc additive manufacturing machine tool with five-axis linkage is used to additively form the part. Following the additive path generated in Step 1, the machine tool's CNC system coordinates the movement of the welding torch and the tilting and rotation of the worktable in real time. This ensures that at each deposition point, the welding torch direction is precisely along the tangent of the path, the distance between the welding torch and the deposition layer surface is constant, and the welding wire length remains stable. In this way, metal material is deposited layer by layer along a preset path until the additive manufacturing of the entire structural component is completed.

[0016] Furthermore, the complex curved surface structure is an inclined ring structure with a maximum inclination angle exceeding 45°, and its outer wall contour can be enveloped by arc segments. The number of arc segments is selected according to the shape of the inclined ring structure, and it can be enveloped by a single arc or by multiple continuous arc segments.

[0017] Furthermore, the length of the equally divided arc ( L The height of the single-layer structure deposited is equal to that of the actual arc-wire additive manufacturing process parameters.

[0018] Furthermore, the actual electric arc wire additive manufacturing process parameters include the wire feed speed as follows: V w The feed rate is V f . Beneficial effects

[0019] (1) This invention provides an arc additive manufacturing method for complex curved surface structures based on a constant arc length slicing strategy, achieving stable arc additive manufacturing of complex curved surface structures. The constant arc length slicing strategy makes the deposition height of each layer more uniform, reducing the difference in heat accumulation between layers. The welding torch is always along the tangential direction of the path, and the distance between the welding torch and the surface of the deposition layer remains constant, ensuring stable welding wire length. Combined with dynamic adjustment of the worktable, this ensures the optimal forming angle and posture of the welding torch and the inclined annular structure during the additive manufacturing process, avoiding the flow and collapse of the molten pool caused by the unstable welding wire length due to the fixed layer height in traditional constant height slicing, and significantly improving the one-time forming success rate.

[0020] (2) The equal arc length slicing strategy significantly reduces raw material waste, improves deposition efficiency, and lowers costs. By using equal arc length slicing, the deposition path length of each layer is kept uniform. The constant arc length segmentation, combined with the tangential control of the welding torch, significantly reduces the need for multi-pass overlap. At the same time, the equal arc length slicing strategy improves the stability of the molten pool and reduces material loss caused by molten pool flow or spatter.

[0021] (3) Parts formed using the equal arc length slicing strategy have superior surface quality, achieving "near-net-shape forming". The equal arc length slicing ensures that the deposition path length of each layer is basically consistent, resulting in more uniform heat input and reducing defects such as metal splashing and droplet spheroidization caused by local overheating or undercooling. The inclined annular structure formed using equal arc length slicing has a smooth and flat surface, reducing the workload and time of subsequent finishing processes such as grinding and polishing, further improving overall manufacturing efficiency and shortening the product delivery cycle. Attached Figure Description

[0022] Figure 1 This is a flowchart of additive manufacturing process based on an electric arc fuse with a tilted annular structure and equal arc length slices.

[0023] Figure 2 This is a schematic diagram of the principle of the equal arc length slice of the present invention;

[0024] Figure 3 This is a schematic diagram of key parameters under the equal arc length slicing strategy of the present invention;

[0025] Figure 4 This is an additive manufacturing trajectory diagram of the inclined ring structure of the present invention;

[0026] Figure 5 This is a schematic diagram showing the relationship between the closed impeller structure (left) and the inclined annular structure (right) in Example 1;

[0027] Figure 6 The tilt angle in Example 1 α and distance to the center line s With each slice height h The change curve;

[0028] Figure 7 This is a superimposed comparison diagram of the actual cross-sectional outline (solid line) of the shaped inclined annular structure after being cut along the center line in the embodiment and the outline (dashed line) of the theoretical model.

[0029] The names of the markings in the diagram are: 1-Outer wall contour envelope curve, 2-Radius line connecting the dividing point and the center of the circle, 3-Center line of the part model, 4-Arc length. L、 5-Central Angle 6 - Rectangular section; 7 - Height of the center point of the rectangular section h、 8- Distance from the center point of the rectangular section to the center line of the part model s、 9- Inclination Angle α、 10-Welding torch, 11-Dividing point, 12-Center of circle, 13-Surface of revolution. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions in this patent application, the technical solutions in this application are described below with reference to the accompanying drawings and application examples. The described embodiments are merely one type of embodiment in this application and do not represent all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort should fall within the scope of protection of this application.

[0031] An electric arc additive manufacturing method for complex curved surface structures based on equal arc length slices is proposed. Based on the equal arc length slice forming strategy, it is suitable for rapid prototyping of ring structures with a maximum tilt angle exceeding 45° and whose outer wall contour can be enveloped by arc segments.

[0032] The adopted equal arc length slicing strategy is as follows: First, a 3D model of the ring structure is constructed using 3D modeling software; then, based on the 3D model of the part, the outer wall contour envelope curve formed by fitting circular arc segments is extracted within the centerline section. The extracted outer wall contour envelope curve is then segmented into equal arc lengths. At each segmentation point, a normal plane of the outer wall contour envelope curve is established, which is a rotating surface that passes through the radius line between the segmentation point and the center of the circle, is perpendicular to the envelope curve, and has the foot of the perpendicular as the segmentation point. This rotating surface is used as the segmentation plane to slice the part model into layers, generating an additive manufacturing trajectory deposition tilted ring structure. This effectively improves the surface forming quality and material utilization rate of the tilted ring structure in arc additive manufacturing, significantly shortens the production cycle, and reduces costs.

[0033] The present invention will now be described in further detail with reference to the embodiments. Example

[0034] This embodiment takes the inclined annular structure, which often appears on the inner and outer walls of closed impeller components, as an example. Figure 5 As shown, an additive manufacturing method for an arc-fused wire based on an inclined annular structure with equal arc length slices is provided, comprising the following steps:

[0035] Step 1: Select the Gefertec Arc405 five-axis electric arc welding additive manufacturing system. This system consists of an additive manufacturing machine and a Fronius Advanced 4000 welding power source. The machine is equipped with a Siemens five-axis CNC system and a laser pyrometer with a temperature measurement range of 0~1500 ℃, used for precise control of interpass temperature.

[0036] Step 2: Based on Figure 5 The 3D model of the inclined ring structure part is used to extract the outer wall contour envelope curve 1 formed by fitting circular arc segments within its centerline section. The extracted outer wall contour envelope curve is then segmented into equal arc lengths. The single-layer structure height is set to an equal arc length based on the selected process parameters. The size is 2.5 mm. The outer wall of the inclined ring structure consists of two circular arcs, with the radius of the lower arc being... It is 75 mm, corresponding to a central angle of 22.05°; the radius of the upper arc The value is 100 mm, corresponding to a central angle of 11.48°. The central angle of the arc segment is calculated according to formula (1). Size is determined by equally dividing the central angle to equalize the arc length:

[0037]

[0038] In the formula To bisect the central angle, Let the arc length be , The radius of the arc;

[0039] The central angle of the lower arc is 1.68°, and the central angle of the upper arc segment with a radius of 100 mm is 1.26°.

[0040] At each dividing point, construct a radius line passing through that dividing point and the center of the circle. Rotate this radius line around the center line of the part model to form a surface of revolution. Use this surface as the dividing surface to slice the part model into layers.

[0041] Step 3: Within the cross-section passing through the model's centerline, treat each slice as a rectangular cross-section and record the height of the center point of each rectangular cross-section. h and the distance from the center point to the center line of the part model s And the angle between the short side and the vertical direction of each rectangular cross section. α , Figure 6 The parameters were displayed. s and α Follow h The trend of change. The recorded data. h , s , α The data is input into the machine tool control system to generate an additive manufacturing trajectory, ensuring that the welding gun direction at each point in the trajectory data is always consistent with the tangent direction at that point.

[0042] Step 4: The welding wire used for additive manufacturing of the inclined ring structure is GH4169 high-temperature alloy solid welding wire, 1.2 mm in diameter, with a chemical composition conforming to AMS 5662 standard, and a wire extension of 12-15 mm. The welding wire needs to be straightened before additive manufacturing. xy The directional error is ≤ 2 mm. The additive manufacturing substrate is a Q235 steel substrate with dimensions of 200 mm × 100 mm × 10 mm. To prevent the oxide film and oil on the substrate surface from affecting the arc additive manufacturing process, the upper surface of the substrate is first sanded with sandpaper, and then the sanded surface is wiped with ethanol solution to remove rust and oil and increase surface wettability. An experimental platform is set up, and the surface-treated substrate is fixed on the worktable with a fixture. The GH4169 high-temperature alloy welding wire is straightened and fed to the welding torch nozzle through a wire feeder. The shielding gas is a quaternary shielding gas, mainly containing argon and helium, with a small amount of carbon dioxide and oxygen added to stabilize the arc and improve wettability. The gas flow rate is 15 L / min.

[0043] Step 5: Using a wire feed speed of 5 m / min, a feed rate of 400 mm / min (corresponding to a linear energy density of 375.6 J / mm), and a reciprocating deposition path, arc-fused wire additive manufacturing of an inclined ring structure is performed. Two GH4169 metal cladding layers are deposited on the additive manufacturing substrate using two overlapping deposits as the substrate. The interlayer temperature is controlled at 100 ℃. Following the additive path generated in Step 3, additive manufacturing is performed layer by layer upwards until the entire inclined ring structure is completed. This strategy requires only single-pass deposition, eliminating the need for multiple overlapping deposits. Experimental results show that compared to the traditional unidirectional equal-thickness slice deposition method (deposition time of 4072.4 s), this strategy significantly shortens the preparation time of the inclined ring structure (deposition time of 2214.4 s), improves material deposition efficiency by approximately 45.62%, significantly increases raw material utilization, and substantially reduces manufacturing costs.

[0044] Step 6: Use a laser binocular vision scanner (TrackScan series P550) to scan the formed inclined ring structure, and compare the scanned reverse model with the theoretical model. Figure 7 By directly superimposing and comparing the actual cross-sectional outline (solid line) of half of the formed part with the outline (dashed line) of the theoretical model through the cross-sectional view, the actual model can completely enclose the theoretical model, and the two have a high degree of consistency, and the forming is complete.

[0045] Example 1 shows that the formed part meets the geometric requirements of the inclined ring structure. Compared with the traditional casting process, it improves material utilization, shortens the manufacturing cycle, and reduces the finishing cost.

[0046] 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 within the protection scope of the present invention.

Claims

1. A method for additive manufacturing of complex curved surface structures using arc-fused wire based on slices of equal arc length, characterized in that, The steps are as follows: Step 1: Using 3D modeling software, construct a 3D model of a complex curved surface structure. Extract the outer wall contour envelope curve (1) formed by fitting circular arc segments within the center line section of the 3D model. Cut the outer wall contour envelope curve (1) into segments with equal arc lengths. Step 2: At each dividing point (11), construct a radius line (2) that connects the dividing point to the center of the circle. Rotate the radius line around the center line (3) of the part model to form a surface of revolution (13). Use this surface as the dividing surface to slice the part model into layers and generate an additive manufacturing trajectory. Step 3: Pre-deposit two metal cladding layers on the substrate as a base to avoid interference between the welding gun and the substrate during the subsequent additive manufacturing process, and at the same time fill the bottom area of ​​the complex curved surface structure to facilitate high-precision contour forming. Step 4: Following the additive manufacturing path generated in Step 2, use an arc additive manufacturing machine tool with five-axis linkage to additively form the part. The CNC system of the machine tool coordinates the movement of the welding torch and the tilting and rotation of the worktable in real time to ensure that at each deposition point, the direction of the welding torch is along the tangent of the path, and the distance between the welding torch and the surface of the deposition layer is constant, and the wire length remains stable. In this way, the metal material is deposited layer by layer along the preset path until the additive manufacturing of the entire tilted ring structure is completed.

2. The method for additive manufacturing of complex curved surface structures based on equal-arc-length slices using arc-fused wire according to claim 1, characterized in that, The complex curved surface structure is an inclined ring structure with a maximum inclination angle exceeding 45°, and its outer wall contour can be enveloped by arc segments. The number of arc segments is determined according to the shape of the inclined ring structure, and is one or more continuous arc segments.

3. The method for additive manufacturing of complex curved surface structures based on equal-arc-length slices using arc-fused wire according to claim 1, characterized in that, In step 1, the arc length is calculated using equation (1). L corresponding central angle The arc length is divided equally by dividing the central angle equally: ； In the formula, Central angle, unit: radians; Arc length, unit: millimeters; The radius of the arc at that point is expressed in millimeters.

4. The method for additive manufacturing of complex curved surface structures based on equal-arc-length slices using arc-fused wire according to claim 1, characterized in that, In step 4, the actual height of the single-layer structure deposited by the electric arc wire additive deposition is equal to the length of the equally divided arc. L .

5. The method for additive manufacturing of complex curved surface structures based on equal-arc-length slices using arc-fused wire according to claim 1, characterized in that, The specific implementation process of step 2 is as follows: Within the cross-section passing through the center line of the 3D model, each slice is regarded as a rectangular cross-section, and the height of the center point of the rectangular cross-section is recorded. h Horizontal distance from the center point to the center line of the model s and the angle between the short side of the rectangular cross-section and the vertical direction. α， This included angle is the tilt angle, which determines how much the machine tool table needs to tilt during the deposition process to match the welding torch posture; the recorded data h , s , α The additive manufacturing trajectory is generated by inputting it into the machine tool control system.

6. The method for additive manufacturing of complex curved surface structures based on equal-arc-length slices using arc-fused wire according to claim 1, characterized in that, In step 3, the metal cladding material used as the substrate is the same as the welding wire material.

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