Cold spraying additive forming method
The active edge deposition control method in cold spray additive manufacturing addresses edge loss and controllability issues by pre-scanning and filling inner areas, achieving higher precision and stability in forming complex structures.
Patent Information
- Application Number
- CN202411291827.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-14
- Publication Date
- 2024-12-13
AI Technical Summary
The existing cold spray additive manufacturing process faces challenges with edge loss and poor controllability of deposition morphology due to the triangular cross-sectional profile of single tracks, leading to insufficient dimensional accuracy and limited forming types.
An active edge deposition control method is employed, involving pre-scanning the edge of each unit layer to establish a vertical contour, adjusting the spray scanning angle, and filling the inner area to form defect-free layers through controlled scanning trajectories.
This method enhances deposition control, ensures accurate edge formation, and improves the precision and stability of cold spray additive manufacturing by preventing over- or under-compensation, resulting in higher forming accuracy.
Smart Images
Figure CN119114961A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of additive manufacturing, and in particular to a cold spraying additive forming method. Background Art
[0002] Cold spray technology has become a new type of additive manufacturing (also known as 3D printing) process due to its extremely high deposition rate. When using cold spray for additive manufacturing of three-dimensional structures, the difficulty of the additive process lies in the forming mechanism of cold spray single-track deposition, which causes the cross-sectional profile of the single track to be triangular rather than flat. The reason for this forming mechanism is that during the aerodynamic acceleration process, the particle velocity at the center of the supersonic jet is usually higher than the particle velocity at the edge area, and the number of particles deposited in the center area of the track is also greater than that in the edge area. The cross-sectional profile of the spray-deposited single track is triangular, and as the unit deposition amount increases, the triangulation of the single track profile will become more obvious; the process of composite deposition forming using a single track will inevitably result in edge missing at the edge of the deposition unit layer, resulting in insufficient dimensional accuracy of the product in actual additive applications and limited forming types (see Figure 1 ). Summary of the invention
[0003] In order to solve the problem of edge loss in the forming process and improve the poor controllability of deposition morphology that is easily produced under the existing passive compensation method, a more active edge deposition control method is used to achieve more stable and higher-precision cold spray additive manufacturing of vertical sidewall unit layers. The present application provides a cold spray additive forming method.
[0004] The present application provides a cold spray additive forming method, which adopts the following technical solution:
[0005] A cold spraying additive forming method, characterized by comprising the following steps:
[0006] S1. Divide the model to be manufactured by additive manufacturing into multiple unit layers in parallel, and obtain the geometric data of each additive unit layer;
[0007] S2, adjusting the spray scanning angle between the spray gun and the substrate so that the current unit track presents a deposition morphology with one side perpendicular to the substrate;
[0008] S3, using the unit track to perform scanning unit track deposition along the edge contour line of the unit layer to construct an outer contour line of the unit layer with a vertical side wall;
[0009] S4, adjusting the spray gun to be perpendicular to the substrate or the surface of the deposited unit layer, scanning and filling the inner area of the unit layer contour, and forming a defect-free unit layer;
[0010] S5. Repeat the above process to complete the superposition deposition of different unit layers until the model is formed.
[0011] Optionally, there is a step S1.1 between step S1 and step S2, specifically: based on the unit layer thickness after slicing and the deposition performance index, setting the spraying gas pressure, gas temperature, powder supply rate, scanning speed and other process parameters.
[0012] Optionally, in step S2, the spraying angle of the tilted scanning should be between 50 and 80 degrees, wherein the manner of adjusting the spraying scanning angle includes fixing the substrate-tilting the spray gun, or fixing the spray gun-tilting the substrate.
[0013] Optionally, in step S2, it is necessary to compensate for the deposition effect of the current single track, and the compensation method includes: increasing the powder supply rate, reducing the scanning speed and multiple reciprocating depositions.
[0014] Optionally, in step S3, the spray focus track during tilt scanning should be offset along the unit layer contour to the inside of the contour, so that the outer vertical side wall of the deposited edge single track coincides with the target contour of the unit layer, wherein the offset distance d should be within the unit track width.
[0015] Optionally, step S4 is specifically as follows: after completing the construction of the unit layer edge contour, taking the end point of the inclined scan as the starting point of the vertical scan, adjusting the spraying angle to a vertical spraying angle, scanning and filling the inner area of the unit layer contour with the highest deposition efficiency to form a unit layer with defect-free edges.
[0016] Optionally, in step S4, the scanning trajectory during vertical scanning may be a reciprocating translation trajectory or a contour-contracting trajectory.
[0017] Optionally, in step S4, the end point of the vertical scan of the unit layer can be used as the starting point of the inclined scan of the edge single track in the next unit layer. If the end point of the vertical scan is located inside the unit layer rather than at the edge of the unit layer, the spraying distance can be increased and the unit layer can be quickly moved to the edge of the unit layer to start the inclined scan of the next unit layer.
[0018] In summary, this application includes the following beneficial technical effects:
[0019] The present invention pre-scans the edge of each unit layer, establishes the vertical contour edge, and then sprays and fills the center part, which is more conducive to controlling the deposition morphology of the entire unit layer and avoiding over-compensation or under-compensation that is prone to occur in the edge part in the comparison scheme. In addition, the spraying method is more controllable, the spraying focus at the edge is easier to determine, and the forming accuracy is higher. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a schematic diagram of defects in the prior art;
[0021] Figure 2 It is an overall flow chart of a cold spray additive forming method of the present application;
[0022] Figure 3 It is a schematic diagram of vertical scanning and oblique scanning in this application;
[0023] Figure 4 It is a schematic diagram of the spraying tilt angle and the spraying focus offset distance in this application;
[0024] Figure 5 It is a simplified schematic diagram of a cold spray additive forming method of the present application;
[0025] Figure 6 This is a schematic diagram of a specific finished product in an embodiment of the present application;
[0026] Figure 7 It is a schematic diagram of a specific finished product in an embodiment of the present application. DETAILED DESCRIPTION
[0027] The following is combined with Figure 1-7 This application is described in further detail.
[0028] The present application discloses a cold spraying additive forming method, which comprises the following steps:
[0029] S1. Slice and layer the target three-dimensional structure model based on additive manufacturing into multiple unit layers, and then obtain the plane data of each additive unit layer.
[0030] S1.1. Based on the unit layer thickness after slicing and the deposition performance index, the process parameters such as spraying gas pressure, gas temperature, powder supply rate, scanning speed, etc. are set.
[0031] S2, adjust the spray scanning angle α (i.e. the angle between the spray gun and the current deposition surface, see Figure 5 ), so that the current unit track has a deposition morphology with one side of the vertical outer wall. Due to different settings of the initial process parameters, the required tilt angles for achieving a nearly vertical wall on one side of the single track are also different. The spraying angle of the tilted scanning (the angle between the spray gun and the horizontal plane of the substrate) should be between 50 and 80°. An inclination angle close to 90° is difficult to achieve a single track with a vertical surface on one side, and an inclination angle below 45° leads to a significant decrease in deposition efficiency, which is too low in practical application value. The methods for achieving tilted scanning include fixed substrate-tilted spray gun, or fixed spray gun-tilted substrate.
[0032] In addition, after the tilted spraying angle deviates from the optimal deposition angle (i.e., 90°), the deposition efficiency will decrease, and the decrease will be more severe as the tilt angle increases. Therefore, it is necessary to compensate for the deposition effect of the current single track. The compensation methods include: increasing the powder supply rate, reducing the scanning speed, etc., so as to ensure that the deposition height of the edge single track is consistent with the preset unit layer thickness. In special cases, the deposition height of the edge single track is too low, and multiple reciprocating depositions can be adopted to ensure the deposition height.
[0033] In addition, the tilt direction of the tilt scan is tilted toward the outside of the unit layer deposition area, ensuring that the vertical side surface in the single track is the outside of the entire unit layer.
[0034] S3, using the unit track to perform scanning unit track deposition along the edge contour line of the unit layer to construct the outer contour line of the unit layer (the outer side of the contour line unit track is vertical).
[0035] In addition, since the vertical side wall of the single track is not the same point as the deposition center, the spray focus trajectory during tilt scanning should be offset inward along the contour of the unit layer so that the outer vertical side wall of the deposited edge single track coincides with the target contour of the unit layer. The offset distance d should range from 1 / 4 to 3 / 4 of the unit track width. The specific offset distance can be determined based on the process parameters and the tilt angle.
[0036] S4. After completing the construction of the edge contour of the unit layer, the end point of the inclined scan is used as the starting point of the vertical scan, and the spraying angle is adjusted to a vertical spraying angle (with the highest deposition efficiency) to scan and fill the inner area of the unit layer contour to form an edge defect-free unit layer.
[0037] In addition, the scanning trajectory during vertical scanning can be a reciprocating translation trajectory or a contour-contracting trajectory.
[0038] In addition, the end point after the completion of the vertical scan can be used as the starting point of the inclined scan of the edge single track in the next unit layer. If the end point of the vertical scan is located inside the unit layer but not at the edge of the unit layer, the spraying distance can be increased and the edge of the unit layer can be moved quickly to start the inclined scan of the next unit layer.
[0039] S5. Repeat the above process on different slice layers according to different unit layer forming requirements to complete the superposition deposition of different unit layers until the three-dimensional structure is formed.
[0040] The following are specific embodiments and specific data:
[0041] In the embodiment, a heat-conducting copper layer with a length, width and height of 80*80*6mm is additively manufactured on the surface of an aluminum plate with a length, width and height of 80*80*5mm, and a slicing software is used to digitally model it, and it is evenly cut into 12 unit layers with a layer thickness of 0.5mm, and the geometric dimensions of each unit layer are 80*80*0.5mm in length, width and thickness;
[0042] The following process parameters are set through the cold spray control system based on the additive requirements of the unit layer:
[0043] Vertical spraying process parameters: spraying gas pressure 3MPa, spraying gas temperature 450℃, powder supply rate 30g / min, scanning speed 200cm / min;
[0044] Tilt spraying process parameters: spraying gas pressure 3.5MPa, spraying gas temperature 450℃, powder supply rate 45g / min, scanning speed 200cm / min; (the deposition efficiency decreases during tilt spraying, and process compensation is required on the vertical spraying process parameters);
[0045] The spray gun angle was adjusted to tilt the spray gun so that the spray scanning angle α was 60°, and the outer contour of the unit layer was scanned when the spray gun was tilted; at the same time, when α was 60°, in order to ensure that the deposition height of the edge single track was consistent with the preset unit layer thickness, the compensation method of increasing the spray gas pressure and increasing the powder supply rate was adopted. Since the spray angle deviated from 90°, the powder deposition efficiency was reduced, and by increasing the spray gas pressure and increasing the powder supply rate, it was possible to maintain a similar powder deposition amount at a lower powder deposition efficiency.
[0046] In order to make the outer vertical sidewall of the deposited edge single track coincide with the target contour of the unit layer, based on the deposition width of the unit track using the cold spray system being 6 mm, the spray offset distance d was set to 3 mm, i.e. 1 / 2 of the effective deposition width.
[0047] After completing the construction of the edge contour of the unit layer, the end point of the inclined scan is used as the starting point of the vertical scan, and the spraying angle is adjusted to the vertical spraying angle to scan and fill the internal area of the unit layer contour. The scanning trajectory during vertical scanning is a reciprocating translation trajectory to form a unit layer with no edge defects.
[0048] The above process is repeated on different slice layers according to different unit layer forming requirements to complete the superposition deposition of different unit layers until the three-dimensional structure is formed. The end point after the completion of the vertical scan can be used as the starting point of the inclined scan of the edge single track in the next unit layer.
[0049] The actual picture of the thermal conductive copper layer finally manufactured by cold spray additive manufacturing is as follows Figure 6 and Figure 7 As shown, the upper surface of the copper layer has been ground and polished, and it can be seen that the edges and corners of the additively formed copper layer are clear, and there is no obvious loss on the edges around.
[0050] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.
Claims
1. A cold spray additive forming method, characterized in that The steps include: S1. Divide the model to be manufactured by additive manufacturing into multiple unit layers in parallel, and obtain the geometric data of each additive unit layer; S2, adjusting the spray scanning angle between the spray gun and the substrate so that the current unit track presents a deposition morphology with one side perpendicular to the substrate; S3, using the unit track to perform scanning unit track deposition along the edge contour line of the unit layer to construct an outer contour line of the unit layer with a vertical side wall; S4, adjusting the spray gun to be perpendicular to the substrate or the surface of the deposited unit layer, scanning and filling the inner area of the unit layer contour, and forming a defect-free unit layer; S5. Repeat the above process to complete the superposition deposition of different unit layers until the model is formed.
2. A cold spray additive forming method according to claim 1, characterized in that: There is also a step S1.1 between the step S1 and the step S2, which is specifically: based on the thickness of the unit layer after slicing and the deposition performance index, the process parameters such as the spraying gas pressure, gas temperature, powder supply rate, and scanning speed are set.
3. A cold spray additive forming method according to claim 1, characterized in that: In the step S2, the spraying angle of the tilted scanning should be between 50 and 80 degrees, wherein the manner of adjusting the spraying scanning angle includes fixing the substrate-tilting the spray gun, or fixing the spray gun-tilting the substrate.
4. A cold spray additive forming method according to claim 3, characterized in that: In the step S2, it is necessary to compensate for the deposition effect of the current single track, and the compensation method includes: increasing the powder supply rate, reducing the scanning speed and multiple reciprocating depositions.
5. The cold spraying additive forming method according to claim 1, characterized in that: In step S3, the spray focus track during tilt scanning should be offset inward along the unit layer contour so that the outer vertical side wall of the deposited edge single track coincides with the target contour of the unit layer, and the offset distance d should range from 1 / 4 to 3 / 4 of the unit track width.
6. The cold spray additive forming method according to claim 1, characterized in that: The step S4 is specifically as follows: after completing the construction of the edge contour of the unit layer, taking the end point of the inclined scan as the starting point of the vertical scan, adjusting the spraying angle to a vertical spraying angle, scanning and filling the inner area of the unit layer contour with the highest deposition efficiency, and forming a unit layer with defect-free edges.
7. A cold spray additive forming method according to claim 6, characterized in that: In the step S4, the scanning trajectory during vertical scanning can be a reciprocating translation trajectory or a contour-contracting trajectory.
8. A cold spray additive forming method according to claim 7, characterized in that: In step S4, the end point of the vertical scan of the unit layer can be used as the starting point of the inclined scan of the edge single track in the next unit layer. If the end point of the vertical scan is located inside the unit layer but not at the edge of the unit layer, the spraying distance can be increased and the unit layer can be quickly moved to the edge to start the inclined scan of the next unit layer.