A method for designing arc additive manufacturing paths for L-shaped structures with variable wall thickness based on low surface roughness and high material utilization.

Abstract

This invention provides a method for designing an arc additive manufacturing path for L-shaped structures with variable wall thickness based on low surface roughness and high material utilization, relating to the field of structural additive forming quality and material utilization. This invention employs a rounded-corner transition additive manufacturing path for L-shaped structures with thick and thin walls. Based on the thin-wall width d and thick-wall width D of the L-shape, as well as the minimum rounded-corner transition radius r and overlap spacing w, the number of additive passes for each part of the thick and thin walls is derived through angle-planning path optimization to improve additive utilization. The additive process is divided into two parts: the first part focuses on thin-wall additive manufacturing, ensuring that the width of the transverse and longitudinal cladding layers of the L-shape reaches the standard thin-wall width d, with an additive pass count of i1; the second part focuses on the remaining width of the thick wall, improving material utilization during the thick-wall width (D-d) additive manufacturing process, designing an additive pass count of i2. This invention provides a forming path method for L-shaped structure arc additive manufacturing with high forming accuracy and low material waste.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing forming quality optimization and material utilization technology, specifically to a method for designing arc additive manufacturing paths for L-shaped structures with variable wall thickness based on low surface roughness and high material utilization. Background Technology

[0002] In many fields such as automobiles, shipbuilding, and aerospace, modern high-end equipment is rapidly developing towards larger sizes and lighter weights. This has led to larger dimensions of some metal structural components and a greater number of areas involving complex structural features. Traditional manufacturing methods for these complex components mainly include casting, forging, and machining. However, these three methods have certain limitations, such as low forming accuracy and significant material waste. Arc additive manufacturing technology uses an electric arc as a heat source and metal welding wire as a supplementary material. The entire part is formed by the accumulation of weld seams. It has advantages such as high material utilization, excellent mechanical properties, and high forming efficiency, and can meet the production needs of large and complex structural components in the automotive, shipbuilding, and aerospace fields.

[0003] Special vehicles and ships with complex internal structures are generally composed of basic intersecting structural features. These intersecting structures are typically categorized into L-shapes, inclined intersecting shapes, and I-shapes, among others. These basic shapes constitute various types of complex intersecting structures. Within the overall structure, the surface forming accuracy and mechanical properties of the intersecting structures are closely related to the overall structural strength. During the arc additive manufacturing process for intersecting structures, severe bulging is prone to occur at the joints, resulting in significant forming accuracy errors. Furthermore, typical defects such as incomplete fusion and pitting may also occur, affecting structural strength.

[0004] For L-shaped cross structures produced by arc additive manufacturing, a right-angle transition additive manufacturing method is typically used. Furthermore, for L-shaped structures with varying wall thicknesses, a common method is to first add material of equal thickness and width, followed by subtraction processing based on the dimensions. This additive manufacturing method easily leads to significant forming accuracy errors and substantial material waste at the cross structure. Summary of the Invention

[0005] The purpose of this invention is to improve the arc additive manufacturing path design method for L-shaped structures with variable wall thickness based on low surface roughness and high material utilization. This method can improve the utilization rate of additive welding wire and improve the forming quality by means of path planning, taking into account the different widths of the L-shaped horizontal and vertical structures.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for designing arc additive manufacturing paths for L-shaped structures with variable wall thickness based on low surface roughness and high material utilization includes the following steps:

[0008] The first step involves exploring the minimum radius *r* for the fillet transition in an L-shaped arc additive manufacturing structure. A smaller fillet transition radius leads to buildup and protrusions at the intersection during additive manufacturing, while a larger radius results in an area difference on the inner side, increasing the welding torch travel path and reducing material utilization. The minimum fillet transition radius *r* ensures a smooth surface formation during buildup at the transition while minimizing the welding torch travel path. The optimal adjacent pass spacing *w* is selected based on material properties and welding process standards. The minimum fillet transition radius *r* and the optimal interpass overlap distance *w* in the L-shaped structure fillet transition are determined. Since the circles in the fillet transition are concentric and their radius variation is related to the minimum radius *r* and the pass spacing *w*, a formula for the radius *r* can be derived. A coordinate system is established with the center of the circle as the origin to obtain the standard equation of the circle in the fillet transition.

[0009] The second step is to determine the number of additive manufacturing passes i1 required in the actual additive manufacturing of the thin-walled structure based on the thin-walled dimension d of the L-shaped structure.

[0010] The third step involves using the thick-walled dimension D of the L-shaped structure as the starting boundary for subsequent additive manufacturing, based on the extension line of the center of the last cladding layer in the thin-walled region. This means constructing the starting line of the arc in the coordinate system with x = r + d + w as the boundary (where r is the minimum transition radius of the fillet, d is the thin-walled dimension of the L-shaped structure, and w is the spacing between adjacent passes). The standard equation of the arc is then calculated. Based on the thick and thin-walled dimensions D and d of the L-shaped structure, and combined with the standard equation of a circle, the actual additive width is ensured to be greater than the model width D, and the fillet transition radius r (i.e., the fillet width) is greater than the thick-walled width D. This is transformed into a geometric problem: in the fillet equation coordinate system, when x = r + d, y > D + r (where r is the minimum transition radius of the fillet, and D and d are the thick and thin-walled dimensions of the L-shaped structure). Substituting this relationship into the fillet equation, the total number of additive passes required is calculated.

[0011] The total number of additive manufacturing passes is calculated, and the number of additive manufacturing passes for the thin-walled portion is subtracted to obtain the number of additive manufacturing passes required to increase the width of the thick-walled portion.

[0012] Preferably, in the first step, the change in the fillet radius during the fillet transition and the standard equation of the circle are as follows:

[0013] r i = r + w(i-1) (i≥1)

[0014] x 2 +y 2 =(r i ) 2 =(r-w+wi) 2

[0015] In the formula, w is the spacing between adjacent passes, i is the number of additive passes, and wi is the expression after formula expansion, which is the spacing between adjacent passes w multiplied by the number of additive passes i.

[0016] Preferably, in the second step, the actual number of additive manufacturing passes required for thin-walled structures is:

[0017] Preferably, in the third step, to increase the width of the thick-walled portion, a rounded transition is directly applied from the starting line x = r + d + w. The standard equation of a circle is:

[0018] x 2 +y 2 =(r-w+wi) 2

[0019] Substituting x = r + d and y > D + r into the fillet equation according to the actual requirements, we obtain the relationship (2r + d - w + wi)(wi - wd) ≥ (D + r) 2

[0020] That is (wi) 2 +2(rw)wi-(2r-w+d)(w+d)-(D+r) 2 ≥0

[0021] In the formula, D, d, r, and w are all known constants. Therefore, (2r-w+d)(w+d)+(D+r) 2 For known constants

[0022] For ease of expressing the formula, let m = (2r - w + d)(w + d) + (D + r) 2

[0023] That is (wi) 2 +2(rw)wi-m≥0

[0024] The final formula for the total number of additive manufacturing passes is:

[0025]

[0026] In the formula, m = (2r + d)d + (D + r) 2 constant

[0027] Preferably, in the third step, the number of additive manufacturing passes i2 required to increase the wall thickness is equal to the total number of additive manufacturing passes i. 总 Subtract the number of additive manufacturing passes i1 required for thin-walled applications:

[0028]

[0029] The arc additive manufacturing path design method for L-shaped structures with variable wall thickness based on low surface roughness and high material utilization provided by this invention has the following significant advantages:

[0030] This invention employs a rounded corner transition method at the corners of L-shaped structures. Based on the minimum transition radius and the interlayer overlap distance, a standard equation is constructed for the rounded corner transition to satisfy the rounded corner. This avoids the phenomenon of height accumulation at the corners causing bulges and improves the forming quality of the metal cladding layer.

[0031] This invention addresses the issue of different widths in the transverse and longitudinal sections of L-shaped structures with varying wall thicknesses. First, the longitudinal thin-walled structure is additively processed to achieve the same width as the thin-walled structure. Then, for the transverse thick-walled structure, the center extension line of the last thin-walled additive process is used as the starting boundary for subsequent additive processes, and the starting point for subsequent rounded corner transitions is located on this extension line.

[0032] This approach improves upon the previous method of adding material to the maximum width of an L-shaped structure before subtracting it. It increases the thickness of the wall without affecting the already added thin-walled dimensions, thus greatly improving material utilization and forming efficiency without affecting the effective forming area.

[0033] The path model constructed in this invention is adaptable to different additive manufacturing methods for L-shaped structures of varying sizes with rounded corner transitions. It provides a forming path method for L-shaped structures with high forming accuracy and low material waste. Attached Figure Description

[0034] To more clearly illustrate the embodiments and design schemes of the present invention, the accompanying drawings required for this embodiment will be briefly described below.

[0035] Figure 1 This is a schematic diagram of an L-shaped structure model.

[0036] Figure 2 This is a schematic diagram of the path planning for an L-shaped structure.

[0037] Figure 3 A schematic diagram of the coordinate system for planning the path of an L-shaped structure.

[0038] Figure 4 This is a schematic diagram of the additive manufacturing process ending for an L-shaped structure.

[0039] Figure 5 The diagram shows the actual measurement results of the overlap distance and minimum fillet transition radius for a wire feed speed of 4.1 mm / s and a welding speed of 5 mm / s.

[0040] Figure 6 The theoretical dimensions of the additive manufacturing path are shown in the diagram, with a wire feed speed of 4.1 mm / s and a welding speed of 5 mm / s. Detailed Implementation

[0041] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific examples. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0042] This invention provides a method for designing arc additive manufacturing paths for L-shaped structures with variable wall thickness based on low surface roughness and high material utilization, comprising the following steps:

[0043] (1) Select the appropriate process parameters according to the welding wire. Explore the optimal overlap distance w through single-layer multi-pass linear additive manufacturing; use rounded corner transition to additively manufacture L-shaped structures, and adjust the process parameters to explore the minimum rounded corner transition radius r.

[0044] (2) Calculate the radius change of the circle in the fillet transition based on the minimum radius r of the fillet transition and the spacing w between adjacent lines. If the fillet transition circles are concentric circles, then the radius change is: r i =r + w(i-1) (i≥1), the rounded corner satisfies the standard equation: x 2 +y 2 =(r-w+wi) 2 wi is the expression for the distance between adjacent passes w multiplied by the number of additive passes i after the formula is expanded.

[0045] (3) Analyze the standard model of the L-shaped cross structure required for additive manufacturing, such as Figure 1 Based on the standard dimensions of the thin-walled material and the spacing between the additive manufacturing passes, the required number of additive manufacturing passes is calculated. In the actual additive manufacturing process, the actual width needs to be increased to allow for machining allowance in subsequent subtractive manufacturing processes. Therefore, one additional pass is required. The actual thin-walled width is d + w, and the actual number of additive manufacturing passes is:

[0046] (4) When the thin-walled width reaches the standard size, for the remaining additive width required for the thick-walled section, in order to simultaneously improve material utilization, x = r + d + w is used as the boundary, such as... Figure 3 Using the coordinate system shown, draw the starting line for subsequent additive manufacturing. The fillet equation remains: x 2 +y 2 =(r-w+wi) 2 .

[0047] (5) To ensure the actual wall thickness is D, it is necessary to explore the number of additive manufacturing passes i2 required to increase the wall thickness, which can be transformed into the mathematical problem: In Figure 3 In the coordinate system shown, when x = r + d, y ≥ D + r is required; substituting the above relationship into the standard equation of the fillet, we get the relationship (2r + d - w + wi)(wi - wd) ≥ (D + r). 2 , that is (wi) 2 +2(rw)wi-(2r-w+d)(w+d)-(D+r)2 The relationship between the total number of additive manufacturing passes and the formula for ≥0 is finally obtained by simplification and finding the root: Where m = (2r - w + d)(w + d) + (D + r) 2 m is a constant.

[0048] To achieve the required width for the thick-walled section, the actual number of additive manufacturing passes required to increase the width of the thick-walled portion is:

[0049]

[0050] Example 1

[0051] The following uses 304 stainless steel as an example to specifically verify the arc additive manufacturing path design method for a variable wall thickness L-shaped structure based on low surface roughness and high material utilization provided by the present invention.

[0052] The present invention provides a method for designing arc additive manufacturing paths for L-shaped structures with variable wall thickness based on low surface roughness and high material utilization to obtain the number of additive manufacturing passes required for each part during the fillet transition of the L-shaped structure. Specifically, this method includes:

[0053] (1) Using process parameters of wire feed speed 4.1 mm / s and welding speed 5 mm / s for additive manufacturing of 304 stainless steel, the optimal overlap spacing of 6 mm was obtained through single-layer multi-pass additive manufacturing; through process experiments, the minimum radius required for rounded corner transition forming was explored to be 8 mm, such as... Figure 5 As shown.

[0054] (2) The radius of the rounded transition circle is a concentric circle, and its variation is: r = 2 + 6i (i ≥ 1). The standard equation of the rounded corner is: x 2 +y 2 =(2+6i) 2 .

[0055] (3) For both thick and thin-walled parts, the standard width d of the thin-walled model is 30mm. In actual additive manufacturing, the actual width needs to be increased to allow for machining allowance in subsequent subtractive machining processes. Therefore, one additional pass is required. The calculated actual thin-walled width is: d + w = ​​36mm; the calculated actual number of additive manufacturing passes for the thin-walled part is:

[0056] (4) When the thin-walled width reaches the standard size, to improve material utilization, the remaining additive width required for the thick-walled section is used as the boundary to draw the subsequent additive starting line. The fillet equation remains the same: x 2 +y 2 =(2+6i) 2 .

[0057] (5) To ensure that the actual wall thickness is D, it is necessary to explore the number of additive layers i, which can be transformed into a mathematical problem: In the coordinate system, when x = r + d = 38, y ≥ 68; Substituting the above values ​​into the relation (2r + d - w + wi)(wi - wd) ≥ (D + r) 2 The total number of additive manufacturing passes is obtained as: i 总 If ≈13, then the number of additive passes i2 = 6 for the width of the additive thick wall.

[0058] (6) Substitute the calculated values ​​into the teach pendant programming, setting the number of additive manufacturing passes for thin-walled parts to 7, the number of additive manufacturing passes for thick-walled parts to 6, and the total number of additive manufacturing passes to 13. Dimensions of the additively manufactured parts are measured. Since the path diagrams all represent the center lines of the cladding layer, the actual additive width is greater than the width shown in the path diagrams. After additive manufacturing, the thin-walled width of the L-shaped structural part is 46mm, and the thick-walled width is 82mm. When the thin-walled width is 30mm, the measured thick-walled width is 63mm. The actual width is greater than 60mm, satisfying the geometric dimensional requirements, and the material utilization rate is increased to 80%. Verification shows that this path can both optimize the forming quality and improve material utilization.

[0059] This application explores the planning of a reasonable additive manufacturing path, aiming to improve the forming accuracy and material utilization of the L-shaped cross structure by arc additive manufacturing. The L-shaped cross structure connection is made using a rounded transition method for additive manufacturing, and the optimal number of additive passes required to meet the model size is explored through model formulas.

Claims

1. A method for designing arc additive manufacturing paths for L-shaped structures with variable wall thickness based on low surface roughness and high material utilization, characterized in that, Includes the following steps: The first step is to determine the minimum fillet transition radius. The principle determines the minimum radius for the fillet transition of the L-shaped structure. Select the spacing w between adjacent passes based on material properties and welding process standards; determine the minimum fillet transition radius. After determining the distance w between adjacent lanes, and based on the fact that the fillet transition circles are concentric circles, the fillet radius r can be obtained. i With the number of additive manufacturing passes The formula for the change of the circle is used to establish a coordinate system with the center of the circle as the origin, and finally the standard equation of the circle is obtained. The second step is to determine the width of the L-shaped thin-walled structure. Determine the actual number of additive manufacturing passes for thin-walled materials. ; The third step is to determine the width of the L-shaped thick wall. The center extension line of the last cladding layer in the thin-walled region is used as the starting boundary for subsequent additive manufacturing, and the starting point for subsequent rounded corner transitions is located on this extension line; based on the thick and thin wall dimensions of the L-shaped structure... and To ensure that the actual width of the additive manufacturing is greater than the width of the model. That is, the radius of the fillet is greater than the width of the thick wall. In the coordinate system of the rounded corner equation, the geometric relationship is as follows: When y > D + r, substituting the relation into the fillet equation, the total number of additive manufacturing passes can be calculated. Finally, subtract the number of additive manufacturing passes required for thin-walled applications from the total number of additive manufacturing passes to obtain the number of additive manufacturing passes required to increase the width of thick-walled applications, i2. In the third step, a rounded transition arc is initiated at the boundary where x = r + d + w. Based on the relationships in the coordinate system, when x = r + d... Substitute into the standard equation for fillet: get: Right now ; In the formula, wi is the product of the spacing between adjacent passes w and the number of additive passes after the formula is expanded. expression; In the formula , , Both and w are known constants, therefore in the formula It is a known constant; To simplify the expression of the formula, let ; Right now ; The final formula for the total number of additive manufacturing passes is: Number of additive manufacturing passes required to increase the width of thick walls Equal to the total number of additive manufacturing passes The critical value minus the number of additive manufacturing passes required for thin-walled applications :

2. The method for designing an arc additive manufacturing path for a variable wall thickness L-shaped structure based on low surface roughness and high material utilization, as described in claim 1, is characterized in that... In the first step, if the fillet radius is too small, it will cause accumulation at the intersection, creating a height difference. If the fillet radius is too large, it will cause an area difference on the inner side, increasing the welding torch travel path and reducing material utilization. The minimum fillet radius... The principle is to ensure a smooth surface when the material accumulates at the transition point, while minimizing the travel path of the welding torch.

3. The method for designing an arc additive manufacturing path for a variable wall thickness L-shaped structure based on low surface roughness and high material utilization, as described in claim 1, is characterized in that... In the first step, the rounding radius r i The standard equation of a circle is: r i =r+w(i-1) Expand to get x 2 +y 2 =(r-w+wi) 2 In the formula, w is the distance between adjacent lanes. To increase the number of material passes, ≥1, The minimum fillet radius is given by wi, where wi is the product of the distance between adjacent passes w and the number of additive passes after formula expansion. expression.

4. The method for designing an arc additive manufacturing path for a variable wall thickness L-shaped structure based on low surface roughness and high material utilization, as described in claim 1, is characterized in that... In the second step, the actual number of thin-wall additive manufacturing passes required is: 。

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