A support-free reinforcement method for cantilever structures based on printing with variable layer heights on the same slice

Abstract

The present invention discloses a support-free reinforcement method for cantilever structural parts based on variable layer height printing of the same slice layer in the field of 3D printing. The method connects the diagonal points of each quadrilateral of the horizontal arm and the vertical arm, divides them into six triangular facets, selects the angle of the self-supporting plane according to the size of the overhang angle, extends the inner side surface of the vertical arm upward to intersect with the upper surface of the horizontal arm, rotates the extended plane toward the outer side surface of the vertical arm to form a dividing interface, and translates the dividing interface downward to obtain the self-supporting plane; the horizontal arm and the vertical arm are sequentially cut into inclined wire laying layers with different layers of variable layer height, smooth inclined layers generated by printing with the same layer of variable layer height, and horizontal wire laying layers. The smooth inclined layers are printed according to the layer angle and number of layers of each variable layer height printing, or a slope layer is pre-generated first, and then a smooth inclined layer is printed on the slope layer based on the slope layer; a smooth and continuous curved surface is formed by adjusting the layer height difference of the wire laying, eliminating the gap in the self-supporting plane, effectively increasing the contact surface between layers in the connection area, and increasing the adhesion between layers.

Description

Technical Field

[0001] The present invention relates to the field of 3D printing of cantilever structural parts. Different from the different-layer variable-height printing technology, it is a variable-height printing method of cantilever structural parts on the same layer. Specifically, it is a method for reinforcing unsupported 3D printing by changing the layer height of the same layer of cantilever structural parts. Background Art

[0002] Cantilevered components are common in 3D printing, characterized by one end suspended in mid-air. They feature a simple structure, concentrated loads, a suspended free end, and significant bending and deflection. They are commonly found in 3D printed parts, such as automotive hulls and complex models, requiring extensive support. Special attention must be paid to the strength and stability of the support points to ensure the structure remains stable under external loads. However, printing supports wastes significant amounts of printing material and increases printing time, and removing the support material can also compromise the surface quality of the printed part.

[0003] Support-free printing technology allows cantilever structures to be printed without supports. Its principle is to create a self-supporting surface by dividing the printed model through oblique slicing. When generating a self-supporting surface, traditional support-free printing identifies inclined layered areas and performs segmented slicing. This creates stair-stepping patterns in the connection areas of the self-supporting surface. The wire-laying connection between the stair-stepping patterns and the inclined surface reduces the bonding area at the connection, resulting in insufficient adhesion strength. Therefore, it is necessary to minimize the printed pattern when printing self-supporting surfaces.

[0004] Existing variable layer height printing technology only changes the printing layer height of different layers to slightly improve the printing quality and connection strength. For example, China Patent Publication No. CN116872499A, named "A 3D printing method and system with variable layer height" and China Patent Publication No. CN116330431A, named "A particle printing device and method suitable for gantry-type variable layer height" are all traditional different layer variable layer height printing. This traditional different layer variable layer height printing method still uses the horizontal wire laying method to generate a self-supporting inclined surface, and cannot generate a smooth self-supporting inclined surface without layer patterns to increase the bonding area of ​​the connection area, thereby increasing the connection strength.

[0005] like Figure 1 The cantilever structure model shown in the figure will be printed without support first. Figure 2The segmentation shown is divided into a multi-degree-of-freedom printing area 1 and a traditional printing area 3. The horizontal section of the cantilever structure is the multi-degree-of-freedom printing area 1, and the vertical section is the traditional printing area 3. Between the multi-degree-of-freedom printing area 1 and the traditional printing area 3 is a self-supporting plane 2, which is also the connecting surface between the horizontal and vertical sections of the cantilever structure. The principle of support-free printing is to form a self-supporting plane 2 at the transition between the traditional printing area 3 and the multi-degree-of-freedom printing area 1 to support the area that originally needed support to achieve support-free printing. After the segmentation is completed, the segmented model is processed as follows Figure 3 The main difference between the slices of the traditional printing area 3 and the slices of the multi-degree-of-freedom printing area 1 is the different slicing directions. The traditional printing area 3 is a horizontal slice, and the multi-degree-of-freedom printing area 1 is an inclined slice. Figure 3 It can be seen that when the existing support-free printing technology prints the cantilever structure, there will be an obvious connection area where the horizontal slice and the inclined slice transition. This connection area is also the area of ​​the self-supporting plane 2. Figure 4 As shown, when the print head 5 is printing, the self-supporting plane 2 is printed by the horizontal wire laying 4 of the traditional printing, and the multi-degree-of-freedom printing area 1 is printed by the inclined wire laying 6, so the self-supporting plane 2 will appear as follows Figure 4 The densely packed stair-shaped lamination patterns 7 shown in the figure result in more gaps in the self-supporting surface 2, reducing interlayer adhesion when connecting the horizontal and inclined filament placements 4 and 6, and lowering the overall strength of the cantilever structure. Current variable-layer-height printing technology, which primarily varies the print height of different layers, can only slightly reduce the stair-shaped lamination patterns 7 during printing, but cannot effectively reinforce them. Summary of the Invention

[0006] The purpose of the present invention is to solve the problem of insufficient connection strength in the existing support-free printing technology, and to provide a support-free reinforcement method for cantilever structural parts that can be printed with variable layer heights in the same slicing layer. By changing the printing layer height of the same layer, a smooth inclined surface is generated when 3D printing cantilever structural parts, step-like layer patterns are eliminated, the bonding area is increased, the printing strength is enhanced, and better quality cantilever structural parts are obtained by support-free printing.

[0007] To achieve the above technical objectives, the present invention adopts a technical solution for the unsupported reinforcement method of a cantilever structure based on the same slice layer variable layer height printing: the outer end point of the bottom of the vertical arm of the cantilever structure 3D model is used as the origin, the vertical contour line of the outer side surface is the z-axis, the horizontal contour line of the bottom is the y-axis, and the horizontal plane perpendicular to the y-axis is the x-axis, including the following steps:

[0008] 1) Extend the lower surface of the horizontal arm to intersect with the outer surface of the vertical arm, and extend the inner surface of the vertical arm upward to intersect with the upper surface of the horizontal arm, so that two quadrilaterals are formed on the horizontal arm and one quadrilateral is formed on the vertical arm. Connect the diagonal points of each quadrilateral to split the model into six triangular facets;

[0009] 2): A vector starting from the outer side of the vertical arm and ending at the suspended end of the horizontal arm and parallel to the upper and lower surfaces of the horizontal arm is defined as a reference vector, and the angle between the z-axis and the reference vector is the overhang angle; extract the coordinates of the three vertices of each triangle, calculate the normal vector of each triangle and the vector angle between the normal vector of each triangle and the reference vector; select the angle α between the self-supporting plane and the y-axis according to the size of the overhang angle, and divide the triangle area to which the normal vector corresponding to the vector angle belongs into an overhang area and a non-overhang area;

[0010] 3) Extend the inner side of the vertical arm upward until it intersects with the upper surface of the horizontal arm, rotate the extended plane toward the outer side of the vertical arm to a position where the angle with the y-axis is α, and the rotated plane is the interface. The interface is translated downward to obtain a self-supporting plane;

[0011] 4) The horizontal arm and the vertical arm are sequentially cut into inclined fiber-laying layers with different variable layer heights, smooth inclined layers generated by printing at the same variable layer height, and horizontal fiber-laying layers. The inclined fiber-laying layers with different variable layer heights are located in the overhang area and partially located in the non-overhang area. The smooth inclined layers and the horizontal fiber-laying layers are located in the non-overhang area.

[0012] 5): When h2*n≤L1m, L 1m It is the height from the intersection F of the lower surface contour line of the horizontal arm 8 and the inner side contour line of the vertical arm to the top surface of the horizontal wire laying layer, h2 is the minimum layer height of the same layer, n is the number of printing layers, and the smooth inclined layer is printed according to the printing angle of each variable layer height and the corresponding number of printing layers; when h2*n>L1m, a bevel layer is pre-generated first, and then a smooth inclined layer is printed on the bevel layer based on the pre-generated bevel layer to generate a reinforcement area.

[0013] Furthermore, in step 5), each layer of the variable layer height printing angle h1 is the maximum height of the same floor, h2 is the minimum height of the same floor, γn is the angle between the self-supporting plane and the z axis, γ n-1 is the angle between the variable height printing layer n-1 and the z-axis, A1 is the length of the bottom edge of the vertical arm along the y-axis, and A n is the length of the self-supporting plane.

[0014] Furthermore, in step 5), each layer of the smooth inclined layer above the bevel layer has a variable layer height printing angle. h1 is the maximum height of the same layer in the smooth inclined layer above the slope layer, h2 is the minimum height of the same layer, A n is the length of the self-supporting plane, and β is the angle between the uppermost inclined surface of the pre-generated inclined surface layer and the y-axis.

[0015] Furthermore, the angles of each layer of variable height printing are superimposed one after another, and when the angle is satisfied Get the number of printing layers.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] Different from the existing printing technology with different layers and variable heights, the unsupported 3D printing is reinforced by changing the layer height of the same layer. When printing cantilever structural parts without support, the existing unsupported printing technology will produce stepped layer patterns when printing the necessary self-supporting planes. It is impossible to generate smooth self-supporting inclined surfaces without layer patterns to increase the bonding area of ​​the connection area. It can only change the printing layer heights of different layers to slightly improve the printing quality and connection strength, but the improvement is far from enough. The present invention uses the same slice layer variable height printing technology to control the extrusion amount of the print nozzle in real time, so that the printing layer height of the same slice layer can change evenly during the printing process. By adjusting the layer height difference of the wire laying, a smooth and continuous curved surface is formed, the gap of the self-supporting plane is reduced or even eliminated, and the interlayer contact surface of the connection area is effectively increased, thereby increasing the interlayer adhesion, improving the connection strength of the connection area and the overall strength of the cantilever structure, and greatly improving the overall quality of the unsupported printed cantilever structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described below with reference to the accompanying drawings.

[0019] Figure 1 It is a schematic diagram of the cantilever structure model;

[0020] Figure 2 yes Figure 1 Schematic diagram of the unsupported printing segmentation of the cantilever structure model;

[0021] Figure 3 yes Figure 2 Schematic diagram of unsupported printing slices;

[0022] Figure 4 Print head pair Figure 3 Schematic diagram of printing of the self-supporting plane;

[0023] Figure 5 is a cantilever structure model in an embodiment of the present invention;

[0024] Figure 6 yes Figure 5Normal vector marker diagram of the cantilever structure model;

[0025] Figure 7 is based on Figure 6 Schematic diagram of self-supporting partitioning;

[0026] Figure 8 is based on Figure 7 A magnified schematic diagram of the slice layered structure and some dimension markings;

[0027] Figure 9 This is a schematic diagram of printing variable layer height filament;

[0028] Figure 10 This is a schematic diagram of variable height printing layer generation;

[0029] Figure 11 It is a schematic diagram of generating a bevel layer with variable layer height in advance;

[0030] Figure 12 It is a self-supporting planar diagram using traditional variable layer height printing;

[0031] Figure 13 It is a schematic diagram of a self-supporting plane printed with the same variable layer height in the present invention.

[0032] In the figure: 1. Multi-degree-of-freedom printing area; 2. Self-supporting plane; 3. Traditional printing area; 4. Horizontal wire laying; 5. Print nozzle; 6. Inclined wire laying; 7. Stepped layer pattern; 8. Horizontal arm; 9. Vertical arm; 10. Inclined surface. DETAILED DESCRIPTION

[0033] The present invention proposes a new non-supported variable layer height printing reinforcement method for the same slice layer of a cantilever structure, wherein the lower surface of the horizontal arm of the cantilever structure is extended to intersect with the outer side surface of the vertical arm, and the inner surface of the vertical arm is extended upward to intersect with the upper surface of the horizontal arm, so that two quadrilaterals are formed on the horizontal arm and one quadrilateral is formed on the vertical arm, and the diagonal points of each quadrilateral are connected to divide the model into six triangular facets; a vector starting from the outer side surface of the vertical arm to the suspended end of the horizontal arm and parallel to the upper and lower surfaces of the horizontal arm is defined as a reference vector, and the angle between the z-axis and the reference vector is the overhang angle; the coordinates of the three vertices of each triangular facet are extracted, and the normal vector of each triangular facet and the vector angle between the normal vector of each triangular facet and the reference vector are calculated; the self-supporting facet is selected according to the size of the overhang angle. The angle α between the supporting plane and the y-axis is divided into the overhang area and the non-overhang area according to the triangular patch area to which the normal vector corresponding to the vector angle belongs; the inner side surface of the vertical arm is extended upward to intersect with the upper surface of the horizontal arm, and the extended plane is rotated toward the outer side surface of the vertical arm to a position with an angle α with the y-axis. The rotated plane is the interface, and the interface is translated downward to obtain a self-supporting plane; the horizontal arm and the vertical arm are cut into different layers of variable layer height inclined wire laying layers, the same layer of variable layer height printing generated smooth inclined layers and horizontal wire laying layers in sequence, the different layers of variable layer height inclined wire laying layers are in the overhang area and partially in the non-overhang area, the smooth inclined layers and the horizontal wire laying layers are in the non-overhang area; when h2*n≤L1m, L 1m It is the height from the intersection F of the lower surface contour line of the horizontal arm 8 and the inner side contour line of the vertical arm to the top surface of the horizontal wire laying layer, h2 is the minimum layer height of the same layer, n is the number of printing layers, and the smooth inclined layer is printed according to the printing angle of each variable layer height and the corresponding number of printing layers; when h2*n>L1m, a bevel layer is pre-generated first, and then a smooth inclined layer is printed on the bevel layer based on the pre-generated bevel layer to generate a reinforcement area. The present invention controls the extrusion amount of the print nozzle in real time so that the printing layer height of the same slice layer can change evenly during the printing process; by adjusting the layer height difference of the wire laying, a smooth and continuous curved surface is formed, the gap of the self-supporting plane is reduced or even eliminated, and the interlayer contact surface of the connection area is effectively increased to increase the interlayer adhesion, thereby increasing the connection strength of the connection domain, and greatly improving the overall quality of the unsupported printed parts. Figure 5 Take the cantilever structure shown in the figure as an example, and perform reinforcement printing with variable layer height on it in the same slice, specifically:

[0034] (1) First, Figure 5 The cantilever structure shown in the figure is used to obtain its 3D model through a 3D scanner. Figure 6 As shown, the three-dimensional model of the cantilever structure is formed by a horizontal arm 8 and a vertical arm 9 to form an L-shaped or V-shaped structure. The common part of the horizontal arm 8 and the vertical arm 9 is the fixed end of the horizontal arm 8, which is also the upper end of the vertical arm 9. The end of the horizontal arm 8 away from the fixed end is the suspended end.

[0035] Then import the 3D model of the cantilever structure into the slicing software and adjust it to the appropriate printing position through 3D transformation.

[0036] (2) After the three-dimensional model of the cantilever structure is in a suitable printing position, the outer end point of the bottom of the vertical arm 9 of the cantilever structure three-dimensional model is used as the origin o, the vertical contour line of the outer side of the vertical arm 9 is used as the z-axis direction, the horizontal contour line of the bottom of the vertical arm 9 is used as the y-axis direction, and the direction perpendicular to the y-axis on the horizontal plane is used as the x-axis direction to establish the xyz coordinate axis. The lower surface of the horizontal arm 8 and the inner surface of the vertical arm 9 of the cantilever structure are extended. The lower surface of the horizontal arm 8 is extended to intersect with the outer side of the vertical arm 9, that is, intersect with the z-axis. The inner surface of the vertical arm 9 is extended upward to intersect with the upper surface of the horizontal arm 8. In this way, two quadrilaterals are formed on the horizontal arm 8 and one quadrilateral is formed on the vertical arm 9. The diagonal points of each quadrilateral are connected to divide the model into triangular facets of unit area, a total of six triangular facets, such as Figure 6 The six triangles shown in .

[0037] (3) After the triangular facets are segmented, a reference vector is defined as the reference vector. A vector M starting from the outer side of the vertical arm 9 and extending to the suspended end of the horizontal arm 8 and parallel to the upper and lower surfaces of the horizontal arm 8 is defined as the reference vector. The angle between the z-axis and the reference vector M can be obtained, which is the overhang angle O.

[0038] Import the segmented triangular face model into commonly used related software, extract each triangular face, obtain the coordinates of the three vertices of each triangular face, and calculate the normal vector N of each triangular face through the coordinates of the three vertices of the triangular face. The calculation formula of the normal vector N is:

[0039] N=[(y2-y1)(z3-z1)-(z2-z1)(y3-y1)(z2-z1)(x3-x1)-(x2-x1)(z3-z1)(x2-x1)(y3-y1)-(y2-y1)(x3-x1)]

[0040] Among them, (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3) are the coordinates of the three vertices of each triangle.

[0041] (4) After obtaining the normal vector N of each triangle, the vector angle Ω between the normal vector N of each triangle and the reference vector M is calculated using the angle calculation formula. The calculation formula for the vector angle Ω is:

[0042] cosΩ=(M·N) / (|M|·|N|),

[0043] Where M is the reference vector, N is the normal vector of each triangle, and Ω is the angle between the reference vector M and the corresponding normal vector N.

[0044] (5) Figure 7 As shown in the figure, after obtaining the vector angle Ω of each triangle, the vector angle Ω is judged. When the vector angle Ω is ≤ 30°, the triangle area to which the normal vector N corresponding to the vector angle Ω belongs is divided into the overhang area A, otherwise the triangle area belongs to the non-overhang area B.

[0045] (6) After all triangular facets are distinguished into overhanging and non-overhanging areas, the angle Δ between the self-supporting plane and the horizontal direction, i.e., the y-axis direction, is determined according to the size of the overhang angle O. First, the overhang angle O is judged. When the overhang angle O≤30, the self-supporting plane angle α=0° is selected; when 30°<O≤60, the self-supporting plane angle α can be selected from any angle between 45° and 60°; when the overhang angle O>60, the self-supporting plane angle Δ can be selected from any angle between 30° and 45°. Embodiments of the present invention Figure 5 The overhang angle O of the cantilever structure model in is 80°, so the angle of the self-supporting plane Δ is selected as 30°.

[0046] After selecting the self-supporting plane angle α, since the inner side of vertical arm 9 extends upward in step 2 to intersect with the upper surface of horizontal arm 8, this extended surface is called plane C. Plane C is rotated toward the outer side of vertical arm 9 until its angle with the y-axis is equal to the self-supporting plane angle Δ. The rotated plane is named interface D, and the angle between interface D and the y-axis is equal to α. At this point, the vertical distance from the intersection of interface D and the outer side of vertical arm 9 to the bottom surface of vertical arm 9 (y-axis) is H1.

[0047] After obtaining the interface D, translate the interface D downward The plane obtained after the distance is called the self-supporting plane E.

[0048] (7) Figure 8 As shown, the three-dimensional model of the cantilever structure with the self-supporting plane E obtained is sliced ​​in different areas, and the slice layers are as follows Figure 8 The three slice layers shown are: a variable-height inclined layer M1, a smooth, inclined layer M2 generated by printing at the same variable height, and a horizontally placed layer M3, arranged from horizontal arm 8 and vertical arm 9. The variable-height inclined layer M1 should be located in overhang area A and partially in non-overhang area B. The smooth, inclined layer M2 and horizontally placed layer M3, generated by printing at the same variable height, should be located in non-overhang area B.

[0049] The three-layer slicing method is as follows: Given the total height of the cantilever structure 3D model is L5, and the height from the intersection F of the lower surface contour of horizontal arm 8 and the inner side contour of vertical arm 9 to the bottom of vertical arm 9 is L4, first calculate the z-axis height of the smooth inclined layer M2, L1 = h2 * n, based on the known minimum layer height h2 and the number of printed layers n.

[0050] To calculate the number of printing layers n, you need to first calculate the angle θ of each variable height printing layer n , where each layer has a variable height printing angle θ n The calculation formula is:

[0051]

[0052] Where h1 is the maximum height of the same floor, h2 is the minimum height of the same floor, γn is the angle between the self-supporting plane E and the z-axis, and γ n-1 is the angle between the variable height printing layer n-1 and the z-axis, A1 is the length of the bottom edge of the vertical arm 9 along the y-axis direction, and A n is the length of the self-supporting plane E.

[0053] By changing the layer height of each layer, the printing layer angle θ n The calculation formula is used to obtain the angle θ of each variable height printing layer n Then, according to the angle of the self-supporting plane Further calculate the number of printing layers n, that is, θ1, θ2. . . . . , θ n The cumulative superposition of The number of printing layers n is obtained.

[0054] After determining the z-axis height L1 of the smooth inclined layer M2, the z-axis height L3 of the horizontal fiber-laying layer M3 and the z-axis height L2 = L5 - L3 - L1 of the variable-height inclined fiber-laying layer M1 can be calculated using the formula L3 = H1 - H2 - L1. The top surface of the horizontal fiber-laying layer M3 is G. Therefore, the positions of the three slice layers M1, M2, and M3 can be determined based on the z-axis heights L2, L1, and L3.

[0055] The horizontal fiber layer M3 is printed using traditional 3D printing methods, the variable-height, tilted fiber layer M1 is printed using existing unsupported printing technology, and the smooth, tilted layer M2, generated by printing the same variable-height layer, is printed using the same variable-height printing method of the present invention. Since the horizontal fiber layer M3 and the variable-height, tilted fiber layer M1 use traditional slicing methods, they will not be described here.

[0056] When printing the smooth inclined layer M2 using the same layer variable height printing method, first select the layer height difference when printing the layer according to the situation. The layer height difference is generally between 0.1mm and 0.2mm. No specific requirements are made because the printing filament has layer height differences. After regular arrangement, it will be like Figure 9 As shown, an angled slope 10 is formed. Therefore, by continuously stacking the variable layer height printing filaments with layer height differences, the inclination angle of the slope 10 is continuously increased, and finally a self-supporting plane E is formed, wherein the angle control of the self-supporting plane E is the slope 10 formed by the superposition of the angles of all variable layer height printing layers. The stacking is shown as follows: Figure 8 shown.

[0057] (8) The same layer variable height printing method described in step (7) can be divided into two printing methods according to the actual situation:

[0058] Select the printing method according to the value of h2*n, and move the intersection F of h2*n, the contour line of the lower surface of the horizontal arm 8 and the contour line of the inner side of the vertical arm 9 to the height L of the top surface G of the horizontal fiber layer M3. 1m For comparison, when h2*n≤L1m, the first printing method is used, such as Figure 10 As shown, the smooth inclined layer M2 with a height of L1 on the z-axis is printed by the same variable layer height, that is, the layer angle θ is printed according to each variable layer height. n The slicing code of the layer can be obtained by importing the data into the slicing software. Because the realization of printing with different layer heights of the same slice layer relies on changing the extruder power to extrude printing filaments of different layer heights, the power configuration of the extruder is related to the volume S of the printing filament. The feed rate of the corresponding printer extruder is configured by the calculated printing filament volume. The calculation formula of the printing filament volume S is:

[0059]

[0060] Where t1 is the time when the extruder frequency changes each time, and the calculation formula of t1 is:

[0061]

[0062] Where S is the volume of the extruded filament, V 喷 is the moving speed of the printer nozzle, Vz is the moving speed of the printer nozzle along the z-axis, V 喷 Vz is selected by the printer configuration itself and is not a hard requirement.

[0063] Import the calculated filament volume S into the slicing software, replace the extrusion value in the slicing code, get the slicing code, import the Gcode file exported by the slicing software into the 3D printer for printing, and you will get Figure 5Cantilever structural member shown.

[0064] When h2*n>L1m, the second printing method is used, such as Figure 11 As shown, during the printing process, before printing the same variable height printed smooth bevel layer, a conventional method is used to generate an angled bevel layer M4. This bevel layer M4 is referred to as the pre-generated bevel layer M4. Then, on top of the pre-generated bevel layer M4, a smooth bevel layer M2 is printed on top of the same variable height printed bevel layer to generate a reinforcement area. The height L2m of the pre-generated bevel layer M4 can be any value as long as L2m+L1m≥h2*n is satisfied. Here, the angle θ of each variable height printing silk print layer M2 above the bevel layer is n1 The calculation formula is:

[0065]

[0066] Where h1 is the maximum floor height of the same layer in the smooth inclined layer M2, h2 is the minimum floor height of the same layer, and A n is the length of the self-supporting plane, and β is the angle between the uppermost inclined surface of the pre-generated inclined surface layer M4 and the y-axis.

[0067] θ is calculated by this formula n1 Then put it into the formula The same calculation is performed in θ 11 ,θ 12。。。。。。 ,θ 1n The number of printed layers n1 is obtained by the cumulative superposition of when the equation is satisfied, where α is the self-supporting plane angle of the printing method.

[0068] As with the first printing method, the printing layer angle θ is changed according to the layer height of each layer. n1 The corresponding number of printing layers can be obtained by importing the data into the slicing software to obtain the slicing code of the layer. The feed rate of the corresponding printer extruder is configured according to the calculated printing filament volume. The calculated printing filament volume is imported into the slicing software to obtain the slicing code. The Gcode file exported by the slicing software is imported into the 3D printer for printing. After printing, the slicing code is obtained. Figure 5 Cantilever structural member shown.

[0069] Figure 12 The figure shows the self-supporting plane structure using the existing traditional variable layer height printing and the same variable layer height printing. Figure 13 What is shown is a self-supporting planar structure printed with variable layer height on the same slice layer in the present invention. By comparing the two structures, it can be seen that the inclined surface generated by the self-supporting planar structure printed with variable layer height on the same slice layer in the present invention is smoother, the stepped layer pattern is eliminated, and the printing strength is enhanced.

Claims

1. A method for unsupported reinforcement of cantilever structures based on layer-by-layer printing with variable layer heights on the same slice, with the outer end point of the vertical arm bottom of the cantilever structure 3D model as the origin, the vertical contour line of the outer side as the z-axis, the horizontal contour line of the bottom as the y-axis, and the x-axis perpendicular to the y-axis on the horizontal plane, characterized by: The following steps are involved: 1) Extend the lower surface of the horizontal arm to intersect with the outer surface of the vertical arm, and extend the inner surface of the vertical arm upward to intersect with the upper surface of the horizontal arm, so that two quadrilaterals are formed on the horizontal arm and one quadrilateral is formed on the vertical arm. Connect the diagonal points of each quadrilateral to split the model into six triangular facets; 2): A vector starting from the outer side of the vertical arm and ending at the suspended end of the horizontal arm and parallel to the upper and lower surfaces of the horizontal arm is defined as a reference vector, and the angle between the z-axis and the reference vector is the overhang angle; extract the coordinates of the three vertices of each triangle, calculate the normal vector of each triangle and the vector angle between the normal vector of each triangle and the reference vector; select the angle α between the self-supporting plane and the y-axis according to the size of the overhang angle, and divide the triangle area to which the normal vector corresponding to the vector angle belongs into an overhang area and a non-overhang area; 3) Extend the inner side of the vertical arm upward until it intersects with the upper surface of the horizontal arm to form an extended plane, rotate the extended plane toward the outer side of the vertical arm to a position where the angle with the y-axis is α, and the rotated plane is the interface. The interface is translated downward to obtain a self-supporting plane; 4) The horizontal arm and the vertical arm are sequentially cut into inclined fiber-laying layers with different variable layer heights, smooth inclined layers generated by printing at the same variable layer height, and horizontal fiber-laying layers. The inclined fiber-laying layers with different variable layer heights are located in the overhang area and partially located in the non-overhang area. The smooth inclined layers and the horizontal fiber-laying layers are located in the non-overhang area. 5): When h2*n≤L1m, L 1m The height from the intersection F of the lower surface contour line of the horizontal arm and the inner side contour line of the vertical arm to the top surface of the horizontal wire laying layer, h2 is the minimum layer height of the same layer, and n is the number of printing layers. The smooth inclined layer is printed according to the printing angle of each variable layer height and the corresponding number of printing layers. When h2*n>L1m, a bevel layer is pre-generated first, and then a smooth inclined layer is printed on the pre-generated bevel layer to generate a reinforcement area. Each layer of variable height printing angle h1 is the maximum height of the same floor, h2 is the minimum height of the same floor, γn is the angle between the self-supporting plane and the z axis, γ n-1 is the angle between the variable height printing layer n-1 and the z-axis, A1 is the length of the bottom edge of the vertical arm along the y-axis, and A n is the length of the self-supporting plane; The printing angles θ1 and θ 2…… ,θ n Repeated superposition, when the angle is satisfied Get the number of printing layers when Each layer of the smooth inclined layer above the bevel layer has a variable layer height and a printing layer angle. h1 is the maximum height of the same layer in the smooth inclined layer above the slope layer, h2 is the minimum height of the same layer, A n is the length of the self-supporting plane, and β is the angle between the uppermost inclined surface of the pre-generated inclined surface layer and the y-axis.

2. The method for unsupported reinforcement of cantilever structures based on layer-by-layer printing with varying layer heights on the same slice according to claim 1 is characterized by: In step 2), when the vector angle Ω≤30°, the triangular patch area to which the normal vector N corresponding to the vector angle Ω belongs is divided into an overhang area, otherwise the triangular patch area belongs to a non-overhang area.

3. The method for unsupported reinforcement of cantilever structures based on layer-by-layer printing with varying layer heights on the same slice according to claim 1 is characterized by: In step 2), when the overhang angle 0≤30°, the included angle α=0°; when 30°<0≤60°, the included angle α is selected from 45° to 60°; when the overhang angle 0>60°, the included angle α is selected from 30° to 45°; In step 3), the interface is shifted downward Then the self-supporting plane is obtained; H1 is the vertical distance from the intersection of the interface and the outer side of the vertical arm to the y-axis.

4. The method for unsupported reinforcement of cantilever structures based on layer-by-layer printing with varying layer heights on the same slice according to claim 1 is characterized by: In step 4), the height of the smooth inclined layer on the z-axis is L1 = h2*n, the height of the horizontal fiber-laying layer on the z-axis is L3 = H1-H2-L1, and the height of the inclined fiber-laying layer with different layer heights on the z-axis is L2 = L5-L3-L1, where L5 is the total height of the cantilever structure.

5. The method for unsupported reinforcement of cantilever structures based on layer-by-layer printing with varying layer heights on the same slice according to claim 1 is characterized by: According to the printing layer angle θ n1 , when the angle When obtaining the number of printing layers of each variable layer height of the smooth inclined layer above the bevel layer.

6. The method for unsupported reinforcement of cantilever structures based on layer-by-layer printing with varying layer heights on the same slice according to claim 1 is characterized by: In step 2), the normal vector <h2 style=";text-align:left;direction:ltr">N = [(y2-y1)(<h2 style=";text-align:left;direction:ltr"> z <h2 style=";text-align:left;direction:ltr"> 3-z1)-(z2-z1)(y3-y1)(z2-z1)(x3-x1)-(x2-x1)(z3-z1)(x2-x1)(y3 -y1)-(y2-V1)(x3-x1)], (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3) are the coordinates of the three vertices of each triangle.

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