A 3D concrete printing path planning method using complex surface layering

Abstract

The present invention discloses a 3D concrete printing path planning method using complex surface layering, including: generating a model of a concrete component; extracting the top edge curve of the model and converting it into a Nurbs curve; converting the Nurbs curve into a Nurbs surface with a UV direction; determining a slice reference plane, projecting the Nurbs surface onto the slice reference plane, and forming an array space surface; calculating the number of printing layers between two adjacent slice reference planes according to the maximum height difference between two adjacent slice reference planes within the model range and the target height of each layer of printing path; performing surface gradient calculation on the space surface, generating a corresponding number of tangent surfaces between each reference plane and the top Nurbs surface; slicing the model using the slice surface, and generating a gradient curve printing path. The present invention is suitable for printing components with irregular top morphology, can achieve the transition between complex surfaces and regular space planes (or surfaces), and can effectively control the printing height.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing concrete, and more specifically to a 3D concrete printing path planning method using complex surface layering. Background Art

[0002] The main principle of 3D printing concrete to achieve geometric forming is to let the print head move along a specific printing path during the printing process. At the same time, the pumping system transports the mixed concrete printing material to the print head through a pipeline, and the print head extrude the concrete printing material. The earliest printing path planning method proposed in the field of 3D printing concrete is the horizontal layer-by-layer printing method. In this type of printing process, the designer uses contour-style slicing logic to slice the component model in the computer at equal intervals, and transforms the three-dimensional model into a layer-by-layer two-dimensional printing path. Subsequently, the field of 3D printing concrete has derived a path planning method for printing along a curved surface. By moving the robotic arm along the surface of a curved template (such as a sphere), the extruded concrete printing material is attached to the curved template, thereby producing a more varied morphological effect.

[0003] Although 3D printed concrete has demonstrated many possibilities for achieving complex concrete shapes, some changes are irregular, especially the shapes with large fluctuations on the top of the component cannot be sliced ​​with a regular plane or curved surface. Therefore, the printing of the corresponding components cannot be achieved by layer-by-layer printing or curved surface printing. Moreover, unlike regular curved surfaces such as spheres and ellipses, the changes in the UV coordinates of complex curved surfaces in space are irregular. At the same time, when the bottom and top surfaces of a model are not parallel to each other, the printing path generated by slicing the model will inevitably have changes in layer height. If the height of each layer of the printing path cannot be effectively controlled to maintain it within a suitable range for printing, it is easy to cause material accumulation or insufficient feed.

[0004] Therefore, how to provide a 3D concrete printing path planning method using complex surface layering that is suitable for irregular top shapes of components, can achieve the transition between complex curved surfaces and regular spatial planes (or curved surfaces), and can effectively control the printing height during 3D printing is a problem that technicians in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention provides a 3D concrete printing path planning method using complex surface layering, which is suitable for printing components with irregular top shapes, can achieve the transition between complex surfaces and regular spatial planes (or surfaces), and can effectively control the printing height during the 3D printing process.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A 3D concrete printing path planning method using complex surface layering, comprising:

[0008] Generate a three-dimensional model of the concrete component and determine whether the three-dimensional model meets the preset surface layering standard;

[0009] Under the condition of meeting the preset surface layering standard, the top edge curve of the 3D model is extracted and converted into a Nurbs curve;

[0010] Convert Nurbs curves into Nurbs surfaces with UV directions;

[0011] Determine the slice reference plane and project the Nurbs surface onto the slice reference plane to form a spatial surface with the same UV coordinate composition logic but different spatial forms.

[0012] Calculate the number of printing layers between two adjacent slice reference planes according to the maximum height difference between two adjacent slice reference planes within the model range and the target height of each layer printing path;

[0013] Perform surface gradient calculation on the formed array space surface, and generate a corresponding number of slice surfaces between each reference plane and the top Nurbs surface;

[0014] Use the slicing surface to slice the 3D model and generate a gradient curve printing path.

[0015] Furthermore, in the above-mentioned 3D concrete printing path planning method using complex surface layering, it also includes:

[0016] Each gradient curve printing path is offset by a certain distance into the 3D model according to the preset printing width.

[0017] Furthermore, in the above-mentioned 3D concrete printing path planning method using complex surface layering, the offset distance is 1 / 2 of the preset printing width.

[0018] Furthermore, in the above-mentioned 3D concrete printing path planning method using complex surface layering, it also includes:

[0019] Each gradient curve is divided into continuous positioning points using the method of equidistant breakpoints;

[0020] The normal direction corresponding to the positioning point in the gradient curve is used as the Z direction, and the U coordinate direction is used as the X direction to generate the three-dimensional rectangular coordinates of each positioning point as the initial coordinate position of the robot arm at each positioning point.

[0021] Furthermore, in the above-mentioned 3D concrete printing path planning method using complex surface layering, it also includes:

[0022] Adjust the initial coordinate position of each positioning point according to the printing environment and robot arm model.

[0023] Furthermore, in the above-mentioned 3D concrete printing path planning method using complex surface stratification, the preset surface stratification standard is:

[0024] The top edge curve of the 3D model is not on the 3D space plane or the regular surface, and the bottom curve of the 3D model is on the 3D space plane.

[0025] Furthermore, in the above-mentioned 3D concrete printing path planning method using complex surface layering, the calculation formula for the number of printing layers between two adjacent slice reference planes is:

[0026] n=int((H max -H min ) / h

[0027] Where n is the number of printing layers between two adjacent slice reference planes; H max H is the maximum height of two adjacent slice reference planes within the model range; min It is the minimum height of two adjacent slice reference planes within the model range; h is the target height of each layer of printing path, and its value range is 6mm-18mm.

[0028] Furthermore, in the above-mentioned 3D concrete printing path planning method using complex surface layering, each slice reference plane is determined according to the morphological change trend of the three-dimensional model.

[0029] Furthermore, in the above-mentioned 3D concrete printing path planning method using complex surface layering, the layer heights of the gradient curve printing paths of each layer vary evenly.

[0030] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a 3D concrete printing path planning method using complex surface layering, which has the following beneficial effects:

[0031] 1. The present invention solves the transition problem between the bottom plane and the top surface in the 3D printing path planning of complex components by using computer-aided design software and visual programming language, by converting the top edge of the complex component into a Nurbs surface and reprojecting the Nurbs surface to other reference planes.

[0032] 2. The present invention solves the problem of height control in the process of complex surface slicing by extracting and calculating the top edge extreme point elevation data of complex components and combining the method of gradual change between curved surface and plane, avoiding the accumulation of materials and insufficient feeding due to inappropriate path height. The purpose of 3D printing path generation for complex concrete forms with obvious top undulations is achieved.

[0033] 3. The present invention solves the technical difficulty of converting complex surface slices into a locatable coordinate system by associating the robot arm positioning point with its corresponding normal direction in the surface slice, and realizes a technical method for moving the robot arm in accordance with the normal direction of the surface slice. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0035] Figure 1 A flow chart of a 3D concrete printing path planning method using complex surface layering provided by the present invention;

[0036] Figure 2 It is a schematic diagram of gradual layering of a complex curved surface and a reference plane in the first embodiment of the present invention;

[0037] Figure 3 It is a structural schematic diagram of components in Embodiment 2 of the present invention;

[0038] Figure 4 Schematic diagram of gradual layering of a complex curved surface and multiple reference planes in the second embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] like Figure 1 As shown, an embodiment of the present invention discloses a 3D concrete printing path planning method using complex surface layering, comprising the following steps:

[0041] S1. Generate a three-dimensional model of a concrete component and determine whether the three-dimensional model meets a preset surface stratification standard. The three-dimensional model of the concrete component is established by computer-aided design software. After the establishment, determine whether the digital model is suitable for the method of the present invention according to the following surface stratification standard: (1) the top edge curve of the model is not on a three-dimensional space plane or a regular surface; (2) the bottom curve of the model is on a three-dimensional space plane. If the above two standards are met, the three-dimensional model information can be further extracted.

[0042] S2. Under the condition of satisfying the preset surface layering standard, extract the top edge curve of the three-dimensional model and convert it into a Nurbs curve (non-uniform rational B-spline curve).

[0043] S3. Convert the Nurbs curve into a Nurbs surface with UV direction.

[0044] In this step, in a visual programming language, the Nurbs curve obtained by S3 is used to generate a Nurbs surface with UV direction. The purpose of this step is to describe and locate the top edge curve of the three-dimensional model through the UV coordinates of the Nurbs surface, which is impossible to achieve with spatial planes and regular surfaces.

[0045] S4. Determine a slice reference plane, and project the Nurbs surface onto the slice reference plane to form a spatial surface whose array has the same UV coordinate composition logic but different spatial forms.

[0046] This step determines the main slicing reference planes according to the geometric shape of the component. These planes need to be consistent with the morphological change trend of the 3D model and can divide a complex 3D model into multiple groups of simple and easy-to-divide parts. This is to ensure that each slice generated in the surface layering step is reasonable, that is, no invalid or redundant slicing will be generated. After the slicing reference planes are determined, the Nurbs surfaces are projected onto these reference planes to form an array of spatial surfaces with the same UV coordinate composition logic but different spatial forms. In other words, these surfaces present a plane shape after projection, but still maintain the UV characteristics of the original surface, so the UV features can be used as a bridge to perform gradient calculations on the surface on the plane and the complex surface on the top of the model to achieve the association between the plane and the surface.

[0047] S5. Calculate the number of printing layers n between two adjacent slice reference planes according to the maximum height difference between two adjacent slice reference planes within the model range and the target height of each layer of the printing path. The calculation formula for the number of printing layers n between two adjacent slice reference planes is:

[0048] n=int((H max -H min) / h

[0049] Where n is the number of printing layers between two adjacent slice reference planes after slicing; H max H is the maximum height of two adjacent slice reference planes within the model range; min is the minimum height of two adjacent slice reference planes within the model range; h is the target height of each layer of the printing path, and the value range is 6mm-18mm. However, the value range will change depending on the size of the actual printed component and the different widths of each layer of concrete printed by different printing devices.

[0050] In this step, Grasshopper, a visual programming language based on the Rhino platform, can be used to calculate the net heights corresponding to the highest point and the lowest point in the top edge curve in the three-dimensional model.

[0051] S6. Perform surface gradient calculation on the formed array space surface, and generate a corresponding number of slice surfaces between each reference plane and the top Nurbs surface.

[0052] The surface gradient calculation can also be called the tween surface algorithm, which is based on the UV characteristics of two adjacent sets of spatial surfaces and is implemented through the Pufferfish plug-in in the visual programming language Grasshopper. Since S4 has ensured that the spatial surfaces between two adjacent slice reference planes have the same UV characteristics, in three-dimensional space, the corner points of each UV grid of the two sets of spatial surfaces can be matched one by one and connected to form an array corner point group. Then, in the Pufferfish plug-in, by entering the corresponding sequence, you can generate an equidistant array of corner points between each group of corner points (for example, if you want to generate 9 groups of spatial surfaces in two sets of adjacent slice reference planes, you can enter the sequence 0, 0.1, 0.2, ..., 0.9, 1, which means that on the line connecting every two corresponding corner points, one spatial point is determined at the position of unit 0, unit 0.1, unit 0.2, ... unit 0.9, unit 1, where the points corresponding to unit 0 and unit 1 are the UV grid points on the two reference surfaces), and the UV surface generated by these corner points is the gradient surface to be generated.

[0053] Specifically in the present invention, the number series required to be input is related to n. That is to say, to divide two adjacent slice reference planes in a model into n layers, it is necessary to evenly divide the interval [0,1] into n segments, generate the number series 0, 1 / n, 2 / n, ..., (n-1) / n, 1, and then input this set of number series and the corresponding two slice reference planes into the tween curve algorithm, so that (n-1) groups of gradient surfaces can be generated in the two slice reference planes, and then the model is segmented through the following steps.

[0054] In this step, in the visual programming language, the spatial surfaces generated in S4 are combined to perform surface gradient calculations. Taking the model with a slice reference plane as an example, the number of printing layers n calculated in S5 is used as the target number of surface gradients to generate n slice surfaces for segmenting the component 3D model. Thanks to the calculation in S5, the height difference between these slices will meet the height requirements of each layer path of 3D printing, ensuring that the material will not accumulate due to the small height difference between the upper and lower layer paths, or the height difference will not cause insufficient material supply.

[0055] The height difference is the difference between the maximum height and the minimum height of each two adjacent gradient surfaces within the model range after the gradient surface is generated. Since the gradient surface is generated by the average series method described above, this difference is actually approximately equal to the height difference between two adjacent slice reference planes divided by n.

[0056] S7, using the slicing surface to slice the three-dimensional model to generate a gradient curve printing path. In this step, the slicing surface obtained in S6 is used to slice the three-dimensional model by Boolean operation to generate n gradient curve printing paths.

[0057] Through the above S1-S7, each layer of concrete printing material in the 3D printing process can be smoothly superimposed, and the layer height fluctuation of each layer of the gradient curve printing path is as small as possible, or changes evenly. It is suitable for 3D printed concrete components with obvious top undulations that cannot be sliced ​​using a single plane or regular surface.

[0058] More advantageously, in one embodiment, the method further comprises:

[0059] S8. offset each gradient curve printing path by a certain distance into the three-dimensional model according to a preset printing width.

[0060] For example, according to the printing width b required for 3D printed concrete components (the applicable value range is 30mm-60mm depending on the size and shape of the component), each gradient curve is offset into the body, and the offset distance is b / 2. The reference surface of the offset is the slice surface corresponding to each curve. This step will generate a reference curve inside the 3D model that can be used to locate the coordinates of the robot arm. The offset calculation with a distance of b / 2 ensures that the 3D printed material can reach the actual boundary of the target shape after extrusion, flow, and solidification.

[0061] More beneficial, including:

[0062] S9. Use the equidistant breakpoint method to divide each gradient curve into continuous positioning points.

[0063] The purpose of this step is to ensure that the distance and speed of the robot arm remain constant when moving between points.

[0064] S10, using the normal direction corresponding to the positioning point in the gradient curve as the Z direction and the U coordinate direction as the X direction, generating the three-dimensional rectangular coordinates of each positioning point as the initial coordinate position of the robot arm at each positioning point.

[0065] Each rectangular coordinate generated in this step is tangent to the corresponding surface slice. In other words, positioning the robotic arm through this coordinate will ensure that the robotic arm always moves in the tangent direction of the surface slice during movement. This can make the texture effect printed by the robotic arm consistent with the shape of the three-dimensional model.

[0066] After the above S1-S10, it also includes:

[0067] S11. In a visual programming language, according to the printing environment and the robot model, the initial coordinate position of each positioning point is adjusted to meet the space limitation of the robot operation, and then the G-code for 3D printing is generated in combination with the operation parameters of the robot.

[0068] Through the above steps, the present invention expands the types of morphologies that can be achieved by 3D printing concrete technology through the gradual change and layering between irregular curved surfaces and planes, and the method of generating a robotic arm positioning coordinate system with the help of complex gradual curved surfaces, and improves the accuracy and stability of the complex concrete morphology printing process.

[0069] The present invention will be further described below in conjunction with specific embodiments.

[0070] Embodiment 1: Gradual layering of a complex curved surface and a reference plane.

[0071] like Figure 2 As shown, this embodiment is a concrete flower pot with an irregular curve on the top. Its characteristic is that, except for the irregular curve on the top edge, the model has no significant changes on the plane, and the model structure is relatively simple, so the path generation can be achieved only by gradient through a complex curved surface and a reference plane. In other words, only the bottom plane of the model needs to be used as the reference plane, and the remaining steps can be implemented according to the above method. After the curved surface layer is processed, the printing path can present a wavy texture on the surface of the flower pot. This embodiment is also applicable to other three-dimensional models with less plane changes and no need for additional support structures. Figure 2 In the figure, 1 indicates generating a Nurbs surface according to a Nurbs curve, 2 indicates projecting the Nurbs surface onto the bottom plane of the three-dimensional model, 3 indicates generating a gradient space surface, and 4 indicates the geometric shape after slicing.

[0072] Example 2: Gradual layering of complex curved surfaces and multiple reference planes

[0073] like Figure 3 As shown, this embodiment is a concrete sculpture with an irregular curved surface on the top and a bowl structure inside the structure, which requires additional support, wherein: Figure 3 --1 is the overall shape of the concrete sculpture. Figure 3-2 This is the cross-section of the concrete sculpture, with a bowl-shaped structure wrapped inside. Because of its complex structure, multiple reference planes are needed to divide the model so that each reference plane can match the changing trend of the model shape. That is to say, in addition to the bottom plane of the model, it is also necessary to construct a reference plane tangent to the bottom surface of the bowl structure, and a reference plane that is similar to the direction of the top opening of the sculpture as a transition, so that the gradual layering between the top curved surface and the plane can be performed. Therefore, in this embodiment, a total of three different reference planes are included, and the remaining steps can be implemented according to the process described above. This embodiment is also applicable to other three-dimensional models with rich plane changes or that require additional supporting structures. Figure 4 As shown, 1 represents generating a Nurbs surface according to a Nurbs curve, 2 represents determining a slice reference plane of a geometric shape, 3 represents projecting the Nurbs surface onto each slice reference plane of a three-dimensional model, 4 represents generating a gradient space surface, and 4 represents a sliced ​​geometric shape.

[0074] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0075] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A 3D concrete printing path planning method using complex surface layering, characterized in that: include: Generate a three-dimensional model of the concrete component, and determine whether the three-dimensional model meets a preset surface stratification standard; the preset surface stratification standard is: the top edge curve of the three-dimensional model is not on a three-dimensional space plane or a regular surface, and the bottom curve of the three-dimensional model is on a three-dimensional space plane; Under the condition of meeting the preset surface layering standard, the top edge curve of the 3D model is extracted and converted into a Nurbs curve; Convert Nurbs curves into Nurbs surfaces with UV directions; Determine the slice reference plane and project the Nurbs surface onto the slice reference plane to form a spatial surface with the same UV coordinate composition logic but different spatial forms; Calculate the number of printing layers between two adjacent slice reference planes according to the maximum height difference between two adjacent slice reference planes within the model range and the target height of each layer printing path; The calculation formula for the number of printing layers between two adjacent slice reference planes is: n=int((H max -H min ) / h Where n is the number of printing layers between two adjacent slice reference planes after slicing; H max H is the maximum height of two adjacent slice reference planes within the model range; min is the minimum height of two adjacent slice reference planes within the model range; h is the target height of each layer of printing path, ranging from 6mm to 18mm; Perform surface gradient calculation on the formed array space surface, and generate a corresponding number of slice surfaces between each reference plane and the top Nurbs surface; Use the slicing surface to slice the 3D model and generate a gradient curve printing path.

2. A 3D concrete printing path planning method using complex surface layering according to claim 1, characterized in that: Also includes: Each gradient curve printing path is offset by a certain distance into the 3D model according to the preset printing width.

3. The 3D concrete printing path planning method using complex surface layering according to claim 2 is characterized in that: The offset distance is 1 / 2 of the preset print width.

4. The 3D concrete printing path planning method using complex surface layering according to claim 2 is characterized in that: Also includes: Each gradient curve is divided into continuous positioning points using the method of equidistant breakpoints; The normal direction corresponding to the positioning point in the gradient curve is used as the Z direction, and the U coordinate direction is used as the X direction to generate the three-dimensional rectangular coordinates of each positioning point as the initial coordinate position of the robot arm at each positioning point.

5. The 3D concrete printing path planning method using complex surface layering according to claim 4 is characterized in that: Also includes: Adjust the initial coordinate position of each positioning point according to the printing environment and robot arm model.

6. The 3D concrete printing path planning method using complex surface layering according to claim 1 is characterized in that: The reference plane of each slice is determined according to the morphological change trend of the three-dimensional model.

7. The 3D concrete printing path planning method using complex surface layering according to claim 1 is characterized in that: The layer height of each layer of the gradient curve printing path changes evenly.

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