An equidistant segment line printing path planning method for curved surface coverings based on FDM printing

Abstract

The present invention relates to the technical field of geometric path production of 3D printing, and specifically discloses an equidistant segment line printing path planning method for curved surface coverings based on FDM printing, comprising the following steps: surface pretreatment: acquisition of geometric surface of covering, property recognition and surface inspection; preparation of substrate: determination of substrate type used for geometric surface of covering and its preparation; reference reference selection: subroutine method for determining reference reference for path planning; surface generation curve: geometric operation to generate initial path segment line; segment line connection: conversion of multiple initial path segment lines into a continuous curve; path inspection and optimization: inspection of path rationality, optimization of path details; printing program generation: production of self-compiled G‑Code file and parameterization of printing data. The present invention adopts the above-mentioned equidistant segment line printing path planning method for curved surface coverings based on FDM printing, which has the advantages of fast speed, reasonable tool path, low cost, automatic adjustment of machine parameters and high quality during additive manufacturing.

Description

Technical Field

[0001] The present invention relates to the technical field of geometric path production of 3D printing, and in particular to an equidistant segment line printing path planning method for a curved surface covering based on FDM printing. Background Art

[0002] FDM printing is the most common and widely used technology in 3D printing. It melts the thermoplastic material by heating the nozzle, deposits the material layer by layer or along a specific path according to the path and extrusion amount controlled by the computer file, and finally forms a 3D printed object.

[0003] In the prior art, printing of curved surface coverings in existing 3D printer slicing software programs can only be achieved by adding support parts, adjusting the model placement to a printable state, or adjusting the model's suspended area to a gradually cantilevered surface. The former will use a large amount of support, resulting in a large amount of material waste, defects on the printed surface, a long manufacturing time, and a greatly increased probability of printing failure due to the continuous retraction of the extruder end and printing across the model. The latter, when the suspended area is large or the cantilever angle is large, the shape of the original model is greatly changed, and it cannot meet the original needs and specific shapes.

[0004] In addition, when encountering geometric surfaces of the covering type, the original contour-based layer-by-layer printing method cannot effectively cope with the printing of surfaces with small curvatures or even flat top covers, resulting in the inability of materials to accumulate layer by layer or poor adhesion between layers during the printing process, which in turn leads to a rough surface.

[0005] Therefore, in order to adapt to various covering surfaces, improve printing quality and reduce the probability of material loss, defects and failure, it is necessary to develop a planning method for equidistant segment line printing paths and a program for geometric operations for FDM printed curved surface coverings. Summary of the invention

[0006] The purpose of the present invention is to provide an equidistant segment line printing path planning method for curved surface coverings based on FDM printing, which has the advantages of fast speed, reasonable tool path, low cost, automatic adjustment of machine parameters and high quality during additive manufacturing.

[0007] To achieve the above object, the present invention provides an equidistant segment line printing path planning method for a curved surface covering based on FDM printing, comprising the following steps:

[0008] S1. Surface preprocessing: acquisition of geometric surface of covering, attribute recognition and surface inspection;

[0009] S2. Prepare the substrate: determine the type of substrate used for the geometric surface of the covering and its preparation;

[0010] S3, datum reference selection: a subroutine method for determining a datum reference for path planning;

[0011] S4, surface generation curve: geometric operation generates initial path segment line;

[0012] S5, segment line connection: convert multiple initial path segment lines into a continuous curve;

[0013] S6, Path inspection and optimization: inspect the rationality of the path and optimize the path details;

[0014] S7, Printing program generation: creation of self-edited G-Code files and parameterization of printing data.

[0015] Preferably, S1 is specifically:

[0016] S11, obtaining the geometric surface of the covering;

[0017] S12, determining whether it is necessary to perform a three-dimensional scan on the surface of the existing component serving as the base; if necessary, using a three-dimensional scanner to scan the surface of the component to be covered to obtain a point cloud model, and processing the point cloud model into a three-dimensional model, and inputting the geometric surface of the covering into the algorithm end; if not necessary, directly inputting the geometric surface of the covering into the algorithm end;

[0018] S13, identifying whether the geometry type is Mesh or NURBS, if not, converting the geometry type to Mesh or NURBS based on the RhinoCommon principle of the RH-GH modeling software, and entering S14; if yes, directly entering S14;

[0019] S14. Check the integrity of the geometric surface, that is, whether there is any broken surface or defect. If so, quickly repair the surface by using the mesh point mapping surface repair method for Mesh and the embedding surface repair method by extracting the characteristic points and lines on NURBS to obtain the geometric surface of the covering object for calculation. If not, directly obtain the geometric surface of the covering object for calculation.

[0020] Preferably, S2 is specifically:

[0021] Determine whether to use the scanned component as the printing base. If not, set a base height value H and then raise the geometric surface of the covering object to a height of H, extract the outer contour of the raised geometric surface of the covering object, and project the outer contour onto the base plane. Then input the maximum layer height value h that the printer can extrude, and generate [N=Ceiling(H / h)] transition lines between the raised outer contour and the projection line of its base plane. Arrange the N transition lines, the contour line of the geometric surface of the covering object at the raised height, and its projection contour line on the base plane in order from bottom to top according to the spatial position. If yes, place the scanned component on the base platform of the printer, and use the machine position calibration function to determine the spatial position P0[X0,Y0,Z0] of the scanned component in the machine coordinate system.

[0022] Preferably, S3 is specifically:

[0023] S31, determining whether the target equidistant segment line path is equidistant along the geometric surface of the covering object rather than equidistant on the two-dimensional plane, if not, using subroutine method S3-3; if yes, proceeding to S32;

[0024] S32, judging whether the extrusion on the target printing path is continuous, if not, adopting the subroutine method S3-1; if continuous, adopting the subroutine method S3-2.

[0025] Preferably, in S32, the subroutine method S3-1 is specifically a subroutine method using the geometric center and the adjacent points as the reference, comprising the following steps:

[0026] S3-11, a method for generating equidistant segment lines along the surface based on geodesic distances using grid points of covering objects;

[0027] S3-12, extract all mesh vertices of the surface, and use the average method to calculate the coordinate values ​​of all mesh vertices to obtain the surface geometric center C1;

[0028] S3-13, get the UV value interval (u0,u1), (v0,v1) of the surface;

[0029] S3-14. Taking the surface geometric center C1 as the origin, set N1 reference points in the U direction and [Ceiling (N1*(u1 / v1))] reference points in the V direction;

[0030] S3-15, determine the ratio of the number of points in each direction orthogonal to the surface geometric center C1 as the origin;

[0031] S3-16, take the surface geometric center C1 and its surrounding reference points as the reference;

[0032] The subroutine method S3-2 specifically uses any contour edge extension line as a reference, and includes the following steps:

[0033] S3-21, a method of using a circular tube of equal radius to cyclically intersect the geometric surface of the covering to produce segment lines equidistant along the surface; taking any contour boundary of the geometric surface of the covering and obtaining the length L2 of the boundary;

[0034] S3-22, extend the two ends of the selected contour boundary by 0.1*L2 with G2 curvature;

[0035] S3-23. Use the curve after extending the boundary as the reference.

[0036] Preferably, in S31, the subroutine method S3-3 specifically adopts the section plane for determining the angle with the geometric plane as a reference, and includes the following steps:

[0037] S3-31, a method for producing equidistant lines of a two-dimensional plane by intersecting an equidistant cutting plane with a geometric surface of a covering;

[0038] S3-32, extract the coordinate values ​​of each corner point on the outer contour of the geometric surface of the covering (X i ,Y i ,Z i );

[0039] S3-33, compare the XY coordinates of each corner point and take the smallest point as the geometric origin and use any adjacent edge as the reference boundary;

[0040] S3-34, determining the XY plane projection angle α between the target path and the starting boundary;

[0041] S3-35. According to the angle α, a section plane is set at the origin, which is parallel to the direction of the target path and is orthogonal to the XY plane;

[0042] S3-36. Use the set section plane as the reference.

[0043] Preferably, S4 is specifically:

[0044] S4-1, obtaining multiple groups of initial equidistant segment lines, including the following steps:

[0045] S4-11, obtaining the reference surface geometric center C1 and several directly adjacent surrounding mesh vertices;

[0046] S4-12, merging and averaging the repeated mesh vertices at all positions on the geometric surface of the covering so that the points at the positions of the mesh vertices are unique;

[0047] S4-13, calculating the distance and vector from all mesh vertices to the surface geometric center C1, and setting the printer line width W1 according to the printer configuration;

[0048] S4-14, setting the maximum number of operation points P for each equidistant point, and obtaining a number of offset directions based on the mesh vertices adjacent to the surface geometric center C1;

[0049] S4-15, offsetting a number of equidistant points based on the vector calculated from the group of points;

[0050] S4-16, determine whether the number of the same group of equidistant points on the surface is greater than or equal to 2. If so, remove the mesh vertices and surface geometric center C1 that have participated in the calculation, and calculate the distance D between the remaining C1 on the surface and the group of equidistant points i and vector V i , repeat S4-15 above until the number of the same group of equidistant points on the surface is less than 2;

[0051] S4-17, obtaining a plurality of groups of equidistant points based on surface geodesic distances;

[0052] S4-18, connect several equidistant points of the same group of polylines;

[0053] S5 is as follows:

[0054] S5-1. Process multiple groups of equidistant segment lines into a continuous curve and set extrusion properties for each part, including the following steps:

[0055] S5-11, obtaining a plurality of groups of curves with equidistant offsets based on the surface geodesic distance, and setting extrusion attributes T and F, where T represents extrusion and F represents no extrusion;

[0056] S5-12, connect multiple curves in the same group;

[0057] S5-13, judging whether a closed curve is obtained, if not, blending multiple segments of non-connected curves in several circle groups, then setting T attribute to the non-connected curve parts, setting F attribute to the blended curve parts, and combining them into a closed curve; if yes, setting T attribute to the curve;

[0058] S5-14, sort by distance from the surface geometric center C1 from far to near;

[0059] S5-15, set a number of equidistant points on the multi-circle closed curve according to the length and accuracy;

[0060] S5-16, transfer rank to multiple groups of equidistant points;

[0061] S5-17, set a matrix sequence relationship, set the Nth data of each group and the N+1th data of the sub-group to be the same array, and so on, and reverse the rank according to the set sequence relationship of the equidistant point groups;

[0062] S5-18, flatten into a one-dimensional array according to the order within the matrix;

[0063] S5-19. Connect all the points in the one-dimensional array in order to form a continuous curve.

[0064] Preferably, S4 is specifically:

[0065] S4-2, obtaining multiple initial surface equal radius circular tube intersection lines, including the following steps:

[0066] S4-21, obtain the extended boundary line of the benchmark reference;

[0067] S4-22, comparing the lengths of two adjacent sides of the extended boundary line, and taking the length E2 of the longer side;

[0068] S4-23, set the print line width W2 according to the printer configuration, and calculate the number of loop operations N2=E2 / W2;

[0069] S4-24, making a circular tube with the extended boundary line as the center line and the line width W2 as the diameter;

[0070] S4-25, cut the surface to get the intersection line;

[0071] S4-26, judging whether the number of intersection lines is less than N2, if so, making a circular tube with the intersection line as the center line and the line width W2 as the diameter, repeating the above step S4-25 to generate new intersection lines until the number of intersection lines reaches N2;

[0072] S4-27, the starting boundary line and the intersection line are arranged sequentially on the geometric surface of the covering;

[0073] S5 is as follows:

[0074] S5-2, processing multiple surface equidistant circular tube intersection lines and connecting them into a curve, including the following steps:

[0075] S5-21, obtaining equidistant curves on the geometric surface of the sequentially arranged covering;

[0076] S5-22, obtain all endpoints of all equidistant curves;

[0077] S5-23, connect corresponding endpoints along the geometric surface of the covering in end-to-end order using the geodesic method;

[0078] S5-24. Combine all curves on the geometric surface of the covering into a continuous curve.

[0079] Preferably, S4 is specifically:

[0080] S4-3, obtaining multiple initial surface equidistant cutting plane intersection lines, including the following steps:

[0081] S4-31, obtaining a section plane of a datum reference;

[0082] S4-32, use the Bounding Box method to find the smallest cube that can enclose the geometric surface of the covering;

[0083] S4-33, connect all the spatial diagonals of the cube and compare their lengths, and take the longest diagonal E3;

[0084] S4-34, set the print line width W3 according to the printer configuration, and calculate the number of arrays N3=E3 / W3;

[0085] S4-35. Cut the covering geometric surface along the section planes of the normal vector array N3 and intersect with the covering geometric surface to obtain a plurality of intersection lines.

[0086] S5 is as follows:

[0087] S5-3, processing multiple surface equidistant cutting plane intersection lines and connecting them into a curve, including the following steps:

[0088] S5-31, obtaining intersection lines between the sequentially arranged equidistant cutting planes and the geometric surface of the covering;

[0089] S5-32, obtain all intersection endpoints;

[0090] S5-33. Get the length parameter λ of all endpoints on the boundary of the covering geometric surface i ;

[0091] S5-34, the boundaries of the covering geometric surface are broken at several length parameters;

[0092] S5-35, setting the starting moving direction V3 of the printing path, and removing the separated boundary intervals according to the path direction;

[0093] S5-36. Connect all intersecting lines and the processed boundaries into a continuous curve.

[0094] Preferably, S6 is specifically:

[0095] S61, obtaining the continuous curve on the geometric surface of the covering and analyzing the curvature change;

[0096] S62, select the curvature continuity standard between G0 and G3;

[0097] S63, extracting Gn discontinuity points on the geometric surface of the covering according to the set curve discontinuity;

[0098] S64, analyzing the parameter positions of several discontinuous points on the continuous curve;

[0099] S65. Creating a sphere of relative radius at corresponding points according to the parameter positions of the plurality of points;

[0100] S66, intersecting a number of spheres with the continuous curve, and obtaining the Boolean difference of the curve on the number of spheres;

[0101] S67, setting a relative fitting convex value B, and blending the beginning and the end of the disconnected curve by relative arc fitting;

[0102] S68, mapping the blended portion of the curve onto the geometric surface of the covering;

[0103] S69, combining the disconnected curve and the arc fitting mixed curve into a continuous path curve;

[0104] S7 is specifically:

[0105] S71, converting the path curve into a number of equidistant points according to printing accuracy requirements;

[0106] S72, calculating the UV point values ​​of all equidistant points on the geometric surface;

[0107] S73, calculating the relative extrusion value of each point according to the set printing line width and the statistical UV value of the equidistant points;

[0108] S74, setting machine parameters of the printer, including adjusting the extrusion ratio, adjusting the printing speed and adjusting the hot end temperature;

[0109] S75, translating the machine parameters into the parameters of the geometric path to generate a G-Code file, and performing a simulation of the movement of the machine along the surface path curve and the extrusion control in the 3D visualization software RH-GH;

[0110] S76, determining whether the path simulation generates collisions or gaps, and if so, readjusting the machine parameters until there are no collisions or gaps, and then executing the printing file.

[0111] Therefore, the present invention adopts the above-mentioned equidistant segment line printing path planning method for curved surface coverings based on FDM printing, and the beneficial effects are as follows:

[0112] The present invention is based on Rhinoceros-Grasshopper three-dimensional visual parametric modeling software, which can identify various covering surfaces, select relatively adaptive and efficient surface path planning subroutines for them according to their geometric properties and target production methods, and perform parametric geometric calculation operations at the same time, and finally generate a path that can be continuously extruded to achieve efficient, high-surface-quality, unsupported suspended surface manufacturing, effectively reduce material loss, defect generation and the probability of printing failure, and reduce the production difficulty, time and economic cost in a simple printing form through parametric automatic control of machine parameters and extrusion paths.

[0113] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0114] Figure 1 It is a general flow chart of the first embodiment of the method for planning the equidistant segment line printing path of the curved surface covering based on FDM printing of the present invention;

[0115] Figure 2 It is a flow chart of surface preprocessing of Example 1 of the equidistant segment line printing path planning method for a curved surface covering based on FDM printing of the present invention;

[0116] Figure 3 It is a flow chart of preparing a substrate in Embodiment 1 of the method for planning an equidistant segment line printing path for a curved surface covering based on FDM printing of the present invention;

[0117] Figure 4 It is a flowchart of the reference selection of the embodiment 1 of the method for planning the printing path of the curved surface covering of the equidistant segment line type based on FDM printing of the present invention;

[0118] Figure 5 It is a flowchart of S4-1 of Embodiment 1 of the method for planning an equidistant segment line printing path for a curved surface covering based on FDM printing of the present invention;

[0119] Figure 6 It is a flowchart of S4-2 of Embodiment 1 of the method for planning an equidistant segment line printing path for a curved surface covering based on FDM printing of the present invention;

[0120] Figure 7 It is a flowchart of S4-3 of Embodiment 1 of the method for planning an equidistant segment line printing path for a curved surface covering based on FDM printing of the present invention;

[0121] Figure 8 It is a flow chart of segment line connection of Example 1 of the equidistant segment line printing path planning method for a curved surface covering based on FDM printing of the present invention;

[0122] Fig. 9It is a flow chart of path verification and optimization of the first embodiment of the equidistant segment line printing path planning method for curved surface coverings based on FDM printing of the present invention;

[0123] Fig.10 It is a flow chart generated by a printing program according to Embodiment 1 of the method for planning an equidistant segment line printing path for a curved surface covering based on FDM printing of the present invention;

[0124] Fig.11 It is a schematic diagram of a mechanical arm printing device equipped with an FDM printing gun according to Embodiment 1 of the method for planning an equidistant segment line printing path for a curved surface covering based on FDM printing of the present invention;

[0125] Fig.12 It is a schematic diagram of an initial path curve of a three-dimensional equidistant segment line type along the surface of a covering object generated in step S4-2 of Embodiment 1 of the method for planning an equidistant segment line type printing path for a curved surface covering object based on FDM printing of the present invention;

[0126] Fig.13 It is a schematic diagram of extrusion simulation inspection of a continuous printing path of three-dimensional equidistant segment lines along the surface of a covering object generated in step S5-2 of Embodiment 1 of the method for planning an equidistant segment line printing path for a curved surface covering object based on FDM printing of the present invention;

[0127] Fig.14 1 is a schematic diagram of the printing process of the first embodiment of the method for planning the printing path of an equidistant segment line type curved surface covering based on FDM printing of the present invention, wherein (a) shows a prefabricated and installed grid support as a base for printing a covering, (b) shows the process of printing and making the curved surface covering, and (c) shows the effect of the curved surface covering after printing;

[0128] Fig.15 Schematic diagram of a grid base according to Embodiment 1 of the method for planning an equidistant segment line printing path for a curved surface covering based on FDM printing of the present invention, wherein (a) represents a curved grid shell support base, and (b) represents a flat top cover support base;

[0129] Fig.16 It is a schematic diagram of the grid base of Example 2 of the equidistant segment line printing path planning method for curved surface coverings based on FDM printing of the present invention, wherein (a) represents the path generated after planning, and (b) represents the process of printing and manufacturing flat-top surface coverings. DETAILED DESCRIPTION

[0130] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0131] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0132] It should be stated in advance that the common geometric attributes of general 3D modeling software on the market mainly include: boundary representation geometry Boundary-Representation (hereinafter referred to as B-rep), non-uniform rational B-spline curves and surfaces Non-Uniform Rational B-Splines (hereinafter referred to as NURBS), mesh surface Mesh, subdivision surface Sub-division (hereinafter referred to as Sub-D), poly-surface Poly-Surface, etc. This method also mainly identifies and judges the above types of geometric attributes in Rhinoceros-Grasshopper (hereinafter referred to as RH-GH) software. If there are geometric attributes not mentioned, the geometry needs to be converted into geometric attributes that can be recognized by general 3D software on the market in advance. This program invention is based on the underlying principle of RhinoCommon, so only Mesh surfaces or NURBS (Non-Uniform Rational B-Splines) surfaces are considered in RH-GH parametric modeling software.

[0133] Embodiment 1

[0134] In this embodiment, a free polygonal curved top cover with no fixed shape will be produced by path planning and unsupported suspended surface printing on a pre-prepared grid base. First, the source of the geometric surface of the covering can be artificial computer modeling, models downloaded from other channels, three-dimensional point cloud scanning models, etc. The geometric surface of the covering is then picked up and input into the parametric operation platform of the three-dimensional software Rhinoceros-Grasshopper, and its geometric properties are judged to be NURBS surfaces, and its surface is checked for damage. If so, the geometric surface is repaired by point-line embedding according to the common operations of the three-dimensional software. Then, the path type sub-method is selected according to the target requirements and the production machine used. The path type sub-method of this embodiment pre-uses a robotic arm equipped with a print gun head to perform unsupported suspended printing on the curved surface on the grid base. Fig.15 As shown, the grid base can adopt a curved grid shell type support base or a flat top cover support base.

[0135] like Figure 1 As shown, the equidistant segment line printing path planning method for a curved surface covering based on FDM printing includes the following steps:

[0136] S1. Surface preprocessing, i.e., firstly, the attribute recognition, surface integrity check and processing of the geometric surface of the covering are performed to obtain the geometric surface of the covering for calculation. The specific steps are as follows: Figure 2 As shown: S11: Obtain the covering geometric surface.

[0137] S12: Determine whether it is necessary to perform a three-dimensional scan on the surface of the existing component as the base. If necessary, use a three-dimensional scanner to scan the surface of the component to be covered to obtain a point cloud model, and process the point cloud model into a three-dimensional model, and input the geometric surface of the covering at the algorithm end. If not necessary, directly input the geometric surface of the covering at the algorithm end. In this embodiment, a three-dimensional scanner is used to scan the curved grid support as the printing base of the covering, and the obtained point cloud model is processed into a geometric surface of the covering with a geometry type of Mesh.

[0138] S13: Identify whether the geometry type is Mesh or NURBS. If not, convert the geometry type to Mesh or NURBS based on the RhinoCommon principle of the RH-GH modeling software, and then check the integrity of the geometry surface. If yes, check the integrity of the geometry surface. In this embodiment, the geometry type of the geometric surface of the cover is Mesh.

[0139] S14: Check the integrity of the geometric surface, whether the geometric surface of the covering is broken or incomplete, etc. If so, it is necessary to quickly repair the surface to make it a whole intact surface. The mesh point mapping surface repair method is used for Mesh, and the embedded surface repair method is used for NURBS to extract the characteristic points and lines on it to obtain the geometric surface of the covering for calculation. If not, the geometric surface of the covering for calculation is directly obtained. In this embodiment, the covering surface is checked for broken and incomplete surfaces, and the mesh point mapping surface repair method is used to subsequently become a complete geometric surface of the covering.

[0140] S2, prepare the substrate, that is, determine the type of substrate used for the geometric surface of the covering and its corresponding pre-preparation method. The specific steps are as follows Figure 3 As shown: S21: Get the intact geometric surface of the covering after repair by S1. S22: Determine whether to use the scanned component as the printing base. If not, set a base height value H and then raise the geometric surface of the covering by H. Extract the outer contour of the raised geometric surface of the covering and project the outer contour onto the base plane. Then input the maximum layer height value h that the printer can extrude, generate [N=Ceiling(H / h)] transition lines between the raised outer contour and the projection line of its base plane, and arrange the N transition lines, the contour line of the geometric surface of the covering with the raised height, and its projection contour line on the base plane in order from bottom to top according to the spatial position. If so, place the scanned component on the base platform within the effective working range of the printer, and use the machine position calibration function to determine the spatial position P0[X0,Y0,Z0] of the component in the machine coordinate system.

[0141] In this embodiment, the scanning component is used as the substrate, and the scanning component is placed on the substrate platform within the effective working range of the printer. The machine position calibration function is used to determine the spatial position P0[X0, Y0, Z0] of the component in the machine coordinate system. In this embodiment, the spatial position of the substrate in the printer working coordinate system is P0[30.684, 50.192, 0.031].

[0142] S3, the reference is selected, that is, the reference subroutine method for path planning is determined. The specific subroutine method is as follows: Figure 4 As shown: S31: Determine whether the target equidistant segment line path is equidistant along the geometric surface of the covering, rather than equidistant on the two-dimensional plane. If not, use subroutine method S3-3. If yes, proceed to step S32. S32: Determine whether the extrusion on the target printing path is continuous. If not, use subroutine method S3-1. If continuous, use subroutine method S3-2.

[0143] Subroutine method S3-1: Use the geometric center and adjacent points as reference.

[0144] Specifically, S3-11: a method for generating equidistant segment lines along the surface based on geodesic distances of covering grid points.

[0145] S3-12: Extract all mesh vertices of the surface and use the average method to calculate the surface geometric center C1 by taking the coordinate values ​​of all mesh points.

[0146] S3-13: Obtain the UV value interval (u0, u1), (v0, v1) of the surface. If the subroutine method S3-1 is used, the UV value interval of the surface of the covering in this embodiment is (0.058, 0.978), (0.064, 0.875).

[0147] S3-14: With the surface geometric center C1 as the origin, set N1 reference points in the U direction and Ceiling (N1*(u1 / v1)) reference points in the V direction. If the subroutine method S3-1 of this embodiment is used, 3 reference points in the U direction are set on the geometric surface of the covering, and 4 reference points in the V direction are rounded up.

[0148] S3-15: Determine the ratio of the number of points in each direction orthogonal to the center of the surface as the origin. If the ratio of the number of points in the embodiment of the subroutine method S3-1 is set according to S3-14, it is 0.75.

[0149] S3-16: Use the surface geometric center C1 and its surrounding reference points as reference. Then proceed to step S4-1. The specific steps are as follows: Figure 5 shown.

[0150] Subroutine method S3-2: Take any contour edge extension line as a reference. Specifically, S3-21: Use a method of cyclically intersecting a circular tube with a geometric surface of a covering object to produce equidistant segment lines along the surface, take any contour boundary of the geometric surface of the covering object and obtain the length L2 of the boundary. The contour edge length taken in this embodiment is 120.67.

[0151] S3-22: Extend both ends of the selected contour boundary by 0.1*L2 with G2 curvature.

[0152] S3-23: Use the curve after extending the boundary as the reference. Then enter step S4-2. The specific steps are as follows: Figure 6 shown.

[0153] Subroutine method S3-3: using a section plane that determines an angle with a geometric plane as a reference object. Specifically, S3-31: using an equidistant section plane to intersect with a geometric surface of a covering object to produce an equidistant line of a two-dimensional plane.

[0154] S3-32: Extract the coordinate values ​​of each corner point on the outer contour of the geometric surface of the covering (X i ,Y i ,Z i ). For example, in this embodiment, the coordinate values ​​of each corner point are (0.00, 0.00, 6.00), (120.00, 0.00, 6.00), (0.00, 120.00, 6.00), and (120.00, 120.00, 6.00).

[0155] S3-33: After comparing the XY coordinates of each corner point, take the smallest point as the geometric origin and use any adjacent edge as the reference boundary. For example, in this embodiment, the most standard value of the minimum XY coordinate point is (0.00, 0.00, 6.00).

[0156] S3-34: Determine the XY plane projection angle α between the target path and the starting boundary. For example, in this embodiment, the XY plane projection angle α between the target path and the starting boundary is 45 degrees.

[0157] S3-35: According to the angle α, a section plane is set at the origin which is parallel to the direction of the target path and is orthogonal to the XY plane.

[0158] S3-36: Use the set cutting plane as the reference. Then proceed to step S4-3. The specific steps are as follows: Figure 7 shown.

[0159] In this embodiment, the target required path planning is an equidistant segment line path along the geometric surface of the covering, and the manufacturing process is continuous along the extrusion of the printing path, so the subroutine method S3-2 is adopted.

[0160] S4, surface generation curve, that is, the extension line of any contour edge selected as the reference by method S3-2 is used to generate an initial path segment line with three-dimensional equidistant distance along the surface on the geometric surface of the covering in method S4-2 through geometric operation.

[0161] Specifically, S4-21: obtain the extended boundary line of the benchmark reference. S4-22: compare the lengths of the two adjacent sides of the extended boundary line, and take the length E2 of the longer side. In this embodiment, the length of the longer side is 120.67. S4-23: set the print line width W2 according to the printer configuration, and calculate the number of loop operations N2=E2 / W2. In this embodiment, a nozzle with a caliber of 1.0 is used, so the relatively appropriate print line width W2 is set to 1.2mm. S4-24: make a circular tube body with the extended boundary line as the center line and the line width W2 as the diameter. S4-25: cut the surface to obtain the intersection line. S4-26: determine whether the number of intersection lines is less than N2. If so, make a circular tube body with the intersection line as the center line and the line width W2 as the diameter, and repeat the step of S4-15 to generate new intersection lines until the number of intersection lines reaches N2. S4-27: the starting boundary line and the intersection line are arranged sequentially on the geometric surface of the covering.

[0162] S5, segment line connection, that is, multiple initial path segment lines generated by S4-2 are connected in S5-2 to form a continuous curve. The specific steps of S5-2 are as follows: Figure 8 As shown:

[0163] S5-21: Get the equidistant curves arranged in order on the geometric surface of the covering. S5-22: Get all the endpoints of all the equidistant curves. S5-23: Connect the corresponding endpoints in the order of end to end along the geometric surface of the covering using the geodesic method. S5-24: Combine all the curves on the geometric surface of the covering into a continuous curve.

[0164] S6, path inspection and optimization, that is, inspecting the rationality of the path of a continuous curve obtained by method S5-2, and optimizing the path details to improve the printing quality. The steps are as follows: Fig. 9 As shown:

[0165] S61: Obtain the continuous curve on the geometric surface of the covering and analyze the curvature change. S62: Select the curvature continuity standard between G0 and G3. In this embodiment, the G0 curvature continuity standard is used. S63: Extract the Gn discontinuous points on the geometric surface of the covering according to the set curve discontinuity. In this embodiment, the G0 discontinuous points, that is, the broken line corner points at the position connection, are extracted. S64: Analyze the parameter positions of several discontinuous points on the continuous curve. S65: Create spheres of relative radius at corresponding points based on the parameter positions of several points. S66: Intersect several spheres with the continuous curve, and calculate the Boolean difference set of the curve to the several spheres. S67: Set the relative fitting bulge value B, and blend the head and tail of the disconnected curve with the relative arc fitting. In this embodiment, the bulge value B (Bulge) is 0.45. S68: Map the blended part of the curve to the geometric surface of the covering. S69: Combine the disconnected curve and the curve blended with the arc fitting into a continuous path curve.

[0166] S7, print program generation, that is, the production of self-edited G-Code files and parameterization of print data. The specific steps are as follows Fig.10 As shown:

[0167] S71: Convert the path curve into a number of equidistant points (such as one equidistant point every 0.5mm) according to the printing accuracy requirements. In this embodiment, equidistant points with an accuracy of 0.1mm are used. S72: Calculate the UV point values ​​of all equidistant points on the geometric surface. S73: Calculate the relative extrusion value of each point based on the set printing line width and the statistical UV value of the equidistant points. S74: Set the machine parameters of the printer, such as adjusting the extrusion ratio, adjusting the printing speed, and adjusting the hot end temperature. S75: Translate the machine parameters combined with the parameters produced by the geometric path to generate a G-Code file, and simulate the movement of the machine along the surface path curve and the extrusion control in the three-dimensional visualization software RH-GH. S76: Determine whether the path simulation produces collisions or gaps. If there are obvious collisions or gaps, readjust the machine parameters until there are no obvious collisions or gaps, and then the print file can be executed.

[0168] After the path planning and optimization method program of this embodiment is executed, the printing program file is then input into the mechanical arm equipped with the printing gun head. Fig.11 As shown, the machine is used to perform continuous path FDM printing along the surface of a pre-prepared curved grid base in a three-dimensional equidistant segment line manner. The path planning is as follows Fig.12 As shown, the simulation of printing and extrusion along the path is as follows Fig.13 The base installation of the execution process is as follows Fig.14 As shown in (a) in the figure, the printing process is as follows Fig.14 As shown in (b) in the figure, the final printing effect is as follows Fig.14 As shown in (c) in .

[0169] Embodiment 2

[0170] The path planning method of the first embodiment is used to print the planar top cover support, and after alignment and three-dimensional scanning, the path planning and printing of the planar top cover is printed on it using an equidistant segment line path based on geodesic distance, such as Fig.16 As shown in (a) of FIG. 1 , the path generated after planning is obtained, and then the process of printing and making the flat top surface covering is as follows: Fig.16 As shown in (b) in .

[0171] Therefore, the present invention adopts the above-mentioned equidistant segment line printing path planning method for curved surface coverings based on FDM printing. The development of the program method is based on Rhinoceros-Grasshopper, a three-dimensional visual parametric modeling software. The program can identify various flat-top or curved surface covering surfaces, select relatively suitable and efficient surface path planning subroutines for them according to their geometric properties and target production methods, and perform some parametric geometric operations at the same time. Finally, by independently writing G-Code, a reasonable printing path is pre-planned on the geometric surface of the covering, and a "one-stroke" continuous extrusion printing path is achieved as much as possible. At the same time, the machine parameters are optimized and parametrically controlled according to the accuracy requirements and surface types. This program is an innovative method, so that the files it finally generates can be manufactured quickly, efficiently and with high quality when dealing with various types of coverings, so as to improve the printing quality and reduce the probability of material loss, defects and failures. This program method provides a new way to reduce the difficulty, time and economic cost of printing the surface of the covering in a simple printing form.

[0172] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. An equidistant segment line printing path planning method for curved surface coverings based on FDM printing, characterized in that: The following steps are involved: S1. Surface preprocessing: acquisition of geometric surface of covering, attribute recognition and surface inspection; S2. Prepare the substrate: determine the type of substrate used for the geometric surface of the covering and its preparation; S3, datum reference selection: a subroutine method for determining a datum reference for path planning; S4, surface generation curve: geometric operation generates initial path segment line; S5, segment line connection: convert multiple initial path segment lines into a continuous curve; S6, Path inspection and optimization: inspect the rationality of the path and optimize the path details; S7, Printing program generation: production of self-edited G-Code files and parameterization of printing data; S3 is specifically: S31, determining whether the target equidistant segment line path is equidistant along the geometric surface of the covering object rather than equidistant on the two-dimensional plane, if not, using subroutine method S3-3; if yes, proceeding to S32; S32, determining whether the extrusion on the target printing path is continuous, if not, using subroutine method S3-1; if continuous, using subroutine method S3-2; In S32, the subroutine method S3-1 is specifically a subroutine method using the geometric center and the adjacent points as the reference, including the following steps: S3-11, a method for generating equidistant segment lines along the surface based on geodesic distances using grid points of covering objects; S3-12, extract all mesh vertices of the surface, and use the average method to calculate the coordinate values ​​of all mesh vertices to obtain the surface geometric center C1; S3-13, get the UV value interval (u0,u1), (v0,v1) of the surface; S3-14, take the surface geometric center C1 as the origin, set N1 reference points in the U direction and N1 reference points in the V direction indivual; S3-15, determine the ratio of the number of points in each direction orthogonal to the surface geometric center C1 as the origin; S3-16, take the surface geometric center C1 and its surrounding reference points as the reference; The subroutine method S3-2 specifically uses any contour edge extension line as a reference, and includes the following steps: S3-21, using a method of cyclically intersecting a circular tube of equal radius with the geometric surface of the covering to produce segment lines equidistant along the surface, taking any contour boundary of the geometric surface of the covering and obtaining the length L2 of the boundary; S3-22, extend the selected contour boundary at both ends with G2 curvature ; S3-23, take the curve after extending the boundary as the reference; In S31, the subroutine method S3-3 specifically adopts the section plane for determining the angle with the geometric plane as a reference, and includes the following steps: S3-31, a method for producing equidistant lines of a two-dimensional plane by intersecting an equidistant cutting plane with a geometric surface of a covering; S3-32, extract the coordinate values ​​of each corner point on the outer contour of the geometric surface of the covering (X i ,Y i ,Z i ); S3-33, compare the XY coordinates of each corner point and take the smallest point as the geometric origin and use any adjacent edge as the reference boundary; S3-34, determining the XY plane projection angle α between the target path and the starting boundary; S3-35. According to the angle α, a section plane is set at the origin, which is parallel to the direction of the target path and is orthogonal to the XY plane; S3-36, take the set section plane as the reference; S4 is specifically: S4-1, obtaining multiple groups of initial equidistant segment lines; S4-2, obtaining a plurality of initial surface equal radius circular tube intersection lines; S4-3. Obtain multiple initial surface equidistant cutting plane intersection lines.

2. The equidistant segment line printing path planning method for curved surface coverings based on FDM printing according to claim 1, characterized in that: S1 is specifically: S11, obtaining the geometric surface of the covering; S12, determining whether it is necessary to perform a three-dimensional scan on the surface of the existing component serving as the base; if necessary, using a three-dimensional scanner to scan the surface of the component to be covered to obtain a point cloud model, and processing the point cloud model into a three-dimensional model, and inputting the geometric surface of the covering into the algorithm end; if not necessary, directly inputting the geometric surface of the covering into the algorithm end; S13, identifying whether the geometry type is Mesh or NURBS, if not, converting the geometry type to Mesh or NURBS based on the RhinoCommon principle of the RH-GH modeling software, and entering S14; if yes, directly entering S14; S14. Check the integrity of the geometric surface, that is, whether there is any broken surface or defect. If so, quickly repair the surface by using the mesh point mapping surface repair method for Mesh and the embedding surface repair method by extracting the characteristic points and lines on NURBS to obtain the geometric surface of the covering object for calculation. If not, directly obtain the geometric surface of the covering object for calculation.

3. The equidistant segment line printing path planning method for curved surface coverings based on FDM printing according to claim 1, characterized in that: S2 is specifically: Determine whether to use the scanned component as the printing base. If not, set a base height value H and then raise the geometric surface of the covering object by H height, extract the outer contour of the raised geometric surface of the covering object, and project the outer contour onto the base plane. Then input the maximum layer height value h that the printer can extrude, generate [N=Ceiling(H / h)] transition lines between the raised outer contour and the projection line of its base plane, and arrange the N transition lines, the contour line of the raised geometric surface of the covering object and its projection contour line on the base plane in order from bottom to top according to the spatial position. If so, the scanned component is placed on the base platform of the printer, and the machine position calibration function is used to determine the spatial position P0[X0, Y0, Z0] of the scanned component in the machine coordinate system.

4. The equidistant segment line printing path planning method for curved surface coverings based on FDM printing according to claim 1, characterized in that: S4 is specifically: S4-1, obtaining multiple groups of initial equidistant segment lines, including the following steps: S4-11, obtaining the reference surface geometric center C1 and several directly adjacent surrounding mesh vertices; S4-12, merging and averaging the repeated mesh vertices at all positions on the geometric surface of the covering so that the points at the positions of the mesh vertices are unique; S4-13, calculating the distance and vector from all mesh vertices to the surface geometric center C1, and setting the printer line width W1 according to the printer configuration; S4-14, setting the maximum number of operation points P for each equidistant point, and obtaining a number of offset directions based on the mesh vertices adjacent to the surface geometric center C1; S4-15, offsetting a number of equidistant points based on the vector calculated based on the mesh vertices; S4-16, determine whether the number of the same group of equidistant points on the surface is greater than or equal to 2. If so, remove the mesh vertices and surface geometric center C1 that have participated in the calculation, and calculate the distance D between the remaining C1 on the surface and the group of equidistant points i and vector V i , repeat S4-15 above until the number of the same group of equidistant points on the surface is less than 2; S4-17, obtaining a plurality of groups of equidistant points based on surface geodesic distances; S4-18, connect several equidistant points of the same group of polylines; S5 is as follows: S5-1. Process multiple groups of equidistant segment lines into a continuous curve and set extrusion properties for each part, including the following steps: S5-11, obtaining a plurality of groups of curves with equidistant offsets based on the surface geodesic distance, and setting extrusion attributes T and F, where T represents extrusion and F represents no extrusion; S5-12, connect multiple curves in the same group; S5-13, judging whether a closed curve is obtained, if not, blending multiple segments of non-connected curves in several circle groups, then setting T attribute to the non-connected curve parts, setting F attribute to the blended curve parts, and combining them into a closed curve; if yes, setting T attribute to the curve; S5-14, sort by distance from the surface geometric center C1 from far to near; S5-15, set a number of equidistant points on the multi-circle closed curve according to the length and accuracy; S5-16, transfer rank to multiple groups of equidistant points; S5-17, set a matrix sequence relationship, set the Nth data of each group and the N+1th data of the sub-group to be the same array, and so on, and reverse the rank according to the set sequence relationship of the equidistant point groups; S5-18, flatten into a one-dimensional array according to the order within the matrix; S5-19. Connect all the points in the one-dimensional array in order to form a continuous curve.

5. The equidistant segment line printing path planning method for curved surface coverings based on FDM printing according to claim 1, characterized in that: S4 is specifically: S4-2, obtaining multiple initial surface equal radius circular tube intersection lines, including the following steps: S4-21, obtain the extended boundary line of the benchmark reference; S4-22, comparing the lengths of two adjacent sides of the extended boundary line, and taking the length E2 of the longer side; S4-23, set the print line width W2 according to the printer configuration, and calculate the number of loop operations N2=E2 / W2; S4-24, making a circular tube with the extended boundary line as the center line and the line width W2 as the diameter; S4-25, cut the surface to get the intersection line; S4-26, judging whether the number of intersection lines is less than N2, if so, making a circular tube with the intersection line as the center line and the line width W2 as the diameter, repeating the above step S4-25 to generate new intersection lines until the number of intersection lines reaches N2; S4-27, the starting boundary line and the intersection line are arranged sequentially on the geometric surface of the covering; S5 is as follows: S5-2, processing multiple surface equidistant circular tube intersection lines and connecting them into a curve, including the following steps: S5-21, obtaining equidistant curves on the geometric surface of the sequentially arranged covering; S5-22, obtain all endpoints of all equidistant curves; S5-23, connect corresponding endpoints along the geometric surface of the covering in end-to-end order using the geodesic method; S5-24. Combine all curves on the geometric surface of the covering into a continuous curve.

6. The equidistant segment line printing path planning method for curved surface coverings based on FDM printing according to claim 1, characterized in that: S4 is specifically: S4-3, obtaining multiple initial surface equidistant cutting plane intersection lines, including the following steps: S4-31, obtaining a section plane of a datum reference; S4-32, use the Bounding Box method to find the smallest cube that can enclose the geometric surface of the covering; S4-33, connect all the spatial diagonals of the cube and compare their lengths, and take the longest diagonal E3; S4-34, set the print line width W3 according to the printer configuration, and calculate the number of arrays N3=E3 / W3; S4-35, cutting the geometric surface of the covering along the section plane of the normal vector array N3 and intersecting with the geometric surface of the covering to obtain a plurality of intersection lines; S5 is as follows: S5-3, processing multiple surface equidistant cutting plane intersection lines and connecting them into a curve, including the following steps: S5-31, obtaining intersection lines between the sequentially arranged equidistant cutting planes and the geometric surface of the covering; S5-32, obtain all intersection endpoints; S5-33. Get the length parameter λ of all endpoints on the boundary of the covering geometric surface i ; S5-34, the boundaries of the covering geometric surface are broken at several length parameters; S5-35, setting the starting moving direction V3 of the printing path, and removing the separated boundary intervals according to the path direction; S5-36. Connect all intersecting lines and the processed boundaries into a continuous curve.

7. The equidistant segment line printing path planning method for curved surface coverings based on FDM printing according to claim 1, characterized in that: S6 is specifically: S61, obtaining a continuous curve of the geometric surface of the covering and analyzing the curvature change; S62, select the curvature continuity standard between G0 and G3; S63, extracting Gn discontinuity points on the geometric surface of the covering according to the set curve discontinuity; S64, analyzing the parameter positions of a number of discontinuous points on the continuous curve; S65. Creating a sphere of relative radius at corresponding points according to the parameter positions of the plurality of points; S66, intersecting a number of spheres with the continuous curve, and obtaining the Boolean difference of the curve on the number of spheres; S67, setting a relative fitting convex value B, and blending the beginning and the end of the disconnected curve by relative arc fitting; S68, mapping the blended part of the curve onto the geometric surface of the covering; S69, combining the disconnected curve and the arc fitting mixed curve into a continuous path curve; S7 is specifically: S71, converting the path curve into a number of equidistant points according to printing accuracy requirements; S72, calculating the UV point values ​​of all equidistant points on the geometric surface; S73, calculating the relative extrusion value of each point according to the set printing line width and the statistical UV value of the equidistant points; S74, setting machine parameters of the printer, including adjusting the extrusion ratio, adjusting the printing speed and adjusting the hot end temperature; S75, translating the machine parameters into the parameters of the geometric path to generate a G-Code file, and performing a simulation of the movement of the machine along the surface path curve and the extrusion control in the 3D visualization software RH-GH; S76, determining whether the path simulation generates collisions or gaps, and if so, readjusting the machine parameters until there are no collisions or gaps, and then executing the printing file.

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