CN111923185B

CN111923185B - 3D printing method and system for ceramic die-free direct writing

Info

Publication number: CN111923185B
Application number: CN202010670321.8A
Authority: CN
Inventors: 吕琳; 刘文强; 周宇; 钟凡超; 闫鑫
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2020-07-13
Filing date: 2020-07-13
Publication date: 2021-05-07
Anticipated expiration: 2040-07-13
Also published as: CN111923185A

Abstract

The application discloses a 3D printing method and a system of ceramic die-free direct writing, comprising the following steps: generating an initial swept curved surface based on the input first profile curve, the input second profile curve, the input track curve and the input set central point; mapping the initial swept curved surface to an actual printing coordinate system to obtain a swept curved surface model; calculating a ceramic modeless direct-writing reciprocating type printing path for the swept surface model; calculating the extrusion amount of the ceramic slurry of the ceramic die-free direct writing to the swept surface model; and 3D printing of the sweep curved surface model ceramic modeless direct writing is completed.

Description

3D printing method and system for ceramic die-free direct writing

Technical Field

The application relates to the technical field of 3D printing, in particular to a 3D printing method and system for ceramic modeless direct writing.

Background

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

The ceramic material has wide application in the fields of chemical industry, machinery, electronics, aerospace, biomedical engineering and the like, and is an indispensable material for the development and application of modern high-end technology. The ceramic material has the characteristics of high wear resistance, high mechanical strength, and good thermal stability and chemical stability. However, the extremely high hardness and brittleness of the ceramic parts make the machining thereof extremely difficult, and not only the cutting tool suffers from severe wear, but also the ceramic parts may suffer from defects such as cracks during the machining process, thereby making it difficult to obtain good surface quality and dimensional accuracy. As a new manufacturing mode, the additive manufacturing technology has the characteristics of personalized manufacturing and quick response, and can meet the production requirements of personalization, complication, light weight and refinement of ceramic products.

Despite the rapid development of additive manufacturing techniques and printed materials, modeling tools for ceramic additive manufacturing are still in the development stage. For users without 3D modeling expertise or with less skilled experience, the demand for easy-to-use modeling tools is high, and after completing geometric modeling of ceramic additive manufacturing, printing limitations such as printability, support-free, etc. during ceramic modeless direct writing need to be considered.

In the process of implementing the present application, the inventors found that the following technical problems exist in the prior art: the ceramic die-free direct-writing forming has the following limiting conditions: the ceramic material is continuously extruded, i.e. the printing path is a strictly single continuous path, without stopping; the model is free-standing, i.e. no external support is required; in the whole printing process, the printing head and the model have no collision; there is sufficient overlap between layers.

Disclosure of Invention

In order to solve the defects of the prior art, the application provides a 3D printing method and a system of ceramic modeless direct writing;

in a first aspect, the present application provides a method of 3D printing of ceramic die-less direct writing;

the 3D printing method of the ceramic die-free direct writing comprises the following steps:

generating an initial swept curved surface based on the input first profile curve, the input second profile curve, the input track curve and the input set central point;

mapping the initial swept curved surface to an actual printing coordinate system to obtain a swept curved surface model;

calculating a ceramic modeless direct-writing reciprocating type printing path for the swept surface model;

calculating the extrusion amount of the ceramic slurry of the ceramic die-free direct writing to the swept surface model;

and 3D printing of the sweep curved surface model ceramic modeless direct writing is completed.

In a second aspect, the present application provides a ceramic modeless direct write 3D printing system;

ceramic modeless direct-write 3D printing system, comprising:

a generation module configured to: generating an initial swept curved surface based on the input first profile curve, the input second profile curve, the input track curve and the input set central point;

a mapping module configured to: mapping the initial swept curved surface to an actual printing coordinate system to obtain a swept curved surface model;

a print path calculation module configured to: calculating a ceramic modeless direct-writing reciprocating type printing path for the swept surface model;

an extrusion amount calculation module configured to: calculating the extrusion amount of the ceramic slurry of the ceramic die-free direct writing to the swept surface model;

a print module configured to: 3D printing of sweep surface model ceramic modeless direct writing is completed based on the printing path and the extrusion amount of the ceramic slurry.

In a third aspect, the present application further provides an electronic device, including: one or more processors, one or more memories, and one or more computer programs; wherein a processor is connected to the memory, the one or more computer programs are stored in the memory, and when the electronic device is running, the processor executes the one or more computer programs stored in the memory, so as to make the electronic device execute the method according to the first aspect.

In a fourth aspect, the present application also provides a computer-readable storage medium for storing computer instructions which, when executed by a processor, perform the method of the first aspect.

In a fifth aspect, the present application also provides a computer program (product) comprising a computer program for implementing the method of any of the preceding first aspects when run on one or more processors.

Compared with the prior art, the beneficial effects of this application are:

1. a user interaction modeling tool for modeless direct writing of ceramics is presented. By introducing a sweep curve modeling scheme of user interaction, a user can generate a continuous, support-free and collision-free mode-free direct-writing forming path only by inputting two contour curves and one track curve as a design intention. The result shows that the modeling tool of the application expands the range of printing models in the ceramic die-free direct writing molding, and the printing process is reliable.

2. The reciprocating path generation method of the self-adaptive inclination angle integrates printing process interference detection in a modeling tool and controls the extrusion amount of ceramic slurry in a printing path so as to ensure the continuity of the printing path and avoid model collapse.

3. The method utilizes the sweep curve as a modeling tool, connects modeling and printing processes under the condition of considering printing constraint, and directly converts the design intention of a user into a ceramic modeless direct-writing printing file. The method aims at the characteristics that ceramic overflows from a spray head to generate interference on a printed part due to material inertia in the idle stroke movement process of the ceramic modeless direct writing, so that a printing model is deformed and printing fails.

4. The present application designs an adaptive zig-zag helical print path along a sweep curve to ensure that the extruder achieves a single continuous path without interruption. Meanwhile, collision between the extrusion head and the printing model and collapse caused by overlarge inclination angle of the model are avoided, and finally, the effectiveness of the method is verified through experiments.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.

FIG. 1 is a flow chart of a method of the first embodiment;

FIGS. 2(a) -2 (e) are schematic diagrams of modeling and printing principles of the first embodiment;

FIG. 3 is a schematic graph of swept surface control of the first embodiment;

FIG. 4(a) is a schematic view of the contour line Cs of the first embodiment;

FIG. 4(b) is a schematic diagram of the contour line Ct of the first embodiment;

FIG. 4(c) is a schematic trace line diagram of the first embodiment;

FIG. 4(d) is a schematic view of the generated sweep model of the first embodiment;

5(a) -5 (c) are diagrams comparing different patterns of the linear interpolation of the contour line of the first embodiment;

FIG. 6 is a diagram illustrating an adjusted interpolation curve according to the first embodiment;

FIGS. 7(a) -7 (b) are schematic diagrams of input modification of the first embodiment;

FIGS. 8(a) -8 (b) are schematic diagrams of an interference collision of the first embodiment;

FIG. 9 is a schematic view of a print path of the first embodiment;

FIG. 10 is a schematic diagram of a print path generation algorithm of the first embodiment;

FIGS. 11(a) -11 (b) are schematic diagrams illustrating the adaptive throughput comparison effect of the first embodiment;

FIG. 12 is a schematic diagram of the adaptive extrusion principle of the first embodiment;

fig. 13 is a schematic view of the first embodiment after the extrusion amount is adjusted.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and it should be understood that the terms "comprises" and "comprising", and any variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The embodiments and features of the embodiments in the present application may be combined with each other without conflict.

Example one

The embodiment provides a 3D printing method of ceramic die-free direct writing;

s101: generating an initial swept curved surface based on the input first profile curve, the input second profile curve, the input track curve and the input set central point;

s102: mapping the initial swept curved surface to an actual printing coordinate system to obtain a swept curved surface model;

s103: calculating a ceramic modeless direct-writing reciprocating type printing path for the swept surface model;

s104: calculating the extrusion amount of the ceramic slurry of the ceramic die-free direct writing to the swept surface model;

s105: and 3D printing of the sweep curved surface model ceramic modeless direct writing is completed.

As one or more embodiments, before the step S101, the method further includes:

s100: and acquiring the input first profile curve, the input second profile curve, the input track curve and the input set central point.

Illustratively, the method of the application adopts sweep modeling, sweep curve modeling is carried out by defining a contour line and a track line, and a model curve is recorded by adopting a mouse to draw points.

First, user interaction modeling is performed, and the user is required to draw two contour curves Cs, Ct and a trajectory curve ψ, which is centered at o (see fig. 2(a) -2 (e)).

As one or more embodiments, in S101, an initial swept curved surface is generated based on the input first profile curve, the input second profile curve, the input trajectory curve, and the set central point; the method comprises the following specific steps:

and generating an initial swept curved surface based on the sampling point of the first profile curve, the sampling point of the second profile curve, the sampling point of the track curve, the central point and the gradual change profile curve between the first profile curve and the second profile curve.

The gradual profile curve is a curve at an intermediate position obtained by linear interpolation between the first profile curve and the second profile curve along the trajectory curve.

The application generates a swept surface defined by these parameters and derives a print path based thereon.

Illustratively, the user plots two contour curves Cs, Ct and one trajectory curve ψ, centered at o. These four parameters then determine the swept surface, as shown in fig. 3.

Assuming that the printing direction is the Z-axis, Cs and Ct are defined in the XOZ plane, and their starting point Z-axis value is 0, the trajectory ψ is defined in the XOY plane. In order to provide a greater degree of freedom in design, it is also possible to introduce curves that are designed in advance and satisfy a continuous condition.

Three drawing interfaces are provided, wherein fig. 4(a) and 4(b) are contour line drawing interfaces, and fig. 4(c) is a trace line drawing interface, where the coordinate system of the pixel points in the drawing interface is set as the canvas coordinate system. By collecting the pixel values of the user drawn curves in fig. 4(a) and 4(b), Cs and Ct contours are obtained respectively, and are sorted from small to large according to the y value of the pixel, and finally, contours Cs and Ct composed of the pixels are obtained. Meanwhile, the same method is used for acquiring the pixel values in fig. 4(c) to obtain a path of the sweep trajectory, which is called a trajectory psi, but a starting point needs to be found in the trajectory and all the points need to be sequenced. Fig. 4(d) is a schematic diagram of the generated sweep model.

Further, generating an initial swept curved surface based on the sampling point of the first profile curve, the sampling point of the second profile curve, the sampling point of the track curve, the central point, and the gradual change profile curve between the first profile curve and the second profile curve; the method comprises the following specific steps:

and connecting the points on the three curves layer by layer in a zigzag mode according to the one-to-one correspondence relationship between the points to generate an initial swept curved surface.

As one or more embodiments, the obtaining step includes:

and resampling the first profile curve, the second profile curve and the track curve to obtain a sampling point of the first profile curve, a sampling point of the second profile curve, a sampling point of the track curve and coordinates of the sampling point of each curve in a canvas coordinate system.

It should be understood that the swept surface model generation method is to use each sampling point on the curve as a layer, and generate the surface model by directly connecting the sampling points on the curve, but since the number of actual pixel points on the input curve is too many and the smoothness of the curve formed by the currently collected pixels is low, and the subsequent resampling operation will further reduce the smoothness of the curve, the pixel points are processed by using an arithmetic average filtering algorithm first, so that the curve is smooth.

For any input curve, a total of M coordinates on the curve are set as p_i(x_i,y_i) And if the pixel point of M is 1,2, the coordinate of the pixel point processed by the filtering algorithm is changed into:

the smoothness of the algorithm of taking N to 7 is better, and the number of the processed pixel points is changed into M-N.

The problem that the y value difference of the smoothed contour curve is not uniform on the same curve still exists, so the pixel value after smoothing needs to be resampled to prepare for next path generation.

Exemplarily, resampling is carried out on the first profile curve and the second profile curve, and sampling points of the first profile curve and sampling points of the second profile curve are obtained; the method comprises the following specific steps:

firstly, translating a first contour curve Cs and a second contour curve Ct, and enabling the lowest points of the first contour curve Cs and the second contour curve Ct to be located at the origin of a canvas coordinate system;

and selecting points which meet the requirement of the printing layer thickness and have the y value difference of two sampling points smaller than a set threshold value on the first contour curve Cs and the second contour curve Ct.

Assuming that the highest point of the first profile curve Cs is lower than the highest point of the second profile curve Ct, taking the first profile curve Cs as a reference, y_{A_max}Represents the maximum coordinate value of y-axis on Cs, y_{B_max}Represents the maximum value of the y-axis coordinate on Ct.

Setting the desired layer thickness T, i.e. the distance between two adjacent points on the same contour, according to the printing machine parameter settings, and then selecting them together

Points, where the value of y at the k-th point should satisfy equation (1):

through the screening, the fact that the y value difference of two adjacent points on the contour line is smaller than a set threshold value is achieved.

In order to make the number of sampling points on the first profile curve Cs and the second profile curve Ct equal, prepare for one-to-one connection of the sampling points on the next profile line, also set the sampling values of two adjacent points on the second profile curve Ct, i.e. the print layer thickness, and set the layer thickness on the second profile curve Ct as the layer thickness

And (4) calculating and screening through a formula (1), and resampling on the second contour curve Ct to obtain points which are equivalent to the points obtained after resampling on the contour line of the first contour curve Cs.

By the screening calculation of the sampling points, the coordinates of the pixel points used in the actual printing path on the drawing interface, namely the coordinates in the canvas coordinate system, are obtained, and the lowest points of the two profiles Cs and Ct are set as the origin of the canvas coordinate system.

Further, the obtaining step of the gradual change profile curve between the first profile curve and the second profile curve comprises:

and obtaining a gradual change contour curve between the first contour curve and the second contour curve in a linear interpolation mode.

Illustratively, a gradual change profile curve between the first profile curve and the second profile curve is obtained through a linear interpolation mode; the method comprises the following specific steps:

the filtered trajectory line psi is set to have N in total_locusPoints, which is also the number of gradual contours between the first contour curve and the second contour curve;

and obtaining the gradual change contour curve between the first contour curve and the second contour curve by adopting a linear difference mode according to the quantity of the gradual change contour lines between the first contour curve and the second contour curve.

Let the ith point on the trajectory line, which is also the lowest point of the ith contour line, be p for any point on this contour line_jAnd the coordinate formula (2) on the canvas coordinate system is as follows:

in order to enable the built sweep model to be more diversified and increase the degree of freedom of modeling, a linear interpolation mode of the contour line and an interpolation mode of cubic spline interpolation of a natural boundary are provided.

Besides, the method also increases the adjustment mode of the vertex control curve of the contour line, the vertex control curve is superposed with the vertex of the interpolation contour line, the nonlinear interpolation of the contour line can be realized by adjusting the vertex control curve, and three different interpolation modes are adopted from left to right in the graphs of 5(a) to 5(c), so that the constructed model is more diversified. FIG. 6 is a vertex control curve modulation interface.

As one or more embodiments, in S102, mapping the initial swept surface to an actual printing coordinate system to obtain a swept surface model; the method comprises the following specific steps:

mapping coordinates of points on the first contour curve, the second contour curve and the gradual change contour curve in the initial swept curved surface in a canvas coordinate system into coordinates in an actual printing coordinate system; and after mapping all the points, connecting adjacent points in the actual printing coordinate system to obtain the swept surface model.

As one or more embodiments, after the step of generating an initial swept surface, the step of mapping the initial swept surface into an actual printing coordinate system further includes, before the step of obtaining a swept surface model: and judging whether the initial swept curved surface has self-intersection or not, and performing self-intersection removal processing on the initial swept curved surface with self-intersection.

Further, the step of judging whether the initial swept curved surface has self-intersection and performing self-intersection removal processing on the initial swept curved surface having self-intersection includes the following specific steps:

firstly, traversing any two points on a trajectory psi, and if a connecting line between the two points approaches to or passes through a central point o, further checking a middle contour curve where the two points are located;

traversing the point pairs with one-to-one correspondence on the two middle contour curves from bottom to top along the z axis, and if the Euclidean distance between the two points is approximate to 0, indicating that the swept curved surfaces have self-intersection;

for swept surfaces where self-intersections exist, the way to remove the self-intersections is to iteratively compress Cs, Ct along the x-axis until the self-intersection disappears.

Illustratively, even if there is no intersection between the Cs, Ct and ψ curves, the curved surface generated during sweep may self-intersect (fig. 7 (b)). Therefore, it is necessary to detect the self-intersection of curved surfaces.

As one or more embodiments, after the step of generating an initial swept surface, the step of mapping the initial swept surface into an actual printing coordinate system further includes, before the step of obtaining a swept surface model: and comparing the overhang angle of each sampling point of the initial swept curved surface with a set threshold value, and correcting the overhang angle larger than the threshold value to ensure that the initial swept curved surface realizes self-support.

It will be appreciated that if the angle of inclination of a certain point is greater than a threshold angle, that point will collapse without a support structure during printing. The present application regards a swept curved surface as a combination of a profile curve and its interpolated curve, tracks each profile curve from the sweep start point, and locally tilts the control polygon when the overhang angle exceeds the collapse angle. For the profile curve, the inclination angle of one point is set to the angle between the tangent of the point and the printing direction (Z axis), and if the angle exceeds a threshold angle, the point is shifted until its inclination angle satisfies the threshold, and the same operation is taken for the points subsequent to the point to correct the entire curve.

Illustratively, fig. 7(a) shows the left contour curve adjusted until the tilt angles of all points thereon satisfy the threshold angle, and the right contour curve is obtained after the adjustment.

It should be understood that in S102, the initial swept surface is mapped to the actual printing coordinate system, so as to obtain a swept surface model; the method comprises the following specific steps:

by the above operation, composition N has been obtained_locusThe +2 contour lines and their coordinates on the respective canvas coordinate system. And then mapping the coordinates of the pixel points in the canvas coordinate system to the coordinates in the actual printing coordinate system.

First, a "center point" C (x) is defined in the canvas coordinate system_c,y_c) And the length of the canvas is set to be L, and any point p (x) on any contour line is considered₀,y₀) And a point p on the trajectory line representing the contour line_locus(x₁,y₁0), the coordinate formula (4-7) of p in the actual printing coordinate system will be obtained by mapping:

and after all the points are mapped, connecting the adjacent points, namely completing the sweep, and obtaining the whole sweep model.

As one or more embodiments, in S103, for the swept surface model, a ceramic modeless direct-write shuttle printing path is calculated; the method comprises the following specific steps:

s1031: inputting a sweep curve and hardware parameters of the sweep curve model, wherein the hardware parameters comprise the length of a printer nozzle, the minimum layer thickness printable by the printer, the minimum path width printable by the printer and the maximum path width;

s1032: calculating the difference value of the z-axis values of the first contour curve and the second contour curve in the actual printing coordinate system, judging whether the difference value of the z-axis values is smaller than a set threshold value, if so, generating a reciprocating printing path, and ending; if not, go to S1033;

s1033: dividing the second contour curve into an upper part and a lower part, generating a first printing path for the lower part, and maintaining an interference distance for the upper part to generate a second printing path;

s1034: and combining the first printing path and the second printing path to obtain a final printing path.

Further, in S1031, inputting a sweep curve of the sweep curve model; the method specifically comprises the following steps: a first profile curve, a second profile curve, and a trajectory line;

further, in S1032, generating a shuttle printing path includes:

equidistant sampling is carried out on the first contour curve and the second contour curve to generate a sampling point set which has one-to-one correspondence and is the same in quantity, a middle gradual change contour curve is generated along a track line based on interpolation, and then points which have one-to-one correspondence are connected in a zigzag mode to generate a reciprocating type printing path;

further, in S1033, the second profile curve is divided into an upper part and a lower part according to the following principle: assuming that the height of the first contour curve is smaller than that of the second contour curve and the height difference between the two contour curves is larger than the length threshold of the printer nozzle, dividing the second contour curve at the position where the z-axis value is the height value of the first contour curve plus the length of the printer nozzle to obtain an upper part and a lower part;

further, in S1034, for the lower portion to generate the first printing path, the specific steps include: the lower parts of the first contour curve and the second contour curve which is segmented before are re-equidistantly sampled to generate the same number of sampling points, a gradual change contour curve is re-generated along the trajectory line based on interpolation, and then points which have one-to-one correspondence are connected in a zigzag mode to generate a first printing path;

further, in S1034, the step of generating the second printing path while maintaining the interference distance for the upper portion includes: generating a Z-axis value of a backtracking point by adding the sampling distance of the second contour curve to the height of the first contour curve in an iteration mode, searching the highest point of the transition contour curve which is closest to the first contour curve for each calculated Z-axis value, wherein the point is the calculated backtracking point, and then connecting all the backtracking points with the residual points on the upper portion of the second contour curve in a zigzag mode to generate a second printing path;

further, in S1035, the first printing path and the second printing path are merged to obtain a final printing path, and the specific steps include: when the second printing path is generated, the final printing path is formed by taking the end point of the first printing path as the starting point and then combining the two-stage paths.

It should be understood that the model generated by the sweep curve in the present application is non-closed, errors will occur by adopting the conventional method of slicing in layers, and the conventional mode of printing in layers according to the z axis will cause serious 'step phenomenon', destroy the original shape and affect the appearance. Therefore, on the basis of a layered slicing process by using a conventional model, a novel path generation method for the model is provided, ceramic slurry is extruded by a spray head all the time when the ceramic slurry is printed along the path in the printing process until the ceramic slurry reaches a terminal point, and the printing layer thickness is changed continuously in order to meet the shape of contour lines with different heights.

Each point on the contour line is used as one layer, and the printing path is generated according to the one-to-one corresponding relation with the points on other contour lines. Two different print path methods will be used depending on the height difference between the contour lines Cs, Ct.

Due to the characteristic of the ceramic die-free direct-writing forming, a continuous printing path needs to be generated for printing the whole model, so that the extrusion of the ceramic material is continuous and the internal filling is not needed. The advantage of using a ceramic material, i.e. a single path that is sufficiently stable, is to print only the swept surface without the filling structure. The present application contemplates a continuous spray path that may be used to create swept surfaces, such as contoured walls. The ceramic product is generated by using a single printing track by utilizing the characteristic of large extrusion amount of ceramic additive manufacturing.

Illustratively, for two contour curves Cs and Ct, equidistant sampling is first performed according to the length of the curve on the Z-axis to obtain two sampling sets Vs, Vt, respectively, having the same number of points. The shorter of Cs and Ct is sampled at a distance in the Z-axis that is the minimum layer thickness Δ Z that the printer can print₀While the other is readily derived. Let it be assumed that n point samples are taken at the trajectory curve ψ. Linear interpolation between Vs and Vt is then performed, generating n-2 transition curves represented by the interpolation points. Points of Vs, Vt and interpolation points of the transition curve correspond one-to-one in the Z-axis sequence, while converting the canvas coordinates of the contour curve and the transition curve into world coordinates centered at o.

The heights of Cs and Ct are represented by Z (Cs) and Z (Ct), respectively. If the difference in the height of Cs and Ct on the Z-axis is less than H, the zig-zag shower path can simply be applied along the trajectory. The extruder keeps printing from the point of vs (vt) to the corresponding point of vt (vs) by means of the interpolated point on the same layer, then returns to vs (vt) from the point of the next layer vt (vs), repeating this spiral reciprocal printing process in the Z axis from bottom to top until the model is completed. In the direct-write molding process, the height position of the extruder continuously changes in the same layer as the height of two corresponding sampling points changes.

However, if the height difference between Cs and Ct in the Z-axis is greater than H, the zigzag head path described above will cause a collision between the extruder and the printed pattern, see fig. 8(a) and 8 (b). To avoid such interference collisions, the present application proposes a new print path planning method that keeps the height difference of the two end points in the same print layer below H.

The basic approach taken by this application is to divide the path into two parts and generate a zig-zag path. For ease of computational explanation, Cs is assumed to be shorter than Ct. The application determines the maximum value of Z but less than the point of Z (cs) + H in Vt. This point divides Ct into two upper and lower parts. For the lower part, the height difference between the two profile curves is smaller than H, so the path generation is the same as described above. As shown in fig. 9, the print path is schematic.

For the upper half, the generated path follows the following steps: the Z-axis value of the return point of Z (cs) is sampled by the sampling distance of Ct. The highest points are found on the transition curve, the distance between the highest points is the nearest, and the Z-axis value is used as the final return point. Then, printing is performed starting from the highest point of Cs and with increasing layer height until the lowest of the remaining Ct samples is reached. Printing will then start from this point to the lowest return point and gradually increase the layer height, repeating this round trip between the return point and the remaining sample points of Ct until the print path generation for the entire model is completed. The algorithm flow is shown in fig. 10.

As one or more embodiments, in S104, for the swept surface model, the extrusion amount of the ceramic slurry for the ceramic die-less direct writing is calculated; the method comprises the following specific steps:

s1041: inputting a minimum printing path width value and a maximum printing path width value;

s1042: calculating the line width and mass center distance of two adjacent layers;

s1043: judging whether the ratio of the line width centroid distance of the two adjacent layers to the minimum value of the printing path width is smaller than a set threshold value, if so, setting the printing path width as the minimum value of the printing path width, and entering S1044; if not, setting the width of the printing path to be a triple value of the line width and mass center distance of two adjacent layers, and entering S1044;

s1044: the print path width is converted into the extrusion amount of the ceramic slurry of the corresponding layer.

As one or more embodiments, in S105, 3D printing of the swept surface model ceramic modeless direct writing is completed; the method comprises the following specific steps:

and finishing the 3D printing of the sweep curved surface model ceramic die-free direct writing based on the ceramic die-free direct writing reciprocating type printing path and the extrusion amount of the ceramic slurry of the ceramic die-free direct writing.

The printing path is adjusted in the ceramic additive manufacturing process, and collision is avoided in the continuous extrusion movement process. At the same time, strict manufacturing constraints are also imposed on the printing path to ensure that the printing model does not collapse during the whole printing process. The printing model is adapted by optimizing the path and the extrusion amount of the spray head, so that the printability is ensured and the stability of the printing model is enhanced.

It will be appreciated that since the extrusion of ceramic paste for die-less direct writing of ceramic is typically greater than for other additive manufacturing approaches, the calculation of the extrusion for each moving step in the print path is also a critical issue. Insufficient extrusion results in less support of adjacent layers, resulting in a collapsed mold, as shown in fig. 11(a) and 11 (b). On the other hand, too much extrusion amount results in rough surface quality and more printing manufacturing time, resulting in uncertainty of the ceramic product. Therefore, the present application proposes a path generation method that adapts to the extrusion amount.

Illustratively, as shown in fig. 12, the horizontal distance of two adjacent dots is represented by s, the overlap width of two adjacent layers is represented by Δ a, and w is the direct-write line width. θ is the angle between the tangent to the dot and the print direction.

The strategy of the application is to ensure that the current layer or the gravity center of the current layer is more than half of the line width of the adjacent layer. Here, the proportional threshold is set to 2/3, and the initial line width of the print path is w_min. While keeping the line widths of the current layer and its adjacent previous layer equal and adjusting simultaneously until the ratio reaches 2/3. If the line width is less than w_minThen reset it to w_min. After unsupported correction prior to this application, the line width was not greater than w_max. After traversing all print paths, the overlap width of each layer is greater than half its own width. After the printing path and the width of the printing line are obtained, the extrusion amount e of each point in the printing process can be determined. The detailed algorithm is described in Table 5-3, and an example of the extrusion amount adjusted is shown in FIG. 13.

The printing path and the extrusion amount of the ceramic die-free direct-writing additive manufacturing equipment are customized by the application, so that an effective model is manufactured by printing, and collision or model collapse cannot occur in the printing process. To meet the printing constraints, the present application uses the print path and extrusion volume of a ceramic die-less direct write extrusion head as the calculated variables. In order to avoid collision between the extruder and the printing model, the height difference between two corresponding points on the Cs and the Ct is smaller than the height of the extruder. While for two profile curves having a height difference greater than the height of the extruder, an adaptive return point is calculated along the print path, thus generating an adaptive zig-zag reciprocating path. And meanwhile, the extrusion amount of the ceramic die-free direct writing is set to be the minimum value, and then the extrusion amount is optimized according to the overlapping degree of layers, so that the model is prevented from collapsing. And finally, the printing test is passed, and the effect is good.

Example two

The present embodiment provides a ceramic modeless direct-write 3D printing system;

ceramic modeless direct-write 3D printing system, comprising:

It should be noted here that the generating module, the mapping module, the printing path calculating module, the extrusion amount calculating module, and the printing module correspond to steps S101 to S105 in the first embodiment, and the modules are the same as the corresponding steps in the implementation example and application scenarios, but are not limited to the disclosure in the first embodiment. It should be noted that the modules described above as part of a system may be implemented in a computer system such as a set of computer-executable instructions.

In the foregoing embodiments, the descriptions of the embodiments have different emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

The proposed system can be implemented in other ways. For example, the above-described system embodiments are merely illustrative, and for example, the division of the above-described modules is merely a logical functional division, and in actual implementation, there may be other divisions, for example, multiple modules may be combined or integrated into another system, or some features may be omitted, or not executed.

EXAMPLE III

The present embodiment also provides an electronic device, including: one or more processors, one or more memories, and one or more computer programs; wherein, a processor is connected with the memory, the one or more computer programs are stored in the memory, and when the electronic device runs, the processor executes the one or more computer programs stored in the memory, so as to make the electronic device execute the method according to the first embodiment.

It should be understood that in this embodiment, the processor may be a central processing unit CPU, and the processor may also be other general purpose processors, digital signal processors DSP, application specific integrated circuits ASIC, off-the-shelf programmable gate arrays FPGA or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, and so on. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.

The memory may include both read-only memory and random access memory, and may provide instructions and data to the processor, and a portion of the memory may also include non-volatile random access memory. For example, the memory may also store device type information.

In implementation, the steps of the above method may be performed by integrated logic circuits of hardware in a processor or instructions in the form of software.

The method in the first embodiment may be directly implemented by a hardware processor, or may be implemented by a combination of hardware and software modules in the processor. The software modules may be located in ram, flash, rom, prom, or eprom, registers, among other storage media as is well known in the art. The storage medium is located in a memory, and a processor reads information in the memory and completes the steps of the method in combination with hardware of the processor. To avoid repetition, it is not described in detail here.

Those of ordinary skill in the art will appreciate that the various illustrative elements, i.e., algorithm steps, described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

Example four

The present embodiments also provide a computer-readable storage medium for storing computer instructions, which when executed by a processor, perform the method of the first embodiment.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. The 3D printing method of the ceramic die-free direct writing is characterized by comprising the following steps:

generating an initial swept curved surface based on the input first profile curve, the input second profile curve, the input track curve and the input set central point; the method comprises the following specific steps: generating an initial swept curved surface based on a sampling point of the first profile curve, a sampling point of the second profile curve, a sampling point of the track curve, a central point and a gradual change profile curve between the first profile curve and the second profile curve;

the sampling points of the first profile curve, the second profile curve and the track curve comprise the following steps: resampling the first profile curve, the second profile curve and the track curve to obtain a sampling point of the first profile curve, a sampling point of the second profile curve, a sampling point of the track curve and coordinates of the sampling point of each curve in a canvas coordinate system;

the gradual change profile curve between the first profile curve and the second profile curve is obtained by the following steps: obtaining a gradual change contour curve between the first contour curve and the second contour curve in a linear interpolation mode; mapping the initial swept curved surface to an actual printing coordinate system to obtain a swept curved surface model;

2. The method as claimed in claim 1, wherein the initial swept surface is mapped to the actual printing coordinate system to obtain a swept surface model; the method comprises the following specific steps:

mapping the coordinates of the sampling point of each curve of the initial swept curved surface in the canvas coordinate system into the coordinates in the actual printing coordinate system; and after mapping all the points, connecting adjacent points in the actual printing coordinate system to obtain the swept surface model.

3. The method as claimed in claim 1, wherein after the step of generating the initial swept surface, the step of mapping the initial swept surface into the actual printing coordinate system and before the step of obtaining the swept surface model, further comprises:

and judging whether the initial swept curved surface has self-intersection or not, and performing self-intersection removal processing on the initial swept curved surface with self-intersection.

4. The method as claimed in claim 3, wherein the overhang angle of each sample point of the initial swept surface is compared with a set threshold value, and the overhang angle greater than the threshold value is corrected to ensure that the initial swept surface is self-supporting.

5. The method as claimed in claim 1, wherein after the step of generating the initial swept surface, the step of mapping the initial swept surface into the actual printing coordinate system and before the step of obtaining the swept surface model, further comprises:

and comparing the overhang angle of each sampling point of the initial swept curved surface with a set threshold value, and correcting the overhang angle larger than the threshold value to ensure that the initial swept curved surface realizes self-support.

6. The method of claim 1, wherein for a swept surface model, a ceramic modeless direct-write shuttle print path is calculated; the method comprises the following specific steps:

inputting a sweep curve and hardware parameters of the sweep curve model, wherein the hardware parameters comprise the length of a printer nozzle, the minimum layer thickness printable by the printer, the minimum path width printable by the printer and the maximum path width;

calculating the difference value of the z-axis values of the first contour curve and the second contour curve in the actual printing coordinate system, judging whether the difference value of the z-axis values is smaller than a set threshold value, if so, generating a reciprocating printing path, and ending; if not, the next step is carried out;

dividing the second contour curve into an upper part and a lower part, generating a first printing path for the lower part, and maintaining an interference distance for the upper part to generate a second printing path;

and combining the first printing path and the second printing path to obtain a final printing path.

7. The method of claim 1, wherein for the swept surface model, the extrusion of the ceramic slurry for the ceramic die-less direct write is calculated; the method comprises the following specific steps:

inputting a minimum printing path width value and a maximum printing path width value; calculating the line width and mass center distance of two adjacent layers;

judging whether the ratio of the line width centroid distance of two adjacent layers to the minimum value of the printing path width is smaller than a set threshold value or not, if so, setting the printing path width as the minimum value of the printing path width, and entering the next step; if not, setting the width of the printing path as a triple value of the line width and the mass center distance of two adjacent layers, and entering the next step;

the print path width is converted into the extrusion amount of the ceramic slurry of the corresponding layer.

8. Ceramic 3D printing system that does not have mould direct writing, characterized by includes:

a generation module configured to: generating an initial swept curved surface based on the input first profile curve, the input second profile curve, the input track curve and the input set central point; the method comprises the following specific steps: generating an initial swept curved surface based on a sampling point of the first profile curve, a sampling point of the second profile curve, a sampling point of the track curve, a central point and a gradual change profile curve between the first profile curve and the second profile curve;

the gradual change profile curve between the first profile curve and the second profile curve is obtained by the following steps: obtaining a gradual change contour curve between the first contour curve and the second contour curve in a linear interpolation mode;

9. An electronic device, comprising: one or more processors, one or more memories, and one or more computer programs; wherein a processor is connected to the memory, the one or more computer programs being stored in the memory, the processor executing the one or more computer programs stored in the memory when the electronic device is running, to cause the electronic device to perform the method of any of the preceding claims 1-7.

10. A computer-readable storage medium storing computer instructions which, when executed by a processor, perform the method of any one of claims 1 to 7.