3DP printer and printing method

Abstract

The invention provides a 3DP printer and a printing method. The 3DP printer comprises a rack used for supporting and a printing head used for stacking printing materials layer by layer according to a preset path. The printing platform is used for controlling the printing head to rotate in the vertical direction; the printing head comprises an extruder and a spray head, the extruder is used for pushing a material from a molten state to the spray head, and the spray head is used for positioning the material at a correct position; the 3D printer is based on three-degree-of-freedom design, the printing quality can be guaranteed, and meanwhile the 3D printer has the advantages of being easy to operate and low in cost; through the printing method provided by the invention, the printing precision is improved, and the interlayer strength of a printed part is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and in particular to a 3DP printer and a printing method. Background Art

[0002] 3D printing, also known as additive manufacturing, is a technology that uses powdered metal or plastic materials to manufacture parts by adding materials layer by layer based on three-dimensional CAD model data. This technology is widely used in industries such as industry, medicine, and construction. Since 3D printing mostly uses the principle of planar layered manufacturing, a stepped structure will inevitably appear when the molded parts have non-straight wall surfaces. This is called the step effect. The step effect will reduce the accuracy of the printed model and increase the roughness of the model surface. At the same time, when processing a single layer, the printer can only extrude materials within the plane. When the cross-sectional size is small, frequent reversal of the extrusion path will also cause the adhesion between layers to decrease, thereby weakening the interlayer strength of the printed parts.

[0003] The design and manufacture of multi-DOF 3D printers, as an important prerequisite for the research and development of curved layer fused deposition modeling (CLFDM), provides the possibility for manufacturing complex geometric shapes, such as 3D printers based on Stewart parallel mechanisms and robotic arms. Existing 3D printers are generally equipped with a nozzle for distributing printing materials and a printing platform for receiving printing materials. In the constructed XYZ space, the objects are printed layer by layer by moving the nozzle and the printing platform. At present, in the process of curved layering, the layering accuracy is low and the work efficiency is low. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a 3DP printer and a printing method, which can improve the interlayer strength and stratification accuracy of printed components.

[0005] In order to achieve the above object, the present invention provides a 3DP printer, comprising:

[0006] A support frame is used to stack the printing material layer by layer along a preset path; a printing platform is used to control the vertical rotation of the print head; the print head includes an extruder and a nozzle, the extruder is used to push the material from the molten state to the nozzle, and the nozzle is used to position the material in the correct position.

[0007] Preferably, the print head comprises a rotating part and a moving part, and the moving part adopts a planar five-bar mechanism and a remote control center mechanism for rotating around a virtual rotation center along the print head.

[0008] Preferably, the moving part adopts a crank slider mechanism to drive the nozzle to approach the frame.

[0009] The present invention also provides a 3D printing method, which specifically comprises the following steps:

[0010] Input the line file in DXF format as a parameter and obtain the starting point and end point of the line through data extraction;

[0011] Discretize a line segment into several point sets, measure the point sets one by one, and reconstruct the line based on the feedback data;

[0012] The feedback data is sent to the control system as the final printing data. The control system drives each stepper motor to work according to the relevant motion instructions received, and completes the printing through three-axis linkage.

[0013] Preferably, the three axes include X-axis, Y-axis and Z-axis mechanisms.

[0014] The present invention provides a 3DP printer and a printing method, which have the following beneficial effects compared with the prior art:

[0015] 1. The three-degree-of-freedom printer can print continuous and uniform circuits on micro-curved surfaces, and can ensure the printing quality while having the advantages of simple operation and low cost.

[0016] 2. The printing method proposed by the present invention can perform differential dispersion according to the curvature size, with high accuracy and greatly reduced calculation amount.

[0017] 3. The present invention defines and separates the upper surface of the model through the angle of the normal vector of the triangular face, and then offsets the model surface multiple times and calculates the intersection line with the side of the model to obtain the layered contour line of the model surface. After the surface layering, the molten material can be extruded along the contour direction of the model surface during the printing process, breaking through the limitation that the molten material can only be stacked in a two-dimensional plane in the common plane layering method, and effectively reducing the step effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention provides a flow chart of a printing method. DETAILED DESCRIPTION

[0019] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0020] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0021] All directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, horizontal, vertical...) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0022] Due to installation errors and other reasons, the parallel relationship referred to in the embodiments of the present invention may actually be an approximately parallel relationship, and the vertical relationship may actually be an approximately vertical relationship.

[0023] The present invention provides a 3D printer, which comprises: a frame for supporting, a print head for stacking printing materials layer by layer according to a preset path; a printing platform for controlling the vertical rotation of the print head; the print head comprises an extruder and a nozzle, the extruder is used to push the material from a molten state to the nozzle, and the nozzle is used to position the material in a correct position.

[0024] The 3D printer also includes a control system, which is the "brain" of the 3D printer and is used to process and interpret the G code generated by the CAD software. In this embodiment, the control system adopts an open source Arduino control system, which has good stability and scalability. The print head is a high-temperature print head, which can adapt to the printing needs of various materials. The printing platform adopts a heating platform, which can effectively prevent the print from warping.

[0025] The print head includes a rotating part and a moving part. The moving part adopts a planar five-bar mechanism and a remote control center mechanism, which is used to rotate along the print head around a virtual rotation center. Specifically, the print head rotating part can realize the rotation of the print head around the virtual rotation center based on a planar five-bar mechanism combined with a remote motion center mechanism. The moving part adopts a nozzle close to the frame. Among them, the remote center of motion (RCM) mechanism is used to constrain the motion planning and motion control of the manipulator, and plays an important role in surgical robots, exoskeleton robots, tactile devices, pointing mechanisms, etc., and its end effector moves through a fixed point. Among them, the three axes include X-axis, Y-axis and Z-axis mechanisms.

[0026] like Figure 1 As shown, the present invention also provides a 3D printing method, the specific steps of which include:

[0027] S1: Input the line file in DXF format as a parameter and obtain the starting point and end point of the line through data extraction.

[0028] DXF is a CAD graphic exchange file. Using DXF file as input parameter format can accurately save CAD graphic data. DXF file consists of file segment and terminator mark. File segment is divided into file header segment, class segment, table segment, block segment, entity segment and object segment, a total of 6 segments. Among them, the entity segment stores the relevant parameters of the primitives in the DXF file.

[0029] The steps of analyzing the file entity segment and converting it into G code include:

[0030] Analyze the entity segment of the line segment to determine the line segment type; if the line segment is a straight line, output 1; if it is an arc, output 2 or 3, where 2 means that the circle is drawn from the starting point to the end point in a clockwise direction, and 3 means that the circle is drawn from the starting point to the end point in a counterclockwise direction;

[0031] Get the start point (X0, Y0) and end point (X1, Y1) of the first line segment, and set the start point to the origin (0, 0).

[0032] Compare X0 and X1, Y0 and Y1 respectively, set the smaller point as the origin, and perform coordinate transformation.

[0033] Continue to iterate the above steps.

[0034] Generate data files.

[0035] S2: Discretize a line segment into several point sets, measure the point sets one by one, and reconstruct the line according to the feedback data. The printed line can be divided into straight line segments and curved line segments (mainly arcs). For this reason, the sampling algorithm for straight line segments and curved line segments is studied separately. For straight line segments, consider four cases: horizontal, vertical, positive slope, and negative slope. Taking the case of positive slope as an example, the steps include:

[0036] Determine the starting and ending points of the line segment, and calculate the slope of the line and the length of the line segment in the horizontal direction;

[0037] Divide the line segment into N equal parts, randomly select a point from it, use this point as the horizontal coordinate, and use the general equation of the line to find the coordinates of another point, so that the line segment is discretized uniformly and randomly.

[0038] This method can effectively solve the problem of avoiding periodic errors caused by the processing method on the substrate surface due to uniform sampling, and can also overcome problems such as dense data points caused by random sampling.

[0039] For curve discretization, the equal arc length method is used, that is, a point is collected on the curve within each fixed arc length, and the height information of the substrate surface is measured while ensuring that the curve is not distorted. A relative coordinate system is established with the center of the arc. Then there are 4 cases for the starting point, which are located in 4 quadrants respectively. Similarly, the end point is also located in 4 quadrants and is divided into 5 cases, namely, the other 3 quadrants that are located in the same quadrant as the starting point and above the starting point, the same quadrant as the starting point and below the starting point, and not in the same quadrant as the starting point. Starting from the starting point, the central angle corresponding to the equal arc length is rotated, and the corresponding coordinate information is calculated, so that the circle can be discretized into several points, and finally a G code file for measurement is generated.

[0040] There are two measurement methods: contact measurement and non-contact measurement. Contact measurement may cause probe offset. Based on a discrete point set, in this embodiment, an NPN output laser displacement sensor is selected as a measurement tool. The measurement center distance of the sensor is 30 mm, and the measurement range is -5 ~ 5 mm, so the sensor will be triggered at 30 mm from the substrate surface, completely avoiding contact with the substrate surface or interference motion.

[0041] S3: The feedback data is sent to the control system as the final printing data. The control system drives each stepper motor to work according to the relevant motion instructions received, and completes the printing through three-axis linkage.

[0042] The above sampling strategy is used to measure the generated sampling point file. When the sensor returns a signal, the host computer motherboard will capture the signal and record the current position information of the X-axis, Y-axis and Z-axis, thus completing the model reconstruction. When the measurement is completed, a G-code file that can be directly printed will be output.

[0043] In order to solve the stratification problem in the curved surface printing process, the present invention adopts a hybrid stratification algorithm of regional segmentation, takes advantage of the advantages of plane stratification and surface stratification algorithms, and uses the spatial topological relationship of the STL (STereoLithography) file to quickly identify and extract the curved area surface of the model for offset and segmentation of the three-dimensional model, and performs plane stratification and surface stratification on the sub-models generated by segmentation to achieve hybrid stratification. The steps include:

[0044] Step 1: Data preparation

[0045] The STL file format was defined by 3D Systems in the United States in 1987. It uses small triangular facets to approximate the surface of a three-dimensional solid model. The definition of each triangular facet includes the three-dimensional coordinates of the three vertices of the triangle and their normal vectors.

[0046] Since the topological relationship between triangles is not stored in the STL file, the triangle information needs to be traversed continuously during layering. In order to improve the efficiency of layering, the link relationship between triangles, that is, topological information, needs to be established. The establishment process is as follows: ① Number each triangle; ② Read a triangle, and record the numbers of the triangles adjacent to it by judging whether the remaining triangles and the triangle have two identical vertices; ③ Read the next triangle in sequence, find the numbers of the triangles adjacent to the triangle, and record them. By traversing all triangles and recording the numbers of the triangles adjacent to each triangle, the topological relationship of all triangles can be established.

[0047] Step 2: Surface layering

[0048] (1) Set the number of surface layers and layer thickness, and offset the separated upper surface of the model along the negative axis direction. The number of offsets is the number of surface layers, and the single offset distance is the surface layer thickness.

[0049] (2) The three-dimensional model is segmented using the surface obtained from the last offset, and the three-dimensional model is segmented into a surface layered area and a plane layered area. The surface layered area is obtained after segmentation.

[0050] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

Claims

1. A 3DP printer, characterized in that: include: A frame for supporting a print head for stacking printing materials layer by layer along a preset path; A printing platform for controlling the vertical rotation of the print head; The printing head includes an extruder and a nozzle, wherein the extruder is used to push the material from a molten state to the nozzle, and the nozzle is used to position the material at a correct position.

2. The 3DP printer according to claim 1, characterized in that: The print head comprises a rotating part and a moving part. The moving part adopts a planar five-bar mechanism and a remote control center mechanism and is used for rotating around a virtual rotating center along the print head.

3. The 3DP printer according to claim 2, characterized in that: The moving part adopts a crank slider mechanism to drive the nozzle to approach the frame.

4. A 3D printing method, characterized in that: The specific steps include: Input the line file in DXF format as a parameter and obtain the starting point and end point of the line through data extraction; Discretize a line segment into several point sets, measure the point sets one by one, and reconstruct the line based on the feedback data; The feedback data is sent to the control system as the final printing data. The control system drives each stepper motor to work according to the relevant motion instructions received, and completes the printing through three-axis linkage.

5. The 3DP printer according to claim 4, characterized in that: The three axes include an X-axis, a Y-axis and a Z-axis mechanism.

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