Continuous fiber 3D printing corner speed reduction method based on corner curvature characteristics

Abstract

The invention discloses a continuous fiber 3D printing corner speed reduction method based on corner curvature characteristics, which comprises the following steps: acquiring a 3D printing model, and setting an advanced speed reduction distance and a delayed speed reduction distance; the dot density on a printing path in the 3D printing model is obtained, and density refinement processing is conducted on the printing path with the dot density smaller than the critical density parameter; whether the path meeting the critical condition is a corner or an arc is judged, and the optimal printing speed corresponding to the corner path is calculated according to the structural parameters of the corner or the arc in combination with a pre-obtained structural parameter and optimal printing speed relational expression; and speed reduction printing is advanced and delayed. The problems of fiber distortion, fiber dislocation, fiber breakage and the like which are usually caused in the existing 3D printing process are solved, the bonding effect of continuous fiber path corners is improved, the effect of a continuous fiber reinforced composite material is fully played, the continuous fiber printing efficiency and quality are improved, and the production cost is reduced. Therefore, the overall mechanical performance of the fiber reinforced composite material component is further improved.

Description

Technical Field

[0001] The invention belongs to the field of material manufacturing and computer technology, relates to 3D printing technology, and specifically relates to a continuous fiber 3D printing corner speed reduction method based on corner curvature characteristics. Background Art

[0002] Fiber-reinforced composite materials have advantages such as high specific strength, high specific modulus and corrosion resistance. They play an important role in realizing lightweight, green and high-performance manufacturing of high-end equipment and are widely used in high-end manufacturing fields such as automobiles and aerospace. Fiber-reinforced composite materials can achieve the regulation of local mechanical properties of composite components through optimization methods of layup design and trajectory planning.

[0003] Compared with traditional continuous fiber reinforced composite manufacturing methods such as compression molding and winding molding, 3D printing, as an emerging manufacturing technology, has the advantages of rapid manufacturing of complex components, good controllability and material saving, which makes it possible to form integrated high-performance composite materials. The rapid development of 3D printing technology is expected to achieve low-cost high-performance composite materials, thereby further expanding the application range of composite materials. However, in the process of continuous fiber 3D printing, defects may occur when the nozzle pulls the continuous fiber to turn.

[0004] In the continuous fiber path turning scenario, the existing 3D printing process usually causes defects such as fiber distortion, fiber dislocation and fiber breakage, which further affects the overall mechanical properties of fiber reinforced composite components. Currently, facing the turning characteristics in the continuous fiber 3D printing path, a fixed value speed reduction method is generally adopted (as long as the path deflection is encountered, printing is performed at a fixed lower speed), which greatly affects the overall printing efficiency. Summary of the invention

[0005] In order to solve the above problems, the present invention discloses a method for reducing the speed at a corner of continuous fiber 3D printing based on the corner curvature characteristics, so as to achieve high-precision and high-quality printing of continuous fibers at the path corners.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for reducing the speed of continuous fiber 3D printing corners based on corner curvature characteristics, comprising the following steps:

[0008] Step 1, obtain the 3D printed model, and set the advance deceleration distance and the delayed deceleration distance;

[0009] Step 2: Obtain the point density on the printing path in the 3D printing model, make a judgment based on a preset critical density parameter, and perform density refinement processing on the printing path with a point density less than the critical density parameter;

[0010] Step 3, collecting printing path data in the 3D printing model and performing critical condition judgment, judging the path that meets the critical condition as a corner or an arc, and calculating the optimal printing speed corresponding to the corner path according to the structural parameters of the corner or arc combined with the pre-obtained structural parameters and the optimal printing speed relationship;

[0011] The process of calculating the optimal printing speed corresponding to the corner path according to the structural parameters of the corner or arc combined with the pre-obtained structural parameters and the optimal printing speed relationship includes:

[0012] Calculate the curvature value at the path corner or arc, and calculate the optimal printing speed through f(k, v). f(k, v) is the corresponding relationship between the curvature value k and the optimal printing speed v established through multiple experiments;

[0013] or

[0014] Record the chord length ratio of the corner / arc in the printing path, obtain the maximum printable speed v1 and the minimum printable speed v2 through the corresponding relationship between the chord length ratio and the speed, calculate the printing speed v3 of any point in the arc = (the degree of the point / π) × the maximum speed v1, and when the calculated printing speed v3 is less than the minimum speed v2, take the minimum speed v2 as the printing speed v; the corresponding relationship between the chord length ratio and the speed is the relationship f(m, v1, v2) between the maximum printable speed v1 and the minimum printable speed v2 corresponding to the chord length ratio m established through multiple experiments;

[0015] Step 4: Print at the optimal printing speed in advance at a distance from the corner n1, and keep printing at the optimal printing speed until the original printing speed is restored at a distance from the corner n2.

[0016] Furthermore, the density refinement process in step 2 includes: performing a point insertion operation in the printing path.

[0017] Furthermore, the process of collecting the printing path data in the 3D printing model and performing critical condition judgment in step 3 includes: reading the continuous discrete points of the printing path one by one, recording the angle between every three consecutive discrete points, and comparing the recorded angle with the critical angle used for speed reduction judgment. If it is less than the critical angle, it means that there is a corner or arc in the printing path.

[0018] Furthermore, the critical angle is 180°.

[0019] Furthermore, the chord length ratio is the ratio of the distance between the starting point and the end point to the distance from the highest point in the corner / arc to the chord length.

[0020] The beneficial effects of the present invention are:

[0021] 1. The method for reducing speed at corners in continuous fiber 3D printing based on corner curvature characteristics provided by the present invention takes curvature and chord length ratio as theoretical calculation basis, and intelligently reduces speed when there are arcs or corners in the continuous fiber path, thereby solving the problems of fiber distortion, fiber dislocation and fiber breakage usually caused by the existing 3D printing process, improving the bonding effect of the corners of the continuous fiber path, giving full play to the effect of continuous fiber reinforced composite materials, improving the efficiency and quality of continuous fiber printing, and further improving the overall mechanical properties of fiber reinforced composite materials components.

[0022] 2. When it is determined that there is a corner, the method of the present invention reduces the printing speed by a certain distance in advance and delays the speed reduction printing, which appropriately expands the speed change area and can ensure the printing quality of the corners or arcs of the continuous fiber path.

[0023] 3. The method of the present invention uses density refinement processing to enable the bending features to be accurately calculated even if they are composed of fewer points, thereby avoiding corner omissions and improving printing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic flow chart of a 3D printing method for reducing printing speed by turning a continuous fiber path provided by the present invention.

[0025] Figure 2 It is a partial schematic diagram of the target workpiece.

[0026] Figure 3 This is a schematic diagram of the printing effect of the target part, with a printing speed of F 4mm / s.

[0027] Figure 4 This is a schematic diagram of the printing effect of the target part, with a printing speed of F 2mm / s.

[0028] Figure 5 This is a schematic diagram of the printing effect of the target part, with a printing speed of F1mm / s.

[0029] Description of reference numerals:

[0030] 1-Continuous fiber path, 2-Path corner. DETAILED DESCRIPTION

[0031] The technical solution provided by the present invention will be described in detail below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to directions in the accompanying drawings, and the words "inside" and "outside" refer to directions toward or away from the geometric center of a specific component, respectively.

[0032] In this example, a 10×10 thin-walled grid with 100 squares (such as Figure 2 As shown in the figure, the target part 1 is taken as the target part 1, in which the square unit cell size is 10×10 mm, the wall thickness is 2 mm, and the printing material used is continuous carbon fiber reinforced polyamide (CCF / PA) composite wire.

[0033] A 3D printing method for reducing printing speed by turning a continuous fiber path provided by the present invention is applied to a target workpiece, and the process is as follows: Figure 1 As shown, the specific steps include:

[0034] Step 1: Obtain the 3D printing model of the target part, and input the advance deceleration distance n1 = 1mm and the delayed deceleration distance n2 = 1mm. The advance deceleration distance n1 and the delayed deceleration distance n2 are setting parameters in this method, and have nothing to do with whether there are corners or arcs in the path. The purpose of setting these two parameters is to appropriately expand the speed change area to ensure the printing quality of the corners or arcs of the continuous fiber path.

[0035] Step 2: When the bending feature is composed of fewer points, the bending feature (curvature / chord length ratio) cannot be accurately calculated. In order to more accurately find the curved path and slow it down, the present invention sets a critical density parameter (in this example, there is only one point under a path length of 1 cm), analyzes the path of the 3D printed model, and determines that the point density in the printing path (the point density is obtained by directly extracting the distance between the path points according to the parameters preset by the slicing software) is 2 points under a path of 10 cm. Since the point density in the current printing path is less than the critical point density, it is necessary to perform density refinement on the path points, that is, inserting points in the printing path to increase the point density and reach the critical density.

[0036] Step 3: Perform critical condition judgment and segmentation on the 3D printing model (i.e. separate the printing path that meets the critical condition from the printing path that does not meet the critical condition) to obtain several sub-printing models. For the printing model that meets the critical condition, calculate the corresponding optimal printing speed according to the curvature or chord length ratio. Specifically, this step includes the following sub-steps:

[0037] (1) Critical condition judgment: First, collect the path data, read the continuous discrete points of the printing path one by one, record the angle of every three continuous discrete points, and compare the recorded angle with the critical angle of deceleration. If it is greater than the critical angle of 180°, there is no need to decelerate and the angle is ignored; if it is less than the critical angle, it means that there is a corner or arc in the printing path, and deceleration is required. Whether the angle of three continuous discrete points is less than the critical angle of 180° is the critical condition set in this example. This condition can be adjusted as needed (for example, multiple sets of adjacent discrete point angles can be used for multiple judgments and verifications), and the critical angle of 180° can also be adjusted as needed.

[0038] (2) Use appropriate methods to calculate the optimal printing speed: In this example, we choose to calculate the curvature. The continuous fiber prints the non-corner area at a speed of 5 mm / s. When the continuous fiber printing path 1 encounters the following Figure 2 After the path turns to corner 2, the curvature value k=0.2 at the path corner is calculated, and the optimal printing speed (2 mm / s) is calculated by f(k, v). The following table 1 is an example of the corresponding table of curvature and optimal printing speed.

[0039]

[0040] Table 1

[0041] f(k, v) is the pre-established correspondence or relationship between the curvature k and the optimal printing speed v. In the early stage, multiple printing experiments should be carried out on the path with corners using different printing speeds, and the curvature of each point in the path and the optimal printing speed should be recorded to establish the correspondence f(k, v) between the curvature k and the optimal printing speed v. During the experiment, the adjustment gradient of the printing speed should be as small as possible to obtain the best result. Experiments should be carried out for various types of corner forms and various types of printing materials, and the corresponding relationship f(k, v) should be established respectively. When calculating the optimal printing speed, the corresponding relationship f(k, v) for the same printing material and the same corner form can be used, and the result is more accurate.

[0042] The chord length ratio can also be calculated to obtain the optimal printing speed: record the distance between the starting point and the end point of the arc in the continuous fiber printing path and the distance from the highest point in the arc to the chord length, and their ratio is recorded as the chord length ratio. In the early stage, multiple printing experiments should be carried out on the path with an arc using different printing speeds, and the chord length ratio of each point in the path and the maximum printable speed and the minimum printable speed should be recorded, so as to establish the corresponding relationship f(m, v1, v2) between the chord length ratio m and the corresponding maximum printable speed v1 and minimum printable speed v2. According to f(m, v1, v2), v1 and v2 corresponding to the chord length ratio can be obtained. Calculate the printing speed v3 of any point in the arc = (the degree of the point / π) × the maximum speed v1, where the degree of the point refers to the angle between the current point and the three points of the starting point and the end point of the arc in the printing path. If the calculated printing speed v3 is less than the minimum speed v2, the minimum speed v2 is taken as the printing speed v, expressed as follows:

[0043]

[0044] In this example, the continuous fiber prints the non-corner area at a speed of 5 mm / s. When the continuous fiber printing path 1 encounters Figure 1After the path turns corner 2, the chord length ratio m=2 at the path corner is calculated, and the corresponding maximum printable speed v1=4mm / s, the minimum printable speed v2=1mm / s. Printing speed v3=(1 / 2)×4=2mm / s.

[0045] Although calculating the optimal printing speed through the chord length ratio is complicated and requires obtaining the maximum printable speed v1 and the minimum printable speed v2 through experiments, it has high accuracy and feasibility.

[0046] Step 4: Tracing back a distance n1 forward and a distance n2 backward, and reducing the printing speed in advance, that is, printing at the optimal printing speed in advance at the distance n1 from the corner, and restoring the original printing speed at the distance n2 from the corner.

[0047] Figure 3 This is a photo of the thin-walled grille printed at F 4mm / s. It can be clearly seen in the figure that the corners are deflected, deviating from the printing path and failing to form a right angle. Figure 4 As shown, by using the 3D printing method of reducing the printing speed by turning the continuous fiber path provided by the present invention, the printing speed is reduced to F 2mm / s, and the grid can be formed into a 90° right angle with excellent right angle quality. It should be noted that this result can be obtained by using the curvature and chord length ratio calculation. Figure 5 As shown in FIG. 1 , after the printing speed is artificially set to a lower value F1 mm / s, the continuous fiber is kinked again, and the quality of the printed corner is reduced. Obviously, the printing effect of the reduced speed method of the present invention is the best.

[0048] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. A method for reducing the speed of continuous fiber 3D printing corners based on corner curvature characteristics, characterized in that: The steps include: Step 1, obtain the 3D printing model, and set the advance deceleration distance and the delayed deceleration distance; Step 2: Obtain the point density on the printing path in the 3D printing model, make a judgment based on a preset critical density parameter, and perform density refinement processing on the printing path with a point density less than the critical density parameter; Step 3, collecting printing path data in the 3D printing model and performing critical condition judgment, judging the path that meets the critical condition as a corner or an arc, and calculating the optimal printing speed corresponding to the corner path according to the structural parameters of the corner or arc combined with the pre-obtained structural parameters and the optimal printing speed relationship; The process of calculating the optimal printing speed corresponding to the corner path according to the structural parameters of the corner or arc combined with the pre-obtained structural parameters and the optimal printing speed relationship includes: Calculate the curvature value at the path corner or arc, and calculate the optimal printing speed through f(k, v), where f(k, v) is the corresponding relationship between the curvature value k and the optimal printing speed v established through multiple experiments; or Record the chord length ratio of the corner / arc in the printing path, obtain the maximum printable speed v1 and the minimum printable speed v2 through the corresponding relationship between the chord length ratio and the speed, calculate the printing speed v3 of any point in the arc = (the degree of the point / π) × the maximum speed v1, and when the calculated printing speed v3 is less than the minimum speed v2, take the minimum speed v2 as the printing speed v; the corresponding relationship between the chord length ratio and the speed is the relationship f(m, v1, v2) between the maximum printable speed v1 and the minimum printable speed v2 corresponding to the chord length ratio m established through multiple experiments; Step 4: Print at the optimal printing speed in advance at a distance from the corner n1, and keep printing at the optimal printing speed until the original printing speed is restored at a distance from the corner n2.

2. The method for reducing the speed at a corner of continuous fiber 3D printing based on the corner curvature feature according to claim 1, characterized in that: The density refinement process in step 2 includes: performing a point insertion operation in the printing path.

3. According to the method for reducing the speed of continuous fiber 3D printing corners based on corner curvature characteristics according to claim 1, the process of collecting the printing path data in the 3D printing model and performing critical condition judgment in step 3 comprises: The continuous discrete points of the printing path are read one by one, and the angle between every three continuous discrete points is recorded. The recorded angle is compared with the critical angle used for speed reduction judgment. If it is less than the critical angle, it means that there is a corner or arc in the printing path.

4. According to the method for reducing the speed at a corner of continuous fiber 3D printing based on the corner curvature feature of claim 1, the critical angle is 180°.

5. According to the method for reducing the speed at a corner of continuous fiber 3D printing based on the corner curvature feature of claim 1, the chord length ratio is the ratio of the distance between the starting point and the end point to the distance from the highest point in the corner / arc to the chord length.

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