A mechanism for transverse spreading of a prepreg and a method of using the same

Abstract

The application discloses a kind of pre-preg transverse expansion mechanism and its use method, to prevent the transverse deformation of unidirectional pre-preg in one deformation process too large and cause the transverse splitting of unidirectional pre-preg, unidirectional pre-preg will be through a series of arc-shaped roller, gradually opened to target width.Unidirectional pre-preg opening width is determined by the final roller geometry.By the application, unidirectional pre-preg can be transversely expanded to a certain extent to realize variable cross-section width component, and the gap caused by the increase of cross-section width can be compensated, thereby greatly improving the forming quality and forming efficiency of the workpiece.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automated manufacturing of composite materials. BACKGROUND

[0002] Unidirectional prepreg is an intermediate material which is obtained by dipping resin matrix into aligned fiber bundles and then storing after certain treatment. Unidirectional prepreg has become an important intermediate product of fiber reinforced composite material due to its uniform glue content and good consistency of fiber alignment. In the production process of composite material components, unidirectional prepreg is laid on the surface of a mold according to the design angle and sequence of the layers by manual or automatic laying, and then the prepreg is cured to obtain a composite material component meeting the performance requirements.

[0003] In general molding process, a certain tension is usually applied to the unidirectional prepreg along the fiber arrangement direction to avoid wrinkles on the surface of the prepreg and ensure that the arrangement angle of the fiber is the same as the design angle. Based on the performance and distribution characteristics of the fiber and resin in the unidirectional prepreg, the fiber has a very high longitudinal tensile elastic modulus, so it can be considered that the unidirectional prepreg does not deform in the existing molding process.

[0004] Generally, the unidirectional prepreg used in the manual and automatic laying process is a fixed-width unidirectional prepreg obtained by slitting. However, in some components with variable cross-sectional width, such as Z-shaped composite ring frame, gaps or overlaps may occur between adjacent equal-width prepregs due to the change of cross-sectional size. The existence of gaps and overlaps will affect the dimensional accuracy and mechanical properties of the final component. Therefore, the above gaps or overlaps must be treated by adjusting the width of the prepreg or filling. However, due to the poor transverse bonding performance between fibers filled with resin, the tensile deformation of the unidirectional prepreg in the direction perpendicular to the fiber arrangement direction is prone to cause transverse tearing of the prepreg, which is difficult to expand. At present, manual repair is often used for the above gaps or overlaps, which wastes a lot of manpower and time. SUMMARY

[0005] The present application provides a prepreg transverse expansion mechanism, which can realize step-by-step transverse expansion of the prepreg to avoid transverse tearing of the prepreg and compensate for the gaps caused by the increase in the cross-sectional width of the prepreg.

[0006] The present application also provides a use method of the prepreg transverse expansion mechanism, which can realize real-time adjustment of the prepreg expansion process to obtain better expansion effect and repair possible transverse tearing by step-by-step expansion of the prepreg combined with image processing technology.

[0007] Technical solution: To achieve the above-mentioned purpose, the present application provides a kind of pre-impregnated material transverse expansion mechanism, including roller group, driving device and camera;The roller group includes the flat roller located in the most downstream and the arc pair of rollers arranged in order from downstream to upstream;Each level of arc pair of rollers is connected with the driving end of a driving device, and the driving device is used to make the arc pair of rollers rotate;Each level of arc pair of rollers includes the straight line roller section coaxially connected with the driving end of the driving device and the arc roller section extending from the straight line roller section, the arc roller section has the arc surface for contacting with the pre-impregnated material, and the arc surface width of the arc roller section upstream contacting with the pre-impregnated material is greater than the arc surface width of the adjacent downstream arc roller section contacting with the pre-impregnated material;The camera is used to capture the pre-impregnated material image on each level of arc pair of rollers.

[0008] Further, the maximum single expansion transverse strain of each arc roller section relative to the adjacent downstream arc roller section or flat roller on the pre-impregnated material is 1%.

[0009] Further, the flat roller is located at the lowest position of the roller group, and the arc pair of rollers are arranged obliquely upwards in order, and the flat roller and the straight line roller section of each level of arc pair of rollers are arranged in parallel.

[0010] Further, the arc roller section of the arc pair of rollers is a curved equal-width arc structure, when the pre-impregnated material contacts the arc roller section, the arc pair of rollers is turned forward or backward by an angle, and the width of the arc roller section contacting with the pre-impregnated material becomes larger or smaller.

[0011] Beneficial effects: Compared with the prior art, the pre-impregnated material transverse expansion mechanism of the present application can realize the transverse expansion of unidirectional pre-impregnated material to a certain extent to realize the variable cross-section width component, wherein the multi-stage arc pair of rollers is adopted and the pre-impregnated material contacting width with the arc pair of rollers increases gradually, so that the expansion width of each stage of pre-impregnated material is controllable until the desired expansion width is reached upstream, which can compensate the gap caused by the increase of cross-section width on line, and also can avoid the transverse tearing of the pre-impregnated material.

[0012] The present application also provides a use method of the pre-impregnated material transverse expansion mechanism, comprising the following steps:

[0013] (1) determining the number of rollers required for expanding the pre-impregnated material;

[0014] (2) feeding the unidirectional pre-impregnated material to be expanded into the mechanism, first passing through the flat roller for guiding and supporting, the camera records the initial width of the pre-impregnated material and monitors its change in real time;

[0015] (3) through the camera based on robot vision technology observation on the last stage roll prepreg, the camera real-time capture with each level of arc-shaped contact roll prepreg image, through feature extraction algorithm extracts the edge features of prepreg after using pixel distance calculation each with each level of arc-shaped contact roll prepreg actual width of the part; Confirm whether the actual width of the prepreg part contacted with each level of arc-shaped contact roll reaches the width requirement, if it cannot complete the width requirement, then through the driving device to rotate the downstream arc-shaped contact roll, make the prepreg contact amount increase, otherwise, adjust in the opposite direction, reduce the contact amount of the roll;

[0016] (4) through the camera to check whether the prepreg on each level of arc-shaped contact roll appears tearing state, when detecting that the prepreg appears tearing state in the part contacted with a certain level of arc-shaped contact roll, drive the arc-shaped contact roll to rotate to reduce the contact amount of the prepreg.

[0017] Further, when the camera captures the prepreg image, the image is denoised, and the specific formula is as follows:

[0018]

[0019] Where g(i,j) is the pixel value of the denoised image at the coordinate, f(i+m,j+n) is the coordinate value of the original image at the coordinate (i+m,j+n), w(m,n) is the Gaussian weight, which is calculated by the Gaussian function, K is a normalization constant, and the sum of the weights is 1, and S is the neighborhood centered at (i,j).

[0020] Further, in step (3), the actual width of each prepreg part contacted with each level of arc-shaped contact roll is calculated by pixel distance, and the specific formula is as follows:

[0021] The width of the prepreg in the image captured by the camera is W pixel , in pixels; the pixel resolution of the camera is P pixel / mm, that is, the number of pixels per millimeter, so the actual width W real of the prepreg is: real W pixel = W pixel / P pixel / mm.

[0022] Advantages: Compared with the prior art, the use method of the prepreg transverse width expansion mechanism can improve the stability and accuracy of the prepreg width expansion process by combining image processing technology, thereby reducing the need for manual intervention and repair, ensuring the molding quality while greatly improving the molding efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structural schematic view of the prepreg transverse width expansion mechanism in the application;

[0024] Figure 2 This is a schematic diagram of one of the arc-shaped rollers. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0026] Figure 1 and Figure 2 As shown, the prepreg lateral widening mechanism provided in this invention includes a roller group, a drive device 9, and a camera 8.

[0027] The roller assembly includes a downstream flat roller 1 and several stages of arc-shaped rollers arranged sequentially from downstream to upstream (from bottom to top: primary arc-shaped roller 2, secondary arc-shaped roller 3, tertiary arc-shaped roller 4, and quaternary arc-shaped roller 5). Each stage of arc-shaped rollers is connected to the drive end of a drive device 9, which is used to rotate the arc-shaped rollers. In this embodiment, the drive device is a motor. The roller assembly is mounted on the wall panel 7, and the drive device 9 is located on the rear side of the wall panel 7.

[0028] Each stage of the curved rollers includes a straight roller segment coaxially connected to the drive end of the drive unit and a curved roller segment extending from the straight roller segment. The curved roller segment has an arcuate surface for contacting the prepreg. Assuming a prepreg of width L remains constant (let's say L) as it passes through the flat roller 1, and that the prepreg contacts the curved roller segment, as... Figure 2 As shown, under tension, the upper fibers tend to move towards the lower layers. When the tension exceeds a certain value, the upper fibers slide down to the lower layers, resulting in a decrease in the thickness and an increase in the width of the prepreg. The change in transverse width is ΔW = SL, and the transverse strain of the prepreg belt is ε = ΔW / L. Furthermore, the width of the arc surface in contact with the prepreg from the upstream arc-shaped roller segment is greater than the width of the arc surface in contact with the prepreg from the adjacent downstream arc-shaped roller segment. The arc-shaped roller segments of the arc-shaped roller pair are curved, uniformly wide arc structures. When the prepreg contacts the arc-shaped roller segment, after the arc-shaped roller pair rotates clockwise or counterclockwise by an angle, the width of the contact between the arc-shaped roller segment and the prepreg increases or decreases.

[0029] By employing a multi-stage arc-shaped roller system, the transverse deformation of the unidirectional prepreg during a single deformation process can be avoided, which could lead to transverse splitting of the unidirectional prepreg. By using a multi-stage arc-shaped roller system and controlling the rotation angle of each stage of the arc-shaped roller system, the maximum single transverse strain of the prepreg relative to the adjacent downstream arc-shaped roller system or flat roller is 1%, allowing the prepreg to gradually widen to the target width.

[0030] The method of using the above-mentioned prepreg transverse widening mechanism includes the following steps:

[0031] (1) Determine the number of rollers needed to spread the prepreg; by analyzing and calculating the number of rollers needed to spread the prepreg (calculate Lf / L0, if it is 0%-1%, one arc-shaped pair of rollers is needed, if it is 1%-2%, two arc-shaped pair of rollers are needed, and so on), the first few rollers that need to use arc-shaped rollers are set to the maximum height by motor-driven rotation, so that the contact amount of the prepreg passing through the rollers reaches the maximum, that is, the gradual expansion amount is 1%.

[0032] (2) The unidirectional prepreg to be spread is sent into the mechanism, first passing through the flat roller 1 for guiding and supporting, and the camera 8 records the initial width of the prepreg and monitors its changes in real time; if the prepreg deviates or wrinkles during the feeding process, it needs to be adjusted in time to ensure that it can smoothly enter the subsequent arc-shaped pair of rollers for spreading.

[0033] (3) The camera based on robot vision technology observes the prepreg on the last-stage roller, and the camera captures the image of the prepreg contacting each level of arc-shaped pair of rollers in real time. However, due to factors such as material properties, working time, and uneven lighting, noise will be introduced into the image, so image denoising is needed. The specific formula is as follows:

[0034]

[0035] where g(i, j) is the pixel value of the denoised image at the coordinate, f(i+m, j+n) is the coordinate value of the original image at the coordinate (i+m, j+n), w(m, n) is the Gaussian weight calculated by the Gaussian function, K is the normalization constant, and S is the neighborhood centered at (i, j).

[0036] After denoising, the edge features of the prepreg are extracted by a feature extraction algorithm, and the actual width of each part of the prepreg contacting each level of arc-shaped pair of rollers is calculated using pixel distance. The actual width can be calculated using pixel distance: assuming that the width of the prepreg in the image captured by the camera is W pixel (pixels), and the pixel resolution of the camera is P pixel / mm (i.e., the number of pixels per millimeter), then the actual width W real of the prepreg can be represented as: W real = W pixel / P pixel / mm. Confirm whether the actual width of the prepreg contacting each level of arc-shaped pair of rollers meets the spreading requirement. If it cannot meet the spreading requirement, increase the contact amount of the prepreg passing through the rollers by driving the downstream arc-shaped pair of rollers to rotate, and vice versa.

[0037] (4) After the step-by-step widening and visual inspection, the width of the prepreg has approached the target value. However, in order to ensure the final widening accuracy and quality control, a round of fine tuning is still needed: through the camera, the prepreg on each level of arc-shaped roller is checked for tearing state, and when the prepreg on a certain level of arc-shaped roller is detected to have tearing state, the arc-shaped roller is driven to rotate to reduce the contact amount of the prepreg. At the same time, according to the image information captured by the camera, the uppermost arc-shaped roller is fine-tuned to ensure that the width of the widened prepreg meets the design requirements. Repeat the fine-tuning operation in this step until the prepreg on each level of arc-shaped roller does not appear tearing and meets the widening requirements.

[0038] Through the above procedure, the width of the prepreg can be adjusted online, and the prepreg meeting the size requirements of the variable-width cross-section member can be obtained at one time, thereby realizing the full-ply laying of the cross-section variable-width member and ensuring no gap and overlap between adjacent prepregs. The application of robot vision technology also greatly improves the efficiency of the unidirectional prepreg transverse widening mechanism and reduces the cost. Through real-time monitoring and accurate control, the robot vision technology can ensure the stability and accuracy of the widening process, thereby reducing the need for manual intervention and repair, ensuring the molding quality while greatly improving the molding efficiency.

Claims

1. A prepreg transverse spreading mechanism characterized by, The roller group, the driving device and the camera; The roller group comprises a flat roller at the most downstream position and a plurality of stages of arc-shaped pairs of rollers arranged in sequence from downstream to upstream; each stage of arc-shaped pairs of rollers is connected with the driving end of a driving device, and the driving device is used to rotate the arc-shaped pairs of rollers; Each stage of arc-shaped pairs of rollers comprises a straight roller segment coaxially connected with the driving end of the driving device and an arc-shaped roller segment extended from the straight roller segment, the arc-shaped roller segment has an arc surface for contacting the prepreg, and the width of the arc surface of the arc-shaped roller segment at the upstream position for contacting the prepreg is greater than the width of the arc surface of the arc-shaped roller segment at the adjacent downstream position for contacting the prepreg; The camera is used to capture the image of the prepreg on each stage of arc-shaped pairs of rollers; the camera observes the prepreg on the last-stage roller based on the robot vision technology, captures the image of the prepreg contacting each stage of arc-shaped pairs of rollers in real time, extracts the edge features of the prepreg by a feature extraction algorithm, and calculates the actual width of each part of the prepreg contacting each stage of arc-shaped pairs of rollers by pixel distance; It is confirmed whether the actual width of the part of the prepreg contacting each stage of arc-shaped pairs of rollers meets the spreading requirement, if the spreading requirement cannot be met, the arc-shaped pairs of rollers at the downstream position are rotated by the driving device, so that the contact amount of the prepreg passing through the rollers is increased, otherwise, the reverse adjustment is performed to reduce the contact amount of the prepreg passing through the rollers; it is checked by the camera whether the prepreg on each stage of arc-shaped pairs of rollers appears in a tearing state, when it is detected that the part of the prepreg contacting a certain stage of arc-shaped pairs of rollers appears in a tearing state, the arc-shaped pairs of rollers are driven to rotate so as to reduce the contact amount of the prepreg.

2. The apparatus according to claim 1, wherein The maximum single expansion transverse strain of each arc-shaped roller segment to the prepreg relative to the adjacent downstream arc-shaped roller segment or the flat roller is 1%.

3. The apparatus according to claim 1 or 2, wherein The flat roller is located at the lowest position of the roller group, the plurality of stages of arc-shaped pairs of rollers are arranged in sequence in a slanting upward direction, and the flat roller and the straight roller segments of each stage of arc-shaped pairs of rollers are arranged in parallel.

4. The apparatus according to claim 3, wherein The arc-shaped roller segment of the arc-shaped pairs of rollers is a curved equal-width arc-shaped structure, when the prepreg contacts the arc-shaped roller segment, the width of the arc-shaped roller segment for contacting the prepreg is increased or decreased after the arc-shaped pairs of rollers are rotated by an angle.

5. A method of using the mechanism for transverse spreading of a prepreg according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: (1) determining the number of rollers required for spreading the prepreg; (2) feeding the unidirectional prepreg to be spread into the mechanism, first passing through the flat roller for guiding and supporting, recording the initial width of the prepreg by the camera, and monitoring the change of the prepreg in real time; (3) observing the prepreg on the last-stage roller by the camera based on the robot vision technology, capturing the image of the prepreg contacting each stage of arc-shaped pairs of rollers in real time, extracting the edge features of the prepreg by a feature extraction algorithm, and calculating the actual width of each part of the prepreg contacting each stage of arc-shaped pairs of rollers by pixel distance; It is confirmed whether the actual width of the part of the prepreg contacting each stage of arc-shaped pairs of rollers meets the spreading requirement, if the spreading requirement cannot be met, the arc-shaped pairs of rollers at the downstream position are rotated by the driving device, so that the contact amount of the prepreg passing through the rollers is increased, otherwise, the reverse adjustment is performed to reduce the contact amount of the prepreg passing through the rollers; (4) checking by the camera whether the prepreg on each stage of arc-shaped pairs of rollers appears in a tearing state, when it is detected that the part of the prepreg contacting a certain stage of arc-shaped pairs of rollers appears in a tearing state, the arc-shaped pairs of rollers are driven to rotate so as to reduce the contact amount of the prepreg.

6. The method of using a preform transverse width mechanism according to claim 5, wherein, When the camera captures the prepreg image, the image is denoised, and the specific formula is as follows: = ； wherein is the pixel value of the denoised image at coordinates is the coordinate value of the original image at coordinates is the coordinate value of the original image at coordinates is a Gaussian weight, calculated from a Gaussian function, K is a normalization constant such that the sum of the weights is 1, S is a neighborhood centered at is a Gaussian weight, calculated from a Gaussian function, K is a normalization constant such that the sum of the weights is 1, S is a neighborhood centered at 7. The method of using a mechanism for transversely widening a prepreg according to claim 5, wherein, In step (3), the actual width of each prepreg part in contact with each level of arc-shaped counter-roller is calculated by pixel distance, and the specific formula is as follows: The width of the prepreg in the image captured by the camera is W pixel in pixels; the pixel resolution of the camera is P pixel per mm, i.e. the number of pixels per mm, then the actual width of the prepreg W real is expressed as: W real = W pixel / P pixel per mm.

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