Prepreg transverse widening mechanism and using method thereof

Abstract

The invention discloses a prepreg transverse broadening mechanism and a use method thereof, and aims to prevent transverse splitting of one-way prepreg caused by overlarge transverse deformation of the one-way prepreg in a one-time deformation process, and the one-way prepreg is gradually expanded to a target width through a series of arc-shaped paired rollers. And the unfolding width of the unidirectional prepreg is determined by the final geometric dimension of the roller pair. According to the invention, transverse broadening of the unidirectional prepreg to a certain extent can be realized, so that a variable cross-section width component is realized, gaps generated due to increase of the cross-section width can be compensated, and the forming quality and the forming efficiency of a workpiece are greatly improved.

Description

Technical Field

[0001] The invention relates to the field of automated manufacturing of composite materials. Background Art

[0002] Unidirectional prepreg is an intermediate material that is made by impregnating directional fiber bundles with a resin matrix and storing them for future use after certain treatment. Due to its uniform glue content and good consistency in fiber arrangement direction, unidirectional prepreg has become an important intermediate product of fiber-reinforced composite materials. In the production process of composite components, prepreg is laid on the mold surface according to the layer design angle and design sequence by manual or automatic laying, forming a preform, and then the preform is cured, and finally a composite component that meets the performance requirements can be prepared.

[0003] In general molding processes, a certain tension is usually applied to unidirectional prepreg along the fiber arrangement direction to avoid wrinkles on the prepreg surface and ensure that the fiber arrangement angle is the same as the designed angle. Based on the properties and distribution characteristics of the fibers and resins in the unidirectional prepreg, it can be known that the fibers have a very high longitudinal tensile elastic modulus, so it can be approximately considered that the unidirectional prepreg tape will not deform in the existing molding process.

[0004] In general, the unidirectional prepreg tapes used in manual and automatic placement processes are all unidirectional prepreg tapes of fixed width obtained by slitting. However, in some components with variable cross-sectional widths, such as Z-shaped composite ring frames, gaps or overlaps often occur between adjacent equal-width prepreg tapes due to changes in cross-sectional dimensions. The existence of gaps and overlaps will affect the dimensional accuracy and mechanical properties of the final components. Therefore, the above gaps or overlaps must be processed by adjusting the width of the prepreg or filling them. However, since the fibers are filled with resin and have poor lateral bonding performance, the tensile deformation of the unidirectional prepreg in the direction perpendicular to the fiber arrangement direction can easily cause lateral tearing of the prepreg, making it difficult to unfold. At present, the above gaps or overlaps are often repaired manually, wasting a lot of manpower and time. Summary of the invention

[0005] Purpose of the invention: The present invention provides a prepreg lateral widening mechanism, the purpose of which is to achieve step-by-step lateral widening of the prepreg to avoid lateral tearing of the prepreg and to compensate for the gap caused by the increase in the cross-sectional width of the prepreg.

[0006] The present invention also provides a method for using the prepreg transverse widening mechanism, the purpose of which is to widen the prepreg step by step and combine it with image processing technology to adjust the prepreg widening process in real time to obtain a better widening effect and to repair possible transverse tearing.

[0007] Technical solution: To achieve the above-mentioned purpose, the present invention provides a prepreg lateral widening mechanism, including a roller group, a driving device and a camera; the roller group includes a flat roller located at the most downstream and a plurality of arc-shaped roller pairs arranged in sequence from downstream to upstream; each arc-shaped roller pair is connected to a driving end of a driving device, and the driving device is used to rotate the arc-shaped roller pair; each arc-shaped roller pair includes a straight roller segment coaxially connected to the driving end of the driving device and an arc-shaped roller segment extending from the straight roller segment, the arc-shaped roller segment having an arc surface for contacting the prepreg, and the width of the arc surface of the upstream arc-shaped roller segment in contact with the prepreg is greater than the width of the arc surface of the adjacent downstream arc-shaped roller segment in contact with the prepreg; the camera is used to capture the image of the prepreg on each arc-shaped roller pair.

[0008] Furthermore, the maximum single unfolding transverse strain of the prepreg by each arc-shaped roller segment relative to the adjacent downstream arc-shaped roller segment or flat roller is 1%.

[0009] Furthermore, the flat roller is located at the lowest position of the roller group, and several levels of arc-shaped roller pairs are arranged obliquely upward in sequence, and the straight roller segments of the flat roller and each level of arc-shaped roller pairs are arranged in parallel.

[0010] Furthermore, the arc roller segment of the arc roller is a curved equal-width arc structure. When the prepreg contacts the arc roller segment, the width of the arc roller segment in contact with the prepreg increases or decreases after the arc roller rotates forward or reversely by an angle.

[0011] Beneficial effect: Compared with the prior art, the prepreg lateral widening mechanism of the present invention can achieve lateral widening of unidirectional prepreg to a certain extent, so as to realize variable cross-sectional width components, wherein a multi-stage arc-shaped roller pair is adopted and the contact width between the prepreg and the arc-shaped roller pair is increased step by step, so that the widening width of each stage of the prepreg can be controlled until the expected widening width is reached upstream, which can not only perform online compensation for the gap caused by the increase in cross-sectional width, but also avoid lateral tearing of the prepreg.

[0012] The present invention also provides a method for using the prepreg lateral widening mechanism, comprising the following steps:

[0013] (1) Determine the number of rollers required to widen the prepreg;

[0014] (2) The unidirectional prepreg to be widened is fed into the mechanism and first guided and supported by a flat roller. The camera records the initial width of the prepreg and monitors its changes in real time;

[0015] (3) The prepreg on the final roller is observed by a camera based on robot vision technology. The camera captures the image of the prepreg in contact with each arc roller in real time. After the edge features of the prepreg are extracted by a feature extraction algorithm, the actual width of each prepreg portion in contact with each arc roller is calculated using pixel distance. It is confirmed whether the actual width of the prepreg portion in contact with each arc roller meets the widening requirement. If the widening requirement cannot be met, the downstream arc roller is rotated by a driving device to increase the contact amount of the prepreg over the roller. Otherwise, the reverse adjustment is performed to reduce the contact amount of the roller.

[0016] (4) Checking by camera whether the prepreg on each level of arc roller is torn. When it is detected that the prepreg is torn at the part in contact with the arc roller at a certain level, drive the arc roller to rotate so that the arc roller reduces the contact amount of the prepreg.

[0017] Furthermore, when the camera captures the prepreg image, the image is denoised. The specific formula is as follows:

[0018]

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

[0020] Furthermore, in step (3), the actual width of each prepreg portion in contact with each level of arc-shaped rollers is calculated using the pixel distance 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, then the actual width of the prepreg W real Expressed as: W real =W pixel / P pixel / mm.

[0022] Beneficial effects: Compared with the prior art, the method of using the prepreg lateral widening mechanism of the present invention can improve the stability and accuracy of the prepreg widening 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 THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the prepreg lateral widening mechanism in the present invention;

[0024] Figure 2 This is a schematic diagram of the structure of one of the arc-shaped roller pairs. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

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

[0027] The roller group includes a flat roller 1 located at the most downstream and a plurality of arc-shaped roller pairs arranged in sequence from downstream to upstream (from bottom to top, the first-stage arc-shaped roller pair 2, the second-stage arc-shaped roller pair 3, the third-stage arc-shaped roller pair 4, and the fourth-stage arc-shaped roller pair 5). Each stage of the arc-shaped roller pair is connected to the driving end of a driving device 9, and the driving device 9 is used to rotate the arc-shaped roller pair. In this embodiment, the driving device is a motor. The roller group is installed on the wall panel 7, and the driving device 9 is placed on the rear side of the wall panel 7.

[0028] Each arc-shaped roller pair includes a straight roller segment coaxially connected to the driving end of the driving device and an arc-shaped roller segment extending from the straight roller segment. The arc-shaped roller segment has an arc surface for contacting the prepreg. Assuming that the width of the prepreg is L when passing through the flat roller 1, the width of the prepreg remains unchanged as L, and when the prepreg contacts the arc-shaped roller segment, Figure 2 As shown, under the action of tension, the upper fibers tend to move toward the bottom layer. When the tension exceeds a certain value, the upper fibers slide toward the lower layer, and the final effect is that the thickness of the prepreg decreases and the width increases. The lateral width change △W=SL, and the lateral strain of the prepreg tape ε=△W / L. And the width of the arc surface where the upstream arc roller segment contacts the prepreg is greater than the width of the arc surface where the adjacent downstream arc roller segment contacts the prepreg. The arc roller segment of the arc roller pair is a curved equal-width arc structure. When the prepreg contacts the arc roller segment, after the arc roller pair rotates forward or reverses an angle, the width of the arc roller segment in contact with the prepreg increases or decreases.

[0029] The use of multi-stage arc rollers can avoid the lateral splitting of the unidirectional prepreg caused by excessive lateral deformation during the primary deformation process. The multi-stage arc rollers are used and the rotation angle of each stage of the arc rollers is controlled so that the maximum single lateral strain of each arc roller segment relative to the adjacent downstream arc roller segment or flat roller is 1%, so that the prepreg is gradually widened to the target width.

[0030] The method for using the above-mentioned prepreg lateral widening mechanism comprises the following steps:

[0031] (1) Determine the number of rollers required for widening the prepreg; by analyzing and calculating the number of rollers required for widening the prepreg (calculating Lf / L0, if it is 0%-1%, then one arc-shaped roller pair is required, if it is 1%-2%, then two arc-shaped roller pairs are required, and so on), the first few stages of rollers that need to be used for the arc-shaped rollers are driven by motors to rotate and set to the maximum height, so that the contact amount of the prepreg over the rollers reaches the maximum, that is, the step-by-step unfolding amount is 1%.

[0032] (2) The unidirectional prepreg to be widened is fed into the mechanism and first guided and supported by the flat roller 1. The camera 8 records the initial width of the prepreg and monitors its changes in real time. If the prepreg is offset or wrinkled during the feeding process, it needs to be adjusted in time to ensure that it can smoothly enter the subsequent arc roller for widening.

[0033] (3) The prepreg on the final roller is observed by a camera based on robot vision technology. The camera captures the image of the prepreg in contact with each arc roller in real time. However, due to factors such as material properties, working time, and uneven lighting, noise will be introduced into the image. Therefore, the image needs to be denoised. The specific formula is as follows:

[0034]

[0035] Where g(i, j) is the pixel value of the denoised image at coordinates, f(i+m, j+n) is the coordinate value of the original image at coordinates (i+m, j+n), w(m, n) is the Gaussian weight calculated by the Gaussian function, K is the normalization constant that makes the sum of the weights 1, and S is the neighborhood centered at (i, j).

[0036] After denoising, the edge features of the prepreg are extracted by the feature extraction algorithm, and the actual width of each prepreg part in contact with each arc roller is calculated using the pixel distance. The actual width can be calculated using the pixel distance: Assume that 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 (i.e. the number of pixels per millimeter), then the actual width of the prepreg W real It can be expressed as: real =W pixel / P pixel / mm. Confirm whether the actual width of the prepreg part in contact with each level of arc rollers meets the widening requirement. If the widening requirement cannot be met, the downstream arc rollers are rotated by the driving device to increase the contact amount of the prepreg over the rollers. Otherwise, reverse adjustment is performed to reduce the contact amount of the rollers.

[0037] (4) After step-by-step widening and visual inspection, the width of the prepreg is close to the target value. However, in order to ensure the final widening accuracy and quality control, a round of fine-tuning is required: the camera is used to check step by step whether the prepreg on each level of the arc roller is torn. When it is detected that the prepreg is torn in the part in contact with a certain level of arc roller, the arc roller is driven to rotate so that the arc roller reduces the contact amount of the prepreg. At the same time, according to the image information captured by the camera, the upstream arc roller is fine-tuned to ensure that the width of the prepreg after widening meets the design requirements. Repeat the fine-tuning operation in this step until the prepreg on each level of the arc roller is not torn and meets the unfolding requirements.

[0038] Through the above program operation, the width of the prepreg tow can be adjusted online, and the prepreg that meets the size requirements of the variable width cross-section component can be obtained at one time, thereby achieving full coverage of the cross-section variable width component, ensuring no gaps and overlaps between adjacent prepregs. The application of robot vision technology has also greatly improved the efficiency of the lateral widening mechanism of unidirectional prepreg and reduced costs. Through real-time monitoring and precise control, 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 lateral widening mechanism, characterized in that: It includes a roller set, a driving device and a camera; The roller group includes a flat roller located at the most downstream and a plurality of arc-shaped roller pairs arranged in sequence from downstream to upstream; each arc-shaped roller pair is connected to a driving end of a driving device, and the driving device is used to rotate the arc-shaped roller pair; Each stage of arc-shaped roller pairs includes a straight roller segment coaxially connected to the driving end of the driving device and an arc-shaped roller segment extending from the straight roller segment, the arc-shaped roller segment having an arc surface for contacting the prepreg, and the width of the arc surface of the upstream arc-shaped roller segment in contact with the prepreg is greater than the width of the arc surface of the adjacent downstream arc-shaped roller segment in contact with the prepreg; The camera is used to capture the image of the prepreg on each stage of the arc-shaped rollers.

2. The prepreg lateral widening mechanism according to claim 1, characterized in that: The maximum single unfolding transverse strain of each arcuate roller segment on the prepreg relative to the adjacent downstream arcuate roller segment or flat roller is 1%.

3. The prepreg lateral widening mechanism according to claim 1 or 2, characterized in that: The flat roller is located at the lowest position of the roller group, and a plurality of arc-shaped roller pairs are arranged obliquely upward in sequence, and the straight roller segments of the flat roller and each arc-shaped roller pair are arranged in parallel.

4. The prepreg lateral widening mechanism according to claim 3, characterized in that: The arc roller segment of the arc roller pair is a curved equal-width arc structure. When the prepreg contacts the arc roller segment, after the arc roller pair rotates forward or reversely by an angle, the width of the arc roller segment in contact with the prepreg becomes larger or smaller.

5. A method for using the prepreg lateral widening mechanism according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Determine the number of rollers required to widen the prepreg; (2) The unidirectional prepreg to be widened is fed into the mechanism and first guided and supported by a flat roller. The camera records the initial width of the prepreg and monitors its changes in real time; (3) The prepreg on the final roller is observed by a camera based on robot vision technology. The camera captures the image of the prepreg in contact with each arc roller in real time. The edge features of the prepreg are extracted by a feature extraction algorithm, and then the actual width of each prepreg portion in contact with each arc roller is calculated using pixel distance. Confirm whether the actual width of the prepreg part in contact with each level of arc rollers meets the widening requirement. If the widening requirement cannot be met, the downstream arc rollers are rotated by the driving device to increase the contact amount of the prepreg over the rollers. Otherwise, reverse adjustment is performed to reduce the contact amount of the rollers. (4) Checking by camera whether the prepreg on each level of arc roller is torn. When it is detected that the prepreg is torn at the part in contact with the arc roller at a certain level, drive the arc roller to rotate so that the arc roller reduces the contact amount of the prepreg.

6. The method for using the prepreg lateral widening mechanism according to claim 5, characterized in that: When the camera captures the prepreg image, the image is denoised using the following formula: Where g(i, j) is the pixel value of the denoised image at coordinates, f(i+m, j+n) is the coordinate value of the original image at coordinates (i+m, j+n), w(m, n) is the Gaussian weight calculated by the Gaussian function, K is the normalization constant that makes the sum of the weights 1, and S is the neighborhood centered at (i, j).

7. The method for using the prepreg lateral widening mechanism according to claim 5, characterized in that: In step (3), the actual width of each prepreg portion in contact with each level of arc-shaped rollers is calculated using the pixel distance 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 / mm, that is, the number of pixels per millimeter, then the actual width of the prepreg W real Expressed as: W real =W pixel / P pixel / mm.

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