A fiber automatic placement method based on differential control of fiber layer thickness

Abstract

The present invention discloses a fiber automatic placement method based on arithmetic control of fiber layer thickness, which relates to the field of composite fiber technology, and includes the steps of: acquiring the information of the number of layers to be placed under arithmetic control of layer thickness according to the target part thickness, the first layer thickness and the intermediate process parameters; acquiring the actual layer thickness increment according to the target part thickness, the first layer thickness and the number of layers to be placed; acquiring the thickness of the last layer according to the first layer thickness, the number of layers to be placed and the actual layer thickness increment; when the thickness of the last layer does not exceed the threshold interval, automatically placing the fiber according to the first layer thickness and the adjusted actual layer thickness increment and the number of layers to be placed. The present invention increases the layer thickness layer by layer in the form of arithmetic increments, takes a single layer thickness as the adjustment amount, does not need to adjust the pressure, and only requires a single height adjustment device, thereby greatly simplifying the structure of the fiber placement head, and at the same time enables the fiber placement head to perform more detailed operations with a smaller volume.

Description

Technical Field

[0001] The invention relates to the technical field of composite fibers, and in particular to an automatic fiber placement method based on arithmetic difference control of fiber layer thickness. Background Art

[0002] Fiber reinforced composite materials have the advantages of light weight, high strength, fatigue resistance, and corrosion resistance. Therefore, this material is widely used in aerospace, energy, transportation, defense and other fields, and its position in the manufacturing industry is also getting higher and higher. Automatic placement in-situ molding is one of the main methods for preparing fiber reinforced composite materials, and the main functional module for realizing this method is the wire placement head assembly.

[0003] At present, the wire laying head assembly of automatic wire laying equipment generally integrates a force-position hybrid control mechanism. The laying process adopts constant pressure control. Through the linkage adjustment between the pressure sensor device and the height adjustment mechanism, the pressure is adjusted by the height adjustment device when the pressure is unstable, so that the pressure returns to a stable state. Although this method can achieve good molding quality, it is difficult to accurately control the thickness of the molded parts, and often requires fine processing later. Summary of the invention

[0004] In order to ensure that the parts obtained by the automatic placement in-situ forming by the fiber placement head have good accuracy consistency, the present invention proposes a fiber automatic placement method based on differential control of fiber layer thickness, comprising the steps of:

[0005] S1: Obtain the first layer thickness and layer thickness threshold range when laying fibers under target bonding requirements by measuring;

[0006] S2: Based on the target part thickness, first layer thickness and intermediate process parameters, the information of the number of layers to be laid is obtained under the condition of equal thickness control;

[0007] S3: Obtaining the actual layer thickness increment according to the target part thickness, the first layer thickness and the number of layers to be laid;

[0008] S4: Obtain the thickness of the last layer according to the thickness of the first layer, the number of laid layers and the actual layer thickness increment, and determine whether the thickness of the last layer exceeds the threshold range. If not, proceed to the next step;

[0009] S5: Automatically place the fibers according to the first layer thickness, the adjusted actual layer thickness increment, and the number of layers to be placed.

[0010] Furthermore, in the step S1, the target bonding requirement is:

[0011] The bonding force between the first layer fiber and the mold at the first layer thickness is greater than the preset bonding force.

[0012] Furthermore, in the step S2, the intermediate process parameters include: expected layer thickness increment, target layer thickness, and target reciprocal layer thickness.

[0013] Furthermore, when the intermediate process parameter is the expected layer thickness increment, the laying layer number information is obtained by solving the following formula:

[0014]

[0015] Where n is the required number of layers, h1 is the thickness of the first layer, d0 is the expected layer thickness increment, and H is the target part thickness.

[0016] Furthermore, when the intermediate process parameter is the target layer thickness, the laying layer number information is obtained by solving the following formula:

[0017]

[0018]

[0019] In the formula, h i is the thickness of target layer i when laying to the i-th layer.

[0020] Furthermore, when the intermediate process parameter is the target inverse layer thickness, the laying layer number information is obtained by solving the following formula:

[0021]

[0022] Where h -i is the layer thickness of the target inverse layer -i when laying to the inverse i-th layer.

[0023] Furthermore, in step S3, the actual layer thickness increment is obtained by the following formula:

[0024]

[0025] Where d is the actual layer thickness increment, n is the number of layers to be laid, H is the target part thickness, and h1 is the first layer thickness.

[0026] Furthermore, in the step S4, when the thickness of the last layer exceeds the threshold range, the following steps are also included:

[0027] S41: When the thickness of the last layer is higher than the upper limit of the threshold interval, the number of laying layers is increased by one and the process returns to step S3;

[0028] S42: When the thickness of the last layer is lower than the lower limit of the threshold range, an error is reported and the process ends.

[0029] Furthermore, the step S5 further includes the following steps:

[0030] S50: Obtain the thickness of each layer according to the thickness of the first layer, the actual thickness increment after adjustment, and the number of laid layers, and determine whether the thickness of the last layer is less than the thickness of the first layer. If so, process the thickness of each layer in reverse order and enter step S5. If not, directly enter step S5.

[0031] Compared with the prior art, the present invention has at least the following beneficial effects:

[0032] (1) The present invention discloses an automatic fiber placement method based on arithmetic control of fiber layer thickness, which increases the layer thickness layer by layer in an arithmetic increment manner, with a single layer thickness as the adjustment amount, and does not require pressure adjustment. Therefore, there is no need to set a pressure adjustment device linked to a height adjustment device on the placement head, and only a single height adjustment device is required. This greatly simplifies the structure of the placement head, reduces costs, and enables the placement head to perform more detailed operations with a smaller volume.

[0033] (2) Since the fiber is automatically laid in the form of increasing layer thickness, although there is no pressure regulating device for pressure adjustment, as the total layer thickness and single layer thickness increase, the bonding force between the layers is also guaranteed under the action of gravity. At the same time, due to the relative reduction of the laying force, the surface of the part can be smoother. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A step diagram of an automatic fiber placement method based on differential control of fiber layer thickness. DETAILED DESCRIPTION

[0035] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0036] Embodiment 1

[0037] When using automatic placement technology to form parts, in order to ensure the constancy of the placement pressure, a force-position hybrid control method is often used to keep the placement pressure constant. That is, during the placement process, the height of the pressure roller is continuously adjusted so that the placement pressure fluctuates within a certain range. This placement method can greatly guarantee the placement quality of the parts, but there are still the following problems: 1. While ensuring the pressure, the layer thickness becomes a passive variable, and it cannot be guaranteed that the thickness of the prepared parts is consistent with expectations; 2. The force-position hybrid control requires the wire placement head to have a pressure measuring device and a height adjustment device, which increases the complexity of the mechanism. In order to solve the problems existing in the above-mentioned prior art, such as Figure 1 As shown, the present invention proposes a fiber automatic placement method based on differential control of fiber layer thickness, comprising the steps of:

[0038] S1: Obtain the first layer thickness and layer thickness threshold range when laying fibers under target bonding requirements by measuring;

[0039] S2: Based on the target part thickness, first layer thickness and intermediate process parameters, the information of the number of layers to be laid is obtained under the condition of equal thickness control;

[0040] S3: Obtaining the actual layer thickness increment according to the target part thickness, the first layer thickness and the number of layers to be laid;

[0041] S4: Obtain the thickness of the last layer according to the thickness of the first layer, the number of layers laid and the actual layer thickness increment, and determine whether the thickness of the last layer exceeds the threshold interval. If the thickness of the last layer is higher than the upper limit of the threshold interval, proceed to step S41; if the thickness of the last layer is lower than the lower limit of the threshold interval, proceed to step S42; if not, proceed to step S50.

[0042] S41: the number of laying layers is increased by one and the process returns to step S3;

[0043] S42: Report an error and end;

[0044] S50: Obtain the thickness of each layer according to the thickness of the first layer, the actual thickness increment after adjustment, and the number of layers laid, and determine whether the thickness of the last layer is less than the thickness of the first layer. If so, process the thickness of each layer in reverse order and then enter step S5. If not, directly enter step S5.

[0045] S5: Automatically place the fibers according to the first layer thickness, the adjusted actual layer thickness increment, and the number of layers to be placed.

[0046] In order to convert the layer thickness into an active change, and based on the experimental discovery that the surface of the part becomes smoother as the layer thickness increases, the present invention proposes an automatic laying idea of ​​equidistantly increasing layer thickness. Based on this idea, an automatic laying scheme under the above steps is proposed. It should be noted that in order to ensure the bonding force between the molded part and the mold, and to avoid the tipping of the part during the laying process due to insufficient bonding force, in the early stage of the experiment, it is necessary to first obtain the first layer thickness and the layer thickness threshold range of the single-layer laying layer through preliminary experiments (the layer thickness that the fiber just cannot bond, and the value can be slightly reduced in actual applications to leave a margin). After obtaining the above necessary safety data, you can officially enter the preliminary data confirmation stage before fiber laying.

[0047] First, according to the intermediate process parameters actually required by the actual customer or product, we need to first determine the number of layers to be laid under the influence of the intermediate parameters. This is because some products have a specific thickness under a certain number of layers to achieve unique performance or functions due to their functions or quality control requirements. Therefore, the number of layers to be laid in the present invention is determined based on actual production needs. Specifically, the intermediate process parameters include the expected layer thickness increment, the target layer total layer thickness, and the target reciprocal layer total layer thickness.

[0048] When the intermediate process parameter is the expected layer thickness increment d0, the calculation method of the laying layer number information n can use the arithmetic progression summation formula:

[0049]

[0050] After simplification, we get:

[0051]

[0052] In the formula, h1 is the thickness of the first layer, H is the target part thickness, and the number of layers n can be obtained by solving it.

[0053] When the intermediate process parameter is the layer thickness h of the target layer i i When the layer thickness increment d0 can be expressed as d0 = (h i -h1) / (i-1), so the laying layer number information is obtained by solving the following formula:

[0054]

[0055] When the intermediate process parameter is the layer thickness h of the target reciprocal layer i -i When the layer thickness increment d0 can be expressed as d0 = (h -i -h1) / (ni), substitute into the equation:

[0056]

[0057] After sorting, we get

[0058]

[0059] The solution can obtain the laying layer number information n.

[0060] It should be noted that the laying layer number information n obtained by the above solution takes a positive root and is rounded down.

[0061] After obtaining the laying layer number information, the actual layer thickness increment can be calculated. The specific formula is:

[0062]

[0063] Where d is the actual layer thickness increment, n is the number of layers to be laid, H is the target part thickness, and h1 is the first layer thickness.

[0064] Since the layer thickness is controlled by arithmetic differences, its thickness will inevitably change as the number of layers increases. In order to avoid the problem of insufficient interlayer adhesion caused by the layer thickness exceeding the threshold range, after obtaining the actual layer thickness increment, it is also necessary to perform a numerical comparison on the thickness of the last layer.

[0065] When the thickness of the last layer is higher than the upper limit of the threshold interval, it means that the thickness of at least one layer exceeds the upper limit of the threshold interval. At this time, the number of paving layers is increased by one and the process returns to step S3 for recalculation.

[0066] When the thickness of the last layer is lower than the lower limit of the threshold range, it means that the target part thickness cannot be achieved, and an error is reported and the process ends.

[0067] Only when the thickness of the last layer is within the threshold range does it indicate that the target part can be manufactured under the incremental control of the layer thickness.

[0068] It should be noted that, since arithmetic control also includes the situation of decreasing layer thickness, and it has been pointed out in the previous article that appropriately reducing the laying pressure and increasing the layer thickness can obtain a smoother part forming effect. Therefore, when the actual calculated thickness of the last layer is less than the thickness of the first layer, it means that the layer thickness is decreasing arithmetic difference. At this time, the layer thickness can be reversed according to actual needs (because the layer thickness is negatively correlated with the pressure, even if the reversed thickness reduces the first layer thickness, its bonding force becomes greater) to ensure that the thickness of the last layer is in a relatively thick state.

[0069] In a specific experiment, the method of the present invention was used to form actual fiber automatic placement parts. The obtained CF / PEEK0° laminate parts had no obvious wire drawing phenomenon in the bending failure section test, and only the tension and compression interface had stratification, indicating that its interlayer bonding performance was good. At the same time, the difference between the laminate part and the target part size did not exceed 0.03mm. Considering the elastic deformation of the fiber prepreg during the placement process and the deformation caused by the cooling process, this error range is relatively good.

[0070] In summary, the present invention describes an automatic fiber placement method based on arithmetic control of fiber layer thickness, which increases the layer thickness layer by layer in the form of arithmetic increments, with a single layer thickness as the adjustment amount, and there is no need to adjust the pressure. Therefore, there is no need to set a pressure adjustment device linked to the height adjustment device on the placement head, only a single height adjustment device is needed. This greatly simplifies the structure of the placement head, reduces costs, and enables the placement head to perform more detailed operations in a smaller volume.

[0071] Since the fiber is automatically laid in the form of increasing layer thickness, although there is no pressure regulating device for pressure adjustment, as the total layer thickness and single layer thickness increase, the adhesion between the layers is guaranteed under the action of gravity. At the same time, due to the relative reduction of the laying force, the surface of the part can be smoother.

[0072] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0073] In addition, in the present invention, descriptions such as "first", "second", "one", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0074] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0075] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A fiber automatic placement method based on differential control of fiber layer thickness, characterized in that: Includes steps: S1: Obtain the first layer thickness and layer thickness threshold range when laying fibers under target bonding requirements by measuring; S2: Based on the target part thickness, first layer thickness and intermediate process parameters, the information of the number of layers to be laid is obtained under the condition of equal thickness control; S3: Obtaining the actual layer thickness increment according to the target part thickness, the first layer thickness and the number of layers to be laid; S4: Obtain the thickness of the last layer according to the thickness of the first layer, the number of layers laid, and the actual layer thickness increment, and determine whether the thickness of the last layer exceeds the threshold range. If so, proceed to step S41 for further adjustment; if not, directly proceed to step S5; S41: When the thickness of the last layer is higher than the upper limit of the threshold interval, the number of laying layers is increased by one and the process returns to step S3; S42: When the thickness of the last layer is lower than the lower limit of the threshold range, an error is reported and the process ends; S5: Automatically place the fibers according to the first layer thickness, the adjusted actual layer thickness increment, and the number of layers to be placed; In the step S1, the target bonding requirement is: The bonding force between the first layer fiber and the mold at the first layer thickness is greater than the preset bonding force; In the step S2, the intermediate process parameters are: expected layer thickness increment or target layer thickness or target reciprocal layer thickness.

2. The method for automatic fiber placement based on differential control of fiber layer thickness according to claim 1, characterized in that: When the intermediate process parameter is the expected layer thickness increment, the laying layer number information is obtained by solving the following formula: Where n is the required number of layers, h1 is the thickness of the first layer, d0 is the expected layer thickness increment, and H is the target part thickness.

3. The method for automatic fiber placement based on differential control of fiber layer thickness according to claim 2, characterized in that: When the intermediate process parameter is the target layer thickness, the laying layer number information is obtained by solving the following formula: In the formula, h i is the thickness of target layer i when laying to the i-th layer.

4. The method for automatic fiber placement based on differential control of fiber layer thickness according to claim 2, characterized in that: When the intermediate process parameter is the target reciprocal layer thickness, the laying layer number information is obtained by solving the following formula: Where h -i is the layer thickness of the target inverse layer -i when laying to the inverse i-th layer.

5. The method for automatic fiber placement based on differential control of fiber layer thickness according to claim 1, characterized in that: In step S3, the actual layer thickness increment is obtained by the following formula: Where d is the actual layer thickness increment, n is the number of layers to be laid, H is the target part thickness, and h1 is the first layer thickness.

6. The method for automatic fiber placement based on differential control of fiber layer thickness according to claim 1, characterized in that: The step S5 also includes the following steps: S50: Obtain the thickness of each layer according to the thickness of the first layer, the actual thickness increment after adjustment, and the number of layers laid, and determine whether the thickness of the last layer is less than the thickness of the first layer. If so, process the thickness of each layer in reverse order and then enter step S5. If not, directly enter step S5. The reverse processing is to swap the thickness of the first layer with the thickness of the last layer, and then obtain the thickness of each layer according to the actual layer thickness increment and the laying layer number information.

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