A method for improving cutting accuracy of a whole lay-up roller type automatic fiber placement system

Abstract

This invention relates to the field of automated composite material placement technology, and in particular to a method for improving the cutting accuracy of an automated fiber placement system using an integral placement roller. The method considers compensation for the compression of the placement roller and obtains a reference point based on the forward movement distance d from the placement endpoint, with the reference point corresponding to s. i Value replaces the sending of the cutting signal at s i Value, the fiber placement head then runs d-s i A cutting signal is then sent to ensure that the filament bundle is laid precisely at the theoretical termination point. This method effectively solves the problem of insufficient cutting accuracy to meet the laying requirements of workpieces with large curvature and complex shapes.

Description

Technical Field

[0001] This invention relates to the field of automated composite material placement technology, and in particular to a method for improving the cutting accuracy of an overall placement roller-type automated filament placement system. Background Technology

[0002] The automated filament placement system independently feeds and cuts prepreg tows from the yarn rack via a placement head. These tows are then bundled into an adjustable-width prepreg tape under the placement rollers and laid onto the surface of a mold with different curvatures according to a predetermined trajectory. This achieves a tight fit and uniform compression of the laid-up surfaces, completing the molding of complex-shaped composite material workpieces. Composite materials are highly designable, with numerous local reinforcements, delaminations, and even openings in the design. Frequent filament cutting operations are required during placement in these areas. With the continuous improvement of aircraft performance, increasingly stringent requirements are placed on placement quality, making cutting accuracy a crucial indicator affecting placement quality and receiving widespread attention. Existing technologies have systematically studied the impact of factors such as CNC system accuracy, cutter assembly accuracy, cutter edge shape, and differences in resistance between different filament transport channels on cutting accuracy, and can meet the placement requirements of workpieces with small curvatures and gentle shapes.

[0003] The automatic yarn placement head is a highly integrated, compact mechanism with functions including yarn stop, refeeding, cutting, placement, channel cooling, surface heating, and placement quality inspection. The cutting actuator is located in a different position from the placement structure, and the yarn cutting point does not coincide with the placement pressure point. (See attached instruction manual.) Figure 1 As shown, the cutting point after the filament is cut. To the laying and pressing point The filament bundles are laid on the mold by the laying rollers, and the cutting point is... Previously, the yarn bundle stopped in the yarn-laying head under the action of the yarn-stopping mechanism. Furthermore, considering the actuation time of the cutting actuator, to meet cutting accuracy requirements, a cutting command needs to be sent to the cutting actuator in advance for compensation. Currently, the control signal is mostly sent according to the center trajectory displacement or distance, and the yarn-laying head moves to the theoretical stopping position of the yarn bundle. A cutting signal is sent over a certain distance, which is called the compensation distance. Obtaining this compensation distance is crucial to ensuring the cutting accuracy of the wire-laying head. This compensation distance mainly consists of the following two aspects: (a) with the first Taking filament bundles as an example, due to the size limitations of the internal structure of the filament placement head, the cutting instant (when the placement roller moves to...) At the point, the non-movement to the theoretical termination of the filament laying position Prepreg cutting point Distance to laying pressure point length .length With the radius of the laying roller and compression amount It changes with the variations. For a given layup roll, the layup roll radius... To determine the value, but the compression of the laying roller. (b) The time required from the issuance of the cutting signal to the actuation element during wire cutting is related to the laying pressure and the shape of the workpiece. Since the filament cutting is a non-stationary cutting process, the speed of the filament laying head at this time is... During this period, the distance the wire laying head moves is Due to the operating time of the cutting actuator It is a relatively fixed value, which can be obtained through debugging, therefore It is only related to the speed of the filament laying head, and the speed of filament cutting can be preset in advance via a program. Considering both of these factors, a cutting signal is sent to the filament laying stop point. distance for:

[0004]

[0005] However, currently, most layup rollers are integral elastic rollers. During layup, the prepreg tow is bundled into a strip, and under the action of a clamping cylinder, the layup roller deforms under pressure to fit the surface to be laid, meeting the layup requirements of composite-shaped workpieces. For areas with large curvature along the axial direction of the layup roller or areas with abrupt changes in curvature, integral layup rollers are used to accommodate different compression amounts at different positions on different curved surfaces. The differences are significant, with varying distances between the cutting points and laying pressure points of different filament bundles. The difference lies in the failure to recognize the compression of the laying rollers. right The impact of this, or the lack of information on the compressibility of the layup rollers for each prepreg tow before cutting. Therefore, effective methods for reasonable compensation are often found in existing technologies, which mostly employ fixed-value compensation, i.e., using a certain amount of compression. (like =3.5mm) corresponding Perform approximate calculations, along the center trajectory line from Point Upward Distance When the filament laying head moves to the point during the laying process, a cutting signal is sent. However, its cutting accuracy is difficult to meet the laying requirements of workpieces with large curvature and complex shapes. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a method for improving the cutting accuracy of an overall layup roller-type automatic filament placement system, which can effectively solve the problem that the cutting accuracy is insufficient to meet the layup requirements of workpieces with large curvature and complex shapes.

[0007] This invention is achieved by adopting the following technical solution:

[0008] A method for improving the cutting accuracy of an overall lay-up roller-type automatic filament placement system includes the following steps:

[0009] Step S1. Obtain the first i Theoretical filament bundle placement termination point D and the actual cutting signal transmission location G ;

[0010] Step S2. Set the stop point D And projecting onto the center trajectory line to obtain the point The point is obtained by projecting the actual cutting signal transmission position point G onto the center trajectory line. ;

[0011] Step S3. Place the point Move forward a distance along the center trajectory line d To obtain a reference point The reference point At point Before;

[0012] Step S3. Obtain a reference point Compression of laying roller and the i The relative height of the filament bundle relative to the center trajectory line ;

[0013] Step S4. Calculate the first... filament bundle laying roller compression :

[0014] ;

[0015] Step S5. Calculate the reference point To the point distance :

[0016]

[0017] In the formula, r is the radius of the laying roller; This is a distance margin, a minimum allowance reserved for the control system. Processing time;

[0018] Step S6. During the laying process, the yarn layup head reaches the point... Then, move along the central trajectory line. Run to point A cutting signal is sent to the cutting actuator to perform the cutting operation.

[0019] The Values ​​and running speed v They are positively correlated.

[0020] The Take 1-3mm.

[0021] The distance traveled d The calculation method is as follows:

[0022]

[0023] in, For the first i filament bundle laying roller compression When it is 0 The For the first i Send a cutting signal to the fiber bundle laying stop point The distance.

[0024] The The calculation method is as follows:

[0025]

[0026]

[0027] In the formula, v The speed at which the wire-laying head moves during the cutting process. t To cut the actuation time of the actuator, e The actuation time of the cutting actuator and the distance the wire-laying head moves; A The point where the filament is cut. B The cutting point between the filament bundle and the laying roller. C Points for laying the silk bundles. P For laying pressure points, r The radius of the laying roller. For the first Compression of the filament bundle layup roller For the first Wire bundle cutting point The corresponding laying pressure point when the laying roller is not compressed The length.

[0028] Step S5 specifically refers to:

[0029]

[0030]

[0031]

[0032] Therefore,

[0033] In the formula, For the first Compression of the filament bundle layup roller For point Move forward a distance along the center trajectory line. For the first Send a cutting signal to the fiber bundle laying stop point distance, For the first filament bundle laying roller compression When it is 0 , for and difference; The point where the filament is cut. The cutting point between the filament bundle and the laying roller. Points for laying the silk bundles. For laying pressure points, This refers to the laying pressure point when the laying roller is not compressed; The radius of the laying roller. This is the distance margin. For the first Wire bundle cutting point The corresponding laying pressure point when the laying roller is not compressed Length, For the first filament bundle laying roller compression When it is 0, the corresponding value.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. This invention proposes a method to improve cutting accuracy by studying the relationship between the compression amount of the laying roller and the compensation distance at a certain point. It improves the cutting accuracy and laying quality of workpieces with large curvature changes along the axial direction of the laying roller and complex shapes. Taking the maximum deformation of the compression roller of 6mm and the radius of the laying roller of 35mm as an example, the laying accuracy is improved by ±0.8mm compared with the prior art.

[0036] 2. This invention proposes an integrated layup roller-type automatic filament placement system with a layup roller compression amount. For compensation distance It has a significant impact, and the following conclusions have been drawn. and , The correspondence between them, and by moving forward a distance based on the laying stop point. Obtain a new location point, corresponding to that point Value replaces the sending of the cutting signal Value, the fiber placement head restarts A cutting signal is then sent to ensure that the filament bundle is laid exactly at the theoretical termination point.

[0037] 3. Through this invention, the position corresponding to the location can be obtained before the fiber placement head moves along the center trajectory line to that position. The value is used by the wire-laying head control system for processing, judgment, and sending control commands; the cutting signal is sent at the corresponding position. Value and distance from the point at that location Equal distance 。 Attached Figure Description

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, wherein:

[0039] Figure 1 This is a schematic diagram of the filament bundle laying during cutting in this invention;

[0040] Figure 2 This is a schematic diagram of the operation state of the laying roller in this invention.

[0041] Figure 3 for Figure 2 Sectional view of AA;

[0042] Figure 4 This is a cross-sectional view of an embodiment of the concave curved surface in this invention;

[0043] Figure 5 This is a cross-sectional view of an embodiment of the present invention with a central boss;

[0044] Marked in the image:

[0045] 1. No. 1. Fiber bundle; 2. Mold; 3. Cutting actuator; 4. Laying roller; 5. Center trajectory line. Detailed Implementation

[0046] Example 1

[0047] As a basic embodiment of the present invention, the present invention includes a method for improving the cutting accuracy of an overall layup roller type automatic filament placement system, comprising the following steps:

[0048] Step S1. Obtain the first i Theoretical layup termination point of filament bundle 1 D and the actual cutting signal transmission location G .

[0049] Step S2. Set the stop point D Projecting the points onto the center trajectory line 5 yields the points. The actual cutting signal transmission point G is projected onto the center trajectory line 5 to obtain the point. .

[0050] Step S3. Place the point Move forward a distance d along the central trajectory line 5 to obtain the reference point. The reference point At point Before.

[0051] Step S3. Obtain a reference point Compression of laying roller and the The relative height of filament bundle 1 relative to the center trajectory line 5 .

[0052] Step S4. Calculate the first... filament bundle 1 laying roller compression amount :

[0053] .

[0054] Step S5. Calculate the reference point To the point distance :

[0055]

[0056] In the formula, r is the radius of the laying roller 4; This is a distance margin, a minimum allowance reserved for the control system. Processing time.

[0057] Step S6. During the laying process, the yarn layup head reaches the point... Then, move along the central trajectory line 5. Run to point A cutting signal is sent to the cutting actuator 3 to perform the cutting operation.

[0058] Example 2

[0059] In a preferred embodiment of the present invention, the present invention includes a method for improving the cutting accuracy of an overall layup roller type automatic filament placement system, comprising the following steps:

[0060] Step S1. Obtain the first i Theoretical layup termination point of filament bundle 1 D and the actual cutting signal transmission location G .

[0061] Step S2. Set the stop point D Projecting the points onto the center trajectory line 5 yields the points. The actual cutting signal transmission point G is projected onto the center trajectory to obtain the point. .

[0062] Step S3. Place the point Move forward a distance d along the central trajectory line 5 to obtain the reference point. The reference point At point Before.

[0063] The method for calculating the moving distance d is as follows:

[0064]

[0065] in, For the first filament bundle 1 laying roller compression amount When it is 0 The For the first Wire bundle 1 sends a cutting signal to the wire bundle laying stop point The distance. This is a distance margin, a minimum allowance reserved for the control system. Processing time.

[0066] Step S3. Obtain points The reference point is obtained from the displacement sensor on the cylinder at the position of the wire laying head. Compression of laying roller The first result is obtained by combining the workpiece shape and the orientation of the wire laying head. The relative height of filament bundle 1 relative to the center trajectory line 5 .

[0067] Step S4. Calculate the first... filament bundle 1 laying roller compression amount :

[0068] .

[0069] Step S5. Calculate the reference point To the point distance :

[0070]

[0071] In the formula, r is the radius of the laying roller 4; This is a distance margin, a minimum allowance reserved for the control system. Processing time.

[0072] Step S6. During the laying process, the yarn layup head reaches the point... Then, move along the central trajectory line 5. Run to point A cutting signal is sent to the cutting actuator 3 to perform the cutting operation.

[0073] Example 3

[0074] As the preferred embodiment of the present invention, the present invention includes a method for improving the cutting accuracy of an overall laying roller automatic filament laying system, which improves the filament laying accuracy by ±0.8mm compared with the prior art.

[0075] In the prior art, refer to the appendix to the specification. Figure 1 , No. Wire bundle 1 cutting point Distance to laying pressure point length The calculation method is as follows:

[0076] (1)

[0077] In the formula, The point where the filament is cut. The four tangent points between the filament bundle and the laying roller are: Points for laying the silk bundles. For laying pressure points, For the radius of the laying roller 4, For the first Compression of the filament bundle 1 laying roller.

[0078] When the laying roller 4 is not deformed, i.e., the compression amount When it is 0, Point and Point coincidence, cutting point Distance to laying pressure point Length is denoted as Obviously It is only related to the structure of the filament placement head and is a fixed value. .

[0079] Will and The difference is denoted as , It can visually reflect the compression amount of the laying roller. right The impact. The calculation method is as follows:

[0080] (2)

[0081] Correspondingly, compression amount When it is 0, at this time Recorded as If the wire-laying head moves at the same speed during cutting, The specific derivation process is as follows:

[0082] (3)

[0083] The geometric meaning of is half the difference between the arc length and the chord length, and the greater the chord height, the greater the difference. Since the above formula is... Regarding the radius of the laying roller 4 and the compression amount of the laying roller Nonlinear functions are not easily reflected intuitively. right The impact of this. Considering the process requirements of the laying rollers, which require a compression of 6mm and a maximum laying speed of 48m / min, the radius of the laying rollers is 4. Most are designed to be 35mm. Table 1 below calculates the compression amount of different laying rollers. corresponding As shown in Table 1 below, when the compression amount When it is 6mm, It is 1.6mm, which is due to the compression amount. When fluctuating between 0 and 6 mm There will be a length fluctuation of 1.6mm. If the fixed value compensation method is used, it will result in a maximum deviation of ±0.8mm.

[0084] Table 1 Compression of different layup rollers corresponding ( =35mm)

[0085]

[0086] Based on this, this embodiment proposes a method to improve the cutting accuracy of the overall layup roller automatic filament placement system, taking into account compensation for the compression of the layup roller.

[0087] Refer to the instruction manual appendix Figure 2 Included with instruction manual Figure 3 The attached diagram is a schematic representation of the placement of a complex workpiece with high curvature. (Instruction manual attached.) Figure 2 The lay-up roller 4 on the middle lay-up head advances tangentially along the central trajectory line 5. The compression direction of the lay-up roller 4 is the normal direction of the central trajectory line 5, and the axial direction of the lay-up roller 4 is perpendicular to both the tangential and normal directions of the central trajectory line 5. Wire bundle 1 is parallel to the center trajectory line 5, the first Points on the filament bundle 1 are projected along the axial direction of the filament placement roller onto the central trajectory line 5. When the filament placement head reaches the corresponding projection point, the relevant operation is performed. When the filament placement head reaches the respective points... , , At that time, the first The filament bundles 1 are laid out at points respectively. , , .

[0088] The displacement sensor on the clamping cylinder of the yarn laying head can acquire the compression amount of the laying rollers at five points along the center trajectory line in real time. Refer to the instruction manual appendix Figure 3 The first result can be obtained by the orientation of the wire laying head and the shape of the workpiece. The height of the normal vector of filament bundle 1 relative to the center trajectory line 5 。 On point Below reference point hour, Negative values, otherwise It is a positive value. (The...) filament bundle 1 laying roller compression amount : Furthermore, this is combined with the program-set wire-laying head running speed. The actuation time of the cutting actuator 3 obtained through debugging is: .

[0089] And send the cutting signal to the end point of the filament laying. distance for:

[0090] (4)

[0091] Substituting the above data into formulas (1) and (4), the distance from the actual stop laying position of the wire bundle at the point where the cutting signal is sent can be calculated. Therefore, the number can be obtained in real time. The corresponding position of the filament bundle 1 , value.

[0092] However, in order to ensure sufficiently high cutting accuracy, the following two technical conditions must be met: (a) The corresponding position must be obtained before the wire placement head moves along the center trajectory line 5 to that position. (a) Values ​​for processing, judgment, and sending control commands by the wire-laying head control system; (b) The position corresponding to the cutting signal transmission position. Value and distance from the point at that location Equal distance 。

[0093] As per the instruction manual Figure 2 As shown, in order to meet the technical condition (a) mentioned above, the position corresponding to the fiber placement head reaching a certain position needs to be obtained in advance. The value used in this embodiment is the value corresponding to the point immediately preceding the current position. Replacement is performed. The specific procedure is as follows: place the filament bundle at the termination point. Move forward a certain distance along the central trajectory line 5 Get points ,point At the actual cutting signal transmission location Before and as close as possible .

[0094] The determination method is as follows: when When it is 0, There is a maximum value, at which point , i.e., point The maximum corresponding to the location Value Due to the point It should be before the theoretically cut signal transmission position, therefore ,Pick . This is a distance margin, a minimum allowance reserved for the control system. The processing time. Due to the high speed of the fiber placement head, the automatic fiber placement control system requires a certain amount of calculation time, and the point... It is recommended to be as close as possible to the theoretical cut signal transmission position. Take 1-3mm. When the running speed... When it is large, Take the larger value; when the running speed When smaller, Take the smaller value.

[0095] To satisfy technical condition (b) above, so that point Distance point Distance equals Place Value. (Based on points) The posture of the wire laying head and the first obtained from the location Top point of strip bundle 1 corresponding Value replaces point The posture of the silk thread laying head is as good as the first Top point of strip bundle 1 corresponding The wire-laying head follows the center trajectory line 5 from... Point movement Run to When the time is right, a cutting signal is sent to the execution structure to perform the cutting operation. This ensures that the cutting signal is sent at the correct position. Value and distance from the point at that location The distances are equal. Combining formulas (2) and (3), The solution process is as follows:

[0096] (5)

[0097] Based on this, a method for improving the cutting accuracy of an overall layup roller-type automatic filament placement system in this embodiment includes the following steps:

[0098] Step S1. Obtain the first i Theoretical layup termination point of filament bundle 1 D and the actual cutting signal transmission location G .

[0099] Step S2. Set the stop point D Projecting the points onto the center trajectory line 5 yields the points. The actual cutting signal transmission point G is projected onto the center trajectory line 5 to obtain the point. .

[0100] Step S3. Place the point Move forward a distance d along the central trajectory line 5 to obtain the reference point. The reference point At point Before.

[0101] The specific calculation method for the moving distance d is as follows: based on the size of the wire placement head and the wire placement head speed set in the program at the moment of cutting. 3. Cutting actuator actuation time Solve According to speed For values The distance traveled is obtained by solving the problem. .

[0102] Step S3. Obtain points The reference point is obtained from the displacement sensor on the cylinder at the position of the wire laying head. Compression of laying roller The first result is obtained by combining the workpiece shape and the orientation of the wire laying head. The relative height of filament bundle 1 relative to the center trajectory line 5 .

[0103] Step S4. According to Calculate the first filament bundle 1 laying roller compression amount .

[0104] Step S5. , Substitute into equation (5) to solve for the reference point. To the point distance .

[0105] Step S6. During the laying process, the yarn layup head reaches the point... Then, move along the central trajectory line 5. Run to point A cutting signal is sent to the cutting actuator 3 to perform the cutting operation.

[0106] Example 4

[0107] As another preferred embodiment of the present invention, please refer to the appendix to the specification. Figure 4 The filament bundles are laid onto mold 2 under the action of the layup roller 4. Mold 2 has a concave curved surface along the axial direction of the layup roller 4, with a radius R of 650 mm. The layup head can lay up to 16 filament bundles simultaneously, with a bundle width of 6.35 mm. Under the action of the clamping cylinder, the compression amount of the layup roller 4 at the center trajectory line 5 is... 2mm, laying roller radius 4 It is 35mm. The value is 2mm. If there is a cutting requirement for the workpiece near this location, the corresponding value for each wire bundle can be calculated. Different filament bundles correspond to As shown in Table 2 below.

[0108] Table 2. Corresponding to different filament bundles ( =35mm =2mm)

[0109]

[0110] Example 5

[0111] As another preferred embodiment of the present invention, please refer to the appendix to the specification. Figure 5 The filament bundles are laid onto mold 2 under the action of the layup rollers. Mold 2 has a step in the middle along the axial direction of the layup rollers 4, with a step height of 3mm. The layup head can lay up to 16 filament bundles simultaneously, with a bundle width of 6.35mm. Under the action of the clamping cylinder, the compression of the layup rollers at the center trajectory line 5 is... The thickness is 5mm, and the radius of the laying roller is 4. It is 35mm. The value is 2mm. If there is a cutting requirement for the workpiece near this location, the corresponding value for each wire bundle can be calculated. Different filament bundles correspond to As shown in Table 3 below.

[0112] Table 3. Corresponding to different filament bundles ( =35mm =2mm)

[0113]

[0114] In summary, any other corresponding modifications made by those skilled in the art after reading this invention document, without requiring creative mental effort, based on the technical solutions and concepts of this invention, are all within the scope of protection of this invention.

Claims

1. A method of improving the cutting accuracy of a whole-mat deposition roller automated fiber placement system, the method comprising: Includes the following steps: ​ Step S1. Acquire the first i Theoretical lay-off point of the tows (1) D And actual cutting signal sending position point G ; Step S2. Project the point of discontinuity D and the center trajectory line (5) to obtain a point Project the actual cutting signal sending position point G to the center trajectory line (5) to obtain a point ; Step S3. Place the point Move forward a distance d along the central trajectory line (5) to obtain the reference point. The reference point At point Before; Step S3. Obtain a reference point Compression of laying roller and the The relative height of the filament bundle (1) relative to the center trajectory line (5) ; Step S4. Calculate the first... filament bundle (1) Compression amount of laying roller : ； Step S5. Calculate the reference point To the point distance : In the formula, r is the radius of the laying roller (4); This is a distance margin, a minimum allowance reserved for the control system. Processing time; Step S6. During the laying process, the yarn layup head reaches the point... Then, move along the central trajectory line (5). Run to point The cutting signal is sent to the cutting actuator (3) to perform the cutting operation; The method for calculating the moving distance d is as follows: in, For the first filament bundle (1) Compression amount of laying roller When it is 0 The For the first The filament bundle (1) sends a cutting signal to the filament bundle laying stop point. The distance; The value of is positively correlated with the running speed v.

2. The method for improving the cutting accuracy of an overall lay-up roller-type automatic filament placement system according to claim 1, characterized in that: The Take 1-3mm.

3. The method for improving the cutting accuracy of an overall lay-up roller-type automatic filament placement system according to claim 2, characterized in that: The The calculation method is as follows: In the formula, The speed at which the wire-laying head moves during the cutting process. To cut the actuation time of the actuator (3), The time required for the structure to actuate is the distance the filament-laying head moves. The point where the filament is cut. The point of contact between the filament bundle and the laying roller (4) is the point of contact. Points for laying the silk bundles. For laying pressure points, The radius of the laying roller (4) is... For the first The compression amount of the filament bundle (1) lay-up roller. For the first Wire bundle (1) cutting point The corresponding laying pressure point when the distance from the laying roller (4) is not compressed The length.

4. A method for improving the cutting accuracy of an overall lay-up roller-type automatic filament placement system according to claim 3, characterized in that: Step S5 specifically refers to: Therefore, In the formula, For the first The compression amount of the filament bundle (1) lay-up roller. For point Move forward a distance along the central trajectory line (5), For the first The filament bundle (1) sends a cutting signal to the filament bundle laying stop point. distance, For the first filament bundle (1) Compression amount of laying roller When it is 0 , for and difference; The point where the filament is cut. The point of contact between the filament bundle and the laying roller (4) is the point of contact. Points for laying the silk bundles. For laying pressure points, This refers to the laying pressure point when the laying roller (4) is not compressed; The radius of the laying roller (4) is... This is the distance margin. For the first Wire bundle (1) cutting point The corresponding laying pressure point when the distance from the laying roller (4) is not compressed Length, For the first filament bundle (1) Compression amount of laying roller When it is 0, the corresponding value.

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