Constant temperature control curved surface fiber laying method and system

Abstract

The invention belongs to the related technical field of composite material additive manufacturing, and discloses a constant temperature control curved surface fiber laying method and system, and the method comprises the steps: carrying out the real-time heating of a laying part in the automatic fiber laying process, and carrying out the real-time monitoring to obtain a measurement temperature value of the laying part; the measured temperature value is corrected according to the deviation relation between the actual heating temperature when the laying part is the curved surface and the theoretical heating temperature when the laying part is equivalent to the plane, and the corrected actual temperature value is obtained; according to the real temperature value and a preset target temperature value, the power of the heating module is adjusted to achieve constant temperature control in the fiber laying process. The laying temperature constant control method is provided in the automatic fiber laying process, the problem that the laying temperature is unstable in the acceleration and deceleration process of a motion executing mechanism is solved, temperature constancy in the whole automatic fiber laying process is achieved, and the forming quality and consistency of automatic laying forming of complex curved surface parts are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to composite material additive manufacturing, and more specifically, relates to a constant temperature controlled curved surface fiber placement method and system. Background Art

[0002] Continuous fiber reinforced thermoplastic composites have the characteristics of high specific strength, good heat resistance, repairability, and green and low carbon, and are widely used in high-end fields such as aerospace. In particular, it has the ability to be consolidated in situ and does not require secondary processing in an autoclave. Compared with thermosetting composites, it simplifies the manufacturing process and reduces manufacturing costs. Automated Fiber Placement (AFP) technology uses heat sources such as lasers and infrared to heat the composite prepreg tapes. The heated prepreg tapes are bonded together along a predetermined trajectory under the action of a pressure roller and finally formed into the desired parts. Taking advantage of the in-situ consolidation forming characteristics of thermoplastic composites, automatic placement technology can quickly form complex curved parts, significantly improving manufacturing efficiency, and its importance in the field of fiber-reinforced composite manufacturing is becoming increasingly prominent.

[0003] The automatic fiber placement device consists of two parts: a placement head and a motion actuator. Common motion actuators include six-axis industrial robots and gantry machine tools. When forming complex curved parts, the motion actuator drives the placement head to follow a complex spatial trajectory on the prefabricated mold. The placement head performs actions such as wire feeding and heating, and performs shearing when it reaches the shearing point of the trajectory. Existing automatic placement molding devices need to prefabricate molds according to the shape of the parts when forming complex curved parts, which greatly increases the manufacturing cost, and the forming accuracy and surface quality of the parts depend to a large extent on the accuracy and surface quality of the mold. In the processing of the shearing action, some devices perform the shearing action while moving, but because the cutter is stationary, this will cause the prepreg tape to have obvious ridges at the shearing position, and have an adverse effect on the accuracy and mechanical properties of the final formed part; some devices stop moving after moving to the shearing position and then perform the shearing action, but because the motion actuator has an acceleration and deceleration process when stopping and starting, and the existing heating devices such as lasers and infrared operate in a constant power mode, the temperature of the prepreg tape is too high when the laying device is laying near the shearing position, resulting in the mechanical properties near this position after the part is formed being different from those at other positions, affecting the final forming quality and consistency of the entire part. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a constant temperature controlled curved fiber placement method and system, which is used to solve the problem of poor forming quality caused by temperature fluctuations at and near the shear position due to acceleration and deceleration of the motion actuator in the existing automatic fiber curved surface placement process.

[0005] To achieve the above object, according to one aspect of the present invention, a method for placing curved fibers under constant temperature control is provided, comprising:

[0006] S1, automatically placing fibers on a curved surface, heating the placement area in real time during the placement process, and monitoring and obtaining the measured temperature value of the placement area in real time;

[0007] S2, correcting the measured temperature value according to the deviation relationship between the actual heating temperature when the laying position is a curved surface and the theoretical heating temperature when the laying position is equivalent to a flat surface, to obtain a corrected real temperature value;

[0008] S3, adjusting the heating power of the placement part according to the deviation between the actual temperature value and the preset target temperature value, so as to achieve constant temperature control of the curved fiber placement process.

[0009] According to the constant temperature controlled curved surface fiber placement method provided by the present invention, the placement location is the meshing area between the fiber prepreg tape and the placement mold surface or the formed curved surface.

[0010] According to the constant temperature controlled curved fiber placement method provided by the present invention, in S1, a heating module is used to heat the placement part in real time; accordingly, the deviation relationship in S2 is obtained as follows:

[0011] Obtaining an area deviation between an actual heating area of ​​the heating region of the heating module projected on the laying position and a theoretical heating area projected on the plane as the deviation relationship;

[0012] The measured temperature value is corrected according to the area deviation to obtain the true temperature value.

[0013] According to the constant temperature controlled curved fiber placement method provided by the present invention, S2 specifically includes:

[0014] According to the normal vector characteristics of the laying part and the direction vector characteristics of the heating module, the corresponding relationship between the surface area of ​​the laying part and the area of ​​the heating area is obtained;

[0015] According to the distance characteristics between the heating module and the laying position, the theoretical heating area of ​​the heating area projected on the plane is obtained;

[0016] According to the corresponding relationship between the curved surface area of ​​the laying part and the area of ​​the heating area, and the theoretical heating area of ​​the heating area projected on the plane, the actual heating area of ​​the heating area projected on the laying part is obtained;

[0017] The measured temperature value is corrected according to the ratio between the actual heating area of ​​the heating area projected on the laying position and the theoretical heating area projected on the plane to obtain the real temperature value.

[0018] According to the constant temperature controlled curved fiber placement method provided by the present invention, the actual temperature value is specifically:

[0019] T amend =T measure ·S authentic / S;

[0020]

[0021] S authentic = k·|L a -L s |·S standard ;

[0022]

[0023] Among them, T measure To measure the temperature, T amend is the corrected true temperature value; S authentic is the actual heating distance L a The theoretical heating area of ​​the lower heating module; S is the actual heating area of ​​the curved surface after the heating area is projected onto the curved surface; dS proj is the projection area of ​​the surface element dS at the placement location in the heating area; N is the normal vector at the placement location on the surface, V laser is the direction vector of the heating direction of the heating module in the surface coordinate system; S standard is the standard heating distance L s The heating area of ​​the lower heating module; k is the spot magnification factor.

[0024] According to the constant temperature controlled curved fiber placement method provided by the present invention, the direction vector of the heating direction of the heating module in the curved surface coordinate system is V laser It is obtained by the normal vector N at the placement position on the surface and the position Rot of the heating module relative to the placement module, where:

[0025]

[0026] According to the constant temperature controlled curved fiber placement method provided by the present invention, before S1, the method further includes:

[0027] Forming a water-soluble resin curved surface mold blank through a granular material printing head;

[0028] Use the electric spindle to mill the surface of the mold blank to meet the preset laying accuracy requirements;

[0029] Correspondingly, S3 and later also include:

[0030] After the placement is completed, the mold is removed by soaking with an organic solvent to obtain a curved surface part.

[0031] According to another aspect of the present invention, a constant temperature controlled curved fiber placement system is provided, comprising an automatic placement module, a heating module, a temperature measurement module, a constant temperature control module and a main controller, wherein the automatic placement module and the heating module are integrally installed at a preset angle, and the temperature measurement module is installed on the heating module; the constant temperature control module is respectively connected to the heating module and the temperature measurement module, and is used to adjust the power of the heating module according to the measured temperature value obtained by the temperature measurement module; the main controller is respectively connected to the automatic placement module and the constant temperature control module, and is used to control each component to implement the constant temperature controlled curved fiber placement method described in any one of the above items.

[0032] The constant temperature controlled curved fiber placement system provided by the present invention also includes an electric spindle cutting module and a granular material printing module, wherein the electric spindle cutting module and the granular material printing module are respectively integrated with the automatic placement module and are respectively connected to the main controller; the granular material printing module is used for printing and forming a water-soluble resin curved surface mold blank; the electric spindle cutting module is used for milling the surface of the mold blank.

[0033] According to the constant temperature controlled curved fiber placement system provided by the present invention, the heating module includes a laser lens group and a laser, the laser and the laser lens group are connected by an optical fiber, the laser lens group is installed integrally with the automatic placement module, and the temperature measurement module includes a monochromatic pyrometer coaxial temperature measuring device coaxially arranged with the laser lens group.

[0034] In general, compared with the prior art, the above technical solutions conceived by the present invention provide a method and system for placing curved fibers under constant temperature control:

[0035] 1. A method for controlling the constant placement temperature is proposed during the automatic fiber placement process, which solves the problem of unstable placement temperature during the acceleration and deceleration of the motion actuator when performing the shearing action, realizes the constant temperature during the entire automatic fiber placement process, and improves the forming quality and consistency of complex curved surface parts formed by automatic placement;

[0036] 2. It is proposed to correct the measured temperature value based on the temperature deviation between the heating module for the curved surface and the heating module for the flat surface. The corrected true temperature value is closer to the actual temperature, and then the constant temperature control is performed based on the true temperature value, which is conducive to more accurate realization of constant temperature control in curved fiber placement, especially suitable for fiber placement on complex curved surfaces;

[0037] 3. The proposed specific temperature correction process for curved surfaces makes the temperature more accurate and computationally efficient after correction, which can achieve high-frequency constant temperature control, thereby better achieving temperature consistency during fiber placement;

[0038] 4. It is proposed to use a granular material print head to quickly form high-temperature resin complex curved surface mold blanks, and use an electric spindle to mill the mold surface to achieve the accuracy and surface quality required for automatic fiber placement. This solves the problem of prefabricated molds in current automatic placement technology, improves the efficiency of automatic placement and molding of complex curved surface parts of thermoplastic composite materials, and reduces manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic diagram of a constant temperature controlled curved fiber placement method provided by the present invention;

[0040] Figure 2 It is a schematic diagram of a high-temperature resin complex curved surface mold blank provided by the present invention;

[0041] Figure 3 It is a schematic diagram of temperature calculation of the coaxial pyrometer provided by the present invention;

[0042] Figure 4 Schematic diagram of the constant temperature controlled curved fiber placement system provided by the present invention;

[0043] Figure 5 It is a schematic diagram of the automatic placement module and the temperature control unit provided by the present invention;

[0044] Figure 6 It is a temperature diagram of automatic fiber placement measurement when temperature control is not turned on provided by the present invention;

[0045] Figure 7 It is a temperature diagram of automatic fiber placement measurement after turning on temperature control provided by the present invention;

[0046] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0047] 100-automatic placement module; 200-electric spindle cutting module; 300-granular material printing module; 1-prepreg tray; 2-roller; 3-wire feeding device; 4-tension measuring device; 51-wire feeding cylinder; 52-tension cylinder; 53-re-feeding cylinder; 6-pressure control cylinder; 7-re-feeding mechanism; 8-clamping mechanism; 9-wall panel; 10-shearing mechanism; 11-pressure roller; 12-laser lens group; 13-laser; 14-constant temperature control module; 15-prepreg tape. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0049] See also Figure 1 This embodiment provides a method for placing curved fibers under constant temperature control, the method comprising:

[0050] S1, automatically placing fibers on a curved surface, heating the placement area in real time during the placement process, and monitoring and obtaining the measured temperature value of the placement area in real time;

[0051] S2, correcting the measured temperature value according to the deviation relationship between the actual heating temperature when the laying part is a curved surface and the theoretical heating temperature when the laying part is equivalent to a flat surface, to obtain a corrected real temperature value;

[0052] S3, adjusting the heating power of the placement part according to the deviation between the actual temperature value and the preset target temperature value, so as to achieve constant temperature control of the curved fiber placement process.

[0053] The fiber placement method provided in this embodiment uses a temperature detection and real-time control method during the placement process, which solves the problem of excessive local placement temperature caused by the motion actuator during acceleration and deceleration, improves the process consistency during automatic placement, and greatly improves the forming quality of complex curved surface parts.

[0054] In S1, the heating module is used to heat the laying part in real time. Further, this embodiment takes into account that the existing temperature measuring instruments, such as infrared measuring instruments, are usually suitable for temperature measurement of planes, and the measurement accuracy is high when measuring the temperature of planes, while most fiber laying conditions are curved surface laying to form curved surface parts. When the existing temperature measuring instruments are used to measure the surface temperature of curved surfaces in curved fiber laying, some errors are inevitable; and according to the principle of the temperature measuring instrument, the temperature measuring instrument usually obtains the measured temperature value based on the heating area of ​​the heating module falling on the plane through temperature integration, while the actual heating area of ​​the heating module falls on the curved surface, and the heating temperature that can be achieved by the heating module for heating the curved surface and the heating for heating the flat surface is different; based on this, it is proposed to correct the measured temperature value according to the deviation between the heating temperature when the heating module heats the curved surface and the heating temperature when the heating module heats the flat surface, so that the corrected real temperature value is more accurate and closer to the real temperature value, and then the power of the heating module is adjusted based on the real temperature value and the target temperature value, which is conducive to better and more accurate realization of constant temperature control in curved fiber laying, especially suitable for fiber laying on complex curved surfaces.

[0055] Specifically, the placement location is the meshing area between the fiber prepreg tape and the placement mold surface or the formed curved surface. When placing the first layer of fibers on the surface of the placement mold, the placement location is the meshing area between the fiber prepreg tape and the placement mold surface; when placing fibers on the surface of the formed curved surface, the placement location is the meshing area between the fiber prepreg tape and the formed curved surface. The meshing area is the overlapping area between the pressure roller of the placement device, the fiber prepreg tape and the placement mold surface or the formed curved surface.

[0056] In some specific embodiments, according to the measurement principle of the above-mentioned temperature measuring instrument, the temperature measuring instrument performs temperature integration based on a plane when obtaining the measured temperature value, but in fact the heating area of ​​the heating module falls on the curved surface and becomes a curved surface, so that the deviation of the projected area of ​​the heating area on the plane and the curved surface causes an error between the measured temperature value and the actual temperature value. It is further proposed that the deviation relationship in S2 is obtained as follows:

[0057] Obtaining an area deviation between an actual heating area of ​​the heating region of the heating module projected on the laying position and a theoretical heating area projected on the plane as the deviation relationship;

[0058] The measured temperature value is corrected according to the area deviation to obtain the true temperature value.

[0059] Furthermore, the projection area of ​​the heating area on the curved surface, i.e., the actual heating area of ​​the heating area projected on the laying part, is related to the curved surface features of the laying part and the heating module posture, and the measured temperature value can be corrected based on the curved surface features of the laying part and the heating module posture. Specifically, S2 specifically includes:

[0060] According to the normal vector characteristics of the laying part and the direction vector characteristics of the heating module, the corresponding relationship between the surface area of ​​the laying part and the area of ​​the heating area is obtained;

[0061] According to the distance characteristics between the heating module and the laying position, the theoretical heating area of ​​the heating area projected on the plane is obtained;

[0062] According to the corresponding relationship between the curved surface area of ​​the laying part and the area of ​​the heating area, and the theoretical heating area of ​​the heating area projected on the plane, the actual heating area of ​​the heating area projected on the laying part is obtained;

[0063] The measured temperature value is corrected according to the ratio between the actual heating area of ​​the heating area projected on the laying position and the theoretical heating area projected on the plane to obtain the real temperature value.

[0064] In some specific embodiments, the heating module includes a laser lens group and a laser, the laser and the laser lens group are connected by an optical fiber, the laser lens group is installed integrally with the automatic placement module, and the temperature measurement module includes a monochromatic pyrometer coaxial temperature measurement device coaxially arranged with the laser lens group. The automatic placement module is connected to the motion actuator, and is used to perform automatic fiber placement driven by the motion actuator.

[0065] Furthermore, the curved surface fiber placement method provided in this embodiment is to perform automatic fiber placement in a constant temperature laser control mode, and the constant temperature laser control method is specifically as follows:

[0066] The target temperature and other parameters for placement are set, and the motion actuator starts to move, turning on the laser to heat the meshing area between the prepreg tape and the mold surface or the formed surface;

[0067] The coaxial monochromatic pyrometer measures the temperature data of the meshing area;

[0068] The temperature control module controls the laser output power at a frequency of up to 10kHz by comparing the measured temperature with the set value through a specific temperature control algorithm, so that the measured temperature in the meshing area is the same as the set temperature;

[0069] After placement is completed, turn off the laser heating and temperature control.

[0070] Furthermore, the constant temperature control strategy in this embodiment is different from the existing control strategy based on the temperature value tested by the temperature measuring instrument. Common monochrome pyrometers divide the measurement area into several sub-areas, integrate the temperature in each sub-area and add them up, and finally use the rectangular spot area to average the temperature. For automatic laying of complex surfaces, when the rectangular laser spot heats the meshing area, it can be understood as a rectangular spot projected onto the surface, and the actual temperature is related to the curvature characteristics of the surface. This embodiment uses a specific control algorithm in the laser constant temperature control to control the laser power in the heating area at a frequency of up to 10kHz, and the temperature is corrected in the temperature measurement taking into account the complex surface characteristics and the posture of the laying device.

[0071] The actual temperature value is specifically:

[0072] T amend =T measure ·S authentic / S;

[0073]

[0074] S authentic = k·|L a -L s |·S standard ;

[0075]

[0076] Among them, T measure To measure the temperature, T amend is the corrected true temperature value; S authentic is the actual heating distance L a The theoretical heating area of ​​the lower heating module; S is the actual heating area of ​​the curved surface after the heating area is projected onto the curved surface; dS proj is the projection area of ​​the surface element dS at the placement location in the heating area; N is the normal vector at the placement location on the surface, V laser is the direction vector of the heating direction of the heating module in the surface coordinate system; S standard is the standard heating distance L s The heating area of ​​the lower heating module; k is the spot magnification factor, which is an inherent parameter of the laser mirror assembly.

[0077] refer to Figure 3 The rectangular laser spot emitted by the laser mirror group is at the standard heating distance L s The spot area of ​​the lower relative plane is S standard , actual heating distance L a The spot area of ​​the lower relative plane is S authenticThen the actual area of ​​the projected part of the actual rectangular light spot on the curved surface after being projected onto the curved surface is S. The actual heating distance is known in advance according to the installation positions of the laying device and the heating module.

[0078] The heating direction of the heating module in the surface coordinate system is V laser It is obtained by the normal vector N at the placement position on the surface and the position Rot of the heating module relative to the placement module, where:

[0079]

[0080] Rot' is a sub-matrix of the matrix Rot; the above formula is used to correct the temperature measured by the monochromatic pyrometer surface. The normal vector at the placement position on the surface is known in advance based on the surface part model; the position of the heating module relative to the placement module is known in advance based on the installation positions of the two.

[0081] Furthermore, a hyperbolic surface is used as the laying surface, the position of the laying device is expressed as (0, 0, 0, 180, 0, 180) using Euler angles, and when the angle between the laser lens group and the laying device is 60°, the pyrometer measurement temperature calculated using the temperature correction method is 82.3% of the uncorrected temperature.

[0082] Furthermore, before S1, it also includes:

[0083] Forming a water-soluble resin curved surface mold blank through a granular material printing head;

[0084] Use the electric spindle to mill the surface of the mold blank to meet the preset laying accuracy requirements;

[0085] Correspondingly, S3 and later also include:

[0086] After the placement is completed, the mold is removed by soaking with an organic solvent to obtain a curved surface part.

[0087] See also Figure 1 This embodiment provides a fiber placement method for constant temperature controlled laser in-situ consolidation forming, the placement method comprising:

[0088] Rapidly form complex curved mold blanks made of high-temperature water-soluble resin through a granular material print head;

[0089] Use the electric spindle to mill the mold surface to achieve the required placement accuracy and surface quality;

[0090] The automatic fiber placement process is used to form curved surface parts. During the placement process, the laser is always turned on for heating and receives the output signal of the temperature control module to change the laser output power in real time, so that the temperature of the placement process is constant;

[0091] After laying is completed, the mold is removed by soaking with an organic solvent to obtain a complex curved surface part.

[0092] The laying method provided in this embodiment is to directly perform constant temperature laying of continuous fiber thermoplastic composite materials on a high-temperature mold that has been rapidly printed and milled, eliminating the step of prefabricating molds in the traditional laying process, increasing the flexibility of automatic laying, and shortening the manufacturing cycle of fiber-reinforced composite components.

[0093] Furthermore, the pellet print head uses a screw extrusion structure, and the raw materials used are high-temperature resin pellets or short-cut fiber reinforced thermoplastic resin pellets. Figure 2 The printing method has low printing cost and high printing efficiency, but poor printing accuracy and obvious step effect, but the method can quickly print the required curved surface mold blank. The high temperature resin particles include high temperature resistant thermoplastic resin particles and short fiber reinforced thermoplastic resin composite particles.

[0094] Furthermore, the electric spindle milling unit is used to trim the rough curved mold blank obtained by printing. Figure 2 After trimming the high-temperature resin mold with a ball-end milling cutter, the mold's precision and surface quality can meet the placement requirements. Due to the use of high-temperature resistant resin, the mold can withstand the high temperature generated by laser heating during automatic fiber placement.

[0095] Furthermore, the application scenarios of the temperature control method are not limited to automatic fiber placement, but can also be used for automatic fiber tape laying and automatic fiber winding.

[0096] Furthermore, the heating method of the temperature control method is not limited to laser heating, and xenon lamp heating, high temperature gas heating, infrared heating, etc. can also be used.

[0097] Furthermore, the raw material used for printing high-temperature molds is resin particles, and its types include but are not limited to the polyetheretherketone (PEEK) family, polyaryletherketone (PAEK), polyphenylene sulfide (PPS), polyetherimide (PEI), polyethersulfone (PES), polyamide (PA), short fiber reinforced thermoplastic composite particles, etc.

[0098] Furthermore, the fiber prepreg used in the fiber placement method is a continuous fiber reinforced thermoplastic composite material, the reinforcing fibers include carbon fibers, basalt fibers, glass fibers, plant fibers and aramid fibers, and the composite material matrix includes the polyetheretherketone (PEEK) family, polyaryletherketone (PAEK), polyphenylene sulfide (PPS), polyetherimide (PEI), polyethersulfone (PES), polyamide (PA), etc.

[0099] Furthermore, this embodiment also provides a temperature-controlled curved fiber placement system, referring to Figure 4 The curved fiber placement system includes an automatic placement module 100, a heating module, a temperature measurement module, a constant temperature control module 14 and a main controller. The automatic placement module 100 and the heating module are integrally installed at a preset angle, and the temperature measurement module is installed on the heating module; the constant temperature control module 14 is respectively connected to the heating module and the temperature measurement module, and is used to adjust the power of the heating module according to the measured temperature value obtained by the temperature measurement module; the main controller is respectively connected to the automatic placement module 100 and the constant temperature control module 14, and is used to control each component to implement any of the above-mentioned constant temperature controlled curved fiber placement methods.

[0100] In some specific embodiments, the curved fiber placement system further includes an electric spindle cutting module 200 and a granular material printing module 300, which are respectively integrally installed in the automatic placement module 100 and are respectively connected to the master controller; the granular material printing module 300 is used to print and shape a water-soluble resin curved surface mold blank; the electric spindle cutting module 200 is used to mill the surface of the mold blank. The automatic placement module 100, the electric spindle cutting module 200, the granular material printing module 300 and the laser lens group 12 are connected as a mechanical connection, and the laser lens group 12, the laser 13 and the constant temperature control module 14 are connected as an electrical connection, that is, a signal connection, which can be connected through a signal line.

[0101] Furthermore, the particle material printing module 300 is connected to the automatic placement module 100 through a linear module. When mold printing is required, the particle material printing module 300 moves downward through the linear module, and the resin particles are quickly printed to form a high-temperature resin mold blank after screw extrusion and heating.

[0102] Furthermore, the electric spindle cutting module 200 is connected to the automatic placement module 100 through a linear module. After the resin mold blank is printed, the electric spindle cutting module 200 moves downward through the linear module, and the mold blank to be cut is processed into a high-temperature resin mold with higher precision and surface quality through electric spindle milling.

[0103] Further, the specific structure of the continuous fiber thermoplastic composite material automatic placement module can be found in Figure 5 The automatic placement module includes a wire feeding box and a placement box. A prepreg disc 1 is arranged on the top of the wire feeding box. A continuous fiber reinforced thermoplastic prepreg tape 15 is wound on the prepreg disc 1. A wire feeding device 3, a tension measuring device 4 and a tension cylinder 52 are arranged inside the wire feeding box. The prepreg tape 15 is transported to the inside of the wire feeding box through a roller 2. There are multiple rollers 2 inside the wire feeding box for changing the direction of the prepreg tape 15. After entering the wire feeding box, the prepreg tape 15 passes through the wire feeding device 3 and the tension measuring device 4 in sequence.

[0104] The wire feeding device 3 is located at the upper part of the wire feeding box, and includes a driving wheel and a passive wheel. The driving wheel is connected to a servo motor, and the passive wheel is connected to a wire feeding cylinder 51. When the laying head starts laying, the wire feeding cylinder 51 pushes the passive wheel and the driving wheel to press tightly, and the driving wheel starts to feed the wire under the action of the servo motor to complete the wire feeding action;

[0105] The tension measuring device 4 is composed of three fixed pulleys, and a tension sensor is installed on the middle pulley shaft. The entire tension measuring device 4 is mechanically connected to the tension cylinder 52. When laying, the tension is PID controlled by the speed difference between the wire feeding speed of the wire feeding device 3 and the movement speed of the robot. The input tension measurement value is compared with the set value. If the tension measurement value is less than the set value, the wire feeding speed is reduced, and vice versa.

[0106] A pressure control cylinder 6 is provided between the laying material box and the wire feeding material box, and the pressure control cylinder 6 controls the pressure generated by the cylinder through a pneumatic balance circuit. An electromagnetic pressure regulating valve is provided on the pneumatic balance circuit, and the pressure on the upper part of the cylinder can be controlled through the pressure regulating valve according to the pressure sensor provided above the pressure roller, thereby maintaining a constant pressure during the entire laying process.

[0107] A re-feeding mechanism 7 is arranged on the top of the laying material box, including a driving wheel and a passive wheel. The driving wheel is connected to a servo motor, and the passive wheel is connected to a re-feeding cylinder 53. When a track is laid, the laying head performs a shearing action, and at this time, the re-feeding mechanism 7 is required to re-feed the prepreg tape to the pressure roller position. When re-feeding is required, the re-feeding cylinder 53 pushes the passive wheel and the driving wheel to press tightly, and the driving wheel starts to re-feed under the action of the servo motor. After the re-feeding reaches the specified length, the re-feeding ends, and the re-feeding cylinder 53 and the servo motor are turned off.

[0108] A clamping mechanism 8 is provided below the re-feeding mechanism 7. The clamping mechanism 8 comprises a clamping cylinder and a clamping block. Before performing the shearing action, the clamping cylinder operates the clamping block to clamp the prepreg tape to the wallboard 9 to prevent the prepreg tape from rebounding.

[0109] A shearing mechanism 10 is provided below the clamping mechanism 8. When a trajectory reaches the shearing point, the shearing cylinder is actuated to shear the prepreg tape.

[0110] A pressure roller 11 is provided at the end of the automatic placement module. The pressure roller is composed of a rigid mandrel and a high temperature resistant flexible rubber outer layer. A pressure sensor is designed above the rigid mandrel to measure the pressure during placement. The high temperature resistant flexible rubber outer layer can better compact the prepreg tape.

[0111] The automatic placement module heats the prepreg tape by a constant temperature controlled laser heating system during placement. The constant temperature controlled laser heating system includes a laser lens group 12, a laser 13 and a constant temperature control module 14. The laser lens group includes a laser output lens group and a pyrometer coaxial temperature measuring device. The laser output lens group is used to output the infrared laser generated by the laser, and the laser spot is a rectangular spot. The pyrometer coaxial temperature measuring device can measure the average temperature in the spot at the laser coaxial position and output it to the constant temperature control module 14; the laser 13 can generate an infrared laser within 0-10kW, and the laser can receive a 0-10V analog signal for controlling the output power; the constant temperature control module 14 can receive the temperature signal emitted by the pyrometer coaxial temperature measuring device, and output an analog control signal to control the laser power after temperature correction. The constant temperature control module 14 compares the temperature measured by the pyrometer with the set temperature, and outputs the control analog quantity at a frequency of 10kHz through a special control algorithm to control the laser output power, so that the average temperature in the rectangular spot measured by the pyrometer is constant.

[0112] In some specific embodiments, when the constant temperature control mode is not turned on for laying, the laser outputs laser at a constant power of 400W, and the pyrometer measures the temperature as follows: Figure 6 As shown in the figure, it can be seen that the temperature measured by the pyrometer fluctuates by about 40°C, and before moving to the shear position, the temperature rises to nearly 420°C due to the deceleration of the motion actuator. The drastic temperature change will cause the performance of the prepreg tape at the shear position to be quite different from that at other positions. When the temperature of the thermostatic control device is set to 340°C and the thermostatic control mode is turned on for laying, the temperature measured by the pyrometer is as follows Figure 7 As shown, the temperature curve measured by the pyrometer basically coincides with the set value straight line, the control error of the temperature control device is within 0.5%, achieving a good temperature control effect, and the process performance at the shearing position has no obvious difference from that at other positions.

[0113] The present invention provides a fiber placement method and device for constant temperature controlled laser in-situ consolidation forming, which not only proposes a process method combining mold printing-mold trimming-automatic placement, but also innovatively proposes a constant temperature controlled laser in-situ consolidation placement method on this basis, thereby solving the problem that the existing automatic fiber placement device needs a prefabricated mold when forming complex curved surface parts and the problem of poor forming quality at the shear position and near the position due to large temperature fluctuations during placement.

[0114] Compared with the current automatic placement process, the automatic placement method provided by the present invention eliminates the step of prefabricating molds, increases the flexibility of automatic placement, and shortens the manufacturing cycle of fiber-reinforced composite materials; and because a temperature detection, correction and real-time control method is used during the placement process, the problem of excessive local placement temperature caused by acceleration and deceleration of the motion actuator is solved, the process consistency during the automatic placement process is improved, and the quality of automatic placement of complex curved surface parts is greatly improved.

[0115] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for placing curved fibers under constant temperature control, characterized in that: include: S1, automatically placing fibers on a curved surface, heating the placement area in real time during the placement process, and monitoring and obtaining the measured temperature value of the placement area in real time; S2, correcting the measured temperature value according to the deviation relationship between the actual heating temperature when the laying part is a curved surface and the theoretical heating temperature when the laying part is equivalent to a flat surface, to obtain a corrected real temperature value; S3, adjusting the heating power of the placement part according to the deviation between the actual temperature value and the preset target temperature value, so as to achieve constant temperature control of the curved fiber placement process.

2. The method for placing curved fibers under constant temperature control according to claim 1, characterized in that: The placement location is the meshing area between the fiber prepreg tape and the surface of the placement mold or the formed curved surface.

3. The method for placing curved fibers under constant temperature control according to claim 1, characterized in that: In S1, the heating module is used to heat the laying part in real time; accordingly, the deviation relationship in S2 is obtained as follows: Obtaining an area deviation between an actual heating area of ​​the heating region of the heating module projected on the laying position and a theoretical heating area projected on the plane as the deviation relationship; The measured temperature value is corrected according to the area deviation to obtain the true temperature value.

4. The method for placing curved fibers under constant temperature control as claimed in claim 3, characterized in that: S2 specifically includes: According to the normal vector characteristics of the laying part and the direction vector characteristics of the heating module, the corresponding relationship between the surface area of ​​the laying part and the area of ​​the heating area is obtained; According to the distance characteristics between the heating module and the laying position, the theoretical heating area of ​​the heating area projected on the plane is obtained; According to the corresponding relationship between the curved surface area of ​​the laying part and the area of ​​the heating area, and the theoretical heating area of ​​the heating area projected on the plane, the actual heating area of ​​the heating area projected on the laying part is obtained; The measured temperature value is corrected according to the ratio between the actual heating area of ​​the heating area projected on the laying position and the theoretical heating area projected on the plane to obtain the real temperature value.

5. The method for placing curved fibers under constant temperature control as claimed in claim 3, characterized in that: The actual temperature value is specifically: T amend =T measure ·S authentic / S; S authentic =k·|L a -L s |·S standard ; Among them, T measure To measure the temperature, T amend is the corrected true temperature value; S authentic is the actual heating distance L a The theoretical heating area of ​​the lower heating module; S is the actual heating area of ​​the curved surface after the heating area is projected onto the curved surface; dS proj is the projection area of ​​the surface element dS at the placement location in the heating area; N is the normal vector at the placement location on the surface, V laser is the direction vector of the heating direction of the heating module in the surface coordinate system; S standard is the standard heating distance L s The heating area of ​​the lower heating module; k is the spot magnification factor.

6. The method for placing curved fibers under constant temperature control as claimed in claim 5, characterized in that: The heating direction of the heating module in the surface coordinate system is V laser It is obtained by the normal vector N at the placement position on the surface and the position Rot of the heating module relative to the placement module, where:

7. The method for placing curved fibers under constant temperature control according to any one of claims 1 to 6, characterized in that: Before S1, it also included: Forming a water-soluble resin curved surface mold blank through a granular material printing head; Use the electric spindle to mill the surface of the mold blank to meet the preset laying accuracy requirements; Correspondingly, S3 and later also include: After the placement is completed, the mold is removed by soaking with an organic solvent to obtain a curved surface part.

8. A constant temperature controlled curved fiber placement system, characterized in that: It includes an automatic placement module, a heating module, a temperature measurement module, a constant temperature control module and a main controller, wherein the automatic placement module and the heating module are integrally installed at a preset angle, and the temperature measurement module is installed on the heating module; the constant temperature control module is respectively connected to the heating module and the temperature measurement module, and is used to adjust the power of the heating module according to the measured temperature value obtained by the temperature measurement module; the main controller is respectively connected to the automatic placement module and the constant temperature control module, and is used to control each component to realize the constant temperature controlled curved fiber placement method described in any one of claims 1 to 7.

9. The constant temperature controlled curved fiber placement system according to claim 8, characterized in that: It also includes an electric spindle cutting module and a granular material printing module, which are respectively installed in one piece on the automatic placement module and are respectively connected to the main controller; the granular material printing module is used for printing and forming a water-soluble resin curved surface mold blank; the electric spindle cutting module is used for milling the surface of the mold blank.

10. The constant temperature controlled curved fiber placement system according to claim 8, characterized in that: The heating module includes a laser lens group and a laser, the laser and the laser lens group are connected via an optical fiber, the laser lens group is integrally installed with the automatic placement module, and the temperature measurement module includes a monochromatic pyrometer coaxial temperature measuring device coaxially arranged with the laser lens group.

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