3D printing system and operating method for composite solid rocket motor insulation

Abstract

The present application relates to the technical field of thermal protection layer forming, and particularly relates to a composite material solid rocket engine heat insulation layer 3D printing system and an operating method. The printing system comprises a feeding system and a mechanical arm system. The feeding system further comprises a storage device, a mixing device and a hydraulic device. The mixing device is connected to the storage device through a pipeline. The hydraulic device delivers the heat insulation material in the storage device to the mixing device through the pipeline. The mechanical arm system further comprises a mechanical arm and a control unit. The head of the mechanical arm is provided with the mixing device and a printing head. The mixing device is connected to the printing head. The control unit has a heat insulation layer model slicing function and controls the movement of the mechanical arm and the printing of the printing head. The head of the mechanical arm is further provided with a curing device and a thickness measuring device. The thickness measuring device can measure the thickness of the heat insulation structure. The mechanical arm system automatically adjusts the process parameters according to the measurement results, and continues to print the areas whose thickness does not meet the requirements, thereby fully guaranteeing the printing effect and improving the reliability of the heat insulation layer.

Description

Technical Field

[0001] This invention relates to the field of thermal protection layer molding technology, and in particular to a 3D printing system and operating method for a composite solid rocket motor thermal insulation layer. Background Technology

[0002] The internal insulation layer of a solid rocket motor is one of its core components. Statistics show that over 70% of rocket launch failures are caused by thermal protection failure. Inadequate thermal protection technology can lead to burn-through of the engine's combustion chamber. The most famous example is the 1993 explosion of the US Titan IV rocket after launch; analysis indicated the explosion was caused by thermal insulation failure and burn-through of the engine's aft end cap.

[0003] The existing composite solid rocket motor internal insulation layer usually follows the following process technology route: (1) Head molding: The insulation material sheet is laid in the head mold and molded by high temperature and high pressure. Then the head is fitted onto the core mold; (2) Column section patching: The insulation material sheet is manually laid on the core mold column section. The overlap between the head and the column section is bonded with adhesive. However, head molding requires manual placement of the material sheet in the mold, which often results in air entrapment, increasing the risk of fire and burn-through of the insulation structure. At the same time, manual placement of the material sheet is inefficient and increases labor costs. Head molding also requires molding molds and high temperature and high pressure vulcanization equipment, which increases the cost of molds and equipment. Column section patching is also a manual operation, which is prone to problems such as uneven thickness of the insulation material sheet and poor quality consistency. The column section and the head are segmented structures, and the overlap is bonded with adhesive. The overall integrity of the insulation structure is poor, which reduces the reliability of the insulation layer.

[0004] The above-mentioned technologies suffer from problems such as low efficiency of manual operation, easy air entrapment, uneven thickness, poor quality consistency, and high mold and equipment costs; they cannot meet the development requirements of high performance, low cost, high reliability, and high efficiency of solid rockets.

[0005] Based on existing patent solutions, a 3D printing system and method for the internal insulation layer of a solid rocket engine (CN202010323345.6) proposes a micro-jet printing method for the insulation layer, with a single printing thickness on the order of hundreds of micrometers, which greatly limits the printing efficiency of the insulation layer. This system lacks a detection system, making it impossible to detect and obtain insulation layer thickness data during printing, and impossible to adjust 3D printing parameters for thickness compensation during the process; furthermore, this patent does not describe in detail the specific operation method for printing the internal insulation layer of a solid rocket engine.

[0006] A 3D printing device for solid rocket motor insulation layers (CN109501256A) was proposed, which describes a 3D printing apparatus for the inside of the engine casing. However, this method is limited by the size of the print head assembly and cannot achieve 3D printing inside small-diameter casings. Furthermore, the low-light and confined space inside the casing increases the difficulty of measuring the insulation layer thickness during 3D printing. This method involves transferring the printed insulation layer to an oven for heating and curing, which carries the risk of the uncured insulation layer adhering and being carried away during printing. When printing thick insulation structures, there is a risk of the uncured insulation layer sagging.

[0007] The 3D printing solid propellant / insulation layer formulation and its integrated preparation method (CN111559948A) proposes a method for simultaneous printing of propellant and insulation layer. This method is suitable for engines with free-loading propellant loading mode, but cannot be applied to composite material engines with wall-mounted propellant loading mode. At the same time, the system also has the problem of lacking a thickness detection system. Summary of the Invention

[0008] Based on the above, the purpose of this invention is to provide a 3D printing system and operation method for the insulation layer of a composite solid rocket engine that can balance efficiency and accuracy, thereby enabling the detection and compensation of the insulation layer thickness during the printing process while preventing the uncured insulation layer from being adhered, carried away, or sagging.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A 3D printing system for the thermal insulation layer of a composite solid rocket motor, comprising: The feeding system includes a storage device, a mixing device, and a hydraulic device. There are multiple storage devices, and the mixing device is connected to multiple storage devices via pipelines. The hydraulic device transports the insulation material in the storage devices to the mixing device through pipelines. A robotic arm system includes a robotic arm and a control unit. The head of the robotic arm is equipped with a mixing device and a print head, and the mixing device is connected to the print head. The control unit has a function of slicing insulation layer models and controls the movement of the robotic arm and the printing of the print head. The head of the robotic arm is also equipped with a curing device and a thickness measuring device.

[0010] As a preferred embodiment of a composite solid rocket motor insulation layer 3D printing system, a metering device is provided at the pipeline between the mixing device and the storage device.

[0011] As a preferred embodiment of a composite solid rocket motor insulation layer 3D printing system, the outer surface of the mixing device is provided with a cooling system.

[0012] As a preferred embodiment of a composite solid rocket motor insulation layer 3D printing system, the nozzle of the printing head has different shapes and sizes. The nozzle shape of the printing head includes rectangular, parallelogram, triangular, trapezoidal, circular and elliptical shapes. The nozzle thickness of the printing head is 0.1mm~5mm and the width is 5mm~100mm.

[0013] As a preferred embodiment of a composite solid rocket motor insulation layer 3D printing system, the direction of energy emitted by the curing device is consistent with the output direction of the printing head, and the energy emitted by the curing device can be selected from one of three forms, including: microwave, ultraviolet light or infrared light.

[0014] As a preferred embodiment of a 3D printing system for the insulation layer of a composite solid rocket engine, the thickness measuring device is specifically a 3D scanner or a thickness gauge, and the orientation of the 3D scanner or the thickness gauge is consistent with the output direction of the print head.

[0015] As a preferred embodiment of a 3D printing system for the insulation layer of a composite solid rocket motor, the system further includes a rotating fixture for fixing and rotating a solid rocket motor core mold. The core mold consists of end caps at both ends and a cylindrical section in the middle. The end caps at both ends are partially hemispherical, and the cylindrical section is cylindrical. The diameter of the bottom of the end caps is equal to the diameter of the cylindrical section.

[0016] A method for 3D printing a composite solid rocket motor insulation layer, the method being applied to the composite solid rocket motor insulation layer 3D printing system described above, comprising the following steps: S1: Fix the solid rocket motor core mold onto the rotating fixture, set the rotation speed of the rotating fixture, input the three-dimensional model of the insulation layer into the robotic arm system, set the single-layer slice thickness, and the control unit slices the insulation layer layer by layer to generate a slice image. S2: Place the different insulation materials after defoaming into multiple storage devices, set the mixing ratio, turn on the cooling system of the mixing device, and control the feeding speed of the hydraulic device through the metering device.

[0017] S3: Select the nozzle shape and size of the print head, start the feeding system for trial operation until the nozzle of the print head outputs material evenly, and then turn off the feeding system.

[0018] S4: The control unit sets the walking angle and speed of the robotic arm, and the robotic arm drives the print head to walk on the core model surface to print the insulation layer.

[0019] S5: After the print head prints one layer, the curing device is activated, the curing mode is selected, and the robotic arm drives the curing device to move along the core model surface to cure the insulation layer. S6: Repeat S4 and S5. Every 5 layers are printed, the thickness measuring device is activated to detect the thickness of the insulation layer and compare it with the 3D model of the insulation layer. The comparison result is transmitted to the robotic arm system. For areas where the thickness does not meet the requirements, printing continues. The above operation is repeated until the insulation layer size meets the requirements.

[0020] As a preferred method for 3D printing of the insulation layer of a composite solid rocket motor, the nozzle shape and size of the print head are selected. For a thick insulation layer, a large nozzle is used for printing in the early stage, and when the printing reaches the required size, the nozzle is switched to a small nozzle for printing.

[0021] As a preferred embodiment of a 3D printing operation method for a composite solid rocket motor insulation layer, the robotic arm drives the print head to move along the core model surface to print the insulation layer. The angle between the print head and the core model is the moving angle, which is 30°~90°.

[0022] As a preferred method for 3D printing of a composite solid rocket motor insulation layer, the diameter D of the mandrel and the rotational speed V of the rotating tooling need to be controlled during the printing process. R The nozzle cross-sectional area S of the print head and the feeding speed V1 of the feeding system are matched; the axial travel speed V2 of the print head along the mandrel and the rotation speed V of the rotating tooling are also controlled. R The nozzle width L of the printhead must be matched with the following formula: S

[0023] in Z represents the shortest distance between the printing position and the column segment when the print head prints on the end cap of the core mold. Z is the diameter of the cross-sectional circle where the printing position is located; when the print head prints on the column segment, Z=0. D, the two formulas above can be simplified to: S .

[0024] The beneficial effects of this invention are as follows: (1) The feeding system and robotic arm system are used to replace manual labor, and the printing head walking speed, rotation speed and walking angle are quantitatively controlled, which avoids the problem of air trapping when manually laying the material sheet and reduces labor costs; (2) In this solution, the insulation layer is 3D printed in situ on the surface of the core mold. The insulation layer and the core mold are completely bonded, which solves the problem of gap between the traditional molded head and the core mold. It further avoids the risk of poor bonding between the insulation layer and the composite shell. At the same time, it eliminates the need for the head molding mold and high-temperature vulcanization equipment, thereby saving mold cost and vulcanization equipment cost. (3) The end caps and column sections are insulated using 3D printing, requiring no manual operation. The walking speed and angle are quantitatively controlled, and the diameter D of the core mold and the rotation speed V of the rotating tooling are controlled. R Matching the nozzle cross-sectional area S of the printhead and the feeding speed V1 of the feeding system can effectively control the uniformity of the insulation layer printing thickness and improve quality consistency. It is also necessary to control the axial travel speed V2 of the printhead along the mandrel and the rotational speed V of the rotating tooling. R The nozzle width L of the printhead is matched to prevent wrinkles and burrs from appearing at the overlap of the insulation layer; (4) The column segments and end caps are continuously 3D printed as an integral structure, which does not require the use of adhesives for bonding. Compared with the traditional manual patching process, this improves the reliability of the insulation structure. (5) A curing device is provided. After each layer is printed, the insulation layer can be cured in situ to prevent the previous insulation layer from sticking and being taken away when printing the next layer. The insulation layer is cured in situ during the printing process, which reduces the time for secondary curing of the insulation layer, shortens the manufacturing cycle of the insulation layer, and eliminates the risk of dripping that may exist during printing. (6) The head of the robotic arm is equipped with a 3D scanner or thickness gauge to measure the thickness of the insulation structure and compare it with the insulation structure model. The comparison result is transmitted to the robotic arm system. The robotic arm system automatically adjusts the process parameters and continues to print areas where the thickness does not meet the requirements. The above operation is repeated until the insulation structure size meets the requirements, which fully ensures the printing effect and improves the reliability of the insulation layer. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0026] Figure 1 This is a three-dimensional structural schematic diagram of a composite material solid rocket engine insulation layer 3D printing system provided by the present invention; Figure 2 yes Figure 1 A magnified view of a section at point A in the middle; Figure 3This is a top view of a composite solid rocket engine insulation layer 3D printing system provided by the present invention; Figure 4 yes Figure 3 A magnified view of a section at point B in the middle; Figure 5 This is a side view of a composite material solid rocket motor insulation layer 3D printing system provided by the present invention; Figure 6 yes Figure 5 A magnified view of a section at point C; Figure 7 This is a cross-sectional schematic diagram of the core mold in a 3D printing system for the insulation layer of a composite solid rocket engine provided by the present invention.

[0027] Figure label: 1-Storage device; 2-Mixing device; 3-Hydraulic device; 4-Robotic arm; 4a-Supporting disc; 5-Print head; 6-Curing device; 7-Thickness measuring device; 8-Metering device; 9-Cooling system; 10-Rotating fixture; 11-Core mold; 11a-End cap; 11b-Column section; 12-Operating table; 13-Base; 14-Wire trough wiring board. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0029] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0031] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used solely for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In the description of the present invention, unless otherwise stated, "a plurality of" means two or more. Furthermore, the terms "first" and "second" are merely used for descriptive distinction and have no special meaning.

[0032] This embodiment provides a 3D printing system for the thermal insulation layer of a composite solid rocket motor, such as... Figures 1 to 6 As shown, it includes: The feeding system includes a storage device 1, a mixing device 2, and a hydraulic device 3. Multiple storage devices 1 are provided to store different insulation materials. The insulation layer is composed of a mixture of multiple insulation materials. The mixing device 2 is connected to multiple storage devices 1 by pipes. The hydraulic device 3 transports the insulation materials in the storage devices 1 to the mixing device 2 through pipes, thereby realizing the mixing of different insulation materials. The robotic arm system includes a robotic arm 4 and a control unit. The head of the robotic arm 4 is equipped with a mixing device 2 and a print head 5, with the mixing device 2 connected to the print head 5. The control unit has a slicing function for the insulation layer model and controls the movement of the robotic arm 4 and the printing by the print head 5. Figure 2 As shown, the head of the robotic arm 4 is also equipped with a curing device 6 and a thickness measuring device 7, such as... Figure 2 and Figure 4 As shown, the print head 5, curing device 6 and thickness measuring device 7 are all mounted on the support disk 4a at the head of the robotic arm 4. The output direction of the print head 5, the direction of the energy emitted by the curing device 6 and the orientation of the thickness measuring device 7 are all the same and the same as the axis of the support disk 4a.

[0033] In this embodiment, the material storage device 1 is specifically a material bucket, and there are two material buckets. The two material buckets are filled with two different heat insulation materials. The heat insulation materials are in liquid or paste form before curing. In some other embodiments, the material storage device 1 is a multi-material bucket, and the specific number of material buckets can be 3, 4, 5, etc., which is suitable for printing multi-layer composite heat insulation structures.

[0034] Specifically, the thermal insulation material used in the printing system can be one or more liquid or paste-like systems, such as liquid silicone rubber system, liquid EPDM system, liquid nitrile rubber system, liquid polyurethane system, and liquid polyurea system.

[0035] Furthermore, each material barrel is equipped with a hydraulic device 3 above it. The core structure of each hydraulic device 3 is a plunger pump. The plunger pump draws the insulation material in the material barrel into the pipeline and delivers it to the mixing device 2. The plunger pump is a conventional technology, so it will not be described in detail in this article.

[0036] Furthermore, such as Figure 5 As shown, a metering device 8 is installed in the pipeline between the mixing device 2 and the storage device 1. The metering device 8 monitors and controls the flow rate or mass of the insulation material in the pipeline in real time. Specifically, based on the flow rate or mass measured by the metering device 8, the metering pump in the metering device 8 controls the mass or volume of different insulation materials delivered per unit time, thereby quantitatively controlling the proportion of different insulation materials to achieve the mixing and production of the insulation layer according to the preset ratio; it can also accurately control the extrusion rate of the mixed insulation material to prevent material interruption or blockage, and ensure the stability of the insulation material molding.

[0037] Preferably, a cooling system 9 is provided on the outer surface of the mixing device 2. In this embodiment, the cooling system 9 is a cooling water system, which is used to absorb the heat generated by the insulation material during the mixing process to prevent the insulation layer temperature from being too high, which would lead to an increase in viscosity or solidification in the mixing device 2.

[0038] Preferably, the nozzles of the printhead 5 have different shapes and sizes. The nozzle shapes of the printhead 5 include rectangular, parallelogram, triangular, trapezoidal, circular, and elliptical. Different nozzle shapes can adapt to different printing needs and solve problems related to adhesion at printing overlaps and dimensional accuracy control. For example, circular and rectangular nozzles are the most common. Circular nozzles extrude nearly cylindrical filaments, suitable for general printing; rectangular nozzles extrude wide and thin filaments, suitable for large-area filling; parallelogram nozzles can reduce the overlap area between adjacent filaments, reducing localized over-thickness caused by boundary buildup, resulting in a more uniform printing effect and increasing the boundary adhesion area for high bonding strength. The nozzle thickness of the printhead 5 is 0.1mm~5mm, and the width is 5mm~100mm. In some other embodiments, the nozzle thickness of the printhead 5 is 2.5mm, and the width is 50mm. Printhead nozzles with high thickness and large width are large-size nozzles, suitable for printing large-thickness insulation layers in the early stages; printhead nozzles with low thickness and small width are small-size nozzles, suitable for printing high-precision insulation layers in the later stages.

[0039] Specifically, such as Figure 2 , Figure 4 and Figure 6 As shown, the direction of energy emitted by the curing device 6 is consistent with the output direction of the print head 5. The energy emitted by the curing device 6 can be selected from three forms: microwave, ultraviolet light, or infrared light. By irradiating the surface of the insulation layer, the insulation layer is cured in situ. In practical applications, after each layer is printed, the curing device 6 can be used to cure the insulation layer in situ, preventing the previous insulation layer from sticking and being carried away when printing the next layer. In-situ curing of the insulation layer is achieved during the printing process, reducing the time for secondary curing of the insulation layer and shortening the manufacturing cycle of the insulation layer.

[0040] More specifically, the curing operation is divided into four modes: room temperature curing, microwave curing, ultraviolet light curing, and infrared heating curing. Room temperature curing is achieved by adjusting the proportion of curing agent in the insulation material. When room temperature curing is selected, printing and curing are carried out simultaneously, and the curing device 6 does not participate in the curing operation. When microwave curing, ultraviolet light curing, and infrared heating curing are selected, printing and curing are carried out separately, and the print head 5 stops working after the curing device 6 is started.

[0041] Specifically, the thickness measuring device 7 is a 3D scanner or a thickness gauge, such as... Figure 2 , Figure 4 and Figure 6 As shown, the orientation of the 3D scanner or thickness gauge is consistent with the output direction of the print head. The thickness measuring device 7 can measure the thickness of the currently printed insulation layer and compare it with the 3D model of the insulation layer. The comparison result is transmitted to the robotic arm system, which automatically adjusts the process parameters and continues printing in areas where the thickness does not meet the requirements. The above operation is repeated until the dimensions of the insulation structure meet the requirements, ensuring the printing effect of the insulation layer.

[0042] More specifically, both the 3D scanner and the thickness gauge utilize existing technologies: the 3D scanner can be the Shining Tianyuan FreeScan Trak Pro2 industrial-grade 3D scanner, which uses laser scanning to scan the insulation surface before and after molding, generating a 3D point cloud map. The thickness of the insulation layer is obtained by comparing the 3D point cloud map. The thickness gauge can be the Keyence LJ-X8000 laser measuring instrument, which uses a cylindrical objective lens to diffuse the laser into a line laser and projects it onto the surface of the target object to form diffuse reflection. After the reflected light is imaged on a CMOS, the thickness of the insulation layer is measured by detecting changes in position and shape. In this embodiment, a thickness gauge is selected as the thickness measuring device 7.

[0043] Specifically, the composite solid rocket motor insulation layer 3D printing system also includes a rotating fixture 10, which is used to fix and rotate the solid rocket motor core mold 11, such as... Figure 7 As shown, the core mold 11 consists of end caps 11a at both ends and a cylindrical section 11b in the middle. The end caps 11a are partially hemispherical, and the cylindrical section 11b is cylindrical. The diameter of the bottom of the end caps 11a is equal to the diameter of the cylindrical section 11b. The rotating fixture 10 fixes and rotates the end caps 11a of the core mold 11 from both ends.

[0044] More specifically, the hydraulic device 3, the robotic arm system, and the rotating tooling 10 are all controlled from the operator console 12. Optionally, the operator console 12 is equipped with a control panel touch screen for actual control.

[0045] Optionally, the solid rocket motor core mold 11 can be a plaster core mold, a sand core mold, or a metal core mold. After the insulation layer and outer shell are made, the plaster core mold is demolded by breaking it, the sand core mold is demolded by washing it with water, and the metal core mold is demolded through a detachable structure.

[0046] Optionally, a cable tray 14 is provided on the base 13 where the composite solid rocket motor insulation layer 3D printing system is located. The cables used by the printing system to connect to the power supply or other external equipment are laid in the inner groove of the cable tray 14 to avoid various safety hazards caused by direct exposure of cables and improve the safety of the system.

[0047] A method for 3D printing a composite solid rocket motor insulation layer, applied to a composite solid rocket motor insulation layer 3D printing system, includes the following steps: S1: Fix the solid rocket motor core mold 11 onto the rotating fixture 10. The core mold 11 has a diameter of 50cm. Set the rotation speed of the rotating fixture 10 to 20r / min. Input the three-dimensional model of the insulation layer into the robotic arm system. Set the single-layer slice thickness to 0.1-1mm. The control unit slices the insulation layer layer by layer to generate a slice image. S2: Place the different insulation materials after defoaming into multiple storage devices 1, set the mixing ratio to 1:1, turn on the cooling system 9 of the mixing device 2, control the water temperature of the cooling water system to ≤10℃, and control the feeding speed of the hydraulic device 3 to 471cm through the metering device 8. 3 / min.

[0048] S3: Select the nozzle shape and size of printhead 5. The nozzle shape of printhead 5 is a parallelogram with a thickness of 1mm and a width of 15mm. Start the feeding system for trial operation until the nozzle of printhead 5 outputs material evenly, then turn off the feeding system.

[0049] S4: The walking angle and speed of the robotic arm 4 are set by the control unit. The robotic arm 4 drives the print head 5 to walk on the core model surface to print the insulation layer, and prints in the order of end cap 11a-column segment 11b-end cap 11a.

[0050] S5: After the print head 5 prints 1 layer, start the curing device 6, select the infrared heating curing mode, turn on the infrared heating lamp, control the heating temperature to 80-120℃, and the robotic arm 4 drives the curing device 6 to move along the core model surface to heat and cure the insulation layer. At this time, the axial movement speed of the robotic arm 4 is 30cm / min. S6: Repeat S4 and S5. Every 5 layers printed, activate the thickness measuring device 7 to detect the thickness of the insulation layer and compare it with the 3D model of the insulation layer. Transmit the comparison result to the robotic arm system. Continue printing on areas where the thickness does not meet the requirements. Repeat the above operation until the insulation layer size meets the requirements.

[0051] Preferably, in the aforementioned operation method, "selecting the nozzle shape and size of the print head 5" means that for a thick insulation layer, a large nozzle is used for printing in the early stage, and when the printing reaches the required size, the nozzle is switched to a small nozzle for printing.

[0052] Specifically, the "print head 5 walking along the core model surface" in the aforementioned operation method refers to the following: the print head 5 walks along the shape of the solid rocket motor core model 11, and the print head 5 always maintains a fixed walking angle with the surface of the core model 11. The walking of the print head along the core model surface can generate a certain pressure on the insulation layer, thereby improving the density of the insulation layer and the interlayer bonding strength.

[0053] More specifically, the robotic arm 4 drives the print head 5 to move along the core mold surface to print the insulation layer. The angle between the print head 5 and the core mold 11 is the walking angle, which is 30°~90°. When the walking angle is less than 90°, the print head 5 generates a certain pressure while printing the insulation material, which is beneficial to improving the interlayer bonding strength of the insulation material.

[0054] In practical applications, the diameter D of the core mold 11 and the rotation speed V of the rotating fixture 10 need to be controlled during the printing process.R The nozzle cross-sectional area S of the print head 5 and the feeding speed V1 of the feeding system are matched to prevent the insulation layer from being too thick or too thin in some areas; it is also necessary to control the axial travel speed V2 of the print head 5 along the core mold 11 and the rotation speed V of the rotating fixture 10. R The nozzle width L of the printhead 5 must be matched to prevent wrinkles and burrs from forming at the overlap of the insulation layer. The two matching relationships must satisfy the following formula: S (1) (2) in ,like Figure 7 As shown, Z is the shortest distance between the printing position and the column segment 11b when the print head 5 prints on the end cap 11a of the mandrel 11. Therefore Z is the diameter of the cross-sectional circle where the printing position is located; when print head 5 prints on column segment 11b, Z=0. D, Formulas (1) and (2) can be simplified to: S (3) (4) When printing in the order of head 11a - column segment 11b - head 11a, Z first gradually decreases to 0, then remains constant, and then gradually increases. The corresponding value gradually increases to D, then remains constant, and then gradually decreases. The dynamic adjustment during this period is achieved by adjusting the rotation speed V using the rotating fixture 10. R accomplish.

[0055] Specifically, formulas (1) and (3) refer to the fact that within the time range during which the rotating fixture 10 rotates the core mold 11 one revolution, the volume of the heat insulation material output by the print head 5 is equal to the volume of the heat insulation material covering the core mold 11 one revolution, thereby ensuring that the heat insulation material is printed evenly on the surface of the core mold 11; formulas (2) and (4) refer to the fact that the time during which the rotating fixture 10 rotates the core mold 11 one revolution is equal to the time during which the print head 5 moves axially by the width of a nozzle, thereby ensuring that there are no gaps between adjacent printing areas when rotating to print the insulating material.

[0056] Based on the specific data provided in the operating instructions, taking the printing process of the column segment area as an example: feeding speed V1 = 471cm 3 / min, rotational speed V of rotating fixture 10 R =20r / min, π = 3.14, core mold 11 diameter D = 50cm, S = 1 × 15 = 15mm 2 (0.15cm) 2The width L of the printhead 5 is 15mm (1.5cm), and the axial travel speed V2 is 30cm / min. Substituting these values ​​into formulas (3) and (4) yields the results, which both satisfy the condition. It was also found that when the diameter D of the core mold 11 differs significantly from the nozzle width L of the printhead 5, and The numerical differences are even greater. Negligible, the formula (3) for printing column segments can be further simplified to: S (5) When the diameter D of the core mold 11 is relatively close to the value of the nozzle width L of the print head 5, the influence of the nozzle width L on the calculation result needs to be considered, and the matching relationship is still calculated using formula (3).

[0057] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0058] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A method for 3D printing a composite solid rocket motor insulation layer, characterized in that, The operation method is applied to a 3D printing system for the thermal insulation layer of a composite solid rocket motor, the system comprising: The feeding system includes a storage device (1), a mixing device (2) and a hydraulic device (3). There are multiple storage devices (1), and the mixing device (2) is connected to multiple storage devices (1) by pipes. The hydraulic device (3) transports the insulation material in the storage device (1) to the mixing device (2) through the pipes. The robotic arm system includes a robotic arm (4) and a control unit. The head of the robotic arm (4) is provided with the mixing device (2) and the printing head (5), and the mixing device (2) is connected to the printing head (5). The control unit has the function of slicing the insulation layer model and controls the movement of the robotic arm (4) and the printing head (5) to print. The head of the robotic arm (4) is also provided with a curing device (6) and a thickness measuring device (7). A metering device (8) is provided at the pipe between the mixing device (2) and the storage device (1), and a cooling system (9) is provided on the outer surface of the mixing device (2). It also includes a rotating fixture (10) for fixing and rotating a solid rocket motor core mold (11). The core mold (11) consists of end caps (11a) at both ends and a cylindrical section (11b) in the middle. The end caps (11a) at both ends are partially hemispherical, and the cylindrical section (11b) is cylindrical. The diameter of the bottom of the end caps (11a) is equal to the diameter of the cylindrical section (11b). The method includes the following steps: S1: Fix the solid rocket engine core mold (11) onto the rotating fixture (10), set the rotation speed of the rotating fixture (10), input the three-dimensional model of the insulation layer into the robotic arm system, set the single-layer slice thickness, and the control unit slices the insulation layer layer by layer to generate a slice image. S2: Place the different insulation materials after defoaming into multiple storage devices (1), set the mixing ratio, turn on the cooling system (9) of the mixing device (2), and control the feeding speed of the hydraulic device (3) through the metering device (8); S3: Select the nozzle shape and size of the print head (5), start the feeding system for trial operation until the nozzle of the print head (5) outputs material evenly, and then turn off the feeding system; S4: The walking angle and speed of the robotic arm (4) are set by the control unit, and the robotic arm (4) drives the print head (5) to walk on the core model surface to print the insulation layer; S5: After the print head (5) prints 1 layer, the curing device (6) is started, the curing mode is selected, and the robotic arm (4) drives the curing device (6) to move along the core model surface to cure the insulation layer. S6: Repeat S4 and S5. Every 5 layers are printed, start the thickness measuring device (7) to detect the thickness of the insulation layer and compare it with the three-dimensional model of the insulation layer. Transmit the comparison result to the robotic arm system. Continue printing on areas where the thickness does not meet the requirements. Repeat the above operation until the size of the insulation layer meets the requirements. During the printing process, the diameter D of the core mold (11) and the rotation speed V of the rotating fixture (10) need to be controlled. R The nozzle cross-sectional area S of the print head (5) and the feeding speed V1 of the feeding system are matched; the axial travel speed V2 of the print head (5) along the core mold (11) and the rotation speed V of the rotating tooling (10) are also controlled. R The nozzle width L of the print head (5) must be matched with each other to satisfy the following formula: ， in Z is the shortest distance between the printing position and the column segment (11b) when the print head (5) prints on the end cap (11a) of the core mold (11). Z is the diameter of the cross-sectional circle where the printing position is located; when the print head (5) prints on the column segment (11b), Z=0. The two formulas above can be simplified to: 。 2. The method for 3D printing the thermal insulation layer of a composite solid rocket motor according to claim 1, characterized in that, The nozzles of the print head (5) have different shapes and sizes. The nozzle shapes of the print head (5) include rectangular, parallelogram, triangular, trapezoidal, circular and elliptical. The nozzle thickness of the print head (5) is 0.1mm~5mm and the width is 5mm~100mm.

3. The method for 3D printing the thermal insulation layer of a composite solid rocket motor according to claim 1, characterized in that, The direction of energy emitted by the curing device (6) is consistent with the output direction of the print head (5). The energy emitted by the curing device (6) can be selected from one of three forms, including microwave, ultraviolet light or infrared light.

4. The method for 3D printing the thermal insulation layer of a composite solid rocket motor according to claim 1, characterized in that, The thickness measuring device (7) is specifically a three-dimensional scanner or a thickness gauge, and the orientation of the three-dimensional scanner or the thickness gauge is consistent with the output direction of the print head (5).

5. The method for 3D printing the thermal insulation layer of a composite solid rocket motor according to claim 1, characterized in that, The selection of the nozzle shape and size of the print head (5) involves using a large nozzle for printing in the early stages for thick insulation layers, and switching to a small nozzle when the print head is close to the required size.

6. The method for 3D printing the thermal insulation layer of a composite solid rocket motor according to claim 1, characterized in that, The robotic arm (4) drives the print head (5) to walk along the core mold surface to print the insulation layer. The angle between the print head (5) and the core mold (11) is the walking angle, which is 30°~90°.

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