Grafting forming multi-stage valve and method

Abstract

The invention discloses a multi-stage valve formed by grafting and a method, and relates to the technical field of hydraulic control element manufacturing, and the method comprises the following steps: correcting a grafting surface of a pilot-stage servo valve, and assembling internal parts of the pilot-stage servo valve; a closing plug is arranged in the channel close to the grafting surface, and a pilot-level servo valve is installed on the clamping tool and leveled; forming a supporting auxiliary structure with the same height as the grafting surface, and leveling; adjusting the grafting surface of the pilot-stage servo valve and the end face of the supporting auxiliary structure of the output-stage servo valve to be located at the vertical zero position of the forming platform; the visual identification and laser contour scanner determines that positioning points of an additive manufacturing forming section coordinate system and a grafting surface coordinate system coincide; forming an output-stage servo valve main body on the grafting surface layer by layer; cleaning the blank, performing destressing heat treatment, and performing finish machining; the closure plug is removed. The multi-stage servo valve has the advantages that on the basis that the stable control mode of the multi-stage servo valve is reserved, the number of parts of the multi-stage servo valve is reduced, and larger flow is achieved with the smaller size of the servo valve.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic control element manufacturing, in particular to a grafted multi-stage valve and method. BACKGROUND

[0002] Traditional servo valves mostly use two-stage structure, and also have three-stage structure, and have a large number of parts that need to be precisely machined, which has high manufacturing difficulty and high maintenance cost; the process limitation of machining itself makes the overall volume of the large-flow servo valve large.

[0003] The transmission mode of the traditional servo valve using the coil to cause the magnet to deflect can realize the application of the servo valve under high-temperature conditions at a lower cost; And the direct-drive valve is integrally formed by additive manufacturing, and has high control precision, but due to the existence of the PCBA (printed circuit board), higher and more expensive electronic components need to be used for high-temperature resistance.

[0004] Both of them are difficult to meet the composite needs of small size, high-temperature resistance and low cost under extreme working conditions. SUMMARY

[0005] The main purpose of the present application is to provide a grafted multi-stage valve and method, which aims to solve the problem of small size, high-temperature resistance and low cost of servo valves under extreme working conditions.

[0006] In order to achieve the above-mentioned purpose, the present application provides a grafted multi-stage valve and method, which comprises the following steps: S1, correcting the grafting surface of the pilot stage servo valve, and assembling the internal parts of the pilot stage servo valve; S2, setting a closing plug in the channel of the pilot stage servo valve close to the grafting surface, the thickness of the closing plug is less than the length of the unchanged cross-section section of the flow passage and the whole is lower than the grafting surface plane, the pilot stage servo valve is installed in the clamping tool, and the grafting plane of the pilot stage servo valve is leveled; S3, according to the model topology analysis of the output stage servo valve, forming a support auxiliary structure with the same height as the grafting surface, and pre-clamping in the clamping tool and leveling; S4, adjusting the end faces of the grafting surface of the pilot stage servo valve and the support auxiliary structure of the output stage servo valve to be at the vertical zero point position of the forming platform; S5, the visual recognition system captures the flow passage profile of the grafting surface, and compares it with the slice of the additive data model; the laser profile scanner locates the center of the flow passage hole, and determines that the additive manufacturing forming cross-section coordinate system and the grafting surface coordinate system positioning points coincide; S6, laser cladding high-temperature alloy powder on the grafting surface, and forming the output stage servo valve body layer by layer; S7, cleaning the blank and stress relief heat treatment, finishing; removing the closing plug in the pilot stage servo valve, and then cleaning the grafting assembly.

[0007] In an embodiment, the step S1: the planeness of the grafting surface of the pilot stage servo valve is not greater than 0.1 mm, and the roughness is not greater than 3.2 μm.

[0008] In an embodiment, the step S2: the closure plug is of a segmented or integral structure. Segmented: rubber frame with embedded metal / ceramic platelets, or adhesively connected plastic platelets. Integral: using a fusible material (at least one of PTFE (polytetrafluoroethylene) wax, PEEK (polyether ether ketone) wax, high phenyl silicone wax, or fluorine wax) higher than the temperature of the additive grafting forming base plate and lower than the temperature interval of the additive forming grafting component stress relief heat treatment.

[0009] In an embodiment, the segmented closure plug is connected by a metal chain, and the segmented closure plug is dispersedly separated from the flow channel by pulling.

[0010] In an embodiment, the support auxiliary structure in the step S3 is a cylinder, a square column, or an irregular straight column, and the material of the support auxiliary structure is similar to that of the additive part (difference in coefficient of thermal expansion ≤ 3 ppm / ℃).

[0011] In an embodiment, the positioning of the step S5 includes: Laser pre-scanning verification (power < 20 W), repeated adjustment 2-3 times until the profiles coincide; The accuracy of the flow channel port profile identification reaches ± 10 μm.

[0012] In an embodiment, the additive forming parameters of the step S6 include: Grafting transition layer 1-5 layers, each layer is remelted 0-3 times (the remelting mode is to re-powder scanning or direct scanning without powder); Forming density ≥ 99.5%; The support structure and the auxiliary structure are connected at 1-5 layers.

[0013] In an embodiment, the step S7, the cleaning method is at least one of compressed air cleaning, explosion-proof dust collector cleaning, or ultrasonic cleaning, and the cleaning method is at least one of high-pressure cleaning, electrochemical cleaning, oil immersion, or rinsing.

[0014] In an embodiment, a plurality of parts are installed on the output stage servo valve, and the plurality of parts include a valve sleeve, a valve core, and an end cover.

[0015] A grafting formed multi-stage valve is prepared by the method described above.

[0016] The technical scheme of the present application is characterized in that after the precision correction of the pilot stage servo valve is grafted with a surface and the internal assembly is completed, a closed plug is implanted into the flow channel on the grafted surface to isolate the additive pollution; then the grafted surface is leveled by a clamping tool, and a support auxiliary structure with the same height as the grafted surface is prepositioned to stabilize the output stage servo valve surface. In the forming stage, the visual recognition system cooperates with the laser profile scanner to position, compare the profile of the grafted surface flow channel with the additive data model slice, and make the coordinate systems coincide; then the laser cladding of high-temperature alloy powder is carried out on the grafted surface, and the output stage servo valve body is stacked layer by layer, and the transition layer is remelted for 1-5 times to ensure that the interface density is greater than or equal to 99.5%. Finally, after stress relief heat treatment and finishing, the closed plug is removed, the high-temperature transmission mechanism of the pilot stage servo valve is integrated with the topologically optimized flow channel of the output stage servo valve, the bottleneck problems of large volume of traditional valve and high-temperature failure of PCBA of direct drive valve are solved at the same time, the number of parts of the multi-stage servo valve is reduced, the qualified rate of the product is improved at a smaller cost, and a larger flow can be realized with a smaller servo valve volume. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and other drawings can also be obtained according to the structures shown in the drawings without creative labor.

[0018] Figure 1 A flow chart of an embodiment of a grafting and forming multi-stage valve method provided by the present application; Figure 2 A front view structural schematic diagram in an embodiment of a grafting and forming multi-stage valve provided by the present application; Figure 3 A three-dimensional structural schematic diagram of a pilot stage servo valve grafting surface in an embodiment of a grafting and forming multi-stage valve and method provided by the present application; Figure 4 A three-dimensional structural schematic diagram of an output stage servo valve in an embodiment of a grafting and forming multi-stage valve and method provided by the present application; Figure 5 A left view schematic diagram of a pilot stage servo valve mounted on a clamping tool in an embodiment of a grafting and forming multi-stage valve and method provided by the present application; Figure 6 A top view schematic diagram of a pilot stage servo valve mounted on a clamping tool in an embodiment of a grafting and forming multi-stage valve and method provided by the present application; Figure 7 A three-dimensional schematic diagram of a clamping tool and a support auxiliary structure in an embodiment of a grafting and forming multi-stage valve and method provided by the present application; BRIEF DESCRIPTION OF DRAWINGS 1. Pilot stage servo valve; 2. Output stage servo valve; 3. Closing plug; 4. Clamping tool; 5. Support auxiliary structure.

[0019] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments in combination with the accompanying drawings. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0021] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications also change accordingly. Unless otherwise specified and limited, the terms “mounting”, “connection”, “connecting” should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral connection; can be mechanical connection, can also be electrical connection; can be direct connection, can also be indirect connection through an intermediate medium, or can be internal communication of two elements. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0022] In addition, if the description involves "first", "second" and the like in the embodiments of the present application, the description of "first", "second" and the like is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can be explicitly or implicitly included at least one of the features. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or equipment including the element. In addition, if "and / or" or "and / or" appears throughout the text, it means that the three parallel schemes are included, for example, "A and / or B" includes A scheme, or B scheme, or A and B scheme. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of the person skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor within the scope of protection required by the present application.

[0023] A grafting shaped multi-stage valve and method, comprising the following steps: S1, correct the grafting surface of the pilot stage servo valve 1, precisely grind the low roughness plane to reduce the interface micro gap, ensure the tight fit of the additive output stage servo valve 2 and the pilot stage servo valve 1 sealing interface, assemble the internal parts of the pilot stage servo valve 1; S2, set a closure plug 3 in the channel of the pilot stage servo valve 1 near the grafting surface, the thickness of the closure plug 3 is less than the length of the unchanged section of the flow channel and the whole is lower than the grafting surface plane, install the pilot stage servo valve 1 in the clamping tool 4, and adjust the grafting plane of the pilot stage servo valve 1; the thickness of the closure plug 3 is less than the length of the vertical section of the flow channel, ensuring that the plug body is completely embedded in the non-variable section area; the metal chain pulls the split plug to split and adapt to the complex flow channel cleaning.

[0024] S3, according to the model topology analysis of the output stage servo valve 2, shape the support auxiliary structure 5 with the same height as the grafting surface, and pre-clamp in the clamping tool 4 and adjust the level; the difference between the thermal expansion coefficients of the cylindrical / square cylindrical straight body support auxiliary structure 5 and the output stage servo valve 2 is ≤3ppm / ℃, which inhibits the thermal deformation in the additive process.

[0025] S4, adjust the end face of the grafting surface of the pilot stage servo valve 1 and the support auxiliary structure 5 of the output stage servo valve 2 to be at the vertical zero point position of the shaping platform; S5, the visual recognition system captures the contour of the grafting surface flow channel and compares it with the slice of the additive data model; the laser profile scanner locates the flow channel hole center to determine that the additive manufacturing shaping cross-section coordinate system coincides with the grafting surface coordinate system positioning point; the visual recognition extracts the flow channel edge feature points and fits them with the additive slice data; S6, laser cladding high-temperature alloy powder on the grafting surface to form the output stage servo valve 2 body layer by layer; the transition layer 1-5 layers are remelted (0-3 times) to improve the interface density and tensile strength; the support structure and the auxiliary structure connection are remelted to eliminate interlayer porosity.

[0026] S7, clean the blank and perform stress relief heat treatment and finishing; remove the closure plug 3 in the pilot stage servo valve 1, and then clean the grafting assembly.

[0027] In an embodiment, in step S1: the flatness of the grafting surface of the pilot stage servo valve 1 is not greater than 0.1 mm, and the roughness is not greater than 3.2 μm.

[0028] In an embodiment, in step S2: the closure plug 3 is of a split type or an integral type; Split type: rubber frame with embedded metal / ceramic plate, or plastic plate connected by adhesive; Integral type: using a fusible material (at least one of PTFE (polytetrafluoroethylene) wax, PEEK (polyether ether ketone) wax, high phenyl silicone wax, or fluorine wax) higher than the temperature of the additive grafting forming substrate and lower than the stress relief heat treatment temperature interval of the additive forming grafting assembly.

[0029] In an embodiment, the split type closure plug 3 is connected with a metal chain to disperse and separate the split type closure plug 3 from the flow channel by pulling.

[0030] In an embodiment, the support auxiliary structure 5 in step S3 is a cylinder, a square column, or an irregular straight column, and the material of the support auxiliary structure 5 is similar to that of the additive part (difference in thermal expansion coefficient ≤3 ppm / ℃).

[0031] In an embodiment, the positioning of step S5 includes: laser pre-scanning verification (power <20W), repeated adjustment 2-3 times until the profile coincides; The accuracy of the flow channel port profile recognition reaches ±10 μm.

[0032] In an embodiment, the additive forming parameters of step S6 include: Grafting transition layer 1-5 layers, each layer is remelted 0-3 times (the remelting method is to re-powder and scan or directly scan without powder); The forming density is ≥99.5%; The support structure and the auxiliary structure connection are remelted 1-5 layers.

[0033] In an embodiment, in step S7, the cleaning method is at least one of compressed air cleaning, explosion-proof vacuum cleaner cleaning, or ultrasonic cleaning, and the cleaning method is at least one of high-pressure cleaning, electrochemical cleaning, oil immersion, or rinsing.

[0034] In an embodiment, a plurality of parts are mounted on the output stage servo valve 2, and the plurality of parts include a valve sleeve, a valve core, and an end cover.

[0035] A grafted multi-stage valve is prepared by the method.

[0036] The above-mentioned content related to the preferred embodiment is described as follows: A grafting method of a multi-stage valve includes the following steps: S1, machining the parts of the hydraulic servo valve pilot stage servo valve 1, especially the grafting surface of the pilot stage servo valve 1 and the output stage servo valve 2 is planed, the pilot stage servo valve 1 is assembled, and the pilot stage servo valve 1 is assembled; S2, the channel connected to the hydraulic system inside the assembled pilot stage servo valve 1 is closed and protected, the pilot stage servo valve 1 is installed on the clamping tool 4, and the grafting plane of the pilot stage servo valve 1 is adjusted by adjusting the clamping tool; S3, analyzing the support auxiliary structure 5 required for grafting and forming the main part of the hydraulic servo valve output stage servo valve 2, separately forming the support auxiliary structure 5, and pre-clamping and leveling it on the same clamp; S4, lowering the forming platform so that the grafting surface and the end surface of the support auxiliary structure 5 are at the zero point position of the forming platform height axis (Z axis), and verifying the parallelism of the grafting surface and the powder laying plane by thin layer powder laying; S5, using visual identification to identify the key flow channel profile of the grafting surface, comparing and coinciding with the grafting additive data file slice, using the laser profile pre-scanning system to confirm the position of the flow channel hole of the grafting surface, and determining that the additive manufacturing forming cross-section coordinate system coincides with the positioning point of the grafting coordinate system; S6, additive manufacturing of the hydraulic servo valve output stage servo valve 2; S7, taking out the formed part, performing powder cleaning, stress relief heat treatment, and local finishing on the formed output stage servo valve 2 blank, the finished part should be simply cleaned, the closed protection rubber plug structure of the channel part of the pilot stage servo valve 1 is taken out after one cleaning, and the grafting assembly is cleaned to obtain the hydraulic servo valve product main part; S8, assembling the valve sleeve, valve core, end cover, and other parts to the hydraulic servo valve main part to obtain the hydraulic servo valve product.

[0037] In an embodiment, in step S1, the grafting surface of the pilot stage servo valve 1 is a plane with a flatness of no more than 0.1 mm and a roughness of no more than 3.2 μm, and the grafting surface has a clearly identifiable flow channel port profile.

[0038] In an embodiment, in step S2, the channel protection of the pilot stage servo valve 1 is to add a closure plug 3 at the position of the non-constant cross-section pipe of the pilot stage servo valve 1 close to the grafting plane, and the closure plug 3 has the following characteristics: The thickness of the closure plug 3 should be less than the length of the non-constant cross-section and non-bent section of the liquid flow channel close to the outlet section of the grafting surface; After the closure plug 3 is inserted into the non-constant cross-section and non-bent section of the flow channel, any part is lower than the plane of the grafting surface; The closure plug 3 needs to be removed from the flow channel of the output stage servo valve 2 with a larger diameter than the pilot stage servo valve 1 after the grafting is completed, and the closure plug 3 is in blocks or as a whole; The block-type closure plug 3 is a rubber frame with an embedded small plate or a small plate using adhesive connection, and the small plate material is metal, plastic or ceramic; The whole-type closure plug 3 is a material that can be melted at a temperature higher than the temperature of the additive grafting forming base plate and lower than the stress relief heat treatment temperature interval of the additive forming grafting assembly, including but not limited to one or more of PTFE (polytetrafluoroethylene) wax, PEEK (polyether ether ketone) wax, high phenyl silicone wax, fluorine wax and the like; The closure plug 3 can be connected to a metal chain, which facilitates the dispersion of the block-type closure plug 3 in the formed grafting assembly by pulling the metal chain, so as to be cleaned; The closure plug 3 can prevent the internal flow channel and transmission structure of the pilot stage servo valve 1 which has been precisely machined from being contaminated and rubbed by metal raw material powder during the grafting process.

[0039] In an embodiment, in step S3, when the support auxiliary structure 5 for the grafted output stage servo valve 2 has a scanning area larger than the grafting surface area of the pilot stage servo valve 1 and the model of the output stage servo valve 2 presents a real slope with a corresponding increased area in the 3D space, the angle between the forming plane and the slope is less than 45°, the support auxiliary structure 5 needs to be designed in advance to be clamped at the same height as the grafting surface, and the support for supporting the output stage servo valve 2 can be printed layer by layer from these support auxiliary structures 5 to support the low-angle slope of the output stage servo valve 2. The pre-clamped support auxiliary structure 5 is a cylindrical, square or irregular column similar to the material of the additive grafting part.

[0040] In an embodiment, in steps S2 and S3, the bottom of the clamping tool 4 is fixed on the forming base plate, which is made of the same material as the forming base plate, and the upper part of the clamping tool 4 has multiple grooves for installing the auxiliary support structure columnar objects and clamping devices, and there is a clamping tool 4 module customized for the pilot stage servo valve 1, the lower end of the clamping tool 4 module is a sliding rail, which can slide in the X and Y directions of the forming plane, and the height of a single clamping point in the clamping tool 4 module can also be adjusted. In an embodiment, in step S5, the device photographs and identifies the contour and channel outlet position of the leveled pilot stage servo valve 1, adjusts the starting layer cross-section data position of the grafted data file, so that the grafted data channel outer contour coincides with the outer contour of the clamped pilot stage servo valve 1 channel, and uses a laser scan with a power lower than 20W to graft the starting layer data contour, and actually verify the coincidence degree of the grafted position with the pilot stage servo valve 1. After adjusting 2-3 times, there is no machine image recognition and naked eye recognition error between the scan contour and the actual contour, and the grafting printing can begin. In an embodiment, in step S6, the main process parameters for additive manufacturing of the output stage servo valve 2 valve body are: the number of times of remelting of the grafting transition layer and the remelting laser parameters, the grafting part forming parameters, and the design and forming parameters of the grafting part support auxiliary structure 5, wherein: The grafting transition layer is generally 1-5 layers, and each layer is remelted 0-3 times; The remelting uses a method of re-laying the original material once without changing the height of the forming platform, or a method of re-scanning once without re-laying the original material once; The forming parameters of the grafted part use parameters corresponding to the material, and the printing forming density is greater than 99.5%; The grafting part auxiliary structure is connected with the pre-clamped support auxiliary structure 5, and the connection is also subjected to 1-5 layers of remelting, and the number of times of remelting is generally 0-3 times.

[0041] In an embodiment, in step S7, after the grafted assembly is completed after powder cleaning, stress relief heat treatment and finishing, it should be cleaned, and then physically or chemically split the closed plug 3 into small pieces or liquefied to flow out, and finally cleaned, wherein: The cleaning method is compressed air cleaning, explosion-proof dust collector cleaning or ultrasonic cleaning, etc.; The cleaning method is high-pressure cleaning, electrochemical cleaning, oil immersion or leaching, etc.

[0042] Through grafting the face of the precision correction pilot stage servo valve 1 after the internal assembly is completed, implanting the closed plug 3 on the flow channel of the grafting face to isolate the additive pollution, then leveling the grafting face through the clamping tool 4, and prepositioning the support auxiliary structure 5 which is in the same height with the grafting face to stabilize the output stage servo valve 2 face. In the forming stage, the visual identification system cooperates with the laser profile scanner to position, compares the profile of the flow channel of the grafting face with the additive data model slice, and makes the coordinate systems coincide; then laser cladding high-temperature alloy powder on the grafting face, layer by layer stacking the output stage servo valve 2 body, during which the transition layer is remelted 1-5 times to ensure that the interface density is greater than or equal to 99.5%. Finally, after stress relief heat treatment and finishing, the closed plug 3 is removed, realizing the integration of the high-temperature resistant transmission mechanism of the pilot stage servo valve 1 and the topologically optimized flow channel of the output stage servo valve 2, synchronously solving the bottleneck problem of the large volume of traditional valve and the high-temperature failure of PCBA of direct drive valve, reducing the number of parts of multi-stage servo valve, improving the qualified rate of products at a smaller cost, and realizing larger flow with smaller servo valve volume.

[0043] It should be understood that the "one embodiment" or "one example" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the application. Therefore, "in one embodiment" or "in an example" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. Those skilled in the art should also know that the embodiments described in the specification are optional embodiments, and the actions and modules involved are not necessarily required by the application.

[0044] In various embodiments of the application, it should be understood that the size of the serial number of the above processes does not mean the inevitable sequence of execution order, and the execution order of each process should be determined according to its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the application.

[0045] The computer program product of the present application can be a computer program implemented on one or more computers. The program segments / computer instructions can be stored in a tangible computer usable medium, or transmitted from a computer data signal, or floppy disk accompanying the application, and comprise a number of computer readable program segments designed to implement the methods of the application. The medium can be a magnetic disk, optical disk, or any other suitable medium. The program segments can be downloaded over a network from an on-line service provider or an Internet source. The program segments can also be embodied in a computer readable signal directed to an appropriate computer system, which interprets the information contained therein.

[0046] The above description is only exemplary implementation of the present application, and is not intended to limit the patent scope of the present application. Any equivalent structural transformation made in the technical concept of the present application, or direct / indirect application in other related technical fields, using the content of the present application specification and drawings, is included in the patent protection scope of the present application.

Claims

1. A method of grafting a shaped multi-stage valve, characterized by, The method comprises the following steps: S1, modifying the grafting surface of the pilot stage servo valve (1), and assembling the internal parts of the pilot stage servo valve (1); S2, arranging a closure plug (3) in the passage of the pilot stage servo valve (1) close to the grafting surface, the thickness of the closure plug (3) being less than the length of the unchanged cross-section section of the flow passage and the whole being lower than the grafting surface plane, mounting the pilot stage servo valve (1) on a clamping tool (4), and leveling the grafting plane of the pilot stage servo valve (1); S3, according to the model topology analysis of the output stage servo valve (2), forming a support auxiliary structure (5) with the same height as the grafting surface, and pre-clamping the support auxiliary structure (5) on the clamping tool (4) and leveling; S4, adjusting the grafting surface of the pilot stage servo valve (1) and the end surface of the support auxiliary structure (5) of the output stage servo valve (2) to be at the vertical zero point position of the forming platform; S5, a visual recognition system captures the flow passage profile of the grafting surface and compares it with the slice of the additive data model; a laser profile scanner locates the flow passage hole center to determine that the additive manufacturing forming cross-section coordinate system and the grafting surface coordinate system positioning points coincide; S6, laser cladding high-temperature alloy powder on the grafting surface to form the output stage servo valve (2) body layer by layer; S7, cleaning the blank and stress relief heat treatment and finishing; removing the closure plug (3) in the pilot stage servo valve (1), and then cleaning the grafting assembly.

2. A method of forming a multi-stage valve by grafting as defined in claim 1, wherein In the step S1, the flatness of the grafting surface of the pilot stage servo valve (1) is not greater than 0.1 mm, and the roughness is not greater than 3.2 μm.

3. A method of forming a multi-stage valve by grafting as defined in claim 1, wherein In the step S2, the closure plug (3) is of a block type or an integral type; The block type is a rubber frame with an embedded metal / ceramic plate, or a plastic plate connected by adhesive; The integral type is a fusible material (at least one of PTFE (polytetrafluoroethylene) wax, PEEK (polyether ether ketone) wax, high phenyl silicone wax, or fluorine wax) with a temperature higher than that of the additive grafting forming substrate and lower than that of the additive forming grafting assembly stress relief heat treatment.

4. A method of forming a multi-stage valve by grafting as defined in claim 3, characterized in that: The block type closure plug (3) is connected with a metal chain, and the block type closure plug (3) is dispersed and separated from the flow passage by pulling.

5. A method of grafting a shaped multi-stage valve as defined in claim 1, wherein: The support auxiliary structure (5) in the step S3 is a cylinder, a square column or an irregular straight column, and the material of the support auxiliary structure (5) is similar to that of the additive part (difference in thermal expansion coefficient ≤3 ppm / ℃).

6. A method of grafting a shaped multi-stage valve as defined in claim 1, characterized by: The positioning in the step S5 includes: laser pre-scanning verification (power <20 W), repeated adjustment 2-3 times until the profiles coincide; The flow passage port profile recognition accuracy is ±10 μm.

7. A method of grafting a multi-stage valve as defined in claim 1, wherein: The additive forming parameters in the step S6 include: 1-5 layers of grafting transition layer, 0-3 times of remelting of each layer (the remelting mode is to re-powder and scan or to directly scan without powder); the forming density is ≥99.5%; 1-5 layers of remelting at the connection between the support structure and the auxiliary structure.

8. A method of grafting a multi-stage valve as defined in claim 1, wherein: In the step S7, the cleaning method is at least one of compressed air cleaning, explosion-proof dust collector cleaning or ultrasonic cleaning, and the cleaning method is at least one of high-pressure cleaning, electrochemical cleaning, oil immersion or rinsing.

9. A method of grafting a multi-stage valve as defined in claim 1, wherein: Further comprising a step S8, a plurality of parts are mounted on the output stage servo valve (2), and the plurality of parts include a valve sleeve, a valve core and an end cover.

10. A grafted shaped multiple stage valve characterized by: Prepared by the method of any one of claims 1-9.

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