Method for surface weight reduction machining of special-shaped curved surfaces based on binocular structured light 3D measurement

Abstract

The present invention discloses a method for weight reduction machining of the surface of a special-shaped curved surface based on binocular structured light 3D measurement, which relates to the technical field of 3D image data processing and is used for weight reduction machining of the outer curved surface of a bent pipe. Based on the binocular structured light 3D measurement technology and combined with double high-pressure water jets, the limitations of traditional weight reduction technologies are broken through, a non-contact machining method is realized, the dependence on the geometric shape of the workpiece is reduced, and a new weight reduction solution is provided for aerospace components with complex shapes; through high-precision 3D measurement and modeling, based on the scanning recognition block and using the ICP registration algorithm, complex components are accurately reconstructed, and combined with the performance parameters of the double high-pressure water jets, accurate data support is provided for subsequent weight reduction path planning, making the weight reduction process more precise; by welding the inner half pipe and the outer half pipe into an integral bent pipe first and then performing overall weight reduction, the deformation that may occur during the weight reduction process is effectively avoided, and the dimensional stability and accuracy of the component after weight reduction are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D image data processing, and particularly to a method for machining the surface weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement. Background Art

[0002] The rocket engine elbow pipe is a bent pipe that is shaped like the spout of a teapot, with one end small and the other end large. Its material is made of superhard alloy, and its hardness and density are significantly greater than those of steel, making the material processing difficult. Due to the requirements of flow guiding, the inner wall of the elbow pipe needs to be of high precision and have a smooth and flawless surface. Therefore, during manufacturing, a process of using a mold in cooperation with forging is adopted. Specifically, the calcined alloy plate is attached to the inner mold, and through forging, the alloy plate is gradually made to completely cover the inner mold. After demolding, a special-shaped semi-pipe is obtained. On the one hand, the forging process strengthens the structural strength of the semi-pipe, and on the other hand, under the action of the inner mold, the semi-pipe can obtain a precise inner wall curved surface morphology. The expected elbow pipe is divided into two semi-pipes, and the two semi-pipes are respectively processed according to the above process, and then the two semi-pipes are welded together to obtain the expected elbow pipe.

[0003] However, since forging cannot guarantee the morphology accuracy, compared with the designed outer surface of the elbow pipe, there is a finishing allowance left on the outer surface of the elbow pipe, and its morphology shows inconsistent thickness. Therefore, it is necessary to perform weight reduction machining, that is, finishing treatment, on the outer surface of the elbow pipe to make it approach the design expectation. In the prior art, a five-axis CNC machining center is usually used to directly perform cutting treatment on the outer surface of the elbow pipe, which is time-consuming and laborious. Usually, it takes 7 days to process a set of elbow pipes, and the processing cost is high. Since the elbow pipe is made of superhard alloy, the tool is particularly consumable. The tool loss cost for processing one elbow pipe usually reaches 20,000 yuan.

[0004] Based on the above background, using a double high-pressure water jet to replace the machining center will eliminate the high tool loss cost, improve the processing efficiency at the same time, and reduce the total processing cost. However, as a new means of weight reduction machining for elbow pipes, a supporting processing method needs to be developed to fully utilize the advantages of the double high-pressure water jet weight reduction machining.

[0005] Through binocular structured light 3D measurement, the morphology of the special-shaped curved surface of the outer surface of the elbow pipe can be accurately mapped. By combining the ICP algorithm to register the morphology data of the special-shaped curved surface with the design expectation, the machining allowance of each area on the special-shaped curved surface can be obtained. Taking this as a reference, in combination with the processing parameters of the double high-pressure water jet, and combining robot offline programming and simulation machining simulation, a new weight reduction machining process method can be obtained. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for machining the surface weight reduction of the special-shaped curved surface of a rocket engine elbow pipe based on binocular structured light 3D measurement, combined with the ICP registration algorithm and applying double high-pressure water jet machining.

[0007] For the above technical problems, the technical solution adopted by the present invention is as follows: A method for machining weight reduction on the surface of a special-shaped curved surface based on binocular structured light 3D measurement, which is used for machining weight reduction on the outer curved surface of a bent pipe. The bent pipe is composed of two half pipes, and the method includes the following steps:

[0008] Step S1: Clamp and fix the half pipe with the inner curved surface of the half pipe as the reference. The fixture is provided with an outwardly convex hemispherical scanning and recognition block; the equidistant curved surface of the inner curved surface of the half pipe is used as the trajectory surface, and the binocular structured light 3D measurement camera is driven by a six-degree-of-freedom robotic arm to move along the trajectory surface to scan and obtain the global point cloud data of the outer curved surface of the half pipe and the scanning and recognition block;

[0009] Step S2: Establish a standard three-dimensional model of the half pipe and its fixture to obtain the target point cloud data of the outer curved surface of the half pipe and the scanning and recognition block. Use the ICP algorithm to perform point cloud registration on the global point cloud data and the target point cloud data of the scanning and recognition block. Based on the point cloud registration result, calculate the difference between the global point cloud data and the target point cloud data of the outer curved surface of the half pipe, that is, the thinning amount of the weight reduction machining of the half pipe;

[0010] Step S3: Perform double high-pressure water jet cutting operations on the two side surfaces of the current half pipe that are used to contact the other half pipe, and drive by a six-degree-of-freedom robotic arm to obtain a welding groove;

[0011] Step S4: Perform the operations of Step S1 to Step S3 on the two half pipes respectively, and then weld the two half pipes into a bent pipe;

[0012] Step S5: Let i = 1, 2; Clamp and fix the bent pipe with the inner curved surface of the i th half pipe as the reference. After performing robot offline programming and simulation machining simulation based on the thinning amount of the i th half pipe, drive the double high-pressure water jet by a six-degree-of-freedom robotic arm to move along the trajectory surface of the i th half pipe, and gradually complete the weight reduction of the outer curved surface of the i th half pipe;

[0013] Step S6: Detect the outer surface of the machined bent pipe, and perform local trimming on abnormal parts until the outer surface morphology of the bent pipe completely meets the target requirements.

[0014] Furthermore, the binocular structured light 3D measurement camera adopts stripe-coded structured light or speckle structured light.

[0015] Furthermore, the first half pipe is an outer half pipe, and the trajectory surface of the outer half pipe is an outer virtual surface; the second half pipe is an inner half pipe, and the trajectory surface of the inner half pipe is an inner virtual surface; Analyze and process the global point cloud data of the outer curved surface of the outer half pipe obtained through the outer virtual surface, and discretize it into mprocessing points to be machined; analyzing and processing the global point cloud data of the outer surface of the inner semi-tube obtained through the inner virtual surface, and discretizing it into n processing points to be machined; the areas of all the processing points to be machined are the same, and the area value of the processing points to be machined is less than the jet cross-sectional area of the double high-pressure water jet.

[0016] Furthermore, m + n The value of is between 12000 and 30000.

[0017] Furthermore, calculate the average thinning amount within the area of each processing point to be machined, and determine the processing parameters of the double high-pressure water jet based on the average thinning amount.

[0018] Furthermore, the double high-pressure water jet is a water-vapor-solid mixed water jet driven by high-pressure water and high-pressure gas, with abrasive particles doped in the high-pressure water; the jet cross-section of the double high-pressure water jet is circular, and the diameter of the circle is between 25 mm and 27 mm.

[0019] Furthermore, let the weight reduction removal amount per unit time of the double high-pressure water jet be Q , with the unit of mm³ / s, then there is:

[0020] ;

[0021] In the formula, K is a comprehensive coefficient, calibrated through trial processing experiments according to the material of the elbow pipe; is the volume fraction of high-pressure water, that is, the volume ratio of high-pressure water in the water jet per unit volume; is the volume fraction of abrasive particles, that is, the volume ratio of abrasive particles in the water jet per unit volume; is the density of high-pressure water, with the unit of kg / m³; is the density of abrasive particles, with the unit of kg / m³; d is the diameter of the jet cross-section of the double high-pressure water jet, with the unit of m; is the pressure of high-pressure water, with the unit of MPa; is the pressure of high-pressure gas, with the unit of MPa; is the impact angle, and the impact angle is the angle between the jet of the double high-pressure water jet and the surface normal vector of the jet action point, with the unit of rad; n is the impact angle sensitivity coefficient, calibrated through trial processing experiments according to the material of the elbow pipe; H is the hardness of the elbow pipe material, with the unit of HV; through the average thinning amount and weight reduction removal amount within the area of any processing point to be machined Q , the residence time of the double high-pressure water jet in the current processing point area can be calculated, and combined with robot offline programming and simulation processing simulation, the processing parameters are determined.

[0022] Further, the pressure of the high-pressure water is 1 - 50 MPa.

[0023] Further, the pressure of the high-pressure gas is 0.6 - 1.2 MPa.

[0024] Further, the solid-liquid ratio range of the abrasive particles to the high-pressure water is 1:0.5 to 1:10.

[0025] The beneficial effects of the present invention compared with the prior art are as follows: (1) Based on the binocular structured light 3D measurement technology, combined with double high-pressure water jets, it breaks through the limitations of traditional weight reduction technologies, realizes a non-contact processing method, reduces the dependence on the geometric shape of the workpiece, and provides a new weight reduction solution for aerospace components with complex shapes; (2) Through high-precision 3D measurement and modeling, based on the scanning recognition block, using the ICP registration algorithm, accurately reconstructs complex components, and combines with the performance parameters of the double high-pressure water jets to provide accurate data support for subsequent weight reduction path planning, making the weight reduction process more precise; (3) By welding the inner half pipe and the outer half pipe into an integral bent pipe and then performing overall weight reduction, it effectively avoids the deformation that may occur during the weight reduction process, and improves the dimensional stability and accuracy of the components after weight reduction; (4) The double high-pressure water jets apply a dual-power mode of coupling high-pressure water and high-pressure gas, improving the utilization rate of abrasives, introducing the influencing factor of cavitation effect, significantly increasing the peeling force, and reducing dust pollution by 95% while improving processing efficiency, realizing a green and environmentally friendly weight reduction processing method; (5) Eliminates the tool loss cost in traditional weight reduction technologies, greatly compresses the weight reduction processing period. Compared with the 7-day processing period of traditional weight reduction technologies, the processing period of the technology of the present invention only requires 1.5 to 2 days. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of the weight reduction processing method of the present invention.

[0027] Figure 2 It is a schematic diagram of the bent pipe structure of the present invention.

[0028] Figure 3 It is a schematic diagram of the outer half pipe structure of the present invention.

[0029] Figure 4 It is a schematic diagram of the inner half pipe structure of the present invention.

[0030] Figure 5 It is a schematic diagram of the measurement principle of the binocular structured light 3D measurement camera of the present invention.

[0031] In the figure: 1 - bent pipe; 2 - virtual plane; 101 - outer half pipe; 102 - inner half pipe; 201 - outer virtual plane; 202 - inner virtual plane. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and through specific embodiments. Among them, the accompanying drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as limiting the present invention; in order to better illustrate the embodiments of the present invention, some components in the accompanying drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0033] As Figure 1 shown, a method for weight reduction machining of the surface of a special-shaped curved surface based on binocular structured light 3D measurement is used for weight reduction machining of the outer curved surface of the bent pipe 1. The bent pipe 1 is composed of two half pipes, and includes the following steps:

[0034] Step S1: Clamp and fix the half pipe with the inner curved surface of the half pipe as the reference. The fixture is provided with an outwardly convex hemispherical scanning and recognition block; the equidistant curved surface of the inner curved surface of the half pipe is used as the trajectory surface, and the binocular structured light 3D measurement camera is driven by a six-degree-of-freedom robotic arm to move along the trajectory surface to scan and obtain the global point cloud data of the outer curved surface of the half pipe and the scanning and recognition block;

[0035] Step S2: Establish a standard three-dimensional model of the half pipe and its fixture, obtain the target point cloud data of the outer curved surface of the half pipe and the scanning and recognition block, perform point cloud registration on the global point cloud data and the target point cloud data of the scanning and recognition block through the ICP algorithm, and calculate the difference between the global point cloud data and the target point cloud data of the outer curved surface of the half pipe based on the point cloud registration result, that is, the thinning amount of the weight reduction machining of the half pipe;

[0036] Step S3: Perform double high-pressure water jet cutting operations on the two sides of the current half pipe that are used to contact the other half pipe, and drive by a six-degree-of-freedom robotic arm to obtain a welding groove;

[0037] Step S4: Perform the operations of Steps S1 to S3 on the two half pipes respectively, and then weld the two half pipes into a bent pipe 1;

[0038] Step S5: Let i = 1, 2; Clamp and fix the bent pipe 1 with the inner curved surface of the i th half pipe as the reference. After robot offline programming and simulation machining simulation based on the thinning amount of the i th half pipe, drive the double high-pressure water jet by a six-degree-of-freedom robotic arm to move along the trajectory surface of the i th half pipe, and gradually complete the weight reduction of the outer curved surface of the i th half pipe;

[0039] Step S6: Detect the outer surface of the machined bent pipe 1, and perform local trimming on the abnormal parts until the outer surface morphology of the bent pipe 1 completely meets the target requirements.

[0040] The binocular structured light 3D measurement camera uses stripe-coded structured light or speckle structured light. In this embodiment, stripe-coded structured light is used, and its schematic principle diagram is as Figure 5 shown.

[0041] As Figure 2 , Figure 3 and Figure 4 shown, the first half tube is the outer half tube 101, and the trajectory surface of the outer half tube 101 is the outer virtual surface 201; the second half tube is the inner half tube 102, and the trajectory surface of the inner half tube 102 is the inner virtual surface 202; the outer virtual surface 201 and the inner virtual surface 202 together form the virtual surface 2; the global point cloud data of the outer surface of the outer half tube 101 obtained through the outer virtual surface 201 is analyzed and processed, and discretized into m processing points to be processed; the global point cloud data of the outer surface of the inner half tube 102 obtained through the inner virtual surface 202 is analyzed and processed, and discretized into n processing points to be processed; the areas of all the processing points to be processed are the same, and the area value of the processing points to be processed is smaller than the jet cross-sectional area of the double high-pressure water jets; m + n The value of is between 12000 and 30000. In this embodiment, m The value of is 8800, n The value of is 4600; further, by calculating the average thinning amount in each area of the processing points to be processed, the processing parameters of the double high-pressure water jets are determined according to the average thinning amount; specifically, the double high-pressure water jets are water-gas-solid mixed water jets driven by high-pressure water and high-pressure gas, and abrasive particles are doped in the high-pressure water; the jet cross-section of the double high-pressure water jets is circular, and the diameter d is between 25 mm and 27 mm; let the weight reduction removal amount per unit time of the double high-pressure water jets be Q , and the unit is mm³ / s, then there is:

[0042] ;

[0043] In the formula, K is the comprehensive coefficient, which is calibrated through trial processing experiments according to the material of the elbow 1; is the volume fraction of high-pressure water, that is, the volume ratio of high-pressure water in the water jet per unit volume; is the volume fraction of abrasive particles, that is, the volume ratio of abrasive particles in the water jet per unit volume; is the density of high-pressure water, and the unit is kg / m³; is the density of abrasive particles, and the unit is kg / m³; is the pressure of high-pressure water, and the unit is MPa; is the pressure of high-pressure gas, and the unit is MPa; is the impact angle, which is the angle between the jet of the double high-pressure water jet and the surface normal vector of the jet action point, with the unit of rad; n is the impact angle sensitivity coefficient, which is calibrated through trial processing experiments according to the material of the elbow 1 and usually ranges between 1 and 2; H is the hardness of the material of the elbow 1, with the unit of HV; through the average thinning amount and the weight reduction removal amount within the area of any point to be processed Q , the residence time of the double high-pressure water jet in the current area to be processed can be calculated. Specifically, assuming that the average thinning amount at a certain point is 1 mm and the cross-sectional area of the jet of the double high-pressure water jet is 507 mm², then the total volume of the material to be removed at this point is 507 mm³. Assuming it is 90°, Q the calculated value of is 507 mm³ / s, then the residence time of the jet of the double high-pressure water jet at this point is 1 s, and the material with a volume of 507 mm³ can be removed; based on the above method, combined with robot offline programming and simulation processing simulation, in Q in the value calculation formula, when other parameters except the impact angle are set, the weight reduction processing parameters are determined, specifically including path planning, the impact angle at any point on the path, and the jet residence time at any point on the path.

[0044] Based on different materials, in this embodiment, the pressure of the high-pressure water is usually set in the range of 1 - 50 MPa, the pressure of the high-pressure gas is usually set in the range of 0.6 - 1.2 MPa, and the solid-liquid ratio of the abrasive particles to the high-pressure water is usually set in the range of 1:0.5 to 1:10; particularly, assuming that the solid-liquid ratio of the abrasive particles to the high-pressure water is 1:4, then the value of is 0.8, the value of is 0.2.

Claims

1. A method for reducing the weight of the surface of a special-shaped curved surface based on binocular structured light 3D measurement, which is used for reducing the weight of the outer surface of a bent pipe (1). The bent pipe (1) is composed of two half pipes, and is characterized in that, Including the following steps: Step S1: Clamp and fix the half pipe based on the inner surface of the half pipe. The fixture is provided with an outwardly convex hemispherical scanning and recognition block. The equidistant surface of the inner surface of the half pipe is used as the trajectory surface, and a binocular structured light 3D measurement camera is driven by a six-degree-of-freedom robotic arm to move along the trajectory surface to scan and obtain the global point cloud data of the outer surface of the half pipe and the scanning and recognition block; Step S2: Establish a standard three-dimensional model of the half pipe and its fixture, obtain the target point cloud data of the outer surface of the half pipe and the scanning and recognition block, perform point cloud registration on the global point cloud data of the scanning and recognition block and the target point cloud data through the ICP algorithm, and calculate the difference between the global point cloud data of the outer surface of the half pipe and the target point cloud data based on the point cloud registration result, that is, the thinning amount of the weight reduction processing of the half pipe; Step S3: Perform a double high-pressure water jet cutting operation on the two sides of the current half pipe used to contact another half pipe, and drive by a six-degree-of-freedom robotic arm to obtain a welding groove. The double high-pressure water jet is a water-gas-solid mixed water jet driven by high-pressure water and high-pressure gas, and abrasive particles are doped in the high-pressure water. The jet cross-section of the double high-pressure water jet is circular; Step S4: Perform the operations of Step S1 to Step S3 on the two half pipes respectively, and then weld the two half pipes into a bent pipe (1); Step S5: Set i = 1, 2; Clamp and fix the bent pipe (1) based on the inner curved surface of the i th half pipe. After robot offline programming and simulation machining simulation based on the thinning amount of the i th half pipe, drive the double high-pressure water jets along the trajectory surface of the i th half pipe by a six-degree-of-freedom robotic arm, and gradually complete the weight reduction of the outer curved surface of the i th half pipe; The first half pipe is the outer half pipe (101), and the trajectory surface of the outer half pipe (101) is the outer virtual surface (201); The second half pipe is the inner half pipe (102), and the trajectory surface of the inner half pipe (102) is the inner virtual surface (202); Analyze and process the global point cloud data of the outer curved surface of the outer half pipe (101) obtained through the outer virtual surface (201), and discretize it into m machining points to be processed; Analyze and process the global point cloud data of the outer curved surface of the inner half pipe (102) obtained through the inner virtual surface (202), and discretize it into n machining points to be processed; The areas of all machining points to be processed are the same, and the area value of the machining points to be processed is less than the jet cross-sectional area of the double high-pressure water jets. Calculate the average thinning amount within each area of the points to be processed; assume that the weight reduction removal amount of the double high-pressure water jet per unit time is Q , with the unit of mm³ / s, then there is: ； In the formula, K is the comprehensive coefficient, calibrated through trial processing experiments according to the material of the elbow pipe (1); is the volume fraction of high-pressure water, that is, the proportion of the volume of high-pressure water in the water jet per unit volume; is the volume fraction of abrasive particles, that is, the proportion of the volume of abrasive particles in the water jet per unit volume; is the density of high-pressure water, with the unit of kg / m³; is the density of abrasive particles, with the unit of kg / m³; d is the jet cross-sectional diameter of the double high-pressure water jet, with the unit of m; is the pressure of high-pressure water, with the unit of MPa; is the pressure of high-pressure gas, with the unit of MPa; is the impact angle, which is the angle between the jet of the double high-pressure water jet and the surface normal vector of the jet action point, with the unit of rad; n is the impact angle sensitivity coefficient, calibrated through trial processing experiments according to the material of the elbow pipe (1); H is the hardness of the material of the elbow pipe (1), with the unit of HV; through the average thinning amount and weight reduction removal amount within any area of the point to be processed Q , the residence time of the double high-pressure water jet in the current area of the point to be processed can be calculated. Combining robot offline programming and simulation machining simulation, the machining parameters can be determined; Step S6: Detect the outer surface of the processed bent pipe (1), and perform local trimming on abnormal parts until the outer surface topography of the bent pipe (1) completely meets the target requirements.

2. The method for machining surface weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 1, characterized in that: The binocular structured light 3D measurement camera uses stripe-coded structured light or speckle structured light.

3. The method for machining surface weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 2, characterized in that: m + n The value ranges between 12,000 and 30,000.

4. The method for machining the surface weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 3, wherein: d The value ranges from 25 mm to 27 mm.

5. The method for machining surface weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 4, wherein: The pressure of the high-pressure water is 1-50 MPa.

6. The method for machining the surface weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 5, characterized in that: The pressure of the high-pressure gas is 0.6-1.2 MPa.

7. The method for machining the surface weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 6, characterized in that: The solid-liquid ratio range of the abrasive particles to the high-pressure water is 1:0.5 to 1:10.

Images