Inspection methods and systems for the blade machining process of five-axis CNC machine tools

Abstract

This application relates to the field of machine tool control, and more particularly to a method and system for detecting the blade machining process of a five-axis CNC machine tool. The detection method includes: performing a three-dimensional scan of the finished blade to obtain a sample model; obtaining a simulated toolpath based on the sample model; and obtaining the five-axis deviation based on the deviation between the standard toolpath and the simulated toolpath. The detection result of the five-axis CNC machine tool is then obtained based on the five-axis deviation. The detection system includes: a 3D scanner, a programming module, a calculation module, a detection result output module, and a data storage module. This method is more reliable than relying on experience to judge the blade machining process and is also more efficient than other measurement methods. Furthermore, it establishes a correspondence between the deviation axis and the cause of the deviation, saving technicians time in analyzing the causes of problems and providing guidance for debugging and correcting the blade machining process, effectively improving the accuracy of blade machining.

Description

Technical Field

[0001] This application relates to the field of machine tool control, and in particular to a detection method and system for detecting the blade machining process of a five-axis CNC machine tool. Background Technology

[0002] The profile of a steam turbine blade can be viewed as a smooth and complex spatial twisted surface formed by fitting different sets of unequal or equidistant parallel cross-sectional profiles, exhibiting good wave characteristics and strength. Due to the complex shape of steam turbine blades, machining them is very difficult. In industrial production, five-axis CNC machine tools are often used to perform helical milling to ensure the accuracy of the finished product.

[0003] However, in the current turbine blade production process, the following problem arises: due to the special shape of turbine blades, it is difficult to measure them using conventional measurement methods, which in turn makes it impossible to detect and analyze the blade processing process. Summary of the Invention

[0004] The technical problem this application aims to solve is the difficulty in detecting the blade machining process of existing five-axis CNC machine tools.

[0005] This application provides a detection method and system for detecting the blade machining process of a five-axis CNC machine tool. The five-axis CNC machine tool uses a machining tool to machine the blade. The machining tool moves on five machining axes, including: X-axis, Y-axis, Z-axis, A-axis, and B-axis. The X-axis and Y-axis are the horizontal movement axes of the machining tool of the five-axis CNC machine tool. The Z-axis is the vertical axis through which the fixture of the five-axis CNC machine tool reciprocates. The A-axis is the rotation axis of the fixture of the five-axis CNC machine tool, and the A-axis is perpendicular to the Z-axis and parallel to the X-axis. The B-axis is the swing axis of the cutting head of the machining tool. The movement of the fixture on the Z-axis and A-axis can be equivalent to the movement of the machining tool on the Z-axis and A-axis.

[0006] The blade manufacturing process includes:

[0007] Obtain the standard model of the blade;

[0008] The standard machining parameters and standard tool information are matched to the standard model to obtain the standard toolpath, which is a set of standard tool coordinates;

[0009] The five-axis CNC machine tool controls the machining tool to move according to the standard tool path, and processes the blade to be processed into a finished blade.

[0010] Firstly, the detection method provided in this application includes the following steps:

[0011] A sample model was obtained by performing a three-dimensional scan on the finished blade;

[0012] The standard machining parameters and the standard tool information are matched to the sample model to obtain a simulated tool path, which is a set of simulated tool coordinates.

[0013] The deviation of the simulated tool coordinates in the simulated tool path is calculated based on the set of standard tool coordinates to obtain the five-axis deviation.

[0014] The detection results of the five-axis CNC machine tool are obtained based on the five-axis deviation, and the detection results include the deviation axis and the cause of the deviation;

[0015] The deviation axis is a combination of any number of axes among the five machining axes, and the deviation cause is a combination of the deviation causes corresponding to the deviation axis.

[0016] When the deviation axis is the X-axis, the causes of the deviation include X-axis origin offset. When X-axis origin offset occurs, the blade root and tail of the finished blade will have dimensional deviations, caused by tool wear or machine tool vibration.

[0017] When the deviation axis is the Y-axis, the reasons for the deviation include Y-axis zero point offset and Y-axis origin offset. When Y-axis zero point offset and Y-axis origin offset occur, the profile of the finished blade will be offset at the beginning or end of the machining process, and the air inlet and outlet edges will be too thick or too thin. This is caused by problems with the configuration of machining parameters such as tool, feed rate, depth of cut and spindle speed, or by problems with the installation of device structure such as guide rail, slider and lead screw.

[0018] When the deviation axis is the Z-axis, the causes of the deviation include Z-axis zero point offset, Z-axis origin offset, and Z-axis sub-axis positive generatrix deviation. When Z-axis zero point offset, Z-axis origin offset, and Z-axis sub-axis positive generatrix deviation occur, the included angle of the blade assembly surface will deviate or the blade profile will gradually become thinner from one end to the other. This is caused by the two sub-axis of the Z-axis of the five-axis CNC machine tool not being on the same plane.

[0019] When the deviation is on the A-axis, the cause of the deviation includes deviation of the A-axis side generatrix. When deviation of the A-axis side generatrix occurs, the surface quality of the blade becomes locally abnormal, which is caused by the inconsistency of the two sub-axis of the A-axis of the five-axis CNC machine tool.

[0020] When the deviation is B-axis, the causes of the deviation include B-axis zero-point offset. When B-axis zero-point offset occurs, tool marks appear on the smooth surface of the blade, caused by the deviation between the B-axis zero point and the Z-axis axis of the five-axis CNC machine tool.

[0021] When the deviation axis is a combination of multiple axes, the causes of deviation corresponding to each axis should be analyzed together to obtain the final cause of deviation.

[0022] Specifically, the step of performing a three-dimensional scan of the finished blade to obtain a sample model includes:

[0023] The finished blades are uniformly sprayed with positioning powder;

[0024] The point cloud data of the positioning powder is acquired using a 3D scanner. The 3D scanner is based on the principle of quasi-triangulation and scans the positioning powder from multiple angles, placing the point cloud data in the same quasi-triangulated model.

[0025] The sample model is obtained based on the point cloud data.

[0026] Specifically, the standard machining parameters include: fixture model, blank size, machining origin, roughing program, and finishing program; the standard tool information includes: tool model, tool length, and tool tip diameter.

[0027] Specifically, the deviation calculation for each simulated tool coordinate in the simulated toolpath includes:

[0028] For each simulated tool coordinate in the simulated toolpath N j ( x 2, y 2, z 2, a 2, b 2) Calculate the standard toolpath. i = j Standard tool coordinates N i ( x 1, y 1, z 1, a 1, b 1) with the simulated tool coordinates N j ( x 2, y 2, z 2, a 2, b 2) The difference between the five components is used to obtain the five-axis deviation.

[0029] in, i The index representing the toolpath coordinates. i ∈{1,2,3,...}, x 1. y 1. z 1.a 1 and b 1 represents the five components of the standard tool coordinate on the machining axis. j The index representing the coordinates of the simulated tool. j ∈{1,2,3,...}, x 2. y 2. z 2. a 2 and b 2 represents the five components of the simulated tool coordinates on the machining axis. The number of simulated tool coordinates and the number of standard tool coordinates are equal. The five-axis deviation includes... X 偏 , Y 偏 , Z 偏 , A 偏 , B 偏 ,

[0030] .

[0031] Specifically, the step of obtaining the detection result of the five-axis CNC machine tool based on the five-axis deviation includes:

[0032] For all X 偏 , Y 偏 , Z 偏 , A 偏 , B 偏 The absolute sum of the values ​​is calculated separately, and the sum of the absolute values ​​is compared with the set judgment threshold to obtain the deviation axis.

[0033] Secondly, the detection system provided in this application includes the following modules:

[0034] 3D scanner, programming module, calculation module, detection result output module, and data storage module;

[0035] The 3D scanner is used to perform 3D scanning on the finished blades to obtain a sample model, and the sample model is stored in the data storage module;

[0036] The programming module is used to obtain the standard machining parameters and standard machining parameters of the standard model from the data storage module, and match the standard machining parameters and the standard tool information to the sample model to obtain the simulated tool path;

[0037] The calculation module is used to obtain the simulated toolpath and calculate the deviation between the simulated toolpath and the standard toolpath in the data storage module to obtain the five-axis deviation.

[0038] The detection result output module is used to output the detection result of the five-axis CNC machine tool based on the five-axis deviation.

[0039] Specifically, the 3D scanner includes a scanning lens, positioning powder, and a sample fixing platform. The finished blade is fixed on the sample fixing platform, and the positioning powder is uniformly covered on the finished blade. The scanning lens faces the sample fixing platform and can rotate around the sample fixing platform.

[0040] Specifically, the 3D scanner also includes a vision receiving module, which is connected to the scanning lens to receive point cloud data of the positioning powder acquired by the scanning lens, and to build the sample model based on the point cloud data.

[0041] Specifically, the programming module obtains the fixture model, blank size, machining origin, roughing program, finishing program, tool model, tool length, and tool tip diameter of the sample model from the data storage module.

[0042] Specifically, the monitoring system also includes a machine tool control module, which acquires the detection results output by the detection result output module and issues control commands to the five-axis CNC machine tool based on the detection results.

[0043] This application has the following technical effects:

[0044] Overcoming the limitations of existing technologies that rely on the experience of technicians to determine the causes of deviations in the blade manufacturing process due to the difficulty in measuring finished blades, this paper proposes a more accurate, easier-to-implement, and more efficient method to detect the blade manufacturing process and locate the causes of problems. Attached Figure Description

[0045] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. Several embodiments of this application are illustrated in the drawings by way of example and not limitation, and the same or corresponding reference numerals denote the same or corresponding parts.

[0046] Figure 1 This is a flowchart of the detection method for the blade processing process in an embodiment of this application;

[0047] Figure 2 This is a diagram showing the finished blades in an embodiment of this application;

[0048] Figure 3 This is a schematic diagram of the simulated toolpath in the embodiments of this application;

[0049] Figure 4 This is a schematic diagram of the detection system for the blade processing process in an embodiment of this application. Detailed Implementation

[0050] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] It should be understood that when the terms "first," "second," etc., are used in the claims, description, and drawings of this application, they are only used to distinguish different objects and not to describe a specific order. The terms "comprising" and "including" used in the description and claims of this application indicate the presence of the described features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0052] In the process of producing steam turbine blades, the inventors of this application have found that due to the special and complex shape of the blades, it is difficult to detect the processing accuracy of the finished blades through some conventional measurement methods. Even if an abnormality in the processing accuracy of the finished blades is detected, the technicians have no way of knowing what caused the abnormality in the processing accuracy during the blade processing. Often, a large number of experiments and analyses are required to debug and correct the blade processing process.

[0053] To address this problem, inventors in this field have conducted research on how to inspect the blade machining process and how to identify the causes of problems, and have proposed a method and system for inspecting the blade machining process of a five-axis CNC machine tool:

[0054] Firstly, in this embodiment, as Figure 1 As shown, the detection method for the blade processing includes the following steps:

[0055] S1: A 3D scan of the finished blade is performed to obtain a sample model. In this embodiment, the processed blade is... Figure 2 The shape shown is as follows. Positioning powder is evenly sprayed onto the blade to completely cover it. Then, the blade is placed in a 3D scanner, which scans and acquires the point cloud data of the positioning powder. After repeated scanning with adjustments to the angle, the complete point cloud data of the blade is obtained. A sample model in PRT format is generated based on this point cloud data.

[0056] S2: Match standard machining parameters and standard tool information to the sample model to obtain a simulated toolpath. Open Geomagic Design X software to reverse engineer the sample model, and program it using RCS software. Define the fixture model, blank size, machining origin, roughing program, finishing program, tool model, tool length, and tool tip diameter. These parameter values ​​should match the parameters defined in the machining process of the finished blade. Then, the software can generate a simulated toolpath based on the cross-section of the sample model. For example... Figure 3 As shown, the simulated toolpath contains simulated tool coordinates. This embodiment uses incremental programming, meaning that each simulated tool coordinate is generated based on the previous simulated tool coordinate.

[0057] S3: Calculate the deviation of the simulated tool coordinates in the simulated toolpath based on the set of standard tool coordinates to obtain the five-axis deviation. Table 1 shows some of the simulated tool coordinates and standard tool coordinates in this embodiment:

[0058] Table 1 Simulated tool coordinates and standard toolpath coordinates

[0059]

[0060] For each simulated tool coordinate in the simulated toolpath N j ( x 2, y 2, z 2, a 2, b 2) Calculate the standard toolpath i = j Standard tool coordinates N i ( x 1, y 1, z 1, a 1, b 1) With simulated tool coordinates N j ( x 2, y 2, z 2, a 2, b 2) The difference between the five components is used to obtain the five-axis deviation.

[0061] in, i Indicates the sequence number of the toolpath coordinates. i ∈{1,2,3,...}, x 1. y 1.z 1. a 1 and b 1 represents the five components of the standard tool coordinate system on the machining axis. j Indicates the sequence number of the simulated tool coordinates. j ∈{1,2,3,...}, x 2. y 2. z 2. a 2 and b 2 represents the five components of the simulated tool coordinates on the machining axis. The number of simulated tool coordinates is equal to that of the standard tool coordinates. The five-axis deviation includes... X 偏 , Y 偏 , Z 偏 , A 偏 , B 偏 ,

[0062] .

[0063] The results are shown in Table 2:

[0064] Table 2 Five-axis deviation table

[0065]

[0066] S4: Obtain the inspection results of the five-axis CNC machine tool based on the five-axis deviation. The inspection results include the deviation axis and the cause of the deviation.

[0067] The deviation axis is a combination of any number of axes from the five machining axes, and the deviation cause is a combination of the deviation causes corresponding to the deviation axis.

[0068] When the deviation axis is the X-axis, the causes of deviation include X-axis origin offset. When X-axis origin offset occurs, the blade root and tail of the finished blade will have dimensional deviations, caused by tool wear or machine tool vibration.

[0069] When the deviation axis is the Y-axis, the causes of deviation include Y-axis zero point offset and Y-axis origin offset. When Y-axis zero point offset and Y-axis origin offset occur, the profile of the finished blade will be offset at the beginning or end of the machining process, and the air inlet and outlet edges will be too thick or too thin. This is caused by problems with the configuration of machining parameters such as tool, feed rate, depth of cut and spindle speed, or by problems with the installation of device structure such as guide rail, slider and lead screw.

[0070] When the deviation axis is the Z-axis, the causes of deviation include Z-axis zero point offset, Z-axis origin offset, and Z-axis sub-axis positive generatrix deviation. When Z-axis zero point offset, Z-axis origin offset, and Z-axis sub-axis positive generatrix deviation occur, the included angle of the blade assembly surface will deviate or the blade profile will gradually become thinner from one end to the other. This is caused by the two sub-axis of the Z-axis of the five-axis CNC machine tool not being on the same plane.

[0071] When the deviation is on the A-axis, the causes of the deviation include deviation of the A-axis side generatrix. When deviation of the A-axis side generatrix occurs, the surface quality of the blades becomes locally abnormal, which is caused by the inconsistency of the two sub-axis of the A-axis of the five-axis CNC machine tool.

[0072] When the deviation is on the B-axis, the causes of the deviation include B-axis zero-point offset. When B-axis zero-point offset occurs, tool marks appear on the smooth surface of the blade, which is caused by the deviation between the B-axis zero point and the Z-axis axis of the five-axis CNC machine tool.

[0073] Based on the five-axis deviation data shown in Table 2, the deviation axes are identified as the X and Z axes. Combining the causes of the X and Z axis deviations, technicians can further conclude that the center point of the machining tool has changed, indicating an RTCP accuracy problem. This allows for rapid decision-making to correct the center point of the machining tool. To correct the center point of the machining tool, a straightening block with a pressure gauge is placed in the fixture of the five-axis CNC machine tool. The swing angle of the machining tool is set to 30° and -30°. The two pressure gauge readings are measured. The pressure gauge readings are then added to the Z-axis coordinate value, and the offset value is calculated using the following formula:

[0074]

[0075]

[0076] Where f is the Z-axis offset value, g is the X-axis offset value, and the other parameters are shown in Table 3:

[0077] Table 3 Calculation Parameter Table

[0078]

[0079] Therefore, we obtain the Z-axis offset value, which is the distance from the spindle end face to the center of rotation, f = 100.1269, and the X-axis offset value, which is the distance from the spindle axis to the center of rotation, g = -0.0180.

[0080] Secondly, such as Figure 4 As shown, the detection system provided in this embodiment includes the following modules:

[0081] 3D scanner, programming module, calculation module, detection result output module, and data storage module;

[0082] A 3D scanner is used to perform 3D scanning on finished blades to obtain sample models, which are stored in a data storage module.

[0083] The programming module is used to obtain the standard machining parameters and standard tool information of the standard model from the data storage module, and match the standard machining parameters and standard tool information to the sample model to obtain the simulated tool path;

[0084] The calculation module is used to obtain the simulated toolpath and calculate the deviation between the simulated toolpath and the standard toolpath in the data storage module to obtain the five-axis deviation.

[0085] The test result output module is used to output the test results of the five-axis CNC machine tool based on the five-axis deviation.

[0086] Specifically, the 3D scanner includes a scanning lens, positioning powder, and a sample fixing platform. The finished blade is fixed on the sample fixing platform, and the finished blade is uniformly covered with positioning powder. The scanning lens is facing the sample fixing platform and can rotate around the sample fixing platform.

[0087] Specifically, the 3D scanner also includes a vision receiving module, which is connected to the scanning lens to receive point cloud data of the positioning powder acquired by the scanning lens, and to build a sample model based on the point cloud data.

[0088] Specifically, the programming module retrieves the fixture model, blank size, machining origin, roughing program, finishing program, tool model, tool length, and tool tip diameter of the sample model from the data storage module.

[0089] Specifically, the monitoring system also includes a machine tool control module, which acquires the detection results output by the detection result output module and issues control commands to the five-axis CNC machine tool based on the detection results.

[0090] While this specification has shown and described numerous embodiments of the present application, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will arise for those skilled in the art without departing from the spirit and intent of the present application. It should be understood that various alternatives to the embodiments of the present application described herein may be employed in the practice of this application.

[0091] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for detecting the blade machining process of a five-axis CNC machine tool, wherein the five-axis CNC machine tool uses a machining tool to machine the blade, the machining tool moves on five machining axes, the five machining axes comprising: X-axis, Y-axis, Z-axis, A-axis, and B-axis; The blade processing procedure includes: Obtain the standard model of the blade; The standard machining parameters and standard tool information are matched to the standard model to obtain the standard toolpath, which is a set of standard tool coordinates; The five-axis CNC machine tool controls the machining tool to move according to the standard tool path, and processes the blade to be processed into a finished blade; The detection method is characterized by comprising: A sample model was obtained by performing a three-dimensional scan on the finished blade; The standard machining parameters and the standard tool information are matched to the sample model to obtain a simulated tool path, which is a set of simulated tool coordinates. The deviation of the simulated tool coordinates in the simulated tool path is calculated based on the set of standard tool coordinates to obtain the five-axis deviation. The detection results of the five-axis CNC machine tool are obtained based on the five-axis deviation, and the detection results include the deviation axis and the cause of the deviation; The deviation axis is a combination of any number of axes among the five machining axes, and the deviation cause is a combination of the deviation causes corresponding to the deviation axis. When the deviation axis is the X-axis, the causes of the deviation include X-axis origin offset; When the deviation axis is the Y-axis, the causes of the deviation include Y-axis zero-point offset and Y-axis origin offset; When the deviation axis is the Z-axis, the causes of the deviation include Z-axis zero-point offset, Z-axis origin offset, and Z-axis sub-axis positive generatrix deviation; When the deviation is along the A-axis, the causes of the deviation include deviation of the A-axis side generatrix; When the deviation is on the B-axis, the cause of the deviation includes B-axis zero-point offset.

2. The detection method according to claim 1, characterized in that, The step of performing a three-dimensional scan of the finished blade to obtain a sample model includes: The finished blades are uniformly sprayed with positioning powder; Point cloud data of the positioning powder was acquired using a 3D scanner; The sample model is obtained based on the point cloud data.

3. The detection method according to claim 1, characterized in that, The standard machining parameters include: fixture model, blank size, machining origin, roughing program and finishing program, and the standard tool information includes: tool model, tool length and tool tip diameter.

4. The detection method according to claim 1, characterized in that, The step of calculating the deviation of the simulated tool coordinates in the simulated toolpath based on the set of standard tool coordinates yields the five-axis deviation, which includes: For each simulated tool coordinate in the simulated toolpath N j ( x 2, y 2, z 2, a 2, b 2) Calculate the standard toolpath. i = j Standard tool coordinates N i ( x 1, y 1, z 1, a 1, b 1) with the simulated tool coordinates N j ( x 2, y 2, z 2, a 2, b 2) The difference between the five components is used to obtain the five-axis deviation. in, i The index represents the coordinate of the standard toolpath. i ∈{1,2,3,...}, x 1. y 1. z 1. a 1 and b 1 represents the five components of the standard tool coordinate on the machining axis. j The index representing the coordinates of the simulated tool. j ∈{1,2,3,...}, x 2. y 2. z 2. a 2 and b 2 represents the five components of the simulated tool coordinates on the machining axis. The number of simulated tool coordinates and the number of standard tool coordinates are equal. The five-axis deviation includes... X 偏 , Y 偏 , Z 偏 , A 偏 , B 偏 , 。 5. The detection method according to claim 4, characterized in that, The step of obtaining the inspection result of the five-axis CNC machine tool based on the five-axis deviation includes: For all X 偏 , Y 偏 , Z 偏 , A 偏 , B 偏 The absolute sum of the values ​​is calculated separately, and the sum of the absolute values ​​is compared with the set judgment threshold to obtain the deviation axis.

6. A detection system for the blade machining process of a five-axis CNC machine tool, operating using the method described in any one of claims 1-5, characterized in that, Includes: a 3D scanner, a programming module, a calculation module, a detection result output module, and a data storage module; The 3D scanner is used to perform 3D scanning on the finished blades to obtain a sample model, and the sample model is stored in the data storage module; The programming module is used to obtain the standard machining parameters and standard machining parameters of the standard model from the data storage module, and match the standard machining parameters and the standard tool information to the sample model to obtain the simulated tool path; The calculation module is used to obtain the simulated toolpath and calculate the deviation between the simulated toolpath and the standard toolpath in the data storage module to obtain the five-axis deviation. The detection result output module is used to output the detection result of the five-axis CNC machine tool based on the five-axis deviation.

7. The detection system according to claim 6, characterized in that, The 3D scanner includes a scanning lens, positioning powder, and a sample fixing platform. The finished blade is fixed on the sample fixing platform, and the positioning powder is evenly covered on the finished blade. The scanning lens faces the sample fixing platform and can rotate around the sample fixing platform.

8. The detection system according to claim 7, characterized in that, The 3D scanner also includes a vision receiving module, which is connected to the scanning lens to receive point cloud data of the positioning powder acquired by the scanning lens, and to build the sample model based on the point cloud data.

9. The detection system according to claim 6, characterized in that, The programming module obtains the fixture model, blank size, machining origin, roughing program, finishing program, tool model, tool length, and tool tip diameter of the sample model from the data storage module.

10. The detection system according to claim 6, characterized in that, The detection system also includes a machine tool control module, which acquires the detection results output by the detection result output module and issues control commands to the five-axis CNC machine tool based on the detection results.

Images