A method for compensating position deviation in small hole machining

Abstract

The present invention discloses a method for compensating position deviation of small hole processing, which is as follows: Step 1: Select a machine tool: The machine tool used is a five-axis electric spark small hole machine, and the machine tool coordinates are defined as follows: X, Y, and Z are linear axes, and B and C are rotation axes, wherein the X, Y, and Z axes conform to spatial Cartesian coordinates, the B axis revolves around the Y axis, and the C axis is mounted on the B axis. When the B axis is at zero position, the rotation axis of the C axis is parallel to the Z axis, and the workbench is mounted on the C axis; the beneficial effects of the present invention are: for workpieces with large surface errors, when processing small holes, the small holes on the workpiece can be first divided into different areas according to different positions, and a regional local coordinate system is established in each area; during actual processing, it is only necessary to find the actual position coordinates and leaf shape trend vector of the coordinate origin of each area in the machine tool coordinate system to compensate for the small hole position in a specific area, thereby adapting to changes in the workpiece surface error.

Description

Technical Field

[0001] The invention belongs to the technical field of film hole machining on engine turbine guide blades, and particularly relates to a method for compensating position deviation of small hole machining. Background Art

[0002] There are many small holes for cooling distributed on the turbine guide blades of aircraft engines. The small holes on these workpieces are mostly processed by electrospark small hole machining. Since the surfaces of the workpieces that need to be processed by electrospark small hole machining are mostly casting surfaces, there are large casting errors. Before electrospark machining small holes, a positioning reference is generally machined on the casting by mechanical processing, and then the workpiece is positioned and mounted on the machine tool using the positioning reference. Through alignment and tool setting, the workpiece coordinates of the machine tool are made to coincide with the programmed theoretical coordinates, and then the program is run for machining. This method requires that the relative actual position and theoretical position of the surface of the workpiece to be machined hole and the positioning reference have no deviation or a small deviation, otherwise the actual position of the machined small hole on the casting surface will deviate greatly from the theoretical position. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for compensating the position deviation of small hole processing, which can obtain the deviation value between the actual position and theoretical position of the feature point by detecting the actual position of the selected feature point, and then use the deviation value to compensate and correct the small hole processing position using a compensation algorithm.

[0004] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a method for compensating position deviation in small hole machining, the method being as follows:

[0005] Step 1: Select the machine tool: The machine tool used is a five-axis EDM machine. The machine tool coordinates are defined as follows: X, Y, and Z are linear axes, and B and C are rotation axes. Among them, the X, Y, and Z axes conform to the spatial Cartesian coordinates. The B axis revolves around the Y axis, and the C axis is mounted on the B axis. When the B axis is at zero position, the rotation axis of the C axis is parallel to the Z axis, and the worktable is mounted on the C axis.

[0006] Step 2: Measure the projection coordinates of the machine tool B-axis rotation center on the XZ plane;

[0007] Step 3: Clamp the workpiece: Install the workpiece on the machine table, rotate the C-axis to align the workpiece rotation center with the C-axis rotation center, and then clamp the workpiece;

[0008] Step 4: Set the machine tool working coordinate zero position;

[0009] Step 5: Establish a local coordinate system for the part's digital model, divide the locations of the air film holes into different areas according to their distribution, and establish a local coordinate system in each area on the mathematical model of the part by determining the origin, Z-axis direction, and X-axis direction. A point on the above contour line is selected as the coordinate origin, the Z-axis direction is vertically upward, and the X-direction is the direction of the above projection vector.

[0010] Step 6: Collect theoretical data of the film hole and draw a machining vector for the film hole on the part model. The vector point is the intersection of the film hole axis and the part surface, and the vector direction is the axis direction of the film hole, pointing from the part surface to the inside of the part. The theoretical data of the film hole machining vector is collected, and the data includes the point coordinates and direction coordinates of the machining vector in the above local coordinate system.

[0011] Step 7: Find the actual position of the origin of the local coordinate point on the part surface in the machine tool workpiece coordinate system: calibrate the position of the origin of the digital model local coordinate system on the actual machine tool part by probing, marking, visual inspection or conversion methods, and obtain the coordinate value of the local coordinate origin of the digital model in the workpiece coordinate system;

[0012] Step 8: The actual processing point coordinates of the air film hole on the machine tool can be obtained by calculation based on the projection coordinates of the B-axis rotation center of the machine tool on the XZ plane, the point coordinates and direction coordinates of the air film hole processing vector in the local coordinate system, and the coordinate value data of the local coordinate origin of the digital model in the workpiece coordinate system;

[0013] Step 9: Move the machine tool so that the electrode tube to be processed is at the actual processing point position and carry out processing.

[0014] As a preferred technical solution of the present invention, in step 2, the specific operations are as follows:

[0015] When the B axis is rotated and the worktable plane is in a horizontal position, the B axis is reset;

[0016] Move the X-axis and Y-axis so that the rotation center of the machine tool electrode tube coincides with the rotation center of the C-axis, and reset the X-axis and Y-axis;

[0017] Face the Y+ direction, rotate the B axis 90° counterclockwise from the initial position to put the worktable in the left vertical position, move the X axis so that the side wall of the electrode tube touches the worktable surface, and record the X axis coordinate value X1 of the machine tool; return to the initial position, rotate the B axis 90° clockwise so that the worktable is in the right vertical position, move the X axis so that the side wall of the electrode tube touches the worktable surface, and record the X axis coordinate value X2 of the machine tool;

[0018] Measure the diameter d of the electrode tube;

[0019] By calculation, the projection coordinates of the B-axis rotation center on the XZ plane can be obtained.

[0020] As a preferred technical solution of the present invention, in step 4, the specific operations are as follows:

[0021] B-axis zero position -B By rotating the B-axis, the machine tool work table is aligned with the horizontal plane and the B-axis coordinate is reset to zero;

[0022] X-axis and Y-axis zero position - when the B-axis is at zero position and the rotation center of the machine tool electrode tube coincides with the rotation center of the C-axis, the X-axis and Y-axis coordinates are cleared;

[0023] Z-axis zero position - when the B-axis is at zero position, the Z-axis coordinate is cleared when the tip of the machine tool processing electrode tube touches the work table;

[0024] C-axis zero position - Draw the maximum contour line of the blade surface along the negative Z-axis on the mathematical model of the workpiece; select two characteristic points along the contour line and connect them to draw the blade shape trend vector; through detection, marking, visual inspection, and conversion methods, the machine tool electrode is positioned at the actual position of the above two characteristic points, and the machine tool working coordinates of the first characteristic point and the second characteristic point are recorded;

[0025] By calculation, the angle δc between the actual blade trend vector direction and the X-axis of the machine tool working coordinate system is obtained; when the C-axis is rotated by δc so that the direction of the projection vector of the above blade trend vector on the horizontal plane coincides with the positive direction of the X-axis, the C-axis is reset.

[0026] As a preferred technical solution of the present invention, it also includes a monitoring camera, which is used to film the processing process.

[0027] As a preferred technical solution of the present invention, it also includes a processing unit connected to the monitoring camera for processing the camera data.

[0028] As a preferred technical solution of the present invention, the processing of the camera data includes smoothing filtering, threshold segmentation, and local extraction.

[0029] As a preferred technical solution of the present invention, it also includes a visualization terminal, through which the processing data can be viewed.

[0030] As a preferred technical solution of the present invention, the visualization terminal includes a mobile phone and a computer.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] For workpieces with large surface errors, when machining small holes, the small holes on the workpiece can be divided into different areas according to their different positions, and a local coordinate system can be established in each area. During actual machining, it is only necessary to find the actual position coordinates and lobe trend vector of each area's coordinate origin in the machine tool coordinate system to compensate for the small hole position in the specific area, thereby adapting to changes in the workpiece surface error.

[0033] The processing process is recorded by monitoring cameras; the efficiency of data processing is improved through smoothing filtering, threshold segmentation, and local extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the machine tool structure used in the present invention;

[0035] Figure 2 The projection coordinates of the B-axis rotation center of the measuring machine tool in the XZ plane ( , ) Figure 1 ;

[0036] Figure 3 The projection coordinates of the B-axis rotation center of the measuring machine tool in the XZ plane ( , ) Figure 2 ;

[0037] Figure 4 Schematic diagram of blade trend vector of the present invention;

[0038] Figure 5 Schematic diagram of the local coordinate relationship of the workpiece coordinate area of ​​the machine tool of the present invention;

[0039] Figure 6 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example

[0041] See also Figures 1-6 , which is the first embodiment of the present invention, provides a method for compensating position deviation in small hole machining, the method is as follows:

[0042] Step 1: Select the machine tool: The machine tool used is a five-axis EDM machine. The machine tool coordinates are defined as follows: X, Y, and Z are linear axes, and B and C are rotation axes. Among them, the X, Y, and Z axes conform to the spatial Cartesian coordinates. The B axis revolves around the Y axis, and the C axis is mounted on the B axis. When the B axis is at zero position, the rotation axis of the C axis is parallel to the Z axis, and the worktable is mounted on the C axis.

[0043] Step 2: Measure the projection coordinates of the machine tool B-axis rotation center on the XZ plane ( , );

[0044] The specific operations are as follows:

[0045] When the B axis is rotated and the worktable plane is in a horizontal position, the B axis is reset;

[0046] Move the X-axis and Y-axis so that the rotation center of the machine tool electrode tube coincides with the rotation center of the C-axis, and reset the X-axis and Y-axis;

[0047] Face the Y+ direction, rotate the B axis 90° counterclockwise from the initial position to put the worktable in the left vertical position, move the X axis so that the side wall of the electrode tube touches the worktable surface, and record the X axis coordinate value X1 of the machine tool; return to the initial position, rotate the B axis 90° clockwise so that the worktable is in the right vertical position, move the X axis so that the side wall of the electrode tube touches the worktable surface, and record the X axis coordinate value X2 of the machine tool;

[0048] Measure the diameter d of the electrode tube;

[0049] By calculation, the projection coordinates of the B-axis rotation center on the XZ plane can be obtained ( , ).

[0050] The calculation method is:

[0051] =( + )÷2; =( - +d)÷2

[0052] Step 3: Clamp the workpiece: Install the workpiece on the machine table, rotate the C-axis to align the workpiece rotation center with the C-axis rotation center, and then clamp the workpiece;

[0053] Step 4: Set the machine tool working coordinate zero position;

[0054] The specific operations are as follows:

[0055] B-axis zero position -B By rotating the B-axis, the machine tool work table is aligned with the horizontal plane and the B-axis coordinate is reset to zero;

[0056] X-axis and Y-axis zero position - when the B-axis is at zero position and the rotation center of the machine tool electrode tube coincides with the rotation center of the C-axis, the X-axis and Y-axis coordinates are cleared;

[0057] Z-axis zero position - when the B-axis is at zero position, the Z-axis coordinate is cleared when the tip of the machine tool processing electrode tube touches the work table;

[0058] C-axis zero position - draw the maximum contour line of the blade surface along the negative direction of the Z axis on the mathematical model of the workpiece; select two feature points along the contour line and connect them to draw the blade trend vector; through detection, marking, visual inspection, and conversion methods, the machine tool electrode is positioned at the actual position of the above two feature points respectively, and the machine tool working coordinates of the first feature point are recorded ( , ), and the machine tool working coordinates of the second feature point ( , );

[0059] By calculation, the angle δc between the actual blade profile trend vector direction and the X-axis of the machine tool working coordinate system is obtained;

[0060] The calculation method is:

[0061] δc=arctan[( - )÷( - )]

[0062] Rotate the C axis by δc so that the direction of the projection vector of the leaf shape trend vector on the horizontal plane coincides with the positive direction of the X axis, and the C axis is cleared;

[0063] Step 5: Establish a local coordinate system for the part's digital model, divide the locations of the air film holes into different areas according to their distribution, and establish a local coordinate system in each area on the mathematical model of the part by determining the origin, Z-axis direction, and X-axis direction. A point on the above contour line is selected as the coordinate origin, the Z-axis direction is vertically upward, and the X-direction is the direction of the above projection vector.

[0064] Step 6: Collect theoretical data of the film hole, and make a processing vector of the film hole on the part model. The vector point is the intersection of the film hole axis and the part surface, and the vector direction is the axis direction of the film hole, pointing from the part surface to the inside of the part; collect the theoretical data of the film hole processing vector, which includes the point coordinates of the processing vector in the above local coordinate system ( , , ) and direction coordinates ( , , );

[0065] Step 7: Find the actual position of the origin of the local coordinate point on the part surface in the machine tool workpiece coordinate system: calibrate the position of the origin of the digital model local coordinate system on the real part of the machine tool by detection, marking, visual inspection or conversion method, and obtain the coordinate value of the local coordinate origin of the digital model in the workpiece coordinate system ( δx, δy, δz );

[0066] Step 8: According to the projection coordinates of the B-axis rotation center of the machine tool on the XZ plane ( , ), the point coordinates of the air film hole processing vector in the above local coordinate system ( , , ) and direction coordinates ( , , ), the coordinate value of the local coordinate origin of the digital model in the workpiece coordinate system ( δx, δy, δz ) data can be calculated to obtain the actual processing point coordinates of the air film hole on the machine tool ( , , , , );

[0067] The details are as follows:

[0068] Step 1: The programmer obtains the data of each air film hole 、 , δx, δy, δz, 、 、 、 、 、 data;

[0069] Among them, different machine tools 、 The value of will be different. For the same machine tool, 、 The value remains consistent;

[0070] Among them, the values ​​of δx, δy, and δz in the air film hole division area of ​​different workpieces will be different, and the values ​​of δx, δy, and δz in the same air film hole division area will remain consistent;

[0071] Step 2: The programmer sets the rotation direction data m of the B axis. The setting method of the above m is: if the B axis rotates counterclockwise towards the positive direction of the Y axis, m is set to 0, and if the B axis rotates clockwise, m is set to 1;

[0072] Step 3: Calculate the actual processing point coordinates of the air film hole on the machine tool ( , , , , );

[0073] Step 9: Move the machine tool so that the electrode tube is at the actual processing point ( , , , , ) position for processing. Example

[0074] See also Figures 1-6 , which is the second embodiment of the present invention, is based on the previous embodiment, except that:

[0075] It also includes a monitoring camera, which is used to record the processing process; and a processing unit that is connected to the monitoring camera for communication, which is used to process the recorded data.

[0076] In this embodiment, preferably, the camera data is processed including smoothing filtering, threshold segmentation, and local extraction to improve the efficiency of data processing.

[0077] In this embodiment, preferably, a visualization terminal is also included, through which processing data can be viewed, thereby further increasing the convenience of use.

[0078] In this embodiment, preferably, the visualization terminal includes a mobile phone and a computer.

[0079] Although the embodiments of the present invention have been shown and described, as detailed above, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the invention, and the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for compensating position deviation in small hole machining, characterized by: The method is as follows: Step 1: Select the machine tool: The machine tool used is a five-axis EDM machine. The machine tool coordinates are defined as follows: X, Y, and Z are linear axes, and B and C are rotation axes. Among them, the X, Y, and Z axes conform to the spatial Cartesian coordinates. The B axis revolves around the Y axis, and the C axis is mounted on the B axis. When the B axis is at zero position, the rotation axis of the C axis is parallel to the Z axis, and the worktable is mounted on the C axis. Step 2: Measure the projection coordinates of the machine tool B-axis rotation center on the XZ plane; Step 3: Clamp the workpiece: Install the workpiece on the machine table, rotate the C-axis to align the workpiece rotation center with the C-axis rotation center, and then clamp the workpiece; Step 4: Set the machine tool working coordinate zero position; Step 5: Establish a local coordinate system for the part's digital model, divide the locations of the air film holes into different areas according to their distribution, and establish a local coordinate system in each area on the mathematical model of the part by determining the origin, Z-axis direction, and X-axis direction. A point on the above contour line is selected as the coordinate origin, the Z-axis direction is vertically upward, and the X-direction is the direction of the above projection vector. Step 6: Collect theoretical data of the film hole and draw a machining vector for the film hole on the part model. The vector point is the intersection of the film hole axis and the part surface, and the vector direction is the axis direction of the film hole, pointing from the part surface to the inside of the part. The theoretical data of the film hole machining vector is collected, and the data includes the point coordinates and direction coordinates of the machining vector in the above local coordinate system. Step 7: Find the actual position of the origin of the local coordinate point on the part surface in the machine tool workpiece coordinate system: calibrate the position of the origin of the digital model local coordinate system on the actual machine tool part by probing, marking, visual inspection or conversion methods, and obtain the coordinate value of the local coordinate origin of the digital model in the workpiece coordinate system; Step 8: The actual processing point coordinates of the air film hole on the machine tool can be obtained by calculation based on the projection coordinates of the B-axis rotation center of the machine tool on the XZ plane, the point coordinates and direction coordinates of the air film hole processing vector in the local coordinate system, and the coordinate value data of the local coordinate origin of the digital model in the workpiece coordinate system; Step 9: Move the machine tool so that the electrode tube to be processed is at the actual processing point position and carry out processing.

2. A method for compensating position deviation in small hole machining according to claim 1, characterized in that: In the step 2, the specific operations are as follows: When the B axis is rotated and the worktable plane is in a horizontal position, the B axis is reset; Move the X-axis and Y-axis so that the rotation center of the machine tool electrode tube coincides with the rotation center of the C-axis, and reset the X-axis and Y-axis; Face the Y+ direction, rotate the B axis 90° counterclockwise from the initial position to put the worktable in the left vertical position, move the X axis so that the side wall of the electrode tube touches the worktable surface, and record the X axis coordinate value X1 of the machine tool; return to the initial position, rotate the B axis 90° clockwise so that the worktable is in the right vertical position, move the X axis so that the side wall of the electrode tube touches the worktable surface, and record the X axis coordinate value X2 of the machine tool; Measure the diameter d of the electrode tube; By calculation, the projection coordinates of the B-axis rotation center on the XZ plane can be obtained.

3. The method for compensating position deviation in small hole machining according to claim 1, characterized in that: In step 4, the specific operations are as follows: B-axis zero position -B By rotating the B-axis, the machine tool work table is aligned with the horizontal plane and the B-axis coordinate is reset to zero; X-axis and Y-axis zero position - when the B-axis is at zero position and the rotation center of the machine tool electrode tube coincides with the rotation center of the C-axis, the X-axis and Y-axis coordinates are cleared; Z-axis zero position - when the B-axis is at zero position, the Z-axis coordinate is cleared when the tip of the machine tool processing electrode tube touches the work table; C-axis zero position - Draw the maximum contour line of the blade surface along the negative Z-axis on the mathematical model of the workpiece; select two characteristic points along the contour line and connect them to draw the blade shape trend vector; through detection, marking, visual inspection, and conversion methods, the machine tool electrode is positioned at the actual position of the above two characteristic points, and the machine tool working coordinates of the first characteristic point and the second characteristic point are recorded; By calculation, the angle δc between the actual blade profile trend vector direction and the X-axis of the machine tool working coordinate system is obtained; The C axis is rotated by δc so that the direction of the projection vector of the leaf shape trend vector on the horizontal plane coincides with the positive direction of the X axis, and the C axis is cleared.

4. A method for compensating position deviation in small hole machining according to claim 1, characterized in that: It also includes a monitoring camera, which is used to record the processing process.

5. A method for compensating position deviation in small hole machining according to claim 4, characterized in that: It also includes a processing unit that is in communication with the surveillance camera, and processes the camera data through the processing unit.

6. A method for compensating position deviation in small hole machining according to claim 5, characterized in that: The camera data is processed including smoothing filtering, threshold segmentation, and local extraction.

7. A method for compensating position deviation in small hole machining according to claim 1, characterized in that: It also includes a visualization terminal, through which processing data can be viewed.

8. A method for compensating position deviation in small hole machining according to claim 7, characterized in that: The visualization terminal includes a mobile phone and a computer.

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