Deep hole machining method of large boring and milling machine

Abstract

The invention discloses a deep hole machining method for a large boring and milling machine, relates to the field of metal material machining, and discloses the method comprising the steps that S1, rough machining is conducted on a hole system in a workpiece according to product requirements; s2, before the workpiece is transferred to finish machining equipment from rough machining equipment, coordinate and error vector evaluation is conducted on the workpiece according to the form and location tolerance type, and coordinates (Xn, Yn and Zn) are obtained; s3, the workpiece is fixed to finish machining equipment for alignment and positioning of a finish machining hole datum, a coordinate system is established according to the form and location tolerance type, coordinates (X'n, Y'n and Z'n) are obtained, and then coordinate system deviation is obtained; s4, according to the form and location tolerance type, coordinate system deviation compensation is conducted on the machining equipment, and then corresponding calibration datum holes are designed in all the holes of the hole system; and S5, finish machining is started, the calibration frequency is set, and the calibration reference hole is detected and compensated regularly in the finish machining process till finish machining is completed. The manufacturing precision is effectively improved, and meanwhile the machining efficiency and the quality stability of products are improved.

Description

Technical Field

[0001] The invention relates to the field of metal material mechanical processing, and in particular to a method for processing deep holes of a large boring and milling machine. Background Art

[0002] In the field of mechanical processing technology, especially in the manufacturing process of large parts, the processing of hole systems is a key link. These hole systems are usually characterized by large diameters and deep holes, and are common in industries such as aviation, shipbuilding, and heavy machinery. Large parts usually weigh 70-100 tons, which makes their processing more complicated. Existing large boring and milling machines have the following difficulties when processing such deep hole systems:

[0003] 1. Long processing time: The processing time of the hole system on large parts is usually as long as dozens of hours or even days. Long-term operation will put the mechanical parts of the machine tool in a state of continuous high load, resulting in fatigue accumulation, and put forward higher requirements on the stability and reliability of the machine tool. Especially for large parts weighing 70-100 tons, their huge weight puts forward more stringent requirements on the load-bearing capacity and stability of the machine tool.

[0004] 2. High risk of coordinate shift: Due to the long processing time, the probability of coordinate shift of CNC equipment during long-term operation increases significantly. Coordinate shift may be caused by a variety of factors, including but not limited to: long-term operation causes the temperature of various machine tool components to rise, thermal deformation causes coordinate shift; long-term use causes wear of machine tool guide rails, lead screws and other components, affecting positioning accuracy; long-term operation may cause instability of the electrical system, resulting in distortion of control signals.

[0005] 3. Abnormal spindle positioning accuracy: Abnormal spindle positioning accuracy at different positions is also one of the important reasons for the excessive tolerance of the processing hole system. Specifically, it manifests as: Insufficient spindle rigidity: During deep hole processing, the spindle is subjected to a large cutting force, and insufficient rigidity will cause spindle deformation and affect positioning accuracy; Improper cutting parameters: Improper settings of parameters such as cutting speed and feed rate may cause spindle vibration and affect processing accuracy; Tool wear: Long-term use causes tool wear, affecting processing quality and accuracy.

[0006] 4. Geometric tolerance out of tolerance: Under the combined effect of the above factors, the geometric tolerance of the processed hole system is likely to exceed the design requirements. Geometric tolerance out of tolerance not only affects the functional performance of parts, but may also cause the failure of the entire assembly.

[0007] Therefore, improving machining accuracy and stability and reducing geometric tolerance deviations are issues that need to be urgently addressed in the current field of mechanical machining technology. Summary of the invention

[0008] The invention aims to provide a method for machining deep holes of a large boring and milling machine, so as to improve the machining accuracy and machining efficiency of the large boring and milling machine when machining deep holes.

[0009] To achieve the above object, the present invention adopts the following technical solution: a method for processing deep holes of a large boring and milling machine, comprising the following steps:

[0010] S1. Rough machining of the hole system on the workpiece according to product requirements;

[0011] S2. Before the workpiece is transferred from the rough processing equipment to the finishing equipment, the coordinates and error vectors of the workpiece are evaluated according to the type of geometric tolerance:

[0012] S2.1, Coaxiality detection: First calculate the fitting center of each hole in the hole system, select the reference hole, and then project the fitting center of each hole into the plane perpendicular to the hole system. The fitting center of the reference hole is the origin of the coordinate system. The coordinates of the fitting center of each hole are (X n , Y n , Z n );

[0013] S2.2, Parallelism detection: First calculate the fitting axis of each hole in the hole system, select the reference hole, then translate the fitting axis of each hole in the hole system to the same coordinate system, and make the starting points coincide, and then project each fitting axis to the plane perpendicular to the hole system. The coordinates of the fitting axis of each hole are (X n , Y n , Z n );

[0014] S2.3, Cylindricity detection: Take multiple detection sections along the axial direction in the hole, and the detection intervals between two adjacent detection sections are equal. Calculate the fitting center of each detection section, and further fit each fitting center to the axis of the hole. Each fitting center is projected into a plane perpendicular to the axis. The coordinates of the fitting center of each detection section are (X n , Y n , Z n );

[0015] S3, fix the workpiece to the finishing equipment for alignment, then locate the finishing hole reference, establish the machine tool coordinate system through the processing equipment according to the geometric tolerance type, and obtain the hole coordinate (X' n , Y' n , Z' n ), and then obtain the coordinate system deviation, including: X-axis direction deviation εn x =X n -X′ n , Y-axis deviation εn y =Y n -Y′ n , Z-axis deviation εnz =Z n -Z′ n ;

[0016] S4, according to the type of geometric tolerance, the coordinate system deviation obtained in step S3 is used to compensate the processing equipment. After the compensation is completed, a corresponding calibration reference hole is designed at each hole of the hole system, the calibration reference hole coincides with the axis of the hole, and the aperture of the calibration reference hole is smaller than the design aperture of the hole system;

[0017] S5. Start finishing and set the calibration frequency. During the finishing process, the calibration reference hole is regularly inspected and compared with the initial coordinates of the calibration reference hole to obtain the accuracy deviation. The coordinate system of the processing equipment is compensated according to the deviation until the finishing is completed.

[0018] Furthermore, in step S2, the device for evaluating the coordinates of the workpiece is a three-dimensional coordinate measuring machine, and the working environment of the three-dimensional coordinate measuring machine is a constant temperature and humidity environment.

[0019] Further, in step S4, the difference between the calibration reference hole and the designed hole diameter of the hole system is the radial process calibration reference allowance, and the radial process calibration reference allowance is 0.02-0.05 mm.

[0020] Further, in step S5, the frequency is calibrated based on the change in ambient temperature, which is 2-5°C.

[0021] Furthermore, in steps S3, S4 and S5, the finish-machined hole system of the workpiece is checked by using a dial indicator or a micrometer, and the reading of the dial indicator or the micrometer is not greater than 0.01 mm.

[0022] Further, in step S2.3, the detection interval is 200-300 mm.

[0023] Furthermore, for the parallel hole system, calibration reference holes are provided at both ends of the hole.

[0024] Further, in step S5, when the radial machining allowance of the workpiece is consistent with the radial process calibration reference allowance, a final calibration is performed, followed by continuous processing to the finished product.

[0025] Further, in step S4, the processing equipment continuously completes the processing of the calibration reference hole under a stable accuracy state.

[0026] Furthermore, the finish-machined hole datum in step S3 is consistent with the hole datum for coordinate evaluation in step S2.

[0027] When large-diameter deep holes are processed on existing large parts, the main measures taken to solve the problem of machining accuracy are:

[0028] One is to use a laser tracker to perform precision detection during the processing. By controlling the light to track the movement of the reflective target, the distance of the reflective target ball and the angular coordinates of the rotation axis are measured at the same time to determine the three-dimensional coordinates of the target point. However, the laser tracker is not only complicated to operate, but also has detection blind spots for some hole systems, and cannot effectively guarantee the processing accuracy to meet product requirements. For example, if the aperture of the single holes on both sides of a single hole in the axial hole system is smaller than its aperture, the laser will interfere during the reflection process, affecting the detection accuracy.

[0029] The second is to carry out a trial processing before formal finishing. After the trial processing, the workpiece is removed from the processing equipment and then transferred to a three-coordinate measuring machine for precision testing. Compared with the laser tracker, this method can effectively ensure the detection accuracy, but the size and weight of large parts are very large. Not only do they require professional facilities to carry them back and forth, increasing costs and labor, but also when the workpiece is fixed to the processing equipment again, it needs to be realigned. This process is prone to new errors. Even if the three-coordinate measuring machine determines that the previous processing accuracy meets the requirements, it is difficult to guarantee the subsequent processing accuracy, which in turn causes the finished product to ultimately fail to meet the precision requirements.

[0030] Currently, traditional measures are still unable to effectively solve the problem of machining accuracy of large-diameter deep holes of large parts. Therefore, the present invention provides a machining method that can be monitored and compensated online, which not only ensures machining accuracy but also improves machining efficiency and stability.

[0031] The principles and beneficial effects of this program are:

[0032] In actual application, the present invention performs coordinate assessment on the rough-machined workpiece in the transfer link after rough machining and before fine machining, measures the error of the workpiece itself after rough machining, and then performs coordinate assessment again after the workpiece is fixed on the processing equipment, measures the error of the machine tool itself at each processing position in this state, and then compensates the processing equipment with the coordinate system deviation obtained after the two errors are superimposed, so that most of the workpiece precision error is compensated; then the compensated processing equipment is used to process the calibration reference hole before formal fine machining, because the calibration reference hole is completed when the processing equipment is in a stable state and has high precision, it basically meets the workpiece processing requirements; moreover, the workpiece is always fixed on the processing equipment in the subsequent fine machining process, and only the error of the processing equipment itself will exist in the subsequent machining process. Therefore, the error direction and value at this time can be effectively judged by online detection of the coordinate position of the calibration reference hole, and the processing equipment can be compensated in real time to ensure the machining accuracy.

[0033] 1. This scheme makes full use of the transfer gap between rough machining and fine machining, and detects the workpiece through a three-coordinate measuring machine. Since the detection environment of the three-coordinate measuring machine is constant temperature and humidity, the coordinate detection result is more accurate and reliable. Therefore, the coordinate system obtained by the three-coordinate measuring machine is used as a reference to judge and compensate the accuracy error of the processing equipment, so that the processing equipment can complete the initial accuracy calibration, and the calibration reference hole is processed with this accuracy, so that the calibration reference hole basically replicates the measurement result of the three-coordinate measuring machine, and then the calibration reference hole can be used as a detection reference in the subsequent fine machining process. Online monitoring and real-time compensation can be achieved without removing the workpiece from the machine tool. The overall operation is simpler, less difficult and more accurate than traditional laser trackers or trial processing measures.

[0034] 2. This solution decomposes the coaxiality, parallelism, and cylindricity errors of a hole or hole system into coordinate values ​​and dimensions that are directly available to the CNC boring and milling machine. The operator can directly and more accurately adjust the position and posture of the machine tool to ensure that the machining accuracy of each hole or hole system meets the design requirements, and the machining accuracy of the hole system is significantly improved.

[0035] 3. This solution does not require the workpiece to be removed from the processing equipment or to be shut down during the entire finishing process, and achieves online monitoring and real-time compensation, effectively improving processing efficiency and stability, reducing wear caused by frequent startup of processing equipment, and extending the service life of the equipment.

[0036] 4. In the process of processing, this solution realizes online monitoring and compensation by calibrating the reference hole, which ensures the real-time accuracy of the product and reduces the accuracy error, thereby effectively reducing the number of process inspections during the product processing, shortening the processing cycle, and reducing the waste of processing resources and costs.

[0037] 5. The ideal processing environment for workpieces is a constant temperature environment. However, due to the huge size of large workpieces, the corresponding constant temperature environment requires a huge space and is very expensive. Therefore, in actual processing and production, most manufacturers process workpieces in a conventional environment. The accuracy of processing equipment in a conventional environment will change after long-term operation, so regular calibration is required. However, due to differences in equipment status and accuracy stability of processing equipment from different manufacturers, the accuracy changes over time differently. If only the time period is used as the basis for the calibration frequency, it is easy to cause over-calibration or calibration delay. Over-calibration will increase the operating time of the machine tool, thereby causing the temperature of various machine tool components to rise. Calibration delays cause the coordinate system deviation to gradually accumulate and exceed the geometric tolerance range required by the design.

[0038] Therefore, taking into account the differences in equipment status and precision stability of different processing equipment, the calibration frequency in this scheme is set based on the change in ambient temperature. The heat generated during the operation of the processing equipment will indirectly affect the ambient temperature. When the ambient temperature changes by 2-5°C, the internal structure of most processing equipment will also expand due to the temperature, and then the geometric shape will change, affecting the processing accuracy. Therefore, setting the calibration frequency by the change in ambient temperature can not only ensure timely calibration, but also reduce the number of calibrations to ensure processing efficiency.

[0039] 6. In step S4 of this scheme, the radial process calibration reference allowance is limited to 0.02-0.05mm, which is within the range of the last cutter finishing amount. Completing the hole allowance in one cut can avoid the cutter marks caused by the joint of the cutters and make the inner hole surface complete. Secondly, if the radial process calibration reference allowance is too large, the processing cycle after the last calibration reference will be long. The long processing cycle will cause the processing equipment to be affected by environmental factors and precision errors will occur again, which cannot be corrected in time, affecting the final precision of the workpiece.

[0040] 7. The processing method of this scheme has no strict requirements on temperature conditions and is also applicable to processing environments with non-constant temperature conditions. It has strong versatility and conforms to production practice. It can effectively improve the quality stability of products with large diameter and deep holes and improve industry standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the coaxiality of the axial hole system according to an embodiment of the present invention.

[0042] Figure 2 Schematic diagram of coaxiality deviation according to an embodiment of the present invention.

[0043] Figure 3 Schematic diagram of the parallelism of a parallel hole system according to an embodiment of the present invention.

[0044] Figure 4 Schematic diagram of parallelism deviation according to an embodiment of the present invention.

[0045] Figure 5 Schematic diagram of deep hole cylindricity according to an embodiment of the present invention.

[0046] Figure 6 Schematic diagram of the deviation of the fitting centers of the cylindricity detection section according to an embodiment of the present invention.

[0047] Figure 7 It is a schematic diagram of the calibration reference of the axial hole system according to an embodiment of the present invention.

[0048] Figure 8 Schematic diagram of a parallel hole system calibration benchmark according to an embodiment of the present invention.

[0049] Fig. 9Schematic diagram of deep hole calibration reference according to an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The following is further described in detail through specific implementation methods:

[0051] The embodiment is basically as follows Figure 1-Figure 9 As shown: A method for processing deep holes of a large boring and milling machine includes the following steps:

[0052] S1. Rough or semi-finish the holes on the workpiece according to product requirements.

[0053] S2. Before the workpiece is transferred from the rough processing equipment to the fine processing equipment, the workpiece is fixed on the three-dimensional coordinate measuring machine using the transfer gap. According to the type of geometric tolerance, the coordinates and error vectors of the workpiece are evaluated by the three-dimensional coordinate measuring machine. The working environment of the three-dimensional coordinate measuring machine is a constant temperature and humidity environment:

[0054] S2.1. Coaxiality detection: combined Figure 1 Take the axial hole system shown in the figure as an example, which includes hole A, hole B and hole C. The axial direction of the hole system is parallel to the Z axis of the coordinate system. First, the fitting center of each hole in the hole system is calculated by a three-dimensional coordinate measuring machine, and hole A is selected as the reference hole. Then, the fitting center of each hole is projected into the XY plane, as shown in Figure 2 As shown, the center of the fitting circle of hole A coincides with the origin of the coordinate system, and the coordinates of holes B and C are (X b , Y b ,0)、(X c , Y c , 0), that is, the coordinate values ​​of hole B and hole C are the coaxiality deviations of hole B and hole C relative to hole A.

[0055] S2.2, Parallelism detection: Combined Figure 3 Take the parallel hole system shown in the figure as an example, which includes hole A, hole B and hole C. The axial direction of the hole system is parallel to the Y axis of the coordinate system. First, the fitting axis of each hole in the hole system is calculated by the three-coordinate measuring instrument, and hole A is selected as the reference hole. The fitting axis of hole A coincides with the Y axis of the coordinate system. Then, Figure 4 As shown in the figure, the fitting axis of each hole in the hole system is translated to the same coordinate system, and the starting point coincides with the origin, and the coordinate A1 (Y a ,0),B1(Y b , Z b ) and C1(Y c , Z c ), and then project each fitting axis into the XZ plane. The projection coordinates of the fitting axis of each hole in the XZ plane are A2(0,0), B2(X b , Z b ), C2(X c , Zc ), the above is the deviation value of parallelism in the main plane.

[0056] S2.3, Cylindricity detection: combined Figure 5 Taking the deep hole shown in the figure as an example, the axial direction of the deep hole is parallel to the Z axis of the coordinate system. Four detection sections are taken along the axial direction in the hole, namely positions 1-4. The detection interval L between two adjacent detection sections is equal. The fitting center of each detection section is calculated by the three-coordinate measuring instrument, and each fitting center is further fitted as the axis of the hole, i.e., the Z axis. Each fitting center is projected into the XY plane, as shown in Figure 6 As shown, the coordinates of the fitting center of each detection section are A1(Xa1, Y a1 ), A2(Xa2, Y a2 ),A3(Xa3,Y a3 ),A4(Xa4,Y a4 ), combined with the diameter deviation Δ at the detection section φDn ,φD1、φD 2、 φD 3、 φD4 corresponds to the diameter of the detection section at positions 1-4, and the center deviation and diameter size deviation are equivalent to the cylindrical deviation. Preferably, the detection interval is 200-300mm; when the hole depth of a single aperture is 300-500mm, the detection interval is 200mm, and when the hole depth of a single aperture is about 1m, the detection interval is 300mm; and when selecting the detection position, the hole mouth position is selected first, and then the position in the middle of the hole is selected.

[0057] The process of calculating the fitting center by a three-dimensional coordinate measuring instrument and calculating the fitting axis by the least square method in step S2 is prior art and will not be described in detail here.

[0058] S3, fix the workpiece to the finishing processing equipment, i.e., a large CNC boring and milling machine, and align it, then locate the finishing hole datum, which is consistent with the coordinate evaluation datum in step S2; use the processing equipment to establish the machine tool coordinate system according to the geometric tolerance type, and obtain the coordinate (X' n , Y' n , Z' n ), and then the fine-machined hole is checked by a dial indicator or a micrometer, and the coordinate system obtained by the three-dimensional coordinate measuring machine in step S2 is used as a reference, and the two coordinate systems are compared and judged in combination with the detection deviation to obtain the coordinate system deviation, including: X-axis direction deviation εn x =X n -X′ n , Y-axis deviation εn y =Y n -Y′ n , Z-axis deviation εn z =Z n -Z′n .

[0059] by Figure 1 , Figure 2 For example, the coordinates of hole C obtained by the processing equipment are (X' c , Y' c , 0): X-axis deviation εc x =X c -X′ c , Y-axis deviation εc y =Y c -Y′ c , Z-axis deviation εb z =0.

[0060] by Figure 3 , Figure 4 Take hole B as an example, the coordinates of hole B obtained by the processing equipment are (X' b , Y' b , Z' b ): X-axis deviation εb x =X b -X′ b , Y-axis deviation εb y =Y b -Y′ b , Z-axis deviation εb z =Z b -Z′ b .

[0061] by Figure 5 , Figure 6 Taking position 3 as an example, the coordinates of the center of the circle obtained by the processing equipment at position 3 are (X' a3 , Y' a3 , Z' a3 ): Deviation in the X-axis direction Deviation in Y-axis direction Deviation in Z-axis direction

[0062] S4. According to the type of geometric tolerance, the coordinate system deviation obtained in step S3 is compensated for the processing equipment. After the compensation is completed, the corresponding calibration reference hole φd is designed at each hole of the hole system. n ,like Figure 7 , Figure 8 , Fig. 9 As shown, the calibration reference hole coincides with the axis of the hole, the aperture of the calibration reference hole is smaller than the design aperture of the hole system, and the processing equipment continuously completes the processing of the calibration reference hole under a stable precision state, ensuring that the calibration reference hole fully meets the processing precision requirements; for the parallel hole system, calibration reference holes are set at both ends of the hole system, and when the hole system includes stepped holes, calibration reference holes are set according to different apertures.

[0063] The difference between the calibration reference hole and the designed aperture of the hole system is the radial process calibration reference allowance, which is 0.02-0.05mm, and is within the range of the last finishing cut of the processing equipment. Completing the processing allowance with one cut can avoid the cutting marks caused by the joint of the cutters, and make the inner hole surface complete. Secondly, if the radial process calibration reference allowance is too large, the processing cycle after the last calibration reference will be long. The long processing cycle will cause the processing equipment to be affected by environmental factors and precision errors will occur again, which cannot be corrected in time, affecting the final precision of the workpiece.

[0064] The coordinate system obtained by the three-coordinate measuring machine is used as a reference to judge and compensate the accuracy error of the processing equipment, so that the processing equipment can complete the initial accuracy calibration, and the calibration reference hole is processed with this accuracy, so that the calibration reference hole basically replicates the measurement result of the three-coordinate measuring machine. The calibration reference hole can be used as a detection reference in the subsequent finishing process, and online monitoring and real-time compensation can be achieved without removing the workpiece from the machine tool.

[0065] S5. Start finishing and set the calibration frequency. During the finishing process, the calibration reference hole is regularly inspected and compared with the initial coordinates of the calibration reference hole to obtain the accuracy deviation. The coordinate system of the processing equipment is compensated according to the deviation until the finishing is completed. When the radial processing allowance of the workpiece is consistent with the radial process calibration reference allowance, the last calibration is performed, followed by continuous processing to the finished product.

[0066] Among them, the calibration frequency is based on the ambient temperature change, and the ambient temperature change is 2-5°C; specifically, according to the accuracy requirements of different processing equipment, the calibration frequency is different during actual processing. For example: if the accuracy of the processing equipment is 0.02mm, the calibration frequency is set based on the ambient temperature change of 2-3°C; if the accuracy of the processing equipment is 0.05mm, the calibration frequency is set based on the ambient temperature change of 5°C.

[0067] Among them, in steps S3, S4 and S5, the fine-machined hole system of the workpiece is checked by a dial indicator or a micrometer. The dial indicator or the micrometer is installed on the spindle of the processing equipment, the measuring head is in contact with the hole surface, and the reading of the dial indicator or the micrometer is not greater than 0.01mm to ensure the processing accuracy and product accuracy.

[0068] Specific working principle: In actual application, the three-coordinate measuring instrument is used to evaluate the coordinates of the rough-machined workpiece in the transfer link after rough machining and before fine machining, and the errors of the workpiece itself after rough machining are measured. Then, the workpiece is fixed on the processing equipment, and the coordinates are evaluated again and the errors caused by the machine tool structure itself are measured. Then, the two errors are compared and judged based on the measurement results of the three-coordinate measuring instrument, and the coordinate system deviation is obtained. The processing equipment is compensated according to the coordinate system deviation, so that most of the workpiece precision error is compensated.

[0069] Then, the calibration reference hole is processed by the compensated processing equipment before the formal finishing. Since the calibration reference hole is processed when the processing equipment is in a stable state and with high precision, it basically meets the workpiece processing requirements and basically replicates the measurement coordinates of the three-coordinate measuring instrument. Moreover, in the subsequent finishing process, the workpiece is always fixed on the processing equipment, and only the error of the processing equipment itself will exist in the subsequent processing process. Therefore, the coordinate position of the calibration reference hole can be detected online to effectively determine the error direction and value at this time, and the processing equipment can be compensated in real time to ensure the processing accuracy.

[0070] The processing method of this scheme decomposes the coaxiality, parallelism and cylindricity errors of a hole or hole system into coordinate values ​​and dimensions directly available to a CNC boring and milling machine, and performs online monitoring and compensation by establishing a calibration reference. Especially for the processing of deep and long holes (systems) and when the accuracy approaches or exceeds the conventional accuracy of the machine tool, this method can ensure the accuracy of the processed holes in real time, effectively reduce the number of process inspections during product processing, and is also applicable to processing environments under non-constant temperature conditions, which is in line with actual production.

[0071] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for processing deep holes of a large boring and milling machine, characterized in that: The following steps are involved: S1. Rough machining of the hole system on the workpiece according to product requirements; S2. Before the workpiece is transferred from the rough processing equipment to the finishing equipment, the coordinates and error vectors of the workpiece are evaluated according to the type of geometric tolerance: S2.1, Coaxiality detection: First calculate the fitting center of each hole in the hole system, select the reference hole, and then project the fitting center of each hole into the plane perpendicular to the hole system. The fitting center of the reference hole is the origin of the coordinate system. The coordinates of the fitting center of each hole are (X n , Y n , Z n ); S2.2, Parallelism detection: First calculate the fitting axis of each hole in the hole system, select the reference hole, then translate the fitting axis of each hole in the hole system to the same coordinate system, and make the starting points coincide, and then project each fitting axis to the plane perpendicular to the hole system. The coordinates of the fitting axis of each hole are (X n , Y n , Z n ); S2.3, Cylindricity detection: Take multiple detection sections along the axial direction in the hole, and the detection intervals between two adjacent detection sections are equal. Calculate the fitting center of each detection section, and further fit each fitting center to the axis of the hole. Each fitting center is projected into a plane perpendicular to the axis. The coordinates of the fitting center of each detection section are (X n , Y n , Z n ); S3, fix the workpiece to the finishing equipment for alignment, then locate the finishing hole reference, establish the machine tool coordinate system through the processing equipment according to the geometric tolerance type, and obtain the hole coordinate (X' n , Y' n , Z' n ), and then obtain the coordinate system deviation, including: X-axis direction deviation εn x =X n -X′ n , Y-axis deviation εn y =Y n -Y′ n , Z-axis deviation εn z =Z n -Z′ n ; S4, according to the type of geometric tolerance, the coordinate system deviation obtained in step S3 is used to compensate the processing equipment. After the compensation is completed, a corresponding calibration reference hole is designed at each hole of the hole system, the calibration reference hole coincides with the axis of the hole, and the aperture of the calibration reference hole is smaller than the design aperture of the hole system; S5. Start finishing and set the calibration frequency. During the finishing process, the calibration reference hole is regularly inspected and compared with the initial coordinates of the calibration reference hole to obtain the accuracy deviation. The coordinate system of the processing equipment is compensated according to the deviation until the finishing is completed.

2. The method for processing deep holes of a large boring and milling machine according to claim 1, characterized in that: In step S2, the device for evaluating the coordinates of the workpiece is a three-dimensional coordinate measuring machine, and the working environment of the three-dimensional coordinate measuring machine is a constant temperature and humidity environment.

3. The method for processing deep holes of a large boring and milling machine according to claim 1, characterized in that: In step S4, the difference between the calibration reference hole and the designed hole diameter of the hole system is the radial process calibration reference allowance, and the radial process calibration reference allowance is 0.02-0.05 mm.

4. The method for processing deep holes of a large boring and milling machine according to claim 1, characterized in that: In step S5, the frequency is calibrated based on the change in ambient temperature, which is 2-5°C.

5. The method for processing deep holes of a large boring and milling machine according to claim 1, characterized in that: In steps S3, S4 and S5, the finish-machined hole system of the workpiece is checked by using a dial indicator or a micrometer, and the reading of the dial indicator or the micrometer is not greater than 0.01 mm.

6. The method for processing deep holes of a large boring and milling machine according to claim 2, characterized in that: In step S2.3, the detection interval is 200-300 mm.

7. The method for processing deep holes of a large boring and milling machine according to claim 6, characterized in that: For parallel hole systems, calibration reference holes are set at both ends of the hole.

8. The method for processing deep holes of a large boring and milling machine according to claim 4, characterized in that: In step S5, when the radial machining allowance of the workpiece is consistent with the radial process calibration reference allowance, a final calibration is performed, followed by continuous processing to the finished product.

9. A method for processing deep holes in a large boring and milling machine according to claim 8, characterized in that: In step S4, the processing equipment continuously completes the processing of the calibration reference hole under a stable accuracy state.

10. The method for processing deep holes of a large boring and milling machine according to claim 1, characterized in that: The finishing hole datum in step S3 is consistent with the hole datum for coordinate evaluation in step S2.

Images