A method for processing a deep hole of a large boring and milling machine

Abstract

The application relates to the field of metal material machining, and discloses the following steps: S1, rough machining is performed on a hole system on a workpiece according to product requirements; S2, coordinate and error vector evaluation is performed on the workpiece according to a shape and position tolerance type before the workpiece is transferred from a rough machining device to a finish machining device, so that coordinates (X n , Y n , Z n ) are obtained; S3, the workpiece is fixed to the finish machining device to perform alignment and positioning finish machining hole reference, a coordinate system is established according to the shape and position tolerance type, so that coordinates (X' n , Y' n , Z' n ) are obtained, and then a coordinate system deviation is obtained; S4, coordinate system deviation compensation is performed on the machining device according to the shape and position tolerance type, and corresponding calibration reference holes are designed at each hole of the hole system; and S5, finish machining is started, calibration frequency is formulated, the calibration reference holes are detected and compensated periodically in the finish machining process, and the finish machining is completed. The application effectively improves manufacturing precision, and simultaneously improves machining efficiency and quality stability of products.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of metal material machining, in particular to a machining method for deep holes of a large boring-milling machine. BACKGROUND

[0002] In the field of machining technology, especially in the manufacturing process of large parts, the machining of hole systems is a key link. These hole systems usually have the characteristics of large diameter and deep holes, and are commonly used in the aviation, shipbuilding, heavy machinery and other industries. The weight of large parts is usually 70-100 tons, which makes the machining process more complex. The existing large boring-milling machines have the following difficulties when machining such deep hole systems:

[0003] 1. Long processing time: The machining time of hole systems on large parts usually lasts for tens of hours or even days, and long-time operation will put the mechanical parts of the machine tool in a state of continuous high load, leading to fatigue accumulation, and higher requirements for the stability and reliability of the machine tool. Especially for large parts with a weight of 70-100 tons, the huge weight puts higher requirements on the load-bearing capacity and stability of the machine tool.

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

[0005] 3. Abnormal positioning accuracy of main shaft: Abnormal positioning accuracy of the main shaft at different positions is also one of the important reasons for the out-of-tolerance of the shape and position tolerance of the machined hole system. The specific performance is: insufficient rigidity of the main shaft: in the process of deep hole machining, the main shaft bears a large cutting force, and insufficient rigidity will cause deformation of the main shaft, affecting the positioning accuracy; improper cutting parameters: unreasonable setting of cutting speed, feed rate and other parameters may cause main shaft vibration, affecting the machining accuracy; tool wear: long-time use leads to tool wear, affecting the machining quality and accuracy.

[0006] 4. Out-of-tolerance of shape and position tolerance: Under the joint action of the above factors, the shape and position tolerance of the machined hole system is easy to exceed the design requirements. Out-of-tolerance of shape and position tolerance not only affects the functional performance of the part, but also may lead to failure of the entire assembly.

[0007] Therefore, improving the machining accuracy and stability and reducing the out-of-tolerance of shape and position tolerance are the problems to be solved in the current field of machining technology. SUMMARY

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

[0009] To achieve the above-mentioned purpose, the application adopts the following technical scheme: a machining method for deep holes of a large boring and milling machine, comprising the following steps:

[0010] S1, rough machining of hole systems on a workpiece according to product requirements;

[0011] S2, coordinate and error vector evaluation of the workpiece according to the type of geometric tolerance before the workpiece is transferred from a rough machining device to a fine machining device:

[0012] S2.1, coaxiality detection: first, the fitting centers of each hole in the hole system are calculated, a reference hole is selected, then the fitting centers of each hole are projected into a plane perpendicular to the hole system, the fitting center of the reference hole is the origin of the coordinate system, and the coordinates of the fitting centers of each hole are (X n , Y n , Z n );

[0013] S2.2, parallelism detection: first, the fitting axes of each hole in the hole system are calculated, a reference hole is selected, then the fitting axes of each hole in the hole system are translated into the same coordinate system with the starting points coinciding, and then the fitting axes are projected into a plane perpendicular to the hole system, and the coordinates of the fitting axes of each hole are (X n , Y n , Z n );

[0014] S2.3, cylindricity detection: a plurality of detection sections are taken in the hole along the axial direction, the detection intervals between adjacent two detection sections are equal, the fitting centers of each detection section are calculated, and the fitting centers are further fitted as the axis of the hole, the fitting centers are projected into a plane perpendicular to the axis, and the coordinates of the fitting centers of each detection section are (X n , Y n , Z n );

[0015] S3, the workpiece is fixed to the fine machining device for alignment, then the fine machining hole reference is positioned, the machine tool coordinate system is established by the machining device according to the type of geometric tolerance, the hole coordinates (X' n , Y' n , Z' n ) are obtained, and the coordinate system deviation is obtained, including: X-axis direction deviation εn x = X n -X′ n , Y-axis direction deviation εn y = Y n -Y′ n , and Z-axis direction deviation εnz = Z n -Z' n ;

[0016] S4, according to the form and position tolerance type, the coordinate system deviation obtained in step S3 is compensated for the machining equipment, and after the compensation is completed, corresponding calibration reference holes are designed at each hole of the hole system, the calibration reference holes coincide with the axis of the hole, and the hole diameter of the calibration reference hole is smaller than the design hole diameter of the hole system;

[0017] S5, start finishing, and make calibration frequency, periodically detect the calibration reference hole during finishing and compare with the initial coordinates of the calibration reference hole, get the precision deviation, and compensate the coordinate system of the machining equipment according to the deviation, until the finishing is completed.

[0018] Further, in step S2, the equipment for coordinate evaluation of the workpiece is a three-coordinate measuring instrument, and the working environment of the three-coordinate measuring instrument is a constant temperature and humidity environment.

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

[0020] Further, in step S5, the calibration frequency is based on the environmental temperature change, and the environmental temperature change is 2-5℃.

[0021] Further, in steps S3, S4 and S5, the finishing hole system of the workpiece is checked by a dial gauge or a micrometer, and the dial gauge or the micrometer reading is not greater than 0.01mm.

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

[0023] Further, for the parallel hole system, calibration reference holes are arranged 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, the last calibration is performed, and then continuous machining is performed to the finished product.

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

[0026] Further, the finishing hole reference in step S3 is consistent with the hole reference for coordinate evaluation in step S2.

[0027] When machining large-diameter deep hole systems of large parts, the main measures taken to solve the machining precision problem are:

[0028] One is to use a laser tracker to detect precision during processing, by controlling the movement of the light tracking reflection target, while measuring the distance of the reflection target ball and the angle coordinate of the rotation axis, to determine the three-dimensional coordinates of the target point; however, the laser tracker is not only complex to operate, but also has a detection blind area for some hole systems, which cannot effectively ensure the processing precision to meet the product requirements. For example, if the diameter of a single hole on one side of an axial hole system is smaller than that of the single hole on the other side, the laser will interfere during the reflection process, affecting the detection accuracy.

[0029] Two is to perform a trial processing before formal finishing, after trial processing, the workpiece is taken off from the processing equipment, and then transferred and placed on a three-coordinate measuring instrument for precision detection. This method can indeed effectively ensure the detection accuracy compared with the laser tracker, but the volume and weight of large parts are very large, which not only needs professional facilities for carrying back and forth, increasing the cost and labor amount of workers, but also needs to be re-aligned when the workpiece is fixed to the processing equipment again. This process is easy to produce new errors, even if the previous processing precision meets the requirements through the three-coordinate measuring instrument, it is difficult to ensure the subsequent processing precision, and thus the final processing product cannot meet the precision requirements.

[0030] At present, the traditional measures still cannot effectively solve the processing precision problem of large-diameter deep hole systems of large parts, therefore, the present application provides a processing method which can be monitored and compensated online, which can ensure processing precision and improve processing efficiency and stability.

[0031] The principle and beneficial effects of the present application are as follows:

[0032] In actual application, the present application evaluates the coordinates of the workpiece after rough machining and before finishing, measures the error of the workpiece itself after rough machining, then fixes the workpiece on the processing equipment and evaluates the coordinates again, measures the error of the machine tool itself at each processing position, then the coordinate system deviation obtained by superimposing the two errors is used to compensate the processing equipment, so that the workpiece precision error is mostly compensated; then the calibrated reference hole is processed before formal finishing using the compensated processing equipment. Since the calibrated reference hole is processed when the processing equipment is stable and has high precision, it basically meets the workpiece processing requirements. Moreover, the workpiece is always fixed on the processing equipment during subsequent finishing process, and only the error of the processing equipment itself exists in the subsequent processing process, therefore, the coordinate position of the calibrated reference hole is detected online to effectively judge the error direction and value, and the processing equipment is compensated in real time to ensure the processing precision.

[0033] 1、This scheme makes full use of the transfer gap after rough machining and before finishing, and detects the workpiece by a three-coordinate measuring instrument. Since the detection environment of the three-coordinate measuring instrument is constant temperature and humidity, the coordinate detection result is more accurate and reliable. Therefore, the coordinate system obtained by the three-coordinate measuring instrument is used as a reference to judge and compensate the precision error of the machining equipment, so that the machining equipment completes the initial precision calibration, and the precision machining calibration reference hole is machined, so that the calibration reference hole basically reproduces the measurement result of the three-coordinate measuring instrument, and the calibration reference hole can be used as a detection reference in the subsequent finishing process, without taking the workpiece off the machine tool for online monitoring and real-time compensation. The overall operation is simpler, lower in difficulty and higher in accuracy than traditional laser trackers or trial machining measures.

[0034] 2、This scheme decomposes the coaxiality, parallelism and cylindricity error of the hole or hole system into coordinate values and sizes directly available for the numerical control boring and milling machine. The operator can directly and more accurately adjust the position and attitude of the machine tool to ensure that the machining precision of each hole or hole system meets the design requirements, and the machining precision of the hole system is significantly improved.

[0035] 3、This scheme does not need to take the workpiece off the machining equipment or stop the machine during the entire finishing process, realizing online monitoring and real-time compensation, effectively improving the machining efficiency and stability, reducing wear caused by frequent start of the machining equipment, and prolonging the service life of the equipment.

[0036] 4、This scheme realizes online monitoring and compensation through the calibration reference hole during the machining process, ensuring the real-time precision of the product, reducing the precision error, and effectively reducing the number of process detection times during the product machining process, shortening the machining cycle, and reducing the waste of machining resources and costs.

[0037] 5、The ideal machining environment for the workpiece is a constant temperature environment. However, due to the large size of large workpieces, the corresponding constant temperature environment space is also very large, and the cost is very high. Therefore, during actual machining production, most manufacturers perform workpiece machining in a conventional environment. The precision of the machining equipment will change after long-time operation in a conventional environment, so it needs to be calibrated regularly. However, due to differences in equipment state and precision stability of machining equipment of different manufacturers, the precision changes with time. If only the time period is used as the basis for calibration frequency, it is easy to lead to over-calibration or delayed calibration. Over-calibration will increase the running time of the machine tool, causing the temperature of each part of the machine tool to rise. Delayed calibration causes the coordinate system deviation to gradually accumulate and exceed the design requirement shape tolerance range.

[0038] Therefore, considering that the equipment states and precision stability of different machining equipment are different, the calibration frequency is set based on the environmental temperature change in the scheme, the heat generated during the operation of the machining equipment indirectly acts on the environmental temperature, when the environmental temperature change is 2-5 DEG C, the internal structure of most machining equipment will also be heat expanded due to temperature, and then the geometric shape is changed to affect the machining precision, therefore, the calibration frequency is set through the environmental temperature change, so that timely calibration can be ensured, and the calibration frequency can be reduced to ensure the machining efficiency.

[0039] 6、The radial process calibration reference allowance in step S4 of the scheme is limited to 0.02-0.05 mm, the allowance is within the finishing amount range of the last cut, the hole allowance can avoid the knife mark generated by the knife connection, and the inner hole surface is complete; secondly, the radial process calibration reference allowance is too large, so that the machining period after the last calibration reference is long, the long machining period leads to the machining equipment affected by environmental factors and cannot be corrected in time, and the final precision of the workpiece is affected.

[0040] 7、The machining method of the scheme has no strict requirement on the temperature condition, is suitable for the machining environment of non-constant temperature condition, is strong in universality, conforms to the production practice, effectively improves the quality stability of the product with a large-diameter deep hole system, and improves the industry standard. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 It is an axial hole system coaxial diagram of the embodiment of the application.

[0042] Figure 2 It is a coaxial deviation diagram of the embodiment of the application.

[0043] Figure 3 It is a parallel hole system parallelism diagram of the embodiment of the application.

[0044] Figure 4 It is a parallelism deviation diagram of the embodiment of the application.

[0045] Figure 5 It is a deep hole cylindricity diagram of the embodiment of the application.

[0046] Figure 6 It is a cylindricity detection section center deviation diagram of the embodiment of the application.

[0047] Figure 7 It is an axial hole system calibration reference diagram of the embodiment of the application.

[0048] Figure 8 It is a parallel hole system calibration reference diagram of the embodiment of the application.

[0049] Figure 9This is a schematic diagram of the deep hole calibration reference according to an embodiment of the present invention. Detailed Implementation

[0050] The following detailed description illustrates the specific implementation method:

[0051] The implementation examples are basically as follows Figures 1-9 As shown: A method for machining deep holes on a large boring and milling machine, comprising the following steps:

[0052] S1. Perform rough machining or semi-finishing of the hole system on the workpiece according to product requirements.

[0053] S2. Before transferring the workpiece from the roughing equipment to the finishing equipment, use the transfer interval to fix the workpiece onto the coordinate measuring machine (CMM). Based on the geometric tolerance type, evaluate the coordinates and error vectors of the workpiece using the CMM. The CMM operates in a constant temperature and humidity environment.

[0054] S2.1, Coaxiality Detection: Combined with Figure 1 Taking the axial hole system shown 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 using a coordinate measuring machine, and hole A is selected as the reference hole. Then, the fitting center of each hole is projected onto the XY plane, as shown below. Figure 2 As shown, the fitted circle center 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 holes B and C are the coaxiality deviations of holes B and C relative to hole A.

[0055] S2.2 Parallelism Detection: Combined with Figure 3 Taking the parallel hole system shown as an example, which includes holes A, B, and 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 using a coordinate measuring machine. Hole A is selected as the reference hole, and the fitting axis of hole A coincides with the Y-axis of the coordinate system. Then, as shown... Figure 4 As shown, the fitted axes of each hole in the hole system are translated to the same coordinate system, with the starting points coinciding with the origin, to obtain the coordinates A1(Y) of each hole axis in the YZ plane. a ,0),B1(Y b Z b ) and C1(Y c Z c Then, project each fitted axis onto the XZ plane. The projection coordinates of the fitted axis of each hole onto the XZ plane are A2(0,0), B2(X... b Z b C2(X) c Zc ), which is the deviation value of parallelism in the main plane.

[0056] S2.3, cylindricality detection: combined with Figure 5 Taking the deep hole shown in FIG. 2 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, which are positions 1-4 respectively, the detection intervals L between adjacent two detection sections are equal, the fitting center of each detection section is calculated by the three-coordinate measuring instrument, and the axis of the hole, i.e. the Z-axis, is further fitted by the fitting centers, and each fitting center is projected into the X-Y plane, as shown in FIG. 3. Figure 6 The coordinates of the fitting centers 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 size deviation Δ φDn of the detection section, φD1, φD 2、 φD 3、 φD4 respectively correspond to the diameters of the detection sections at positions 1-4, and the center deviation and the diameter size deviation are equivalent to the cylindricality deviation. Preferably, the detection interval is 200-300 mm; when the single-hole deep hole is 300-500 mm deep, the detection interval is 200 mm; when the single-hole deep hole is about 1 m deep, the detection interval is 300 mm; and when selecting the detection position, the hole opening position is preferred, and then the middle position of the hole is selected.

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

[0058] S3, fix the workpiece to the finishing machining equipment, i.e. a large numerical control boring and milling machine, and perform alignment, then position the finishing hole reference, which is consistent with the coordinate evaluation reference in step S2; use the machining equipment to establish the machine tool coordinate system according to the form and position tolerance type, and obtain the coordinates (X' n , Y' n , Z' n ), then recheck the finishing hole by the dial gauge or the micrometer, take the coordinate system obtained by the three-coordinate measuring instrument in step S2 as the reference, combine the detection deviations, and further compare and judge the two coordinate systems to obtain the coordinate system deviation, including: X-axis direction deviation εn x = X n -X′ n , Y-axis direction deviation εn y = Y n -Y′ n , and Z-axis direction deviation εn z = Z n -Z′n .

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

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

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

[0062] S4, according to the form and position tolerance type, compensate the coordinate system deviation obtained in step S3 to the processing equipment, and after the compensation is completed, design corresponding calibration reference holes φd n at each hole of the hole system, as shown in Figure 7 , Figure 8 , Figure 9 , the calibration reference hole coincides with the axis of the hole, the hole diameter of the calibration reference hole is smaller than the designed hole diameter of the hole system, and the processing equipment continuously completes the processing of the calibration reference hole in the precision stable state, ensuring that the calibration reference hole completely meets the processing precision requirements; for parallel hole systems, calibration reference holes are arranged at both ends of the hole system, and when the hole system includes stepped holes, calibration reference holes are arranged according to different hole diameters.

[0063] The difference between the calibration reference hole and the designed aperture of the hole system is a radial process calibration reference allowance, the radial process calibration reference allowance is 0.02-0.05mm, the allowance is within the last finishing allowance range of the machining equipment, and the machining allowance of one pass can avoid the knife mark caused by the knife connection, so as to make the inner hole surface complete; secondly, the radial process calibration reference allowance is too large, which will make the machining period long after the last calibration reference, and the long machining period will lead to the precision error of the machining equipment affected by the environmental factors and unable to be corrected in time, thereby affecting the final precision of the workpiece.

[0064] The coordinate system obtained by the three-coordinate measuring instrument is used as a reference to judge and compensate the precision error of the machining equipment, so that the machining equipment completes the initial precision calibration, and the calibration reference hole is machined with the precision, so that the calibration reference hole basically reproduces the measurement result of the three-coordinate measuring instrument, and the calibration reference hole can be used as a detection reference in the subsequent finishing process, so that online monitoring and real-time compensation can be realized without taking the workpiece off the machine tool.

[0065] S5, start finishing, and set the calibration frequency, periodically detect the calibration reference hole during the finishing process and compare it with the initial coordinates of the calibration reference hole, obtain the precision deviation, and compensate the coordinate system of the machining equipment according to the deviation, until the finishing is completed; when the radial machining allowance of the workpiece is consistent with the radial process calibration reference allowance, the last calibration is performed, and then continuous machining is performed to the finished product.

[0066] The calibration frequency is based on the environmental temperature change, and the environmental temperature change is 2-5℃; specifically, according to the precision requirements of different machining equipment, the calibration frequency is different during actual machining, for example: if the precision of the machining equipment is 0.02mm, the calibration frequency is set based on the environmental temperature change of 2-3℃, and if the precision of the machining equipment is 0.05mm, the calibration frequency is set based on the environmental temperature change of 5℃.

[0067] In steps S3, S4 and S5, the finishing hole system of the workpiece is checked by a dial gauge or a micrometer, the dial gauge or the micrometer is installed on the main shaft of the machining equipment, the measuring head is in contact with the hole surface, and the dial gauge or the micrometer reading is not greater than 0.01mm, so as to ensure the machining precision and product precision.

[0068] Specific working principle: in actual application, the coordinate of the workpiece after rough machining is evaluated by the three-coordinate measuring instrument in the transfer link before finishing, the error existing in the workpiece after rough machining is measured, then the workpiece is fixed on the machining equipment and the error generated by the structure of the machine tool is measured again, then the two errors are compared and judged based on the measurement result of the three-coordinate measuring instrument, and the coordinate system deviation is obtained, the machining equipment is compensated according to the coordinate system deviation, and most of the precision error of the workpiece is compensated.

[0069] Then, the calibration reference hole is machined before formal finishing by the compensated machining equipment, since the calibration reference hole is machined when the machining equipment is stable and has high precision, it basically meets the machining requirements of the workpiece and basically reproduces the measurement coordinates of the three-coordinate measuring instrument; moreover, the workpiece is always fixed on the machining equipment in the subsequent finishing process, and only the error of the machining equipment itself exists in the subsequent machining process, therefore, the coordinate position of the calibration reference hole is detected online to effectively judge the error direction and value at this time, and the machining equipment is compensated in real time to ensure the machining precision.

[0070] The machining method of the scheme decomposes the coaxiality, parallelism and cylindricity error of the hole or hole system into coordinate values and sizes directly available for the numerical control boring and milling machine, and the calibration reference is established to perform online monitoring and compensation, especially for the machining of deep and long holes (system) and the machining with precision close to or exceeding the conventional precision of the machine tool, the method can ensure the precision of the machined hole in real time, effectively reduces the number of process detections in the product machining process, and is also applicable to the machining environment under non-constant temperature conditions, and conforms to the actual production.

[0071] The above is only an embodiment of the present application, and the specific technical solutions and / or common knowledge of characteristics in the scheme are not described in detail. It should be noted that for those skilled in the art, without departing from the technical solutions of the present application, a number of modifications and improvements can be made, which should also be considered as the protection scope of the present application, and these will not affect the effect and practicality of the present application. The protection scope of the present application should be subject to the content of its claims, and the specific implementation mode and the like in the specification can be used to explain the content of the claims.

Claims

1. A method for machining deep holes on a large boring and milling machine, characterized in that: Includes the following steps: S1. Perform rough machining on the hole system of the workpiece according to product requirements; S2. Before the workpiece is transferred from the roughing equipment to the finishing equipment, the coordinates and error vectors of the workpiece are evaluated according to the type of geometric tolerances: S2.1 Coaxiality Inspection: First, calculate the fitting center of each hole in the hole system, select a reference hole, and then project the fitting center of each hole onto a plane perpendicular to the hole system. The fitting center of the reference hole is the origin of the coordinate system, and the coordinates of the fitting center of each hole are (X... n Y n Z n ); S2.2 Parallelism Detection: First, calculate the fitted axis of each hole in the hole system, select a reference hole, and then translate the fitted axes of each hole in the hole system to the same coordinate system, with the starting points coinciding. Next, project each fitted axis onto a plane perpendicular to the hole system. The coordinates of the fitted axis of each hole are (X... n Y n Z n ); S2.3 Cylindricity Inspection: Multiple inspection sections are taken along the axial direction inside the hole, with equal inspection intervals between adjacent sections. The fitted center of each inspection section is calculated, and these fitted centers are further fitted to the axis of the hole. The fitted centers are projected onto a plane perpendicular to the axis. The coordinates of the fitted center of each inspection section are (X... n Y n Z n ); S3. Fix the workpiece onto the precision machining equipment for alignment, then locate the precision machining hole datum. Based on the geometric tolerance type, establish the machine tool coordinate system through the machining equipment to obtain the hole coordinates (X'). n Y' n Z' n This leads to 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. Based on the type of geometric tolerance, compensate the coordinate system deviation obtained in step S3 for the processing equipment. After the compensation is completed, design corresponding calibration reference holes at each hole in the hole system. The calibration reference holes coincide with the axis of the holes, and the diameter of the calibration reference holes is smaller than the designed diameter of the hole system. S5. Begin finishing and establish a calibration frequency. During the finishing process, periodically inspect the calibration reference hole and compare it with the initial coordinates of the calibration reference hole to obtain the accuracy deviation. Based on the deviation, perform coordinate system compensation on the machining equipment until finishing is completed.

2. The method for machining deep holes on a large boring and milling machine according to claim 1, characterized in that: In step S2, the equipment used to evaluate the coordinates of the workpiece is a coordinate measuring machine, and the working environment of the coordinate measuring machine is a constant temperature and humidity environment.

3. The method for machining deep holes on 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, which is 0.02-0.05 mm.

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

5. A method for machining deep holes on a large boring and milling machine according to claim 1, characterized in that: In steps S3, S4 and S5, the precision-machined hole system of the workpiece is checked using a dial indicator or a micrometer, and the dial indicator reading is no greater than 0.01 mm.

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

7. A method for machining deep holes on 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 holes.

8. A method for machining deep holes on 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 datum allowance, a final calibration is performed, and then continuous machining is carried out until the finished product is finished.

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

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

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