A highly efficient processing method for array holes on the outer surface of a thin-walled shell

Abstract

The present invention discloses a method for efficiently processing array holes on the outer surface of a thin-walled shell, and belongs to the field of processing technology. The method obtains the actual position information of the array mounting seat based on the line laser measurement method, solves the final processing position of adjacent symmetrical mounting seat holes, and realizes efficient automatic processing of depth-controllable threaded holes, solving the problems of difficult positioning, low efficiency, and insufficient precision in array mounting seat hole processing. The method described in the present invention is suitable for the situation where the position is automatically adjusted by programming in the adaptive processing system of the array holes on the outer surface of thin-walled shell parts. The adjustment process is simple, taking into account the coupling influence between the array holes and the safety processing requirements, and the results are reliable. The method can meet the requirements of adaptive processing of mounting seat hole features for manufacturing site environments.

Description

Technical Field

[0001] The invention belongs to the field of processing technology and relates to a method for efficiently processing array holes on the outer surface of a thin-wall shell. Background Art

[0002] Mounting holes are common features on key thin-walled structural parts in the aerospace field, and their processing quality seriously affects the overall performance and safe service life of core components. Due to the characteristics of thin walls and low rigidity, thin-walled shells are easily affected by factors such as initial residual stress, cutting force, and clamping conditions during processing, which can easily produce unpredictable posture deformation, causing the array features to deviate from the theoretical position. Making holes according to the theoretical processing position seriously affects the dimensional accuracy and performance of the array holes. During processing, the array holes need to meet the position size requirements during processing, and the holes should be as close as possible to the center of the mounting seat, that is, the wall thickness requirements, and the relative position requirements of the adjacent mounting seat holes. When making holes manually, workers use marking to perform radial positioning, use the previous hole as the positioning reference for the next hole, and use a vernier caliper for axial positioning. This will cause error accumulation, resulting in increasing processing errors in the holes in the second half of the workpiece. Manual marking and punching are very inefficient, the accuracy is difficult to guarantee, and it is difficult to take into account multiple constraints. Therefore, by obtaining the posture change data of the hole matrix to be processed during the machining process through in-machine measurement, comprehensively considering the hole position constraints, wall thickness constraints and the relative position constraints of adjacent feature holes, the machining position of the hole is adjusted and compensated, and the optimal machining position of the hole is solved. Adaptive and controllable machining of the hole is realized, which is crucial to improving the machining accuracy of large thin-walled parts, and further improving the safe service performance and life of core aerospace components.

[0003] In 2020, Zhu Simeng et al. disclosed an adaptive compensation processing method for film cooling holes of turbine blades in patent CN202010656092.4, which improved the processing accuracy and automation of the holes. However, this method only uses the coordinate system offset transformation after point cloud registration to solve the processing position of the holes, which is inefficient and does not consider the relative position requirements between the holes. It is not suitable for the processing of array holes. In 2018, Kang Renke et al. disclosed a method for making holes in laminated components with adaptive adjustment of processing parameters in patent CN201811126903.9. In this method, sensors are used to monitor the rotation speed and speed changes of the tool drive device after stabilization, and the type of material to be processed and the processing progress are judged, so as to adaptively change the hole making parameters, reduce manual intervention during hole making, and improve processing efficiency. However, this method does not consider the adaptive correction processing after the base position of the hole to be processed changes, and cannot make specific processing position corrections for the changed hole features.

[0004] The above studies have not yet mentioned an efficient method for processing array holes on the outer surface of a thin-walled shell. Summary of the invention

[0005] In order to overcome the shortcomings of the existing methods, the present invention aims at the problem that manual positioning and processing of array mounting holes on the outer surface of thin-walled parts is difficult and inefficient, and proposes an efficient processing method for array holes on the outer surface of thin-walled shells. In the method, a line laser measurement method is used to obtain the actual posture information of the mounting seat, and the axial positioning reference and radial positioning reference of the mounting seat are determined; the deviation between the actual position and the theoretical position of the mounting seat is compared, the qualified range of wall thickness and the qualified range of position of the mounting seat hole are determined, and the intersection is taken to solve the qualified processing range that meets both the wall thickness requirements and the position requirements, and the midpoint of the simplified line of the qualified processing range is taken as the preliminary processing position of the mounting seat hole; considering the relative position requirements of adjacent mounting seat holes in the same group, the preliminary processing position of the mounting seat hole is adjusted within the qualified processing range, and the final processing position of the mounting seat hole is solved; in engineering practice, it is assumed that the final processing position of the mounting seat hole satisfies all spatial position constraints, the final processing position coordinates are output, and an adaptive processing program is generated; a laser automatic tool setting instrument is used to realize automatic tool setting during the processing process, and a machine tool spindle cutting force monitoring method is used to realize the monitoring of the processing state, while efficiently making holes, avoiding damage to the workpiece substrate, and completing the adaptive and efficient processing of the mounting seat hole.

[0006] The technical solution adopted by the present invention is:

[0007] An efficient processing method for array holes on the outer surface of a thin-walled shell comprises the following steps: firstly, a line laser measurement method is used to scan the workpiece, and based on the measurement data, boundary point extraction and contour fitting are performed to obtain the actual position information of the thin-walled shell and the mounting seat, and the axial positioning reference and radial positioning reference of the mounting seat are determined; the deviation between the actual position and the theoretical position of the mounting seat is compared, and the qualified wall thickness range and the qualified position range of the mounting seat hole are determined, and it is judged whether the two have an intersection. The intersection of the two is the qualified processing range that meets both the position requirement and the wall thickness requirement, and the judgment result is divided into two cases; for the case where the intersection exists, the midpoint of the simplified line of the qualified processing range is taken as the preliminary processing position of the mounting seat hole; considering the adjacent symmetrical mounting positions, the qualified wall thickness range and the qualified position range are determined. The relative position requirements of the mounting hole are used to determine whether it can be further adjusted. The judgment results are divided into three situations. For situations that can be further adjusted, the initial processing position of the mounting hole is adjusted within the qualified processing range, and the center point of the intersection of the relative position tolerance zone and the simplified line of the qualified processing range is taken as the final processing position of the mounting hole. In engineering practice, it is considered that the optimal processing position of the hole meets all spatial position constraints, and the optimal processing position coordinates are output, and the processing G code is generated. The machine tool spindle cutting force monitoring method is used to realize the monitoring of the processing status to avoid damage to the thin-walled shell, and the laser automatic tool setting instrument is used to realize fast and accurate tool change, thereby realizing adaptive and efficient processing of the mounting hole.

[0008] The specific steps are as follows:

[0009] The first step is to quickly extract array feature information based on line laser on-machine measurement

[0010] The rapid and accurate extraction of the actual position information of array features is a prerequisite for high-quality and efficient processing of parts. This step uses the line laser on-machine measurement method to quickly and accurately extract the surface contour information of the parts, which can lay the foundation for the next step of array hole processing position solution.

[0011] The part consists of a thin-walled shell and an array of mounting seats on the outer surface of the thin-walled shell. There are two rows of mounting seats axially distributed on the outer surface of the thin-walled shell. Two radially adjacent mounting seats form a group, and each mounting seat needs to be processed with a threaded hole. When making holes in the mounting seats, the holes need to meet the axial and radial dimension requirements relative to the thin-walled rotating shell, the holes of two adjacent mounting seats in the same group need to meet the relative position requirements, and the holes on the mounting seats need to meet the axial and radial dimension requirements relative to the mounting seats, that is, the wall thickness requirements. At the same time, due to the gap between the mounting seat and the thin-walled shell, during processing, after the tool penetrates the mounting seat, it cannot damage the thin-walled shell.

[0012] Considering that the mounting seat is very small relative to the thin-walled shell, it is difficult to use the contact on-machine measurement method, so the non-contact line laser on-machine measurement method is used to measure the part. First, the thin-walled shell 4 is clamped on the processing machine tool 1, a special tool handle type line laser measurement tool is developed, and the line laser scanner is installed on the processing machine tool, which is driven by the processing machine tool to complete the workpiece measurement. The tool handle type line laser measurement tool includes a special tool handle 6, an upper connecting plate 7, a lower connecting plate 9, a three-dimensional precision fine-tuning platform 8 and a line laser scanner 10; wherein, the special tool handle 6 is installed on the main shaft of the processing machine tool, and it is connected to the three-dimensional precision fine-tuning platform 8 through the upper connecting plate 7; the three-dimensional precision fine-tuning platform 8 is connected to the line laser scanner 10 through the lower connecting plate 9, which is used to calibrate the measurement posture of the line laser scanner 10. The non-contact line laser on-machine measurement method is used to obtain the measurement point cloud data of the surface contour of the thin-walled shell part. After the measurement point data is pre-processed such as noise removal, data simplification and repair, it needs to be further feature boundary extraction and gap solution.

[0013] As an important geometric feature of point cloud data, curvature can reflect the change of curves to a certain extent, so curvature is used as the measurement parameter of edge feature points. The three-point method is used to calculate the approximate curvature of each position data point of the thin-walled shell surface profile measurement point cloud data, and the point with the largest curvature is calculated, which is the edge feature point of the mounting seat to be measured. After obtaining the edge feature points of the mounting seat, the quadratic B-spline curve is used to interpolate and fit the edge feature points of the mounting seat to obtain the fitting curve. The fitting curve consists of semicircular arc A, straight line L1, semicircular arc B and straight line L2. The four lines are connected end to end in sequence, and the semicircular arc A and straight line L1 intersect at endpoint a1 (x a1 ,y a1 ), intersecting the straight line L2 at the endpoint a3(x a3,y a3 ), the semicircular arc B intersects the straight line L1 at the endpoint a2(x a2 ,y a2 ), intersecting the straight line L2 at the endpoint a4(x a4 ,y a4 ). The fitting curve is the positioning reference of the mounting seat hole relative to the mounting seat.

[0014] Solve for the perpendicular bisector of line L1:

[0015]

[0016] Similarly, the perpendicular bisector of line L3 can be solved, and the intersection of the two perpendicular bisectors can be obtained jointly, that is, the center point O2 of the mounting base; repeat the above steps to obtain another intersection point O1 of the perpendicular bisector of line L2 and the perpendicular bisector of line L4, and the midpoint of the line connecting points O1 and O2 is the actual center point 2a of the mounting base.

[0017] Since the thin-walled shell cannot be damaged during the hole processing, it is necessary to accurately calculate the actual height and actual gap value of the mounting seat to provide a basis for the cutting feed rate of the machine tool. The deformation of the thin-walled shell is uneven, and it is necessary to perform differential fitting on the gap between the mounting seat and the thin-walled shell. For the gap area, the deformation is small. After quadratic interpolation fitting, the actual deformation situation can be approximately solved, and the degree of approximation is high, which is accurate enough to judge the actual change state of the mounting seat gap. Take a radial section of the mounting seat as an example. After quadratic interpolation fitting, the fitted gap can represent the actual gap. After fitting, the actual height D of the mounting seat at different positions j It can be approximated using a quadratic curve:

[0018] D j =k1·x 2 +k2·x+b(2)

[0019] Where, the horizontal coordinate x is the horizontal coordinate value of the cross section; D j is the actual height value at the mounting seat position j; k1, k2, b are fitting constants.

[0020] The actual gap can be expressed as:

[0021] η=D j -d=k1·x 2 +k2·x+bd(3)

[0022] Where η is the actual gap value; d is the actual thickness of the mounting base.

[0023] The curvature calculation and quadratic B-spline curve fitting method can be used to obtain the boundary expression of the end face of the thin-walled shell. The vertex is taken as the axial positioning reference of the array mounting seat hole relative to the thin-walled shell. The position data points on the line connecting the actual center points of the same group of radially adjacent mounting seats are taken, and the quadratic B-spline curve is used for fitting to obtain the expression. The vertex is taken as the radial positioning reference of the same group of radially adjacent mounting seat holes relative to the thin-walled shell.

[0024] The second step is to calculate the hole position of the thin-walled shell surface mounting seat based on the measured point cloud

[0025] This step is based on the surface posture information and positioning reference of the thin-walled shell obtained in the first step, comprehensively considers the multiple constraints of the array holes, and solves the processing position coordinates of the array holes.

[0026] When making holes for the array mount, multiple constraints need to be considered in coordination: L Z ±D WZ and L d ±D Wd Constrain the position of the hole on the thin-walled substrate to ensure the position requirements; L bd ±D bd and L bz ±D bz The position of the constraint hole on the mounting base ensures the wall thickness requirement; L dL ±D WdL Constrains the relative position requirements between radially adjacent mounting seat holes in the same group.

[0027] The actual end face center 2a of the mounting base does not coincide with the theoretical end face center 1a of the mounting base. There is an axial deviation d between the two. z and radial deviation d d All points that meet the wall thickness processing requirements are a rectangular area, that is, the wall thickness tolerance range Q b , the center of which is the actual end face center 2a of the mounting base. All points that meet the position requirements are also a rectangular area, that is, the position tolerance range Q w , the center of which is the theoretical end face center 1a of the mounting base. Wall thickness tolerance range Q b and position tolerance range Q w The intersection of is the qualified processing range Q of a single hole h That is, when machining holes within this range, both the wall thickness requirements and the position requirements can be met. According to the axial deviation d of the center point of the wall thickness tolerance range and the center point of the position tolerance range z and radial deviation d d , axial wall thickness tolerance value D bz And radial wall thickness tolerance D bd , axial position tolerance value D wz And radial position tolerance value D wdAccording to the relationship between the qualified processing range and the processing conditions, the qualified processing range can be divided into two situations:

[0028] When z <D wz +D bz And d d <D wd +D bd When the hole is within the qualified processing range, it can coordinate and compensate the processing position of the hole based on the relative position requirements of the adjacent mounting seat holes while meeting the wall thickness requirements and position requirements. In order to facilitate processing, the qualified processing range is simplified, and the line L connecting the center point 2a of the wall thickness tolerance range and the center point 1a of the position tolerance range is taken, and the intersection of the straight line L and the qualified processing range is taken as the adjustable range L. T , take the midpoint O of the adjustable range as the initial processing position of the hole.

[0029] When z ≥D wz +D bz or d ≥D wd +D bd When the qualified processing range of the hole does not exist, the wall thickness requirements and position requirements cannot be met at the same time, and the part is scrapped.

[0030] Considering the relative position requirements between radially adjacent mounting seat holes, it is necessary to further coordinate and adjust the initial processing positions of radially adjacent mounting seat holes. Lmin and the maximum radial distance d Lmax , Radial distance d between the initial processing positions of radially adjacent mounting seat holes Lmid , Relative position requirements of radially adjacent mounting holes L dL ±D WdL The relationship between them can be further divided into three cases:

[0031] When the radial distance between the initial processing positions of the radially adjacent mounting seat holes meets L dL ±D WdL The initial processing position of the radially adjacent mounting seat holes is the final processing position of the holes.

[0032] When the radial distance between the initial processing positions of the radially adjacent mounting seat holes does not meet L dL ±D WdL Requirements, Lmax ≥L dL +D wdL or Lmin ≤L dL -D wdLWhen the adjustment is completed, all points within the adjustment range do not meet the relative position requirements of the radially adjacent mounting seat holes, and coordination compensation cannot be achieved, so the parts are scrapped.

[0033] When the radial distance between the initial processing positions of the radially adjacent mounting seat holes does not meet L dL ±D WdL Requirements, d Lmax ∈L dL ±D wdL or Lmin ∈L dL ±D wdL When the adjustment range is adjusted, some points in the adjustment range meet the radial relative position requirements. On this basis, the initial processing position of the radially adjacent mounting seat holes is adjusted. Take the intersection L of the adjustable range of the radially adjacent mounting seat holes and the relative position tolerance band TZ , the points in the intersection can meet the wall thickness requirements, position requirements and relative position requirements. At this time, the midpoint O of the intersection is taken Z , as the final machining position of the radially adjacent mounting seat holes.

[0034] Finally, the final processing position coordinates of the array mounting seat holes are output, and the processing G code is generated to prepare for processing.

[0035] Step 3: Efficient and automatic processing of threaded holes with controllable depth

[0036] This step completes high-quality and efficient processing of the array mounting seat holes based on the array mounting seat hole processing position coordinates solved in the previous step while ensuring that the shell is not damaged.

[0037] First, in order to ensure the processing quality of the array mounting seat hole, it is necessary to perform drilling and threading processing in two processes. After changing the tool between different processes, the tool has size deviation and position runout deviation. Only after tool setting, the radius, length and position deviation of the tool are compensated into the adaptive processing program, and the tool can be accurately processed at the position after adjustment and compensation, while avoiding damage to the shell. This method uses a laser automatic tool setting instrument for tool setting. When setting the tool, first use a standard tool to set the tool to obtain the actual position of the laser tool setting instrument in the machine tool coordinate system; then, the actual tool used is approached to the laser beam from multiple directions to accurately determine the tool geometry and the position deviation of the tool relative to the spindle after installation. After the actual length H of the tool is obtained by tool setting, the tool length compensation instruction G43 can be updated to perform the height offset of the processing position; for the deviation of the tool in the X and Y directions, the coordinate system offset instructions such as TRANS or R parameters can be used to perform cumulative compensation for the position offset, thereby further generating array mounting seat hole processing programs for different tools (different processes) based on the adaptive processing code.

[0038] Secondly, considering the gap of the mounting seat, the solid rocket shell cannot be damaged during processing. At the same time, two measures are taken to ensure the safe processing of the mounting seat hole. The actual mounting seat height and gap value are solved by line laser measurement data to control the G code drilling depth of the mounting seat processing to avoid damaging the shell. At the same time, when the tool cuts in and out of the workpiece, the cutting force will produce periodic mutations. The machine tool spindle cutting force monitoring function is used to capture the axial cutting force mutation point at the moment the tool penetrates the mounting seat. When the tool continues to feed after the penetration is completed, the system alarms and controls the machine tool to stop, realizing the safe monitoring of the processing status during the processing, avoiding abnormal situations, and ensuring safe processing.

[0039] Finally, start the machine tool, and execute the array mounting seat hole processing program while monitoring the force on the machine tool spindle to complete high-quality and efficient processing of the array holes of the thin-walled shell mounting seat.

[0040] Beneficial effects of the present invention: The present invention proposes an efficient processing method for array holes on the outer surface of a thin-walled shell. The method obtains the actual position information of the array mounting seat based on the line laser measurement method, solves the final processing position of adjacent symmetrical mounting seat holes, and realizes efficient automatic processing of depth-controllable threaded holes, solving the problems of difficult positioning, low efficiency, and insufficient precision in array mounting seat hole processing. The method described in the present invention is suitable for programming and automatic position adjustment in the adaptive processing system of array holes on the outer surface of thin-walled shell parts. The adjustment process is simple, taking into account the coupling effect between the array holes and the safety processing requirements, and the results are reliable. This method can meet the requirements for adaptive processing of mounting seat hole features for manufacturing site environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 (a) is a schematic diagram of the hardware equipment composition of the present invention.

[0042] Figure 1 (b) is a schematic diagram of the tool-handle type linear laser measurement tooling of the present invention.

[0043] Figure 2 It is a schematic diagram of the array hole feature processing requirements described in the present invention.

[0044] Figure 3 The present invention provides a flowchart of the method for adaptively processing holes in a multi-source constrained array.

[0045] Figure 4 This is a schematic diagram of fitting the actual pose information of the mount.

[0046] Figure 5 Schematic diagram for solving the preliminary processing position of the hole.

[0047] Figure 6 This is a schematic diagram of a situation where there is no solution due to large deviation of the mounting base.

[0048] Figure 7 Schematic diagram of further adjustments to the initial machining position of the hole.

[0049] In the figure: 1 processing machine tool; 2 special tool; 3 mounting seat; 4 thin-walled shell; 5 laser tool setting instrument; 6 special tool handle; 7 upper connecting plate; 8 three-dimensional precision fine-tuning platform; 9 lower connecting plate; 10 line laser scanner; i is the i-th group of mounting seats; Z J L is the axial positioning reference of the workpiece; Z L is the center axis of the workpiece; Z ±D WZ L is the axial position requirement of the mounting seat hole relative to the thin-walled shell; d ±D Wd L is the radial relative position requirement of the mounting seat hole relative to the thin-walled shell; dL ±D WdL L is the relative position requirement between adjacent mounting seat holes; bd ±D bd L is the radial position requirement of the mounting seat hole relative to the mounting seat; bz ±D bz The axial position requirement of the mounting seat hole relative to the mounting seat;

[0050] L S L is the theoretical position boundary of the mounting base; C is the actual position boundary of the mounting base; 1a is the theoretical end face center of the mounting base (the center point of the position tolerance range); 2a is the actual end face center of the mounting base (the center point of the wall thickness tolerance range); d z d is the axial deviation between the theoretical end face center of the mounting base and the actual end face center of the mounting base; d is the radial deviation between the theoretical end face center of the mounting base and the actual end face center of the mounting base; L is the line connecting the theoretical end face center of the mounting base and the actual end face center of the mounting base; L T D is the adjustable range; bz D is the axial position tolerance of the mounting seat hole relative to the mounting seat; bd D is the radial position dimension tolerance of the mounting seat hole relative to the mounting seat; wz D is the axial position tolerance of the mounting seat hole relative to the thin-walled substrate; wd Q is the radial position dimension tolerance of the mounting seat hole relative to the thin-walled substrate; w is the position tolerance range; Q b is the wall thickness tolerance range; Q h is the qualified processing range; O is the initial processing position of the hole; Q L Tolerance zone required for relative position; d Lmin The minimum radial distance within the qualified processing range; d LmaxThe maximum radial distance within the qualified processing range; d Lmid L is the radial distance between the initial processing positions of adjacent mounting seat holes. TZ It is the intersection of the adjustable range of adjacent mounting seat holes and the required tolerance zone of relative position; Z It is the final processing position of the adjacent mounting seat holes. DETAILED DESCRIPTION

[0051] The present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0052] Figure 2 Schematic diagram of the processing requirements of the array hole of the present invention, the specific requirements are as follows:

[0053] A rotary part consists of a thin-walled shell and an array of mounting seats on the outer surface of the thin-walled shell. There are two rows of mounting seats axially distributed on the outer surface of the thin-walled shell, with 10 seats in each row, for a total of 20 mounting seats; two radially adjacent mounting seats form a group, and each mounting seat needs to be processed with a threaded hole. The hole processing needs to meet the axial dimension requirement L from the hole to the axial positioning reference of the thin-walled shell Z ±D WZ , radial dimension requirement L to the center axis of the thin-walled shell d ±D Wd , Dimensional requirements between adjacent mounting holes L dL ±D WdL At the same time, the axial dimension requirement L of the hole on the mounting seat must be met. bz ±D bz and radial dimension requirements L bd ±D bd , ensure wall thickness requirements.

[0054] Figure 3 This is a flow chart of the hole adaptive processing method. The specific steps of the hole position adaptive adjustment method are as follows:

[0055] The first step is to quickly extract array feature information based on line laser on-machine measurement

[0056] Considering that the size of the mounting base is very small relative to the thin-walled shell, it is difficult to use the contact on-machine measurement method, so the non-contact line laser on-machine measurement method is used to measure the part.

[0057] The thin-walled shell 4 is clamped on the processing machine 1, a special tool holder type line laser measurement tool is developed, and the line laser scanner is installed on the processing machine, which is driven by the processing machine to complete the workpiece measurement. The tool holder type line laser measurement tool includes a special tool holder 6, an upper connecting plate 7, a lower connecting plate 9, a three-dimensional precision fine-tuning platform 8 and a line laser scanner 10; wherein the special tool holder 6 is installed on the main shaft of the processing machine, connected to the three-dimensional precision fine-tuning platform 8 through the upper connecting plate 7, and the three-dimensional precision fine-tuning platform 8 is connected to the line laser scanner 10 through the lower connecting plate 9, which is used to calibrate the measurement posture of the line laser scanner 10. The non-contact line laser on-machine measurement method is used to obtain the measurement point cloud data of the surface contour of the thin-walled shell part. After the measurement point data is pre-processed such as noise removal, data simplification and repair, it is necessary to further extract the feature boundary and solve the gap.

[0058] As an important geometric feature of point cloud data, curvature can reflect the change of curves to a certain extent, so curvature is used as the measurement parameter of edge feature points. The three-point method is used to calculate the approximate curvature of each position data point of the thin-walled shell surface profile measurement point cloud data, and the point with the largest curvature is calculated, which is the edge feature point of the mounting seat to be measured. After obtaining the edge feature points of the mounting seat, the quadratic B-spline curve is used to interpolate and fit the edge feature points of the mounting seat to obtain the fitting curve. The fitting curve consists of semicircular arc A, straight line L1, semicircular arc B and straight line L2. The four lines are connected end to end in sequence, and the semicircular arc A and straight line L1 intersect at endpoint a1 (x a1 ,y a1 ), intersecting the straight line L2 at the endpoint a3(x a3 ,y a3 ), the semicircular arc B intersects the straight line L1 at the endpoint a2(x a2 ,y a2 ), intersecting the straight line L2 at the endpoint a4(x a4 ,y a4 ). The fitting curve is the positioning reference of the mounting seat hole relative to the mounting seat.

[0059] Solve for the perpendicular bisector of line L1:

[0060]

[0061] Similarly, the perpendicular bisector of line L3 can be solved, and the intersection of the two perpendicular bisectors can be obtained jointly, that is, the center point O2 of the mounting base; repeat the above steps to obtain another intersection point O1 of the perpendicular bisector of line L2 and the perpendicular bisector of line L4, and the midpoint of the line connecting points O1 and O2 is the actual center point 2a of the mounting base.

[0062] Since the thin-walled shell cannot be damaged during the hole processing, it is necessary to accurately calculate the actual height and actual gap value of the mounting seat to provide a basis for the cutting feed rate of the machine tool. The deformation of the thin-walled shell is uneven, and it is necessary to perform differential fitting on the gap between the mounting seat and the thin-walled shell. For the gap area, the deformation is small. After quadratic interpolation fitting, the actual deformation situation can be approximately solved, and the degree of approximation is high, which is accurate enough to judge the actual change state of the mounting seat gap. Take a radial section of the mounting seat as an example. After quadratic interpolation fitting, the fitted gap can represent the actual gap. After fitting, the actual height D of the mounting seat at different positions j It can be approximated using a quadratic curve:

[0063] D j =k1·x 2 +k2·x+b (2)

[0064] Where, the horizontal coordinate x is the horizontal coordinate value of the cross section; D j is the actual height value at the mounting seat position j; k1, k2, b are fitting constants.

[0065] The actual gap can be expressed as:

[0066] η=D j -d=k1·x 2 +k2·x+bd (3)

[0067] Where η is the actual gap value; d is the actual thickness of the mounting base.

[0068] The curvature calculation and quadratic B-spline curve fitting method can be used to obtain the boundary expression of the end face of the thin-walled shell. The vertex is taken as the axial positioning reference of the array mounting seat hole relative to the thin-walled shell. The position data points on the line connecting the actual center points of the same group of radially adjacent mounting seats are taken, and the quadratic B-spline curve is used for fitting to obtain the expression. The vertex is taken as the radial positioning reference of the same group of radially adjacent mounting seat holes relative to the thin-walled shell.

[0069] The second step is to calculate the hole position of the thin-walled shell surface mounting seat based on the measured point cloud

[0070] When making holes for the array mount, multiple constraints need to be considered in coordination: L Z ±D WZ and L d ±D Wd Constrain the position of the hole on the thin-walled substrate to ensure the position requirements; L bd ±D bd and L bz ±D bz The position of the constraint hole on the mounting base ensures the wall thickness requirement; L dL ±DWdL Constrains the relative position requirements between radially adjacent mounting seat holes in the same group.

[0071] The actual end face center 2a of the mounting base does not coincide with the theoretical end face center 1a of the mounting base. There is an axial deviation d between the two. z and radial deviation d d All points that meet the wall thickness processing requirements are a rectangular area, that is, the wall thickness tolerance range Q b , the center of which is the actual end face center 2a of the mounting base. All points that meet the position requirements are also a rectangular area, that is, the position tolerance range Q w , the center of which is the theoretical end face center 1a of the mounting base. Wall thickness tolerance range Q b and position tolerance range Q w The intersection of is the qualified processing range Q of a single hole h That is, when machining holes within this range, both the wall thickness requirements and the position requirements can be met. According to the axial deviation d of the center point of the wall thickness tolerance range and the center point of the position tolerance range z and radial deviation d d , axial wall thickness tolerance value D bz And radial wall thickness tolerance D bd , axial position tolerance value D wz And radial position tolerance value D wd According to the relationship between the qualified processing range and the processing conditions, the qualified processing range can be divided into two situations:

[0072] When z <D wz +D bz And d d <D wd +D bd When the hole is within the qualified processing range, it can coordinate and compensate the processing position of the hole based on the relative position requirements of the adjacent mounting seat holes while meeting the wall thickness requirements and position requirements. In order to facilitate processing, the qualified processing range is simplified, and the line L connecting the center point 2a of the wall thickness tolerance range and the center point 1a of the position tolerance range is taken, and the intersection of the straight line L and the qualified processing range is taken as the adjustable range L. T , take the midpoint O of the adjustable range as the initial processing position of the hole.

[0073] When z ≥D wz +D bz or d ≥D wd +D bd When the qualified processing range of the hole does not exist, the wall thickness requirements and position requirements cannot be met at the same time, and the part is scrapped.

[0074] Considering the relative position requirements between radially adjacent mounting seat holes, it is necessary to further coordinate and adjust the initial processing positions of radially adjacent mounting seat holes. Lmin and the maximum radial distance d Lmax , Radial distance d between the initial processing positions of radially adjacent mounting seat holes Lmid , Relative position requirements of radially adjacent mounting seat holes L dL ±D WdL The relationship between them can be further divided into three cases:

[0075] When the radial distance between the initial processing positions of the radially adjacent mounting seat holes meets L dL ±D WdL The initial processing position of the radially adjacent mounting seat holes is the final processing position of the holes.

[0076] When the radial distance between the initial processing positions of the radially adjacent mounting seat holes does not meet L dL ±D WdL Requirements, d Lmax ≥L dL +D wdL or Lmin ≤L dL -D wdL When the adjustment is completed, all points within the adjustment range do not meet the relative position requirements of the radially adjacent mounting seat holes, and coordination compensation cannot be achieved, so the parts are scrapped.

[0077] When the radial distance between the initial processing positions of the radially adjacent mounting seat holes does not meet L dL ±D WdL Requirements, d Lmax ∈L dL ±D wdL or Lmin ∈L dL ±D wdL When the adjustment range is adjusted, some points in the adjustment range meet the radial relative position requirements. On this basis, the initial processing position of the radially adjacent mounting seat holes is adjusted. Take the intersection L of the adjustable range of the radially adjacent mounting seat holes and the relative position tolerance band TZ , the points in the intersection can meet the wall thickness requirements, position requirements and relative position requirements. At this time, the midpoint O of the intersection is taken Z , as the final machining position of the radially adjacent mounting seat holes.

[0078] Finally, the final processing position coordinates of the array mounting seat holes are output, and the processing G code is generated to prepare for processing.

[0079] Step 3: Efficient and automatic processing of threaded holes with controllable depth

[0080] First, in order to ensure the processing quality of the array mounting seat hole, it is necessary to perform drilling-threading processing in two processes. After changing the tool between different processes, the tool has size deviation and position runout deviation. Only after tool setting, the radius, length and position deviation of the tool are compensated into the adaptive processing program, and the tool can be accurately processed at the position after adjustment and compensation, while avoiding damage to the shell. This method uses a laser automatic tool setting instrument 5 for tool setting. When setting the tool, first use a standard tool to set the tool to obtain the actual position of the laser tool setting instrument in the machine tool coordinate system; then, the actual tool used is approached to the laser beam from multiple directions to accurately determine the tool geometry and the position deviation of the tool relative to the spindle after installation. After the actual length H of the tool is obtained by tool setting, the tool length compensation instruction G43 can be updated to perform the height offset of the processing position; for the deviation of the tool in the X and Y directions, the coordinate system offset instruction such as TRANS or the R parameter can be used to perform cumulative compensation for the position offset, thereby further generating array hole processing programs for different tools (different processes) based on the adaptive processing code.

[0081] Secondly, considering the gap of the mounting seat, the solid rocket shell cannot be damaged during processing. At the same time, two measures are taken to ensure the safe processing of the mounting seat hole. The actual mounting seat height and gap value are solved by line laser measurement data to control the G code drilling depth of the mounting seat processing to avoid damaging the shell. At the same time, when the tool cuts in and out of the workpiece, the cutting force will produce periodic mutations. The machine tool spindle cutting force monitoring function is used to capture the axial cutting force mutation point at the moment the tool penetrates the mounting seat. When the tool continues to feed after the penetration is completed, the system alarms and controls the machine tool to stop, realizing the safe monitoring of the processing status during the processing, avoiding abnormal situations, and ensuring safe processing.

[0082] Finally, start the machine tool, and execute the array mounting seat hole processing program while monitoring the force on the machine tool spindle to complete high-quality and efficient processing of the array holes of the thin-walled shell mounting seat.

Claims

1. A method for efficiently processing array holes on the outer surface of a thin-walled shell, characterized in that: The method comprises the following steps: The first step is to quickly extract array feature information based on line laser on-machine measurement The thin-walled shell part is composed of a thin-walled shell and an array of mounting seats on the outer surface of the thin-walled shell; two rows of mounting seats are axially distributed on the outer surface of the thin-walled shell, and two radially adjacent mounting seats form a group, and each mounting seat needs to be processed with a threaded hole; The non-contact line laser on-machine measurement method is used to obtain the measured point cloud data of the surface contour of the thin-walled shell parts. After the noise removal, data simplification and repair preprocessing of the measured point data, further feature boundary extraction and gap solution are performed on it. The three-point method is used to calculate the approximate curvature of each position data point of the thin-walled shell surface profile measurement point cloud data, and the point with the largest curvature is calculated, which is the edge feature point of the mounting seat to be measured; after obtaining the edge feature point of the mounting seat, the quadratic B-spline curve is used to interpolate and fit the edge feature point of the mounting seat to obtain a fitting curve; the fitting curve is composed of a semicircular arc A, a straight line L1, a semicircular arc B and a straight line L2, and the four lines are connected end to end in sequence, wherein the semicircular arc A and the straight line L1 intersect at the endpoint a1 (x a1 ,y a1 ), intersecting the straight line L2 at the endpoint a3(x a3 ,y a3 ), the semicircular arc B intersects the straight line L1 at the endpoint a2(x a2 ,y a2 ), intersecting the straight line L2 at the endpoint a4(x a4 ,y a4 ); The fitting curve is the positioning reference of the mounting seat hole relative to the mounting seat; Solve for the perpendicular bisector of line L1: Similarly, solve the perpendicular bisector of line L3, and jointly find the intersection of the two perpendicular bisectors, which is the center point O2 of the mounting base; repeat the above steps to find another intersection point O1 of the perpendicular bisector of line L2 and the perpendicular bisector of line L4, and the midpoint of the line connecting points O1 and O2 is the actual center point 2a of the mounting base; Since the thin-walled shell cannot be damaged during hole processing, it is necessary to accurately calculate the actual height and actual clearance value of the mounting seat to provide a basis for the cutting feed of the machine tool; taking a radial section of the mounting seat as an example, after secondary interpolation fitting, the fitted clearance represents the actual clearance; after fitting, the actual height D of the mounting seat at different positions j Using a quadratic curve representation: D j =k1·x 2 +k2·x+b(2) Where, the horizontal coordinate x is the horizontal coordinate value of the cross section; D j is the actual height value at the mounting seat position j; k1, k2, b are fitting constants; The actual gap is expressed as: η=D j -d=k1·x 2 +k2·x+b-d(3) Where η is the actual gap value; d is the actual thickness of the mounting base; The curvature calculation and quadratic B-spline curve fitting method is used to obtain the boundary expression of the end face of the thin-walled shell, and the vertex is taken as the axial positioning reference of the array mounting seat hole relative to the thin-walled shell; the position data points on the line connecting the actual center points of the same group of radially adjacent mounting seats are taken, and the quadratic B-spline curve is used for fitting to obtain the expression, and the vertex is taken as the radial positioning reference of the same group of radially adjacent mounting seat holes relative to the thin-walled shell; the second step is to solve the hole making position of the thin-walled shell surface mounting seat based on the measured point cloud When making holes for the array mount, multiple constraints need to be considered in coordination: L Z ±D WZ and L d ±D Wd Constrain the position of the hole on the thin-walled substrate to ensure the position requirements; L bd ±D bd and L bz ±D bz The position of the constraint hole on the mounting base ensures the wall thickness requirement; L dL ±D WdL Constrain the relative position requirements between radially adjacent mounting seat holes in the same group; where L Z ±D WZ L is the axial position requirement of the mounting seat hole relative to the thin-walled shell, d ±D Wd L is the radial relative position requirement of the mounting seat hole relative to the thin-walled shell, bd ±D bd L is the radial position requirement of the mounting seat hole relative to the mounting seat. bz ±D bz The axial position requirement of the mounting seat hole relative to the mounting seat; The actual end face center 2a of the mounting base does not coincide with the theoretical end face center 1a of the mounting base. There is an axial deviation d between the two. z and radial deviation d d ; All points that meet the wall thickness processing requirements are a rectangular area, that is, the wall thickness tolerance range Q b , the center of which is the actual end face center 2a of the mounting base; all points that meet the position requirements are also a rectangular area, that is, the position tolerance range Q w , the center of which is the theoretical end face center 1a of the mounting base; the wall thickness tolerance range Q b and position tolerance range Q w The intersection of is the qualified processing range Q of a single hole h That is, when machining holes within this range, the wall thickness requirements and position requirements can be met at the same time; according to the axial deviation d of the center point of the wall thickness tolerance range and the center point of the position tolerance range z and radial deviation d d , axial wall thickness tolerance value D bz And radial wall thickness tolerance D bd , axial position tolerance value D wz And radial position tolerance value D wd The qualified processing range is divided into two situations: When z <D wz +D bz And d d <D wd +D bd When the qualified processing range of the hole exists, it can coordinate and compensate the processing position of the hole based on the relative position requirements of the adjacent mounting seat holes while meeting the wall thickness requirements and position requirements at the same time; in order to facilitate processing, the qualified processing range is simplified, and the line L connecting the center point 2a of the wall thickness tolerance range and the center point 1a of the position tolerance range is taken, and the intersection line of the straight line L and the qualified processing range is taken as the adjustable range L T , take the adjustable range L T The midpoint O of is taken as the initial processing position of the hole; When z ≥D wz +D bz or d ≥D wd +D bd When the qualified processing range of the hole does not exist, the wall thickness requirements and position requirements cannot be met at the same time, and the part is scrapped; Considering the relative position requirements between radially adjacent mounting seat holes, it is necessary to further coordinate and adjust the initial processing positions of radially adjacent mounting seat holes; according to the radial minimum distance d within the qualified processing range Lmin and the maximum radial distance d Lmax , Radial distance d between the initial processing positions of radially adjacent mounting seat holes Lmid , Relative position requirements of radially adjacent mounting seat holes L dL ±D WdL The relationship between them can be further divided into three cases: When the radial distance between the initial processing positions of the radially adjacent mounting seat holes meets L dL ±D WdL When the requirements are met, no adjustment is required; the initial processing position of the radially adjacent mounting seat holes is the final processing position of the holes; When the radial distance between the initial processing positions of the radially adjacent mounting seat holes does not meet L dL ±D WdL Requirements, Lmax ≥L dL +D wdL or Lmin ≤L dL -D wdL When all points within the adjustment range do not meet the relative position requirements of radially adjacent mounting seat holes, coordination and compensation cannot be achieved, and the parts are scrapped; When the radial distance between the initial processing positions of the radially adjacent mounting seat holes does not meet L dL ±D WdL Requirements, Lmax ∈L dL ±D wdL or Lmin ∈L dL ±D wdL When there are some points in the adjustable range that meet the radial relative position requirements, on this basis, the preliminary processing positions of the radially adjacent mounting seat holes are adjusted; the intersection L of the adjustable range of the radially adjacent mounting seat holes and the relative position requirement tolerance zone is taken TZ , the points in the intersection can meet the wall thickness requirements, position requirements and relative position requirements. At this time, the midpoint O of the intersection is taken Z , as the final processing position of radially adjacent mounting seat holes; Finally, the final processing position coordinates of the array mounting seat holes are output, and the processing G code is generated to prepare for processing; Step 3: Efficient and automatic processing of threaded holes with controllable depth First, to ensure the processing quality of the array mounting seat holes, drilling and threading are required in two processes. After changing the tool between different processes, the tool has size deviation and position runout deviation. Only after tool setting and compensating the radius, length and position deviation of the tool into the adaptive processing program, can the tool perform precise processing at the position after adjustment and compensation, while avoiding damage to the shell. Secondly, considering the gap between the mounting seats, the solid rocket shell must not be damaged during processing. The actual mounting seat height and gap value are solved by line laser measurement data to control the G code drilling depth of the mounting seat processing to avoid damaging the shell. At the same time, when the tool cuts in and out of the workpiece, the cutting force will produce periodic mutations. The machine tool spindle cutting force monitoring function is used to capture the axial cutting force mutation point at the moment the tool penetrates the mounting seat. When the tool continues to feed after the penetration is completed, the system alarms and controls the machine tool to stop, realizing safe monitoring of the processing status during the processing, avoiding abnormal situations, and ensuring safe processing. Finally, the machine tool is started, and under the premise of monitoring the force on the machine tool spindle, the array mounting seat hole processing program is executed to complete the processing of the array holes of the thin-walled shell mounting seat.

2. The method for efficiently processing array holes on the outer surface of a thin-walled shell according to claim 1, characterized in that: In the first step, when the non-contact line laser on-machine measurement method is used to measure the part, the thin-walled shell is clamped on the processing machine tool, a tool holder type line laser measurement fixture is designed, and the line laser scanner is installed on the processing machine tool, which is driven by the processing machine tool to complete the workpiece measurement; the tool holder type line laser measurement fixture includes a special tool holder, an upper connecting plate, a lower connecting plate, a three-dimensional precision fine-tuning platform and a line laser scanner; wherein the special tool holder is installed on the main shaft of the processing machine tool, and is connected to the three-dimensional precision fine-tuning platform through the upper connecting plate; the three-dimensional precision fine-tuning platform is connected to the line laser scanner through the lower connecting plate, and is used to calibrate the measurement posture of the line laser scanner.

3. A method for efficiently processing array holes on the outer surface of a thin-walled shell according to claim 1 or 2, characterized in that: In the third step, after the tool is changed between the two processes of drilling and threading, the laser automatic tool setter is used to set the tool; when setting the tool, first use the standard tool to set the tool to obtain the actual position of the laser tool setter in the machine tool coordinate system; then, the tool actually used is approached to the laser beam from multiple directions, so as to accurately determine the tool geometry and the position deviation of the tool relative to the spindle after installation; after the tool is set to obtain the actual length H of the tool, the tool length compensation instruction G43 is updated to perform the height offset of the processing position; for the deviation of the tool in the X and Y directions, the coordinate system offset instruction or the R parameter is used to perform the cumulative compensation for the position offset, so as to further generate the array mounting seat hole processing program of different tools based on the adaptive processing code.

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