CN115157010A - Novel locating machining system and method for multi-variety large thin-walled workpiece - Google Patents
Novel locating machining system and method for multi-variety large thin-walled workpiece Download PDFInfo
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Abstract
The invention relates to a novel position-finding machining system for multi-variety large thin-wall parts, in particular to a method for realizing quick measurement, alignment and position-finding machining of the external machining position of the multi-variety large thin-wall parts by adopting an external preset workstation, a zero-point positioning tool and a five-axis numerical control machine tool, and belongs to the technical field of self-adaptive machining of the large thin-wall parts. The method is characterized in that: the system comprises a server, a cantilever type coordinate measuring machine, a joint arm scanner, a zero positioning tool, an AGV moving platform and a five-axis machine tool; the quick alignment and locating processing of the external processing pose of the multi-variety large thin-wall part can be realized. Compared with the existing processing method of the large thin-wall part, the method provided by the invention can greatly improve the alignment and positioning efficiency and the production efficiency of the large thin-wall part.
Description
Technical Field
The invention relates to a novel position-finding machining system for multi-variety large thin-walled parts, in particular to a method for realizing quick measurement, alignment and position-finding machining of the external machining position of the multi-variety large thin-walled parts by adopting an external preset workstation, a zero point quick-changing tool and a five-axis numerical control machine tool, and belongs to the technical field of large thin-walled part self-adaptive machining.
Background
In order to meet the requirement of aerodynamic profile accuracy, the outer shell of the aerospace craft is mostly formed by combining large thin-walled parts in curved surface shapes, such as cylinders, cones and special-shaped curved surfaces. In order to realize light weight design as much as possible while ensuring structural strength, the large thin-wall part has the characteristic of smooth outer wall curved surface-transverse and longitudinal inner wall rib grids. The large thin-wall part with the characteristics generally adopts a manufacturing route of 'blank casting/forging forming-precise numerical control machining', and because the deformation and shape precise regulation and control difficulty of the blank casting/forging process is large, the formed blank has the problems that the original standard is deviated, the allowance distribution is uneven and the like, and great problems are brought to the processing process of the curved surface of the outer wall and the rib grid of the inner wall of the large thin-wall part. In order to ensure the numerical control machining quality of the large thin-wall part, a technical route of 'measuring, adjusting and machining' is generally adopted, wherein the pose measuring and adjusting are more key process steps, and the result directly determines the machining precision of the internal and external wall characteristics of the subsequent large thin-wall part. However, the conventional posture adjustment process has the following two difficulties: (1) the large-scale thin-wall part is large in size and weight, so that the positioning and alignment process is time-consuming and labor-consuming; (2) special posture adjusting tools for large thin-walled parts need to be designed, and the tools have low flexibility and high cost; in order to solve the above difficulties, a self-locating processing technology is applied. The self-locating machining technology generally means that the actual pose of a workpiece is obtained through measuring equipment inside a machine tool, and the effect of finding the workpiece is achieved by adjusting the pose of a cutter, so that the correct relative position relation between the cutter and the workpiece is guaranteed. Compared with the traditional measurement-posture adjustment process, the implementation process of the self-locating processing technology is obviously more convenient for large thin-wall parts.
The commonly used alignment measuring equipment mainly comprises a digital dial indicator, a coordinate measuring machine and a laser scanner. The measuring and aligning method based on the digital dial indicator is mainly suitable for large thin-wall parts with straight or rotary characteristics such as cylinders/cones, and the method is greatly limited for large special-shaped thin-wall parts without obvious straight or rotary characteristics. The coordinate measuring machine-based positioning and aligning method is mainly used for obtaining the space point coordinates of the workpiece characteristics and is suitable for determining the working condition of the processing pose of the workpiece through a small number of measuring points. For large-sized special-shaped thin-wall parts, a large number of measuring points are often needed to solve the actual pose of the large-sized special-shaped thin-wall parts, and for the working condition, the coordinate measuring machine type positioning and aligning method is often low in efficiency. The positioning and aligning method based on laser scanning is suitable for large thin-walled parts without obvious measurable characteristics, the method fits the actual pose through scanning point cloud data, the pose calculation precision is high, and the method is particularly suitable for the complex machining process of the large thin-walled parts.
The three pose measurement methods are respectively suitable for different types of large thin special-shaped wall parts, wherein the measurement method based on laser scanning not only has higher pose calculation accuracy, but also is suitable for various large thin-wall parts. Therefore, the combination of the laser scanning measurement method and the self-locating processing method is an effective solution for realizing the high-precision and high-efficiency processing of various large thin-walled parts. However, when the method is applied to a large-sized special-shaped thin-walled part, the following problems still need to be solved. (1) The pose measurement process is usually carried out in the machine tool, and the process can occupy a large amount of machine tool using time and reduce the utilization rate of the machine tool. (2) For large thin-wall parts, multiple station transfer measurement is often needed, the process is troublesome and labor-consuming, and the alignment efficiency is severely restricted. An automatic acquisition system for three-dimensional measurement data of a curved surface of a skin curved surface based on laser scanning and a vision sensor is disclosed in the prior patent (CN 2021113756977) of an automatic measurement device and a measurement method for the curved surface of a large skin curved surface of an airplane. A point laser measuring device and method of a four-axis blade laser measuring platform (patent number: CN 2020114934731) discloses a blade measuring system based on a four-axis measuring device and a point laser device. The system applies laser measurement to pose and quality detection of the special-shaped thin-walled workpiece, but the application of the laser measurement in machining is not discussed. A workpiece self-locating device and a processing method for a high-precision polishing machine tool (patent number: CN 2015106615061) disclose a workpiece locating and processing system based on a high-precision measuring head, the method realizes the conversion of measurement data and a processing program, and a processed workpiece only needs to be clamped on the machine tool without table drilling and locating, so that the processing efficiency is greatly improved. However, the method is suitable for machining small workpieces, and for large thin-wall parts, the pose measurement efficiency is low, and the utilization rate of a machine tool is reduced.
Disclosure of Invention
The invention aims to provide a large thin-wall part position-finding machining system and method based on an external preset workstation, a zero point quick-change tool and a five-axis machine tool. And (3) finishing measurement of the actual pose of the large thin-wall part by adopting an off-machine preset workstation, and calculating a conversion relation between the actual pose and a theoretical pose through registration. The zero point quick-change tool is used for realizing the quick change of the large thin-wall part between the external preset workstation and the five-axis numerical control machine tool, and the processing coordinate system of the five-axis numerical control machine tool is corrected based on the pose conversion relation, so that the position finding processing of the large thin-wall part is realized.
The invention comprises the following technical scheme that the large thin-wall part locating machining system based on an external preset workstation, a zero point quick-change tool and a five-axis machine tool comprises a server, a cantilever type coordinate measuring machine, a numerical control rotary table, a measuring end interface, a joint arm type laser scanner, a digital dial indicator, the zero point quick-change tool, a large thin-wall part, an AGV moving platform and the five-axis machine tool.
The server is provided with control software of an off-machine preset workstation and point cloud scanning measurement software of a laser scanner, the control software is used for calculating the conversion relation between the actual pose and the theoretical pose of the workpiece, and accordingly the adjustment amount of a machining coordinate system and the adjustment sequence and the adjustment amount of each movement axis of the five-axis machine tool are obtained.
The external preset workstation comprises a cantilever type coordinate measuring machine (an X axis, a Y axis and a Z axis), a numerical control rotary table (a C axis), a laser scanner and a digital dial indicator. The external preset workstation adopts a set of control system to drive four axes to move. Meanwhile, the cantilever type coordinate measuring machine adopts a magnetic grid ruler, and the rotary table adopts a grating encoder to match with the controller to realize double-feedback accurate motion control in the four-axis motion process, so as to realize accurate positioning.
The articulated arm type laser scanner is fixed to the tail end of a beam of the cantilever type coordinate measuring machine through threaded connection, a threaded interface at the tail end of the beam has quick-change characteristics, and measuring instruments or equipment such as the laser scanner and a digital dial indicator can be installed.
The numerical control rotary table is provided with a quick-change tool, and the quick-change tool comprises a foundation plate, a zero point positioning tool and a clamp plate. The zero point positioning tool comprises a blind rivet and a chuck, and the blind rivet is matched with the chuck to realize accurate positioning. The foundation plate is fixedly connected with the rotary table through bolts and T-shaped blocks, the zero point positioning chuck is fixed on the foundation plate, the zero point positioning blind rivet is fixed on the clamp plate, and the large thin-wall part is fixed on the clamp plate through the clamp. The general zero point positioning blind rivet is matched with the chuck, so that the large thin-walled part is pre-positioned on the rotary table.
And (3) acquiring actual pose point cloud data of the large thin-walled workpiece by using an articulated arm type laser scanner, and further calculating the adjustment sequence and adjustment quantity of the movement axis of the machine tool based on the management and control software in [0007 ]. And then, integrally transporting the workpiece and the clamp plate to a five-axis gantry machine tool through an AGV moving platform, and realizing the quick positioning of the workpiece on the working platform of the machine tool through the matching of a zero positioning rivet on the clamp plate and a zero positioning chuck on the working platform of the five-axis machine tool.
And (3) quickly correcting the zero point of a machining coordinate system in a numerical control system based on the adjustment sequence and the adjustment quantity of the movement axis of the machine tool obtained in the step [0011], so that the cutter can quickly find the actual position of the large thin-walled part, the accuracy of the relative position between the large thin-walled part and the large thin-walled part is ensured, and the machining is started.
A large thin-wall part locating machining method based on an external preset workstation, a zero point quick-change tool and a five-axis numerical control machine tool comprises the following six steps: the method comprises the following steps that a workpiece is pressed on a clamp plate of a numerical control rotary table, a joint arm type laser scanner scans the workpiece, point cloud and a theoretical model are registered, the conversion quantity of a machining coordinate system is calculated, the workpiece is quickly positioned in a machine tool, the machining coordinate system is modified, and machining is started, wherein the method mainly comprises the following steps:
the first step is as follows: the fixture plate is connected and matched with the foundation plate on the numerical control rotary table by using the zero point positioning tool, and the large thin-walled workpiece is fixed on the fixture plate of the numerical control rotary table through fixtures such as a pressure plate, so that the workpiece does not need to be accurately positioned, but the clamping state is ensured to be good, and the vibration in the machining process is reduced as much as possible;
the second step is that: scanning the outer wall, the inner wall rib grid and the clamp plate of the large thin-walled part by using an articulated arm type scanner to obtain point cloud data of the actual pose of the large thin-walled part, and storing the point cloud data;
the third step: introducing a theoretical model and scanning point cloud data into control software, registering an actual clamp plate and a theoretical clamp plate obtained by scanning, registering an actual workpiece and a theoretical workpiece obtained by scanning on the basis, calculating a pose transformation matrix, calculating an adjustment sequence and an adjustment amount of each motion axis of the five-axis machine tool based on the pose transformation matrix, and storing the adjustment sequence and the adjustment amount;
the fourth step: the fixture plate and the workpiece are transported to the five-axis machine tool station through the AGV moving platform, and the fixture plate and the workpiece are quickly positioned on the machine tool working platform by using the zero point positioning tool;
the fifth step: correcting a machining coordinate system in a numerical control system of the machine tool according to the adjustment sequence and adjustment quantity of each movement axis of the machine tool obtained in the step [0016 ];
and a sixth step: starting to process the large thin-walled part by taking the corrected processing coordinate system as a zero point;
the technical scheme of the invention has the following advantages or beneficial effects:
(1) The locating processing system realizes the quick alignment of the large thin-wall part based on the idea of 'measurement outside the machine-adjustment inside the machine'. Compare in traditional built-in alignment, do not occupy the lathe operating time, improved the utilization ratio of lathe greatly, and then improve the production efficiency of whole strip production line. In addition, the machining pose of the large thin-wall part does not need to be actually adjusted, a special pose adjusting tool can be avoided, the whole operation is more convenient, and the cost is lower.
(2) The four-axis measuring equipment disclosed by the invention is matched with the articulated arm type laser scanner to realize the rapid scanning and acquisition of the point cloud data of the full range of the inner wall and the outer wall of the large thin-walled part. The four-axis measuring equipment can realize accurate positioning (the positioning error is within the range of +/-0.03 mm), and the position change relationship before and after the movement of the four-axis measuring equipment can be directly obtained, so that the rapid station transfer of the laser scanner is realized based on the variation of the positions before and after the movement of the four-axis measuring equipment, the measurement reverse process in the traditional station transfer operation process can be avoided, and the station transfer efficiency is higher;
(3) The measuring method of the invention has higher flexibility by matching the four-axis measuring equipment with the articulated arm type laser scanner, can be suitable for various large thin-wall parts such as cylinders, long strips and the like, and has higher equipment flexibility and richer application scenes compared with the measuring method only adopting the articulated arm scanner at present.
Drawings
Fig. 1 is a general structural diagram of a large thin-wall part locating machining system of the invention.
Fig. 2 is a schematic structural view of a four-axis measuring device and a joint arm type laser scanner according to the present invention.
Fig. 3 is a schematic structural view of the zero point positioning tool of the present invention.
FIG. 4 is a flowchart of a locating process method according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clear and more obvious, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the examples described herein are for the purpose of illustration only and are not intended to limit the invention.
As shown in fig. 1, the invention provides a position finding and processing system for a large thin-wall part based on four-axis measuring equipment, a zero point positioning tool and a laser scanner. In this example description, the system configuration includes: the system comprises a server 1, four-axis measuring equipment (a cantilever type coordinate measuring machine 2, a laser scanner mounting interface 3 and a joint arm type laser scanner 4), a numerical control rotary table 5, a zero point positioning tool 6, a foundation plate 7, a clamp plate 8, a large thin-wall part 9, an AGV moving platform 10, a five-axis numerical control machine tool 11 and an operator 12. The server 1 is provided with four-axis measuring equipment management and control software and point cloud scanning and measuring software, the articulated arm type laser scanner 4 is a laser scanner, and the zero point positioning tool 6 comprises an NP190 type non-directional chuck 6-1 and an NP190 type blind rivet 6-2.
The articulated arm type laser scanner 4 is fixed to the tail end of a beam of the cantilever type coordinate measuring machine 2 in a threaded connection mode, the base plate is fixed to the numerical control rotary table 5 through bolts and T-shaped nuts, the non-directional chuck 6-2 of the zero point positioning tool 6 is fixed to the base plate 7 through bolts, the base plate 7 is connected with the clamp plate 8 through the chuck 6-1 and the pull nails 6-2, and the large thin-wall part is fixed to the clamp plate through the pressing plate.
As shown in fig. 2, the four-axis measuring apparatus includes a three-axis cantilever coordinate measuring machine (linear axis, X, Y, Z axis), a numerically controlled turret (revolving axis C axis) and a scanner mounting interface, the X axis stroke is 2000mm, the Y axis stroke is 1600mm, the Z axis stroke is 3100mm, the numerically controlled turret has a diameter of 1600mm and is rotatable 360 °. The positioning precision of the tail end of the cantilever type coordinate measuring machine can reach +/-0.03 mm, and the positioning precision of the rotary table can reach +/-5'.
The articulated arm type laser scanner is connected with a mounting interface at the tail end of the cross beam through threads and is connected to a data acquisition channel of the server 1 in a wired mode, and acquired point cloud data are displayed and stored in point cloud scanning measurement software in the server 1.
The layout mode of the non-directional chuck on the foundation plate is completely the same as that of the non-directional chuck on the working platform of the five-axis numerical control machine tool, so that the repeated positioning precision is less than or equal to +/-5 mu m when the clamp plate is quickly replaced between two devices.
As shown in FIG. 3, the AGV moving platform has a rated load of 3t, and the clamp plate and the workpiece are conveyed back and forth between the four-axis measuring equipment and the five-axis numerical control machine tool.
Point cloud scanning and measuring software in the server 1 is responsible for collecting, displaying and storing scanning point cloud data; the control software is responsible for controlling the four-axis equipment to move according to specified requirements, calculating the conversion relation between the actual pose and the theoretical machining pose of the large thin-wall part and providing the adjustment sequence and the adjustment amount of the machining coordinate system of the five-axis machine tool.
As shown in fig. 4, the invention provides a large thin-walled part position finding processing system based on four-axis measuring equipment, a zero point positioning tool and a laser scanner, which comprises a pose measuring module, a zero point quick-change module, a processing coordinate system adjusting module and a processing module, and specifically comprises the following steps:
the first step is as follows: the clamp plate is in place. Connecting an air source input port on the foundation plate, loosening a locking module on the clamp plate, hoisting the clamp plate onto the foundation plate by using the truss vehicle, and completing the positioning of the clamp plate through the matching of a blind rivet on the clamp plate and a chuck on the foundation plate;
the second step: and (5) positioning a large thin-wall part blank. The workpiece is hoisted to the clamp plate by using the truss vehicle, and the large thin-wall part is prepositioned in a manner of observation by a worker, so that the center line of the large thin-wall part is approximately collinear with the center line of the clamp plate. The large thin-walled part is pressed on the clamp plate through the three pressing plates, the pressing force is determined according to the experience of workers, the workpiece cannot move in the machining process, and the large thin-walled part is prevented from being pressed and deformed;
the third step: and scanning the clamp plate and the blank. The tip of the cantilevered cmm was moved to a position about 200mm directly above the workpiece and the articulated arm scanner was mounted to the end of the beam. A worker holds a joint arm scanner to scan the inner wall and the outer wall of the large thin-walled workpiece blank and the fixture plate, and point cloud data are obtained through measurement software in a server;
the fourth step: and (4) the scanner is used for station transfer measurement. If the size of the workpiece is large and a single scan cannot cover most features of the workpiece and the clamp plate, a transfer station scanning measurement is required. The cantilever type coordinate measuring machine of this patent design has higher terminal positioning accuracy, consequently, after accomplishing scanning for the first time, control coordinate measuring machine end and remove next measuring point, and scanner initial point coordinate directly obtains through management and control software before and after removing, can realize large-scale thin wall spare and change station measurement fast according to initial point coordinate before and after removing.
The fifth step: and (5) processing point cloud data. After the scanning measurement is finished, the obtained point cloud data is processed by using control software, firstly, the point cloud data of the scanning fixture plate and the digital-analog registration of the theoretical fixture plate are realized through an ICP (inductively coupled plasma) algorithm, and an initial reference is determined. On the basis, the point cloud data of the scanned workpiece and the theoretical digital-analog registration are realized through an ICP (inductively coupled plasma) algorithm, and an adjustment matrix T of a machining coordinate system is calculated R . Finally, based on T R Calculating the adjustment sequence and adjustment quantity of each axis of the five-axis machine tool; the specific registration process and algorithm are introduced as follows:
step one, point cloud data acquisition and simplification. Based on a voxel grid downsampling method, firstly, voxel division is carried out on point cloud, then the centroid of a non-empty voxel is calculated to replace all points in the voxel, and downsampling of the point cloud is achieved.
And step two, clamp plate registration. Firstly, dividing the measuring point cloud P into a clamp plate and a workpiece. Framing out a plurality of points on the upper plane of the clamp plate in a worker-assisted manner to obtain a point set P fixture,sample And based thereon, fitting the fixture plate and the workpiece dividing plane S.
Dividing the point cloud into an upper part and a lower part through a fitted plane S, wherein points closer to the plane are all divided to one side of the clamp plate, so that a workpiece measurement point cloud P is obtained workpiece And a fixture plate measurement point cloud P fixture 。
Calculating a fixture plate measurement point cloud P by using a traditional ICP algorithm fixture To a reference point cloud Q fixture If two groups of point clouds can be completely matched, the pose transformation matrix is used for P fixture Every point in the space can be mapped to Q after the pose changes fixture The corresponding point in (1) can be represented as Q fixture ＝R 0 ·P fixture +T 0 Wherein R is 0 A rotation matrix of 3x3, T 0 Is a translation vector of 3x 1.
Solving a rotation matrix R from the measurement point cloud of the clamp plate to the reference point cloud 0 And translation vector T 0 Then, can pass through R 0 And T 0 Operating workpiece measurement point cloud P workpiece Obtaining a workpiece measurement point cloud P 'under the jig plate coordinate system' workpiece The point cloud is the pose of the actual workpiece in the numerical control programming coordinate system, and is the initial state for subsequent pose adjustment.
And step three, registering the large thin-walled parts. Worker interactive point selection workpiece reference point cloud Q workpiece To obtain a reference point cloud Q of the inner wall non-processed surface unmachine 。
First, P is carried out w ′ orkpiece And Q unmachine Coarse registration of (Q) unmachine Is a target pointCloud, P 'using a sample consensus initial registration algorithm SAC-IA' workpiece And Q unmachine Aligned to obtain P ″ workpiece 。
After the coarse registration is finished, the registration algorithm of the inner wall non-processing surface extracted based on key points is used for realizing the scanning point cloud P' of the workpiece workpiece To theoretical model inner wall point cloud Q unmachine Solving the pose offset of the point cloud P ″, scanning the point cloud from the workpiece workpiece Automatically extracting point cloud of inner wall precision casting surface and point cloud Q of theoretical model inner wall unmachine The registration is carried out according to the following specific idea:
calculating a normal vector: computing a point cloud P ″) workpiece And Q unmachine All points in p i 、q i The normal vector of (a);
extraction of Q unmachine The key points are as follows: estimating SIFT key points by using the normal direction as an intensity variable to obtain a key point cloud Q';
extracting non-machined surface point cloud of the inner wall: extracting scanning point cloud P' according to the distance of the closest point workpiece Neutral point cloud Q unmachine Adjacent points to obtain scanning point cloud P of internal non-processing surface unmachine If the distance between two points is greater than a given threshold value, the distance is considered as P ″) workpiece Is not point cloud data of the interior non-machined surface;
extraction of P unmachine The key points are as follows: calculating P unmachine Estimating SIFT key points by using normal vectors to obtain P';
matching key points: searching corresponding points between the point sets P 'and Q';
calculating the curvature of the key point: calculating all key point pairs P in P' and Q i 、q i Gaussian curvature K of pi 、K qi ；
Removing error matching: if K is i ＝|K pi -K qi If | is more than epsilon, deleting key point pair p i 、q i ；
Calculating a rotation and translation matrix: solving a rotation matrix R and a translational vector t between the point sets P 'and Q', Q '= RP' + t;
updating point cloud: using rotation matrices R andtranslation vector t vs. P ″) workpiece And Q unmachine Updating is carried out;
and (3) calculating a registration error: calculating P unmachine And Q unmachine Of the registration error
If the registration error variation is less than the given value and the iteration times do not reach the maximum iteration times, returning to [0063]；
Outputting a rotation and translation matrix: outputting a rotation and translation matrix T obtained after iteration is finished R Specifically, the method comprises the steps of rotating a matrix R and translating a vector t;
the rotation matrix R and the translational vector t are obtained through the registration of the inner wall non-processing surface, and the updated workpiece scanning point cloud P ″ workpiece And the registration error between the inner wall of the scanning point cloud of the workpiece and the inner wall of the theoretical model under the pose is minimum, so that the optimal processing pose of the workpiece is obtained.
And a sixth step: and (5) rapidly transferring the workpiece. And after the measurement and calculation of the workpiece are completed, the workpiece is transferred to a machine tool workbench for machining. Firstly, the air source of the foundation plate is connected to quickly release the locking. And then, placing the clamp plate and the workpiece on a tray of the AGV moving platform by using a truss vehicle, and enabling the jig plate and the workpiece to transfer to a five-axis machine tool goods buffer area. Finally, the fixture plate and the workpiece are placed on a foundation plate on a five-axis machine tool workbench through a truss vehicle, and the workpiece quick-change transfer station is completed through the matching of the locking block and the positioning pin;
the seventh step: and adjusting a machining coordinate system. According to the rotation matrix and the translation vector obtained by calculation in [0069], quickly correcting an original machining coordinate system, so that the cutter can quickly find a workpiece to finish alignment and positioning of the workpiece;
eighth step: and starting the processing. And after the steps are completed, executing a machining program and starting machining.
The above examples of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. It will be appreciated by those skilled in the art that the invention can be embodied in many other forms without departing from the spirit or scope thereof. The present invention may encompass various modifications and substitutions without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (12)
1. A novel locating machining system and method based on multi-variety large thin-walled parts are characterized in that: the system comprises a server (1), four-axis measuring equipment (a cantilever type coordinate measuring machine (2), a laser scanner mounting interface (3), a joint arm type laser scanner (4)), a numerical control rotary table (5), a zero positioning tool (6), a base plate (7), a clamp plate (8), a large thin-wall part (9), an AGV moving platform (10), a five-axis numerical control machine (11) and an operator (12);
the server (1) is provided with control software of a cantilever type coordinate measuring machine (2), can control four-axis movement of the coordinate measuring machine, is also provided with point cloud measuring software which can be communicated with the laser scanner (4) and can acquire scanning point cloud data of a large thin-wall part in real time;
the articulated arm type laser scanner (4) is installed on a terminal interface (3) of the coordinate measuring machine by adopting threaded connection, and other measuring equipment such as a digital dial indicator and the like can also be installed on the interface;
the foundation plates (7) are respectively fixed on a rotary table working plane, an AGV moving platform and a five-axis machine tool working platform in a bolt connection mode, the clamp plates (8) are connected with the foundation plates (7) of all stations through zero point positioning tools (6), and the large thin-wall parts (9) are fixed on the clamp plates (8) through clamps such as pressing plates.
2. The novel position-finding machining system for the large-scale thin-walled parts with multiple varieties according to claim 1, characterized in that: based on the idea of 'external measurement alignment-internal processing', the processing pose of the large thin-wall part is quickly aligned, the process does not occupy the operation time of a machine tool, and the utilization rate of the machine tool and the production efficiency of a production line are greatly improved.
3. The novel position-finding machining system for the large-scale thin-walled parts with multiple varieties according to claim 1, characterized in that: the four-axis measuring equipment is combined with the articulated arm type laser scanner, so that the point cloud data of the full range of the inner wall and the outer wall of the large thin-wall part can be rapidly scanned and obtained. Four-axis measuring equipment can realize accurate positioning (positioning error is in 0.03mm within range), and its position change relation before and after removing can directly obtain, consequently, realize laser scanner and change the station fast based on the change volume of four-axis measuring equipment removal front and back position, can avoid traditional operation in-process that changes a station to measure the process of asking reversely, it is higher to change a station efficiency.
4. The novel position-finding machining system for the large-scale thin-walled workpiece with multiple varieties according to claim 1, characterized in that: the measuring method of the shaft measuring equipment matched with the articulated arm type laser scanner has higher flexibility, can be suitable for various large thin-wall parts such as cylinders, long strips and the like, and has higher equipment flexibility and richer application scenes compared with the existing measuring method only adopting the articulated arm scanner.
5. The novel position-finding machining system for the large-scale thin-walled parts with multiple varieties according to claim 1, characterized in that: the tail end of the four-axis measuring equipment is provided with a quick-change interface, so that the quick change of measuring equipment such as a joint arm scanner, a digital dial indicator and the like can be realized.
6. The novel position-finding machining system for the large-scale thin-walled parts with multiple varieties according to claim 1, characterized in that: after the crossbeam of the cantilever type coordinate measuring machine (2) extends to the farthest end, the deformation of the tail end needs to be less than 0.01mm/100N before and after the joint arm scanner is installed, and therefore the fact that the scanning and measuring process is not affected by the movement of the base of the joint arm scanner is guaranteed.
7. A novel locating processing method for a multi-variety large thin-wall part is characterized by comprising the following steps: the locating processing process comprises six steps: the method comprises the following steps that a workpiece is pressed on a clamp plate of a numerical control rotary table, a joint arm type laser scanner scans the workpiece, point cloud and a theoretical model are registered, the conversion quantity of a machining coordinate system is calculated, the workpiece is quickly positioned in a machine tool, the machining coordinate system is modified, and machining is started, wherein the method comprises the following steps:
the first step is as follows: a fixture plate (8) is connected and matched with a foundation plate (7) on the numerical control rotary table by using a zero point positioning tool (6), and a large thin-walled part (9) is fixed on the fixture plate of the numerical control rotary table through fixtures such as a pressure plate, and the like, so that the workpiece does not need to be accurately positioned, but the good clamping state is ensured, and the vibration in the machining process is reduced as much as possible;
the second step is that: scanning the outer wall and the inner wall of the large thin-walled part and the clamp plate by using an articulated arm type scanner (4), acquiring point cloud data of the actual pose of the large thin-walled part, and storing the point cloud data;
the third step: and (3) introducing a theoretical model and scanning point cloud data into control software, registering the clamp plate obtained by scanning with the theoretical clamp plate, registering the workpiece obtained by scanning with the theoretical workpiece on the basis, and calculating a pose transformation matrix. Calculating the adjustment sequence and adjustment quantity of each motion axis of the five-axis machine tool based on the matrix, and storing the adjustment sequence and adjustment quantity;
the fourth step: the fixture plate (8) and the workpiece (9) are transported to a five-axis machine tool (11) through an AGV moving platform (10), and the fixture plate (8) and the workpiece (9) are quickly positioned in the machine tool by using a zero point positioning tool (6);
the fifth step: correcting a machining coordinate system in a machine tool numerical control system according to the adjustment sequence and the adjustment quantity of the machine tool movement axis obtained in the third step;
and a sixth step: and starting to process the large thin-wall part by taking the corrected processing coordinate system as a zero point.
8. According to the first step of the novel position-finding machining method for the multiple-variety large thin-walled parts, as claimed in claim 7, the large thin-walled part (9) is fixed on a clamp plate (8) through clamps such as a pressure plate, the requirement for precision in the clamping process is not high, and the magnitude of the pressing force is determined according to the experience of workers, so that the workpiece can not move in the machining process, and the generation of large pressure-bearing deformation can be avoided.
9. The second step of the novel position-finding machining method for the multi-variety large thin-walled parts according to claim 7, wherein in order to ensure a better registration effect, most of the features of the fixture plate, the inner and outer walls of the large thin-walled part, and the like, especially the features of the critical dimension parts, need to be scanned heavily during the measurement process of the articulated arm.
10. The novel position-finding machining method for the large-scale thin-walled workpiece with multiple varieties according to claim 7, wherein the second step and the third step, the point cloud scanning, the coordinate system adjustment amount calculation and other steps are applicable to the large-scale thin-walled workpiece with multiple varieties.
11. According to the third and fifth steps of the novel locating machining method for the multiple-variety large thin-walled parts, when the adjustment sequence and the adjustment amount of each axis of the five-axis machine tool are calculated, the adjustment sequence and the adjustment amount of each axis are determined according to the specific machine tool, for example, for a Siemens 840D numerical control system, the adjustment sequence of each axis is X-Z-Y.
12. The fourth step of the novel position finding machining method for the multi-variety large thin-walled parts according to claim 7, wherein the rated load of the AGV moving platform needs to be higher than 3t, and normal circulation of the large thin-walled parts and the clamp plates is guaranteed.
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