Large-diameter conical high-density grid wall thickness control method

Abstract

The invention provides a method for controlling the wall thickness of a large-diameter conical high-density grid. The method comprises the following steps: sensing initial static deviation; initial static deviation elimination: executing a measurement program based on a measurement compensation device, and controlling each point location to carry out space translation along the direction of the cutter shaft according to a preset thickness so as to obtain a new milling track; process static deviation sensing is carried out, milling is carried out according to a new milling track, and a single area is divided into a plurality of areas again by executing clustering operation; and process static deviation elimination: performing layered milling on the plurality of divided areas, measuring the grid wall thickness during milling of each layer, comparing the generated wall thickness deviation with a first process static deviation elimination threshold value, and judging whether to trigger an intervention process static deviation elimination program or not according to a comparison result until the target wall thickness is met. According to the method, the deviation between most of the reference and the milling track in the high-density grid milling procedure can be realized, so that the wall thickness precision of the high-density grid is greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tank manufacturing, and particularly relates to a large-diameter conical high-density grid wall thickness control method. BACKGROUND

[0002] The tank bottom is a key structural part of a missile body, bears internal pressure load, and serves as a main load carrier for increasing a delivery interface, and is a structure with the largest difficulty and longest manufacturing cycle in the manufacturing of the missile body structure. The tank bottom of a certain type of carrier rocket is a conical structure, as shown in FIG. 1, with a large opening of about 5 meters and a small opening of about 2 meters, and is an open structure, and high-density grids are distributed on the tank bottom, with a thickness of about 4 mm. From the design structure, the open structure design without constraints at the large and small ends determines the weak stiffness and thin wall product characteristics, and increases the deformation problem in the manufacturing of the tank bottom. Figure 1

[0003] The advanced process of "overall forming + machining" is an effective way to solve the problems of the traditional process of the tank bottom, and has absolute advantages such as high precision, good reliability, and green environmental protection. For the machining link in the overall manufacturing of the tank bottom, a machining process of "turning equal-thickness thinning + milling grid openings" is adopted, and the removal amount of the whole product in the whole process is more than 70%. In the key process of milling to ensure the grid wall thickness precision, irregular deformation caused by a series of processes such as material removal, reference deviation, and residual stress release brings great difficulty to the grid wall thickness precision control.

[0004] The essence of the large-diameter conical high-density grid wall thickness control is the deviation control problem between the reference and the milling track. Based on this element, there are mainly two kinds of existing milling methods: one is the surface guarantee method, and the other is the grid adjustment method. The surface guarantee method has the following disadvantages: the residual thickness of the grid is formed by the inner surface reference and the processed surface, and the milling precision is determined by the deviation program of the inner surface reference. Therefore, the commonly used measures for the surface guarantee method to reduce the surface reference deviation to achieve the milling precision are mainly clamping measures, and the whole jig or suction cup is used to achieve the surface guarantee purpose. However, the effect of the surface guarantee is poor during the clamping process, and there are problems such as not adhering to the jig and insufficient suction force, and it is often difficult to achieve the milling precision.

[0005] The grid adjustment method has the following disadvantages: the grid adjustment method is to split a plurality of continuous grids into a single grid under the condition of allowing a certain surface reference deviation, to reduce the deviation between the milling track and the reference by reducing the milling track, and to mill. The surface deviation of the single grid is often less than the thickness tolerance, so the milling of the single grid can meet the wall thickness tolerance requirement. However, this method has a large limitation on the size of the grid, and the surface deviation of the large grid often exceeds the thickness tolerance, and the milling method of the single grid has extremely low efficiency and cannot meet the part machining requirement.​ SUMMARY

[0006] Therefore, the present application aims to provide a large-diameter conical high-density grid wall thickness control method to solve at least one of the above problems.

[0007] To achieve the above purpose, the technical scheme of the present application is as follows: The present application provides a large-diameter conical high-density grid wall thickness control method, comprising: Initial static deviation sensing, by dividing the high-density grid into regions, and numbering the single grid according to the circumferential region, the initial milling and washing of the single region grid is performed according to the theoretical milling trajectory, and the outer surface of the grid is taken as the milling trajectory surface; Initial static deviation elimination, based on the measurement compensation device to execute the measurement program, to obtain the coordinate point data, tool axis angle data and wall thickness data of the device, and to control the spatial translation of each point along the tool axis direction according to the predetermined thickness, to obtain a new milling trajectory; Process static deviation sensing, according to the new milling trajectory for milling, and using the new measurement trajectory for measurement, the minimum wall thickness of each grid in the single region is counted and the clustering operation is performed, and the single region is re-divided into multiple regions; Process static deviation elimination, by layering the divided multiple regions for milling, and measuring the grid wall thickness during each layer milling, comparing the generated wall thickness deviation with the preset first process static deviation elimination threshold, and determining whether to trigger the intervention process static deviation elimination program according to the comparison result, until the target wall thickness is met.

[0008] Further, the theoretical milling trajectory is set to a predetermined size of avoidance space around the grid, and then used as the measurement program.

[0009] Further, the translation distance is the Euclidean distance, and its formula is as follows: ; In the formula, represents the translation distance value, represents the wall thickness data value, represents the set target thickness value.

[0010] Further, the clustering method comprises: According to 50% of the preset wall thickness tolerance band, the minimum value to the maximum value in the wall thickness data is sorted in order and cut, and the single region is divided into multiple regions.

[0011] Further, by statistically processing the wall thickness data after layered milling, when the wall thickness deviation is greater than the first process dynamic deviation elimination threshold, the process static deviation elimination procedure is intervened, and the next layer milling track and measurement track are re-planned.

[0012] Further, it also includes: When the product is processed to the last layer, the wall thickness deviation coefficient of the last layer is defined, and when the wall thickness deviation is less than the second process static deviation elimination threshold, it is considered that the wall thickness deviation is controllable, and the process static deviation elimination action is cancelled.

[0013] Further, the second process static deviation elimination threshold = the first process static deviation elimination threshold x the wall thickness deviation coefficient.

[0014] Compared with the prior art, the large-diameter conical high-density grid wall thickness control method has the following beneficial effects: The large-diameter conical high-density grid wall thickness control method can realize the deviation between the reference and the milling track in most of the high-density grid milling procedures, thereby greatly improving the high-density grid wall thickness precision. BRIEF DESCRIPTION OF DRAWINGS

[0015] The drawings constituting a part of this application are used to provide a further understanding of this application, the illustrative embodiments of this application and the description thereof are used to explain this application, and do not constitute an improper limitation on this application. In the drawings: Figure 1 The box bottom structure of the launch vehicle according to the embodiment of the application is shown in the figure; Figure 2 The large-diameter conical high-density grid wall thickness control method according to the embodiment of the application is shown in the figure; Figure 3 The grid division schematic diagram according to the embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical scheme and advantages of the application more clear, the application is further described in detail below in combination with specific embodiments and with reference to the drawings.

[0017] It should be noted that, unless otherwise defined, technical terms or scientific terms used in the embodiments of the present application shall have the common meaning understood by one of ordinary skill in the art to which the embodiments of the present application belong. The terms "first", "second" and similar terms used in the embodiments of the present application do not represent any order, number or importance, but are only used to distinguish different components. The terms "include" or "contain" and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right" and the like are only used to represent relative positional relationships, and when the absolute positions of the described objects are changed, the relative positional relationships can also be changed accordingly.

[0018] As described in the above background, the essence of the large-diameter conical high-density grid wall thickness control is the deviation control problem between the reference and the milling trajectory. When there is a deviation between the reference and the milling trajectory, the wall thickness after milling will naturally have a deviation. Such a deviation can be divided into an initial deviation and a process deviation according to the time of occurrence. The initial deviation is the deviation that exists in the reference surface before milling. The process deviation is the deviation that is continuously formed in the milling process. Similarly, according to the dynamic characteristics of the deviation, it can be divided into static deviation and dynamic deviation. The static deviation is the deviation that exists before single milling. The dynamic deviation is the deviation that is continuously generated in the milling process.

[0019] Based on the high-density grid milling process of the conical bottom, the wall thickness control needs to eliminate the following three types of deviations: ① Initial static deviation. The existing deviation between the reference surface and the milling trajectory before turning and before milling.

[0020] ② Process static deviation. The dynamic deviation generated in the Nth milling process becomes the static deviation of the N+1th milling, also known as the staticization of the process dynamic deviation.

[0021] The elimination of the deviation must be preceded by the perception of the deviation. The perception of the deviation ① and the deviation ② is technically feasible due to their static characteristics.

[0022] Therefore, through the accurate analysis of the large-diameter conical high-density grid deviation control elements, the embodiments of the present application provide a complete process method and process to realize the perception and elimination method of the initial static deviation and the process static deviation.

[0023] The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0024] Please refer to Figure 2 The embodiments of the present application provide a large-diameter conical high-density grid wall thickness control method, which specifically includes the following steps: Step S101: Initial static deviation perception. The high-density grid is divided into regions, and the single grid is numbered according to the circumferential region. The single region grid is initially milled and exposed to light according to the theoretical milling trajectory, and the outer surface of the grid is used as the milling trajectory surface.

[0025] Specifically, in this embodiment, to improve the efficiency of the milling motion path and facilitate further deviation detection, the high-density mesh is divided into regions. First, the mesh is divided into five equal parts circumferentially, named Q01-Q05, as follows: Figure 3 As shown. The individual grids are numbered according to the circumferential region. For example, grid number 1-1-20 is located in the first row and 20th column of region Q01.

[0026] First, for a single region, a theoretical milling trajectory is compiled in the theoretical model. The theoretical milling trajectory is used to perform initial milling on the mesh until all outer surfaces of the mesh are exposed to light. At this point, the outer surfaces of the mesh are considered as the milling trajectory surfaces.

[0027] Step S102: Initial static deviation elimination. Based on the measurement compensation device, a measurement program is executed to obtain the coordinate point data of the device, the tool axis angle data, and the wall thickness data. According to the predetermined thickness, each point is controlled to move spatially along the tool axis direction to obtain a new milling trajectory.

[0028] Specifically, in this embodiment, an electromagnetic ultrasonic measuring device is mounted on the machine tool spindle via a tool holder. The front end is an electromagnetic ultrasonic thickness measuring module, and the middle end is a data communication module (including a WIFI module). The electromagnetic ultrasonic thickness measuring module collects thickness data from the front end and communicates with the industrial control computer's receiver via the WIFI module. Simultaneously, the machine tool PLC and the industrial control computer communicate via serial port to obtain the real-time position information of the electromagnetic ultrasonic thickness measuring device.

[0029] The theoretical milling trajectory is recessed by 1mm around the grid to create a clearance space, which is then used as the measurement program. The measurement program is executed to obtain the device coordinate point data and the tool axis angle information. , , , , The wall thickness data and the deviation between the wall thickness data and the predetermined thickness are the initial static deviation.

[0030] Combine theoretical procedures, device coordinate point data, and cutter shaft angle information ( , , , , ) and wall thickness data ( By setting the target thickness This causes each point to be spatially translated along the tool axis direction, with the translation distance being the Euclidean distance. This yields a new milling trajectory, which eliminates the initial static deviation.

[0031] Step S103: Sensing static deviation in the process, milling is performed according to the new milling trajectory, and measurements are taken using the new measurement trajectory. The minimum wall thickness of each grid in a single region is statistically analyzed and clustering is performed to re-divide the single region into multiple regions.

[0032] Specifically, in this embodiment, milling is performed using a new milling trajectory, and measurements are taken using a new measurement trajectory. The minimum wall thickness of each grid in a single region is statistically analyzed and clustered. The clustering principle is based on 50% of the designed wall thickness tolerance zone. Taking the 1mm tolerance zone of this product as an example, the minimum and maximum values ​​of the wall thickness data are sorted, and then divided into multiple regions by 0.5mm. This step is for sensing dynamic deviations.

[0033] If there is no dynamic deviation, the wall thickness deviation after milling should be zero due to the new milling trajectory. However, the dynamic deviation generated during the milling process causes unevenness in the wall thickness after milling. This unevenness is closely related to the milling conditions and material properties, and cannot be quantified. The method provided in this embodiment is a trial cutting method. Through trial cutting, a preliminary judgment of the dynamic deviation can be made, and large dynamic deviations during the milling process can be avoided by classifying and dividing the process.

[0034] Step S104: Elimination of static deviation in the process. This involves performing layered milling on multiple divided areas and measuring the mesh wall thickness during each layer of milling. The wall thickness deviation is compared with the preset first static deviation elimination threshold. Based on the comparison result, it is determined whether to trigger the intervention of the static deviation elimination program until the target wall thickness is met.

[0035] Specifically, in this embodiment, the trial cutting partitioning method in S103 can detect and avoid some dynamic deviations, but it cannot truly eliminate them. As milling progresses and more material is removed, the need to eliminate dynamic deviations remains. Therefore, a first-process static deviation elimination threshold is defined, namely... After layer milling, the wall thickness data is statistically analyzed. When the wall thickness deviation exceeds the dynamic deviation elimination threshold, the error is considered. At this time, the static deviation elimination procedure is initiated, and S102 is repeated to replan the milling trajectory and measurement trajectory for the next layer. When the product is machined to the last layer, a deviation elimination action must be performed in principle to ensure product accuracy. However, a deviation coefficient L for the last layer can be defined, which is applied when the wall thickness deviation is less than the second dynamic deviation elimination threshold. If the wall thickness deviation is considered controllable, the elimination action can be cancelled.

[0036] Taking this conical high-density mesh as an example, the high-density mesh has two thicknesses: 8mm and 4mm. The initial milling thickness is 20mm. The timing for initial static deviation elimination intervention, i.e., the first intervention for deviation elimination, is 13mm and 12mm respectively, considering high milling efficiency. In subsequent layer cutting, the wall thickness deviation after layer cutting is judged, and the static deviation elimination threshold is determined. Take 80% of the design tolerance, which is 0.8mm. When the wall thickness deviation is greater than 0.8mm, the elimination process is initiated. For thicknesses of 10mm and 6mm, the final elimination intervention is initiated, with the layer deviation coefficient L set to 5 / 8. When the wall thickness deviation is less than 0.5, the wall thickness deviation is considered controllable, and the elimination process is cancelled.

[0037] The method described in this embodiment, by employing a high-density mesh static deviation elimination method and standardizing the determination and elimination intervention method for dynamic deviation staticization, can realize the deviation between most of the references and milling trajectories in the high-density mesh milling procedure, thereby greatly improving the wall thickness accuracy of the high-density mesh.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

[0039] The embodiments of this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of this application.

Claims

1. A method for controlling the wall thickness of a large-diameter conical high-density mesh, characterized in that, include: Initial static deviation perception is achieved by dividing a high-density grid into regions and numbering individual grids according to the circumferential region. The individual grids are then initially milled according to the theoretical milling trajectory, and the outer surface of the grid is used as the milling trajectory surface. Initial static deviation is eliminated by executing a measurement program based on the measurement compensation device to obtain the device's coordinate point data, cutter axis angle data, and wall thickness data. Based on the predetermined thickness, each point is controlled to spatially translate along the cutter axis direction to obtain a new milling trajectory. The process static deviation is perceived, milling is performed according to the new milling trajectory, and measurement is performed using the new measurement trajectory. The minimum wall thickness of each grid in a single region is statistically analyzed and clustering is performed to re-divide the single region into multiple regions. The process static deviation elimination is achieved by performing layered milling on multiple divided areas and measuring the mesh wall thickness during each layer milling. The wall thickness deviation is compared with the preset first process static deviation elimination threshold. Based on the comparison result, it is determined whether to trigger the intervention process static deviation elimination procedure until the target wall thickness is met.

2. The method according to claim 1, characterized in that: The theoretical milling trajectory is then reduced to a predetermined size of clearance space around the grid as the measurement procedure.

3. The method according to claim 1, characterized in that, The translation distance is a Euclidean distance, and its formula is as follows: ； In the formula, This represents the translation distance value. This represents the wall thickness data value. This indicates the set target thickness value.

4. The method according to claim 1, characterized in that, The clustering method includes: Clustering is performed based on 50% of the preset wall thickness tolerance zone. The minimum to maximum values ​​in the wall thickness data are sorted in order and then segmented to divide a single region into multiple regions.

5. The method according to claim 1, characterized in that: By statistically analyzing the wall thickness data after layered milling, when the wall thickness deviation exceeds the dynamic deviation elimination threshold of the first process, the static deviation elimination program is initiated, and the milling trajectory and measurement trajectory of the next layer are replanned.

6. The method according to claim 1, characterized in that, Also includes: When the product is processed to the last layer, the wall thickness deviation coefficient of the last layer is defined. If the wall thickness deviation is less than the second process static deviation elimination threshold, the wall thickness deviation is considered to be controllable, and the process static deviation elimination action is canceled.

7. The method according to claim 6, characterized in that: The static deviation elimination threshold of the second process = the static deviation elimination threshold of the first process × the wall thickness deviation coefficient.

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