Numerical control machining method of complex thin-wall curved surface structure additive manufacturing part

Abstract

A numerical control machining method for a complex thin-wall curved surface structure additive manufacturing part comprises the steps that a special positioning tool is installed on a five-coordinate machining center workbench, the complex thin-wall curved surface part is installed on the special positioning tool, and a selected feature position point on the part serves as an original point of a machining coordinate system; the numerical control machining program is imported into a five-coordinate machining center, and part machining is completed through the five-coordinate machining center in a five-axis five-linkage machining mode; the method comprises the following steps: transferring a part and a special positioning tool to a three-coordinate measuring machine workbench together, taking an original point of a part machining coordinate system as an original point of a measuring coordinate system, completing multi-point measurement of the machined surface of the part, drawing a theoretical contour line and a tolerance zone of the part in CAD software, importing multi-point measurement data into the CAD software, and fitting the theoretical contour line and the tolerance zone into an actual contour line; and observing whether the actual contour line is completely positioned between the theoretical contour line and the tolerance zone, if the actual contour line meets the requirement, judging that the part processing is qualified, and if the actual contour line does not meet the requirement, judging that the part processing is unqualified.

Description

Technical Field

[0001] The invention belongs to the technical field of CNC machining, and in particular relates to a CNC machining method for additively manufactured parts with complex thin-walled curved surface structures. Background Art

[0002] With the trend of large-scale, lightweight and complex structural design of aircraft engine parts, the use of traditional processing and manufacturing technology has problems such as long processing cycle, high cost and low material utilization rate, which makes it difficult to meet the design and processing requirements. The use of additive manufacturing technology can make up for the shortcomings of traditional processing technology and further realize the rapid near-net forming of complex thin-walled curved parts. At the same time, the formed parts can also ensure excellent mechanical properties.

[0003] However, complex thin-walled curved parts manufactured by additive manufacturing need to achieve a higher surface roughness due to assembly or special working conditions, so corresponding machining processes are required later. However, complex thin-walled curved parts usually have no reliable positioning reference, so there are problems such as difficulty in processing and positioning, and inaccurate positioning. In addition, deformation and vibration are prone to occur during the machining process, and alignment is frequent, which leads to long alignment time, poor machining accuracy and low machining efficiency. At the same time, the complex thin-walled curved parts after machining are still difficult to measure. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a CNC machining method for additively manufactured parts with complex thin-walled curved surface structures. With the help of special positioning tooling and a five-coordinate machining center, a reliable positioning reference is provided for the complex thin-walled curved surface parts, thereby reducing the difficulty of machining positioning, improving positioning accuracy, reducing deformation and vibration during machining, reducing the number of alignment times, reducing alignment time, and improving machining accuracy and efficiency. After the complex thin-walled curved surface parts are machined, the complex thin-walled curved surface parts are measured with the help of a three-coordinate measuring machine and CAD software, effectively reducing the difficulty of measurement.

[0005] In order to achieve the above-mentioned object, the present invention adopts the following technical solution: A CNC machining method for additively manufactured parts with complex thin-walled curved surface structure, comprising the following steps:

[0006] Step 1: Positioning

[0007] Prepare a set of special positioning fixtures, first install the special positioning fixtures on the workbench of the five-axis machining center, and then position and clamp the complex thin-walled curved surface parts manufactured by additive manufacturing onto the special positioning fixtures, and then select a feature position point on the complex thin-walled curved surface parts, and determine the feature position point as the origin of the machining coordinate system;

[0008] Step 2: Processing

[0009] First, compile the CNC machining program in UG software, and then import the compiled CNC machining program into the five-axis machining center. The CNC machining program consists of three parts: rough milling, semi-finishing milling, and fine milling. Then, run the CNC machining program in the five-axis five-link machining mode. After the rough milling program is completed, the machining surface of the complex thin-walled curved surface parts has a 0.2mm margin; after the semi-finishing milling program is completed, the machining surface of the complex thin-walled curved surface parts has a 0.1mm margin; after the fine milling program is completed, the machining process of the complex thin-walled curved surface parts is completely completed;

[0010] Step 3: Measure

[0011] First, the processed complex thin-walled curved surface parts are transferred together with the special positioning tooling to the workbench of the three-coordinate measuring machine, and the origin of the processing coordinate system of the complex thin-walled curved surface parts is used as the origin of the measurement coordinate system. Then, the three-coordinate measuring machine is used to perform multi-point measurement on the processing surface of the complex thin-walled curved surface parts. Then, the theoretical contour line and tolerance zone of the complex thin-walled curved surface parts are drawn in the CAD software. Then, the multi-point measurement data of the three-coordinate measuring machine is imported into the CAD software, and the multi-point measurement data is fitted into the actual contour line in the CAD software. Finally, it is observed whether the actual contour line is all between the theoretical contour line and the tolerance zone. If the requirements are met, the processing size of the complex thin-walled curved surface parts is judged to be qualified. If not, the processing size of the complex thin-walled curved surface parts is judged to be unqualified.

[0012] The special positioning tooling includes a base plate, a part positioning platform, an edge pressure plate, an edge clamping bolt, a middle pressure plate, a middle clamping bolt and a fastening bolt; the part positioning platform is placed on the upper surface of the base plate, and the part positioning platform is fixedly connected to the base plate by fastening bolts; the upper surface of the part positioning platform is set as the part positioning surface, and the complex thin-walled curved surface part is placed on the part positioning platform, and the complex thin-walled curved surface part is tightly fitted with the part positioning surface; the edge pressure plate overlaps the upper surface of the edge of the complex thin-walled curved surface part, and the edge pressure plate and the base plate are fixedly connected by the edge clamping bolts; the middle pressure plate overlaps the circumferential upper surface of the middle hole opening of the complex thin-walled curved surface part, and the middle pressure plate and the part positioning platform are fixedly connected by the middle clamping bolts.

[0013] Beneficial effects of the present invention:

[0014] The CNC machining method of the additively manufactured parts with complex thin-walled curved surface structure of the present invention uses a special positioning tool to cooperate with a five-coordinate machining center to provide a reliable positioning reference for the complex thin-walled curved surface parts, reduce the difficulty of machining positioning, improve positioning accuracy, reduce deformation and vibration during machining, reduce the number of alignment times, reduce alignment time, and improve machining accuracy and efficiency; when the complex thin-walled curved surface parts are machined, the measurement of the complex thin-walled curved surface parts is achieved with the help of a three-coordinate measuring machine and CAD software, effectively reducing the difficulty of measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the structure of the splash plate in the embodiment (viewing angle 1);

[0016] Figure 2 Schematic diagram of the structure of the splash plate in the embodiment (viewing angle 2);

[0017] Figure 3 Schematic diagram of the combination of the splash plate and the special positioning tool in the embodiment (the edge is pressed tightly);

[0018] Figure 4 It is a schematic diagram of the combination of the splash shield and the special positioning tool in the embodiment (the middle part is pressed tightly);

[0019] Figure 5 It is a structural schematic diagram of a parts positioning platform of a special positioning tool in the embodiment;

[0020] Figure 6 It is a schematic diagram for measuring whether the machining dimensions of the outer contour surface of the splash plate are qualified by coordinating the theoretical contour line, the tolerance zone and the fitted actual contour line in the CAD software;

[0021] In the figure, 1 is a complex thin-walled curved surface part, 2 is a base plate, 3 is a part positioning platform, 4 is an edge pressure plate, 5 is an edge clamping bolt, 6 is a middle pressure plate, 7 is a middle clamping bolt, 8 is a fastening bolt, 9 is a part positioning surface, 10 is a theoretical contour line, 11 is a tolerance zone, and 12 is an actual contour line. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] A CNC machining method for additively manufactured parts with complex thin-walled curved surface structures, comprising the following steps:

[0024] Step 1: Positioning

[0025] Prepare a set of special positioning tooling, first install the special positioning tooling on the workbench of the five-axis machining center, and then position and clamp the complex thin-walled curved surface part 1 manufactured by additive manufacturing onto the special positioning tooling, and then select a characteristic position point on the complex thin-walled curved surface part 1, and determine the characteristic position point as the origin of the machining coordinate system;

[0026] Step 2: Processing

[0027] First, compile the NC machining program in UG software, and then import the compiled NC machining program into the five-axis machining center. The NC machining program consists of three parts: rough milling, semi-finishing milling, and fine milling. Then, run the NC machining program in the five-axis five-link machining mode. After the rough milling program is executed, the machining surface of the complex thin-walled curved surface part 1 has a 0.2mm margin; after the semi-finishing milling program is executed, the machining surface of the complex thin-walled curved surface part 1 has a 0.1mm margin; after the fine milling program is executed, the machining process of the complex thin-walled curved surface part 1 is completely completed;

[0028] Step 3: Measure

[0029] First, the processed complex thin-walled curved surface part 1 is transferred together with the special positioning tool to the workbench of the three-coordinate measuring machine, and the origin of the processing coordinate system of the complex thin-walled curved surface part 1 is used as the origin of the measurement coordinate system. Then, the three-coordinate measuring machine is used to perform multi-point measurement on the processing surface of the complex thin-walled curved surface part 1, and then the theoretical contour line 10 and tolerance zone 11 of the complex thin-walled curved surface part 1 are drawn in the CAD software. Then, the multi-point measurement data of the three-coordinate measuring machine is imported into the CAD software, and the multi-point measurement data is fitted into the actual contour line 12 in the CAD software. Finally, it is observed whether the actual contour line 12 is completely located between the theoretical contour line 10 and the tolerance zone 11. If the requirements are met, the processing size of the complex thin-walled curved surface part 1 is judged to be qualified. If the requirements are not met, the processing size of the complex thin-walled curved surface part 1 is judged to be unqualified.

[0030] like Figures 3 to 5 As shown, the special positioning tooling includes a base plate 2, a part positioning platform 3, an edge pressure plate 4, an edge clamping bolt 5, a middle pressure plate 6, a middle clamping bolt 7 and a fastening bolt 8; the part positioning platform 3 is placed on the upper surface of the base plate 2, and the part positioning platform 3 is fixedly connected to the base plate 2 by the fastening bolt 8; the upper surface of the part positioning platform 3 is set as a part positioning surface 9, and the complex thin-walled curved surface part 1 is placed on the part positioning platform 3, and the complex thin-walled curved surface part 1 is tightly fitted with the part positioning surface 9; the edge pressure plate 4 overlaps the upper surface of the edge of the complex thin-walled curved surface part 1, and the edge pressure plate 4 and the base plate 2 are fixedly connected by the edge clamping bolt 5; the middle pressure plate 6 overlaps the circumferential upper surface of the middle hole opening of the complex thin-walled curved surface part 1, and the middle pressure plate 6 and the part positioning platform 3 are fixedly connected by the middle clamping bolt 7.

[0031] In this embodiment, Figure 1 , 2As shown, the complex thin-walled curved surface part 1 is a splash plate in an aero-engine. The splash plate is a complex micro-curved thin-walled structural part, which is prepared by a laser selective melting forming process. In order to meet the requirements of the assembly and use conditions of the splash plate, the internal circular hole and the outer contour surface of the splash plate need to be machined. However, since the splash plate has high requirements for dimensional accuracy, the traditional machining method faces the following difficulties:

[0032] ①. No positioning reference

[0033] The splash plate part is a special-shaped structural part, which is mainly composed of a rotating surface. The main body of the part has no reliable positioning reference, and the processing and positioning are difficult, which is prone to inaccurate positioning problems.

[0034] ②, Thin-walled parts have poor rigidity

[0035] The splash plate parts have thin wall thickness and high dimensional accuracy requirements, and the overall part has an open structure, which leads to insufficient rigidity of the parts. During machining, especially when cutting with large allowances, the parts are easily deformed due to excessive cutting force, resulting in dimensional deviations.

[0036] ③. Part size cannot be measured

[0037] The machined dimensions of splash plate parts are mostly spatial dimensions, which are difficult to measure using conventional measurement methods and measuring tools. When using a three-coordinate measuring machine for measurement, it is impossible to select an effective alignment reference due to the irregular shape of the parts, making it difficult to measure the parts.

[0038] To this end, the CNC machining method for additively manufacturing parts with complex thin-walled curved surface structures of the present invention can be used to machine the splash plate parts.

[0039] First, prepare a set of special positioning tooling, which is manufactured according to the size and shape characteristics of the splash plate. First, install the special positioning tooling on the workbench of the five-axis machining center, and then place the splash plate on the part positioning table 3 so that the bottom curved surface of the splash plate is tightly fitted with the part positioning surface 9 on the top of the part positioning table 3, and then use the edge pressure plate 4 and the edge clamping bolts 5 to press the four corner points of the splash plate onto the part positioning table 3.

[0040] After the splash plate is pressed and fixed, the center of the central circular hole of the splash plate is used as a characteristic position point, and the characteristic position point is used as the origin of the processing coordinate system, and then the processing of the central circular hole of the splash plate is completed.

[0041] After the central circular hole of the splash plate is processed, the circumferential edge of the central circular hole of the splash plate is pressed against the part positioning table 3 using the central pressure plate 6 and the central clamping bolt 7, and then the edge pressure plate 4 and the edge clamping bolt 5 are removed.

[0042] Import the NC machining program compiled in UG software into the five-axis machining center. This NC machining program is used as the machining program for the outer contour surface of the splash plate. The NC machining program consists of three parts: rough milling, semi-finishing milling, and fine milling. When all the preparations are completed, the NC machining program can be started. After the rough milling program is executed, a 0.2mm margin is left on the machining surface; after the semi-finishing milling program is executed, a 0.1mm margin is left on the machining surface; after the fine milling program is executed, the machining process of the outer contour surface of the splash plate is completely completed.

[0043] The processed splash plate is transferred together with the special positioning tool to the workbench of the three-dimensional coordinate measuring machine, and the origin of the processing coordinate system of the splash plate is used as the origin of the measurement coordinate system. Then the three-dimensional coordinate measuring machine is used to perform multi-point measurement on the outer contour surface of the splash plate.

[0044] After the multi-point measurement of the outer contour surface of the splash plate is completed, the theoretical contour line 10 and the tolerance zone 11 of the outer contour surface of the splash plate are first drawn in the CAD software, and then the multi-point measurement data of the three-dimensional coordinate measuring machine are imported into the CAD software, and the multi-point measurement data are fitted into the actual contour line 12 in the CAD software. Figure 6 As shown, finally observe whether the actual contour line 12 is completely located between the theoretical contour line 10 and the tolerance zone 11. If the requirement is met, the processing size of the splash plate is judged to be qualified. If the requirement is not met, the processing size of the splash plate is judged to be unqualified.

[0045] The solutions in the embodiments are not intended to limit the protection scope of the present invention. All equivalent implementations or changes that do not deviate from the present invention are included in the protection scope of the present invention.

Claims

1. A CNC machining method for additively manufactured parts with complex thin-walled curved surface structures, characterized in that: The steps include: Step 1: Positioning Prepare a set of special positioning fixtures, first install the special positioning fixtures on the workbench of the five-axis machining center, and then position and clamp the complex thin-walled curved surface parts manufactured by additive manufacturing onto the special positioning fixtures, and then select a feature position point on the complex thin-walled curved surface parts, and determine the feature position point as the origin of the machining coordinate system; Step 2: Processing First, compile the CNC machining program in UG software, and then import the compiled CNC machining program into the five-axis machining center. The CNC machining program consists of three parts: rough milling, semi-finishing milling, and fine milling. Then, run the CNC machining program in the five-axis five-link machining mode. After the rough milling program is completed, the machining surface of the complex thin-walled curved surface parts has a 0.2mm margin; after the semi-finishing milling program is completed, the machining surface of the complex thin-walled curved surface parts has a 0.1mm margin; after the fine milling program is completed, the machining process of the complex thin-walled curved surface parts is completely completed; Step 3: Measure First, the processed complex thin-walled curved surface parts are transferred together with the special positioning tooling to the workbench of the three-coordinate measuring machine, and the origin of the processing coordinate system of the complex thin-walled curved surface parts is used as the origin of the measurement coordinate system. Then, the three-coordinate measuring machine is used to perform multi-point measurement on the processing surface of the complex thin-walled curved surface parts. Then, the theoretical contour line and tolerance zone of the complex thin-walled curved surface parts are drawn in the CAD software. Then, the multi-point measurement data of the three-coordinate measuring machine is imported into the CAD software, and the multi-point measurement data is fitted into the actual contour line in the CAD software. Finally, it is observed whether the actual contour line is all between the theoretical contour line and the tolerance zone. If the requirements are met, the processing size of the complex thin-walled curved surface parts is judged to be qualified. If not, the processing size of the complex thin-walled curved surface parts is judged to be unqualified.

2. The CNC machining method for additively manufactured parts with complex thin-walled curved surface structures according to claim 1, characterized in that: The special positioning tooling includes a base plate, a part positioning platform, an edge pressure plate, an edge clamping bolt, a middle pressure plate, a middle clamping bolt and a fastening bolt; the part positioning platform is placed on the upper surface of the base plate, and the part positioning platform is fixedly connected to the base plate by fastening bolts; the upper surface of the part positioning platform is set as the part positioning surface, and the complex thin-walled curved surface part is placed on the part positioning platform, and the complex thin-walled curved surface part is tightly fitted with the part positioning surface; the edge pressure plate overlaps the upper surface of the edge of the complex thin-walled curved surface part, and the edge pressure plate and the base plate are fixedly connected by the edge clamping bolts; the middle pressure plate overlaps the circumferential upper surface of the middle hole opening of the complex thin-walled curved surface part, and the middle pressure plate and the part positioning platform are fixedly connected by the middle clamping bolts.

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