Numerical control machining method for multi-feature base plate

Abstract

The invention discloses a numerical control machining method for a multi-feature base plate, which comprises the following steps: designing a process data model to assist precise positioning of parts, numerical control stretch forming, flexible clamping and numerical control milling, so that efficient and precise digital manufacturing of the multi-feature base plate parts is realized. According to the method, the technological process of multi-feature base plate machining is simplified, the machining quality is good, and the production efficiency is high. The problem that efficient and accurate digital manufacturing cannot be achieved in the prior art is effectively solved.

Description

Technical Field

[0001] The invention belongs to the field of process equipment design of aviation manufacturing technology and relates to a processing method of a multi-feature pad. Background Art

[0002] In the aircraft development process, the fuselage wall panels often adopt the typical structure of "skin + pad". In order to facilitate the smooth passage of systems and structural parts, the pads are mostly designed to contain system through holes, irregular structural openings, complex contours, and multi-curvature thin-walled parts that fit the skin. The processing quality of this type of multi-feature pad is of great significance to the assembly efficiency and quality of the aircraft.

[0003] Since the pads are mostly double-curvature structures, roll bending cannot be used. The traditional pad processing method is to manually knock and cut the shape according to the skin mold score line. This method has low production efficiency, poor processing quality, poor surface forming degree, some margin, and requires a high level of worker skills. It cannot meet the production needs of efficient and precise digital manufacturing of aircraft sheet metal parts. Summary of the invention

[0004] The purpose of the present invention is to provide a method for processing a multi-feature pad to solve the problem that the prior art cannot achieve efficient and accurate digital manufacturing.

[0005] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0006] A CNC machining method for a multi-feature pad comprises the following steps:

[0007] Step 1: Design process data model

[0008] Firstly, the molding surface of the tooling die used for processing the skin at the corresponding position of the multi-feature pad is used as the design reference surface;

[0009] Secondly, the normal equal thickness of the theoretical outer surface of the aircraft is offset to the design reference surface with the help of 3D software to make it fit with the design reference surface. Then the contour line of the multi-feature pad is extracted and projected normally to the outer surface. The connection area viewing hole is designed to be added at the edge of the outer contour of the multi-feature pad.

[0010] Finally, the process data model surface is trimmed using the contour line projected onto the outer surface by the multi-feature pad, the viewing holes in the supplementary connection area, and the positioning hole information of the skin on the tooling mold; then the process data model surface is thickened to become a three-dimensional entity of the process data model, and the detail fillet is edited according to the tool situation. Finally, the positioning hole error is tested to see if it meets the manufacturing and assembly tolerance requirements of the pad;

[0011] Step 2: Prepare CNC machining program

[0012] Complete the CNC machining program and simulate the machining based on the three-dimensional entity of the process data model to optimize the tool trajectory;

[0013] Step 3: Cutting

[0014] After the pre-production inspection is completed, the rough material is cut, deburred and inspected according to the size of the three-dimensional entity of the process data model after adding the allowance to obtain the rough material of the pad part;

[0015] Step 4: Solution treatment and stretch forming

[0016] The rough material of the backing plate part is subjected to a solution treatment, and a CNC skin stretching machine is used to install a tooling die to longitudinally stretch the rough material of the backing plate part to form a backing plate part blank, and at least two positioning holes are processed at corresponding positions on the backing plate part blank based on the original positioning holes on the tooling die;

[0017] Step 5: Mark the blank of the pad part, and then perform eddy current conductivity test and hardness test;

[0018] Step 6: Flexible clamping and five-axis sheet metal contour milling

[0019] The five-axis sheet metal milling and drilling processing center adopts a two-point one-curved surface multi-point positioning method. The pad part blank is clamped on the five-axis sheet metal milling and drilling, and is accurately positioned according to the positioning holes. The pad part blank is milled according to the CNC machining program.

[0020] Step 7: Manually trim the area on the blank of the pad part that is not milled to the line and then conduct a semi-inspection;

[0021] Step 8: Surface treatment, painting, marking and inspection to obtain the processed multi-feature pad.

[0022] Furthermore, the reference surface is the surface for molding the inner surface of the skin.

[0023] Furthermore, during normal projection, the contour of the multi-feature pad should include the contours of all features on the multi-feature pad, including system through holes, irregular structure openings, and internal and external contours.

[0024] Furthermore, the design principle of the additional connection area viewing holes is: additional connection area viewing holes are set for non-linear contour change areas, areas with straight or approximately straight contour lines, and areas with outer shape gaps, and reinforcement structures are set in the areas between adjacent additional connection area viewing holes.

[0025] Furthermore, the width of the viewing hole in the supplementary connection area is not less than 25 mm; and the chord height between adjacent viewing holes in the supplementary connection area is not greater than 0.3 mm.

[0026] Furthermore, the process data model surface should completely include the outer shape surface, and both sides of the process data model surface in the length direction should extend to the positioning hole areas on the left and right sides of the tooling mold.

[0027] Furthermore, the distance between the two sides of the process data model surface in the width direction and the edge of the contour line of the multi-feature pad is not less than 300 mm, but cannot exceed the maximum shape of the tooling mold.

[0028] Furthermore, the requirement for the positioning hole error is that the deviation between the projection points of the positioning hole on the tooling mold and the process data model surface should be less than 0.15 mm.

[0029] Furthermore, the dimensions after the margin are 1.5 m in the length direction and 0.2-0.3 m in the width direction.

[0030] Furthermore, in the two points and one curved surface, the two points are any two positioning holes processed on the pad part blank in step four, and the one curved surface refers to the curved surface of the tooling mold.

[0031] Furthermore, the five-axis sheet metal milling and drilling processing center adopts a two-point-one-surface multi-point flexible tooling positioning method, and online detects the vacuum adsorption status of the multi-point flexible tooling.

[0032] Compared with the prior art, the present invention has the following technical features:

[0033] This method replaces the traditional manual cutting and forming process with allowance, and realizes the efficient and accurate digital manufacturing of a multi-feature pad part. The process data model design, CNC stretch forming, flexible clamping and CNC contour milling scheme in the method simplify the process flow of multi-feature pad processing, and has good processing quality and high production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a multi-feature pad part;

[0035] Figure 2 is the process data model;

[0036] Figure 3 It is the coordination between the process data model and the tooling mold positioning;

[0037] Figure 4 It is the additional connection area;

[0038] Figure 5 Schematic diagram of the chord height.

[0039] Explanation of the numbers in the figure: 1- tooling mold, 2- process data model surface, 3- multi-feature pad, 4- positioning hole, 5- additional connection area viewing hole. DETAILED DESCRIPTION

[0040] In conjunction with the accompanying drawings, the present invention provides a CNC machining method for a multi-feature pad. Analyze the contour features of this pad: direct CNC machining not only lacks a positioning reference and poor local adsorption and cannot be stretched, but also parts vibration during flexible clamping can easily lead to overcutting. Therefore, before CNC machining, it is necessary to design a three-dimensional process data model to assist in the coordinated positioning, local reinforcement, flexible clamping and CNC programming of the multi-feature pad. After the process data model design is completed, the multi-feature pad is stretched into shape using a CNC skin stretching machine, and then coordinated with the skin mold to position, and then the sheet metal contour milling equipment is used to CNC mill the inner and outer contour features of the pad, and finally the connection area is manually trimmed and supplemented. A CNC machining method for a multi-feature pad, comprising the following steps:

[0041] Step 1: Design the process data model.

[0042] First, the molding surface of the tooling mold used for processing the skin at the corresponding position of the multi-feature pad is used as the design reference surface; wherein the reference surface is the surface for molding the inner surface of the skin;

[0043] Secondly, with the help of three-dimensional software such as CAT IA, the normal equal thickness of the theoretical outer surface of the aircraft is offset to the design reference plane to make it fit with the design reference plane, and then the contour line of the multi-feature pad is extracted and normally projected to the outer surface, and the additional connection area viewing hole is designed at the outer contour edge of the multi-feature pad; wherein, when projecting normally, the contour line of the multi-feature pad should include the contour lines of all features on the multi-feature pad, and the features include system through holes, irregular structure openings, and inner and outer contours. The design principle of the additional connection area viewing hole is: for non-linear contour change areas, areas with straight or approximately straight contours, and areas with shape gaps, additional connection area viewing holes are set, and the areas between adjacent additional connection area viewing holes are set with reinforcement structures, such as reinforcing ribs; the width of the additional connection area viewing hole is not less than 25mm; the chord height between adjacent additional connection area viewing holes is not more than 0.3mm, so that the adjacent additional connection area viewing holes are approximately a straight line, which is convenient for processing and cutting;

[0044] Finally, the process data model surface is trimmed using the contour line projected onto the outer surface by the multi-feature pad, the viewing holes in the supplementary connection area, and the positioning hole information of the skin on the tooling mold; then the process data model surface is thickened to become a three-dimensional entity of the process data model, and the detail fillet is edited according to the tool situation (the fillet radius should not be less than the tool radius), and finally the positioning hole error is tested to see if it meets the manufacturing and assembly tolerance requirements of the pad;

[0045] Among them, the process data model surface should completely include the outer shape surface, and the two sides of the process data model surface in the length direction should extend to the positioning hole area on the left and right sides of the tooling mold; the two sides of the process data model surface in the width direction should be no less than 300mm away from the contour line edge of the multi-feature pad, but cannot exceed the maximum shape of the tooling mold, so as to ensure that there is enough adsorption and fixing area during subsequent five-axis sheet metal milling processing to prevent vibration and overcutting caused by insufficient adsorption.

[0046] The positioning hole error is: the deviation between the projection points of the positioning hole on the tooling mold and the process data model surface should be less than 0.15mm.

[0047] Step 2: Prepare CNC machining program.

[0048] Complete the CNC machining program and simulate the machining based on the three-dimensional entity of the process data model to optimize the tool trajectory;

[0049] Step 3: Cutting the materials.

[0050] After completing the pre-work inspection, the rough material is cut, deburred and inspected according to the size after adding the allowance to the three-dimensional entity of the process data model to obtain the rough material of the pad part; the size after the allowance is 1.5m in the length direction and 0.2-0.3m in the width direction.

[0051] Step 4: Solution treatment and stretching.

[0052] The rough material of the pad part is solution treated, and the CNC skin stretching machine is used to install the tooling mold to longitudinally stretch the rough material of the pad part to form a pad part blank. Based on the original positioning holes on the tooling mold, at least two positioning holes are processed at corresponding positions on the pad part blank for positioning in the subsequent five-axis sheet metal contour milling process.

[0053] Step 5: Mark the blank of the pad part, then perform eddy current conductivity test and hardness test, and proceed to the next step after passing the test.

[0054] Step 6: Flexible clamping and five-axis sheet metal contour milling.

[0055] The five-axis sheet metal milling and drilling machining center adopts a two-point-one-curved-surface multi-point flexible tooling positioning method. The pad part blank is clamped on the equipment, the vacuum adsorption status of the multi-point flexible tooling is detected online, precise positioning is performed according to the positioning holes, and the pad part blank shape is milled according to the CNC machining program.

[0056] In the two points and one curved surface, the two points are any two positioning holes processed on the pad part blank in step 4, and the one curved surface refers to the curved surface of the tooling mold.

[0057] Step 7: Manually trim the area on the pad part blank that has not been milled to the line and then perform a semi-inspection.

[0058] Step 8: Surface treatment, painting, marking and inspection to obtain the processed multi-feature pad.

Claims

1. A CNC machining method for a multi-feature pad, characterized in that: The following steps are involved: Step 1: Design process data model Firstly, the molding surface of the tooling die used for processing the skin at the corresponding position of the multi-feature pad is used as the design reference surface; Secondly, the normal equal thickness of the theoretical outer surface of the aircraft is offset to the design reference surface with the help of 3D software to make it fit with the design reference surface. Then the contour line of the multi-feature pad is extracted and projected normally to the outer surface. The connection area viewing hole is designed to be added at the edge of the outer contour of the multi-feature pad. Finally, the process data model surface is trimmed using the contour line projected onto the outer surface by the multi-feature pad, the viewing holes in the supplementary connection area, and the positioning hole information of the skin on the tooling mold; then the process data model surface is thickened to become a three-dimensional entity of the process data model, and the detail fillet is edited according to the tool situation. Finally, the positioning hole error is tested to see if it meets the manufacturing and assembly tolerance requirements of the pad; Step 2: Prepare CNC machining program Complete the CNC machining program and simulate the machining based on the three-dimensional entity of the process data model to optimize the tool trajectory; Step 3: Cutting After the pre-production inspection is completed, the rough material is cut, deburred and inspected according to the size of the three-dimensional entity of the process data model after adding the allowance to obtain the rough material of the pad part; Step 4: Solution treatment and stretch forming The rough material of the backing plate part is subjected to a solution treatment, and a CNC skin stretching machine is used to install a tooling die to longitudinally stretch the rough material of the backing plate part to form a backing plate part blank, and at least two positioning holes are processed at corresponding positions on the backing plate part blank based on the original positioning holes on the tooling die; Step 5: Mark the blank of the pad part, and then perform eddy current conductivity test and hardness test; Step 6: Flexible clamping and five-axis sheet metal contour milling The machining center of the five-axis sheet metal milling and drilling machine adopts a two-point one-curved surface multi-point positioning method. The blank of the pad part is clamped on the five-axis sheet metal milling and drilling machine, and is accurately positioned according to the positioning holes. The blank of the pad part is milled according to the CNC machining program. Step 7: Manually trim the area on the blank of the pad part that is not milled to the line and then conduct a semi-inspection; Step 8: Surface treatment, painting, marking and inspection to obtain the processed multi-feature pad.

2. The CNC machining method of a multi-feature pad according to claim 1, characterized in that: The reference surface is the surface for shaping the inner surface of the skin.

3. The CNC machining method of a multi-feature pad according to claim 1, characterized in that: During normal projection, the contour of the multi-feature pad should include the contours of all features on the multi-feature pad, including system through holes, irregular structure openings, and internal and external contours.

4. The CNC machining method of a multi-feature pad according to claim 1, characterized in that: The design principle of the additional connection area viewing hole is: additional connection area viewing holes are set for non-linear contour change areas, areas with straight or approximately straight contour lines, and areas with shape gaps, and reinforcement structures are set in the areas between adjacent additional connection area viewing holes.

5. The CNC machining method of a multi-feature pad according to claim 1, characterized in that: The width of the viewing hole in the supplementary connection area shall not be less than 25mm; the chord height between adjacent viewing holes in the supplementary connection area shall not be greater than 0.3mm.

6. The CNC machining method of a multi-feature pad according to claim 1, characterized in that: The process data model surface should completely include the outer shape surface, and both sides of the process data model surface in the length direction should extend to the positioning hole areas on the left and right sides of the tooling mold.

7. The CNC machining method of a multi-feature pad according to claim 1, characterized in that: The distance between the two sides of the process data model surface in the width direction and the edge of the contour line of the multi-feature pad shall not be less than 300 mm, but shall not exceed the maximum shape of the tooling mold.

8. The CNC machining method of a multi-feature pad according to claim 1, characterized in that: The requirement for the positioning hole error is that the deviation between the projection points of the positioning hole on the tooling mold and the process data model surface should be less than 0.15 mm.

9. The CNC machining method of a multi-feature pad according to claim 1, characterized in that: The dimensions after the margin are 1.5 m in the length direction and 0.2-0.3 m in the width direction.

10. The CNC machining method of a multi-feature pad according to claim 1, characterized in that: In the two points and one curved surface, the two points are any two positioning holes processed on the pad part blank in step 4, and the one curved surface refers to the curved surface of the tooling mold.

Images