A method for controlling deformation of NC milling of titanium alloy slender flange parts

Abstract

A method for controlling deformation of a titanium alloy slender edge strip part during CNC milling. The part is composed of a slender edge plate and a web plate, and has an L-shaped cross-section. There are transverse ribs between the inner edge plate and the web plate of the part. The web plate is a planar structure. The part is processed from a rectangular blank. The processing process includes process planning, a rough processing stage, a heat treatment stage, a semi-finishing stage, and a finishing stage. The left and right parts are symmetrically arranged in parallel on a piece of raw material. A slender "I"-shaped process connecting rib is provided between the left and right parts. A plurality of stress grooves are transversely processed on the vertical ribs of the process connecting ribs. A detection hole is made in the middle of the vertical ribs of the process connecting ribs. After the finishing is completed, the process connecting ribs around the part are milled in sections, and finally the process connecting ribs are cut off and removed by a fitter.

Description

Technical Field

[0001] The invention relates to the technical field of numerical control machining, in particular to a numerical control milling deformation control method for titanium alloy slender edge strip parts. Background Art

[0002] Among the various major structural parts of aircraft, titanium alloy slender edge strip parts are a typical structure widely used in key docking parts of various aircraft. This type of parts is slender, with an aspect ratio of generally more than 40:1, and weak resistance to bending deformation; one side is a flat structure, and the other side has a transverse rib structure between the inner edge plate and the web. In the CNC machining process of this type of parts, after the material removal of the parts on one side is completed, it is often due to the large residual internal stress inside the rough material. After the rough machining of the parts, the internal stress is released in large quantities, resulting in large deformation; at the same time, after heat treatment, it will also cause secondary stress release deformation, and the deformation produced often exceeds the allowable machining allowance range, resulting in out-of-tolerance or scrap, and huge quality risks.

[0003] In the production and processing of aircraft products, the traditional process manufacturing process adopts single-piece processing, which requires multiple removal of excess processes, multiple releases of deformation, repeated calibration and trial. As a result, there are huge quality risks, continuous processing is impossible, repeated clamping, large human intervention, long machine time, and a greatly extended production cycle. Summary of the invention

[0004] The present invention discloses a method for controlling deformation of titanium alloy slender edge strips during CNC milling. The method can solve the problems of deformation and heat treatment deformation that occur during CNC machining of aircraft parts with titanium alloy slender edge strip structures, thereby improving machining continuity, reducing human intervention, improving machining efficiency, and ensuring stable machining of titanium alloy slender edge strip structures.

[0005] A method for controlling deformation of a titanium alloy slender edge strip part during CNC milling, wherein the part is composed of a slender edge plate and a web plate to form an L-shaped structure in cross section, and there are transverse ribs between the inner edge plate and the web plate of the part, and the web plate is a plane structure. The part is processed from a rectangular blank, and the processing process includes process planning, rough processing stage, heat treatment stage, semi-finishing stage, and finishing stage, and is characterized in that it includes the following contents: 1) Process planning: The left and right parts are symmetrically arranged in parallel on a piece of raw material, and a slender "I"-shaped process connecting rib is provided between the left and right parts. The upper and lower transverse ribs of the "I"-shaped are respectively located at the two ends of the left and right parts, and the middle vertical rib of the "I"-shaped is located between the left and right parts. The length of the process connecting rib is large 1) The process connection ribs are equal in height to the length of the part body, and there is a process allowance between the process connection ribs and the part shape; 2) Rough machining stage: Rough machining is divided into two-sided machining, and two-sided unequal allowance machining is adopted. First, the outer surface of the web is rough-machined on the lower surface of the rough material, and a finishing allowance is left; then the flange plate and the inner surface of the web are rough-machined on the upper surface of the rough material, and the first finishing allowance is evenly left on the top of the flange plate, both sides of the flange plate and the inner surface of the web; when machining the inner surface of the web, multiple stress grooves are transversely machined on the vertical ribs of the process connection ribs; the height of the top of the flange plate is consistent with the height of the vertical ribs of the process connection ribs; a detection hole is made in the middle position of the vertical ribs of the process connection ribs, and the theoretical hole position of the detection hole is obtained; 3) Rough machining is completed After completion, annealing heat treatment is carried out to reduce the stress of rough processing. Before heat treatment, two pieces of the same raw materials are connected back to back with the head and tail directions consistent, and annealing heat treatment is carried out. Each raw material contains two parallel parts; 4) Semi-finishing stage: Before semi-finishing, the hole position of the detection hole on the process connection rib is first detected by the probe on the machine tool, and compared with the theoretical hole position of the detection hole, and the bending deformation and deformation direction of the raw material are analyzed. If the bending deformation is within 6mm and the warping deformation is within 0.5-1mm, normal subsequent processing can be carried out; during semi-finishing, first remove the finishing allowance of the outer surface of the web on the lower surface of the raw material, finish the outer surface of the web, and then align the top of the edge plate and the edge plate on the upper surface of the raw material. Semi-finishing is performed on both sides and the inner surface of the web, and part of the first finishing allowance is removed at the top of the flange plate, both sides of the flange plate and the inner surface of the web, leaving a second finishing allowance; 5) In the finishing stage, the hole positions of the detection holes on the process connection ribs are detected by the probe on the machine tool and compared with the theoretical hole positions of the detection holes to analyze the bending deformation and deformation direction. If the bending deformation is within 1 mm and the deformation direction is the width direction of the blank, subsequent processing can be performed normally. During finishing, the second finishing allowance is removed from the top of the flange plate, both sides of the flange plate and the inner surface of the web in turn, and the web surface and the transition surface inside the flange plate are processed in place; after finishing is completed, the process connection ribs around the parts are milled in sections, and finally the process connection ribs are cut off and removed by the fitter.

[0006] The CNC milling deformation control method of the titanium alloy slender edge strip parts is characterized in that during semi-finishing and finishing of the edge plate rib height, the tool is swung 90° horizontally and the axial direction is prioritized for cutting. The edge plate rib height is processed by the side edge of the tool to minimize the deformation of the edge plate.

[0007] The CNC milling deformation control method of the titanium alloy slender edge strip parts is characterized in that in the semi-finishing and finishing stages, when processing the inner and outer sides of the edge plate, the tool path is first axial layered cutting and then radial layered cutting.

[0008] The CNC milling deformation control method of the titanium alloy slender edge strip parts is characterized in that in the finishing stage, the finishing of the web surface adopts a cutting method of axial layering combined with radial layering, axial cutting priority, and layer-by-layer cutting from the outside to the inside.

[0009] The beneficial effects of the present application are as follows: the above-mentioned processing method has been tested by the inventor in actual production, and the deformation of the slender edge strip structure parts during the processing and heat treatment process can be controlled, the deformation size and deformation direction can be detected, the cutting process is stable, the cutting surface quality is good, and the edge plate wall thickness meets the design tolerance requirements, effectively avoiding the problem of the edge plate wall thickness size cannot be guaranteed due to the processing deformation and heat treatment deformation of the slender edge strip structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Schematic diagram of the structural parts of titanium alloy slender edge parts.

[0011] Figure 2 Schematic diagram of the left and right rough materials of titanium alloy slender edge parts.

[0012] Figure 3 Schematic diagram of the first side of the rough machining of the left and right parts of the titanium alloy slender edge part.

[0013] Figure 4 Schematic diagram of the second side rough machining status of the left and right parts of the titanium alloy slender edge part.

[0014] Figure 5 Schematic diagram of the left and right parts of the titanium alloy slender edge part after rough machining.

[0015] Figure 6 Schematic diagram of back-to-back heat treatment of two pieces of raw material of titanium alloy slender flange parts.

[0016] Figure 7 Schematic diagram of the milling tool clamping for the left and right parts of the titanium alloy slender flange part.

[0017] Figure 8 Schematic diagram of semi-finishing of left and right parts of titanium alloy slender flange parts.

[0018] Fig. 9 Schematic diagram of finishing of left and right parts of titanium alloy slender edge parts.

[0019] Fig.10 Schematic diagram of the connecting ribs after finishing the left and right parts of the titanium alloy slender flange part.

[0020] Explanation of the numbers in the figure: 1. Titanium alloy slender flange parts; 2. Flange plate; 3. Web plate; 4. Left parts; 5. Right parts; 6. Rough material; 7. Process connection ribs; 8. "U"-shaped stress groove; 9. Inspection hole; 10. Bolt through hole; 11. Milling tool; 12. Process connection ribs; DETAILED DESCRIPTION

[0021] The following description will be made by taking the CNC machining of the elongated flange structural component 1 as an example.

[0022] See attached Figure 1 The main structural features of the slender edge strip structural part 1 involved in this embodiment are: the part is a slender structure composed of a flat web 3 and a curved edge plate 2, and its cross section is "L"-shaped; the flat web 3 and the curved edge plate 2 are both thin-walled structures, with a wall thickness of 3mm (wall thickness tolerance ±0.15), an edge plate height of 65mm, a web width of 75mm, a part length of 3400mm, an aspect ratio generally reaching more than 40:1, and a weak ability to resist bending deformation; its material is aviation titanium alloy TC18.

[0023] See attached Figure 2 ,, adopts a symmetrical parallel arrangement design for the left and right parts. The slender edge strip left part 4 and the slender edge strip right part 5 are arranged side by side on the rectangular raw material 6 for processing. The left and right parts are arranged head to head and tail to tail, the distance between the head and tail is basically equal, and the slender edge plate is on the outermost side. The symmetrical distribution of the slender structure can reduce the bending deformation during the processing and heat treatment stages; at the same time, the bending rigidity of the slender edge plate is increased to reduce the bending deformation caused by heat treatment. In the middle of the symmetrical parallel arrangement of the left and right parts, a slender "I"-shaped process connecting rib 7 is added to separate the left and right parts of the parts, and is equidistant from the left part 4 and the right part 5; the length of the "I"-shaped process connecting rib 7 is greater than the length of the part body, and the entire length is connected to the part body through the process connecting rib; the "I"-shaped process connecting rib 7 is an equal height structure, and its height is higher than the height of the edge plate of the part body;

[0024] The parts processing process is divided into five stages: process planning, rough processing stage, heat treatment stage, semi-finishing stage, and finishing stage.

[0025] See attached Figure 3 , attached Figure 4 For rough machining, bolts and pressure plates are used to clamp the rough material 6. Figure 5, the rough machining is divided into two-sided machining, and two-sided unequal allowance machining is adopted. First, the outer surface of the web is rough-machined on the lower surface of the rough material 6, and a finishing allowance is left; then the flange plate 2 and the inner surface of the web 3 are rough-machined on the upper surface of the rough material 6, and the first finishing allowance is evenly left on the top of the flange plate 2, the sides of the flange plate 2 and the inner surface of the web 3; when machining the inner surface of the web 3, multiple stress grooves 8 are transversely machined on the vertical ribs of the process connection ribs 7; the height of the top of the flange plate is consistent with the height of the vertical ribs of the process connection ribs; a deformation detection hole 9 is made in the middle position of the vertical ribs of the process connection ribs, and the theoretical hole position of the detection hole 9 is obtained. When rough machining the inner shape, a number of "U"-shaped stress grooves 8 are segmented on the "I"-shaped process connection rib 7, and the spacing between the stress grooves 8 is about 1 / 6 of the length of the process connection rib 7, and the groove depth is 1 / 2 of the height of the connection rib, so as to achieve the purpose of releasing deformation. The two outer slender edge plates are roughly processed into equal height structures, the height of which is consistent with the "I"-shaped process connecting rib 7. A number of "U"-shaped stress grooves 8 are also milled out at the notched part of the top of the edge plate.

[0026] See attached Figure 5 After rough machining, a detection hole 9 is made in the middle of the "I"-shaped process connecting rib 7, and finally a plurality of bolt through holes 10 are made on the "I"-shaped process connecting rib 7.

[0027] See attached Figure 6 After the rough machining is completed, annealing heat treatment is first performed to reduce the rough machining stress. Before heat treatment, two pieces of the same raw material are connected back to back with the head and tail in the same direction, and annealing heat treatment is performed to reduce the warping deformation generated during the heat treatment stage. After the heat treatment, the hole position coordinates of the detection hole 9 are analyzed and compared with the theoretical hole position to analyze the deformation size and deformation direction.

[0028] See attached Figure 7 In the semi-finishing stage, a special milling tool 11 is used for processing. The left and right parts of the titanium alloy slender flange parts are placed on the milling tool 11 in a free state. The warping amount of the rough material 6 is detected with a feeler gauge. When the warping amount is within 0.5-1mm, the warped part needs to be filled with tin foil to ensure that there is no gap. External force is applied to clamp the parts before semi-finishing can be carried out normally. Then the probe on the machine tool is used to detect the hole position of the detection hole 9 on the "I"-shaped process connecting rib 7. If the bending deformation is within the range of 6mm, semi-finishing can be carried out normally. First, the finishing allowance of the outer surface of the web is removed from the lower surface of the rough material, and the outer surface of the web is finished. Then, the top of the flange plate, the two sides of the flange plate and the inner surface of the web are semi-finished on the upper surface of the rough material. Part of the first finishing allowance is removed from the top of the flange plate, the two sides of the flange plate and the inner surface of the web, leaving the second finishing allowance; see the attached Figure 7When semi-finishing the two sides of the edge plate, the outer shape of the edge plate 2 is processed first, and the outer shape of the edge plate 2 is uniformly left with a 1mm margin, and then the inner shape of the edge plate 2 is added, and the inner shape of the edge plate 2 is uniformly left with a 3mm margin. In order to ensure the bending rigidity of the edge plate 2 of the left and right parts, the web 3 is not processed temporarily. When semi-finishing the rib height of the edge plate 2, the traditional tool is used to vertically process the arc trough of the edge plate. Due to the small curvature of the arc trough, the bottom angle of the tool is very easy to break teeth, and the tool life is greatly reduced. Therefore, the tool is used to swing the horizontal axis 90° and the axial priority cutting method is used to process the height surface of the edge plate to minimize the deformation of the edge plate. When semi-finishing the inner and outer shapes of the edge plate 2, the tool is processed by the axial layered cutting first and then the radial layered cutting method, which is divided into 3 layers, and the cutting width of each layer is 1mm. The tool adopts an ordinary solid carbide tool with a tool diameter of φ25mm, a number of teeth of 4 teeth, a tool blade length greater than the height of the edge plate 2 by 65, a tool speed of 400RPM, and a feed speed of 120mm / min.

[0029] After semi-finishing, the clamping is released to release the stress. The probe on the machine tool is used to detect the hole position of the detection hole 9 on the "I"-shaped process connecting rib 7, and compared with the theoretical hole position, the bending deformation amount and deformation direction are analyzed. If the bending deformation amount is within the range of 1mm, the finishing can be carried out normally, and the deformation direction is the width direction of the blank.

[0030] See attached Fig. 9 After the outer shape of the edge plate 2 is finely processed, the inner shape of the edge plate 2 is processed, and after ensuring that the wall thickness of the edge plate 2 is 3mm, the web 3 and other structures are finally processed.

[0031] First, the web 3 is semi-finished, using a machine-clamped fast-feed milling cutter with a tool diameter of φ35mm and 4 teeth. The blade is a replaceable machine-clamped blade. The processing strategy of small cutting and fast feeding is adopted. The tool speed is 350RPM, the feed speed is 1400mm / min, and the cutting depth is 0.5mm. The semi-finishing of the web surface adopts the tool path of axial layering combined with radial layering, axial cutting priority, and cutting from the outside to the inside layer by layer. Then, the web 3 is finished, using ordinary solid carbide tools, with a tool diameter of φ25mm and 4 teeth. The finishing of the web surface adopts the tool path of axial layering combined with radial layering, axial cutting priority, and cutting from the outside to the inside layer by layer. The tool speed is 500RPM and the feed speed is 130mm / min. Then, the web surface and the inner transition surface of the edge plate are finished, and the angle end mill is used for finishing.

[0032] See attached Fig.10 Finally, the process connection ribs 12 connecting the rough material and the parts are milled in sections, and the process connection ribs 12 are cut off and removed by the fitter.

Claims

1. A method for controlling deformation of a titanium alloy slender flange part during CNC milling. The part is composed of a slender flange plate and a web plate, and has an L-shaped cross-section. There are transverse ribs between the inner flange plate and the web plate of the part. The web plate is a plane structure. The part is processed from a rectangular blank. The processing process includes process planning, rough processing stage, heat treatment stage, semi-finishing stage, and finishing stage. It is characterized in that It includes the following contents: 1) Process planning: The left and right parts are symmetrically arranged in parallel on a piece of rough material, and a slender "I"-shaped process connecting rib is set between the left and right parts. The upper and lower transverse ribs of the "I" shape are located at the two ends of the left and right parts respectively, and the middle vertical rib of the "I" shape is located between the left and right parts. The length of the process connecting rib is greater than the length of the part body, and the process connecting rib is an equal height structure. There is a process allowance between the process connecting rib and the part shape; 2) Rough processing stage: Rough processing is divided into two-sided processing, and two-sided unequal allowance processing is adopted. First, the outer surface of the web is rough-processed on the lower surface of the rough material. , and leave a finishing allowance; then roughly process the flange plate and the inner surface of the web on the upper surface of the raw material, and leave the first finishing allowance evenly on the top of the flange plate, both sides of the flange plate and the inner surface of the web; when processing the inner surface of the web, transversely process multiple stress grooves on the vertical ribs of the process connecting ribs; the height of the top of the flange plate is consistent with the height of the vertical ribs of the process connecting ribs; make a detection hole in the middle of the vertical ribs of the process connecting ribs, and obtain the theoretical hole position of the detection hole; 3) After the rough processing is completed, annealing heat treatment is carried out to reduce the rough processing stress. Before heat treatment, two pieces of the same raw materials are connected back to back, and the head and tail are square. 4) Semi-finishing stage: Before semi-finishing, first use the probe on the machine tool to detect the hole position of the detection hole on the process connection rib, and compare and analyze it with the theoretical hole position of the detection hole to analyze the bending deformation and deformation direction of the raw material. If the bending deformation is within 6mm and the warping deformation is within 0.5-1mm, normal subsequent processing can be performed. During semi-finishing, first remove the finishing allowance of the outer surface of the web on the lower surface of the raw material, finish the outer surface of the web, and then on the upper surface of the raw material, the top of the flange plate, the sides of the flange plate and The inner surface of the web is semi-finished, and part of the first finishing allowance is removed from the top of the flange plate, the sides of the flange plate and the inner surface of the web, leaving the second finishing allowance; 5) In the finishing stage, the position of the detection hole on the process connection rib is detected by the probe on the machine tool and compared with the theoretical position of the detection hole to analyze the bending deformation and deformation direction. The bending deformation is within 1mm, and the deformation direction is the width direction of the blank. Normal subsequent processing can be performed. During finishing, the second finishing allowance is removed from the top of the flange plate, the sides of the flange plate, and the inner surface of the web in turn, and the web surface and the transition surface inside the flange plate are processed in place; After finishing, the process connection ribs around the parts are milled in sections, and finally the process connection ribs are cut off and removed by the fitter.

2. The method for controlling deformation of a titanium alloy slender flange part by numerical control milling according to claim 1, characterized in that: When semi-finishing and finishing the edge plate rib height, the tool is swung 90° horizontally and the axial direction is cut first. The side edge of the tool processes the edge plate rib height to reduce edge plate deformation.

3. The method for controlling deformation of a titanium alloy slender flange part by numerical control milling according to claim 1, characterized in that: In the semi-finishing and finishing stages, when processing the inner and outer sides of the edge plate, the tool path is first axial layered cutting and then radial layered cutting.

4. The method for controlling deformation of a titanium alloy slender flange part by numerical control milling according to claim 1, characterized in that: In the finishing stage, the finishing of the web surface adopts a cutting method of axial layering combined with radial layering, axial cutting priority, and layer-by-layer cutting from the outside to the inside.

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