CN110587237B

CN110587237B - Numerical control machining method for thin-wall curved surface edge strip structural part of airplane

Info

Publication number: CN110587237B
Application number: CN201910896440.2A
Authority: CN
Inventors: 田辉; 史靠军; 尹佳; 马梁栋; 杨旭
Original assignee: Xian Aircraft Industry Group Co Ltd
Current assignee: Xian Aircraft Industry Group Co Ltd
Priority date: 2019-09-20
Filing date: 2019-09-20
Publication date: 2021-04-20
Anticipated expiration: 2039-09-20
Also published as: CN110587237A

Abstract

The invention discloses a numerical control machining method for a thin-wall curved surface edge strip structure part of an airplane, wherein the part is machined from a square blank, and the technological process is divided into three stages: rough machining, aging and fine machining. By the method, the problems of serious vibration, cutter relieving and the like in numerical control machining of the airplane part with the thin-wall curved surface edge strip structure can be solved, and normal numerical control machining of the thin-wall curved surface edge strip structure of the airplane is guaranteed.

Description

Numerical control machining method for thin-wall curved surface edge strip structural part of airplane

Technical Field

The invention relates to the technical field of numerical control machining, in particular to a numerical control machining method for an airplane thin-wall curved surface edge strip structure.

Background

In the design of modern airplane parts, due to the requirement of overall design performance, thin-wall structures are increasingly adopted, wherein the thin-wall curved surface edge strip structures are common airplane typical thin-wall structure parts and are widely applied to the structural design of various airplane typical parts. Because the weight of the part needs to be strictly controlled, the wall thickness of a plurality of edge strip structures is designed to be very small, is greatly beyond the structural wall thickness of the traditional airplane part and belongs to a weak rigid structure, and great difficulty is brought to numerical control machining.

The invention relates to an airplane thin-wall curved surface edge strip structure part which is mainly structurally characterized in that: the part is a slender arc-shaped structure formed by a plane web plate and a curved surface edge plate, and the cross section of the part is L-shaped; its plane web and curved surface listrium are thin wall structure, and general wall thickness is all not more than 1.5mm, and the ratio of listrium height (or web width) and wall thickness is greater than 20: 1; the curved surface edge plate is a non-straight-line curved surface; the plane web plate is provided with a plurality of openings or through holes; the material is aviation titanium alloy, aluminum alloy or steel.

The main difficulties in the machining of such parts are: the wall thickness of the whole structure of the part is very small and greatly exceeds that of the traditional part, so that the cutting vibration is aggravated under the action of cutting force during cutting processing, the quality of a cutting surface cannot be ensured, and the normal processing cannot be realized; meanwhile, due to the fact that the cutter back-off phenomenon of the thin-wall weak-rigidity structure during cutting is very serious, the machining size cannot be guaranteed.

Disclosure of Invention

The invention discloses a numerical control machining method for an airplane thin-wall curved surface edge strip structure part, which can solve the problems of serious vibration, cutter back-off and the like in numerical control machining of the airplane part with the thin-wall curved surface edge strip structure and ensure normal numerical control machining of the airplane thin-wall curved surface edge strip structure. The specific method comprises the following steps:

the airplane thin-wall curved surface edge strip structural part is formed by processing a square blank, and the technological process is divided into three stages: rough machining, aging and fine machining.

And (5) a rough machining stage. The method is divided into two-side processing. The upward side of the edge plate of the part is defined as an A surface in advance, and the bottom surface side of the web plate is defined as a B surface. Firstly, the surface B faces upwards, the processing of the upper surface reference of the blank and the rough processing of the surface B are carried out, and the allowance of 1-2 mm is uniformly reserved on the bottom surface of the web plate during the rough processing of the surface B. And then, facing the surface A upwards, and processing the upper surface of the blank and roughly processing the surface A. When the surface A is roughly processed, the allowance of 1-2 mm is uniformly reserved at the top of the curved surface edge plate; the allowance of 4-6 mm is uniformly reserved on the two sides of the curved surface edge plate, so that the ratio of the height to the wall thickness of the curved surface edge plate is not more than 4: 1; the web surface is uniformly remained with 4-6 mm of allowance. After the rough machining of the surface A is finished, the periphery of the workpiece is connected with the blank through technological lap joint.

And (5) aging. And after the rough machining is finished, naturally aging the workpiece for more than 48 hours. If the material is titanium alloy or steel, annealing heat treatment is firstly carried out to reduce rough machining stress.

And (5) finishing. Reference surface correction and reference hole correction are performed on both sides of A, B. And then, finishing the surface B upwards, and finishing the openings or through holes on the web plate surface and the web plate surface, and the outer transition surfaces of the web plate surface and the edge plate in place respectively.

And after the surface B is processed, adhering a damping block on the web surface. The damping block is a metal block with the same thickness as the web plate surface.

Then, the surface A faces upwards, and the surface A is finely processed by five steps.

Firstly, the top of the curved surface edge plate is finely processed in place.

And secondly, performing finish machining on the inner side and the outer side of the curved surface edge plate. Because the curved surface flange plate is a non-ruled curved surface, a large machining error can be generated when a common end mill is used for milling five-axis side edges, and the larger the curvature is, the larger the machining error is, and the wall thickness is difficult to ensure. Therefore, in the invention, the finish machining of the inner side and the outer side of the curved surface flange plate is carried out by five-axis side edge milling by using a drum-type end mill. The side edge of the drum-shaped end mill is arc-shaped, and the curvature radius of the arc-shaped end mill is slightly smaller than that of the curved surface flange plate along the height direction. When the inner side and the outer side of the curved surface edge plate are precisely machined, a feeding mode combining radial layering with axial layering and radial cutting priority is adopted; the radial layering adopts a feeding mode that the cutting allowance is gradually decreased layer by layer from outside to inside and in the radial direction, the cutting width of the last layer is not more than 0.5mm, and the layer is generally divided into 2-3 layers; the axial layering is carried out by adopting a milling strategy of alternately machining the inner side and the outer side of the edge plate from high to low. When the cutting edge is cut to the innermost layer, the side edge of the drum-shaped end mill is tangent to the curved face flange plate.

And thirdly, performing finish machining on the web surface by using a common end mill. The finish machining of the web surface adopts a feed mode of combining axial layering with radial layering, giving priority to axial cutting and cutting layer by layer from the outer side to the inner side; the radial layering adopts a small cutting width cutting mode (the cutting width is not more than 25 percent of the diameter of the cutter); the axial layering adopts a mode of gradually decreasing the cutting allowance layer by layer, the axial layering is generally divided into 2-3 layers, and the cutting depth of the last layer is not more than 0.5 mm.

And fourthly, performing finish machining on the web surface and the transition surface in the flange plate, and performing finish machining in place by adopting a five-axis swing angle mode of a pen-shaped end mill.

And fifthly, carrying out process lap joint on the periphery of the workpiece by sectional milling, separating the workpiece from the peripheral blank, and uniformly reserving a plurality of process connection points. The process connection points are cut off and removed by a bench worker.

According to the machining method, through the inspection of an inventor in actual production, the rigidity of the thin-wall curved surface edge strip structure part in the machining process is guaranteed, the cutting process is stable, the quality of the cut surface is good, the size meets the design tolerance requirement, and the problems that the quality defect of the cut surface and the size of the wall thickness cannot be guaranteed due to cutting vibration and cutter back-off of the thin-wall curved surface structure are effectively solved.

The invention is further described below with reference to the following examples and the accompanying drawings.

Description of the drawings:

FIG. 1 is a schematic view of structural parts of an aircraft thin-wall curved edge strip.

FIG. 2 is a schematic cross-sectional view of the open angle portion of the thin-wall curved edge strip structure.

FIG. 3 is a schematic cross-sectional view of a closed corner of a thin-walled curved edge strip structure.

FIG. 4 is a schematic diagram of rough machining state of structural parts of thin-wall curved-surface edge strips of an airplane.

FIG. 5 is a cross-sectional view of a thin-walled curved-surface cap structural component of an aircraft in a rough machining state.

FIG. 6 is a sectional view of a first-side state of a thin-walled curved rim strip structural part of an aircraft.

Figure 7 schematic view of a damper block.

FIG. 8 is a sectional view of a second side of an aircraft thin-walled curved platform structural member.

FIG. 9 is a schematic diagram showing the inner and outer side states of a curved face flange plate milled by five-axis side edges of a drum-type end mill.

FIG. 10 is a schematic diagram of a five-axis swing angle milling web surface and a flange transition surface of the pen-shaped end mill.

FIG. 11 is a schematic view of a process lap joint for segment milling the periphery of a workpiece.

The numbering in the figures illustrates: 1. thin-wall curved-surface edge strip structure parts; 2. a curved face margin plate; 3. a planar web; 4. a through hole; 5. a blank; 6. a reference hole; 7. carrying out process lapping; 8. an outer transition surface; 9. a damper block; 10. margin of the top of the edge plate; 11. a drum-type end mill; 12. a side edge of a drum-type end mill; 13. an inner transition surface; 14. a pen-shaped end mill; 15. and (4) connecting points of the process.

Detailed Description

The numerical control machining of the thin-wall curved surface edge strip structural part of the airplane is taken as an example for explanation.

Referring to the attached

drawings

1, 2 and 3, the thin-wall curved edge strip structural part 1 related to the embodiment has the following main structural characteristics: the part is a slender arc-shaped structure formed by a plane web plate 3 and a curved surface edge plate 2, and the cross section of the part is L-shaped; the planar web and the curved surface edge plate are both of thin-wall structures, the wall thickness is 1.2mm (the wall thickness tolerance is +/-0.1), the height of the edge plate is 35mm, and the width of the web is 45 mm; the curved surface edge plate is a non-straight-line curved surface; the web plate is provided with a plurality of through holes 4; the material is aeronautical titanium alloy TC 4.

Referring to the attached figure 4, the airplane thin-wall curved surface edge strip structural part 1 is formed by processing a square blank 5, and the technological process is divided into three stages: rough machining, aging and finish machining.

Referring to fig. 5, the rough machining stage is divided into two-sided machining. The upward side of the edge plate of the part is defined as an A surface in advance, and the bottom surface side of the web plate is defined as a B surface. Firstly, the B surface faces upwards, the machining of the upper surface reference of the blank and the rough machining of the B surface are carried out, reference holes 6 are formed, and 2mm allowance is uniformly reserved on the bottom surface of the web plate during the rough machining of the B surface. And then, the A surface is upwards facing, the processing of the upper surface of the blank and the rough processing of the A surface are carried out, the top of the curved surface edge plate 2 uniformly leaves 2mm allowance during the rough processing of the A surface, the two sides of the curved surface edge plate 2 uniformly leave 4mm allowance, the web plate 3 uniformly leaves 4mm allowance, and after the rough processing of the A surface is completed, the workpiece is connected with the blank 5 all around through a process lap joint 7.

After the rough machining is finished, annealing heat treatment is firstly carried out, and rough machining stress is reduced; and naturally aging for more than 48 hours.

Referring to fig. 6, in the finishing stage, A, B two-sided datum plane correction and datum hole correction are performed. And then, finishing the surface B upwards, and finishing the through holes on the web surface and the web surface, and the outer transition surface 8 of the web surface and the edge plate in place.

Referring to fig. 7, after the surface B is processed, the damping block 9 is adhered to the surface of the web plate by using super glue. The damping block is an aluminum alloy block with the same profile as the web plate surface and the same thickness.

Referring to fig. 8, the a side is then faced up and finish machining of the a side is performed.

First, the top margin 10 of the curved flange 2 is finished in place using a cylindrical end mill.

Then, finish machining of the inner and outer sides of the curved face flange 2 is performed. In the invention, the finish machining of the inner side and the outer side of the curved surface flange plate is carried out by five-axis side edge milling by using a drum-shaped end mill 11, which is shown in the attached figure 9. The side edge 11 of the drum-shaped end mill is arc-shaped, and the curvature radius Rt of the arc-shaped end mill is slightly smaller than the curvature radius Rw of the curved surface edge plate along the height direction; the diameter of the bottom of the drum-shaped end mill is phi 25mm, the number of teeth is 4, and the material is hard alloy. When the inner side and the outer side of the curved surface edge plate are precisely machined, a feeding mode combining radial layering with axial layering and radial cutting priority is adopted; the radial layering adopts a feeding mode that the cutting allowance is gradually decreased from outside to inside and radial cutting allowance is gradually decreased, 2 layers are formed, the cutting width of the first layer is 3.5mm, and the cutting width of the second layer is 0.5 mm; the axial layering is carried out by adopting a milling strategy of alternately processing the inner side and the outer side of the edge plate from high to low, and the axial cutting depth is 3 mm; the allowance cutting sequence is shown in fig. 8. When the cutting edge is cut to the innermost layer, the side edge of the drum-shaped end mill is tangent to the curved face flange plate. The tool rotation speed was 500RPM and the feed speed was 130mm/min during machining.

And then, carrying out finish machining on the web surface, wherein a cylindrical end mill is adopted, the diameter of a cutter is phi 25mm, the number of teeth is 4, and the material is hard alloy. The finish machining of the web surface adopts a feed mode of combining axial layering with radial layering, giving priority to axial cutting and cutting layer by layer from the outer side to the inner side; the allowance cutting sequence is shown in fig. 8; the radial cutting width is 5 mm; the axial direction is divided into 2 layers, the cutting depth of the first layer is 3.5mm, and the cutting depth of the second layer is 0.5 mm. The tool speed was 500RPM, and the feed speed was 130 mm/min.

Referring to fig. 10, the web face and the flange inner transition face 13 are then finished in place by a five-axis swing angle mode of a pen-shaped end mill 14.

Referring to fig. 11, finally, the peripheral process lap joint of the workpiece is milled in sections, the workpiece is separated from the peripheral blank, and a plurality of process connection points 15 are uniformly reserved. The process connection points are cut off and removed by a bench worker.

Claims

1. A numerical control machining method for an airplane thin-wall curved surface edge strip structural part is characterized in that a square blank is used for completing part machining through the following steps:

step 1 rough machining stage predefines ascending one side of part curved surface flange and is the A face in advance, web bottom surface one side is the B face, rough machining stage divide into A, B two-sided processing, A, B two sides are processed and are upwards faced earlier with B, carry out the processing of blank upper surface benchmark and the rough machining of B face, the web bottom surface evenly leaves 1-2 mm surplus, upwards face A again, carry out the processing of blank upper surface and the rough machining of A face, the surplus of 1-2 mm is evenly left at curved surface flange top, 4-6 mm surplus is evenly left at curved surface flange both sides, the surplus of 4-6 mm is evenly left to the web face, the work piece is connected with the blank through the technology overlap joint all around, make the ratio of height and the wall thickness of curved surface flange be not more than 4: 1;

step 2, after the rough machining in the aging stage is finished, naturally aging the workpiece for more than 48 hours, and if the workpiece is made of titanium alloy or steel, annealing heat treatment is firstly carried out to reduce rough machining stress;

step 3, in the finish machining stage, firstly, reference surface correction and reference hole correction of A, B two surfaces are carried out, then the B surface faces upwards, openings or through holes on the web surface and the web surface, and outer transition surfaces of the web surface and the curved surface edge plate are respectively processed in place, damping blocks are bonded on the web surface, then the A surface faces upwards, finish machining of the A surface is carried out in five steps, and the method specifically comprises the following steps:

firstly, finely machining the top of a curved surface edge plate in place;

secondly, a drum-type end mill is adopted, finish machining is carried out on the inner side and the outer side of the curved surface edge plate in a five-axis side edge milling mode, when finish machining is carried out on the inner side and the outer side of the curved surface edge plate, a feeding mode that radial layering is combined with axial layering and radial cutting is preferred is adopted, a feeding mode that cutting allowance is gradually decreased from outside to inside and radial cutting allowance is adopted for radial layering, the cutting width of the last layer is not more than 0.5mm, the axial layering is carried out by a milling strategy that the inner side and the outer side of the curved surface edge plate are alternately machined from high to low, and when the innermost layer is radially cut, the side edges of the drum-type end mill and the curved surface;

thirdly, finish machining of the web surface adopts a feed mode of combining axial layering with radial layering and giving priority to axial cutting and cutting layer by layer from the outer side to the inner side, wherein the radial layering adopts a small cutting width cutting mode, the cutting width is not more than 25% of the diameter of a cutter, the axial layering adopts a mode of gradually decreasing the cutting allowance layer by layer, and the cutting depth of the last layer is not more than 0.5 mm;

fourthly, performing finish machining on the web surface and the inner transition surface of the curved surface edge plate in a five-axis swing angle mode by adopting a pen-shaped end mill;

and fifthly, carrying out process lap joint on the periphery of the workpiece by sectional milling, separating the workpiece from the peripheral blank, uniformly reserving a plurality of process connection points, and cutting off and removing the process connection points by a bench worker.