Airframe engine flame tube head vortex finder mounting hole machining fixture and method

Abstract

The application discloses an aero-engine flame tube head vortex finder mounting hole processing clamp and method, the processing clamp comprises a bottom plate, a mandrel, a positioning plate, a nut, a supporting block one, a positioning pin support and an angular hole, the clamp solves the problems of the thin wall, poor rigidity and no effective support of the aero-engine flame tube itself, ensures the controllable deformation of the flame tube after unloading, solves the accurate alignment problem of the workpiece center and the angle, ensures the position precision processing qualified, the application adopts a mechanical processing mode which has been considered unfeasible all the time, replaces the laser cutting mode to process the flame tube head vortex finder mounting hole, and the shape and position precision fully meet the requirements, and the processing qualified rate is improved from zero to 100%.

Description

Technical Field

[0001] This invention relates to the field of machining technology for thin-walled flame tube casings of aero-engines, specifically to machining fixtures and methods for mounting holes of vortex generators at the head of aero-engine flame tubes. Background Technology

[0002] like Figure 1 The main structure of a certain aero-engine's flame tube consists of five parts: the outer ring, the rear section of the outer ring, the inner ring, the rear section of the inner ring, and the head, all welded together. The diameter of the mounting hole for the vortex generator at the flame tube head is required to be Φ38 (+0.062, 0), and the positional tolerances for the inner ring circle A reference, the angular hole C on the sidewall of the inner ring, and the positive flame tube head B reference are required to be Φ0.2.

[0003] The part has a wall thickness of 1mm, a large diameter, and an open ring-shaped cavity structure with poor rigidity. If machining is chosen, the following problems will arise: First, there is no effective clamping surface, and the part is prone to deformation during clamping and pressing; second, the angular hole C is located on the inner ring sidewall, making it difficult to align, and the angular hole itself has a large machining tolerance of 0.1mm, which cannot guarantee the positional accuracy using a locating pin; third, machining vibration, machining deformation, and deformation after unloading will lead to dimensional deviations.

[0004] If laser cutting is used, due to the limitations of laser cutting methods and equipment, the equipment alignment is done by focal point alignment, which relies on visual alignment and has low precision. This makes it difficult to meet the positional accuracy requirements. Furthermore, the remelted layer after processing has a significant impact on the hole diameter. After processing, the hole diameter is out of tolerance, with an actual diameter of Φ38 to Φ38.2 and a pass rate of zero. The positional accuracy is also out of tolerance, with an actual diameter of Φ0.14 to Φ0.43 and a pass rate of zero.

[0005] Patent CN 115740807 A discloses a method for processing impact holes in a floating wall flame tube. It uses laser cutting technology. By adjusting the position of the laser head and rotating the worktable, the center of the laser head is aligned with the center of each pre-set positioning reference hole on the floating wall flame tube with a large end allowance. The remelted layer after laser drilling has a significant impact on the hole diameter. After processing, the hole diameter does not meet the requirements.

[0006] Summary of the Invention This invention addresses the problem that the thin walls, poor rigidity, and lack of effective support of the aero-engine flame tube itself lead to machining deformation, resulting in a zero pass rate for the diameter and position accuracy of the head vortex mounting hole. It provides a machining fixture and method for the head vortex mounting hole of the aero-engine flame tube.

[0007] The technical solution adopted in this invention is: A machining fixture for the mounting hole of the vortex generator at the head of an aero-engine flame tube includes a base plate. A mandrel perpendicular to the base plate is located at the center of the base plate. The mandrel passes through the flame tube. A positioning plate and a nut for pressing and positioning the flame tube are fitted on the mandrel. The flame tube includes an inner ring and an outer ring. A support block is provided on the base plate to support the bottom of the inner ring of the flame tube, with the bottom of the inner ring of the flame tube as the support surface and the top end face of the inner ring of the flame tube as the pressing surface. A positioning pin support is provided on the base plate close to the outer periphery of the inner ring of the flame tube. An angular hole is provided on the side wall of the inner ring of the flame tube, through which the positioning pin passes. The flame tube is fixed on the positioning pin support by the positioning pin.

[0008] Furthermore, the locating pin is tapered.

[0009] Furthermore, a guide pin is provided on the bottom, which connects the base plate and the positioning plate.

[0010] Furthermore, the base plate is also provided with a second support block close to the inner side of the outer ring.

[0011] Furthermore, the support surface can be equipped with adjusting shims.

[0012] Furthermore, a protective pad is provided on the top periphery of the outer ring of the flame tube.

[0013] The machining method for the mounting hole of the vortex generator at the head of an aero-engine flame tube includes the following steps: S1 laser cutting is used for rough cutting of the vortex generator mounting hole at the head of the flame tube to remove excess material; S2, while measuring the relevant dimensions, increases the angle θ between the angular hole and the head vortex mounting hole, so that the head vortex mounting hole and the angular hole are on the same interface.

[0014] S3 CNC milling and finishing, CNC milling and finishing includes clamping and alignment and machining vibration control. The flame tube is positioned with the inner ring circle of the flame tube as the center, the bottom of the inner ring with the strongest local rigidity of the flame tube is used as the support surface, and the top end face of the inner ring is selected as the clamping surface. S3.1 Clamping and Alignment S3.1.1 Place the fixture on the worktable. When placing it, the angular holes should be positioned close to the angular coordinate axis according to the programmed coordinate system. S3.1.2 Align the fixture mandrel and set the machine tool workpiece coordinate system X0, Y0; S3.1.3 Place the flame tube on the clamp; S3.1.4 Use a dial indicator to align the head face of the flame tube. The runout should not exceed 0.2mm. If this is not met, insert shims of varying thicknesses into the support surface for adjustment. S3.1.5 Slide the positioning plate over the mandrel and position it in place within the inner ring of the flame tube; S3.1.6 Screw in the nut, and at the same time, press 2-3 dial indicators onto the head of the flame tube and set the dial indicators to zero; S3.1.7 Slowly tighten the nut while observing the dial indicator reading. The change should not exceed 0.05mm. If not, adjust the support surface as needed. S3.1.8 Use the tool setting block to complete the Z-axis zeroing and set the machine tool workpiece coordinate system Z0; S3.1.9 Use a dial indicator to align the head vortex generator mounting hole, obtain the current center coordinates of the head vortex generator mounting hole, calculate the angle α with the X-axis in the coordinate system, and then substitute the included angle θ obtained in step S2 for compensation to obtain the coordinate rotation angle α+θ, and set it in the program to complete the accurate alignment of the angular reference. S3.2 Machining Vibration Control S3.2.1 Wrap a protective pad several times around the outer ring of the flame tube. When wrapping, do not apply force. A dial indicator can be used to check for any deformation during wrapping. S3.2.2 Adds the use of locating pins to fix the flame tube to the clamp; S3.2.3 Select a small-diameter tool with a diameter of less than 12mm, and choose a machining mode with medium-low speed, small depth of cut, and low feed rate for cutting parameters.

[0015] Furthermore, the tool diameter is 8mm, the cutting speed is 56m / min, the depth of cut is 0.2mm, and the feed per tooth is 0.02mm.

[0016] Furthermore, during laser cutting, a margin of 0.2-0.5mm is left on each side. Furthermore, the tolerance of the inner annular diameter of the flame tube is guaranteed to be between (0, -0.045), and the tolerance of the bottom plate diameter is guaranteed to be between (+0.01, 0).

[0017] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention adopts a mechanical processing method that has always been considered infeasible, replacing the laser cutting method to process the mounting hole of the vortex generator at the head of the flame tube, and the shape and position accuracy fully meet the requirements, and the processing qualification rate is increased from zero under the original laser cutting method to 100% qualified.

[0018] (2) This invention provides a feasible clamping method for thin-walled flame tube components without effective support.

[0019] (3) The present invention provides a precise alignment method for the alignment of sidewall corner holes, which is highly accurate and efficient.

[0020] (4) The present invention provides a machining mode with low to medium speed, small depth of cut, and low feed rate for machining hollow and suspended flame tubes, as well as optimized cutting parameters and related auxiliary vibration reduction measures, resulting in low machining vibration and a 100% pass rate; (5) This invention can be used to process thin-walled parts with structures similar to flame tubes, with significant effects, high processing efficiency, low cost, and significant socio-economic benefits. Attached Figure Description Figure 1 A schematic diagram of the clamping structure for machining the flame tube of an existing aero-engine; Figure 2 A schematic diagram of the fixture for machining the mounting hole of the vortex generator at the head of an aero-engine flame tube; Figure 3 A schematic diagram of the machining fixture structure for the mounting hole of the vortex generator at the head of an aero-engine flame tube; Figure 4 A three-dimensional structural diagram of the flame tube of an aero-engine; Figure 5 (A schematic diagram of the structure of an aircraft engine flame tube). Figure 6 A schematic diagram of the machining fixture structure for the mounting hole of the vortex generator at the head of an aero-engine flame tube; Figure 7 A schematic diagram of the locating pin for the mounting hole of the vortex generator at the head of an aero-engine flame tube.

[0021] Wherein: 1-Hex socket screw; 2-Base plate; 3-Support block one; 4-Protective pad; 5-Positioning plate; 6-Mandrel; 7-Nut; 8-Positioning pin; 9-Positioning pin support; 10-Support block two; 11-Guide pin; 12-Inner ring; 13-Outer ring; A-Inner ring circle of flame tube; B-Head face of flame tube; C-Angular hole; D-Supporting surface; E-Clamping surface; I-Head vortex generator mounting hole. Detailed Implementation

[0022] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application; however, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the invention. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in this invention can be purchased commercially or prepared by existing methods.

[0023] Example 1 Please see Figures 2 to 7 An embodiment of the present invention provides a machining fixture for the mounting hole of the vortex generator at the head of an aero-engine flame tube, comprising a base plate, a mandrel perpendicular to the base plate having a center on the base plate, the mandrel being fixed to the base plate by an internal hexagon screw, the mandrel passing through the flame tube, the mandrel being fixed to the base plate by an internal hexagon screw, the flame tube comprising an inner ring and an outer ring, the bottom of the inner ring of the flame tube serving as a support surface, and the top end face of the inner ring of the flame tube serving as a pressing surface, the support surface being able to be adjusted by adding shims to the support block for alignment.

[0024] The mandrel is fitted with a positioning plate and a nut that press and position the top end face of the inner ring of the positioning flame tube. A guide pin is provided on the bottom, which serves as a guide for the positioning plate to ensure that the positioning plate is in a horizontal state. The guide pin connects the bottom plate and the positioning plate.

[0025] The base plate is provided with a support block 1 that supports the bottom of the inner ring of the flame tube.

[0026] The base plate is provided with a positioning pin support close to the outer perimeter of the inner ring of the flame tube. An angular hole is provided on the side wall of the inner ring of the flame tube, through which the positioning pin passes. The flame tube is fixed to the positioning pin support by the positioning pin to prevent deformation due to compression. The use of the positioning pin further secures the flame tube to the fixture, preventing slight movement of the part due to vibration. The positioning pin is tapered, which avoids ineffective positioning caused by excessive deviation of the positioning hole.

[0027] A protective pad is provided on the top periphery of the outer ring of the flame tube. The protective pad can be made of soft rubber. The soft rubber band is wrapped around the outer ring of the flame tube several times, preferably 3-5 times. When wrapping, no force is applied. A dial indicator can be used to check the head to see if there is any deformation during wrapping.

[0028] Example 2 Please see Figures 2 to 7 An embodiment of the present invention provides a machining fixture for the mounting hole of the vortex generator at the head of an aero-engine flame tube, comprising a base plate, a mandrel perpendicular to the base plate having a center on the base plate, the mandrel being fixed to the base plate by an internal hexagon screw, the mandrel passing through the flame tube and being fixed to the base plate by an internal hexagon screw, the flame tube comprising an inner ring and an outer ring, the bottom of the inner ring of the flame tube serving as a support surface, and the top end face of the inner ring of the flame tube serving as a pressing surface, the support surface may be fitted with an adjusting shim for alignment.

[0029] The mandrel is fitted with a positioning plate and a nut that press and position the top end face of the inner ring of the flame tube. A guide pin is provided on the bottom, and the guide pin connects the bottom plate and the positioning plate.

[0030] The base plate is provided with a support block 1 that supports the bottom of the inner ring of the flame tube.

[0031] The base plate is provided with a positioning pin support close to the outer perimeter of the inner ring of the flame tube. An angular hole is provided on the side wall of the inner ring of the flame tube, through which the positioning pin passes. The flame tube is fixed to the positioning pin support by the positioning pin to prevent deformation due to compression. The use of the positioning pin further secures the flame tube to the fixture, preventing slight movement of the part due to vibration. The positioning pin is tapered, which avoids ineffective positioning caused by excessive deviation of the positioning hole.

[0032] A protective pad is provided on the top periphery of the outer ring of the flame tube. The protective pad can be made of soft rubber. The soft rubber band is wrapped around the outer ring of the flame tube several times, preferably 3-5 times. When wrapping, no force is applied. A dial indicator can be used to check the head to see if there is any deformation during wrapping.

[0033] Furthermore, the base plate is also provided with a second support block close to the inner side of the outer ring, which is used to assist in supporting the inner and outer rings of the flame tube and reduce processing vibration.

[0034] Example 3 Please see Figures 2 to 7 The present invention provides an embodiment of a method for machining mounting holes for vortex generators at the head of an aero-engine flame tube, comprising the following steps: S1 laser cutting is used for rough cutting of the mounting hole of the vortex generator at the head of the flame tube to remove excess material. In order to ensure the final hole diameter requirement is met during CNC milling, it is necessary to control the vibration of the part during milling. Therefore, while meeting the processing requirements, the excess material should be milled as little as possible. For this reason, during laser cutting, a single-sided allowance of 0.2-0.5mm is left. In this case, a 0.5mm allowance is selected. To solve the problem of accurate angular alignment during CNC milling, after laser processing, while measuring the relevant dimensions, an angle θ is added between the angular hole and the head vortex mounting hole for adjustment during subsequent CNC milling finishing. The head vortex mounting hole and the angular hole are on the same interface.

[0035] S3 CNC milling and finishing includes clamping and alignment, and machining vibration control. The flame tube is positioned with the inner ring circle as the center, and the bottom of the inner ring, where the local rigidity of the flame tube is the strongest, is used as the support surface. The top end face of the inner ring is selected as the clamping surface to prevent clamping deformation. The diameter tolerance of the inner ring circle of the flame tube is guaranteed to be between (0, -0.045), and the diameter tolerance of the base plate is guaranteed to be between (+0.01, 0). S3.1 Clamping and Alignment S3.1.1 Place the fixture on the worktable. When placing it, position the angular hole close to the coordinate axis according to the programming coordinate system. (When the angular hole is placed on the machine tool, its position is uncertain. It may be in any position of 360°. However, when programming, the angular hole is placed on the x-axis or y-axis of the programming coordinate system. Therefore, when placing it, try to place it as close as possible to the programmed state.) S3.1.2 Align the fixture mandrel, and set the machine tool workpiece coordinate system X0 and Y0 with the mandrel as the center; S3.1.3 Place the flame tube on the clamp; S3.1.4 Use a dial indicator to align the head face of the flame tube. The runout should not exceed 0.2mm. If this is not met, insert shims of varying thicknesses into the support surface for adjustment. S3.1.5 Slide the positioning plate over the mandrel and position it in place within the inner ring of the flame tube; S3.1.6 Screw in the nut, and at the same time, press 2-3 dial indicators onto the head of the flame tube and set the dial indicators to zero; S3.1.7 Slowly tighten the nut while observing the dial indicator reading. The change should not exceed 0.05mm. If not, adjust the support surface as needed. S3.1.8 Use the tool setting block to complete the Z-axis zeroing and set the machine tool workpiece coordinate system Z0; S3.1.9 Use a dial indicator to align the head vortex generator mounting hole, obtain the current center coordinates of the head vortex generator mounting hole, calculate the angle α with the X-axis in the coordinate system, and then substitute the included angle θ obtained in step S2 for compensation to obtain the coordinate rotation angle α+θ, and set it in the program to complete the accurate alignment of the angular reference. S3.2 Machining Vibration Control S3.2.1 Use a soft rubber band to wrap around the outer ring of the flame tube several times, preferably 3-5 times. When wrapping, do not apply force. A dial indicator can be used to check the head for any deformation during wrapping. S3.2.2 Add the use of locating pins to fix the flame tube to the fixture to prevent slight movement of the parts due to vibration; S3.2.3 Select a small-diameter tool with a diameter of less than 12mm. In this case, an 8mm tool is preferred. For cutting parameters, select a machining mode with medium-low speed, small depth of cut, and low feed rate. In this case, the preferred cutting speed is 56m / min, depth of cut is 0.2mm, and feed per tooth is 0.02mm.

[0036] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for machining the mounting hole for the vortex generator at the head of an aero-engine flame tube, characterized in that, The processing method is based on a processing fixture, which includes a base plate. A mandrel perpendicular to the base plate is located at the center of the base plate. The mandrel passes through the flame tube. A positioning plate and a nut for pressing and positioning the flame tube are fitted on the mandrel. The flame tube includes an inner ring and an outer ring. A support block one supporting the bottom of the inner ring of the flame tube is provided on the base plate, with the bottom of the inner ring of the flame tube as the support surface and the top end face of the inner ring of the flame tube as the pressing surface. A positioning pin support is provided on the base plate close to the outer periphery of the inner ring of the flame tube. An angular hole is provided on the side wall of the inner ring of the flame tube, through which the positioning pin passes. The flame tube is fixed on the positioning pin support by the positioning pin. A guide pin is provided on the base plate, which connects the base plate and the positioning plate. A support block two close to the inner side of the outer ring of the flame tube is also provided on the base plate. The processing steps include: S1 laser cutting is used for rough cutting of the vortex generator mounting hole at the head of the flame tube to remove excess material; The angle θ between the S2 metering angular hole and the head vortex mounting hole is such that the head vortex mounting hole and the angular hole are on the same interface. S3 CNC milling and finishing includes clamping and alignment and machining vibration control. The flame tube is positioned with the inner ring as the center, the bottom of the inner ring as the support surface, and the top end face of the inner ring as the clamping surface. The clamping, alignment, and machining vibration control steps include: S3.1 Clamping and Alignment S3.1.1 Place the fixture on the worktable. When placing it, the angular holes should be positioned close to the angular coordinate axis according to the programmed coordinate system. S3.1.2 Align the fixture mandrel and set the X0 and Y0 coordinates of the machine tool workpiece coordinate system; S3.1.3 Place the flame tube on the clamp; S3.1.4 Use a dial indicator to align the surface where the vortex generator mounting hole is located at the head of the flame tube. The runout should not exceed 0.2mm. If this is not met, insert shims of different thicknesses into the support surface for adjustment. S3.1.5 Slide the positioning plate over the mandrel and position it in place within the inner ring of the flame tube; S3.1.6 Screw in the nut, and at the same time, press 2-3 dial indicators onto the head of the flame tube and set the dial indicators to zero; S3.1.7 Slowly tighten the nut while observing the dial indicator reading. The change should not exceed 0.05mm. If not, adjust the support surface as needed. S3.1.8 Use the tool setting block to complete the Z-axis zeroing and set the Z0 of the machine tool workpiece coordinate system; S3.1.9 Use a dial indicator to align the head vortex generator mounting hole and obtain the center coordinates of the current head vortex generator mounting hole. Calculate the angle α between the center of the current head vortex generator mounting hole and the X-axis in the coordinate system. Then, substitute the included angle θ obtained in step S2 into the compensation to obtain the coordinate rotation angle α+θ, and set it in the program to complete the accurate alignment of the angular reference. S3.2 Machining Vibration Control S3.2.1 Wrap a protective pad around the outer ring of the flame tube several times. When wrapping, do not apply force. Use a dial indicator to check for any deformation on the outer ring of the flame tube. S3.2.2 Secure the flame tube to the clamp using locating pins; S3.2.3 Select a small-diameter tool with a diameter of 8mm and perform machining with cutting parameters of 56m / min cutting speed, 0.2mm depth of cut, and 0.02mm feed per tooth.

2. The method for machining the mounting hole of the vortex generator at the head of the aero-engine flame tube according to claim 1, characterized in that, The locating pin is tapered.

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