A method for machining a precision optical mounting window

Abstract

The present application belongs to the field of aerospace machinery precision manufacturing technology, and particularly relates to a precision optical mounting window machining method, which is based on tooling design, optical mounting window machining and optical mounting window profile rapid detection to optimize the precision optical mounting window machining. When filling the gypsum, the gypsum filling amount at the top of the tooling adopts the minimization principle; in the trial cutting correction process, the re-clamping is configured with a step of calibrating the machining origin of the part. The present application can solve the problems of easy deformation, low machining qualification rate and dependence on three-coordinate equipment for precision profile detection in the precision optical mounting window machining, and has high application and promotion value.

Description

Technical Field

[0001] This invention belongs to the field of precision manufacturing technology for aerospace machinery, and specifically relates to a machining method for a precision optical mounting window. Background Technology

[0002] As new fighter jets place increasingly higher demands on weight reduction and stealth performance, aircraft structural components are also developing towards lightweighting and high precision. Lightweighting inevitably leads to a large amount of material removal, reduced component rigidity, and increased susceptibility to deformation during machining, resulting in out-of-tolerance parts. Meanwhile, the increasing precision requirements of components, particularly for mounting windows of optical components, significantly increase the difficulty of machining and inspection.

[0003] Taking a certain type of product as an example, the structural components involved in stealth performance are typical large-sized, weakly rigid skeleton parts. These parts are highly susceptible to deformation during clamping and machining, and are made of difficult-to-machine cast titanium alloy. Tool wear is severe during machining, making it difficult to guarantee accuracy. Multiple optical mounting windows are symmetrically distributed on the upper part of the part. Because these windows need to provide mounting and positioning references for the optical components, their contour accuracy requirements are -0.03mm to +0.02mm. Affected by residual stress, machining deformation, clamping and positioning, the contour accuracy pass rate for these optical mounting windows is extremely low. Furthermore, the contour accuracy of the part needs to be inspected using a coordinate measuring machine (CMM), which is highly dependent on CMM equipment, lengthening the part's machining cycle and causing long equipment wait times, hindering the promotion of the machining method.

[0004] Therefore, there is an urgent need for a stable and precise machining and rapid inspection method for optical mounting windows to ensure stable and efficient machining and forming of optical mounting windows, guarantee the machining qualification rate, and shorten the machining cycle of structural components. Summary of the Invention

[0005] In view of this, the present invention provides a machining method for precision optical mounting windows, which can solve the problems of easy deformation during machining of precision optical mounting windows, low machining pass rate, and reliance on coordinate measuring machines for precision contour detection, and has high application and promotion value.

[0006] The technical solution of this invention is as follows:

[0007] A machining method for a precision optical mounting window, comprising:

[0008] Residual stress removal: During the processing of the mounting window, a heat treatment process for the entire part is inserted in a timely manner, and the heat treatment parameters are controlled to release the residual stress of the part;

[0009] Tooling design: An auxiliary support tooling is provided to support the part during machining; the tooling is based on aluminum alloy and filled with plaster on top, and the part is in contact with the plaster when supported;

[0010] Optical mounting window processing: A dovetail cutter is set to machine the part from the outer cavity, and the window contour is processed in one pass; a allowance value is set during the material removal process before the final finishing of the part to realize trial cutting and correction;

[0011] Rapid inspection of the profile of an optical mounting window: During the trial cutting and correction process, a fixture is used to quickly inspect the parts. The fixture is used to completely simulate the mating state between the optical parts and the parts. During the rapid inspection, the profile accuracy is converted into dimensional accuracy based on the inspection results of the fixture.

[0012] Among them: when filling with plaster, the amount of plaster filling on the top of the tooling is minimized; during the trial cutting and correction process, a step is set up to calibrate the machining origin of the part when it is clamped again.

[0013] Furthermore, the specific methods for residual stress removal are as follows:

[0014] First, the parts are machined to a margin of no more than 2mm. Then, titanium alloy vacuum annealing heat treatment is performed to relieve stress. The heat treatment parameters are: heating temperature 400~600℃, holding time 2~3h, working vacuum degree ≤8×10 -2 Pa;

[0015] Afterwards, except for the optical mounting window and features with precision requirements, which leave a 0.3-0.6mm allowance, the rest of the machining is carried out to the dimensions. The titanium alloy is then subjected to high and low temperature aging heat treatment. The heat treatment parameters are: low temperature -40~-60℃ for 1~2h, high temperature 90~110℃ for 1~2h, and the cycle is repeated at least 3 times, first at low temperature and then at high temperature.

[0016] Furthermore, the tooling is a contour tooling designed according to the part structure, and the specific design process of the tooling is as follows:

[0017] The slope angle of the upper surface support surface of the tooling is designed according to the angle between the ribs between the windows and the mounting reference surface, so that the distance between the upper surface support surface and the supported surface of the part is consistent; the upper surface support surface of the tooling is evenly distributed with stepped structure to improve the bonding between the plaster and the tooling.

[0018] The bottom surface of the fixture is set with an oblong through hole, through which screws are connected to the worktable. The fixture adjusts the distance between the upper surface support surface and the part by linearly moving on the worktable.

[0019] Furthermore, the specific method for filling the tooling with plaster includes the following steps:

[0020] S101: Clean the tooling and parts before filling with plaster, and stir the plaster evenly;

[0021] S102: The moving fixture ensures that the distance between the ribs on the upper surface of the fixture and the window is less than 20mm;

[0022] S103: Plaster is evenly filled at least two locations on the upper surface support surface. The width of the plaster support area is limited to within 12mm. The filling length of a single plaster filling point is 0.2 to 0.3 times the length of the rib. No plaster is filled in the processing area of ​​the optical mounting window.

[0023] S104: After the plaster has dried completely, begin machining the parts.

[0024] Furthermore, the processing method for the optical mounting window is as follows:

[0025] The dovetail cutter is designed to mimic the shape of the optical mounting window, with the angle of the dovetail cutter matching the angle of the mounting window. Different specifications of dovetail cutters are selected according to different processing steps. Large-diameter dovetail cutters with a diameter of 18-22mm are used for machining with a large allowance, while small-diameter dovetail cutters with a diameter of no more than 10mm are used for final finishing. When setting the tool, the middle part of the dovetail cutter is considered for machining the optical mounting window. When clamping the tool, the tool extension should be kept as short as possible while ensuring normal machining.

[0026] The optical mounting window profile is machined to size using at least three CNC milling operations. The first CNC milling operation leaves a 0.3-0.6mm allowance, and then the allowance is measured using a coordinate measuring machine. After that, the CNC program allowance is adjusted according to the measurement result, and the part is machined to the upper tolerance dimension. The coordinate measuring machine is measured again, and the CNC program is adjusted according to the measurement result. The second measurement result is compared, and only the edges where the tolerance is exceeded are finely repaired. The edges that do not exceed the tolerance are not processed again until the profile is qualified.

[0027] The machining parameters for using a dovetail cutter with a diameter of no more than 10mm are: spindle speed 1500~2000r / min, feed rate 250~300mm / min.

[0028] Furthermore, the specific method for origin calibration includes the following steps:

[0029] S201: Position the part on the fixture by using the two pin holes at the front and back of the part, and tighten the screw through the screw hole to clamp the part in the fixture.

[0030] S202: Remove the two pins, align the pin holes at the front and rear, and calibrate the machining coordinate system;

[0031] S203: Use a dial indicator to locate the pin hole, set the center of the pin hole as the origin of the machine tool machining program, and perform machining on the part.

[0032] Furthermore, the method for detecting the profile of the optical mounting window is as follows:

[0033] Based on the structure of the optical components being fitted, a precision fixture for the optical mounting window is designed. The fixture completely simulates the fit between the optical components and the metal components.

[0034] After installing the precision gauge behind the window, the profile tolerance is converted into the height difference of the gauge beyond the outer surface of the metal part by using trigonometric functions based on the angle value of the window.

[0035] The beneficial effects of this invention are:

[0036] 1. This invention provides a complete processing method for optical windows of large-size weak rigid skeleton parts, which can stably inspect and process the parts, improving the consistency and pass rate of part processing.

[0037] 2. This invention designs a set of rigid-flexible auxiliary support fixtures, clarifies the principles of plaster filling, and standardizes the usage of the fixtures.

[0038] 3. This invention specifies the machining method and origin correction method for optical mounting windows, providing ideas for the machining of similar structural features.

[0039] 4. This invention designs a rapid window detection method that can quickly detect optical windows without using a coordinate measuring machine, reducing the reliance on coordinate measuring machines for part processing and shortening the processing cycle. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 A schematic diagram of the aluminum alloy base for the auxiliary support tooling that combines rigidity and flexibility;

[0042] Figure 2 This is a schematic diagram of the structure of a portion of the part in the embodiment;

[0043] Figure 3 This is a schematic diagram of a contour-following dovetail knife;

[0044] Figure 4 A schematic diagram of the principle of a precision fixture for optical mounting windows;

[0045] Among them: 1. Upper surface support surface of tooling; 2. Stepped structure; 3. Waist-shaped through hole; 4. Plaster filling position; 5. Pin hole at the front end of the part (one at the rear end is not shown); 6. Screw hole; 7. Dovetail cutter angle; 8. Precision gauge; 9. Metal part; 10. Glue filling gap; 11. Bottom surface of precision gauge; 12. Outer surface of part; 13. Height difference. Detailed Implementation

[0046] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0047] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0048] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0049] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this disclosure. The illustrations only show the components related to this disclosure and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0050] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0051] In one embodiment of the present invention, a machining method for a precision optical mounting window is provided, comprising:

[0052] Residual stress removal: During the processing of the mounting window, a heat treatment process for the entire part is inserted in a timely manner, and the heat treatment parameters are controlled to release the residual stress of the part;

[0053] Tooling design: An auxiliary support tooling is provided to support the part during machining; the tooling is based on aluminum alloy and filled with plaster on top, and the part is in contact with the plaster when supported;

[0054] Optical mounting window processing: A dovetail cutter is set to machine the part from the outer cavity, and the window contour is processed in one pass; a allowance value is set during the material removal process before the final finishing of the part to realize trial cutting and correction;

[0055] Rapid inspection of the profile of an optical mounting window: During the trial cutting and correction process, a fixture is used to quickly inspect the parts. The fixture is used to completely simulate the mating state between the optical parts and the parts. During the rapid inspection, the profile accuracy is converted into dimensional accuracy based on the inspection results of the fixture.

[0056] Among them: when filling with plaster, the amount of plaster filling on the top of the tooling is minimized; during the trial cutting and correction process, a step is set up to calibrate the machining origin of the part when it is clamped again.

[0057] In this embodiment, the specific method for residual stress removal is as follows:

[0058] First, the parts are machined to a margin of no more than 2mm. Then, titanium alloy vacuum annealing heat treatment is performed to relieve stress. The heat treatment parameters are: heating temperature 400~600℃, holding time 2~3h, working vacuum degree ≤8×10 -2 Pa;

[0059] Afterwards, except for the optical mounting window and features with precision requirements, which leave a 0.3-0.6mm allowance, the rest of the machining is carried out to the dimensions. The titanium alloy is then subjected to high and low temperature aging heat treatment. The heat treatment parameters are: low temperature -40~-60℃ for 1~2h, high temperature 90~110℃ for 1~2h, and the cycle is repeated at least 3 times, first at low temperature and then at high temperature.

[0060] In this embodiment, the tooling is a contour tooling designed according to the structure of the part. The specific design process of the tooling is as follows:

[0061] The slope angle of the upper surface support surface of the tooling is designed according to the angle between the ribs between the windows and the mounting reference surface, so that the distance between the upper surface support surface and the supported surface of the part is consistent; the upper surface support surface of the tooling is evenly distributed with stepped structure to improve the bonding between the plaster and the tooling.

[0062] The bottom surface of the fixture is set with an oblong through hole, through which screws are connected to the worktable. The fixture adjusts the distance between the upper surface support surface and the part by linearly moving on the worktable.

[0063] In this embodiment, the specific method for filling the tooling with plaster includes the following steps:

[0064] S101: Clean the tooling and parts before filling with plaster, and stir the plaster evenly;

[0065] S102: The moving fixture ensures that the distance between the ribs on the upper surface of the fixture and the window is less than 20mm;

[0066] S103: Plaster is evenly filled at least two locations on the upper surface support surface. The width of the plaster support area is limited to within 12mm. The filling length of a single plaster filling point is 0.2-0.3 times the length of the rib. No plaster is filled in the processing area of ​​the optical mounting window.

[0067] S104: After the plaster has dried completely, begin machining the parts.

[0068] In this embodiment, the processing method of the optical mounting window is as follows:

[0069] The dovetail cutter is designed to mimic the shape of the optical mounting window, with the angle of the dovetail cutter matching the angle of the mounting window. Different specifications of dovetail cutters are selected according to different processing steps. Large-diameter dovetail cutters with a diameter of 18-22mm are used for machining with a large allowance, while small-diameter dovetail cutters with a diameter of no more than 10mm are used for final finishing. When setting the tool, the middle part of the dovetail cutter is considered for machining the optical mounting window. When clamping the tool, the tool extension should be kept as short as possible while ensuring normal machining.

[0070] The optical mounting window profile is machined to size using at least three CNC milling operations. The first CNC milling operation leaves a 0.3-0.6mm allowance, and then the allowance is measured using a coordinate measuring machine. After that, the CNC program allowance is adjusted according to the measurement result, and the part is machined to the upper tolerance dimension. The coordinate measuring machine is measured again, and the CNC program is adjusted according to the measurement result. The second measurement result is compared, and only the edges where the tolerance is exceeded are finely repaired. The edges that do not exceed the tolerance are not processed again until the profile is qualified.

[0071] The machining parameters for using a dovetail cutter with a diameter of no more than 10mm are: spindle speed 1500r / min~2000r / min, feed rate 250mm / min~300mm / min.

[0072] In this embodiment, the specific method for origin calibration includes the following steps:

[0073] S201: Position the part on the fixture by using the two pin holes at the front and back of the part, and tighten the screw through the screw hole to clamp the part in the fixture.

[0074] S202: Remove the two pins, align the pin holes at the front and rear, and calibrate the machining coordinate system;

[0075] S203: Use a dial indicator to locate the pin hole, set the center of the pin hole as the origin of the machine tool machining program, and perform machining on the part.

[0076] In this embodiment, the method for detecting the contour of the optical mounting window is as follows:

[0077] Based on the structure of the optical components being fitted, a precision fixture for the optical mounting window is designed. The fixture completely simulates the fit between the optical components and the metal components.

[0078] After installing the precision gauge behind the window, the profile tolerance is converted into the height difference of the gauge beyond the outer surface of the metal part by using trigonometric functions based on the angle value of the window.

[0079] In this embodiment, refer to Figures 1-4 A machining method for a precision optical mounting window is provided, comprising:

[0080] Step 1: Residual Stress Removal: During material removal, residual stress is continuously released from the parts, causing deformation. A heat treatment process is inserted at appropriate times during processing, and the heat treatment parameters are controlled to release the residual stress.

[0081] Step 2: Tooling Design: Design a rigid-flexible auxiliary support tooling with an aluminum alloy base, topped with plaster to connect with the part, supporting the part during machining and improving the overall rigidity of the part during processing.

[0082] Step 3: Plaster filling. The plaster filling of the tooling top follows the principle of minimization, strictly controlling the amount of plaster used to minimize deformation caused by plaster expansion.

[0083] Step 4: Machining the optical mounting window. A dovetail cutter is designed to machine the window contour from the outer cavity in a single pass, ensuring toolpath continuity for easy subsequent adjustments. A allowance value is designed, and the allowance for the optical mounting window is measured. The measurement results are analyzed, and out-of-tolerance areas are located and fine-tuned.

[0084] Step 5: Calibration of the machining origin. After the second clamping, the origin is calibrated to ensure the consistency of the program origin.

[0085] Step 6: Rapid inspection of the optical mounting window profile. Specialized inspection fixtures are used on-site to rapidly inspect the parts. High-precision fixtures are designed based on the mating optical components to completely simulate the mating state between the optical components and structural parts, converting profile accuracy into dimensional accuracy for convenient on-site rapid inspection.

[0086] Specific methods for residual stress removal:

[0087] Due to limitations in casting processes, residual stress is inevitably introduced into the blank during casting. As this residual stress is released during machining, it can cause deformation of the part, affecting its dimensions and form and position tolerances. In the example, the titanium alloy casting blank typically has a 5-7mm allowance. The release of residual stress during material removal will inevitably cause deformation of the part, necessitating the elimination of residual stress during machining.

[0088] 1) First, machine the parts to leave a 1mm allowance, and then perform vacuum annealing heat treatment on titanium alloy to relieve stress. Heat treatment parameters: heating temperature 400~600℃, holding time 2~3h, working vacuum degree ≤8×10-2Pa.

[0089] 2) Then, except for the optical mounting window and some features with precision requirements (leaving a 0.5mm allowance), the rest are dimensionally corrected, and the titanium alloy undergoes high and low temperature aging heat treatment. Heat treatment parameters: low temperature treatment at -50℃ for 1~2 hours, high temperature treatment at 100℃ for 1~2 hours, first low temperature then high temperature, for a total of 3 cycles. Residual stress in the parts is removed before the optical mounting window is precision machined.

[0090] The specific process of tooling design:

[0091] The fixture is a contour-following fixture designed based on the part's structure. The angle of the upper surface support surface 1 of the fixture is designed according to the angle between the ribs between the windows and the mounting reference surface. The upper surface support surface of the part has evenly distributed stepped structures 2 to improve the bonding between the plaster and the fixture. The bottom surface of the fixture is set with an oblong through hole 3, through which screws are connected to the worktable. The distance between the oblong edge of the fixture and the part is adjusted by moving the fixture back and forth.

[0092] Specific methods for filling with plaster:

[0093] In actual processing, the deformation of parts caused by plaster expansion has a significant impact on the final profile of the mounting surface of optical components. Therefore, the plaster filling is minimized to reduce deformation caused by plaster expansion. The specific operating method is as follows:

[0094] 1) Before filling with plaster, the tooling and parts should be cleaned, and the plaster should be stirred evenly.

[0095] 2) The moving fixture ensures that the distance between the support surface 1 on the upper surface of the fixture and the window is 15mm.

[0096] 3) Plaster should be used to fill the gaps between the upper, middle, and lower three points (4 positions) of the ribs between the windows. The width of the plaster support area should be limited to within 10mm, and the length of each plaster filling point should be about 1 / 5 of the rib length. Plaster filling is strictly prohibited in the processed areas of optical installation windows.

[0097] 4) After the plaster has dried for about 2 hours, start machining the parts.

[0098] Optical mounting window processing method:

[0099] 1) Design a contour-following dovetail cutter based on the shape of the optical mounting window. The dovetail cutter angle 7 must strictly match the angle of the mounting window. Select different specifications of dovetail cutters according to different machining processes. When the allowance is large, use a large-diameter dovetail cutter of about 20mm to improve cutting efficiency. During final finishing, to reduce cutting force, the tool diameter must be strictly controlled not to exceed 10mm. Considering the stability of the tool during cutting, the middle part of the dovetail cutter should be used for machining the optical mounting window during tool setting. When clamping the tool, the tool extension should be kept as short as possible while ensuring normal machining.

[0100] 2) The outline of the optical mounting window needs to be machined to the required dimensions using at least three CNC milling operations. The first CNC milling operation leaves a 0.2mm allowance, which is then measured using a coordinate measuring machine (CMM) to obtain the allowance measurement result. Based on the measurement result, the CNC program allowance is adjusted, and the part is machined to the required dimension. CMM measurement is then performed again. The CNC program is strictly adjusted according to the CMM measurement result. Only the edges where the tolerance is exceeded are further refined; edges that are within the tolerance are not further processed until the outline meets the requirements.

[0101] The machining is performed using a dovetail cutter with a cutting diameter of no more than 10mm. The machining parameters are: spindle speed 1500~2000r / min, feed rate 250~300mm / min.

[0102] Machining origin calibration method:

[0103] The profile of an optical window requires multiple processing and measurement steps to ensure its pass rate. During these multiple processing and measurement cycles, secondary clamping of the part is unavoidable. Due to pin positioning errors and machine tool repeatability, inaccurate secondary clamping can prevent the part from being machined to the correct position during fine finishing based on the measurement results. Therefore, calibrating the machining origin is a crucial step in ensuring the pass rate of the optical mounting window profile. Origin calibration mainly includes the following steps:

[0104] 1) Position the part on the fixture by using the two pin holes 5 at the front and rear, and tighten the screw through the screw hole 6 to clamp the part.

[0105] 2) Remove the two pins, align the pin holes at both ends with a dial indicator, and calibrate the C-axis;

[0106] 3) Use a dial indicator to locate the pin hole, and set the center of the pin hole as the program origin to start machining.

[0107] Rapid detection method for the contour of optical mounting windows:

[0108] The profile of an optical window requires multiple processing and measurement steps to ensure a high pass rate, making part processing overly reliant on coordinate measuring machines (CMMs). When CMMs face heavy workloads or when some manufacturers lack precision CMMs, part processing is limited. The principle of a rapid detection method for the profile of an optical mounting window is as follows:

[0109] 1) Based on the structure of the optical components to be used, design a precision fixture for the optical mounting window. The fixture completely simulates the mating state between the optical components and the metal components.

[0110] 2) Due to the glue-filled gap 10 between the optical and metal parts, after the precision fixture 8 mates with the metal part 9, a height difference 13 will occur between the bottom surface 11 of the precision fixture and the outer surface 12 of the part. Additionally, changes in the profile affect the gap between the fixture and the part, also causing changes in the height difference 13. Based on the window angle value, the profile tolerance can be converted into the height difference 13 of the fixture exceeding the outer surface of the metal part using simple trigonometric functions. This converts the form and position tolerance requiring coordinate measuring machine (CMM) measurement into a dimensional tolerance that can be measured using a dial indicator.

[0111] A preferred embodiment: precision boring and correcting the process holes on other process shanks, and correcting the machining coordinate system based on the process holes.

[0112] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method of machining a precision optical mounting window, characterized by, The application relates to a machining method for an optical mounting window of a titanium alloy integral part. The method comprises the following steps: After the machining of the optical mounting window and the features with precision requirements is completed, the remaining part is machined to the size, and high-temperature aging heat treatment is carried out on the titanium alloy; the heat treatment parameters are as follows: low temperature -40 to -60 DEG C, 1 to 2 h of heat preservation, high temperature 90 to 110 DEG C, 1 to 2 h of heat preservation, and the low-temperature aging heat treatment is followed by the high-temperature aging heat treatment, and the total cycle is not less than 3 times; First, the parts are processed to leave a margin of no more than 2mm, and then titanium alloy vacuum annealing heat treatment is carried out to remove the stress of the parts, and the heat treatment parameters are as follows: heating temperature 400~600℃, holding time 2~3h, working vacuum degree ≤8×10 -2 Pa; An auxiliary supporting tool is designed to support the part during machining; The auxiliary supporting tool is made of aluminum alloy as a base and filled with gypsum at the top, and the part is in contact with the gypsum during supporting; The auxiliary supporting tool is a profiling tool designed according to the structure of the part, and the specific process of the design of the auxiliary supporting tool is as follows: The angle of the inclined surface of the upper surface supporting surface of the auxiliary supporting tool is designed according to the angle between the rib between the windows and the mounting reference surface, so that the upper surface supporting surface is consistent with the supported surface of the part; The upper surface supporting surface of the auxiliary supporting tool is uniformly distributed in a stepped structure, which is used for improving the combination degree between the gypsum and the auxiliary supporting tool; The bottom surface of the auxiliary supporting tool is designed as a waist-shaped through hole, a screw passes through the waist-shaped through hole and is connected with a workbench, and the auxiliary supporting tool is adjusted to be linearly moved on the workbench to adjust the distance between the upper surface supporting surface and the part; The optical mounting window is machined by setting a profiling dovetail tool to machine the part from the outer cavity, and the window profile degree is machined by one-time feeding; a margin value is set during the previous material removal machining of the final finishing machining of the part to realize trial cutting correction; During the trial cutting correction process, a testing tool is used to quickly detect the part, the testing tool is used to completely simulate the cooperation state of the optical part and the part, and during the quick detection process, the profile accuracy is converted into the size accuracy based on the detection result of the testing tool; after the testing tool is installed on the window, the profile tolerance is converted into the height difference of the testing tool exceeding the outer surface of the metal part according to the angle value of the window through the trigonometric function conversion; Wherein: when the gypsum is filled, the gypsum filling amount at the top of the auxiliary supporting tool adopts the minimization principle; during the trial cutting correction process, the machining origin of the part is calibrated again when the part is clamped again. The specific method for filling the gypsum on the auxiliary supporting tool comprises the following steps:

2. The method of claim 1, wherein, S101: the auxiliary supporting tool and the part are cleaned before the gypsum is filled, and the gypsum is uniformly stirred; S102: the auxiliary supporting tool is moved to ensure that the distance between the upper surface supporting surface of the auxiliary supporting tool and the rib between the windows is less than 20 mm; S103: the gypsum is uniformly filled at least two positions of the upper surface supporting surface, the width of the gypsum supporting area is limited to be within 12 mm, the filling length of a single gypsum filling point is 0.2 to 0.3 times the length of the rib, and the optical mounting window machining position is not filled with gypsum; S104: after the gypsum is dried, the part is machined. The machining method for the optical mounting window is as follows:

3. The method of claim 2, wherein, ​ According to the shape of the optical mounting window, a profiled dovetail tool is designed, and the angle of the dovetail tool is consistent with the angle of the mounting window; different specifications of the dovetail tool are selected according to different processing procedures, a large-diameter dovetail tool with a diameter of 18-22 mm is used in large excess processing, and a small-diameter dovetail tool with a diameter of not more than 10 mm is used in final finishing; when the tool is set, the middle part of the dovetail tool is used to process the optical mounting window, and the tool is as long as possible under the condition of ensuring normal processing when the tool is clamped; The contour of the optical mounting window is machined by at least three numerical control milling processes; the first numerical control milling process leaves a 0.3-0.6 mm excess, and then the measurement result of the excess is obtained based on the three-coordinate measuring instrument; then the numerical control program excess is adjusted according to the measurement result, the part is machined to the upper limit size, the three-coordinate measurement is performed again, and the numerical control program is adjusted according to the three-coordinate measurement result; only the edge where the out-of-tolerance position is located is refined compared with the second measurement result, and the edge that is not out of tolerance is not processed, until the contour is qualified; The machining parameters of the profiled dovetail tool with a tool diameter of not more than 10 mm are as follows: spindle speed 1500-2000 r / min, feed speed 250-300 mm / min.

4. The method of claim 3, wherein, The specific method of origin correction includes the following steps: S201: Place the part on the tool by positioning the front and rear pin holes of the part, tighten the screw through the screw hole to clamp the part; S202: Take out the two pins, find the front and rear pin holes, and calibrate the machining coordinate system; S203: Find the pin hole by the watch, set the pin hole center as the origin of the machine tool machining program, and execute the machining of the part.

5. The method of claim 4, wherein, The detection method of the contour of the optical mounting window is as follows: According to the structure of the matched optical part, a precision gauge for the optical mounting window is designed, which completely simulates the matching state of the optical part and the metal part; After installing the precision gauge behind the window, the contour tolerance is converted into the height difference of the gauge exceeding the outer surface of the metal part according to the angle value of the window through the trigonometric function conversion.

Images