Method for processing thin-walled weakly rigid flat casings

Abstract

The application discloses a kind of thin-wall weak rigid flat casing processing methods, comprising the following steps: S1, part is fixed on fixture, then gradually processes the preliminary profile of the group of precision holes on the part mounting edge by drilling, burying hole and rough boring, and the rough boring processing amount is controlled within the set range;S2, part is taken out from fixture, part is fixed again by pressing, and in the process of pressing, the layered step-by-step pressing fixation of part is carried out by using layered uniform distribution pressing method and torque wrench, and torque wrench is controlled within the set torque, while the maximum deformation of part is checked in real time when pressing plate is pressed each time, to ensure that the deformation of part is controlled within the set runout;S3, the complete profile of the group of precision holes on the part mounting edge is gradually processed by using semi-fine boring, fine boring and reaming, and the reaming processing amount is controlled to be a set value;Compared with prior art, the position of precision hole on the part mounting edge is accurate and reliable, and the processing qualified rate of part is high.

Description

Technical Field

[0001] This invention relates to the field of casing processing technology, and in particular, to a method for processing a thin-walled, weakly rigid, flat casing. Background Technology

[0002] In a certain type of aero-engine, the intermediate casing is made of high-temperature alloys such as GH625 and GH3030, which are difficult to machine. The radial span of the parts is much greater than their axial length. The overall shape is a flat, bowl-like cover with a wall thickness ranging from only 2.5 to 3.75 mm. The front and rear mounting edges are connected by a conical, arc-shaped thin wall that is suspended in mid-air. The mounting bosses are unevenly welded circumferentially to the curved, thin-walled sections on the casing's sloping sides. Therefore, this intermediate casing is a typical thin-walled, weakly rigid, flat structure. Furthermore, since this intermediate casing belongs to the gas generator unit of this type of aero-engine, its front and rear mounting edges are precisely assembled with the centrifugal impeller cover and turbine casing, respectively. Therefore, the technical requirements and dimensions of the precision holes on its mounting edges are very high.

[0003] However, when using fixtures to clamp and fix the intermediate housing, the large end face of the part is usually supported, and multiple pressure plates are evenly distributed around the circumference for clamping. However, due to the flatness control issues of the support surface itself, unevenness always occurs when the part is supported on its entire surface (even if the flatness requirement is within acceptable limits). Therefore, during the clamping process, the part will always experience clamping stress deformation. In addition, the existing machining methods are drilling, rough boring, finish boring, and reaming. Due to the thin-walled, weak-rigidity structure and low plasticity and high hardness of the part, in order to ensure the finish boring allowance, the machining allowance during rough boring is too large. This leads to rapid wear of the rough boring tool, large cutting force during rough boring, and severe dulling of the tool after wear, which further increases the cutting force during rough boring. Furthermore, the large reaming allowance left after finish boring results in a large cutting force during reaming. After the part is machined, its stress deformation will be converted into an accumulation on the precision hole size and technical requirements of the part end face after the part deforms and springs back, which can easily cause out-of-tolerance. Moreover, since precision hole machining is a semi-closed cutting process, the high cutting heat and chips that are difficult to break are difficult to remove away from the tool tip in time, resulting in more severe tool wear. In addition, the axial force of drilling is large, and the radial force of boring will be generated, which makes the tool prone to large bending deformation, thus affecting the machining accuracy of the part. At the same time, abnormal tool wear and tool breakage are also prone to occur during the machining process, resulting in large cutting stress deformation of the part and low pass rate. Summary of the Invention

[0004] This invention provides a method for machining a thin-walled, weakly rigid, flat casing to solve the technical problems of compression stress deformation and cutting stress deformation, unstable machining of precision holes on the mounting edge, and low yield rate in the existing intermediate casing machining process.

[0005] According to one aspect of the present invention, a method for machining a thin-walled, weakly rigid, flat casing is provided, comprising the following steps: S1, clamping and fixing the part onto a fixture, and then gradually machining the preliminary outline of the precision hole group on the mounting edge of the part using drilling, backfilling, and rough boring, while controlling the rough boring machining amount within a set range; S2, removing the part from the fixture, re-clamping and fixing the part, and during the clamping and fixing process, using a layered uniform clamping method in conjunction with a torque wrench to gradually clamp and fix the part in layers, while controlling the torque wrench within a set torque, and simultaneously checking the maximum deformation of the part each time the pressure plate clamps, ensuring that the deformation of the part is controlled within a set runout amount; S3, gradually machining the complete outline of the precision hole group on the mounting edge of the part using semi-fine boring, fine boring, and reaming, while controlling the reaming machining amount to a set value.

[0006] As a further improvement to the above technical solution:

[0007] Furthermore, the specific steps for using a layered, evenly distributed clamping method to gradually clamp and fix the parts are as follows: The parts are clamped in four layers. The first layer involves manually tightening multiple pressure plate nuts in sequence. The second layer involves using a torque wrench with a torque of 6 N·m-7 N·m to tighten multiple pressure plate nuts in sequence. The third layer involves using a torque wrench with a torque of 7 N·m-8 N·m to tighten multiple pressure plate nuts in sequence. The fourth layer involves using a torque wrench with a torque of 8 N·m-9 N·m to tighten multiple pressure plate nuts in sequence.

[0008] Furthermore, the tightening sequence of the nuts on each pressure plate is the same.

[0009] Furthermore, the parts are clamped at three points, with each pressure plate clamped sequentially in a clockwise or counterclockwise direction; or the parts are clamped at four points, with each pressure plate clamped sequentially in a cross-shaped pattern; or the parts are clamped at six points, with each pressure plate clamped sequentially in an intermittent cross-shaped star pattern.

[0010] Furthermore, the torque is set to 6 N·m-9 N·m, and the runout is set to 0.005.

[0011] Furthermore, the setting range is 0.5mm-0.7mm; and / or the setting value is 0.02mm.

[0012] Furthermore, during the machining process, severely worn rough boring tools, fine boring tools, and reamers are reground and replaced.

[0013] Furthermore, the machining parameters for drilling are: rotational speed 500 r / min, feed rate 20 mm / min; the machining parameters for buried hole drilling are: rotational speed 600 r / min, feed rate 10 mm / min, depth of cut 0.5 mm; the machining parameters for rough boring are: rotational speed 800 r / min, feed rate 15 mm / min, depth of cut 0.6 mm; the machining parameters for semi-finish boring are: rotational speed 1000 r / min, feed rate 15 mm / min, depth of cut 0.23 mm; the machining parameters for finish boring are: rotational speed 1000 r / min, feed rate 12 mm / min, depth of cut 0.15 mm; and the machining parameters for reaming are: rotational speed 500 r / min, feed rate 18 mm / min, depth of cut 0.02 mm.

[0014] Furthermore, the maximum deformation of the parts is checked in real time each time the pressure plate is tightened using a dial indicator. If the deformation of the parts exceeds the set runout, the support and clamping points of the pressure plate are adjusted, and the tightening and deformation checks are performed again until the deformation of the parts is controlled within the set runout.

[0015] Furthermore, by controlling the machining amount of semi-finish boring, the machining amount of rough boring is controlled within a set range, and the machining amount of reaming is controlled within a set value.

[0016] The present invention has the following beneficial effects:

[0017] The present invention discloses a method for machining a thin-walled, weakly rigid, flat casing. The part is clamped and fixed onto a fixture. Then, drilling, backfilling, and rough boring are used to progressively machine the preliminary outline of the precision hole group on the mounting edge of the part. Backfilling and rough boring are used to correct the position of the precision holes after drilling, reducing positional deviations. The rough boring machining amount is controlled within a set range to avoid excessive feed, while the rough boring cutting force is controlled within a reasonable range. The part is then removed from the fixture and re-clamped and fixed. During the clamping process, a layered, evenly distributed clamping method is used in conjunction with a torque wrench to progressively clamp and fix the part in layers. The torque wrench is controlled within a set torque, and the maximum deformation of the part is monitored in real time during each clamping operation to ensure that the deformation is controlled within a set runout. This transforms a single clamping operation into multiple clamping operations, reducing the clamping force on the part each time it is clamped, resulting in relatively uniform force distribution during clamping and maximizing efficiency. This method minimizes the clamping stress deformation of parts and, through precise control of the clamping force, keeps the deformation within a suitable range to avoid repeated adjustments due to excessive deformation, thereby improving the clamping and fixing efficiency of parts. It employs semi-finish boring, finish boring, and reaming to progressively machine the complete outline of the precision hole group on the mounting edge of the part, controlling the reaming machining amount to a set value. This ensures the quality of precision hole machining while minimizing reaming cutting force. Compared to existing technologies, this solution reduces cutting stress deformation after drilling by using buried holes, reduces cutting stress deformation during rough boring by using semi-finish boring, and minimizes cutting stress deformation to the greatest extent by precisely controlling the rough boring and reaming machining amounts. Furthermore, it minimizes clamping stress deformation to the greatest extent by using secondary clamping and layered clamping and fixing of the parts, ensuring accurate and reliable positioning of the precision holes on the mounting edge of the part. This results in a high part machining qualification rate, strong practicality, and suitability for widespread promotion and application.

[0018] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 This is a flowchart illustrating the steps of a preferred embodiment of the processing method for a thin-walled, weakly rigid, flat casing of the present invention.

[0021] Figure 2 This is a schematic diagram of the structure of the thin-walled, weakly rigid, flat casing in the preferred embodiment of the present invention. Detailed Implementation

[0022] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0023] like Figure 1 and Figure 2 As shown, the machining method for a thin-walled, weakly rigid, flat casing in this embodiment includes the following steps: S1, clamping and fixing the part onto a fixture, and then using drilling, backing holes, and rough boring to gradually machine the preliminary outline of the precision hole group on the mounting edge of the part, while controlling the rough boring machining amount within a set range; S2, removing the part from the fixture, re-clamping and fixing the part, and during the clamping and fixing process, using a layered uniform clamping method in conjunction with a torque wrench to gradually clamp and fix the part in layers, while controlling the torque wrench within a set torque, and simultaneously checking the maximum deformation of the part each time the pressure plate clamps, ensuring that the deformation of the part is controlled within a set runout amount; S3, using semi-fine boring, fine boring, and reaming to gradually machine the complete outline of the precision hole group on the mounting edge of the part, and controlling the reaming machining amount to a set value.

[0024] like Figure 1 and Figure 2As shown, specifically, the thin-walled, weakly rigid, flat casing machining method of the present invention involves clamping and fixing the part onto a fixture, then gradually machining the preliminary outline of the precision hole group on the mounting edge of the part using drilling, backfilling, and rough boring. Backfilling and rough boring correct the position of the precision holes after drilling, reducing positional deviations, and controlling the rough boring machining amount within a set range to avoid excessive feed. Simultaneously, the rough boring cutting force is controlled within a reasonable range. The part is then removed from the fixture and re-clamped and fixed. During the clamping process, a layered, evenly distributed clamping method is used in conjunction with a torque wrench to gradually clamp and fix the part in layers, with the torque wrench controlled within a set torque. Simultaneously, the maximum deformation of the part is checked in real time during each clamping operation to ensure that the deformation is controlled within a set runout. This transforms a single clamping operation into multiple clamping operations, reducing the clamping force on the part each time it is pressed, and ensuring relatively uniform force distribution during clamping. This method minimizes the deformation caused by clamping stress on parts and, through precise control of the clamping force, keeps the deformation within a suitable range to avoid repeated adjustments due to excessive deformation, thereby improving the clamping and fixing efficiency of parts. It employs semi-finish boring, finish boring, and reaming to progressively machine the complete outline of the precision hole group on the mounting edge of the part, controlling the reaming machining amount to a set value. This ensures the quality of precision hole machining while minimizing reaming cutting force. Compared to existing technologies, this solution reduces cutting stress deformation after drilling by using buried holes, reduces cutting stress deformation during rough boring by using semi-finish boring, and minimizes cutting stress deformation by precisely controlling the rough boring and reaming machining amounts. Furthermore, it minimizes clamping stress deformation through secondary clamping and layered clamping, ensuring accurate and reliable positioning of the precision holes on the mounting edge of the part. This results in a high part machining qualification rate, strong practicality, and suitability for widespread promotion and application.

[0025] It should be understood that a precision hole group refers to all the precision holes on the mounting edge of a part.

[0026] It should be understood that buried holes and boring are crucial in the machining process. They can correct the hole position and the cutting allowance in a timely manner, and prevent the hole from being eccentric, which would lead to uneven circumferential hole machining allowance and uneven cutting force. This would result in greater local force and cause the part to deviate from its position. Therefore, increasing the number of buried holes and precisely controlling the boring machining amount can greatly improve the pass rate of the machined parts.

[0027] It should be understood that, by Figure 2 As shown, due to the structure of the outer ring bevel boss and pipe joint, it is impossible to change the multi-point clamping to full-surface clamping; while changing the full-surface support to multi-point support requires modification of the fixture, but the workload of fixture modification is large and the cycle is long, and the production organization of changing the fixture is risky, so neither is advisable; in addition, under the current process conditions, it is not possible to completely eliminate the clamping stress deformation when the part is clamped.

[0028] It should be understood that the processing method in this embodiment is a step-by-step precision hole group processing method. First, the precision hole group on the mounting edge of the part is drilled, then the precision hole group on the mounting edge of the part is buried, then the precision hole group on the mounting edge of the part is rough bored, then the precision hole group on the mounting edge of the part is semi-finish bored, then the precision hole group on the mounting edge of the part is finish bored, and finally the precision hole group on the mounting edge of the part is reamed. Compared with processing precision holes one by one, this method can greatly reduce the cumulative deformation of the part and improve the processing quality.

[0029] It should be understood that the existing tool path for parts consists of rough boring, finish boring, and reaming. In this tool path, in order to ensure the finish boring allowance, the machining allowance during rough boring is too large, which leads to rapid wear of the rough boring tool, large rough boring cutting force, and severe tool dulling after wear, further increasing the rough boring cutting force. In addition, the reaming allowance reserved after finish boring is large, which makes the cutting force during reaming of the part large. Therefore, in this embodiment, by adding semi-finish boring, the amount of rough boring and reaming machining can be reduced, thereby reducing the rough boring cutting force and the reaming cutting force.

[0030] In this embodiment, the specific steps of using a layered, evenly distributed clamping method to gradually clamp and fix the parts are as follows: The parts are clamped in four layers. The first layer involves manually tightening multiple pressure plate nuts sequentially. The second layer involves using a torque wrench with a torque of 6 N·m-7 N·m to tighten multiple pressure plate nuts sequentially. The third layer involves using a torque wrench with a torque of 7 N·m-8 N·m to tighten multiple pressure plate nuts sequentially. The fourth layer involves using a torque wrench with a torque of 8 N·m-9 N·m to tighten multiple pressure plate nuts sequentially. Specifically, by clamping in layers, warping deformation of the parts can be avoided due to uneven stress on that area compared to other parts after one pressure plate is tightened. Furthermore, by gradually increasing the torque of the torque wrench in each layer, the stress on the parts is ensured to be relatively regular and uniform, greatly reducing the clamping stress deformation of the parts.

[0031] In this embodiment, the tightening sequence of the nuts on each layer of pressure plates is the same. Specifically, by ensuring that the tightening sequence of the nuts on each layer of pressure plates is the same, the stress on the parts is relatively regular and uniform, further reducing the deformation of the parts due to the clamping stress.

[0032] In this embodiment, the part is clamped at three points, with each pressure plate being clamped sequentially in a clockwise or counterclockwise direction. Specifically, when the part is clamped at three points, clamping each pressure plate sequentially in a clockwise or counterclockwise direction ensures that the pressure on a single layer of the part is relatively uniform, thereby reducing the clamping deformation stress on the part.

[0033] In another embodiment, the part is clamped at four points, with each pressure plate being clamped sequentially in a cross-shaped pattern. Specifically, when the part is clamped at four points, using a cross-shaped pattern to clamp each pressure plate sequentially ensures that the pressure on a single layer of the part is relatively uniform, thereby reducing the deformation of the part due to clamping stress.

[0034] In another embodiment, the part is clamped at six points, and each pressure plate is clamped sequentially using a staggered star-shaped pattern. Specifically, when the part is clamped at six points, a cross-shaped pattern is used to clamp each pressure plate sequentially, which can ensure that the pressure on a single layer of part is relatively uniform, thereby reducing the deformation of the part due to clamping stress.

[0035] In this embodiment, the set torque is 6 N·m-9 N·m, and the set runout is 0.005. Specifically, when the designed torque is within 6 N·m-9 N·m, the runout during part clamping can be controlled within 0.005, ensuring the part is clamped and preventing loosening. When the set torque is less than 6 N·m, the part will still loosen after clamping. When the set torque is greater than 9 N·m, the runout during part clamping is greater than 0.005, requiring re-clamping and inspection. In this embodiment, the set range is 0.5 mm-0.7 mm. Specifically, when the set range is 0.5 mm-0.7 mm, the machining efficiency and rough boring cutting force are appropriate; when the set range is less than 0.5 mm, the machining efficiency is low; when the set range is greater than 0.8 mm, the rough boring cutting force is too large.

[0036] In this embodiment, the set value is 0.02mm. Specifically, when the set value is 0.02mm, the part pass rate is high and the reaming cutting force is appropriate; when the set value is less than 0.02mm, the part pass rate is low; when the set value is greater than 0.02mm, the reaming cutting force is large.

[0037] In this embodiment, during the machining process, severely worn rough boring tools, finish boring tools, and reamers are reflashed and replaced. Specifically, by reflashing and replacing severely worn rough boring tools, finish boring tools, and reamers, the cutting edges of these tools are kept sharp, thereby reducing the cutting force during machining and thus reducing the cutting stress deformation of the parts.

[0038] In this embodiment, in step S2, the machining parameters for drilling are: rotational speed 500 r / min, feed rate 20 mm / min; the machining parameters for buried hole are: rotational speed 600 r / min, feed rate 10 mm / min, depth of cut 0.5 mm; the machining parameters for rough boring are: rotational speed 800 r / min, feed rate 15 mm / min, depth of cut 0.6 mm; the machining parameters for semi-finish boring are: rotational speed 1000 r / min, feed rate 15 mm / min, depth of cut 0.23 mm; the machining parameters for finish boring are: rotational speed 1000 r / min, feed rate 12 mm / min, depth of cut 0.15 mm; and the machining parameters for reaming are: tool rotational speed 500 r / min, feed rate 18 mm / min, depth of cut 0.02 mm. Specifically, by precisely controlling the machining parameters, the cutting force at each step can be controlled to ensure that the deformation of the part during clamping is within a controllable range. This can significantly improve the process stability and quality reliability of precision hole machining. In addition, except for reaming, the rotational speed is gradually increased, the feed rate is gradually decreased, and the depth of cut is gradually reduced to reduce cutting force, reduce tool wear, and improve machining quality.

[0039] In this embodiment, a dial indicator method is used to check the maximum deformation of the part in real time each time the pressure plate is tightened. If the deformation exceeds the set runout, the support and clamping points of the pressure plate are adjusted, and the tightening and deformation checks are repeated until the deformation is controlled within the set runout. Specifically, during the layered tightening and fixing process, the maximum deformation of the part is checked in real time each time the pressure plate tightens the part, and the deformation is compared with the set runout to determine the next pressure block to tighten, or to adjust and re-tighten and check, so as to ensure that the deformation of the part meets the processing accuracy requirements to the greatest extent and improve the processing qualification rate of the part.

[0040] In this embodiment, the machining amount of semi-finish boring is controlled to keep the rough boring amount within a set range and the reaming amount within a set value. Specifically, by increasing the reduction in rough boring and reaming amounts into the semi-finish boring amount, the cutting forces of rough boring and reaming are reduced, keeping the rough boring amount within a set range and the reaming amount within a set value. Furthermore, after semi-finish boring is completed, finish boring can be used to eliminate any part deformation that may occur during semi-finish boring, thereby improving the part's machining pass rate.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for machining a thin-walled, weakly rigid, flat casing, characterized in that, Includes the following steps: S1, clamp and fix the part on the fixture, and then use drilling, backing holes and rough boring to gradually process the preliminary outline of the precision hole group on the mounting edge of the part, and control the rough boring amount within the set range; S2, remove the part from the fixture, re-clamp and fix the part, and during the clamping process, use a layered uniform clamping method with a torque wrench to gradually clamp and fix the part in layers, and control the torque wrench within the set torque, while checking the maximum deformation of the part each time the pressure plate clamps, to ensure that the deformation of the part is controlled within the set runout. The specific steps for using a layered, evenly distributed clamping method to gradually clamp and fix the parts are as follows: The parts are clamped in four layers. The first layer involves manually tightening multiple pressure plate nuts in sequence. The second layer involves using a torque wrench with a torque of 6 N·m-7 N·m to tighten multiple pressure plate nuts in sequence. The third layer involves using a torque wrench with a torque of 7 N·m-8 N·m to tighten multiple pressure plate nuts in sequence. The fourth layer involves using a torque wrench with a torque of 8 N·m-9 N·m to tighten multiple pressure plate nuts in sequence. The maximum deformation of the parts is checked in real time with a dial indicator during each clamping of the pressure plate. If the deformation exceeds the set runout, the support and clamping points of the pressure plate are adjusted, and the clamping and deformation checks are repeated until the deformation is controlled within the set runout. S3 uses semi-finish boring, fine boring and reaming to gradually machine the complete outline of the precision hole group on the mounting edge of the part, and controls the reaming machining amount to the set value; The machining method is a step-by-step precision hole group machining method. First, the precision hole group on the mounting edge of the part is drilled, then the precision hole group on the mounting edge of the part is buried, then the precision hole group on the mounting edge of the part is rough bored, then the precision hole group on the mounting edge of the part is semi-finish bored, then the precision hole group on the mounting edge of the part is finish bored, and finally the precision hole group on the mounting edge of the part is reamed. The machining parameters for drilling are: 500 r / min rotation speed, 20 mm / min feed rate; the machining parameters for buried hole drilling are: 600 r / min rotation speed, 10 mm / min feed rate, and 0.5 mm depth of cut; the machining parameters for rough boring are: 800 r / min rotation speed, 15 mm / min feed rate, and 0.6 mm depth of cut; the machining parameters for semi-finish boring are: 1000 r / min rotation speed, 15 mm / min feed rate, and 0.23 mm depth of cut; the machining parameters for finish boring are: 1000 r / min rotation speed, 12 mm / min feed rate, and 0.15 mm depth of cut; and the machining parameters for reaming are: 500 r / min tool rotation speed, 18 mm / min feed rate, and 0.02 mm depth of cut.

2. The method for machining a thin-walled, weakly rigid, flat casing according to claim 1, characterized in that, The tightening sequence of the nuts on each pressure plate is the same.

3. The method for machining a thin-walled, weakly rigid, flat casing according to claim 1, characterized in that, The part is clamped at three points, by clamping each pressure plate sequentially clockwise or counterclockwise; or The part is clamped at four points, using a cross-shaped clamping pattern to sequentially clamp each pressure plate; or The parts are clamped at six points, and each pressure plate is clamped in a staggered star-shaped pattern.

4. The method for machining a thin-walled, weakly rigid, flat casing according to any one of claims 1-3, characterized in that, The torque is set to 6 Nm - 9 Nm, and the runout is set to 0.

005.

5. The method for machining a thin-walled, weakly rigid, flat casing according to any one of claims 1-3, characterized in that, The setting range is 0.5mm-0.7mm; and / or The setting value is 0.02mm.

6. The method for machining a thin-walled, weakly rigid, flat casing according to any one of claims 1-3, characterized in that, During the machining process, severely worn rough boring tools, fine boring tools, and reamers are re-sharpened and replaced.

7. The method for machining a thin-walled, weakly rigid, flat casing according to any one of claims 1-3, characterized in that, By controlling the machining amount of semi-finish boring, the machining amount of rough boring is controlled within a set range, and the machining amount of reaming is controlled within a set value.

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