Machining method of thin-wall lining

Abstract

The invention relates to the field of machining, in particular to a thin-wall lining machining method which comprises the following steps that S1, a thin-wall lining blank is prepared, the total length and an inner hole of the thin-wall lining blank are roughly machined, a first intermediate product is obtained, and machining allowance is reserved; s2, the two end faces of the first intermediate product serve as positioning references, the outer circle of the first intermediate product is shaped, and a second intermediate product is obtained; s3, the second intermediate product is subjected to heat preservation for 4-6 h at the temperature of 200-300 DEG C, when the furnace is cooled to 100 DEG C or below, the second intermediate product is taken out of the furnace and air-cooled to the room temperature, and a third intermediate product is obtained; s4, the two end faces of the third intermediate product are subjected to flat grinding, and a fourth intermediate product is obtained; and S5, the outer circle of the fourth intermediate product is ground to the target size through an outer circle grinding machine, an inner hole of the fourth intermediate product is subjected to finish machining to the target size through a vertical machining center or a vertical numerical control milling machine, and the thin-wall lining is obtained. And the production requirements of large thin-wall linings can be directly met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of machining, in particular to a machining method of a thin-wall bushing. BACKGROUND

[0002] Under the background of increasing application demand of large thin-wall bushings, the specifications of thin-wall bushings continue to develop towards large size. The plastic mandrel internal expansion type machining method adopted in the prior art has defects of large tooling volume, heavy weight and high manufacturing cost; and with the increase of the bushing specifications, the machining precision of this machining method decreases significantly, which is difficult to meet the quality requirements of the products, resulting in that it cannot adapt to the production requirements of large thin-wall bushings, so it is urgent to innovate and optimize the related machining process. SUMMARY

[0003] The purpose of the present application is to provide a machining method of a thin-wall bushing, which can directly meet the production requirements of large thin-wall bushings.

[0004] In order to achieve the above purpose, the technical scheme selected by the present application is as follows: The present application discloses a machining method of a thin-wall bushing, which comprises the following steps: S1, preparing a thin-wall bushing blank, rough machining the total length and inner hole of the thin-wall bushing blank to obtain a first intermediate product, and reserving a machining allowance; S2, shaping the outer circle of the first intermediate product on a press machine with the two end faces of the first intermediate product as positioning reference to obtain a second intermediate product; S3, keeping the second intermediate product at a temperature of 200-300 DEG C for 4-6 hours, furnace cooling to 100 DEG C or below, and air cooling to room temperature after taking out of the furnace to obtain a third intermediate product; S4, grinding the two end faces of the third intermediate product to make the flatness of a single end face and the parallelism between the two end faces reach the preset requirements, and the total length reach the target size to obtain a fourth intermediate product; S5, grinding the outer circle of the fourth intermediate product to the target size by using an outer circle grinding machine, and precisely machining the inner hole of the fourth intermediate product to the target size by using a vertical machining center or a vertical numerical control milling machine to obtain a thin-wall bushing.

[0005] Further, the step S1 of preparing a thin-wall bushing blank comprises: starting a centrifugal casting device to make the mold reach a preset rotating speed, synchronously starting the induction heater, and pouring the alloy liquid into the rotating mold at a constant speed; maintaining the rotating speed of the mold until the alloy liquid completely solidifies to obtain a thin-wall bushing blank; and the induction heater is a hollow spiral structure obtained by winding metal wires.

[0006] Further, the shaping mold for shaping treatment in the step S2 has an inner circle diameter of 0.98-0.995 times the outer circle diameter of the first intermediate product.

[0007] Further, the preset requirements in the step S4 include that the flatness of the single end face is not greater than 0.02 mm, and the parallelism between the two end faces is not greater than 0.03 mm.

[0008] Further, the step S5 includes the following steps: clamping and fixing the fourth intermediate product by using a clamp, then fixing the clamp with the fourth intermediate product on the cylindrical grinding machine, positioning by using the center hole, setting the cylindrical grinding process parameters, and precisely grinding the outer circle of the fourth intermediate product to the target size.

[0009] Further, the clamp includes a base plate, a pressing plate and a stud, one end of the base plate is provided with a first protrusion matched with the first end opening of the fourth intermediate product in a gap, the middle part of the base plate is provided with a first through hole; one end of the pressing plate is provided with a second protrusion matched with the second end opening of the fourth intermediate product in a gap, the middle part of the pressing plate is provided with a second through hole; the stud is connected with the nut through the first through hole and the second through hole at both ends, and the relative position between the base plate and the pressing plate is adjusted by the nut; the outer circle diameter of the first protrusion is 0.2-0.5 mm smaller than the inner diameter of the first end opening of the fourth intermediate product; the outer circle diameter of the second protrusion is 0.2-0.5 mm smaller than the inner diameter of the second end opening of the fourth intermediate product.

[0010] Further, the step S5 includes the following steps: when the perpendicularity between the spindle and the workbench of the vertical machining center or the vertical numerical control milling machine is ≤ the target value of the bushing wall thickness difference × 0.8 ÷ the bushing length, the fourth intermediate product is clamped and fixed on the workbench of the vertical machining center or the vertical numerical control milling machine, the inner hole finishing process parameters are set, and the inner hole of the fourth intermediate product is finished to the target size; when the perpendicularity between the spindle and the workbench of the vertical machining center or the vertical numerical control milling machine is > the target value of the bushing wall thickness difference × 0.8 ÷ the bushing length, a supporting plate is provided, the clamping end face of the fourth intermediate product and the supporting face of the supporting plate are milled by using the same fine milling equipment, the fourth intermediate product is clamped and fixed on the supporting face of the plate, the clamping end face of the fourth intermediate product is matched with the supporting face of the plate in contact, the inner hole finishing process parameters are set, and the inner hole of the fourth intermediate product is finished to the target size.

[0011] The present application has the following unexpected beneficial effects: 1. The outer circle shaping process in step S2 of the processing method provided by this invention, using the two end faces as positioning references, can correct irregular deformation or dimensional deviations of the outer circle after rough machining, making the outer circle contour more regular, providing uniform machining allowance for subsequent outer circle grinding, and reducing the risk of wall thickness difference in the final product. The heat preservation and furnace cooling process in step S3, i.e., heat setting treatment, can effectively release residual stress generated by previous processing, avoid dimensional deformation caused by stress release during subsequent processing or product use, and significantly improve the long-term dimensional stability of the product. The end face flat grinding in step S4 can accurately control the flatness and parallelism of the end face, which not only establishes a stable positioning reference for subsequent outer circle grinding and inner hole finishing, but also avoids the accumulation of form and position tolerances caused by reference deviation, further ensuring the overall accuracy of the product. Step S5 uses a combination of cylindrical grinding machine and vertical machining center / vertical CNC milling machine to replace the traditionally relied-upon high-precision special equipment, such as large vertical turning and grinding equipment. The equipment selection is more flexible. Furthermore, since the internal hole is precision machined using a vertical machining center / vertical CNC milling machine, there is no need to design special fixtures for internal hole machining, which greatly reduces tooling investment costs and can better ensure machining quality.

[0012] 2. The processing method described in this invention addresses the pain points of thin-walled bushings being prone to deformation and difficult to control in terms of precision through a combination of shaping, stress relief, and benchmark finishing. It has stronger adaptability and eliminates the need for frequent adjustments to the core process framework due to changes in product specifications, thereby indirectly reducing process adjustment costs. Attached Figure Description

[0013] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.

[0014] Figure 1 This is a schematic flowchart illustrating the processing method of the thin-walled bushing provided in an embodiment of this application.

[0015] Figure 2 This is a schematic diagram of the fixture provided in an embodiment of this application.

[0016] In the diagram, 1-substrate, 2-pressure plate, 3-double-ended stud, 4-nut, 5-washer, 6-fourth intermediate product. Detailed Implementation

[0017] Other advantages and benefits of the present application will become apparent to those skilled in the art upon consideration of the disclosure or can be learned by practice of the application. The application can be realized and achieved by means as various as those set forth herein in the written description and claims claims hereof. It is therefore to be understood that such preferred embodiments are merely illustrative of the present application and are not intended to limit the scope of the present application as defined by the appended claims.

[0018] In one embodiment, referring to Figure 1 As shown in the drawings, the application discloses a processing method of a thin-wall bushing, comprising the following steps: S1, preparing a thin-wall bushing blank, rough machining the total length and inner hole of the thin-wall bushing blank to obtain a first intermediate product, and reserving a machining allowance.

[0019] The excess metal on the surface of the thin-wall bushing blank is removed through rough machining, and the blank is initially processed into the first intermediate product with the total length and the inner hole, thereby completing the transition from the disordered blank to the ordered semi-finished product.

[0020] Exemplarily, each of the two end faces of the first intermediate product in the length direction reserves a machining allowance of 1-2 mm on a single side, and the inner hole wall reserves a machining allowance of 1-2 mm on a single side.

[0021] S2, taking the two end faces of the first intermediate product as positioning reference, performing shaping treatment on the outer circle of the first intermediate product on a press to obtain a second intermediate product.

[0022] The two end faces of the first intermediate product are selected as the positioning reference, because the end face is the core reference of the subsequent multiple processes, positioning in advance with the end face can reduce the reference conversion error and ensure that the shaping direction is consistent with the subsequent machining reference.

[0023] The direct effect of the outer circle shaping is to correct the irregular deformation (such as ovality, local bulging) or size out-of-tolerance of the outer circle after rough machining, so that the outer circle contour is closer to the design shape, and finally provides uniform machining allowance for the outer circle grinding process of S5. If the outer circle allowance is uneven, wall thickness difference is prone to occur after grinding, and this step can reduce this risk from the source.

[0024] S3, keeping the second intermediate product at a temperature of 200-300°C for 4-6h, furnace cooling to 100°C or below, and air cooling to room temperature after taking out of the furnace to obtain a third intermediate product.

[0025] The pressure shaping of step S2 belongs to plastic deformation processing, which will generate residual stress in the bushing. If not eliminated, stress release during subsequent finishing or product use process will cause secondary deformation of the bushing, such as bending, reducing diameter, and destroying precision.

[0026] By keeping the bushing at low temperature and 200-300℃ for a long time, the metal atoms inside the bushing slowly move, gradually releasing residual stress. Subsequent furnace cooling to 100℃ or below is to avoid new thermal stress generated by rapid cooling, and finally make the internal stress of the third intermediate product at a low level, significantly improving the dimensional stability of the product during long-term use.

[0027] S4, the two end faces of the third intermediate product are ground flat, so that the flatness of a single end face and the parallelism between the two end faces meet the preset requirements, and the total length reaches the target size, obtaining the fourth intermediate product.

[0028] The precision of the end face machined in step S1 is low and cannot be directly used as a positioning reference for S5. Through the flat grinding process, the flatness of the end face and the parallelism between the two end faces are controlled within the preset requirements, providing a high-precision reference surface for the external grinding and internal hole finishing of S5.

[0029] The total length of the third intermediate product is machined to the target size, which not only completes the precision closed loop in the length direction of the bushing, but also avoids the size matching disorder of the subsequent internal hole / external circle machining caused by the total length out of tolerance.

[0030] S5, the external circle of the fourth intermediate product is ground to the target size using an external grinding machine, and the internal hole of the fourth intermediate product is precisely machined to the target size using a vertical machining center or a vertical CNC milling machine, obtaining a thin-walled bushing.

[0031] The external circle of the fourth intermediate product is machined to the target size using the high-precision grinding capability of the external grinding machine, while ensuring the cylindricity and roundness of the external circle and other form and position tolerances. Compared with traditional rough machining equipment, the grinding machine can more accurately control the surface precision of the external circle, matching the precision requirements of the thin-walled bushing.

[0032] A vertical machining center or a vertical CNC milling machine is used instead of traditional high-precision special equipment such as large vertical turning and grinding equipment. The device selection is more flexible, and there is no need to configure special equipment for a single product, reducing equipment investment costs. Moreover, since the internal hole is precisely machined using a vertical machining center / vertical CNC milling machine, there is no need to design a special fixture for internal hole machining, significantly reducing tooling investment costs and better ensuring machining quality.

[0033] In this embodiment, the machining method solves the pain points of thin-walled bushing deformation and precision control through the combination of shaping, stress relief, and reference finishing, and has better adaptability. There is no need to frequently adjust the core process framework due to product specification changes, indirectly reducing process adjustment costs.

[0034] As a preferred embodiment of the present application, the step S1 of preparing the thin-walled bushing blank comprises: starting the centrifugal casting device to make the mold reach a preset rotating speed, synchronously starting the induction heater, and pouring the alloy liquid into the rotating mold at a constant speed; maintaining the rotating speed of the mold until the alloy liquid is completely solidified to obtain the thin-walled bushing blank; and the induction heater is a hollow spiral structure obtained by winding metal wires.

[0035] The core problem of the thin-walled bushing is that the thin wall easily leads to poor flow and uneven distribution of the alloy liquid during casting. The centrifugal force can drive the alloy liquid poured into the mold to spread quickly and uniformly along the inner wall of the mold, avoiding local material shortage and wall thickness deviation caused by gravity casting, reducing the initial wall thickness deviation of the blank from the source, and reducing the adjustment pressure of the subsequent S2 shaping. Moreover, the centrifugal force can promote the aggregation of bubbles, slag and other impurities in the alloy liquid to the center of the mold (non-molding area), and ultimately remove the pouring riser, effectively reducing the internal porosity, porosity and other defects of the blank. At the same time, the centrifugal force can make the alloy liquid more closely adhere to the inner wall of the mold before solidification, improving the density of the metal organization.

[0036] The mold cavity of the thin-walled bushing is narrow and has fast heat dissipation. If the temperature of the alloy liquid drops rapidly during pouring, the flowability will suddenly decrease, and then cold separation (alloy liquid not completely fused gap), insufficient pouring and other defects will occur. The induction heater with high electrical conductivity copper wire wound into a hollow spiral structure can uniformly heat the mold or the alloy liquid through electromagnetic induction, continuously maintain the pouring temperature and flowability of the alloy liquid, and ensure that it can fully fill every detail of the thin-walled cavity to avoid forming defects. The hollow spiral structure can make the magnetic field of the induction heating cover most of the circumferential and axial areas of the mold. Compared with the traditional local heating method, the temperature field of the mold and the alloy liquid can be more uniformly controlled.

[0037] Exemplarily, the preset rotating speed is set to 200-1500 rpm, which can be reasonably adjusted according to the defect condition of the thin-walled bushing blank obtained by centrifugal casting.

[0038] As a preferred embodiment of the present application, the inner diameter of the shaping mold for the shaping treatment in the step S2 is 0.98-0.995 times the outer diameter of the first intermediate product.

[0039] The rigid constraint of the inner hole of the die in the preferred embodiment forms uniform and controllable extrusion pressure on the outer circle of the product. If the inner diameter of the sizing die is too large, the extrusion pressure of the die on the outer circle of the product is insufficient, and the recesses of rough machining cannot be completely smoothed or the ovality cannot be corrected, and the outer circle after sizing still has obvious deformation, and the wall thickness difference is easy to cause by uneven allowance during subsequent S5 outer circle grinding. If the inner diameter of the sizing die is too small, the extrusion pressure exceeds the metal plastic bearing range of the thin-walled bushing, which may cause local cracking and wrinkling of the outer circle of the product, or generate residual stress far exceeding the S3 heat setting that can be eliminated, thereby increasing the subsequent deformation risk. By limiting the inner diameter of the sizing die for sizing treatment to 0.98-0.995 times the outer diameter of the first intermediate product, the outer circle of the product can be gently plastically deformed under pressure, which not only completely corrects the rough machining defects and makes the outer circle contour close to a circle, but also avoids structural damage caused by excessive metal deformation.

[0040] Further, the sizing treatment press in step S2 is a 200t press.

[0041] As a preferred embodiment of the present application, the preset requirements in step S4 include that the flatness of a single end face is not greater than 0.02mm, and the parallelism between two end faces is not greater than 0.03mm.

[0042] As a preferred embodiment of the present application, the grinding of the outer circle of the fourth intermediate product to the target size in step S5 includes: clamping and fixing the fourth intermediate product with a clamp, then fixing the clamp with the fourth intermediate product on the outer circle grinding machine, positioning with the center hole, setting the outer circle grinding process parameters, and precisely grinding the outer circle of the fourth intermediate product to the target size.

[0043] The clamp design needs to adapt to the structure of the thin-walled bushing, and the axial compression is used instead of radial hard clamping, or the large-area contact between the clamp and the bushing is used to disperse the clamping force, so as to avoid permanent deformation caused by local stress exceeding the elastic limit of the metal, and ensure that the bushing still maintains the reference shape after clamping and flat grinding in S4.

[0044] As a preferred embodiment of the present application, referring to Figure 2As shown, the clamp comprises a base plate 1, a pressing plate 2 and a stud 3, one end of the base plate 1 is provided with a first protrusion matched with the first end opening gap of the fourth intermediate product 6, and the middle part of the base plate 1 is provided with a first through hole. One end of the pressing plate 2 is provided with a second protrusion matched with the second end opening gap of the fourth intermediate product 6, and the middle part of the pressing plate 2 is provided with a second through hole. The stud 3 passes through the first through hole and the second through hole at both ends and is matched and connected with the nut 4, and the relative position between the base plate 1 and the pressing plate 2 is adjusted by the nut 4; the outer diameter of the first protrusion is 0.2-0.5mm smaller than the inner diameter of the first end opening of the fourth intermediate product 6; and the outer diameter of the second protrusion is 0.2-0.5mm smaller than the inner diameter of the second end opening of the fourth intermediate product 6.

[0045] Compared with the traditional chuck radial hard clamp, the clamping force of the clamping angle structure provided by the preferred embodiment is applied in the axial direction parallel to the bushing axis, and the size of the clamping force can be adjusted by the tightness of the nut, so as to avoid the extrusion deformation of the thin-walled bushing by the radial force and protect the initial shape of the outer circle and the inner hole of the bushing. Moreover, the adjustment mode of the nut allows the positioning to be performed first and then the pressing to be performed, the fourth intermediate product 6 is sleeved on the first protrusion and the second protrusion first, the gap matching is easy to clamp, and after the circumferential position of the fourth intermediate product 6 is confirmed, the nut is tightened for fixing, so that the operation is convenient and the positioning accuracy is not damaged.

[0046] Specifically, before the outer circle is ground, the clamp is taken off from the outer circle grinding machine, the axis of the base plate 1 is in the vertical direction, then the fourth intermediate product 6 is freely clamped on the first protrusion of the base plate 1, the circumferential direction position of the fourth intermediate product 6 can be manually adjusted during the clamping process to improve the uniformity of the outer circle grinding allowance, but the bushing outer circle cannot be knocked, then the fourth intermediate product 6 is fastened on the clamp by the pressing plate 2 and the nut 5, finally the clamp and the fourth intermediate product 6 are installed on the outer circle grinding machine together and are positioned by the center hole, and the outer circle is ground.

[0047] Further, referring to Figure 2 As shown, the gasket 5 is connected between the nut 4 and the base plate 1 and between the nut 4 and the pressing plate 2.

[0048] As a preferred embodiment of the present application, the step S5 of adopting the vertical machining center or vertical numerical control milling machine to finish machining the inner hole of the fourth intermediate product to the target size comprises: when the perpendicularity of the spindle of the vertical machining center or vertical numerical control milling machine to the workbench is less than or equal to the bushing wall thickness difference target value x 0.8 ÷ bushing length, the fourth intermediate product is clamped and fixed on the workbench of the vertical machining center or vertical numerical control milling machine, the inner hole finish machining process parameters are set, and the inner hole of the fourth intermediate product is finish machined to the target size. That is, when the equipment accuracy meets the requirements, the inner hole is efficiently and accurately formed relying on the equipment accuracy itself.

[0049] When the perpendicularity between the spindle and the worktable of the vertical machining center or vertical CNC milling machine is greater than the target value of the difference between the bushing wall thicknesses × 0.8 ÷ the bushing length, a support plate is provided, the clamping end face of the fourth intermediate product and the support face of the support plate are respectively milled by using the same fine milling equipment, the fourth intermediate product is clamped and fixed on the support face of the plate, the clamping end face of the fourth intermediate product is in contact with the support face of the plate, the inner hole fine machining process parameters are set, and the inner hole of the fourth intermediate product is fine machined to the target size. That is, when the equipment precision is insufficient, the equipment precision defects are compensated by the tooling, and the deviation between the tool axis and the bushing reference axis is forcibly corrected.

[0050] Compared with the machining method of the conventional thin-walled bushing, the process flow of the present application increases the shaping and heat setting, which can effectively reduce the internal residual stress of the workpiece to control the product shape and position tolerance. The two-end-face flat grinding process is added, which can effectively reduce the deformation in the outer circle grinding process to control the product outer circle cylindricity; the special outer circle grinding tooling with a simplified structure is designed, which not only can effectively reduce the tooling production cycle and cost, but also can effectively ensure the product outer circle precision. After the inner hole fine machining is changed from the boring machine to the vertical machining center, not only the special fixture is not needed, the cost is greatly reduced, but also the quality can be better ensured.

[0051] The above examples are only preferred embodiments for fully illustrating the present application, and the protection scope of the present application is not limited thereto. The equivalent substitutions or transformations made by the person skilled in the art on the basis of the present application are within the protection scope of the present application.

Claims

1. A method of machining a thin-walled bushing, characterized by, The method comprises the following steps: S1, preparing a thin-wall bushing blank, rough machining the total length and the inner hole of the thin-wall bushing blank to obtain a first intermediate product, and reserving a machining allowance; S2, using the two end faces of the first intermediate product as positioning references, performing shaping treatment on the outer circle of the first intermediate product on a press to obtain a second intermediate product; S3, keeping the second intermediate product at a temperature of 200-300 DEG C for 4-6 hours, furnace cooling to 100 DEG C or below, and air cooling to room temperature after being taken out of the furnace to obtain a third intermediate product; S4, flat grinding the two end faces of the third intermediate product, so that the flatness of a single end face and the parallelism between the two end faces meet preset requirements, and the total length reaches a target size to obtain a fourth intermediate product; S5, grinding the outer circle of the fourth intermediate product to the target size by using an outer circle grinding machine, and performing finish machining on the inner hole of the fourth intermediate product to the target size by using a vertical machining center or a vertical numerical control milling machine to obtain the thin-wall bushing.

2. The method of machining a thin-walled bushing according to claim 1, characterized in that, The step S1 of preparing the thin-wall bushing blank comprises the following steps: starting a centrifugal casting device to make the mold reach a preset rotating speed, synchronously starting the induction heater, and pouring the alloy liquid into the rotating mold at a constant speed; maintaining the rotating speed of the mold until the alloy liquid is completely solidified to obtain the thin-wall bushing blank. The induction heater is a hollow spiral structure obtained by winding a metal wire.

3. The method of machining a thin-walled bushing of claim 1, wherein: The inner diameter of the shaping die for performing the shaping treatment in the step S2 is 0.98-0.995 times the outer diameter of the outer circle of the first intermediate product.

4. The method of machining a thin-walled bushing of claim 1, wherein: The preset requirements in the step S4 include that the flatness of a single end face is not greater than 0.02 mm, and the parallelism between the two end faces is not greater than 0.03 mm.

5. The method of claim 1, wherein: The step S5 of grinding the outer circle of the fourth intermediate product to the target size by using the outer circle grinding machine comprises the following steps: clamping and fixing the fourth intermediate product by using a clamp, then fixing the clamp with the fourth intermediate product fixed thereon on the outer circle grinding machine, positioning by using a center hole, setting outer circle grinding process parameters, and precisely grinding the outer circle of the fourth intermediate product to the target size.

6. The method of machining a thin-walled bushing according to claim 5, characterized in that: The clamp comprises a base plate, a pressing plate and a stud, one end of the base plate is provided with a first protrusion which is gap-fitted with the first end opening of the fourth intermediate product, the middle part of the base plate is provided with a first through hole; one end of the pressing plate is provided with a second protrusion which is gap-fitted with the second end opening of the fourth intermediate product, the middle part of the pressing plate is provided with a second through hole; the stud passes through the first through hole and the second through hole at two ends and is connected with nuts in a matched mode, and the relative position between the base plate and the pressing plate is adjusted by the nuts; The outer diameter of the first protrusion is 0.2-0.5 mm smaller than the inner diameter of the first end opening of the fourth intermediate product. The outer diameter of the second protrusion is 0.2-0.5 mm smaller than the inner diameter of the second end opening of the fourth intermediate product.

7. The method of claim 1, wherein: The step S5 of performing finish machining on the inner hole of the fourth intermediate product to the target size by using the vertical machining center or the vertical numerical control milling machine comprises the following steps: when the perpendicularity between the spindle of the vertical machining center or the vertical numerical control milling machine and the workbench is less than or equal to the target value of the bushing wall thickness difference multiplied by 0.8 divided by the length of the bushing, the fourth intermediate product is clamped and fixed on the workbench of the vertical machining center or the vertical numerical control milling machine, finish machining process parameters of the inner hole are set, and the inner hole of the fourth intermediate product is finish machined to the target size. When the perpendicularity between the spindle and the worktable of the vertical machining center or vertical numerical control milling machine is greater than the target value of the difference between the bushing wall thicknesses × 0.8 ÷ the bushing length, a support plate is provided, and the clamping end face of the fourth intermediate product and the supporting surface of the support plate are respectively milled by using the same fine milling equipment, the fourth intermediate product is clamped and fixed on the supporting surface of the plate, the clamping end face of the fourth intermediate product is in contact with the supporting surface of the plate, and the inner hole fine machining process parameters are set to fine machine the inner hole of the fourth intermediate product to the target size.

Images