A fixture and method for machining thin-walled toothed rings

Abstract

This invention discloses a machining fixture and method for thin-walled toothed rings. The fixture includes a lower part, an upper part, an embedded damping ring, a pressure plate, a clamping nut, and screws. Multiple rubber rings are fitted onto the outer surface of the embedded damping ring and secured with the screws. When machining the thin-walled toothed ring, the embedded damping ring fills the cavity F of the ring. The positioning and supporting surfaces of the upper part of the fixture, in conjunction with the pressure plate and nut, clamp the ring. During machining, the outer diameter, outer shape, tooth grooves, tooth grooves, and outer shape are sequentially rough-machined, ultimately obtaining a thin-walled toothed ring that meets the requirements for runout and surface roughness. This invention offers high machining efficiency and a high pass rate, demonstrating excellent performance in machining ring-shaped cavity structures.

Description

Technical Field

[0001] This invention belongs to the field of thin-walled toothed ring machining technology in aero-engine manufacturing, and relates to the design of CNC machining schemes and the design and manufacture of CNC machining fixtures for thin-walled toothed rings. Background Technology

[0002] Figure 1 The image shows a thin-walled toothed ring made of stainless steel, which possesses excellent high-temperature strength and corrosion resistance, and is widely used in aerospace and energy equipment. The thin-walled toothed ring requires machining the teeth on its outer cylindrical surface (forming the teeth by cutting tooth grooves). A planar sketch of the part is shown below. Figure 1 The surface roughness requirement is Ra0.8, and the runout of the outer circle of the grating teeth relative to datums A and B is difficult to guarantee at 0.03. The reasons are as follows: 1) The fixture cannot always be coaxial with the machine tool spindle when it is clamped on the machine tool. A fixture that can be re-aligned and reused needs to be designed to ensure that the runout between the outer circle positioning surface of the fixture and the spindle is within 0.005. 2) There will be a gap between the inner hole B of the part and the outer circular surface of the fixture positioning, which directly affects the runout of the thin-walled grate ring by 0.03. 3) The thinnest part of the wall is only 1mm and there is a cavity F. The overall rigidity of the part is very poor. It is prone to vibration during processing and even tool breakage, which makes it impossible to guarantee the runout 0.03 and surface roughness Ra0.8.

[0003] Previously, increasing the overall rigidity of thin-walled toothed rings involved casting low-melting-point metal into the cavity F. While this achieved the goal of enhancing the rigidity of the part, it resulted in poor vibration damping and low part processing efficiency. The low-melting-point metal casting process was as follows: melting low-melting-point metal → casting metal into the part cavity F → part cooling → part processing → melting low-melting-point metal → part cooling. The entire process took 4 hours, and the part processing qualification rate was less than 80%.

[0004] For the reasons mentioned above, there is an urgent need for a thin-walled toothed ring turning fixture and method to solve the above problems. The key to part machining lies in the planning of CNC machining scheme, the design and manufacturing of CNC machining fixture. Summary of the Invention

[0005] The present invention aims to provide a machining fixture and method for thin-walled toothed rings, to solve the technical problems of runout and surface roughness defects in toothed rings, further improve machining efficiency and yield, and plan a CNC machining scheme suitable for this type of toothed ring.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A fixture for machining thin-walled toothed rings includes: The lower part of the fixture includes a clamping part connected to the chuck and a connecting upper end face, and the connecting upper end face has a threaded hole. The upper part of the fixture includes a lower end face for connection, a support surface, a positioning surface and a stud. The lower end face for connection has a through hole that penetrates the support surface. The distribution of the through hole corresponds one-to-one with the distribution of the threaded holes on the upper end face for connection. The support surface is an annular surface and the positioning surface is a cylindrical surface. The stud is coaxial with the clamping part of the lower part of the fixture. An embedded damping ring is installed in the cavity F of a thin-walled toothed ring. The embedded damping ring is made of metal, and multiple rubber rings are mounted on the outer ring surface of the embedded damping ring at intervals along the axial direction of the embedded damping ring. A pressure plate with a central hole is provided and is fitted onto a stud on the upper part of the fixture through the central hole. One end face of the pressure plate forms a pressing surface. A clamping nut is installed on a stud on the upper part of the clamp, such that the pressure plate is located between the clamping nut and the support surface on the upper part of the clamp; A screw is installed in a through hole on the upper part of the fixture and extends into a threaded hole on the lower part of the fixture corresponding to the through hole. The outer diameter of the screw shank in the through hole is smaller than the inner diameter of the through hole, thereby forming a radial clearance.

[0007] As one option, the embedded shock-absorbing ring has a screw hole, and a fixing screw is installed in the screw hole.

[0008] A method for machining thin-walled toothed rings includes the following steps: Step 1: Machining the inner holes B and E of the thin-walled toothed ring. Supporting and pressing the two end faces of the annular process edge corresponding to the tooth surface on the thin-walled toothed ring along the axial direction of the thin-walled toothed ring. Aligning the axial end face on the thin-walled toothed ring that is parallel to the reference A. After one clamping, the machining of inner holes B and E is completed. Controlling the flatness of the axial end face parallel to the reference A, controlling the parallelism between the axial end face parallel to the reference A and the reference A, controlling the runout between inner hole E and inner hole B, and controlling the dimensional tolerance of inner hole B. Step 2: Using the machining fixture described in the claims, clamp the thin-walled grate ring. Assemble the upper positioning surface of the fixture with the inner hole B, insert the embedded shock-absorbing ring into the cavity F of the thin-walled grate ring and press the rubber ring. Support the embedded shock-absorbing ring with the upper support surface of the fixture, while supporting the axial end face of the thin-walled grate ring that is parallel to the reference A. Use a pressure plate to press the axial end face of the thin-walled grate ring corresponding to the opening of the inner hole E, and use a nut to press the pressure plate. Clamp the clamping part of the lower part of the fixture using a chuck. Step 3: Machining the teeth on the thin-walled toothed ring, by performing the following steps in sequence: Rough turn the outer diameter to remove the annular process edge from step one; Roughly machine the shape, remove most of the excess material on the outer circle of the thin-walled toothed ring, and leave room for finishing; Roughly cut the grate teeth grooves, removing most of the excess material from the thin-walled grate teeth grooves, leaving room for finishing; Precision cutting and machining of the grate teeth ensures the final dimensions and surface roughness of the grate teeth. The outer shape is precision machined, and the outer circle contour of the thin-walled toothed ring is precisely machined to ensure the final outer circle dimension and final runout.

[0009] As one solution: In step two, the positioning surface on the upper part of the fixture is fitted with the inner hole B in a tight fit. In step two, the runout of the inner hole E is adjusted by tapping the thin-walled comb ring.

[0010] As one possible approach: In step three, C-type inserts are used for rough turning of the outer diameter, D-type inserts are used for rough turning of the outer shape, grooving cutter is used for rough cutting of the grate tooth groove, ball end grooving cutter is used for fine cutting of the grate tooth groove, and V-type positive rake angle insert is used for fine turning of the outer shape.

[0011] As one possible approach: In step three, the rotational speed of the roughing outer diameter is less than the rotational speed of the roughing outer shape, the feed rate of the roughing outer diameter is greater than the feed rate of the roughing outer shape, the rotational speed of the roughing grate groove, the rotational speed of the finishing grate groove and the rotational speed of the finishing outer shape are the same, the feed rate of the roughing grate groove is less than the feed rate of the finishing grate groove, and the feed rate of the finishing grate groove is less than the feed rate of the finishing outer shape.

[0012] As one possible solution: In step two, before using a machining fixture to clamp the thin-walled toothed ring, the upper end face of the lower part of the fixture and the lower end face of the upper part of the fixture are ground and polished, and the contact area of ​​the upper end face and the lower end face of the fixture is checked by coloring.

[0013] As one possible solution: In step two, before the thin-walled toothed ring is clamped for the first time using a machining fixture, machining allowances are left on the upper support surface and positioning surface of the fixture. The positioning surface is machined on a lathe to fit the inner hole B to ensure the fit clearance, and the support surface is exposed to light to ensure the perpendicularity between the support surface and the positioning surface.

[0014] This invention explores a machining fixture and method for thin-walled toothed rings, providing an effective way to enhance rigidity and achieve excellent vibration reduction for hollow ring-shaped thin-walled parts, meeting the technical requirements of 0.03 mm runout and Ra 0.8 surface roughness for thin-walled toothed rings. Compared with traditional low-melting-point metal casting methods, it offers higher machining efficiency and a higher yield rate. The embedded vibration-damping ring structure of this invention has been extended to the machining of other "ring-shaped hollow structure" parts, facilitating on-site operation and achieving excellent results. Attached Figure Description

[0015] Figure 1 It is a planar sketch of the part; Figure 2 This is a schematic diagram of the control principle for assembly clearance of parts; Figure 3 This is a schematic diagram of the embedded shock-absorbing ring and its component assembly. Figure 4 This is a schematic diagram of machining fixtures and parts assembly; Figure 5 It is a 3D assembly drawing of the fixture and parts; In the diagram, 1. Lower part of the clamp; 2. Upper part of the clamp; 3. Embedded shock-absorbing ring; 4. Thin-walled toothed ring; 5. Pressure plate; 6. Pressure nut; 7. Screw; 8. Rubber ring; 9. Fixing screw. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0017] This invention mainly includes two aspects: the design of CNC machining scheme for thin-walled toothed rings and the design of CNC machining fixtures.

[0018] First, the design of a CNC machining solution for thin-walled toothed rings: 1) Control of the gap between the thin-walled toothed ring 4 and the fixture positioning.

[0019] The clearance between the inner hole B of the thin-walled toothed ring 4 and the fixture directly affects the machining runout of the thin-walled toothed ring 4 (0.03). Therefore, when designing the machining process route for the thin-walled toothed ring 4, it is required that before the actual machining of the teeth, such as... Figure 2 As shown, a ring-shaped process edge is reserved on the thin-walled grate ring 4. First, the left end face of the ring-shaped process edge of the thin-walled grate ring 4 is supported, and then the right end face of the ring-shaped process edge of the thin-walled grate ring 4 is pressed tightly, thereby achieving axial pressing of the thin-walled grate ring 4. The nitriding surface of the thin-walled grate ring 4 is aligned to within 0.005 (that is, ensuring that the flatness of the nitriding surface is within 0.005 is necessary for processing). Figure 2 When machining the datum surface A, ensure the parallelism between the nitrided surface and datum A is within 0.01. Complete the machining of the inner holes B and E (inner hole E includes the surface of datum A, i.e., the bottom surface of inner hole E) of the thin-walled grate ring 4 in a single clamping operation, ensuring the parallelism between the nitrided surface and datum A is within 0.01, the runout of inner hole E relative to inner hole B is within 0.005 (guaranteed in a single clamping operation), and the dimensional tolerance of inner hole B is controlled within 0.01. Datum quality assurance control: a) The inner hole B of the thin-walled toothed ring 4 should fit tightly with the outer circle of the fixture, with a gap of less than 0.01.

[0020] b) After the thin-walled toothed ring 4 is mounted on the fixture, a dial indicator should be used to check the runout of the inner hole E. It should be within 0.01 (this refers to the runout relative to the machine tool spindle; the design drawing uses references A and B, but reference B is obscured by the upper part 2 of the fixture during part clamping and cannot be directly aligned; therefore, in...). Figure 2 The ΦB and ΦE holes are machined together to ensure coaxiality of 0.005. Aligning the ΦE hole is equivalent to aligning the ΦB hole. Since the runout tolerance of the toothed comb is 0.03, alignment is needed to improve accuracy and ensure that the ΦB and ΦE holes are concentric with the machine tool spindle (the machined toothed comb is concentric with the machine tool spindle). If the requirements are not met, a copper rod can be used to gently tap the thin-walled toothed comb ring 4 to eliminate uneven gaps and ensure a runout of 0.01. See the assembly gap control principle diagram of the thin-walled toothed comb ring 4. Figure 2 .

[0021] 2) Design of a rigidity enhancement scheme for thin-walled toothed ring 4.

[0022] The thin-walled toothed ring 4 is a thin-walled component with poor rigidity, making it prone to vibration during processing. Therefore, it is necessary to enhance the overall rigidity of the thin-walled toothed ring 4. To address this, the present invention designs an embedded damping ring 3, such as... Figure 3 As shown. The core idea is to start from the inside of the thin-walled toothed ring 4, by introducing an elastic damping ring with three rubber rings 8 whose outer diameter matches the inner diameter of the cavity F of the thin-walled toothed ring 4. Before processing, this embedded damping ring 3 is inserted into the cavity F of the thin-walled toothed ring 4, and a force is applied (usually by manual pressing) to deform the rubber rings 8 and make them tightly adhere to the surface of the cavity F of the thin-walled toothed ring 4. A dedicated pressing mechanism (i.e....) is then used. Figure 3 Four fixing screws (9) are screwed into the threaded holes on the embedded damping ring 3 to fix the embedded damping ring 3 within the cavity F of the thin-walled toothed ring 4. This fundamentally changes the overall rigidity of the thin-walled toothed ring 4. The rubber ring 8 itself has good internal friction characteristics, which can effectively absorb and dissipate the vibration energy generated during cutting, resulting in excellent damping effect. This invention adopts a combination of embedded damping ring 3 made of metal material and rubber ring 8 made of elastic material. The inner part is hard and the outer part is flexible, so that the deformation is mainly concentrated in the small area where the rubber ring 8 is located. Multiple rubber rings 8 have sufficient deformation space. This combination method supports and fills the cavity F on the one hand, and ensures that the embedded damping ring 3 and the rubber ring 8 are firmly fixed in the cavity F and do not detach. Figure 3 In this design, the gap between the embedded damping ring 3 and the cavity F is 1mm. This gap facilitates the insertion and removal of the embedded damping ring 3 into and out of the cavity F of the thin-walled toothed ring 4. For example... Figure 3 The embedded shock-absorbing ring 3 is clamped on the inner wall of the thin-walled comb-shaped ring cavity F by four fixing screws 9. The inner diameter formed by the ends of the four fixing screws 9 is stuck in the inner wall of the cavity F to achieve fixation.

[0023] The usage method of the embedded shock absorber ring 3 is as follows: a) Insert the three rubber rings 8 into the three grooves on the outer ring surface of the embedded shock-absorbing ring 3; b) Screw the fixing screws 9 (4 screws, evenly distributed in the cross direction) into the embedded shock-absorbing ring 3; c) Press the assembled embedded shock-absorbing ring 3 into the cavity F of the thin-walled toothed ring 4, and apply force to deform the rubber ring 8 so that it fits tightly against the surface of the cavity F of the thin-walled toothed ring 4. d) Use an Allen wrench to evenly and alternately tighten the fixing screws 9 to fix the embedded shock-absorbing ring 3 into the cavity F of the thin-walled toothed ring 4 (the embedded shock-absorbing ring 3 and the cavity F are clearance fit, such as...). Figure 3 As shown in dimension 1, there is a 1mm gap. If the embedded shock-absorbing ring 3 is not fixed, it will loosen during processing, failing to achieve the desired support and shock absorption effects, and posing a safety risk. Therefore, it must be fixed. Figure 3 The end faces of the four fixing screws 9 have a 45° chamfer, which makes line contact with the outer circular surface of the cavity F. The four fixing screws 9 are equivalent to a four-jaw chuck. When the four fixing screws 9 are screwed in, the circle formed by the four fixing screws 9 will become smaller, so that it can be fixed on the inner wall of the cavity F. The even and alternating screwing is to ensure that the embedded shock-absorbing rings 3 are distributed as evenly as possible in the cavity F.

[0024] 3) Thin-walled toothed ring 4-step CNC process design.

[0025] The CNC machining of the thin-walled toothed ring 4 is divided into roughing and finishing processes. The specific steps are as follows: a) Rough turning of the outer diameter. Remove the annular process edge, use a C-type insert, spindle speed S=100r / min, feed F=0.25; b) Rough machining of the outer shape. Remove the large allowance of the outer diameter of the toothed ring, leaving a finishing allowance of 0.3. Use a D-type insert, a rotation speed of S=150r / min, and a feed rate of F=0.2. c) Rough cutting of the grate tooth grooves. Remove the large allowance of the grate tooth grooves, leaving a finishing allowance of 0.15. Use a 1mm wide grooving cutter, with a rotation speed of S=150r / min and a feed rate of F=0.03. d) Precision machining of the grate tooth grooves. The grate tooth grooves are precision machined to ensure dimensional accuracy and surface roughness Ra0.8, using an R0.75 ball end mill, with a rotation speed S=150 r / min and a feed rate F=0.04. e) Finish machining of the outer profile. The outer diameter of the thin-walled toothed ring 4 is precision machined to ensure a dimensional tolerance and runout of 0.03. V-shaped inserts with a positive rake angle are used, with a rotational speed of S=150r / min and a feed rate of F=0.06.

[0026] Second, CNC machining fixture design: The fixture employs a segmented design principle, dividing it into an upper fixture part 2 and a lower fixture part 1. The two parts are connected by four screws 7. There is a 0.1mm clearance on one side between the outer diameter of the screw shank of each screw 7 and the screw hole in the upper fixture part 2. (See attached image.) Figure 4 By adjusting this gap, the runout between the fixture positioning surface and the machine tool spindle is ensured to be within 0.005. The mating surfaces of the upper part 2 and the lower part 1 of the fixture are ground and polished, and the mating area is checked by coloring at 95% min. For the first machining, a 0.2mm allowance should be left between the support surface and the positioning surface of the upper part 2 of the fixture (this allowance is to ensure that the support surface and the positioning surface of the fixture are perpendicular). The positioning surface is machined on a CNC lathe to fit the inner hole B of the thin-walled toothed ring 4, ensuring that the fit clearance is controlled within 0.01. At the same time, the allowance is removed after the support surface is polished to ensure that the perpendicularity between the support surface and the positioning surface is within 0.01.

[0027] The clamp usage process is as follows, please refer to... Figure 4 Assembly diagram of CRRC machining fixture and thin-walled toothed ring 4: 1) Fit the upper part 2 of the clamp with the lower part 1 of the clamp, aligning the screw holes; 2) Screw in screw 7, tightening it evenly and alternately, but do not lock screw 7; 3) Load the assembled fixture into the machine tool spindle and clamp it with a three-jaw chuck; 4) On the machine tool, use a dial indicator with an accuracy of 0.001 to check the runout of the positioning surface of the upper part 2 of the fixture. It should be within 0.005. If it exceeds the requirement, gently tap the outer circle of the largest diameter part of the upper part 2 of the fixture with a copper rod to ensure that the runout is within 0.005. Tighten the screw 7, and check the runout of the positioning surface of the upper part 2 of the fixture again. It should be within 0.005. 5) Install the thin-walled toothed ring 4 with the embedded damping ring 3 into the fixture, and check the inner hole E of the thin-walled toothed ring 4 with a dial indicator to ensure that the runout is within 0.01 (the runout reference is the machine tool spindle). 6) Install the pressure plate 5, install the nut 6 and tighten it.

[0028] When machining the thin-walled toothed ring, the reference machining of the thin-walled toothed ring 4 before machining the toothed ring is carried out according to the above scheme to ensure the quality of the thin-walled toothed ring 4 blank. Based on the above requirements, design and manufacture machining fixtures and embedded shock absorber rings 3; The equipment for machining thin-walled toothed rings includes: CNC lathe, five-axis machining center, surface grinder and fitter's table.

[0029] During the above CNC machining, UG software is used for program compilation. UG simulation verification should show no interference, overcutting, or residue. The UG toolpath file is then post-processed into an NC program that the machine tool can recognize. When machining the thin-walled toothed ring, the assembled fixture is loaded into the three-jaw chuck of the CNC lathe and clamped. A dial indicator is used to check that the runout of the fixture positioning surface is within 0.005. The thin-walled toothed ring 4 (with the embedded shock-absorbing ring 3 already assembled) is loaded. A dial indicator is used to check that the runout of the inner hole E of the thin-walled toothed ring 4 is within 0.01. The thin-walled toothed ring 4 is clamped. The prepared CNC program is imported into the machine tool, the machining coordinate system is established, the tool is clamped, and the machine tool is started to machine the thin-walled toothed ring 4.

[0030] Using the fixture and CNC machining scheme for the thin-walled toothed ring 4 designed and manufactured according to this invention, and in conjunction with the cutting parameters of this invention, the vibration phenomenon is completely eliminated, and the machining process is stable and smooth. The external dimensions of the thin-walled toothed ring 4, with a runout of 0.03 and a surface roughness of Ra 0.8, are all qualified. The stable machining process reduces the impact of cutting vibration on the tool, prevents tool tip chipping and abnormal wear, extends tool life, and ensures product machining quality. The CNC machining qualification rate of the thin-walled toothed ring 4 is 100%.

[0031] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A thin-walled serration ring turning jig characterized by, include: The lower part of the clamp (1) includes a clamping part connected to the chuck and a connecting upper end face, and the connecting upper end face has a threaded hole. The upper part (2) of the clamp includes a lower end face for connection, a support surface, a positioning surface and a stud. A through hole is opened on the lower end face for connection, and the distribution position of the through hole corresponds one-to-one with the distribution position of the threaded hole on the upper end face for connection. The support surface is an annular surface and the positioning surface is a cylindrical surface. The stud is coaxial with the clamping part of the lower part (1) of the clamp. Embedded shock absorber ring (3), the embedded shock absorber ring (3) is installed in the cavity F of the thin-walled toothed ring (4), the embedded shock absorber ring (3) is made of metal material, and multiple rubber rings (8) are mounted on the outer ring surface of the embedded shock absorber ring (3) at intervals along the axial direction of the embedded shock absorber ring (3). The pressure plate (5) has a central hole and is sleeved on the stud of the upper part (2) of the clamp through the central hole. One end face of the pressure plate (5) forms a pressing surface. A clamping nut (6) is installed on a stud on the upper part (2) of the clamp, and the pressure plate (5) is located between the clamping nut (6) and the support surface of the upper part (2) of the clamp; Screw (7), the screw (1) is installed in the through hole of the upper part (2) of the fixture and extends to the threaded hole corresponding to the through hole on the lower part (1) of the fixture. The outer diameter of the screw shank of the screw (7) in the through hole is smaller than the inner diameter of the through hole, thereby forming a radial gap.

2. A thin-walled gullet ring machining fixture according to claim 1, characterized in that: The embedded shock-absorbing ring (3) has a screw hole, and a fixing screw (9) is installed in the screw hole.

3. A method of machining a thin-walled serration ring, characterized by, Includes the following steps: Step 1: Machining the inner holes B and E of the thin-walled toothed ring (4), supporting and pressing the two end faces of the annular process edge on the surface of the thin-walled toothed ring (4) corresponding to the tooth along the axial direction of the thin-walled toothed ring (4), aligning the axial end face of the thin-walled toothed ring (4) parallel to the reference A, completing the machining of the inner holes B and E after one clamping, controlling the flatness of the axial end face parallel to the reference A, controlling the parallelism between the axial end face parallel to the reference A and the reference A, controlling the runout between the inner hole E and the inner hole B, and controlling the dimensional tolerance of the inner hole B; Step 2: Using the machining fixture described in claim 1, clamp the thin-walled toothed ring (4). Assemble the positioning surface of the upper part (2) of the fixture with the inner hole B, insert the embedded shock-absorbing ring (3) into the cavity F of the thin-walled toothed ring (4) and press the rubber ring (8). Support the embedded shock-absorbing ring (3) with the support surface of the upper part (2) of the fixture, while supporting the axial end face of the thin-walled toothed ring (4) parallel to the reference A. Use the pressure plate (5) to press the axial end face of the thin-walled toothed ring (4) corresponding to the opening of the inner hole E, and use the nut (6) to press the pressure plate (5). Clamp the clamping part of the lower part (1) of the fixture with the chuck. Step 3: Machining the teeth on the thin-walled toothed ring (4) by performing the following steps in sequence: Rough turn the outer diameter to remove the annular process edge from step one; Roughly machine the shape, remove most of the allowance at the outer circle of the thin-walled toothed ring (4), and leave a finishing allowance; Roughly cut the grate teeth grooves, removing most of the excess material from the thin-walled grate teeth grooves, leaving room for finishing; Precision cutting and machining of the grate teeth ensures the final dimensions and surface roughness of the grate teeth. The outer shape is precision machined, and the outer circle contour of the thin-walled toothed ring (4) is precision machined to ensure the final outer circle size and final runout.

4. The method for machining a thin-walled toothed ring according to claim 3, characterized in that: In step two, the positioning surface of the upper part (2) of the fixture is fitted with the inner hole B in a tight fit. In step two, the runout of the inner hole E is adjusted by tapping the thin-walled comb ring (4).

5. A method of machining a thin-walled gilled ring according to claim 3, characterized in that: In step three, C-type inserts are used for rough turning of the outer diameter, D-type inserts are used for rough turning of the outer shape, grooving cutter is used for rough cutting of the grate tooth groove, ball end grooving cutter is used for fine cutting of the grate tooth groove, and V-type positive rake angle insert is used for fine turning of the outer shape.

6. A method of machining a thin-walled gilled ring according to claim 3, characterized in that: In step three, the rotational speed of the roughing outer circle is less than the rotational speed of the roughing outer shape, the feed rate of the roughing outer circle is greater than the feed rate of the roughing outer shape, the rotational speed of the roughing grate groove, the rotational speed of the finishing grate groove and the rotational speed of the finishing outer shape are the same, the feed rate of the roughing grate groove is less than the feed rate of the finishing grate groove, and the feed rate of the finishing grate groove is less than the feed rate of the finishing outer shape.

7. A method of machining a thin-walled gilled ring according to claim 3, characterized in that: In step two, before using a machining fixture to clamp the thin-walled toothed ring (4), the upper end face of the lower part (1) of the fixture and the lower end face of the upper part (2) of the fixture are ground and polished, and the contact area of ​​the upper end face and the lower end face of the fixture is checked by coloring.

8. A method for machining a thin-walled toothed ring according to claim 3, characterized in that: In step two, before the thin-walled toothed ring (4) is clamped for the first time using a machining fixture, machining allowance is left on the support surface and positioning surface of the upper part (2) of the fixture. The positioning surface is machined with the inner hole B on the lathe to ensure the fit clearance. The support surface is exposed to light to ensure the perpendicularity between the support surface and the positioning surface.

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