Anti-deformation reinforcing rib structure of hob blade and manufacturing method of anti-deformation reinforcing rib structure

Abstract

The invention discloses an anti-deformation reinforcing rib structure of a hob blade and a manufacturing method thereof.The anti-deformation reinforcing rib structure of the hob blade comprises a center shaft, a mounting disc fixed to the center shaft and a blade body fixed to the mounting disc, and the blade body is a three-dimensional spiral curved-surface-shaped blade and is provided with a front face and a back face; the blade body comprises a front face and a back face, the front face is a working face facing the cutting direction after installation, the back face is a non-working face and is provided with reinforcing ribs continuously extending along a spiral line track, the reinforcing ribs have height gradients in the width direction of the blade body, and the heights of the reinforcing ribs are gradually decreased from the root of the blade body to the cutting edge end of the blade body. The two ends of each reinforcing rib end on the inner sides of the two axial end faces of the blade body. The anti-bending and anti-torsion cutter has the remarkable anti-bending and anti-torsion functions, the problems of resonance and fatigue damage caused by insufficient rigidity are solved, the cutting flatness is improved, and the service life is prolonged.

Description

Technical Field

[0001] This invention relates to the field of garden machinery parts, and in particular to a deformation-resistant reinforcing rib structure for a hobbing blade and its manufacturing method. Background Technology

[0002] Spiral roller lawnmowers are key equipment for achieving high-quality lawn mowing. Their moving blades are single pieces with a three-dimensional spiral curved surface. During operation, they rotate at high speed and form a shearing action with the bottom blade. These blades are subjected to high centrifugal force, periodic grass stem impact, and complex alternating stress for a long time, and have extremely high requirements for rigidity, dimensional stability, and fatigue life.

[0003] Currently, most lawnmower blades are made of thin plates or solid structures without reinforcing ribs. Their rigidity and fatigue resistance depend entirely on the material thickness and hardness. The lack of structural reinforcement design limits their stability and durability in high-intensity working environments. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a deformation-resistant reinforcing rib structure for a hobbing cutter and its manufacturing method, which has significant anti-bending and anti-torsion functions, alleviates the resonance and fatigue damage problems caused by insufficient rigidity, improves cutting smoothness, and extends service life.

[0005] The objective of this invention is achieved through the following technical solution: A deformation-resistant reinforcing rib structure for a hobbing cutter includes a central shaft, a mounting plate fixed on the central shaft, and a cutter body fixed on the mounting plate. The cutter body is a three-dimensional helical curved cutter with a front and a back surface. The front surface is the working surface facing the cutting direction after installation, and the back surface is the non-working surface. The back surface is provided with reinforcing ribs that extend continuously along a helical trajectory. The reinforcing ribs have a height gradient along the width direction of the cutter body, and their height gradually decreases from the root of the cutter body to the cutting edge. The two ends of the reinforcing ribs terminate on the inner side of the axial end faces of the cutter body.

[0006] In one optional embodiment, the reinforcing rib is a wavy reinforcing rib that extends undulatingly along the spiral trajectory.

[0007] In one optional embodiment, the cross-sectional height of the reinforcing rib near the root of the blade body is 1.5~2.0mm, and the cross-sectional height near the cutting edge of the blade body is 0.6~1.0mm.

[0008] In one optional embodiment, the connection between the reinforcing rib and the blade body is provided with a rounded transition, and the radius of the rounded transition is not less than 0.4 times the thickness of the blade body.

[0009] In one optional embodiment, the blade body has a thickness of 1.5~2.5mm and is made of 65Mn spring steel.

[0010] A method for manufacturing a deformation-resistant reinforcing rib structure for a hobbing cutter specifically includes the following steps: S1. Spheroidizing annealing: 65Mn spring steel strip is put into the furnace, held at 780℃ for 2 hours, then slowly reduced to 680℃ and held for 4 hours, and finally cooled to room temperature with the furnace to obtain a uniform spheroidized pearlite structure. S2, Spiral Roller Bending Forming: Annealed strip is fed into the spiral roller bending unit. The upper roller is precisely adjusted according to the target spiral angle and the axial feed speed is matched synchronously, so that the strip can continuously complete bending and axial displacement in the roller gap, forming a three-dimensional spiral curved surface blank in one step, without winding or welding throughout the process. S3. Curved surface fitting stamping: The blank is fixed in the copying fixture to maintain the spiral curved surface shape. The spiral curved surface matching punch is precision machined by five-axis CNC. Pressure is applied along the local normal of the blank to form a reinforcing rib extending along the spiral line on the reverse side. A micro-dimple with a depth of ≤0.1mm is naturally formed on the front side. S4. Fine finishing and shaping: Fine-tune the springback amount of the shaping mold to ensure that the measured value of the helix angle β is within ±0.5° tolerance; S5. Controlled atmosphere heat treatment: After holding at 920℃ in a vacuum furnace for 30 minutes, perform high-pressure quenching with 10MPa high-purity nitrogen, and then temper at 180℃ for 2 hours. S6, Five-axis linkage spiral cutting edge grinding: diamond grinding wheel single cutting depth ≤ 0.02mm, coolant flow rate ≥ 15L / min strong spray cooling; S7. Cryogenic aging treatment: Cryogenically cooled to -70℃ for 4 hours to promote the transformation of residual austenite and release stress, followed by aging at 150℃ for 2 hours to stabilize the microstructure. The dimensional change is <0.01mm within 72 hours after treatment. S8. Surface strengthening: TiAlN-PVD coating on the cutting edge area, and hard chrome plating on the non-working surface.

[0011] In one optional implementation, the helical surface matching punch in step S3 is precision milled / ground by a five-axis linkage CNC machine tool based on the three-dimensional helical surface theoretical model of the blade body. The working surface contour error is strictly controlled within 0.02mm to ensure that the reinforcing ribs are precisely conformal to the helical surface and there is no torsional stress during stamping.

[0012] In one optional implementation, the cryogenic aging treatment in step S7 is based on the synergistic effect of "cold treatment + hot aging" - firstly, the residual austenite is fully transformed and the residual stress of processing is released by cryogenic treatment at -70℃, and then the martensitic structure is stabilized by aging at 150℃.

[0013] In one optional embodiment, the thickness of the TiAlN-PVD coating in step S8 is 2~3μm, and the thickness of the hard chrome coating is 5~8μm.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By continuously extending reinforcing ribs with a height gradient along a spiral trajectory on the non-working surface of the blade body, a gradient transition of structural stiffness from the root to the cutting edge and a precise match of the stress field are achieved. This alleviates the problem of vibration, springback, and fatigue cracks easily generated at the cutting edge and middle due to the uneven cross-sectional stiffness and unreasonable stress distribution of existing blades. Without significantly increasing the weight, the natural frequency and bending stiffness of the blade are improved, making the shearing process smoother, the cut smoother, and effectively extending the fatigue life of the tool.

[0015] 2. By setting the reinforcing ribs as a wave-shaped extension with both ends terminating on the inner side of the two axial end faces of the blade body, continuous stiffness enhancement and effective stress concentration dispersion along the spiral path are achieved. This alleviates the stress concentration and early fracture problems that are easily caused by abrupt changes in stiffness at the welded joint of the blade in the existing structure, thereby significantly enhancing the impact toughness and structural reliability of the blade.

[0016] 3. By combining spiral roll bending in one step with curved surface stamping, the integrated, weld-free precision manufacturing of the three-dimensional spiral curved surface reinforcing rib structure is achieved, fundamentally eliminating the stress concentration and dynamic balance problems caused by traditional segmented forming. Furthermore, through the combination of deep cryogenic aging synergistic treatment and five-axis linkage cold grinding technology, the material's residual austenite is fully transformed and the processing stress is deeply released, while ensuring high-precision forming without thermal damage to the cutting edge. Ultimately, this results in a systematic improvement in the insert's dimensional stability, fatigue resistance, and wear resistance. Attached Figure Description

[0017] Figure 1 A schematic diagram of the overall structure of a deformation-resistant reinforcing rib structure for a rolling cutter. Figure 2 This is a schematic diagram of the cross-sectional structure of a deformation-resistant reinforcing rib structure for a rolling cutter.

[0018] In the diagram: 1. Central shaft; 2. Mounting disc; 3. Blade body; 4. Reinforcing rib. Detailed Implementation

[0019] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. Unless otherwise specified, the materials and equipment used in this embodiment are commercially available. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0020] Please refer to Figure 1-2 A deformation-resistant reinforcing rib structure for a hobbing cutter includes a central shaft 1, a mounting plate 2 fixed on the central shaft 1, and a cutter body 3 fixed on the mounting plate 2. The cutter body 3 is a three-dimensional helical curved cutter with a front and a back surface. The front surface is the working surface facing the cutting direction after installation, and the back surface is the non-working surface. The back surface is provided with reinforcing ribs 4 that extend continuously along the helical trajectory. The reinforcing ribs 4 have a height gradient along the width direction of the cutter body 3, and their height gradually decreases from the root of the cutter body 3 to the cutting edge. The two ends of the reinforcing ribs 4 terminate on the inner side of the axial end faces of the cutter body 3.

[0021] In a preferred embodiment of the present invention, the reinforcing rib 4 is a wave-shaped reinforcing rib that extends undulatingly along the spiral trajectory. It appears as a continuous sine wave on the planar projection of the blade body 3, so as to enhance the stress dispersion capability and suppress the crack propagation path.

[0022] In a preferred embodiment of the present invention, the cross-sectional height of the reinforcing rib 4 near the root of the blade body 3 is 1.5~2.0mm, and the cross-sectional height near the cutting edge of the blade body 3 is 0.6~1.0mm, forming a stiffness gradient distribution from the root to the cutting edge, effectively matching the stress distribution during the shearing process.

[0023] In a preferred embodiment of the present invention, the connection between the reinforcing rib 4 and the blade body 3 is provided with a rounded transition, and the radius of the rounded transition is not less than 0.4 times the thickness of the blade body 3, so as to avoid stress concentration and improve fatigue resistance.

[0024] In a preferred embodiment of the present invention, the blade body 3 has a thickness of 1.5~2.5mm and is made of 65Mn spring steel, which has good elastic recovery ability and wear resistance. Combined with the reinforcing rib structure, it achieves a balance between high rigidity and high toughness.

[0025] A method for manufacturing a deformation-resistant reinforcing rib structure for a hobbing cutter specifically includes the following steps: S1. Spheroidizing annealing: 65Mn spring steel strip is put into the furnace, held at 780℃ for 2 hours, then slowly reduced to 680℃ and held for 4 hours, and finally cooled to room temperature with the furnace to obtain a uniform spheroidized pearlite structure. S2, Spiral Roller Bending Forming: Annealed strip is fed into the spiral roller bending unit. The upper roller is precisely adjusted according to the target spiral angle and the axial feed speed is matched synchronously, so that the strip can continuously complete bending and axial displacement in the roller gap, forming a three-dimensional spiral curved surface blank in one step, without winding or welding throughout the process. S3. Curved surface fitting stamping: The blank is fixed in the copying fixture to maintain the spiral curved surface shape. The spiral curved surface matching punch is precision machined by five-axis CNC. Pressure is applied along the local normal of the blank to form a reinforcing rib 4 extending along the spiral line on the reverse side. A micro-dimple with a depth ≤0.1mm is naturally formed on the front side. S4. Fine finishing and shaping: Fine-tune the springback amount of the shaping mold to ensure that the measured value of the helix angle β is within ±0.5° tolerance; S5. Controlled atmosphere heat treatment: After holding at 920℃ in a vacuum furnace for 30 minutes, perform high-pressure quenching with 10MPa high-purity nitrogen, and then temper at 180℃ for 2 hours. S6, Five-axis linkage spiral cutting edge grinding: diamond grinding wheel single cutting depth ≤ 0.02mm, coolant flow rate ≥ 15L / min strong spray cooling; S7. Cryogenic aging treatment: Cryogenically cooled to -70℃ for 4 hours to promote the transformation of residual austenite and release stress, followed by aging at 150℃ for 2 hours to stabilize the microstructure. The dimensional change is <0.01mm within 72 hours after treatment. S8. Surface strengthening: TiAlN-PVD coating on the cutting edge area, and hard chrome plating on the non-working surface.

[0026] In a preferred embodiment of the present invention, the helical surface matching punch mentioned in step S3 is precisely milled / ground by a five-axis linkage CNC machine tool based on the three-dimensional helical surface theoretical model of the blade body 3. The working surface contour error is strictly controlled within 0.02mm to ensure that the reinforcing rib 4 is precisely conformal with the helical surface and free from torsional stress during stamping.

[0027] In a preferred embodiment of the present invention, the core of the cryogenic aging treatment described in step S7 lies in the synergistic effect of "cold treatment + hot aging" - firstly, the residual austenite is fully transformed and the residual stress of processing is released by cryogenic treatment at -70℃, and then the martensitic structure is stabilized by aging at 150℃.

[0028] In a preferred embodiment of the present invention, the thickness of the TiAlN-PVD coating in step S8 is 2~3μm, and the thickness of the hard chrome coating is 5~8μm.

[0029] When using this device, multiple blade bodies 3 are first securely welded onto the mounting plate 2. The mounting plate 2 is welded and fixed to the central shaft 1, thus forming a rotary blade assembly. The assembly is then assembled onto the frame of the rotary blade lawnmower. The central shaft 1 is connected to the drive motor. After starting the equipment, the motor drives the central shaft 1 to rotate at high speed, causing the blade bodies 3 to rotate synchronously. The grass stems enter the gap between the rotating blade body 3 and the fixed blade, and the front cutting edge completes precise cutting. During this process, the gradient height and wave-shaped structure of the reverse reinforcing rib 4 dynamically match the stiffness along the spiral path with the working load, effectively suppressing centrifugal deformation and grass stem impact vibration. The blade body 3, which has undergone deep cryogenic aging treatment, has excellent dimensional stability. Combined with the TiAlN-PVD coated cutting edge, the overall blade service life is extended by more than 35%, the cut smoothness is improved by 25%, and there is no risk of embrittlement in the welding heat-affected zone throughout the process. This solves the industry pain points of traditional rotary blades, such as easy deformation and short service life.

[0030] Although only certain components and embodiments of this application have been illustrated and described, many modifications and alterations (e.g., variations in the size, dimensions, structure, shape and proportion of the various elements, installation arrangement, material use, color, orientation, etc.) will be conceived by those skilled in the art without actually departing from the scope and spirit of the claims.

[0031] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A deformation-resistant reinforcing rib structure for a hobbing cutter, comprising a central shaft (1), a mounting plate (2) fixed on the central shaft (1), and a cutter body (3) fixed on the mounting plate (2), characterized in that: The blade body (3) is a three-dimensional spiral curved blade with a front and a back. The front is the working surface facing the cutting direction after installation, and the back is the non-working surface. The back is provided with a reinforcing rib (4) that extends continuously along the spiral trajectory. The reinforcing rib (4) has a height gradient along the width direction of the blade body (3), and its height gradually decreases from the root of the blade body (3) to the cutting edge. The two ends of the reinforcing rib (4) terminate on the inner side of the axial end faces of the blade body (3).

2. The deformation-resistant reinforcing rib structure of a hobbing cutter according to claim 1, characterized in that: The reinforcing rib (4) is a wave-shaped reinforcing rib that extends undulatingly along the spiral trajectory.

3. The deformation-resistant reinforcing rib structure of a hobbing cutter according to claim 2, characterized in that: The cross-sectional height of the reinforcing rib (4) near the root of the blade body (3) is 1.5~2.0mm, and the cross-sectional height near the cutting edge of the blade body (3) is 0.6~1.0mm.

4. The deformation-resistant reinforcing rib structure of a hobbing cutter according to claim 1, characterized in that: The connection between the reinforcing rib (4) and the blade body (3) is provided with a rounded transition, and the radius of the rounded transition is not less than 0.4 times the thickness of the blade body (3).

5. The deformation-resistant reinforcing rib structure of a hobbing cutter according to claim 1, characterized in that: The blade body (3) has a thickness of 1.5~2.5mm and is made of 65Mn spring steel.

6. A method for manufacturing a deformation-resistant reinforcing rib structure for a hobbing cutter according to any one of claims 1-5, characterized in that, Specifically, the following steps are included: S1. Spheroidizing annealing: 65Mn spring steel strip is put into the furnace, held at 780℃ for 2 hours, then slowly reduced to 680℃ and held for 4 hours, and finally cooled to room temperature with the furnace to obtain a uniform spheroidized pearlite structure. S2, Spiral Roller Bending Forming: Annealed strip is fed into the spiral roller bending unit. The upper roller is precisely adjusted according to the target spiral angle and the axial feed speed is matched synchronously, so that the strip can continuously complete bending and axial displacement in the roller gap, forming a three-dimensional spiral curved surface blank in one step, without winding or welding throughout the process. S3, Curved surface fitting stamping: The blank is fixed in the copying fixture to maintain the spiral curved surface shape. The spiral curved surface matching punch is precision machined by five-axis CNC. Pressure is applied along the local normal of the blank to form a reinforcing rib (4) extending along the spiral line on the reverse side. A micro-depression with a depth ≤0.1mm is naturally formed on the front side. S4. Fine finishing and shaping: Fine-tune the springback amount of the shaping mold to ensure that the measured value of the helix angle β is within ±0.5° tolerance; S5. Controlled atmosphere heat treatment: After holding at 920℃ in a vacuum furnace for 30 minutes, perform high-pressure quenching with 10MPa high-purity nitrogen, and then temper at 180℃ for 2 hours. S6, Five-axis linkage spiral cutting edge grinding: diamond grinding wheel single cutting depth ≤ 0.02mm, coolant flow rate ≥ 15L / min strong spray cooling; S7. Cryogenic aging treatment: Cryogenically cooled to -70℃ for 4 hours to promote the transformation of residual austenite and release stress, followed by aging at 150℃ for 2 hours to stabilize the microstructure. The dimensional change is <0.01mm within 72 hours after treatment. S8. Surface strengthening: TiAlN-PVD coating on the cutting edge area, and hard chrome plating on the non-working surface.

7. The manufacturing method according to claim 6, characterized in that: The helical surface matching punch mentioned in step S3 is made by precision milling / grinding of a five-axis linkage CNC machine tool based on the three-dimensional helical surface theoretical model of the blade body (3). The working surface contour error is strictly controlled within 0.02mm to ensure that the reinforcing rib (4) is precisely conformal with the helical surface and without torsional stress during stamping.

8. The manufacturing method according to claim 6, characterized in that: The core of the cryogenic aging treatment described in step S7 lies in the synergistic effect of "cold treatment + hot aging" - firstly, the residual austenite is fully transformed and the residual stress of processing is released by cryogenic treatment at -70℃, and then the martensitic structure is stabilized by aging at 150℃.

9. The manufacturing method according to claim 6, characterized in that: In step S8, the thickness of the TiAlN-PVD coating is 2~3μm, and the thickness of the hard chrome coating is 5~8μm.

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