A preparation method of an involute CBN grinding wheel

Abstract

This invention discloses a method for preparing an involute CBN grinding wheel, relating to the field of shaped grinding wheel manufacturing technology. The method includes steps such as designing involute tooth profile parameters, optimizing the geometric and proportioning parameters of the axial abrasive layer of the involute grinding wheel, mixing, curing, and assembling the abrasive layers of each segment along the axial direction of the involute grinding wheel, and laser dressing of the involute grinding wheel. This invention can adjust the proportioning coefficient of the mixed abrasive grains in each abrasive layer according to the material removal volume of each local area of ​​the gear tooth groove, making each segment of the abrasive layer more closely conform to the complex curved surface profile of the gear tooth groove. This mitigates the decrease in tooth profile accuracy caused by the non-uniform distribution of grinding load during the contact between the grinding wheel and the tooth surface, and promotes the wear consistency of the involute grinding wheel. Simultaneously, the optimized design of the abrasive layer composition in this invention can significantly improve the laser dressing efficiency and dressing accuracy of the grinding wheel, effectively reducing the maintenance cost of the involute grinding wheel.

Description

Technical Field

[0001] This invention relates to the field of shaped grinding wheel manufacturing technology, specifically to a method for manufacturing an involute CBN grinding wheel. Background Technology

[0002] Involute gears are key components in the transmission systems of industrial speed increasers, wind turbines, medical devices, and other equipment, playing a decisive role in the main functions, service life, reliability, and economic affordability of mechanical equipment. With the increasing demand for precision-machined involute gears, form grinding, as a commonly used gear finishing process, has gained widespread market attention and product application.

[0003] Form grinding involves dressing a grinding wheel to the required tooth profile of the part to be machined, and then using the dressed wheel to grind the tooth surface to obtain the desired tooth shape. However, due to the variable curvature of the involute tooth profile, the grinding force and temperature distribution of the grinding wheel in each profile segment are inconsistent, resulting in heterogeneous wear on the grinding wheel surface, which severely reduces the machining quality. Furthermore, the form grinding wheel is prone to wear during form grinding, requiring frequent dressing to maintain the original tooth profile, leading to a significant lack of machining continuity. These combined factors not only severely limit the improvement of involute gear machining efficiency but also introduce substantial errors into the form grinding process, ultimately resulting in unsatisfactory precision of the machined involute gears.

[0004] To improve the grinding quality and efficiency of profile grinding wheels in the gear grinding process from the perspective of profile grinding mechanism, it is necessary to improve the preparation process of superhard abrasive profile grinding wheels. Chinese invention patent CN111203594A discloses a method for grinding bevel gears using a disc-shaped grinding wheel, which improves the processing efficiency and accuracy of gears by utilizing the flexibility of CNC gear grinding machines. However, this method fails to fully consider the local contact geometry between the grinding wheel and the workpiece, as well as the variation law of the cumulative material removal volume along the involute gear tooth profile. It is difficult to formulate suitable abrasive layer formulation schemes for each segment of the involute gear tooth profile to solve the current technical problems in the profile grinding process.

[0005] This invention proposes a method for preparing an involute CBN grinding wheel, thereby improving the grinding performance of the involute grinding wheel and solving the problems of severe heterogeneous wear and low dressing efficiency of the grinding wheel during the forming grinding process. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention proposes a method for preparing an involute CBN grinding wheel. The method sets a suitable ratio coefficient of CBN abrasive particles of two different grit sizes according to the different material removal volumes of each segment of the involute tooth profile, so as to improve the overall wear resistance of the grinding wheel and promote the wear consistency of the shaped grinding wheel. The resulting grinding wheel can realize efficient shaped grinding of involute gears, with flexibility and precision.

[0007] Using spur involute gears as the workpiece, an involute CBN grinding wheel was designed. The preparation method adopted in this invention is as follows:

[0008] A method for preparing an involute CBN grinding wheel includes the following steps:

[0009] Step 1: Segmentation of the involute tooth profile; The tooth profile of the involute gear being machined includes the tooth root transition section and the involute segment; The tooth root transition section is divided according to the curvature K, and is further subdivided into a tooth root transition arc segment K>0, a tooth root transition arc segment K<0, and a tooth root straight line segment K=0; The involute segment is divided according to the involute rolling angle θ, and the unit rolling angle of the involute is set as... θ, and 0 < θ < π / 2;

[0010] Step 2: Determining the axial abrasive layer width of the involute grinding wheel; the abrasive layer width B corresponds to the tooth root transition arc segment of the involute CBN grinding wheel. W圆弧 The straight segment at the tooth root corresponds to the width B of the abrasive layer. W直线 The involute segment corresponds to the total width B of the abrasive layer. W渐开线 The width B of the transition arc segment at the tooth root of the involute gear 圆弧 , width B of the straight section at the tooth root 直线 The total width B of the involute segment 渐开线 The following relationship exists:

[0011]

[0012] Step 3: Design of the abrasive particle size ratio for the involute grinding wheel abrasive layer; During the forming grinding process, the local material removal volume of the involute tooth groove is V, which represents the material removal volume of the transition arc segment at the tooth root. 圆弧 Material removal volume V of the straight section at the root of the tooth 直线 and the volume V removed from the involute segment material 渐开线 , represented as:

[0013]

[0014]

[0015]

[0016] In the formula, a r a is the radial unit grinding feed depth of the grinding wheel. 圆弧 The normal unit grinding depth of the transition arc segment at the tooth root, a 直线 The normal unit grinding depth of the straight segment at the tooth root, a 渐开线 p represents the normal unit grinding depth of the involute segment. f β is the radius of the transition arc segment at the tooth root, β is the arc unfolding angle of the transition arc segment at the tooth root, and S is the thickness of the involute gear.

[0017] The abrasive of the grinding wheel contains two different grit sizes of CBN abrasive grains: coarse-grained CBN abrasive grains and fine-grained CBN abrasive grains; the abrasive grain density of the fine-grained CBN abrasive grains in each abrasive layer along the axial direction of the involute grinding wheel is X. 细粒度 The abrasive density of coarse-grained CBN abrasive grains in each abrasive layer along the axial direction of the involute grinding wheel is X. i-粗粒度 'i' represents the number of any profile segment. The abrasive density of fine-grained CBN abrasive grains is constant in each abrasive layer along the axial direction of the involute grinding wheel, while the abrasive density of coarse-grained CBN abrasive grains varies with the material removal volume of each abrasive layer. The abrasive density ratio X of the two different CBN abrasive grain sizes in the abrasive layer corresponding to the straight segment at the tooth root is set. 细粒度 :X 直线-粗粒度 The ratio of material removal volume to abrasive density in a sand profile segment is 1:1, and the following relationship exists between these ratios:

[0018] ;

[0019] Step 4: Preparation of abrasive layer composition for each profile segment of the involute grinding wheel; Based on the relationship between the material removal volume of each profile segment of the gear tooth groove and the density of the mixed particle size abrasive, the mixed particle size abrasive of each profile segment of the grinding wheel along the axial direction is prepared separately; the mixed particle size abrasives of different preparation ratios are stirred with a wetting agent to obtain abrasive mixtures of each profile segment of the involute grinding wheel along the axial direction with different preparation ratios; the light absorber, pore-forming agent and resin binder weighed according to the proportions are stirred to obtain a binder mixture; the binder mixture is stirred with abrasive mixtures of different preparation ratios to obtain abrasive layer materials of each profile segment of the involute grinding wheel along the axial direction with different mixed particle size abrasive ratios;

[0020] Step 5: Curing and assembling the abrasive layers of each profile segment along the axial direction of the involute grinding wheel; sequentially add the corresponding abrasive layer material of the involute gear tooth groove profile into the mold along the grinding wheel axis. After each layer of abrasive layer material of the profile segment is added, the abrasive layer is initially cured using a cold pressing process; after ensuring that each layer of grinding wheel abrasive layer material has been cold-pressed and cured, place the mold, grinding wheel base, and abrasive layer material together in an electric oven, and perform the final curing operation of the grinding wheel using hot pressing; after cooling to room temperature in the oven, remove the material, thereby obtaining an un-dressed parallel abrasive layer grinding wheel blank;

[0021] Step 6: Laser dressing of involute grinding wheel; The undressed parallel abrasive layer grinding wheel blank is dressed using pulsed laser ablation technology to prepare an involute CBN grinding wheel that conforms to the expected tooth groove profile of an involute gear.

[0022] Preferably, the transition arc segment at the tooth root corresponds to the abrasive layer width B. W圆弧 The width B of the transition arc segment at the tooth root 圆弧 The numerical values ​​are equal, and the straight segment at the tooth root corresponds to the abrasive layer width B. W直线 The width B of the straight segment at the tooth root 直线 The values ​​are equal; the involute segment in the involute CBN grinding wheel corresponds to the abrasive layer B. 渐开线 Composed of multiple involute profile segments, its width can be expressed as:

[0023]

[0024] In the formula, j represents the total number of divisions of the involute profile;

[0025] The involute CBN grinding wheel, in addition to including all the profile segments of the involute segments of the gear tooth grooves, also has additional involute extension segments in the abrasive layer, resulting in the total width B of the abrasive layer corresponding to the involute segments of the shaped grinding wheel. W渐开线 The involute segment width B is greater than the total width of the gear tooth groove. 渐开线 .

[0026] Preferably, the abrasive density ratio between mixed-size CBN abrasive grains is adjusted based on the local material removal volume of each profile segment of the involute gear tooth groove. The complementary advantages between two different CBN abrasive grains with different ratios effectively alleviate the heterogeneous grinding of the involute grinding wheel during the forming grinding process.

[0027] Preferably, the coarse-grained CBN abrasive grains and fine-grained CBN abrasive grains are two different grit sizes of CBN abrasive grains, defined relative to each other in terms of grain size. CBN abrasive grains with a larger average grain size are coarse-grained CBN abrasive grains, and CBN abrasive grains with a smaller average grain size are fine-grained CBN abrasive grains; the following grain size relationship exists between them:

[0028]

[0029] In the formula, the abrasive grain size of fine-grained CBN abrasive grains is C. 细粒度 The abrasive grain size of coarse-grained CBN abrasive grains is C 粗粒度 ξ is the particle size coefficient between fine-grained CBN abrasive grains and coarse-grained CBN abrasive grains.

[0030] Preferably, the mass percentage of each component in the involute CBN abrasive layer is: 40-60% mixed-size CBN abrasive grains, which include fine-grained and coarse-grained CBN abrasive grains, 20-40% resin binder, 5-10% light absorber, and 10-15% pore-forming agent.

[0031] Preferably, the resin binder is phenolic resin powder, which has good bonding strength, can improve the holding strength of abrasive grains in the grinding wheel abrasive layer, and can also impart good high temperature resistance and corrosion resistance.

[0032] Preferably, the light absorber is a Clear-weld light absorber, which can be used as an additive to the resin binder. After the Clear-weld light absorber is incorporated into the abrasive layer, it can enhance the absorption of near-infrared laser by the abrasive layer of the grinding wheel, improve the efficiency of laser dressing of the grinding wheel, and reduce the dressing cost of the grinding wheel.

[0033] Preferably, the pore-forming agent is made of hollow alumina spheres, which have good thermal stability, uniform shape, and produce smooth pores with an approximately spherical pore structure. Hollow alumina spheres can precisely control the size and distribution of pores in the grinding wheel, which is beneficial for adjusting the packing density of mixed abrasive particles and resin binder. They can also improve the cooling effect, chip removal capacity, and self-sharpening performance of the grinding wheel during the grinding process.

[0034] Preferably, the through hole at the center of the grinding wheel base can cooperate with the positioning cylinder at the center of the mold; during the process of adding abrasive material, the cooperation between the grinding wheel base and the mold can limit the displacement of the grinding wheel base under pressure or temperature conditions; the abrasive layer contact surface of the grinding wheel base is provided with multiple rectangular cross-section grooves, which helps to make the abrasive layer and the grinding wheel base more stable.

[0035] Preferably, in the process of adding abrasive material to each segment of the axial profile of the involute grinding wheel with different mixed particle size abrasive ratios, after each layer of abrasive material is added, the mold is tightened, the mold cap is fastened, and a cold pressing process is performed to initially solidify the abrasive layer. After the abrasive layer has been initially solidified, the process of adding subsequent abrasive material to the grinding wheel continues. This process of adding material and cold pressing is repeated until all abrasive material in all profile segments of the grinding wheel has been initially solidified. Then, the mold, the grinding wheel base, and the added abrasive material are hot-pressed to complete the final solidification and assembly of the grinding wheel.

[0036] After adopting the above preparation method, the variable ratio mixed particle size forming grinding wheel of the present invention for grinding involute gears has the following advantages compared with the prior art:

[0037] (1) Good processing performance. Compared with traditional involute grinding wheels, the present invention has made detailed differentiation of the involute profile to be ground, and formulated a suitable grinding wheel abrasive formulation scheme for the local material removal characteristics of each profile of the gear tooth groove. This helps to improve the non-homogeneous wear of traditional involute grinding wheels in form grinding, and significantly improves grinding accuracy and grinding efficiency.

[0038] (2) Wide range of applications. The volume change of material removal in the tooth groove can be judged according to the number of teeth and module of the actual involute gear grinding, and then the mixing ratio coefficient of the mixed abrasive particles can be adjusted to achieve the combined effect of coarse abrasive particles to efficiently remove materials and fine abrasive particles to improve surface quality. The service performance of the forming grinding wheel is greatly improved for different material removal requirements in each profile area.

[0039] (3) High dressing efficiency. The light absorber added to the abrasive layer of the grinding wheel can reduce the reflection and transmission of laser on the surface of the grinding wheel, and can more effectively transfer laser energy to the surface of the grinding wheel. This helps to evenly and stably disperse the laser energy on the surface of the grinding wheel, thereby improving the dressing efficiency of the grinding wheel. The light absorber after dressing will solidify in the contact gap between the abrasive and the binder, which will improve the holding strength of the abrasive on the working surface of the grinding wheel and help control the subsequent maintenance cost of the formed grinding wheel.

[0040] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0041] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0042] Figure 1 This is a schematic diagram of grinding with an involute CBN grinding wheel;

[0043] Figure 2 A schematic diagram showing the comparison between the abrasive layer and the involute tooth groove profile of the parallel abrasive layer grinding wheel blank in each axis;

[0044] Figure 3 A schematic diagram of the grinding wheel feed depth during the forming grinding of involute tooth grooves;

[0045] Figure 4 A flow chart showing the material mixing process of the abrasive layers in the axially segmented profiles of the parallel abrasive layer grinding wheel blank.

[0046] Figure 5 A schematic diagram showing the curing of a parallel abrasive layer grinding wheel blank in a mold;

[0047] Figure 6 This is an exploded view of an involute CBN grinding wheel after pulsed laser dressing. Detailed Implementation

[0048] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0049] The preparation method adopted in this invention is as follows:

[0050] Step 1: Segmentation of the involute tooth profile. The tooth profile of the involute gear to be machined includes the tooth root transition section and the involute segment. The tooth root transition section can be divided according to the curvature K, and can be further subdivided into a tooth root transition arc segment K>0, a tooth root transition arc segment K<0, and a tooth root straight line segment K=0. The involute segment can be divided according to the involute rolling angle θ, where the unit rolling angle of the involute is set as... θ, and 0 < θ < π / 2. The abrasive layer of the designed involute CBN grinding wheel can be divided in the axial direction into the abrasive layer corresponding to the tooth root transition arc segment, the abrasive layer corresponding to the tooth root straight segment, and the abrasive layer corresponding to the involute segment.

[0051] Step 2: Confirmation of the axial abrasive layer width of the involute grinding wheel. The width B of the transition arc segment at the tooth root of the involute gear. 圆弧 , width B of the straight section at the tooth root 直线 Involute segment width B 渐开线 It can be represented as:

[0052]

[0053]

[0054]

[0055]

[0056] In the formula: p f Let be the radius of the transition arc segment at the tooth root, β be the arc unfolding angle of the transition arc segment at the tooth root, j be the total number of involute segments, and B be the radius of the transition arc segment at the tooth root. 渐开线-分度圆 r is the width of the involute segment at the intersection of the pitch circle and the involute segment. 起始 Let r be the radius at the starting point of the involute segment. 结束 Let η be the radius at the endpoint of the segment of the involute. 起始 η is the half-angle of the tooth center at the starting point of the involute segment segment. 起始 It is the half-angle of the tooth groove center at the end point of the segmentation of the involute.

[0057] The involute CBN grinding wheel's tooth root transition arc segment corresponds to the abrasive layer width B. W圆弧 The straight segment at the tooth root corresponds to the width B of the abrasive layer. W直线 The involute segment corresponds to the total width B of the abrasive layer. W渐开线 The width B of the transition arc segment at the tooth root of the involute gear 圆弧 , width B of the straight section at the tooth root 直线 Involute segment width B 渐开线 The following relationship exists between them:

[0058]

[0059] The transition arc segment at the tooth root corresponds to the abrasive layer width B. W圆弧 The width B of the transition arc segment at the tooth root 圆弧 The numerical values ​​are equal, and the straight segment at the tooth root corresponds to the abrasive layer width B. W直线 The width B of the straight segment at the tooth root 直线 The values ​​are equal. The abrasive layer corresponding to the involute segment includes all the profile segments of the involute segment of the gear tooth groove, and also has additional involute extension segments. This makes the total width of the abrasive layer corresponding to the involute segment of the forming grinding wheel greater than the total width of the involute segment of the gear. This ensures that the feed of the involute segment grinding wheel has a margin during forming grinding to meet the processing requirements of the modified gear.

[0060] Step 3: Design of the abrasive particle size distribution in the involute grinding wheel abrasive layer. Two different CBN abrasive particle sizes from GB2477-83 "Abrasive Particle Size and Composition" are mixed and uniformly distributed within the grinding wheel abrasive layer. The grinding wheel abrasive includes coarse-grained and fine-grained CBN abrasive particles. To increase the material removal volume during a single grinding cycle, coarse-grained CBN abrasive particles are incorporated into the fine-grained CBN abrasive particle group to expand the effective abrasive particle volume during a single grinding cycle. The following particle size relationship exists between the fine-grained and coarse-grained CBN abrasive particles:

[0061]

[0062] In the formula, the abrasive grain size of fine-grained CBN abrasive grains is C. 细粒度 The abrasive grain size of coarse-grained CBN abrasive grains is C 粗粒度 ξ is the particle size coefficient between fine-grained CBN abrasive grains and coarse-grained CBN abrasive grains.

[0063] Because the gear profile surface is curved, the normal grinding depth varies for each profile segment of the involute gear tooth groove, resulting in different local material removal volumes for each tooth groove profile segment. During the form grinding process, the radial unit grinding feed depth of the grinding wheel is set to a. r The normal unit grinding depth of the transition arc segment at the tooth root is a. 圆弧 The normal unit grinding depth of the straight segment at the tooth root is a. 直线 The normal unit grinding depth of the involute segment is a. 渐开线 The thickness of the involute gear is S, and the material removal volume of the transition arc segment at the tooth root is V. 圆弧 Material removal volume V of the straight section at the root of the tooth 直线 and the volume V removed from the involute segment material 渐开线 It can be represented as:

[0064]

[0065]

[0066]

[0067] The abrasive density of fine CBN abrasive grains in each abrasive layer along the axial direction of the involute grinding wheel is X. 细粒度 The abrasive density of the fine-grained CBN abrasive grains is equal in all abrasive layers. The abrasive density of the coarse-grained CBN abrasive grains in each abrasive layer along the axial direction of the involute grinding wheel is X. i-粗粒度 'i' represents the number of any profile segment, and the abrasive density value of the coarse-grained CBN abrasive grains varies with the material removal volume of each abrasive layer. The abrasive density ratio X of the two different CBN abrasive grain sizes in the abrasive layer is defined as corresponding to the straight segment at the tooth root. 细粒度 :X 直线-粗粒度 The ratio of material removal volume to abrasive density in a sand profile segment is 1:1, and the following relationship exists between these ratios:

[0068]

[0069] In the involute CBN grinding wheel, the abrasive density of fine-grained CBN abrasive grains in each axial abrasive layer is constant, while the abrasive density of coarse-grained CBN abrasive grains varies with the local material removal volume of each profile segment of the involute gear tooth groove under the normal unit grinding depth condition.

[0070] Step 4: Preparation of abrasive layer components for each segment along the axial direction of the involute CBN grinding wheel. The mass percentage of each component in the abrasive layer material of the involute CBN grinding wheel is as follows: 40~60% mixed-size CBN abrasive grains, including fine and coarse CBN abrasive grains; 20~40% resin binder; 5~10% light absorber; and 10~15% pore-forming agent.

[0071] Before mixing the abrasive layer materials, the abrasive particles are pretreated. Fine-grained and coarse-grained CBN abrasive particles are screened using a sieve to improve the content and uniformity of the basic abrasive particles. Based on the relationship between the material removal volume of each contour segment of the gear tooth groove and the density of the mixed-size abrasive particles, the mixed-size abrasive particles for each segment of the abrasive layer along the grinding wheel axis are formulated. Abrasive particles of different formulations are mixed with a wetting agent in a high-power mixer to obtain mixtures of abrasive particles from each contour segment of the involute grinding wheel axis with different formulations. The wetting agent is liquid phenolic resin, whose components are included in the resin binder. The liquid phenolic resin enables the binder to adhere more evenly to the abrasive particle surface, ensuring strong holding force for the mixed-size abrasive particles in the abrasive layer. The light-absorbing agent, pore-forming agent, and resin binder, weighed according to the specified proportions, are stirred in a high-power mixer to obtain a binder mixture. The phenolic resin binder is phenolic resin powder, and the light absorber is Clear-weld light absorber. Clear-weld light absorber has a good absorption effect on near-infrared laser (800-1100nm), which can improve the efficiency of laser removal of abrasive grains and binder from the grinding wheel surface, improve the efficiency of subsequent grinding wheel dressing, and save laser dressing costs. The pore-forming agent is alumina hollow spheres, which have controllable particle size and uniform shape, and can improve the self-sharpening property and chip-holding capacity of the grinding wheel. The binder mixture and abrasive grain mixtures of different formulations are put into a high-power mixer for stirring. After mixing, the abrasive layer material is sieved and set aside for later use.

[0072] Step 5: Curing and assembling the segmented abrasive layers along the axial direction of the involute grinding wheel. To ensure a more stable fit between the grinding wheel substrate and the abrasive layers, the grinding wheel substrate is pre-cleaned and fixed in a mold. Abrasive layer material corresponding to the involute gear tooth profile is added sequentially to the mold along the grinding wheel axis. After each layer of segmented abrasive layer material is added, a cold-pressing process is used for preliminary curing. Once each abrasive layer has been cold-pressed and cured, the mold, grinding wheel substrate, and abrasive layer material are placed together in an electric oven for final curing using hot pressing. After cooling to room temperature in the oven, the material is removed, resulting in an un-dressed parallel abrasive layer grinding wheel blank.

[0073] Step 6, Laser Dressing of the Involute Grinding Wheel. A pulsed laser ablation process is used to dress the undressed parallel abrasive layer grinding wheel blank. First, a pulsed laser is incident on the working surface of the grinding wheel along the involute ablation trajectory at the tangential direction to perform laser shaping. Then, a pulsed laser is incident on the working surface of the grinding wheel at the normal direction to perform laser sharpening, ensuring that the mixed-size CBN abrasive grains all have a certain cutting edge height on the working surface of the grinding wheel. Finally, an involute CBN grinding wheel conforming to the expected tooth profile of an involute gear is prepared.

[0074] Example 1

[0075] As attached Figure 1 As shown, in this embodiment, a spur involute gear is used as the workpiece to be machined. Based on the change in the material removal volume of the workpiece along the tooth groove contour, a method for preparing an involute CBN grinding wheel is proposed. The preparation method of this grinding wheel is as follows:

[0076] Step 1: Dividing the involute tooth profile into segments. (See attached image) Figure 2 As shown, the tooth profile of the involute gear 1 includes a tooth root transition arc segment 11, a tooth root straight line segment 12, and an involute segment 13. The involute segment 13 can be divided according to the involute rolling angle θ, where the unit rolling angle of the involute is... θ, and 0 < θ < π / 2. The light-absorbing enhanced modified-ratio mixed particle size involute CBN grinding wheel prepared is a parallel abrasive layer grinding wheel blank 2 before dressing. To address the different profiles of the involute gear tooth grooves, a corresponding abrasive layer is established in the axial direction of the parallel abrasive layer grinding wheel blank 2. This avoids heterogeneous wear of the grinding wheel caused by local feed rate differences, extends the service life of the involute grinding wheel, and maintains the profile accuracy during grinding. The parallel abrasive layer grinding wheel blank 2 corresponding to the tooth groove profile of the involute gear 1 includes an abrasive layer 21 corresponding to the tooth root transition arc segment, an abrasive layer 22 corresponding to the tooth root straight segment, and an abrasive layer 23 corresponding to the involute segment. In this example, the processed involute gear has a module m of 8, a number of teeth z of 51, and a unit roll angle of the involute. θ is 1°, and the involute segment is planned to be divided into 4 layers.

[0077] Step 2: Confirmation of the axial abrasive layer width of the involute grinding wheel. The width B of the tooth root transition arc segment 11 of the involute gear 1. 圆弧 12 width B of the straight segment at the tooth root 直线 Involute segment 13, width B 渐开线 The following relationship exists:

[0078]

[0079]

[0080]

[0081]

[0082] In the formula: p f Let be the radius of the transition arc segment at the tooth root, β be the arc unfolding angle of the transition arc segment at the tooth root, j be the total number of involute segments, and B be the radius of the transition arc segment at the tooth root. 渐开线-分度圆 r is the width of the involute segment at the intersection of the pitch circle and the involute segment. 起始 Let r be the radius at the starting point of the involute segment. 结束 Let η be the radius at the endpoint of the segment of the involute. 起始 η is the half-angle of the tooth center at the starting point of the involute segment segment. 起始 The center half-angle of the tooth groove at the end point of the involute segment segment. In this case, the total number of involute segments j=4, and the arc development angle β of the tooth root transition arc segment is 77°.

[0083] The tooth root transition arc segment of the parallel abrasive layer grinding wheel blank 2 corresponds to the width B of the abrasive layer 21. W圆弧 The straight segment at the tooth root corresponds to the width B of the abrasive layer 22. W直线 The involute segment corresponds to the width B of the abrasive layer 23. W渐开线 The width B of the transition arc segment 11 at the tooth root of the involute gear 1 圆弧 12 width B of the straight segment at the tooth root 直线 Involute segment 13, width B 渐开线 The following relationship exists between them:

[0084]

[0085] The transition arc segment at the tooth root corresponds to the width B of the abrasive layer 21. W圆弧 Width B of the transition arc segment 11 at the tooth root 圆弧 The values ​​are equal, and the straight segment at the tooth root corresponds to the width B of the abrasive layer 22. W直线 Width B of the straight segment 12 at the tooth root 直线 The values ​​are equal. The abrasive layer 23 corresponding to the involute segment includes all segments of the involute segment 13, and also has additional involute extension segments. Therefore, the total width of the abrasive layer 23 corresponding to the involute segment is greater than the total width of the involute segment 13. This ensures that the involute segment grinding wheel still has a feed margin during profile grinding to meet the machining requirements of the modified gear.

[0086] Step 3: Design of the abrasive grain size ratio for the involute grinding wheel abrasive layer. The grinding wheel abrasive layer contains fine-grained CBN abrasive grains and coarse-grained CBN abrasive grains. Two different CBN abrasive grain sizes from GB2477-83 "Abrasive Grain Size and Composition" are mixed and evenly distributed within the grinding wheel abrasive layer, leveraging the complementary advantages of the high wear resistance of the coarse grains and the finishing properties of the fine grains. This not only improves the wear resistance between the abrasive grains and increases grinding efficiency, but also reduces the need to change grinding wheels at different grinding stages, and saves costs. The fine-grained CBN abrasive grains 3 and coarse-grained CBN abrasive grains 4 have the following grain size relationship:

[0087]

[0088] In the formula, the abrasive grain size of fine-grained CBN abrasive grains is C. 细粒度 The abrasive grain size of coarse-grained CBN abrasive grains is C 粗粒度 ξ is the particle size coefficient between fine-grained CBN abrasive grains and coarse-grained CBN abrasive grains. In this embodiment, the particle size of the fine-grained CBN abrasive grains is 120 μm, and the particle size of the coarse-grained CBN abrasive grains is 180 μm.

[0089] As attached Figure 4 As shown, since the gear tooth groove has a complex curved profile, the normal unit grinding depth a of the tooth root transition arc segment 11 is... 圆弧 The normal unit grinding depth a of the straight segment 12 at the tooth root 直线 and the normal unit grinding depth a of involute segment 13 渐开线 The differences between these factors result in varying amounts of material removed from different tooth profile segments under the condition of a unit radial grinding feed depth of the grinding wheel. During the profile grinding of the involute gear 1, the unit radial grinding feed depth of the grinding wheel is set to a. r The thickness of the involute gear is S, and the material removal volume V of the transition arc segment 11 at the tooth root is... 圆弧 12 Material removal volume V of straight segment at the tooth root 直线 and the volume V of material removal from involute segment 13 渐开线 The following relationship exists between them:

[0090]

[0091]

[0092]

[0093] The abrasive density of the fine-grained CBN abrasive grains in each profile segment of the axial section of the involute grinding wheel is X. 细粒度The abrasive density of the fine-grained CBN abrasive grains is equal in each abrasive layer. The abrasive density of the coarse-grained CBN abrasive grains in each profile segment of the axial section of the involute grinding wheel is X. i-粗粒度 'i' represents the number of any contour segment, and the abrasive density value of the coarse-grained CBN abrasive grains varies with the material removal volume of each abrasive layer. The abrasive density ratio X of the fine-grained CBN abrasive grains and the coarse-grained CBN abrasive grains in abrasive layer 22 is set to correspond to the straight segment at the tooth root. 细粒度 :X 直线-粗粒度 The ratio of material removal volume to abrasive density in a sand profile segment is 1:1, and the following relationship exists between these ratios:

[0094]

[0095] The abrasive density ratio of fine-grained CBN abrasive grains in each profile segment of the involute grinding wheel along the axial direction is used as a benchmark to establish the relationship between the material removal volume of each profile segment during grinding and the ratio coefficient of CBN abrasive grains of two different grit sizes, thereby achieving controllable preparation of mixed-size abrasive grains in the abrasive layer.

[0096] Step 4: Preparation of abrasive layer components for each profile segment along the axial direction of the involute grinding wheel. The mass percentage of each component in the abrasive layer of the parallel abrasive layer grinding wheel blank 2 is as follows: 40-60% mixed-size CBN abrasive grains, including fine-grained and coarse-grained CBN abrasive grains, 20-40% resin binder, 5-10% light absorber, and 10-15% pore-forming agent.

[0097] As attached Figure 5As shown, the components in the abrasive layer of the grinding wheel are mixed sequentially. The abrasive grains are pretreated before mixing. Fine-grained CBN abrasive grains and coarse-grained CBN abrasive grains are screened using a sieve to improve the content and uniformity of the basic abrasive particles. The screened fine-grained and coarse-grained CBN abrasive grains are placed in alcohol and ultrasonically cleaned 3-4 times, 5 minutes each time, to remove dust, oil, and other impurities from the abrasive grain surface. The cleaned abrasive grains are then dried in a dryer. Based on the abrasive density ratio of fine-grained and coarse-grained CBN abrasive grains described in step three, the mixed particle size abrasive grains for each profile segment of the abrasive layer along the axial direction of the grinding wheel are separately formulated for subsequent mixing. Abrasive grains of different formulations are mixed with a wetting agent in a high-power mixer for 4-5 hours to obtain mixtures of abrasive grains for each profile segment of the involute grinding wheel with different formulations. The wetting agent is selected as liquid phenolic resin, and its components are incorporated into the resin binder in a specific proportion. Liquid phenolic resin enables the binder to adhere more uniformly to the abrasive grain surface, ensuring strong holding force for abrasive grains of mixed sizes within the abrasive layer. The light absorber, pore-forming agent, and resin binder, weighed according to the specified proportions, are mixed in the same direction for 2-3 hours using a high-power mixer to obtain the binder mixture. The phenolic resin binder is selected as phenolic resin powder, which has excellent adhesion. The light absorber is selected as Clear-weld light absorber, which has good absorption of near-infrared (800-1100 nm) laser light and can be incorporated into the phenolic resin binder. The pore-forming agent is selected as hollow alumina spheres, which have controllable particle size and uniform shape, improving the self-sharpening performance and chip-holding capacity of the grinding wheel. The binder mixture and abrasive mixtures with different proportions are placed into a high-power mixer and stirred in the same direction for 3-5 hours at 600 r / min to obtain abrasive layers of different profiles along the axial direction of the involute grinding wheel with different abrasive particle size ratios. After sieving, the abrasive layers are set aside for later use.

[0098] Step 5: The abrasive layers of each axial profile segment of the involute grinding wheel are cured and assembled. (See attached image.) Figure 5 As shown, the abrasive layer of the grinding wheel is cured and assembled in segments according to the axial profile in mold 3. For this purpose, the grinding wheel substrate 4 needs to be pre-treated. The grinding wheel substrate 4 is annular in shape with a through hole 41 at its center to facilitate assembly between the grinding wheel and the machine tool. The abrasive layer contact surface 42 of the grinding wheel substrate 4 has multiple rectangular grooves, which helps to ensure a more stable fit between the abrasive layer and the grinding wheel substrate. The grinding wheel substrate 4 is cleaned with xylene, dried, and then left to stand for later use. The mold 3 is annular in shape with a positioning cylinder 31 at its center that engages with the through hole 41 of the grinding wheel substrate 4.

[0099] The grinding wheel base 4 is placed in the mold 3 beforehand to ensure a firm bond between the grinding wheel base 4 and the abrasive layer material. The mixed abrasive layer material for each segment of the grinding wheel is then added to the mold 3 sequentially according to the designed width of each segment of the parallel abrasive layer grinding wheel blank 2 as described in step two. After each segment of the abrasive layer material is added to the grinding wheel profile, the mold 3 is tightened, and the mold cap 5 is fastened, with a (17-20)×10... 5 The abrasive layer is initially cured by cold pressing under pressure of Pa. After the abrasive layer has been initially cured, the abrasive material for subsequent profile segments of the grinding wheel is added. This feeding-cold pressing process is repeated until all profile segments of the grinding wheel have been initially cured. The initially cured grinding wheel blank and mold are then placed in an electric oven at a temperature of 180-200℃ and a pressure of (300-700)×10. 5 Pa hot-presses the grinding wheel. After the adjacent abrasive layers are tightly bonded together and the abrasive layer is tightly bonded to the grinding wheel substrate, the wheel is cooled to room temperature and hardened for 10-30 hours in the furnace before being discharged, thus obtaining an un-dressed parallel abrasive layer grinding wheel blank 2.

[0100] Step 6, Laser Dressing of the Involute Grinding Wheel. A pulsed laser ablation process is used to dress the parallel abrasive layer grinding wheel blank 2, achieving non-contact, efficient, and high-precision dressing of the involute grinding wheel. First, a pulsed laser is incident on the working surface of the grinding wheel along the involute ablation trajectory at the tangential direction, shaping the parallel abrasive layer grinding wheel blank 2. Then, a pulsed laser is incident on the working surface of the grinding wheel at the normal direction, sharpening the shaped grinding wheel to ensure that the mixed-size CBN abrasive grains all have a certain cutting edge height on the working surface of the grinding wheel. Finally, an involute CBN grinding wheel conforming to the expected tooth profile of an involute gear is prepared. In this case, the laser used for dressing is a nanosecond pulsed laser with an average power of 60-80W, a laser scanning rate of 0.01-0.2mm / s, and a pulse frequency of 50kHz.

[0101] During laser dressing, the laser radiation is absorbed by the Clear-weld absorber in the binder, improving the laser's efficiency in removing abrasive grains and the binder from the grinding wheel surface. As the laser radiation is gradually absorbed and converted into heat energy by the Clear-weld absorber, the Clear-weld absorber near the radiation area is heated to the point of melting. The Clear-weld absorber incorporated into the resin binder exists in a free state, providing additional chip-holding space for the grinding wheel's working surface. After the laser spot moves away from the radiation area, the free Clear-weld absorber will solidify again in the joint between the abrasive grains and the binder, improving the abrasive layer's ability to hold the abrasive grains.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing an involute CBN grinding wheel, characterized in that, Includes the following steps: Step 1: Segmentation of the involute tooth profile; The tooth profile of the involute gear to be machined includes a tooth root transition section and an involute segment; The tooth root transition section is divided according to the curvature K, and is further subdivided into a tooth root transition arc segment K>0, a tooth root transition arc segment K<0, and a tooth root straight line segment K=0; The involute segment is divided according to the involute rolling angle θ, and the unit rolling angle of the involute is set as... θ, and 0 < θ < π / 2; Step 2: Determining the axial abrasive layer width of the involute grinding wheel; the abrasive layer width B corresponds to the tooth root transition arc segment of the involute CBN grinding wheel. W圆弧 The straight segment at the tooth root corresponds to the width B of the abrasive layer. W直线 The involute segment corresponds to the total width B of the abrasive layer. W渐开线 The width B of the transition arc segment at the tooth root of the involute gear 圆弧 , width B of the straight section at the tooth root 直线 The total width B of the involute segment 渐开线 The following relationship exists between them: Step 3: Design of the abrasive particle size ratio for the involute grinding wheel abrasive layer; During the forming grinding process, the local material removal volume of the involute tooth groove is V, which represents the material removal volume of the transition arc segment at the tooth root. 圆弧 Material removal volume V of the straight section at the root of the tooth 直线 and the volume V removed from the involute segment material 渐开线 , represented as: In the formula, a r a is the radial unit grinding feed depth of the grinding wheel. 圆弧 The normal unit grinding depth of the transition arc segment at the tooth root, a 直线 The normal unit grinding depth of the straight segment at the tooth root, a 渐开线 p represents the normal unit grinding depth of the involute segment. f β is the radius of the transition arc segment at the tooth root, β is the arc unfolding angle of the transition arc segment at the tooth root, and S is the thickness of the involute gear. The grinding wheel contains mixed-size abrasive grains of two different CBN abrasive grains: coarse-grained CBN abrasive grains and fine-grained CBN abrasive grains. The abrasive grain density of the fine-grained CBN abrasive grains in each abrasive layer along the axial direction of the involute grinding wheel is X. 细粒度 The abrasive density of coarse-grained CBN abrasive grains in each abrasive layer along the axial direction of the involute grinding wheel is X. i-粗粒度 'i' represents the number of any profile segment. The abrasive density of fine-grained CBN abrasive grains is constant in each abrasive layer along the axial direction of the involute grinding wheel, while the abrasive density of coarse-grained CBN abrasive grains varies with the material removal volume of each abrasive layer. The abrasive density ratio X of the two different CBN abrasive grain sizes in the abrasive layer corresponding to the straight segment at the tooth root is set. 细粒度 :X 直线-粗粒度 The ratio of material removal volume to abrasive density in a sand profile segment is 1:1, and the following relationship exists between these ratios: ； Step 4: Preparation of abrasive layer composition for each axial profile segment of the involute grinding wheel; Based on the relationship between the material removal volume of each profile segment of the gear tooth groove and the density of the mixed particle size abrasive, the mixed particle size abrasive of each axial profile segment of the grinding wheel is prepared separately; the mixed particle size abrasives of different preparation ratios are stirred with a wetting agent to obtain abrasive mixtures of each axial profile segment of the involute grinding wheel with different preparation ratios; the light absorber, pore-forming agent and resin binder are weighed according to the proportions and stirred to obtain a binder mixture; the binder mixture is stirred with the abrasive mixtures of each axial profile segment of the involute grinding wheel with different preparation ratios to obtain abrasive layer materials of each axial profile segment of the involute grinding wheel with different mixed particle size abrasive ratios; Step 5: Curing and assembling the abrasive layers of each profile segment along the axial direction of the involute grinding wheel; sequentially add the corresponding abrasive layer material of the involute gear tooth groove profile into the mold along the axial direction of the grinding wheel. After each layer of abrasive material is added, the abrasive layer is initially cured using a cold pressing forming process. After ensuring that each abrasive layer of the grinding wheel has been cold-pressed and cured, the mold, grinding wheel base, and abrasive layer material are placed together in an electric oven, and the grinding wheel is finally cured by hot pressing. After cooling to room temperature in the oven, the material is removed, thus obtaining an untrimmed parallel abrasive layer grinding wheel blank. Step 6: Laser dressing of involute grinding wheel; The undressed parallel abrasive layer grinding wheel blank is dressed using pulsed laser ablation technology to prepare an involute CBN grinding wheel that conforms to the expected tooth groove profile of an involute gear.

2. The method for preparing an involute CBN grinding wheel according to claim 1, characterized in that, The transition arc segment at the tooth root corresponds to the abrasive layer width B. W圆弧 The width B of the transition arc segment at the tooth root 圆弧 The numerical values ​​are equal, and the straight segment at the tooth root corresponds to the abrasive layer width B. W直线 The width B of the straight segment at the tooth root 直线 The values ​​are equal; the abrasive layer corresponding to the involute segment in the involute CBN grinding wheel is composed of multiple involute profile segments, and its width can be expressed as: In the formula, j represents the total number of divisions of the involute profile; The involute segment of the CBN grinding wheel corresponds to an abrasive layer that includes all the profile segments of the involute segment of the gear tooth groove, and also has additional involute extension segments, resulting in a total width B of the abrasive layer corresponding to the involute segment of the forming grinding wheel. W渐开线 The involute segment width B is greater than the total width of the gear tooth groove. 渐开线 .

3. The method for preparing an involute CBN grinding wheel according to claim 1, characterized in that, The abrasive density ratio of mixed-size CBN abrasive grains is adjusted based on the local material removal volume of each profile segment of the involute gear tooth groove. The complementary advantages between two different CBN abrasive grains with different abrasive density ratios effectively alleviate the heterogeneous grinding of the involute grinding wheel during the forming grinding process.

4. The method for preparing an involute CBN grinding wheel according to claim 1, characterized in that, The coarse-grained and fine-grained CBN abrasives are defined as two different grit sizes of CBN abrasives. The terms "coarse-grained" and "fine-grained" are relative definitions in terms of particle size. CBN abrasives with a larger average particle size are coarse-grained CBN abrasives, and CBN abrasives with a smaller average particle size are fine-grained CBN abrasives. The following particle size relationship exists between them: In the formula, the abrasive grain size of fine-grained CBN abrasive grains is C. 细粒度 The abrasive grain size of coarse-grained CBN abrasive grains is C 粗粒度 ξ is the particle size coefficient between fine-grained CBN abrasive grains and coarse-grained CBN abrasive grains.

5. The method for preparing an involute CBN grinding wheel according to claim 1, characterized in that, The mass percentage of each component in the involute CBN abrasive layer is as follows: 40-60% mixed-size CBN abrasive grains, which include fine-grained and coarse-grained CBN abrasive grains; 20-40% resin binder; 5-10% light absorber; and 10-15% pore-forming agent.

6. The method for preparing an involute CBN grinding wheel according to claim 1, characterized in that, The resin binder is phenolic resin powder, which has good bonding strength, can improve the holding strength of abrasive grains in the grinding wheel abrasive layer, and can also give the grinding wheel good high temperature resistance and corrosion resistance.

7. The method for preparing an involute CBN grinding wheel according to claim 1, characterized in that, The light absorber selected is Clear-weld light absorber, which can be used as an additive to the resin binder. After being incorporated into the abrasive layer, Clear-weld light absorber can enhance the absorption of near-infrared laser by the abrasive layer of the grinding wheel, improve the efficiency and accuracy of laser dressing of the grinding wheel, and reduce the dressing cost of the grinding wheel.

8. The method for preparing an involute CBN grinding wheel according to claim 1, characterized in that, The pore-forming agent is made of hollow alumina spheres. Hollow alumina spheres can precisely control the size and distribution of pores in the grinding wheel, which is beneficial for adjusting the packing density of mixed abrasive particles and resin binder. It can improve the cooling effect, chip removal capacity and self-sharpening performance of the grinding wheel during grinding.

9. The method for preparing an involute CBN grinding wheel according to claim 1, characterized in that, The through hole at the center of the grinding wheel base can mate with the positioning cylinder at the center of the mold; during the addition of abrasive material, this mating can limit the displacement of the grinding wheel base under pressure or temperature conditions; the abrasive layer contact surface of the grinding wheel base is provided with multiple rectangular cross-section grooves, which helps to achieve a more stable bond between the abrasive layer and the grinding wheel base.

10. The method for preparing an involute CBN grinding wheel according to claim 1, characterized in that, In the process of adding abrasive material to the axial profile segments of involute grinding wheels with different mixed particle size abrasive ratios, after each layer of abrasive material is added, the mold is tightened, the mold cover is fastened, and a cold pressing process is carried out to initially solidify the abrasive layer. After the abrasive layer has initially cured, continue adding abrasive material to the subsequent profile segments of the grinding wheel. Repeat this adding-cold-pressing process until all profile segments of the grinding wheel have initially cured. Then, hot-press the mold, grinding wheel base, and the added abrasive material to each segment to complete the final curing and assembly of the grinding wheel. During the addition of abrasive material, it is necessary to avoid cross-contamination between adjacent axial profile segments of the abrasive layer in the uncured stage, which would cause a chaotic distribution ratio of mixed abrasive particles and affect the accuracy of the involute tooth profile processed by the formed grinding wheel.

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