Search

Copyright of Journal of Xi'an Jiaotong University is the property of Editorial Office of Journal of Xi'an Jiaotong University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A method is proposed for determining the cut-layer dimensions in tooth milling by modular hobs, on the basis of graphical CAD software. The cutting trajectory of each tooth is determined, with successive drawing of each trajectory, after Boolean subtraction of the cut metal. By this method, the optimal cutting parameters may be determined, the required tool material may be selected, and the machining cost may be greatly reduced. [ABSTRACT FROM AUTHOR]

Gear drives are widely used in various fields and applications due to their properties and capacity. Their versatility, durability, and ability to transmit high torques as well as precision and reliability make them extremely useful in many fields of technology. They are widely used in industrial and energy machinery, vehicle drive systems, aerospace, medical devices, and many other areas. Gears can be manufactured using many technologies. This work focuses mainly on machining with particular emphasis on high-performance new technologies. The process of mathematical modeling of the gear and the machined profile is strongly related to CNC machining technologies. A robust correlation of systems supporting the design and modeling of sliding gears needed for the manufacturing process is presented in the article. It is very important to properly assess gears with correct manufacturing in accordance with a specific standard. The article presents an analysis of available methods for controlling gears using coordinate measurement techniques. Gear machining methods were assessed in terms of the technologies used as well as their productivity and manufacturing tolerance. [ABSTRACT FROM AUTHOR]

The tooth profiles at different positions of the non-circular gear pitch curve have the characteristics of equal modulus but unequal curvature radius and polar diameter. The distribution characteristics of the envelope curve of each tooth profile formed during the hobbing process are different, which lead to the unequal envelope error of the tooth profile at different positions. Taking the basic linkage model of hobbing as the motion constraint, the geometric simulation scheme of the tooth profile generated by the intermittent cutting of the hob is constructed, and the correlation characteristics between the envelope distribution and the curvature radius of the pitch curve and the polar diameter are analyzed. The concept of equivalent hobs is introduced, the relationship model between envelope error and equivalent gear tooth number and equivalent hob groove number is built, and the calculation and position distribution of the maximum envelope error of different tooth profiles are analyzed. A hobbing model to improve the envelope error is proposed. The model can realize the change of the equivalent hob groove number at different positions of the non-circular curve through the hob shifting method, thereby the maximum value and uneven distribution of the envelope error are improved. This study provides theoretical support for the analysis of the tooth profile envelope error of the non-circular gear hobbing, which can predict the envelope error and guide the formulation of a reasonable machining plan.

Harmonic drives are critical components in robotic joints, and the hobbing accuracy of flexspline tooth profiles is essential for the transmission accuracy and operational stability of harmonic drives. The objective of this study is to propose an analysis method for the hobbing accuracy of flexspline tooth profiles. Firstly, a synthetic volumetric error model considering both geometric errors and thermal deformations was established based on the multi-body system theory. This model demonstrates the correlation between individual errors of the hobbing machine tool components and the spatial machining accuracy. Furthermore, the kinematic relationship of flexspline hobbing was established. Through kinematic analysis, it is concluded that the radial position deviation of the hob along the Y direction in the hobbing coordinate system directly affects the machining accuracy of the flexspline tooth profile. This deviation leads to variations in the tooth thickness of the flexspline tooth profile. Finally, theoretical tooth thickness deviations of the flexspline tooth profiles were predicted. Actual measurements of the flexspline tooth profiles were conducted, obtaining measured tooth thickness deviations. The measured values were smaller than the theoretical values, indicating the correctness of the established synthetic volumetric error model and the effectiveness of the proposed analysis method for evaluating the hobbing accuracy of flexspline tooth profiles. This research provides valuable technical references for error tracing and compensation in the gear hobbing process.

Gear materials need a more in-depth analysis to verify the conditions of chemical elements and their structural formations. Among them, the focus is often related to the thermochemical treatment process, which should ensure low levels of distortion in micro-geometry due to its high level of mechanical accuracy. In gear manufacturing processes where profile and helix errors are defined in operations prior to thermochemical treatment, process designers are faced with challenges to ensure tooth quality levels. Processes such as hobbing and shaving are important in gear manufacturing. This study addressed the influence of some factors on the gear manufacturing finishing process, as well as the steel alloy microstructure, on the geometric distortion levels in the profile and helix. All stages of the experiments were followed in a controlled manufacturing process, observing the behavior of micro-geometric parameters in each manufacturing phase in the hobbing, shaving, and carbonitriding processes. This analysis was performed on DIN 19MnCr5 alloy steel batches whose microstructures are different, after analyzing them in a laboratory to characterize each one. These observations can lead to important decisions being taken in the manufacturing process to improve a product, regarding the profile and helix parameters. Decisions can also be made about optimizing manufacturing processes. [ABSTRACT FROM AUTHOR]

Gear drives are widely used in various fields and applications due to their properties and capacity. Their versatility, durability, and ability to transmit high torques as well as precision and reliability make them extremely useful in many fields of technology. They are widely used in industrial and energy machinery, vehicle drive systems, aerospace, medical devices, and many other areas. Gears can be manufactured using many technologies. This work focuses mainly on machining with particular emphasis on high-performance new technologies. The process of mathematical modeling of the gear and the machined profile is strongly related to CNC machining technologies. A robust correlation of systems supporting the design and modeling of sliding gears needed for the manufacturing process is presented in the article. It is very important to properly assess gears with correct manufacturing in accordance with a specific standard. The article presents an analysis of available methods for controlling gears using coordinate measurement techniques. Gear machining methods were assessed in terms of the technologies used as well as their productivity and manufacturing tolerance.

This paper presents the influence of three lubrication environments, namely hobbing with minimum quantity lubrication (HWMQL), hobbing with flood lubrication (HWFL), and hobbing without any lubrication (HWAL), on the wear characteristics, microhardness, functional performance parameters, generation of noise and vibrations, flank surface roughness, and microgeometry deviation parameters of spur gears. Convective heat transfer coefficients in HWMQL and HWFL are evaluated to study the cooling mechanism involved and their heat dissipation capabilities during spur gear manufacturing. It is found that HWMQL-manufactured spur gears exhibited higher microhardness and smaller values of microgeometry deviations, flank surface roughness, functional performance parameters, wear rate, wear volume, and noise and vibrations than the spur gears manufactured by HWFL and HWAL. HWMQL facilitated a significantly higher convective heat transfer coefficient than HWFL, indicating its superior hobbing performance. An examination of the worn flank surfaces of HWMQL-manufactured gears revealed a wear track that resulted in less abrasive wear, wear debris, and subsurface damage, whereas the worn flank surfaces of HWFL-manufactured gears showed deep grooves, feed marks, and surface defects. This study proves that HWMQL is capable of manufacturing gears with better accuracy, enhanced wear resistance, smoother and quieter operational performance, and longer service life due to its better cooling and lubrication action. The results of this study will be very helpful for the manufacturers and users of spur gears. [ABSTRACT FROM AUTHOR]

Conventional semisupervised learning approaches are limited by the reliance on assumptions of samples (manifold assumption, cluster assumption, and smoothness assumption) and may fail to reach their full potential when it comes to industrial scenarios with complicated data characteristics. In this article, a semisupervised process quality evaluation framework is proposed based on conditional variational auto-encoder. Label inference process is utilized to handle unlabeled samples during training stage and to directly predict the label during the evaluation stage. Real-valued nonvolume preserving (Real NVP) is introduced to optimize the posterior distribution in order to increase flexibility. The proposed framework does not rely on assumptions of data distributions and it learns the hidden distributions from samples. Gear hobbing simulation and experiment investigations are conducted to verify the effectiveness of the proposed framework. The results indicate that the proposed method can achieve remarkable classification performance compared with other state-of-the-art approaches. [ABSTRACT FROM AUTHOR]

The paper describes a theoretical research approach that performs a dynamic study upon a complex gear transmission. The transmission errors of the gears from the considered complex gear drive are considered when kinematics is analyzed and presented. The cutting forces from a gear hobbing process, possibly driven by such a complex gear transmission, are considered when parameters of the dynamic model are mathematically evaluated and presented. The proposed model development includes the obtaining of the differential equation for kinetic energy. Some discussions are also made regarding the studied complex mechanism. Practically, mathematical models for the influence of transmission errors and hobbing forces upon the considered complex gear drive are proposed as deliverable results of the study. Final conclusions are also included in the paper. The aspects discussed in the paper are presenting utility for the design of such mechanisms or for calculating the parameters of some gear hobbing processes. [ABSTRACT FROM AUTHOR]

In the paper the influence of cutting speed on the hob wear in gear hobbing when minimum quantity lubrication (MQL) cutting fluid supply method was applied, is described. Gears made of C45 steel were cut with the use of the hobs made of HS6-5-2 high-speed steel. For comparison, some tests with flood cutting fluid supply mode were performed. The investigations were carried out for four cutting speeds with constant feed rate and the full depth of tooth spaces. The tool wear was measured in a direct way, as the width of the flank wear land (VBC parameter). The results of the investigations were presented in the form of the diagrams of the distribution of tool wear on consecutive hob teeth vs. time, and also as the diagrams of the tool wear changes for the most loaded hob's tooth. By the use of the Taylor's equation the influence of the cutting speed on the hob tool life T period was determined. Based on the results obtained it was found that the MQL method can be an alternative solution for the cutting fluid supply in hobbing.

This paper presents the influence of three lubrication environments, namely hobbing with minimum quantity lubrication (HWMQL), hobbing with flood lubrication (HWFL), and hobbing without any lubrication (HWAL), on the wear characteristics, microhardness, functional performance parameters, generation of noise and vibrations, flank surface roughness, and microgeometry deviation parameters of spur gears. Convective heat transfer coefficients in HWMQL and HWFL are evaluated to study the cooling mechanism involved and their heat dissipation capabilities during spur gear manufacturing. It is found that HWMQL-manufactured spur gears exhibited higher microhardness and smaller values of microgeometry deviations, flank surface roughness, functional performance parameters, wear rate, wear volume, and noise and vibrations than the spur gears manufactured by HWFL and HWAL. HWMQL facilitated a significantly higher convective heat transfer coefficient than HWFL, indicating its superior hobbing performance. An examination of the worn flank surfaces of HWMQL-manufactured gears revealed a wear track that resulted in less abrasive wear, wear debris, and subsurface damage, whereas the worn flank surfaces of HWFL-manufactured gears showed deep grooves, feed marks, and surface defects. This study proves that HWMQL is capable of manufacturing gears with better accuracy, enhanced wear resistance, smoother and quieter operational performance, and longer service life due to its better cooling and lubrication action. The results of this study will be very helpful for the manufacturers and users of spur gears.

Results of complex mathematical and computer simulation of gear hobbing are given. A systematic approach to research allowed for the development of simulation models and sequencing of all aspects of this complex process. Based on the modeling of non-deformable chips, a new analytical method for analyzing hobbing has been proposed. The shear, friction and cutting forces at the level of certain teeth and edges in the active space of the cutter are analyzed depending on the cut thickness, cross-sectional area, intensity of plastic deformation and length of contact with the workpiece has been developed. The results of computer simulations made it possible to evaluate the load distribution along the cutting edge and to predict the wear resistance and durability of the hob cutter, as well as to develop measures and recommendations for both the tool design and the technology of hobbing in general. Changing the shape of cutting surface, or the design of the tooth, can facilitate separation of the cutting process between the head and leading and trailing edges. In this way, more efficient hobbing conditions can be achieved and the life of the hob can be extended. [ABSTRACT FROM AUTHOR]

This paper focuses on parametric analysis, modelling, and parametric optimization of minimum quantity lubrication–assisted hobbing (MQLAH) using an environment-friendly lubricant for manufacturing superior quality spur gears. Influences of hob cutter speed, axial feed, lubricant flow rate, air pressure, and nozzle angle on the deviations in total profile, total lead, total pitch and radial runout, and flank surface roughness parameters were studied by conducting 46 experiments using the Box-Behnken method of response surface methodology. Results revealed that the effect of air pressure is negligible but other parameters have a significant impact on the considered responses. A back propagation neural network (BPNN) model was developed to predict microgeometry deviations and flank surface roughness values of the MQLAH-manufactured spur gears. The BPNN-predicted results are found to be very closely agreeing with the corresponding experimental results with a mean square error as 0.0063. A real-coded genetic algorithm (RCGA) was used for parametric optimization of MQLAH process for simultaneous minimization of microgeometry deviations and flank surface roughness. Standardized values of the optimized parameters were used to conduct confirmation experiments whose results had very good closeness with RCGA-computed and BPNN-predicted values and produced spur gears of superior quality. This study proves MQLAH to be a potential sustainable replacement of conventional flood lubrication–assisted hobbing for manufacturing cylindrical gears of better quality. [ABSTRACT FROM AUTHOR]

In recent hobbing, the technologies of dry cutting have been developed in an attempt to improve the working environmental and prevent global environmental pollution. In this study, we investigated wear behavior (tool life), crater wear and finished surface roughness of various coated cutting tools when hardness of work material was changed by heat treatment in dry hobbing. Experiments were conducted by simulating hobbing by fly tool cutting on a milling machine. The results helped clarify the following points: (1) When the hardness of workpiece material SCM415 was changed to HB131, HB144 and HB161, the tool life obtained with all of the four kinds of coated cutting tools used in this experiment in the cases of cutting HB131 (annealing) and HB161 (as rolled) work materials is longer than the case of cutting HB144 (normalizing) work material. Especially AlCrSiN-coated tool is effective. (2) For various coated tools, the crater wear tends to decrease in the order of cutting HB144, HB131 and HB161 work materials, and when cutting HB161 work material with AlCrSiN-coated tool, the crater wear is small. (3) Even if the hardness of the workpiece is changed, the finished surface roughness is as small as 1 μm when cutting with the AlCrSiN-coated tool compared to other coated tools. (4) From the viewpoints of tool life, crater wearand finished surface roughness comprehensively, AlCrSiN-coated tool is effective when the hardness of the work material is changed.

Simulation studies of the hobbing process kinematics can effectively improve the accuracy of the machined gears. The parameters of the cut-off layers constitute the basis for predicting the cutting forces and the workpiece stress-strain state. Usually applied methods for simulation of the hobbing process are based on simplified cutting schemes. Therefore, there are significant differences between the simulated parameters and the real ones. A new method of hobbing process modeling is described in the article. The proposed method is more appropriate, since the algorithm for the momentary transition surfaces formation and computer simulation of the 3D chip cutting sections are based on the results of hobbing cutting processes kinematics and on rheological analysis of the hob cutting process formation. The hobbing process is nonstationary due to the changes in the intensity of plastic strain of the material. The total cutting force is represented as a function of two time-variable parameters, such as the chip's 3D parameters and the chip thickness ratio depending on the parameters of the machined layer. [ABSTRACT FROM AUTHOR]

This paper reports on study of laser texturing assisted abrasive flow finishing (LT-AFF) process of the hobbed spur gear (HSG) to further improve their microgeometry, surface finish, micohardness, microstructure, wear resistance, and material removal rate (MRR) as compared to AFF process. Preliminary experiments were conducted to identify optimum values of power and focal length of the continuous fiber laser of 1064-nm wavelength, and number of passes for laser texturing of the HSG made of 20MnCr5 alloy steel. Identified optimum values were used to produce homothetic texture on flank surfaces of HSG in a direction perpendicular to the lay profile generated by hobbing. Influence of laser texturing was studied by comparing deviations in microgeometry, average and maximum surface roughness values, microhardness, wear resistance, and MRR of HSG directly finished by AFF and laser-textured hobbed spur gears (LTHSG) finished by AFF. Previously optimized value of viscosity of AFF medium was used during finishing of HSG and LTHSG. Deviations in total profile, total lead and total pitch, and radial runout were used to indicate deviation in microgeometry of the spur gears. Results reveal that AFF of LTHSG reduced surface roughness and errors in microgeometry and improved microhardness, microstructure, wear resistance, and MRR than direct of AFF of HSG. Improved microgeometry and surface quality of spur gears will lead to their increased operating performance and service life thus reducing their running noise and vibrations and preventing their premature and failures. This research proves that productivity of AFF process can be improved significantly by laser texturing for finishing the spur gears. [ABSTRACT FROM AUTHOR]

Abstract Knowledge about the angular tool position is important for many modern process monitoring or control systems in machining. However, the availability of a high-resolution encoder is not always given, and its access creates further expenditure. Hence, a new method was developed to generate the tool position out of the measurement signal of the effective power. Thus, the signal used for process monitoring also provides further information about the tool position. The method is based on a statistical analysis of the signal in order to find recurring patterns and is validated in a hobbing process. [ABSTRACT FROM AUTHOR]

This paper describes manufacturing capabilities evaluation of wire spark erosion machining (WSEM), milling and hobbing to manufacture meso straight bevel gear (MSBG) and meso helical gear (MHG) made of SS 304 using microgeometry, macrogeometry, flank surface topology, surface finish, microstructure, microhardness, manufacturing time and cost, and gear material loss. Experiments were conducted using the parameters of WSEM, milling and hobbing processes optimized through trial experiments. This study reveals that WSEM manufactured MSBG and MHG possess better microgeometry (DIN 5-7), macrogeometry (29, 33, and 46 µm deviation in span, tooth thickness and outside diameter for MHG), topology, higher microhardness, superior microstructure, lower manufacturing time (25 and 20 min, respectively) and cost ($ 4 for both), smaller loss of gear material but poor surface finish (1.07 and 6.60 µm as average and maximum surface roughness for MHG and 1.04 and 6.16 µm for MSBG) than milled MSBG and hobbed MHG. Microstructure study showed presence of burrs and marks of the cutting tool on the flanks of the best quality hobbed MHG and milled MSBG. It proves that WSEM is a superior, economical, material efficient, and environment friendly process to manufacture meso-sized cylindrical and conical gears of higher accuracy and better quality with excellent repeatability. [ABSTRACT FROM AUTHOR]

Machining performance, such as carbon emission, machining time, and quality, can be improved by selecting appropriate tools and cutting parameters for gear hobbing. However, the importance machining performance is usually difficult for users to quantify. To resolve the decision-making problem of hobbing tools and cutting parameters in fuzzy evaluation, a multi-objective fuzzy decision-making approach for hobbing parameters is proposed. It uses spectral clustering, the multi-objective weighted mean of vectors (MOINFO) algorithm and the fuzzy technique for ordering preference by similarity to the ideal solution (TOPSIS) algorithm. First, spectral clustering is used to confirm the initial range of the hobbing parameters based on past machining cases. MOINFO is then applied to search for nondominated hobbing parameters based on the optimization model, taking the carbon emission, cutting time, and quality as the objectives. Finally, the nondominated hobbing parameters are sorted by fuzzy TOPSIS according to a user evaluation, and the hobbing parameter ranking is used to guide hob selection and machining. Decision-making experiments on the hobbing parameters are performed with actual hobbing. The comprehensive evaluation index C E I result for the proposed approach is 0.19. Compared with other methods, the proposed approach exhibits certain advantages. These results demonstrate that the multi-objective decision-making problem of hobbing parameters under fuzzy evaluation can be solved using the proposed approach. [Display omitted] • INFO is fused with Pareto improvement to form MOINFO for obtaining the noninferior hobbing parameters. • The fuzzy TOPSIS is used to address the fuzzy user requirements for the most suitable hobbing parameters. • The spectral clustering method is to obtain the preliminary value range of the hobbing parameters. [ABSTRACT FROM AUTHOR]

In the paper evaluation of the influence of axial feed on the hob wear in hobbing with minimal quantity lubrication technique has been done. As a work material C45 carbon steel has been investigated. Wear resistance of the hob made from high speed steel HS6-5-2 without coating has been investigated. For comparison tests with conventional fluid supply method have been carried out. Gears have been generated with full depth of cut and with two axial feed with constant cutting speed value. During hobbing cutting forces have been measured by experimental stand. Tool wear has been measured directly as a width of flank wear land of the hob cutter teeth. During investigation any significant wear changes on the rake faces haven’t been detected, so those results haven’t been taken into consideration. A constant length of cut parameter has been established as a criteria value. Results of investigation have been presented in the form of graphs describing changes of wear land width parameter in comparison to the most loaded tooth wear land parameter. Also changes of cutting forces in time are presented too. On the base of obtained results conclusion has been formulated that MQL technique might be used as an alternative solution for supplying cutting fluid into the cutting zone during hobbing process.

In order to improve the efficiency of gearprocessing,a kind of CNC hobbing automatic programming system is presented. Firstly,the mathematical model of the hober- axial roll cut method is established.Then,the hober hardware platform of CNC gear hobbing automatic programming system is established,the several functional modules and the software page set are designed. Finally,the object- oriented software programming technology,communications technology,multi- threading technology and decoding technology in the system development are analyzed. The automatic programming technology provides some convenient reference and experience for the future gear hobbing CNC machining.

The hobbing of external gears by a worm mill without machining fluid is considered, theoretically and experimentally. The performance of worm cutters made of high-speed powder steel is investigated. [ABSTRACT FROM AUTHOR]

The availability, adaptability, reliability and productivity of modern industrial complexes, maintenance costs, energy costs and industrial production costs depend also on the intensity of wear of the elements of tribo-mechanical systems. Gear cutting operations are usually a bottleneck of production, especially in higher types of production. Therefore, the necessity of researching the process of gear cutting by hob milling is obvious. In the paper a part of the results related to the possibility of direct measurement of the temperature in a very complex process of gear cutting of cylindrical gears by hob milling is given. [ABSTRACT FROM AUTHOR]

Dry hobbing is a well-known environmentally benign process for gears production by eliminating serious pollution and occupational health hazards in the shop floor. However, due to the absence of the cooling and lubrication of cutting oil, it requires quite accurate monitoring and adjustment of the accumulation of thermal energy within the cutting space to reduce the thermal deformation of machine tool. In this paper, an analytical method is proposed to reveal the mechanism of thermal energy accumulation in dry hobbing. And further, a thermal energy balance optimization model is developed to minimize the average temperature of cutting space by optimizing the heat-carrying efficiency of chips, the temperature of compressed air, and the mass flow rate of air filter. The comprehensive learning particle swarm optimization (CLPSO) based solution method is designed to search the optimal solutions of the proposed model. To verify the performance of the proposed thermal energy balance problem, a case study has been conducted and the experimental results showed that the maximum difference of the average temperature of cutting space reduced by 16.3%, and the M-value of hobbed gears was effectively controlled, which demonstrated the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Manufacturing of gears can be achieved with various methods, including the cutting of gears in a hobbing machine. The function of such a machine tool is based on a combination of timing gears which synchronize all moving components accurately. Variations in the synchronization, which alter the geometric features of the gear being cut, are achieved via external gearboxes with interchangeable gears. Thus, precise knowledge of the change gears that correspond to the desired gear geometry is essential in order to operate the machine tool properly. The hobbing machine examined in this paper had remained unused for years, without a manual to indicate the correct use of the external gearboxes. The task was to render the machine tool functional by devising an experimental procedure for the calculation of the internal gear ratios and the correct combination of change gears, making use only of simple tools. The project was carried out successfully and proved to be an excellent case study to delve into the manufacturing as well as the use of gears. The documentation of the whole procedure and a short explanatory video are integrated within the educational aids of a relative course in the School of Mechanical Engineering of the National Technical University of Athens. [ABSTRACT FROM AUTHOR]

Cutting tools are extensively used in subtractive manufacturing systems for achieving the desired products. The advancement of cutting tool technology promotes the development of efficient and green machining. However, as one of the auxiliary consumptive materials, cutting tools have a crucial impact on the sustainability of machining systems. Thus, the development of sustainability urgently requires characterizing the impacts of cutting tools. This paper investigates the environmental impacts of cutting tools from the life cycle aspect based on the material and energy consumption during the material extraction, manufacturing, use, and recycling of cutting tools. Carbon emission is applied to measure the impacts of cutting tools on the sustainability of the machining system. Then a life cycle carbon efficiency approach based on the service life of the cutting tool is presented to characterize the life cycle carbon emission characteristics of cutting tools. A gear hobbing system with five kinds of hobs was introduced as a case study to characterize the life cycle carbon emissions and efficiency of hobs. It indicates that substrate and coating material type, manufacturing process, coating method, and regrinding times all influence the carbon emissions and efficiency of hobs to different extents. A high-speed dry-cutting hob exhibits excellent carbon efficiency in addition to carbon emissions. [ABSTRACT FROM AUTHOR]

High-speed dry hobbing is an emerging green technique for gear hobbing owing to its high productivity and environmental friendliness. However, severe friction occurs and heat instantaneously accumulates in the cutting region due to the adoption of high cutting speed and the lack of metalworking fluids, which causes serious hob wear. This investigation is concerned with the thermal performance and heat-loading quantitative method of hob cutter in high-speed dry hobbing. According to the multiple-edge and intermittent cutting behavior, the temporal dynamic characteristics of hob cutter are analyzed. Based on the complex 3D chip geometry produced in high-speed dry hobbing, the calculation method for heat-production (the amount of generated cutting heat) of hob tooth is proposed. Considering the coupling effects of heat conduction, heat convection, and heat radiation, the prediction model for heat-loading quantity (the bearing capacity of cutting heat) of hob tooth is developed. With the help of the developed method, the interrelation between the thermal performance of hob cutter and material removal volume, cutting conditions, coating material, respectively, are investigated. The predictive method developed in this work provides a methodology for process parameter optimization and hob cutter manufacturing of high-speed dry hobbing. [ABSTRACT FROM AUTHOR]

A single enveloping worm gear of cylindrical worm gear drive is cut by an oversized hob. The oversize provides a longitudinal crowning on the worm gear tooth surface. However, when a lead angle of the worm becomes higher, the longitudinal crowning becomes more asymmetric. The asymmetrically crowned worm gear surface makes the gear contact more sensitive to the certain direction of misalignment. To change the longitudinal crowning from asymmetric to symmetric, a method of modified worm gear hobbing is proposed. The modification uses a modified machine tool setting and a modified hob specification. A new hobbing mechanism or hob geometry is not required in this method. Results of the proposed modification are confirmed by using a surface separation topology based on differential geometry, and contact pressure analysis based on finite element method. [ABSTRACT FROM AUTHOR]

This paper aims to present the results of a study that has resulted in a matrix-vector mathematical model of the process of machining milling cutter of the double worm-face wheels, which engages with a cylindrical worm, with hob through tangentially advanced.. The mathematical model developed provides determine the coordinates of the points that make up the flanks of the two crowns worm-face gear machined simultaneously. Worm generator was considered a cylindrical worm with flanks asymmetric Archimedean. Coordinates obtained by calculation allow modelling in a graphical environment of the machined wheels