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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]

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]

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]

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]

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]

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]

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]

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]

Dry hobbing is a new gear machining process with high efficiency and environmental friendliness, replacing traditional wet hobbing process. However, to get high reliable precision, it is a critical work for the dry hobbing system to reduce and control the thermal impact. Even new hobbing machine tool structure with high thermal stability such as double stand columns was designed to substitute the traditional structure; some new structures, such as air extraction and filtration device, air-cooling component, and magnetic chip conveyor, would affect the thermal energy accumulation of dry hobbing machine tool. In this paper, a multi-variable thermal energy control model was developed to describe the thermal energy accumulation characteristic of dry hobbing machine tool. Variables which would affect thermal energy generation and sink of dry hobbing machine tool are analyzed. A multi-objective optimization algorithm is proposed for variable optimization, combined with the multi-variable thermal energy control model. An application method is presented to show the thermal energy control procedure of dry hobbing machine tool. As a result, the temperature variation of interior space air, workpiece column, and anterior end cover is fluctuated in an acceptable range with optimization. Furthermore, thermal deformation errors, which range from −7 to 3 μm, could meet production requirements. It illustrates that the multi-variable driving thermal energy control model of dry hobbing machine tool is available. [ABSTRACT FROM AUTHOR]

Copyright of Metal Forming / Obróbka Plastyczna Metali is the property of Instytut Obrobki Plastycznej 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.)

Copyright of Scientific Bulletin of National Mining University is the property of National Mining University, State Higher Educational Institution 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.)

Gear hobbing technology is one of the most widely used forming processes of gear teeth. And the development of dry hobbing technology provides a solution for realizing productive, economical, and ecological gear production. Since there is no cutting oil for cooling and lubrication in dry hobbing process, the hob tool life, thermal deformation errors of machine tool, and quality of workpiece are sensitive to the cutting parameters, especially the cutting speed and tip chip thickness. Considering this situation, a dry hobbing parameters optimization model with the hobbing efficiency as our objective, and the hobbing cost per piece, gear quality, tact time as constraints was established, in which the cutting speed and tip chip thickness were considered as optimal variables and the material of workpiece, coating of hob, and feed rate were considered comprehensively. An iterative test method is proposed to solve this model. And for the application in automated production line, an online adaptive application system was also developed based on SINUMERIK 840D NC system. The parameters of five different kinds of material gear were optimized by applying this model and system, and the result showed the model and the system were practical. [ABSTRACT FROM AUTHOR]

High-speed gear hobbing, especially dry hobbing, is an economical and environmentally friendly way to machine massive workpieces. Considering the fact that high-speed gear hobber are more expensive than the conventional machine tool and the same is true of the corresponding cutters, it is requisite that process parameters are decided appropriately so as to obtain the ideal comprehensive machining effect. What is more, the classical decision-making method of process parameters scarcely consider parameters' adjustment in the hobbing process of a batch of gears. To resolve the problems, this work presents a hybrid improved back propagation neural network/differential evolution (IBPNN/DE) approach to do a continuous optimization decision making of process parameters in high-speed gear hobbing. Gear hobbing effect evaluation model is first structured to assess the machining effect. The optimization population of the process parameters, which is the input of the DE module, is generated by the IBPNN module. Using the DE algorithm, the best of best process parameters are obtained during the course of working. Finally, a test case is presented to give a clear picture of the application of the optimization approach. The results reveal that the proposed IBPNN/DE method has better performance than the general decision-making method under the comprehensive evaluation criterion over a batch of workpieces. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mechanical Engineering / Strojniški Vestnik is the property of University of Ljubljana, Faculty of Mechanical Engineering, Journal of Mechanical Engineering 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.)

The gear generation process is strongly dependent on the accuracy of the multi-axis relative motion, which is controlled by the electronic gearbox (EGB). This research mainly focuses on helical gear hobbing and on EGB control error analysis, estimation and compensation in the generation process of a gear hobbing machine. First, a simple approach for estimation of the helical gear pitch error and the spiral line contour error is proposed. Then, in conjunction with this estimation method, an EGB cross-coupling controller (ECCC) architecture, which is connected by the EGB and the cross-coupling controller, is presented. Simulation results show that the proposed ECCC has higher control accuracy than an uncoupled controller, and its control accuracy can be further improved using friction compensation. Finally, experiments are conducted on an YS3118 six-axis hobbing machine. The helical gears machined using this machine have high precision. In addition, the proposed ECCC architecture can be implemented easily on most motion systems that are in current use. [ABSTRACT FROM AUTHOR]

As an efficient manufacturing method for gears, shaping technology developed for non-circular helical gears will greatly break through the dilemma of their applications; especially for those gears with part of pitch curves being concave, being not able to be hobbed. Two fundamental linkage-models for external non-circular helical gears were built based on the meshing theory of non-circular gears in this article. According to four linkage methods in plane and two kinds of additional rotation in vertical direction, eight shaping strategies and their practical linkage-models (1)–(8) were developed. Taking a three-order elliptic helical gear as an example, the kinematic characteristics of the eight practical linkage-models were analyzed, which reveals that equal arc-length of gear billet (models (3) and (4)) have the highest accuracy under a given efficiency. The dynamic characteristics of models (3) and (4) were analyzed, which shows that model (4) (equal arc-length of gear billet and additional rotation on shaper cutter) is better in performance, and is an optimal one. The optimal linkage-model was demonstrated to be valid by a virtual shaping, and be able to shape those non-circular helical gears with part of pitch curves being concave. Moreover, the accuracy among every gear tooth is uniform. The theory developed and the results of the virtual shaping were illustrated with a shaping experiment. The train of thought and the results will be useful for any external non-circular helical gears with free pitch curves. [ABSTRACT FROM PUBLISHER]

As dominating manufacturing process to create external gears, hobbing is of major industrial importance. Hence, a continuous process optimisation to satisfy the demand of the market is necessary. Changing the substrate material is a basic approach in optimization of operation times. Due to acquisition costs and lacking knowledge most companies hesitate to use cemented carbide hobs which endure higher cutting speeds compared to HSS/PM-HSS. Offering experience based knowledge which can be used to revise the cemented carbide application in industry, cutting parameters were varied investigating their influence on the wear behaviour. The impact of high performance cutting parameters within a fly cutting analogy test was examined using different measurement techniques and simulation results. [ABSTRACT FROM AUTHOR]

With increasing emphasis on miniaturization, the demand for manufacturing the high-quality fine-pitched miniature gears is growing continuously. Inability of the conventional processes to manufacture high-quality miniature gears compels the need to explore a process which can economically manufacture precise and accurate gears required by the various miniature products used for different scientific, industrial, and domestic applications. This article reports on exploring and subsequently establishing wire electric discharge machining (WEDM) process as a superior, economical, and viable alternative for manufacturing the high-quality miniature gears through a comparative evaluation of process capabilities of WEDM and gear hobbing which is the most commonly used conventional process. The evaluation concentrated on those capabilities of these two processes which affect functional performance and service life of the miniature gears. This included microgeometry parameters (i.e., profile error and pitch error) and surface integrity aspects (i.e., surface topography, surface roughness, microhardness, and microstructure). The miniature gears manufactured by WEDM were found to be of superior quality (of DIN standard 5) and surface integrity than the hobbed gears (of DIN standard 10). [ABSTRACT FROM AUTHOR]

In a well-chosen hobbing configuration, the hazardous tensile stresses in hard-alloy inserts are significantly less than in the standard configuration. [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 [ABSTRACT FROM AUTHOR]

Hobbing process is one of the machining methods in manufacturing spur gears. In machining processes, selecting a suitable lubricant is one of the significant factors in enhancing machining productivity and improving the characteristics of manufactured workpieces. This study has used the nanolubricant including alumina nanoparticles dispersed in mineral-based oil 25W-50 in hobbing process. Then, hobbing process using the lubricant including both nanoparticles, and none has been done utilizing with the similar hob tools. Two spur gears with DIN1.7131 material have been manufactured using each of two lubricants. Then, the hob tool wear and surface roughness values of manufactured spur gears were investigated. Comparing the results show that using lubricant including alumina nanoparticles in hobbing process causes an expressive decrease in the hob tool crater and flank wear. Also, arithmetic surface roughness value in spur gears manufactured with nanolubricant has decreased. [ABSTRACT FROM AUTHOR]

Gear couplings are mechanical components to connect shaft ends and eliminate the misalignments. The most important element of the gear coupling is the hub which is an external gear having crowned teeth. The crowned teeth on the hub are typically produced by hobbing. The resulting tooth surface depends on several parameters. It is influenced by the size of the hob and the feed. In this paper two mathematical models of the crowned tooth surface are introduced for the generation of the idealized tooth surfaces. These are the profile-shifting and the two-parameter enveloping methods. Our aim is to compare the obtained crowned tooth profiles for the two examined models and to investigate the results. From our numerical results, it was found that the two profiles show indistinguishable differences. [ABSTRACT FROM AUTHOR]

This paper approaches the issue of profiling gear hob bounded by a cylindrical helical surface with constant pitch, reciprocally enveloping with an ordered surfaces curl. The process kinematics of generation reproduces the 3D gear between the worm and the wheel. This gear has crossing axes and it is used for the profiling of the primary peripheral surface of the gear hub in the intermediary surface method (the common rack-gear of the surfaces curl to be generated and the primary peripheral surface of the gear hob). An algorithm in the CATIA design environment is presented, based onto an original method for the determination of the reference rack-gear form—the rack-gear reciprocally enveloping with the surfaces curl, using the principle of the cylindrical helical motion decomposition in translation and rotation motions. Graphical and analytical profiling examples are presented for the gear hob for generation of a parallel spline shaft and for the generation of a toothed wheel with involute teeth. Solutions for the interference problems, problems due to the singular points onto the profiles, are presented. [ABSTRACT FROM AUTHOR]

Spur involute gears may be manufactured using one of the the shape methods or by hobbing. Manufacturing process needs special tools and machine tools. Authors present basis of manufacturing technology based on step-by-step method for application on universal CNC machine tools. The tool in proposed method is ball end mill, whose geometry isn't associated with the shape of machined surface. The developed technology allows longitudinal and outline modification of gear teeth profile. Presented method may be useful especially in manufacturing non standard, large module gears in unity production. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mechanical Engineering / Strojniški Vestnik is the property of University of Ljubljana, Faculty of Mechanical Engineering, Journal of Mechanical Engineering 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.)

Optimal tool making is of great importance for reducing costs and increasing the performance of toolsets. The dies and punches, which are basic components of any metal forming toolset, are usually produced by machining, but this technology requires relatively long manufacturing times, characterized by significant material and energy waste. By replacing machining operations or combining them with forming ones, such as cold hobbing (indenting), significant cost and time savings, as well as improvement of tool performance could be achieved. Cold hobbing could be applied to making die cavities as well as shaping punch profiles. Investigations showed that a large number of variables influence the successful application of this technique. However, there is a scarcity of literature regarding the choice of relevant process parameters for the hobbing process. With this in mind, the aim of this paper is to yield further insight into the hobbing process. Special focus will be placed on the influence of the hob geometry on the deformation process and relevant process parameters. This paper presents theoretical, numerical, and experimental investigations of a cold hobbing process in which a cone-like punch is obtained. The upper-bound method was used for metal flow analysis and optimization of hob geometry. Stress-strain distribution, workpiece geometry prediction, and load estimation were obtained with the finite element method (FEM) using Simufact.Forming 8.1 software. The results were analyzed, compared, and discussed. [ABSTRACT FROM AUTHOR]

The paper presents an analysis of three-dimensional surface topography of side and side out in tooth space flanks of cylindrical gear machined after hobbing and chiselling by Fellows method. The parameters and functions of surface topography as well as spectral analysis were used. Primary surface topography after extraction of involute tooth profile was analysed. It was found that contour maps of areal power spectral density and autocorrelation functions were very useful for the analysis of teeth flank surface topography. The angular plot of areal power spectral density function assures proper description of surface, background and defects directionalities. Surface texture parameter SPtr and isotropy index Spiso are useful for quantitative surface topography analysis. Good distribution functions of amplitudes and summit curvatures isolate surface roughness height and shape. It was proved using a kinematical–geometric digital model of machining simulation in 3D system, universal generalised model and experimental investigations that the roughness height and roughness spacing were smaller for the tooth point surface than for the root surface after hobbing and Fellows chiselling. Roughness height of tooth profile after machining by one-coil cutter with great axial feed and by modular gear-sharper cutter is smaller than roughness height of tooth line. Inverse dependencies take place after hobbing by three-coil cutter with small axial feed. It was also found that flank teeth surface topography, primary profile along teeth height and teeth line along its width were quasi-periodic. In all the analysed cases, teeth flank surfaces going to the machining have higher roughness height than surfaces going out from the machining. It was probably caused by direction of chips runout; chips damage surface going into the machining. The flank tooth surfaces of a gear made by hobbing and Fellows-chiselling method are anisotropic and strongly oriented along the helix. The orientation of the flank surfaces after hobbing is considerably lower than after Fellows chiselling. [ABSTRACT FROM AUTHOR]

The paper presents the computer simulation methodology of modelling tooth flanks of cylindrical gears. The modelling consists of a computer simulation of a gear generation. A model of tooth flanks is an envelope curve of a family of envelopes that originate from the rolling motion of a solid tool model in relation to a solid model of the cylindrical gear. The surface stereometry and topography of the tooth flanks, hobbed, are compared to their numerical models. A computer simulation of the gear generation was performed in a mechanical desktop environment. [ABSTRACT FROM AUTHOR]