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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 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 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]

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]

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]

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]

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]

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]

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]

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]

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]

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]