Gear Hobbing Research Articles

Investigation of the effects of alumina nanoparticles on spur gear surface roughness and hob tool wear in hobbing process

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.

Fast Production of Gear Prototypes – A Comparison of Technologies

The time-to-market for automotive and other gear-involved products is still reducing. This demands new production technologies for the manufacturing of functional gear prototypes. At the moment gear prototypes are made using classical series production technologies, such as gear hobbing and grinding. However, these technologies require design specific dedicated tools, making the production of a functional gear prototype expensive and time-consuming. This paper presents an experimental investigation and comparison of different alternative production technologies for the manufacturing of functional gear prototypes. Wire-EDM, Selective Laser Melting and milling using standard milling tools, have been compared for the production of a spur gear out of 16MnCr5 steel. A strategy for the wire-cutting of a spur gear was developed, resulting in a total machining time of 22h – with very good gear quality in terms of geometrical accuracy and surface roughness. This same gear has been produced by SLM, with a total machining time of 17h. Two different milling strategies have been developed on a milling machine, resulting in a total machining time of 14h15min. The shape accuracy and surface roughness were compared using a CMM and a surface profiler. Taking these results into account and considering the fact that it is impossible to make helical gears or machine micro flank corrections using wire-EDM, it was concluded that the milling is the most promising production technology for functional gear prototypes. The fact that functional prototypes could be made without the current lead time (± 10 weeks) is a great improvement for the production of gear prototypes, meeting the shorter time-to-market requirements of today's industry.

High speed temperature measurement in gear hobbing: Part I—design, concept and physical operation mode of the infrared-camera

Gear hobbing is the major technology to manufacture external gears. The motions of the tool and workpiece are dynamically linked. Therefore it is difficult to apply external measurement devices in the process. Especially the temperature, which is a vital factor to determine the load on the cutting edge, cannot be measured as easy as in other processes (for example turning). Suitable infrared-cameras are not commercially available, because these do not meet the demands for temporal and geometrical resolutions. Furthermore, commercial equipment has to be calibrated for each individual temperature (above 350 °C). This forced the Institute of Manufacturing Technology and Quality Management to develop an own measuring device. This camera is able to measure the temperature of the cutting surface within the gear hobbing process. Despite focusing the usage of the camera on hobbing in this paper, it can also be used to monitor further highly dynamical machining processes with discontinuous cutting conditions. This paper is divided into two parts. The first part describes the set-up, the concept and the physical and optical basics of the IR-camera. In the second part, the experimental realisation and the results of trials during an analogy test of the hobbing process are presented.

Study on Design Method of the Double Arc Gear Hobs

This article find that one of the effecting the double circular arc gear s running performance is the double circular arc gear tooth profile precision, through analysis to the running-in properties of double arc gear. The problems about tooth profile precision of gear hobs caused by the current profiling theory and approximate design method of gear hobs are analyzed. In the design of circular arc gear hob, use the space engagement theory, can eliminating the tooth error. Acquiring the equation of hobs basic of worm tooth surface by analytical and calculation that the establishment of basic gear rack and worm of hob meshing. The hob not only eliminate the tooth profile error in manufacturing, but also improve the running performance of double circular arc gear, and provides the theory evidence for engineering practice.

Tooth contact analysis for helical gear pairs generated by a modified hob with variable tooth thickness

Conventionally, the longitudinal crowning of helical gears can be accomplished by varying the center distance between the hob and work gear in gear hobbing process. Without a crossed angle compensation, however, this center distance variation produces twisted tooth flanks on the work gear. A methodology is thus proposed herein to reduce the tooth flank twisting of a longitudinal crowning gear by applying a modified variable tooth thickness hob and having a diagonal feed without varying the center distance. This study also investigates the gear tooth surface topologies, contact ellipses and transmission errors of the work gear pairs, generated by a conventional hob and the proposed modified hob with variable tooth thickness, respectively. Three numeral examples are presented to illustrate and verify the merits of the proposed gear hobbing method with longitudinal crowning.

Structure Optimization Design for the Bed of Gear Hobbing Machine

In the optimization design of the gear hobbing machine bed, the finite element model is build and the static analysis and vibration modal analysis are performed. Then sensitivity analysis is used to gain the main design parameters which influence the bed property most. Furthermore, the multi-objective optimization design of the bed is performed in ANSYS Workbench with these design parameters as the design variables. At last, after all optimum proposals are showed up, Analytic Hierarchy Process is used to determine the weighting coefficient, and the most optimal solution is found out. As a result, the dynamic and static performances of the machine bed are improved under control of the machine bed mass.

Research on Thermal Error Compensation of Gear Hobbing Machine

The purpose of this research is to improve the machining accuracy of YK3610 Hobbing machine through thermal error compensation. This study presents the whole process of thermal error modeling and compensation by using Back Propagation Network (BPN) and ant colony optimization is introduced into the training of BPN. The results show that the BPN model based on ant colony algorithm improves the prediction accuracy of thermal errors on the gear hobbing machine and the thermal drift has been reduced from 14.2 μm to 4.5 μm after compensation.

Research on thermal deformation of large-scale computer numerical control gear hobbing machines

Research on thermal deformation of large-scale computer numerical control (CNC) hobbing machines is on the purpose of obtaining the law of thermal deformation of gear hobbing machines to improve machining precision. According to the structure characteristics of hobbing machines, this paper presents a novel computing model of thermal deformation based on the theory of the thermal expansion deformation of metallic materials, the extensional beam theory, non-uniform temperature distribution of the Euler-Bernoulli beam and Kirchhoff theory of plane-section assumption. Then, the coupling theory of axial and bending deformation of hobbing machines based on the deformation element and equilibrium element method is proposed. The experimental measurement system and platform for thermal deformation of gear hobbing machines is established. The temperature and displacement data of thermal deformation of a certain type gear hobbing machine is analyzed, which has demonstrated the law of thermal deformation of hobbing machines. The locus curves for overall displacement error of cutting points and teeth trace error are obtained. Comparing deformation theory and experimental data, the relative error is lower than 5%, which verifies the computing model proposed by this paper, and shows the research method has great significance for structural optimization, local temperature control, and prediction and compensation for thermal deformation error of gear hobbing machines.

A Precision CNC Turn-Mill Machining Center with Gear Hobbing Capability

With ever increased demand for reduced sizes and increased complexity and accuracy, traditional machine tools have become ineffective for machining miniature components. Typical examples include dental implants, the parts used in mechanical watch movement, and the parts used in medical endoscope. With complex geometry and tight tolerance, few machine tools are capable of making them. This paper introduces our PC-based CNC Turn-Mill Machining Center. It has 5 axes, an automatic bar feeder, an automatic part collection tray, and a tool changer. In particularly, it has a special synchronization control algorithm that gives not only higher accuracy but also ease of use. In addition, to improve the accuracy, the software based volumetric error compensation system is implemented. Based on the experiment testing, the machining error is ± 3 µm in turning, ± 7 µm in milling and the maximum profile error is less than ± 7.5 µm in gear hobbing.

Influence of machining data on developed cutting forces in gear hobbing

In every manufacturing process the prior knowledge of the developed cutting forces is crucial in order to increase the cutting performance and make the optimal selection of cutting conditions. In gear hobbing the complexity of the process as well as the diversity of the produced chips makes it difficult to create and use empirical charts that predict cutting forces according to the process parameters. The CAD-based simulation model Hob3D was developed in an effort to create an accurate model for gear hobbing that can produce reliable results for the cutting forces. The effect of the various parameters of the gear hobbing on the developed cutting forces with the aid of Hob3D is presented in this paper.

Research on Mapping Rules of Hob Geometric Errors and Gear Geometric Precision

High precision gear is an necessary support of high-end equipment to meet the requirements of high-speed, heavy-duty,impact, low noise(mute) and other extreme environments. In order to improve the accuracy of hobbing manufacture, to partly achieve"replacing grinding with rolling", and to reduce processing costs, focusing on the insufficient quantitative mapping rules between hob geometry errors and gear geometric error, the quantitative mapping rule research between gear hob tooth profile error, helix error, gear hob installation angle of the radial runout error and the gear tooth profile error, base pitch error with the consideration of machine tool movement error are carried out respectively. Utilizing the counterpart rack law, the gear tooth profile equation enveloping from involute curve hob tooth profile equation is generated, quantitative mapping relational model of hob pitch error and pitch deviation based on differential geometry and envelope principle is builded. At the same time quantitative mapping relational model between hob helix error,radial runout error of hob installation angle and the gear tooth profile error are established respectively. According to the geometric relations between gear tooth profile error and gear base pitch error, the mapping rule of base pitch error is calculated based on the factors mentioned above. A joint equation model between the above three main errors of gear hob and the tooth profile error based on Gaussian distribution with the consideration of machine tool movement error are builded. At last the correctness of the above model by comparing the result of model simulation method with empirical data is verified, so the essential mapping rules of hob error and the main factors which affect tooth geometric precision such as tooth profile error, base pitch error with the consideration of machine tool movement error are revealed, thus a theoretical foundation for roll cutting gear with higher precision is layed.

Heat Flux and Temperature Distribution in Gear Hobbing Operations

Thermal deviations in gear hobbing are one of the main reasons for wet machining. To reduce lubricant, especially for dry machin- ing of large modulus, it is necessary to compensate these thermal deviations.Gear hobbing is a very complex technology, where chip geometries are changing continuously. To measure cutting forces during machining a simplified fly cutting test is commonly used. Within this study a modification of the fly cutting test was necessary to enable the measurement of temperature and temperature distribution in the gear during the process.For a better understanding, in addition numerical simulations are performed to calculate the heat flow and thermal distribution. Thereby, a two step simulation procedure was applied. The generated heat during chip formation was evaluated in the first step. The second step is a heat flow simulation, where the generated heat from the first step was used. In this simulation part, the heat flow and thermal deviations are calculated, and also chip removal is taken into account. Thereby, different simulation strategies are used to reduce the calculation time, which will be described within this paper.The results are showing a good agreement between the measured and calculated temperature fields in chip formation and heat flow.

A Gear Cutting Predictive Model Using the Finite Element Method

Current processes for producing transmission gears involve hobbing, milling or shaping of a forged stock to obtain the gear shape. Gears are typically formed by hobbing tools made from solid tooling material, such as tungsten carbide, and have dozens of teeth. The gear hobbing process entails several teeth in cut simultaneously. Generation of in-volute tooth profiles results in varying chip loads from pass to pass. In this paper, details are provided for a finite element-based model of gear hobbing and milling processes. The model explicitly meshes gear cutter geometries with dozens of teeth. These cutters are used to simulate the complicated kinematic motion between tool and workpiece. Thermo-mechanical coupled calculations within an explicit dynamic formulation are per-formed on the tool and workpiece during chip removal. The complex geometry of involute tooth profiles results in complicated contact scenarios on the evolving workpiece geometry during tooth profile generation. Tooth-workpiece-chip contact is enforced rigorously and is particularly complicated with the confined space of gear hobbing. Advanced adaptive meshing strategies are developed and employed to maintain the resolution of the tool-workpiece interaction while multiple teeth are in contact. Cutting forces, temperatures and stresses in the tool and workpiece are predicted for steel workpiece materials. Models are validated through a set of initially simplified experiments where incremental complexity is added, allowing for direct comparison between predicted and measured forces and chip shapes.

Effect of Coating Film on Tool Life of High Speed Steel Hob in Dry Gear Hobbing

This paper presents the results of practical dry hobbing experiments performed on a traditional productive type of hobbing machine. The HSS (high speed steel) hobs with different combination of coat materials and coating states display significant variations in tool life. A TiN coating hob demonstrates the best cutting performance although the coating cost is the lowest. From these experimental results, two meaningful conclusions are obtained. One is some coat materials proper to HSS milling cutters are not always suitable for a HSS hob applied in dry hobbing. The other is that for a coated HSS hob, a cutting performance and tool life satisfactory to practical application is possible when using the hob to carry out dry hobbing on a general type of hobbing machine, if the coat film on the hob teeth is proper both in material and coating form.

Study on High-Order Elliptical Gear Parametric Design, Automatic Modeling and Motion Simulation

In this paper, the high-order elliptical gear design principle and methods were studied based on Solidworks API to accomplish high-order elliptical gear parametrical design, machining simulation and automatic modeling. Elliptical gear pair simulation was carried out for verification. The high-order elliptical gear modeling method proposed was to use gear hob type of envelope processing method with the advantages of being able to process concaved pitch curve of high-order elliptical gear. The idea of this design process can also be extended to other types of non-circular gear design and modeling.

The Influence of the Center-to-Center Distance on the Accuracy of the Serration with the New Gear Hob

A gear meshing mathematical model was set up according to the tooth profile normal line method. The influence of the gear cutter-workpiece center distance on the tooth profile accuracy was discussed in spur gear cutting using a new type of gear cutter, with the center distance errors being ±0.005, ±0.01, ±0.02 and ±0.04 respectively. The results show that the machined tooth profile errors at the root circle is less than 1μm, while errors at other parts of the tooth profile are even smaller.

Experiments and Study of the Static Rigidity of Workpiece Spindle of Direct-Drive Gear Hobbing Machine

Static rigidity of workpeice spindle component is a very important index of the rigidity of derict-drive gear hobbing spindle unit. In this study, the static rigidity of workpiece spindle system were analyzed through a finite element method (EFM) by building geometric models and studying the deformation when radial cutting force was imposed. Experiments on workpiece were carried out with and without the assistance of tailstock center separately to measure the changes of the static rigidity of spindle. The results prove a less change of the static rigidity of spindle when with the assistance of tailstock center, which helps to ensure the accuracy and surface roughness of a workpiece.

4-Axis CNC Machine Tool for Relief Grinding Sphere Gear Hob

A new 4-axis machine tool, which is used for relief grind of sphere gears hob including spherical hob, elliptic hob and arc surface hob, is developed. The principle of relief machining of spherical hob is introduced first. Transmitting system, numerical system and some key techniques are then introduced. The machine tool can be reconfigured in machining of arc worms and spatial cams beside of machining of spherical hob. Four forms of the machine tool for machining different workpiece are also introduced. DOI: http://dx.doi.org/10.11591/telkomnika.v10i7.1557

The Optimization of Tooth Form Fitting Error on Worm Type Shaving Cutter

In order to solve the flank concave problem of the rotary gear shaving cutter, a new worm type shaving cutter has been manufactured, which will be used on a gear hobbing achieving freedom shaving. And its tooth precision can reach 6-7 level. The main contents includes the worm normal section curve equation of the worm type shaving cutter involutes, the optimization of tooth fitting error and the linear fitting of the tooth curve of the normal section by the MATLAB genetic algorithm toolbox. According to GB/T6084-2001 hob series standard, the results showed that the error theory is less than 1/6 of the AA level.

Finite-Element Analyze of D-Post on Numeric Controlled Gear Hobbing Cooperative Working Machine Based on ANSYS

This paper completed the CNC milling machine upright post joint mechanics modeling, and using ANSYS software column models are static and modal analysis, according to the results of analysis to find out the weak link in the design, and puts forward the improvement methods.