Gear Forging Research Articles

Billet Design Optimization of Helical Gears Precision Forging Based on Response Surface Method and FEM Simulation

Billet is designed by utilizing the flow relief-hole principle to improve the dimensional accuracy during the precision cold forging of helical gear . An optimization method for the initial diameter of the relief-hole was proposed based on the finite element method(FEM) and response surface method (RSM). The degree of uniformity of effective strain in helical gear precision forging was considered as the optimal objective. The empirical equation built through Response Surface Method shows the relationship between the the initial diameter of the relief-hole and the degree of uniformity of effective strain. The optimal diameter is obtained through gold section method based on the empirical equation . The optimal result has been verified by using the commercial software DEFORM 3D.

Rotary forging with double symmetry rolls

A novel metal plastic forming technology, namely rotary forging with double symmetry rolls (DSRs) is presented in comparison to more conventional single roll rotary forging. Based on a reliable three-dimensional elastic–plastic dynamic explicit finite element model, the fundamental deformation characteristics of cold rotary forging with DSRs of a cylindrical workpiece are made clear. Meanwhile, the interactive effects of two main processing parameters, feedrate v of the lower die and rotational speed n of the two upper dies on the forming process have been comprehensively revealed. As a specific case, hot rotary forging of a spiral bevel gear was analysed and an experiment was carried out on a developed hot rotary forging press with DSRs. The simulation results are in good agreement with the experimental ones and demonstrate that rotary forging with DSRs has a potential prospect in forming a complex spiral bevel gear. The results of this research help to better understand the advanced metal plastic forming technology of rotary forging with DSRs.

Three-Dimensional Numerical Simulation and Forming Investigation for Net-Shape Forging of Spur Gears

In this paper, a new precision forging technique composite processing of the moving-die forging and divided flow forging process to form the spur gear is introduced. A systematic investigation of the floating-relief method process is performed by using finite element numerical simulation. The stress distributions on the workpieces were obtained. The closer the die teeth corner is, the higher stress value results can be acquired. And the effective stress is concentrated in spur gears forging die cavity corner. It was found that the floating-relief method forging process with upper and lower convex punches control the material flow effectively and the tooth cavity is filled successfully during the performing forging and final forging. The proposed method can serve as preconditions to analyze the abrasion and fatigue of spur gears forging die. The obtained results can offer valuable guidelines for gear precision forging experiments and practical process planning.

Finite Element Analysis and Optimization of Deformation Behavior for Spur Gear Warm Forging Process

Recent years have therefore seen growing interest in gear precision forging to net-shape form of forge bevel, spur and helical gears, as an alternative to conventional manufacturing. In this paper, gear precision forging processes are simulated by using metal forming finite element code DEFORM-3D. The investigations of gear precision forging processes are conducted with perform forging and final forging processes. The processes of completely closed-die forging, moving-die forging and central divided flow forging processes are investigated for spur gears. The effect of different processes on the distribution of effective stress in the workpieces and forging loads are given. The purpose of this study is to introduce a new method, a so-called floating-relief method which applied to the forging of spur gears. It indicated that the flowing properties of the gear billet have a higher improve than that of conventional forging process. And the forging load obtained by using this new precision forging technology is decline sharply. The floating-relief method for gear precision forging is a sound process in the practical application.

Numerical and experimental investigation of cold rotary forging of a 20CrMnTi alloy spur bevel gear

Due to the complex three-dimensional (3D) geometry and tooling design, mass production of precision spur bevel gears by machining or conventional forging technology is impeded by numerous stubborn barriers to date. Cold rotary forging, an innovative incremental metal forming process, has great potential to improve the current situation owing to its flexibility and low tool load requirement. In the present study, a sound 3D rigid-plastic finite element (FE) model of cold rotary forging of a 20CrMnTi alloy spur bevel gear is developed under the DEFORM-3D platform. To ensure the precision of the proposed FE model, a series of experiments are well performed for the identification of the mechanical properties of 20CrMnTi alloy and the realistic friction conditions prevailing at the die-workpiece interface. By utilising this FE model, the workpiece geometry is optimised with the intention of achieving a better filling of gear shape and a lower forming load requirement, and then the distribution of different field-variables such as flow velocity and effective strain are thoroughly investigated. For verification purposes, the cold rotary forging experiments of 20CrMnTi alloy spur bevel gears are subsequently conducted. Good agreement between the experimental results and the simulation ones is highlighted by comparing the gear shape after cold rotary forging and the axial forging force, which validates employed model.

Effects of temperature and grain refinement on the closed-die forging of a micro gear

Temperature and grain size are important factors for material flow behaviour and die filling in metal-forming processes. Their impacts are even greater in micro metal forming when the process is scaled from conventional down to micro dimensions because so-called size effects cause inhomogeneous material characteristics, leading to inaccuracy of shape and scatter of product properties. This study investigates the effects of temperature and grain refinement on the closed-die forging of a micro copper gear with a module of 0.4 mm, 12 teeth, and an integral shaft. A micro forging system equipped with heating devices was developed for conducting the experiments at elevated temperature. Moreover, equal-channel angular extrusion and heat treatments were applied to control the mean grain size of the copper in a range between 4 and 46 μm. The experimental results show that the increase of forming temperature and the grain refinement can improve material flow behaviour, resulting in better filling of tooth cavities, more uniform hardness distributions, and smoother tooth profiles.

A New Punch Profile Design for Orbital Forging of a Bevel Gear Part

The difficulty in forging of bevel gear with an outside diameter larger than 75mm is due to the high forming load requirement. In this paper, a new intuitive method for the punch and preform design of the bevel gear warm orbital forging is proposed to lower the forging load and improve the die filling. The geometry of the forged bevel gear are divided into characteristic features and mapped to the main dimensions of the preform design. The exact dimensions of the preform are determined utilizing constraints of the volume constancy and the section centroid balance. The surface of punch tip is designed using the section profile described by a Bezier curve with five control points which are related to the preform and the forged part geometry simultaneously. The forming process was analyzed via the FEM simulation. The die stress was also calculated to prevent die failure and improve tool life. A PXW-200 orbital forging press was adopted for the experimental tests of the proposed designs. The unfilled area at the teeth faces were examined via the laser scanner. The experimental results of the maximum unfilled distances were varied from 0.3 mm to 0.8mm depending on the different punch tip profile design. The predicted tooth profiles were in good agreement with the experimental measurements.

Development of self-adjusting hydraulic machine for combination forming of upsetting and extruding

In the paper a self-adjusting hydraulic machine for combination forming of upsetting and extruding is systematacially presented in terms of mechanical principle, design principle, machine construction, design of the key components and working routine. The machine is designed with the following features: The lower movable beam is adjusted by the ejecting cylinder, the upper upsetting beam is reset by the backstroke slide rods, and the upsetting cylinders communicate with the gas-liquid accumulators. These features make the machine conformation compact, save both the backstroke cylinder of the upper upsetting beam and the upsetting cylinder of the lower movable beam, and simplify the hydraulic system. Furthermore, the machine can resolve such problems as incomplete filling at the addendum position, microcracks at the dedendum position, greater force and lower die life during precision forging of spur gears.

Die design for cold precision forging of bevel gear based on finite element method

The finite element analysis (FEA) software Ansys was employed to study the stress state of the dies of both plane and non-plane parting face structures with uniform interference and the die of plane parting face structure with non-uniform interference. Considering the symmetry of the die, a half gear tooth model of the two-ring assembled die with 2.5 GPa inner pressure was constructed. Four paths were defined to investigate the stress state at the bottom corner of the die where stress concentration was serious. FEA results show that the change of parting face from non-plane to plane can greatly reduce the stress at the teeth tips of the die so that the tip fracture is avoided. The interference structure of the die is the most important influencing factor for the stress concentration at the bottom corner. When non-uniform interference is adopted the first principal stress at the corner on the defined paths of the die is much lower than that with uniform interference. The bottom hole radius is another important influencing factor for the corner stress concentration. The first principal stress at the corner of the plane parting face die with non-uniform interference is reduced from 2.3 to 1.9 GPa when the hole radius increases from 12.5 to 16.0 mm. The optimization of the die structure increases the life of the die from 100 to 6 000 hits.

904 曲がり歯かさ歯車の鍛造加工法の研究 : 軸角任意の場合(模索潤滑設計I)

904 曲がり歯かさ歯車の鍛造加工法の研究 : 軸角任意の場合(模索潤滑設計I)

Prediction of maximum forming load and billet dimensions using an abductive network and finite element method simulation of a near net-shaped helical gear forging

This study applies the finite element method (FEM) in conjunction with an abductive network to predict maximum forging load and billet dimensions during near net-shaped helical gear forging. Maximum forging load and the billet dimensions are determined for different process parameters, such as modules, number of teeth, and helical angle of the near net-shaped gear forging, using the FEM. The abductive network is then utilized to synthesize the datasets acquired from numerical simulations. Finally, prediction models are established for predicting maximum forging load and the billet dimensions under an appropriate range of process parameters.

Effects of friction laws on metal forming processes

In this paper, the Coulomb friction law and the constant shear friction law were compared and investigated in detail using a rigid-plastic finite element method with emphasis on their application in bulk metal forming. The ring compression test for two different materials was used to evaluate the two friction laws, and then their effects on metal flow lines and forming loads for various friction-sensitive metal forming processes including strip rolling, ring gear forging, multistep extrusion, and pipe shrinkage and expansion were investigated. It was shown that considerable differences exist between the two friction laws, especially in friction-sensitive metal forming processes.

ANALYSIS AND DESIGN OF PINION WITH INNER HELICAL GEAR BY FEM

Cold forging of pinion gear with shape of outer spur gear and inner helical gear have been investigated in this study. A numerical analysis for preform design substituting cutting process in gear forging was developed by means of upsetting process. By using the finite element program DEFORM-3D, the analysis is carried out. Using this simulation, the preform of pinion and helical gear forging process were designed. The suggested process is verified by experiment. Compared to the traditional CNC processing, the upsetting process can form a preform without cutting, which leads to shorter forming time and reduce material usage.

Numerical Simulation Analysis on Cold Closed-Die Forging of Differential Satellite Gear in Car

The cold closed-die forging process of the gear is a kind of new technique of the precise forming of gear in recent years. In this paper, the cold closed-die forging process of differential satellite gear in car was analyzed through numerical simulation method. Forming mold was designed with Pro/E Wildfire2.0 which included four components : upper punch, lower punch, tooth shape upper die and lower die for Normal Cone. The three-dimensional models of satellite bevel gear mould were built and imported into numerical simulation software DEFORM-3D. Because the gear has the uniform circumferential features, in order to save time and improve the accuracy, only one tooth was simulated, and the full simulation outcome of 10 teeth was mirrored from this one. Through the numerical simulation analysis of DEFORM-3D, the instantaneous deformation and stress filed were gained. Forming defects were forecasted and the cold closed-die forging rule for satellite gear used in car was obtained which can provide effective references for no-flash cold forging process of planet bevel gear and the mold design.

Hot Forging Process Design Optimization Based on Approximate Model and FEM Simulation

Technology and die design are very important in the development of forging products due to its great influence on the quality, cost and manufacturing efficiency of the final products as well as the life of the forging die. In the environment of the severe competition, how to improve the quality of forging technology and die design, to reduce the product cost and ultimately to enhance competitiveness of the forging factory are the problems that forging technology and die designer have to solve. In order to improve the quality of forging technology and die design, a design optimization method based on approximate model (response surface model) and FEM technique for hot forging process is proposed in this paper. During design optimization process, finite element analysis is incorporated to calculate the objective function and check the design alternatives. Design of experiment (DOE) method is used to collect sample points and calculate the polynomial coefficients of response surface model, and approximate model is used to calculate the optimum search direction. Finally, a case study is conducted for a gear workpiece hot forging process. The objective function is the degree of uniformity of equivalent-strain, which can be defined as mean square deviation of the equivalent-strain in each element and the average equivalent-strain of all elements, and the design parameters are the initial H0/D0 ratio of billet and the key dimensions of the die. Then the design optimization mathematical model is established. The result shows that the objective function value is dropped from 0.7914 and converges at 0.4843 within 17 iterations, the optimal design parameters are obtained.

Analysis of Metal Flow and Technology Improvement on Gear Forging

The metal flow rule in the conventional cold forging process of spur gear is investigated.Inorder to reduce the friction resistance and improve the non-uniform deformation,radial rigid translation flow mode and axial uniform flow mode are proposed. Based on the rigid translation mode,a novel gear finish forging technology is put forward.From the results of numerical simulation and physical experiment,the hypothesis of rigid translation flow mode is verified.The effect of two key process parameters (the tooth height after preforming and friction coefficient) on forming load is analyzed,and the superiority of the novel forming tech- nology is further proved from the analysis results.To improve the non-uniform flow mode,the novel technology is further improved with unsymmetrical punch.Finally,the peak value of conventional forging process is also simulated to compare the novel forming technology,and the result shows that the forming load can decrease significantly with the new technology.

A contribution on the study of cold forging of steel helical gears

In this work it was designed a cold forging tooling for the manufacturing of steel helical gears by lateral extrusion. The results obtained from forging tests and numerical simulation are presented and demonstrated that this process is very capable to achieve in one step parts with excellent overall quality.

Application of CAE in cold forging and heat treatment processes for manufacturing of precision helical gear part

In this study, numerical simulations, using the general-purpose process simulation software DEFORM-3D/HT, were carried out for the design of the cold forged precision helical gear used for the automotive steering part. The helical gear forging was carried out using the designed die set. From the simulation results, forming load, normal pressure, effective strain distributions on the workpiece, and stress distributions on forging dies were investigated. The predicted workpiece geometry showed good agreement with experimental result. Also, the heat treatment processes of the forged helical gear parts were simulated and compared with the experimental results. Highly accurate heat transfer coefficients considering the complex boundary heat transfer were applied in the current simulations to improve the simulation accuracy. The inverse calculation technique was used to find out the accurate heat transfer coefficients to minimize the difference between simulation and experiment. From the simulation result, the microstructure distribution and geometrical change of teeth were investigated for various quenching media, such as oil, water, and polymer.

The prediction of maximum forging load and effective stress for different material of bevel gear forging

The manufacture of gears by applying hot or cold bulk forming processes is a quite widespread production method due to its well-known basic advantages such as material and time cost reduction and the increased strength of the teeth. However, the associated process planning and tool design are more complicated. In the precision forging of gears, the workpiece volume, the die design, the power requirement and careful processing are more critical than traditional forging technology. For complete filling up, predicting the power requirement is an important feature of the near net-shape forging process. In this paper, a finite element analysis is utilized to investigate the material properties such as yielding stress, strength coefficient and strain hardening exponent effects on forming load and maximum effective stress. The adductive network was then applied to synthesize the data set obtained from the numerical simulation. The predicted results of the maximum forging load and maximum equivalent stress of bevel gear forging from the prediction model are consistent with the results obtained from FEM simulation quite well. After employing the prediction model one can provide valuable references in prediction of the maximum forging load and maximum equivalent stress of bevel gear forging under a suitable range of material parameters.

Numerical analysis and design of pinion with inner helical gear by FEM

In the design of the cold forging process one of the most important tasks is the determination of the required number of processes. Preforming in incremental steps is aimed at achieving high accuracy of the forged part, high quality of the surfaces and also decreasing the die damage during the forging process. Cold forging of pinion gear with shape of outer spur gear and inner helical gear have been investigated in this study. A numerical analysis for preform design substituting a cutting process in the gear forging was developed by means of upsetting process. By using the finite element (FE) program DEFORM-3D, the analysis is carried out. Using this simulation, the preform of the pinion and helical gear forging process was designed. The suggested valuable information regarding the forging process shows a successful attempt. The suggested process is verified by experiment. Compared to the traditional computer numerical control (CNC) processing, the upsetting process can form a preform without cutting, which leads to shorter forming time and reduced material usage.