Precision Forging Of Gears Research Articles

An investigation of involute and lead deflection in hot precision forging of gears

A theoretical model is presented in the paper for predicting involute profile deflection in hot precision forging of gears. This model is a function of a number of material and processing parameters, including the thermal expansion of the die, thermal contraction of workpiece, elastic expansion of the die during forging, and workpiece recovery after ejection. To improve the accuracy of the hot forged gear tooth, an equation set to define modified involute that is used to design the die tooth has been proposed based on the model. The distribution of deflection along the involute was also predicted using the commercial FE code, PRO-E. The deflection characteristic of the toothed die through the tooth width was analyzed by combining the theoretical method and FEM to investigate the non-uniform deflection. The dimension of the forged gears was measured using a gear measurement machine WGT3000. A close agreement between predicted and measured tooth involute profiles was obtained, which validated the involute deflection prediction model. The measured lead error also verified the model for deflection non-uniformity through the tooth width. The results can provide a guide for die tooth designs to improve the dimensional accuracy of hot forged gear teeth.

Design of relief-cavity in closed-precision forging of gears

To reduce the difficulty of material filling into the top region of tooth in hot precision forging of gears using the alternative die designs, relief-cavity designs in different sizes were performed on the top of die tooth. The influences of the conventional process and relief-cavity designs on corner filling, workpiece stress, die stress, forming load and material utilization were examined. Finite element simulation for tooth forming, die stress and forming load using the four designs was performed. The material utilization was further considered, and the optimal design was determined. The tooth form and forming load in forging trials ensured the validity of FE simulation. Tooth accuracy was inspected by video measuring machine (VMM), which shows the hot forged accuracy achieves the level of rough machining of gear teeth. The effects of friction on mode of metal flow and strain distribution were also discussed.

Precision forging of spur gear by flow control forming method

In order to reduce the final forging load of spur gear precision forging, several alternative die designs that use a ring billet are put forward. The influence of different designs on metal flow and load requirements is examined through finite element simulation and experiments. A new precision forging technology is then developed, which includes a two-step forging process to control metal flow in the die cavity. Well-shaped products can be forged successfully by using a lower forging load than that of conventional forging.

Prediction of Forming Load for the Helical Gear Precision Forging by BP Neural Network

Precision forging of the helical gear is a complex metal forming process under coupled effects with multi-factors. The high forming load is required to fill the teeth corner, which significantly causes failure, plastic deformation and wear of dies. The maximum forming load during precision forging helical gear is calculated by the finite element method (FEM). Combining the FEM simulation results with the artificial neural networks (ANN), backward propagation (BP) neural network is trained using the data of FEM simulation as learning sample. The trained BP neural network is validated using test samples and used to predict the maximum forming load under the different deformation conditions. The results show that the predicted results agree well with the simulated ones, the differences of prediction results exhibit low value, the predicted precision satisfy the request of industry.

Numerical Investigation of the Influence of Friction, Module and Number of Teeth in Forging Process of a Spur Gear

Among all manufacturing processes, forging has a special place because in this technology, parts with desired mechanical properties and minimum waste of material can be produced. Gear is one of the components of machinery which should have special features such as high strength-to-weight ratio, fatigue and surface abrasion resistance, etc. So, comparing with other methods, gear forging provides above requirements. Moreover, precision forging of gears is one of the appropriate methods for producing this piece because it saves material consumption and reduces machining costs. Extensive studies are carried out on this production method but there are also many aspects to be investigated. Since, without having knowledge of the influence of parameters such as friction conditions, material properties, and geometry of work piece on the mechanics of the process, optimal design of the form, selection of appropriate equipments, and prediction and prevention of defects that may occur is not possible, modelling the process for computer simulation has been given much attention in modern technology of metals forming. The purpose of this study is to examine factors such as number of teeth, modulus and coefficient of friction on load, and the force required for the process which has been studied using finite element method.

Effect of Mandrel Exchange on the Precision Forging of Spur Gear

In order to reduce the spur gear precision forging load and prevent load to rise sharply in final forging, on the basis of analysis the distribution of contact pressure of cylinder upsetting, mandrel exchange technology is put forward. As a result, the material always has free space to flow. The tool-set and experiment scheme are designed, finally, the scheme is further validated by Deform-3D, and the results show that the validity of mandrel exchange technology to reduce the load in gears precision forging.

Multi-objective optimization of process parameters for the helical gear precision forging by using Taguchi method

Precision forging of the helical gear is a complex metal forming process under coupled effects with multi-factors. The various process parameters such as deformation temperature, punch velocity and friction conditions affect the forming process differently, thus the optimization design of process parameters is necessary to obtain a good product. In this paper, an optimization method for the helical gear precision forging is proposed based on the finite element method (FEM) and Taguchi method with multi-objective design. The maximum forging force and the die-fill quality are considered as the optimal objectives. The optimal parameters combination is obtained through S/N analysis and the analysis of variance (ANOVA). It is shown that, for helical gears precision forging, the most significant parameters affecting the maximum forging force and the die-fill quality are deformation temperature and friction coefficient. The verified experimental result agrees with the predictive value well, which demonstrates the effectiveness of the proposed optimization method.

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.

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.

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.