Experimental and finite element analysis to predict the dimensional changes of a cold-forged spur gear

Abstract

The dimensional tolerance of spur gears for automobiles is within the range of several micrometres. Therefore, to manufacture these gears by cold forging, dimensions should be controlled in the same range. The dimensional changes by the various forging variables should be analysed and compensated into the forging tool. Computer-aided engineering (CAE) would be appropriate for investigating the effects of variables. However, the realistic finite element modelling (FEM) techniques should be confirmed and used to predict the dimension of the forged part in the order of micrometres. As realistic modelling considers the elastic characteristics of both workpiece and die at unloading and ejecting stage, threedimensional analysis for spur gears may often encounter difficulties in solving time and convergence. In this study, dimensional changes for cold-forged parts of spur gears were investigated by experimental and FEM analysis, after modelling to obtain desirable FEM results had been studied by closed-die upsetting. The dimensional changes of involute curve for the spur gear can be analysed from the FEM results during the whole forging stage; and give an index of a modified involute curve of the forging tool for improving gear profile accuracy.