Analysis of the elastic characteristics at forging die for the cold forged dimensional accuracy

Systematic understanding of dimensional difference between forging tools and forged components is tried by both experimental and FEM analysis. The difference is mainly influenced by the elastic deflections of the die and the elastic recovery of the forged part. Since the die is continuously deformed during the loading, unloading, and ejecting stage, the elastic strains of die are measured at each forging stage using strain gages. For a comparison with the measured elastic strains, two FEM modeling approaches are tried by using a commercial FEM-code, DEFORM-2D™. The first of the two modeling approaches regards the die as a rigid body at an entire forging cycle, and pressure from the deformed part is used as the die stress analysis. For the second approach, it is assumed that both the die and workpiece are considered as a deformable body during the forming simulation. Therefore, the elastic strain of tool is calculated at each deformation step. The FEM analysis result from the consideration of the die as a deformable body are well agreed with the experimental results. As well, the method considering a shrink-fitting factor is discussed. When the shrink-fitting factor is adequately compensated, the analyzed dimensional difference results are well fitted to the measured data within the range of 1 μm.