Realisation and application of size dependent FEM-simulation for deep drawing of rectangular work pieces

Abstract

Deep drawing provides a great application potential for the manufacturing of parts with complex shapes, even in very small dimensions. The friction between blank and forming tool is one of the decisive affecting factors for this process, since it affects the punch force as well as the surface quality of drawn workpieces essentially. Using scaled deep drawing it was found in our previous works, that the friction coefficients increase significantly with decreasing process dimension. This is called tribological size effect, which must be taken into account during the development of micro deep drawing. In this work, the tribological size effect is further investigated in deep drawing of work pieces with more complicated geometry, i.e. rectangular cups. In this investigation, scaled experiments are carried out with different rectangular punches (from 1.5 × 0.75 mm² to 20 × 10 mm²) and the blank material Al99.5 with different thicknesses (from 0.015 mm to 0.2 mm). Size dependent FEM-simulation for this process is performed, at which the friction functions from scaled deep drawing of circular parts in previous work are applied. The comparison of both the simulated and experimental punch force-stroke-curves shows that the friction functions from deep drawing of circular parts is also valid for the deep drawing of rectangular work pieces. The size-dependent FEM-simulation with application of friction functions can be used to determine an optimum blank shape for a flange free rectangular micro workpiece (punch 2 × 1 mm²), which is later validated in experimental investigation.