Improved part quality in complex deep drawing using variable draw bead motion control

Résumé

The use of locally varying draw bead motion to remove complex deep drawed part defects and improve formability has been extensively studied in the academic research community over the last twenty years. The new idea of using variable draw bead motion is conceptually simple: if wrinkle is starting to form, the draw bead penetration is increased thus relatively quick (typically 0,5-0,8 sec.). The present papers describe a FE analysis of the effect that different variations of the draw bead position have on the rate σ_22/ σ₁₁ , considered a criterion for wrinkles developing process. The stress   σ ₁₁ and σ ₂₂ , represent Cauchy stress tensor components, which usually are a tension, respectively compression stress in one of critical zones of the part. When this rate is higher than his limit value, the compression stress is dominant and the wrinkles appear. The motion of the draw bead can control the flow of the material in die cavity and improve quality of the part. An optimal motion of draw bead is obtained using FE analysis.