Backward can extrusion

  • Danckert, Joachim, (Projektdeltager)



    Backward can extrusion is a widely used forming process for the manufacturing of cans e.g. aerosol cans. The punch used in the backward can extrusion process is commonly made according to the ICFG recommendations (International Cold Forging Group). According to these recommendations the punch should be made with a cylindrical punch land. Analysis of the pressure distribution on the punch land shows that the backward can extrusion process is, when made with a cylindrical punch land, in a state of unstable equilibrium; the punch is not self-centring and any disturbance will cause the process to become unstable. The analysis has been carried out using classical theory of plasticity and FEM. Analysis carried out shows that if the punch land instead of being cylindrical is made slightly curved, e.g. circular profiled, the robustness of the backward can extrusion process can be improved. With a slightly curved punch land a small tilt of the punch land e.g. due to a slight deflection of the punch or due to inaccurate manufacturing will only have a minor effect on the quality of the produced cans. The manufacturing of thin walled aluminium cans with a wall thickness of 1 mm has been carried out experimentally. With a punch designed according to ICFG?s recommendation the can wall thickness varied +- 0.15 mm. With a punch with a slightly curved punch land the variations in can wall thickness were greatly reduced; the variations were less than +- 0.6 mm. Aalborg University has applied for a patent regarding the new punch design. A brochure describing the patent has been made, and in 2004 the University will distribute the brochure to relevant companies with the purpose of selling licenses. (Joachim Danckert, Department of Production, AAU)
    Effektiv start/slut dato31/12/200431/12/2004