| Abstract: | Deformation during cooling and take-up of rectangular, triangular and T-shaped profiles were investigated. Experimental results show that there is an excellent agreement between changes in a cross-section dimension and prediction from the theory for various take-up speeds. The correlations decrease in the case where other process variables such as different melt temperatures and output rates are involved. Based on undrawn sample measurements, it has been concluded that to a high degree of approximation only a scaled-down change in shape occurs along the drawing path after die swell is completed. Industrial practices in handling profiles during cooling and take-up which may cause deviations from geometrically similar deformation were examined. Metal guides and local cooling by small water streams along the drawing path were used to impose shear forces on the profile. It was found that the effects of such shear forces has been small in comparison with the effects of elongational stress as indicated by only slight, if any, deviation from geometrically similar changes in cross-sections. Based on the data obtained, it is concluded that feedback control during profile drawing to give correct size is feasible based on monitoring a single dimension. The correct shape can, however, be obtained only by choice of the proper die geometry and other extrusion conditions. |
