EXTRUSION DIE DESIGN FOR MULTIPLE STRIPES

Two numerical approaches have been applied to examine the possibility of adding shims to conventional extrusion dies such as T-dies and coat -hanger dies to produce multiple stripes. The first numerical approach is based on a one or two-dimensional lubrication approximation and th e second one is the three-dimensional finite element simulation. Both approaches are applicable, but the lubrication approximation is accura te and much simpler to use. The extruded stripes are assumed to obey a non-Newtonian power-law model. It has been found that the T-die with a shim can produce multiple stripes of acceptable uniformity, irrespec tive of the strip numbers and widths and the power-law index The coat- hanger die with a shim did not deliver multiple stripes with good unif ormity. Adding an outer manifold to the coat-hanger die can serve as a n effective means to reduce flow nonuniformities.