An extruder apparatus and method for producing an extruded tubing having varying
inner dimensions without changing the outer dimensions. The tubing is forced from
the die face of an extrusion head having an extruder die and an internal mandrel
determining the outer and inner dimensions, respectively, of the extruded tubing.
The outer dimensions of the mandrel varied by the user to change the inner dimensions
of the extruded tubing. A pressure is maintained in the extruded tubing to prevent
its collapse and that pressure is changed based upon the change of the external
dimensions of the mandrel and the wall thickness of the tubing. In one embodiment,
the mandrel is comprised of a core and a plurality of telescoping sleeves. Each
sleeve is movable between a retracted position where the sleeve is displaced away
from the die face and an extended position where sleeve is at the die face. There
may be multiple mandrels in the case of multi-lumen catheters.
