Extrusion die for making a double-skin honeycomb substrate

An extrusion die assembly for making a double-skin honeycomb structure, comprising:

• an inner cell forming die having a central region and a peripheral region, the central region comprising an array of inner slots cut to define an array of inner pins and an array of central feedholes in communication with the array of inner slots, the peripheral region comprising an array of peripheral feedholes;
• a skin forming mask mounted coaxially with the inner cell forming die;
• and
• at least one outer cell forming die mounted coaxially with and interposed between the inner cell forming die and the skin forming mask, the outer cell forming die having an array of outer slots cut to define an array of outer pins, the outer pins being spaced radially from the central region to define an inner skin slot, the inner skin slot being in selective communication with the peripheral feedholes, the outer pins being spaced radially from the skin forming mask to define an outer skin slot, the outer skin slot being in selective communication with the peripheral feedholes through an opening in the outer cell forming die.