Method and apparatus for forming a uniform skin on a cellular substrate

Novel apparatus is disclosed for forming a skin on an extruded honeycomb structure, wherein detrimental distortion of the peripheral cells is eliminated to thus provide a virtually distortion free honeycomb structure with an integral skin. Batch material is supplied for forming the central cellular structure, and a metered flow of skin-forming batch material is transitioned by the apparatus from a predominantly transverse flow to a predominantly longitudinal flow so as to minimize the distortion of web portions of the peripheral cells. In addition the apparatus subjects the skin-forming batch material to a first or primary flow path reduction in the form of flow depth and then, as it is knitting with peripheral web portions of the central cellular structure, the apparatus subjects such batch material to a second or secondary flow path reduction the form of reduced cross-sectional area, so as to effect a complete knitting thereof while still within the extrusion die. A unitary cellular structure with an integral skin is then discharged from the die with improved structural and strength characteristics.