Composite Co-extrusion Decking Co-extrusion decking is the production of industry's most advanced extrusion molding technology, which is wood plastic surface coated with co-extrusion.wood plastic composite co-extrusion machine/WPC decking co. 2, SJ45 single screw extruder.--- for outside layer. 3, wpc co-extrusion decking moulds. 4,calibration table, 5, catapillar haul-off and cutter.Co-Extruded Composite Decking Explained | Wood and Beyond Blog Feb 19, 2018. Co-extruded technology is the most advanced in the composite decking industry. With a co-extruded surface, your deck can have superior.What is the difference between normal classic WPC boards and Co. Normal deck boards are the first generation composite decking boards. Co-extrusion or capped deck boards are WPC second generation boards.