PE/PP WPC profiles are typically extruded in three ways:
One-step technology (small-scale projects): tandem WPC extrusion line (compounder + profile extruders) process premixed WPC blend without preliminary pelletizing.
Two-step technology (bigger and expandable scale projects): wood plastic pelletizing extruder process premixed WPC blend into WPC pellets (granules). Pellets are extruded into WPC lumber with twin or single screw WPC extruders.
Direct extrusion (bigger and expandable scale projects): WPC formulation components (wood powder, polymer) are fed on-line into WPC profile extruder through automatic dosing system.
One step WPC extrusion (for small-scale WPC projects)
No preliminary WPC pelletizing - you save on initial investments, power costs, workshop area, salaries as you skip using separate WPC pelletizing line.
Hot melt enters WPC extruder directly, thus reducing screw and barrel wear, while providing higher WPC lumber quality (as polymer is melt/degrades only once).
No need of extra drying of wood fiber - you save on costs and shop area.
Co-rotating twin-screw compounder provides for homogenous WPC mixing and compounding exhausting moisture through the barrel vents.
Wood powder with moisture content up to 8% can be used without extra drying.
Two step WPC extrusion (for bigger-scale WPC projects)
Preliminary pelletizing provides for more consistent WPC, stable extrusion process and higher capacity. Though, of course, it will require separate WPC pelletizer with additional space, power, personnel.