Screw and barrel wear costs compounders both pellet quality and output. Wear increases the clearance between screw and barrel, which entrains air in pellets and reduces pellet density. Extruder operators compensate by slowing production. These drawbacks prompted Solvay Advanced Polymers LLC in Augusta, Ga., to study barrel wear in a disciplined fashion over an eight-year period. Solvay, which compounds some highly abrasive materials like 50% glass-filled Amodel PPA, compared barrel wear of nitrided steel, D2 tool steel, CPM 10V powder-metallurgy alloy from Crucible Service Centers, Camillus, N.Y., and WPR-29 brazed tungsten carbide alloy from Conforma Clad Inc., New Albany, Ind. Solvay studied the degree of wear of each barrel material in four positions within the segmented extruder barrel: melt sections 1 and 2, melt section 3, mixing section, and glass-addition/ cooling section. Solvay tested some extruders with the same wear-resistant metal in all four barrel sections and other extruders with hard metal only in the glass-addition section. Screws were pulled and wear checked on a routine basis. Conforma Clad's WPR 29 showed the least wear in all barrel sections, but results were most dramatic in the glass-addition section. (CPM 10V showed less wear than nitriding or D2 steel, but not close to WPR29, so it wasn't tested in the first three barrel sections.) Ultimately, Solvay converted all four barrel sections to WPR 29. Its engineers report four times longer barrel life and annual savings per line of about $200,000.
Conforma Clad, Inc.
501 Park East Blvd. New Albany, IN 47150
Phone (812) 948-2118 Fax (812) 944-325