Metal coating the helical screw of an injection moulding or extrusion device - with a carbon di:oxide laser as heating source and controlled parameters for the powdered metal feed and movement of screw past the laser unit

摘要

Method of metal coating a helical screw of an injection moulding or extrusion device consists of using a high energy CO2 laser (5) as heat source which can be adjusted to give a predetermined energy density and width of coating via a focussing unit. The feeding speed of the metal coating in the form of a powder and the movement of the screw beneath the laser beam are controlled as are the degree of overlap of each coating and the pressure and flow of a protective gas atmosphere fed with the metal powder. ADVANTAGE - The energy used is partly for melting the surface of the screw and partly for melting the powder so that a metallic bond is produced by instanteous coagulation. This bond ensures that the coating does not suffer any future stripping or flating. The heat used is controlled so that the screw is not excessively deformed and the coating thickness can be precisely controlled. This all leads to improved wear and corrosion resistance with reduced production costs.