Deformation analysis and improvement method of the Ni-P mold core in the injection molding process

Abstract

Electroless nickel phosphide (abbreviated as Ni-P) commonly serves as the plating material of the mold core for injecting aspheric plastic lenses used in imaging optics. The deformation of Ni-P mold core is accomplished in the injection molding through the influences of pressure and temperature. To verify whether the deformed Ni-P mold core can meet the accuracy requirements of the aspheric mold core in imaging optics, a deformation analysis of the Ni-P mold core with injection experiments was performed. It is shown that the P-V error of the Ni-P mold core is found to increase by approximately 1.6 μm. The mold core exhibits a deformation trend of contraction in the center and expansion at the edges. Heat treatment, which can transform Ni–P from amorphous into crystalline, is adopted to reduce its deformation. Experimental results indicate that the deformation trend of heat-treated crystallized Ni-P mold core is alleviated, and its form accuracy is reduced by 1.1642 μm (PV). Such reduced deformation in this innovation makes it able to meet the accuracy requirements of aspheric mold core for imaging optics, and the life of mold core is greatly prolonged using the proposed method.