Precision surface finish of the mold steel PDS5 using an innovative ball burnishing tool embedded with a load cell

A load-cell-embedded burnishing tool has been newly developed and integrated with a machining center, to improve the surface roughness of the PDS5 plastic injection mold steel. Either the rolling-contact type or the sliding-contact type was possible for the developed ball burnishing tool. The characteristic curves of burnishing force vs. surface roughness for the PDS5 plastic injection mold steel using the developed burnishing tool for both the rolling-contact type and the sliding-contact type, have been investigated and constructed, based on the test results. The optimal plane surface burnishing force for the PDS5 plastic injection mold steel was about 420 N for the rolling-contact type and about 470 N for the sliding-contact type, based on the results of experiments. A force compensation strategy that results in the constant optimal normal force for burnishing an inclined surface or a curved surface, has also been proposed to improve the surface roughness of the test objects in this study. The surface roughness of a fine milled inclined surface of 60 degrees can be improved from Ra 3.0 μm on average to Ra 0.08 μm (Rmax 0.79 μm) on average using force compensation, whereas the surface roughness was Ra 0.35 μm (Rmax 4.56 μm) on average with no force compensation.