Investigation of Surface Integrity and Wheel Wear in Grinding Complex Freeform Surfaces Using a Single-Layer Electroplated CBN Wheel

This study investigates the factors governing the distribution of surface roughness in the finish grinding of complex freeform bone plates using a single-layer electroplated CBN ball end wheel on Ti6Al4V alloy. Eight independent workpieces were machined under fixed process parameters, four in the as-machined condition and four heat treated to 41 HRC, with each group ground sequentially by a dedicated wheel. Roughness was measured at twenty-one locations with three repeated measurements per location, and radial wheel wear was monitored across eight cross sections throughout the grinding sequence, yielding 504 observations. The spatial distribution of roughness proved reproducible, with intraclass correlation coefficients of 0.852 and 0.768 for the two groups, and was preserved across both material conditions. Wheel wear exhibited a two-stage behaviour and reduced roughness by 5.53 nm per micrometre of cumulative wear, consistent with the levelling of grain protrusion heights during run in. Heat treatment reduced mean roughness by 91.8 nm, corresponding to 24.0 percent, while regions of larger radius of curvature exhibited roughness higher by up to 77.5 nm. The measured roughness exceeded the geometric scallop limit by a factor of 16 to 103, indicating that the governing mechanism resides in the abrasive grit regime rather than in toolpath kinematics within the range of conditions examined.