A theoretical model to predict the anisotropic characteristics in grinding of diamond conical indenter

Abstract

Mechanical grinding of a high-precision diamond conical indenter is difficult due to the strong grinding removal rate anisotropy. In the existing literature, theoretical models have been established to predict the strength anisotropy of diamond on the (100), (110) and (111) planes, which provide a theoretical basis for the fabrication of pyramid diamond indenters, such as Berkovich, Vickers or Knoop indenters. However, investigations on the anisotropic characteristics in processing of diamond curved surface are rarely carried out. To solve the anisotropy problem in grinding of diamond conical indenter, this work contributes a theoretical model to predict the anisotropic characteristics in grinding of diamond cone face, and provides an effective method to optimize the grinding direction for enhancing the fabrication precision. Based on a proposed grinding-ability factor model, a general method is developed to analyze the grinding ability along different directions according to the formation process of the cone face. The results suggest that the optimized mechanical grinding direction can be determined by minimizing the standard deviation of the grinding-ability factors of the crystal planes. The proposed method is validated by grinding experiments on indenters, with the <100> or <111> orientation along the indenter axis. The experimental observations confirm that the optimized grinding direction can weaken the pyramid phenomenon, yielding a roundness error of 0.12 μm. In addition, the grinding removal rate-dependent roughness petal phenomenon is suppressed, which considerably enhances the conical surface quality.