An investigation into the challenges of the point grinding machining process

Point grinding is an abrasive machining process that utilises miniature single layer superabrasive tools to remove material. The use of such small diameter tools offers advantages in the manufacturing of small or difficult to access complex 3D geometries, however, in their current state, these tools suffer from several critical challenges preventing their successful implementation. An investigation into the use of a typical commercially available point grinding tool for machining of hardened steel components has been carried out, with the aim of identifying the critical process challenges. The requirement for high rotational speeds, high tool deflection, variation in grit protrusion heights and bond layer thickness, accelerated tool wear, increased sensitivity to runout, zero cutting speed at tooltip and high tool loading have been identified as the main issues affecting the point grinding process. It is crucial that these challenges are correctly understood to facilitate future tool development

Evolution of electroplated cBN tool surface texture parameters during point grinding

Point grinding is an abrasive machining process that utilises small diameter superabrasive single-layer grinding tools for accurate machining of complex 3D geometries. Due to the small nature of these tools, high wear rates and uneven wear around the tool circumference present a challenge for their successful application for finish machining of metallic components. It is, therefore, essential to monitor the surface condition of the point grinding tools, to ensure their safe and reliable operation. In this investigation, the 3D topography evolution of single-layer B126 cBN point grinding tools was characterised using focus-variation imaging. Given the wealth of information obtained using this method, a decision-matrix methodology was used to identify the most important parameters for monitoring the wear condition of the point grinding tools. Grinding trials were also performed with fixed cutting parameters and varied cutting durations up to 520mm3 of material removed to assess the evolution of the point grinding tool surfaces over time as a result of wear during grinding of hardened D2 tool steel. The best criteria for the characterisation of the surface texture of electroplated cBN point grinding tool surfaces were identified to be the average surface height (Sa), skewness (Ssk), root mean square gradient (Sdq), reduced peak height (Spk), peak material volume (Vmp) and developed interfacial area ratio (Sdr). These parameters performed best for direct measurement of point grinding tool surfaces, paving the way for the application of the imaging technique under manufacturing conditions as an on-machine monitoring method for performance assessment