Nanoparticle lubricant additives applied in a CNC lathe ball screw component for improving the quality of machined workpieces: A case study

A lathe ball screw is a mechanical actuator that translates rotational motion to linear motion. These machine elements are lubricated to reduce friction and wear since they can affect dimensions of the machined workpiece, measured by C _p and C _pk process capability indicators, and the number of equipment shutdowns. In this work, different nanoparticles (NPs) were added to a commercial lubricant for machine tool slideways with the purpose of reducing coefficient of friction (COF) and wear. NPs of SiO ₂, CaCO ₃ and montmorillonite clay (MMT) were added to the lubricant in concentrations on 0.01 and 0.05 wt%. Four ball tests performed under scuffing conditions showed that the best concentration was 0.01 wt% for all NPs, with improvements in load-carrying capacity of 13–15%. Higher concentrations resulted in agglomeration and these large NP clusters were not able to infiltrate the contact area to reduce friction and wear. Block-on-ring tests showed that 0.01 wt% MMT reduced wear and COF by 83% and 81%, respectively. Finally, machining tests were performed in a CNC lathe with the 0.01 wt% MMT nanolubricant for the ball screw component. Improvement was measured by keeping track of the dispersion of the workpiece dimensions, the process capability indicators C _p and C _pk and the number of equipment shutdowns for adjustments. The addition of MMT NPs to the lubricant improved C _p and C _pk by 34% and 52%, indicating a lower variation on the work piece measurements. Furthermore, equipment shutdowns were reduced by up to 50%, improving the process efficiency and lowering manufacturing costs.