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

Abstract

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 Cp and Cpk 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 SiO2, CaCO3 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 Cp and Cpk and the number of equipment shutdowns for adjustments. The addition of MMT NPs to the lubricant improved Cp and Cpk 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.