Experimental Study of the Gaseous Coolants Influence in the Milling of Polytetrafluoroethylene on the Surface Characteristics

The achievement of a desirable surface roughness with an efficient structure is a major challenge in machining of Polytetrafluoroethylene (PTFE) owing to its viscoelastic behavior. The aim of this research is to investigate the effect of gaseous coolants utilization on the roughness and structure of surfaces.  For this purpose, the effect of Argon noble and CO2 effective gases on the machining of PTFE were evaluated, taking into consideration the cutting and feed velocities as input factors. The surface roughness was measured by Ra criterion.  The microscopic structure of surfaces was investigated using optical and scanning electron microscopes. To measure the machining temperature, the operation was recorded by high accurate thermal camera. The results show that the utilization of CO2 due to decreasing local machining temperature to below -40°C can change the cutting behavior of material from viscoelastic to elastoplastic, and reduces the surface roughness up to Ra=0.2 µm. Microscopic studies indicate that the using of CO2 can govern the viscous behavior during cutting which causes the viscous-flowing of material and prevents the generation of surface cracks. CO2 also protects the surface from chemical interactions and creation of functional groups during the machining. Microscopic examination revealed that the use of carbon dioxide gas prevents separated chips from re-adhering to the surface.