Studies on Eco-Friendly Grinding with an Extremely Small Amount of Coolant – Applicability of Contact-Type Flexible Brush-Nozzle –

Abstract

This study considers an innovative coolant nozzle that enables a remarkable reduction in grinding fluid consumption in cylindrical plunge grinding of chromium molybdenum steel (ISO 34CrMo4 / JIS SCM435) using a vitrified-bonded cubic boron nitride (CBN) wheel. This coolant nozzle has a simple structure consisting of ordinary nylon or polypropylene fiber brushes and an acrylic resin oil pool. This flexible brush-nozzle is suitably placed in contact with the wheel surface, and the grinding fluid is supplied along the brush to the wheel surface to form a fluid film to the wheel surface, while simultaneously scraping the “air belt.” Thus, the grinding fluid adheres to the whole wheel surface by the “Coandă effect,” and grinding fluid consumption is reduced to 0.5 L/min or less without causing any thermal damage to the ground surface. The cooling effect of this coolant nozzle is examined mainly by a grinding temperature measurement by means of a fiber-coupled two-color pyrometer. The nylon fiber brush is more effective than the polypropylene brush because of its high elasticity and good water absorption rate, which is related to the wettability. Even with such an extremely small amount of grinding fluid, the grinding force, surface roughness, and grinding temperature are nearly the same as those in the case of the conventional wet grinding.