A free-abrasive machining approach to dressing of resin-bonded CBN grinding Wheels

Abstract

There are increasing demands placed on manufacturing engineers to improve quality and reduce total cost in their grinding operations. Grinding using CBN (Cubic Boron Nitride) wheels has been well documented in reducing total grinding costs (wheel plus labour plus overhead) on tool and die steels with Rc hardness greater than 50 and nickel- and cobalt-based superalloys with HRc hardness greater than 35. Resin-bonded CBN wheels are commonly used in CBN grinding due to their advantages in high speed grinding. However, dressing of resin-bonded CBN wheels is usually a difficulty. In this paper, a free-abrasive machining approach to dressing of CBN grinding wheels is presented. The basis of this method is to indent and drive free abrasive grains on the wheel surface to excavate the binder material between the CBN grains and uncoat the exposed portion of the grains. It is shown that by using the present dressing method CBN wheels can be dressed precisely and efficiently as expected. Experimental results are presented to show the advantages of the present dressing method over other dressing methods in the dressed wheel topography and grinding performance such as the wheel wear, grinding forces, ground workpiece surface roughness and thermal damage. The main parameters in the present dressing method are also considered. It is shown that the wheel topography can be controlled with the average size of the free-abrasive grains used for dressing. There is an optimum value in the grain size, from which the dressed wheel grinds at the lowest forces and highest G ratio. It is also shown that the pressure applied on the dressing plate has a saturation point at which the highest dressing efficiency, and optimum wheel topography and grinding performance can be achieved.