To achieve the quality and productivity requirements for most precision grinding operations, it is necessary that the grinding wheel is trued and dressed prior to grinding and periodically during the grinding operation. The truing process is initially performed to correct for any wheel runout, create the required profile on the wheel and condition the grinding wheel face.
During the grinding operation it is usually necessary to dress the wheel periodically to re-establish the wheel profile and/or recondition the wheel face. Wheel conditioning, typically involves the sharpening and opening up of the wheel face, while also removing dull abrasives, excessive bond and workpiece material (loading). A sharp and open wheel face will allow maximum possible material-removal rates by minimizing the high grinding power and forces associated with a dull and closed wheel. On the other hand, there may be occasions when a closed and dull wheel face is required, such as to improve the surface finish. This process of preparing of the wheel face to the desired condition (roughness) is achieved during the dressing process and fine-tuned by modifying the dressing parameters, including the dressing speed ratio.
Truing and dressing a grinding wheel can be carried out using either stationary tools or rotary tools. As the names suggest, the rotary dressing tool rotates and the stationary tools do not. The main reason for selecting a rotary tool – also known as dressing roll – over a stationary tool is that it will greatly improve the dressing tool life and form holding capabilities. This is largely due to the greater number of active diamonds that are around the periphery of the roll. Although tool life is usually the chief driving force being selecting a rotary dresser over a stationary device, an additional benefit to rotating the dresser is the fact that the relative speed between the wheel and roll can be adjusted to influence grinding process. The dress ratio is the dress roll velocity divided by the grinding wheel velocity and can be either in a positive or a negative direction. This paper discusses the different rotary dressing methods and will cover in more detail how the dress speed ratio can be used to manage the wheel face condition and ultimately manage the grinding process including, workpiece quality and process productivity.
Read more: Optimizing grinding and dressing with ‘dressing speed ratio’ parameter