Diamond roll dressing was introduced in the 1960s and has been growing in usage until it now represents the commonest dressing method for the majority of profiled and flat grinding applications, and virtually all vitrified CBN applications. Nevertheless, it often remains just an option on new grinders still designed primarily for stationary dressers or a later requirement for retrofitting to existing grinders. Conversion of machines to rotary dressing may require machine modifications including mounting plates, guarding changes, or even additional axes of motion. These axes may be used as controlled infeed motion for the dressing operation or merely to move in to a fixed stop and then after dressing retract in order to clear the dresser from the grind area. Some examples of both dressing spindles and the accompanying infeed systems are illustrated in the proceeding pages [courtesy of Wheel Dressing (Saint-Gobain Abrasives)].
15.17.2 DFW-ACI Air-Driven Spindle
Figure 15.36 shows an impellor rotor-driven spindle with ABEC 7 twin ball bearings for radial stiffness and ABEC 7 thrust bearing for axial stiffness. Note, a muffler is required to reduce noise level with air operation. The unit requires dry shop air lubricated and filtered to 5 pm. It was originally designed for Heald internal grinders and is most effective on alox wheels but has been used successfully on small vitrified CBN internal wheels. Since air is compressible, a larger cylinder is required to achieve the same drive stiffness as with a hydraulic cylinder.
15.17.3 ECI Hydraulic Spindle
Figure 15.37 shows a cantilevered hydraulic powered dresser with three pressure-lubricated sleeve bearings for radial stiffness and damping and two ABEC 7 thrust bearings for axial stiffness; used
|
|
FIGURE 15.37 EC1 hydraulic spindle.
with up to 3 diameter by 1 wide rolls typically for traverse dress operations or narrow plunge forms. This hydraulically driven spindle is rated for up to 7,000 rpm although generally runs at 4,000 rpm.