A special case of dressing is crushing. The operating principle of crushing is based on the crushing of bond bridge when a certain force level on the grinding wheel coating is exceeded [DENN02]. This is achieved by pressing rollers on the grinding wheel layer without relative velocity (dressing speed ratio qd = 1).
The crushing, effected by steel or carbide rollers, has been long known in thread grinding with conventional wheels [KLOC82]. Fundamentally, ceramic bonds and specially developed brittle metal bonds are suited to crushing. The method can also be employed for cBN and diamond grinding wheels if they exhibit the brittle bonds necessary for the process.
In full crushing, the profile roller and the grinding wheel are aimed towards each other at equal peripheral speeds. The brittle bond bridges break under the pressure that builds up in the contact zone [MEYE81]. The high forces on the grinding wheel cause the shape of the crushing roller to replicate on the grinding wheel as a result of grain splintering and grain and bond breakaway. This method is only used in praxis to a limited extent [KAIS97]. One reason for this is that an unavoidable relative speed between the grinding wheel and the profile roller leads to high wear on the dressing tool and thus to profile loss.
In point crushing, a carbide roller cuts the grinding wheel contour by numerical control. With a regulated dressing roller drive, the relative speed can be set to zero at every point of the grinding wheel profile [DENN02].