In the case of so-called “milling dressing” or kinematically coupled dressing, a fixed rpm ratio is set between the grinding wheel and a diamond segment or PCD dressing roller [EICH97, MERZ94, SPIE92, WARN88]. For integral rpm ratios, the same areas of dressing roller and grinding wheel are always engaged. When segmented diamond dressing tools are used, geometrically precisely defined surface sections are formed on the grinding wheel. In the case of non-integral ratios, the surface section deviations are phase-delayed. Coupled dressing can also be carried out with statistically distributed diamond coatings. The depth of dressing cut is measured only once for the entire dressing amount, so that all dressing engagements take place in the same cutting edge depth. By stringing together several cycloidal engagement paths, a wave-like profile emerges on the grinding wheel circumference [EICH97, GRUE88, SPIE92]. High demands are placed upon rpm control.
Methods involving Material Removal
For metal-bonded grinding wheels, spark-erosive or electrochemical conditioning methods can be used. These methodological principles are described extensively in “Manufacturing Processes Volume 3”. Depending on the intensity of the spark — erosive or electrochemical material removal effect, these methods can serve either profiling or sharpening purposes [HARB96].
Dressing with spark-erosion is based on discharge processes between the two electrodes — the grinding wheel and the dressing tool — in a nonconductive dielectric. The grinding wheel is polarised as an anode, a numerically controlled wire or a profile block electrode as a cathode. During spark discharge, the bond is removed by means of thermal erosion. The superabrasive grits can be damaged by excessive impulse energies [TOEN75]. Spark-erosive dressing necessitates a high cost in apparatus for the isolation and power transmission on the grinding wheel and has yet to make a mark in industrial praxis [FALK98]. It must also be determined whether the dielectric can be used as a cooling lubricant for grinding or whether two separate fluid cycles are necessary [HARB96].
In the case of electrochemical material removal, the grinding wheel bond is polarized as an anode, confronted with the gap of an electrode and thus dissolved in an electrolyte solution. The gap width must be constantly supervised, since it determines the amount of dressing. The electrolyte solution which is produced presents difficulties in disposal, which is a disadvantage of the method [HARB96].
Hybrid methods such as electrochemical discharge machining (ECDM) can combine the advantages of electro-erosive and electrolytic material removal [SCHO01].
Laser conditioning used a tangentially arranged laser beam for profiling superabrasive grinding wheels [HOFF02, TIMM00]. The energy of the laser beam must be selected such that the cutting tool material is not damaged. All multilayered abrasive coatings can be dressed with this method. However, in the case of vitrified and metallic bonds, unevaporated material can remain on the grinding wheel, which has to be removed [HARB96, TIMM00]. Laser-conditioned grinding wheels exhibit the same process behaviour as those dressed by conventional means [HOFF02].