Key polishing machine principle of operation is to try to get the maximum polishing rate, so as to remove the damaged layer produced by grinding. At the same time that the polishing damage layer will not affect the final observed, that will not cause false tissue. The former requirements to ensure high polishing rate to remove grinding damage layer, use coarse abrasive polishing, but damage layer is deep; the latter requires the use of the finest materials, but the polishing rate low, polishing damage layer is shallow.