To complete the preparation of the samples after cutting and mounting, it is necessary to dress/to grind and polish them, or even super-polish them. A metallographic polisher meets this need.
For dressing, abrasive discs with increasingly fine grain sizes are most often used, from P80 to P1200, or even P2400 and P4000 for certain rather ductile materials, and then for finishing, woven polishing cloths and felts, which are loaded with diamond suspensions, most often from 9µ to 1µ.
Superfinishing with alumina or oxides is also possible, with products with submicron grain sizes such as 0.3 or 0.05µ.
Metallographic polishing machines therefore allow the use of all these products.
Metallographic polishers exist in several standard diameters namely 200mm, 250mm and 300mm. Other diameters may exist such as Ø230mm, 350mm and 400mm.
Most often they have a variable speed platen allowing the speed of the platen to be adapted to the support then used. For dressing, a speed of around 300rpm and for polishing slower speeds of around 150rpm.
Metallographic polishing machines are available in manual and automatic. In manual, it is the user who holds the sample by hand and applies it to the various supports. Only one sample can be produced at a time therefore. Automatic polishers have a polishing head on which several samples to be treated can be inserted at the same time. In addition, it allows a regular process independent of the user and therefore better repeatability.
Depending on the materials to be processed, different processes are required. On modern metallographic polishing machines it is possible to adapt and memorize all the parameters such as the speed of rotation of the plates and the polishing head, the pressure force on the sample, the polishing time, the dosage of the polishing products. Modern metallographic polishing machines almost all have a touch screen control panel allowing control of all functions.