Calotte grinder

Small changes often make work more efficient and reduce wait times. Important film architecture parameters such as the film thickness or abrasion resistance have been determined with calotte grinding methods established in research and industry for many years. Now this method has been expanded at Fraunhofer IST: Up to three calotte grindings can be produced simultaneously during a test procedure for the first time, resulting in significant time savings.

The new calotte grinder

Notwithstanding relatively straightforward handling, the process is difficult to automate. Fraunhofer IST has succeeded in designing a more effective test process through a structural modification. With the devices that are commercially available today, only one calotte grinding can be produced at one time with a grinding ball. Now up to three balls do this work simultaneously using the method developed by Fraunhofer IST, with the same precision. This makes three calotte grindings available for evaluation in the shortest possible time.

Film thickness determination

Film thickness determination is based on the optical analysis of the grinding pattern. The adapted preparation of the grinding is therefore of great importance. Under optimum conditions, the relative error of a film thickness measurement is only a few percent. The ratio of the grinding depth to the film thickness is decisive for this purpose. With very thin films (< 5 µm), special attention must be paid to ensuring that the grinding depth is only slightly greater than the film thickness.

Measuring the wear resistance of thin films

The calotte grinding process was subject to continuous further development in recent years. With kinematics optimized for the wear process, it is also possible to determine the abrasion resistance of thin films. A grinding suspension adapted to thin films is essential in addition to the device technology details. The abrasion capacity in the grinding zone can be adjusted with the grit (grain size). Keeping the grinding depth less than the film thickness is important to determine the film wear.


The calotte grinding process is straightforward with proper handling and the result is informative. The process introduced here is of particular interest under the aspect of minimal investment needs. Notwithstanding the very low expenditure of time, the accuracy of the test setup is rather good. This innovation is very well suited for the fast and precise testing of layer thicknesses on multiple specimens.