As is well known, the actual objective of the impact tests defined in the standards is to determine the impact resistance of various materials used for guards. Commonly used for this purpose are steel sheets and transparent plastics for the vision panels, the latter being of great importance for the safe use of the machine: The vision panels in machine tools serve two purposes: they allow the machining process to be observed and, in the event of an accident, they protect the operator from ejected tool fragments, for example. Polycarbonate is used as a material for such vision panels because of its excellent impact resistance. However, polycarbonate is subject to aging processes that lead to a reduction in its impact resistance. Cooling lubricants in particular accelerate these aging processes as Uhlmann et al. [1] pointed out in a preliminary study "KSS-PC", but the effect of modified cooling lubricants on polycarbonate sheets in impact tests is not entirely clear due to the relatively short exposure time. Therefore, funding for a comprehensive follow-up project "KSS-PC-Plus" was obtained via the German Machine Tool Builders' Association (VDW) in order to substantiate the statements of the preliminary study within a larger time frame.

The total scatter of the determined impact resistance adds up from numerous individual effects, which can lead to a considerable random measurement error, as described in a separate paper [2]. Only when a model for this measurement error is available can the impact resistance of the polycarbonate sheets under investigation be determined indirectly from the velocity measurements of the projectile with some degree of "accuracy".