In the field of machining difficult-to-cut materials, the high-pressure coolant supply represents a promising technology for increasing productivity and process stability. The distinctive characteristic is the targeted supply of the coolant at elevated pressure (> 80 bar) into the wedge between the chip bottom and the tool rake face. In the industrial application, the high-pressure coolant supply is mainly used in turning of difficult-to-cut materials under roughing conditions. Despite the technological advantages, the application is prevented in turning operations under finishing conditions as the coolant jet force accelerates the broken chips to high velocities, which then collide with the workpiece surface. The high-dynamic impact of the chips on the surface significantly affects the surface quality and may reduce the lifetime of the final component. Hence, the technological and scientific motivation of the thesis was to analyse the underlying mechanisms for the occurrence of surface anomalies.

In a first step, a literature research of theories and hypothesis with regard to the working principle and the acting mechanisms of high-pressure coolant supply was conducted. The analysis of the scientific literature showed that a widespread use (especially in finishing applications) is currently hindered due to the lack of knowledge concerning the influence of the high-pressure coolant supply on the surface quality. Initially, relevant process parameters were identified in a screening approach. Then, the cause-and-effect relationships between the relevant process parameters and the occurrence of surface anomalies were investigated. Based on the approach of ‘process signature‘ according to Brinksmeier [BRIN11] an explanation model was proposed which contained the cause-and-effect relationships between the relevant process parameters and the surface anomalies. Subsequently, a consideration of the energy balance showed that different regions of surface anomalies exist depending on the process parameters. Additionally, an overview of different regions for each type of surface anomaly was derived and possibilities for anomaly-free machining with high-pressure coolant supply were shown. Finally, an innovative appraoch of pulsating high-pressure coolant supply was presented in order to prevent the surface anomaly occurrence.