Grinding is widely known for its low material removal rates and high surface quality. However, recent developments in production processes for cubic boron nitride (CBN) abrasive grains have led to commercially available grain sizes larger than 300 µm. These superabrasive CBN-grains allow higher material removal rates during grinding of hardened steel components. Currently, these components are pre-machined with turning processes before hardening and finishing the work piece by grinding. However, the turning process can be eliminated by grinding with coarse CBN-grains since higher depths of cut are achievable when machining hardened components. This paper explores the limits of grinding wheels using grains with a size of B602 during soft and hard machining in comparison to conventional B252 grains. It is shown that the use of coarser grains leads to lower process forces, higher (tensile) residual stress and higher surface roughness. Residual stress and surface roughness are of less importance as these grains are to be used mainly in roughing operations with ensuing finishing operations for the required surface properties. Over all investigations, especially in hard machining, neither grain nor tool wear was observed for the B602 grains, whereas the B252 tool was severely clogged during the experiments. Additionally, the grinding force ratio indicates that the coarse grain tools have not yet reached their productivity limit as it increases over all investigated feeds. This indicates improving tool performance with lower amounts of rubbing for increasing feed rate during hard grinding and shows the potential for the industrial use of higher feed rates with larger grains.

Recent developments in the production processes for cubic boron nitride (CBN) abrasive grains have led to commercially available grain sizes larger than lg > 300 µm. These superabrasive grains allow higher material removal rates during grinding of hardened steel components. Currently, these components are pre-machined by turning processes before being hardened and eventually finished by grinding. However, the turning process can be substituted by grinding with coarse CBN-grains since higher depths of cut are achievable when machining hardened components. This paper investigates the process behaviour of vitrified and electroplated grinding wheels with large grain sizes during the machining of hardened steel components. Process forces, wear behaviour and workpiece surface roughness are investigated for three different grain sizes, and the process limits of both bond types are examined. The investigations show that vitrified tools do not fully suit the demands for peel grinding process with high material removal rates since wear by bond breakage occurs. The electroplated tools on the other hand are capable of very high material removal rates. Their wear behaviour is characterized by clogging of the chip space if the process limit is reached. Even so, both tools outperform a standard hard-turning process in terms of process time by 74% and 94% respectively. This process time reduction in combination with the possibility to use the same (machine) tool to machine both soft and hard sections of a workpiece adds flexibility to current process chains.

This study presents original research of the investigation of the coolant supply to the contact area with two different approaches. The cooling and lubrication are key aspects of manufacturing processes such as grinding to achieve a high surface quality at high productivity. The coolant supply to the contact area has a high impact on the performance of the coolant. This paper presents the results from two approaches to tailoring the coolant supply for conventional and high-performance processes. An analytical approach is established to determine the coolant outlet velocity. Afterward, a sensor is developed to measure the coolant velocity at the nozzle. Conclusively, the influence of the coolant velocity on the volume flow through the contact zone is investigated. The results of this study highlight the importance of coolant outlet velocities of at least 60% of the cutting speed. The two approaches outline low impact possibilities to ensure optimal coolant outlet velocities and thus low thermal loads during the grinding process. Article Highlights Analytical approach to calculate outlet velocities for varying noozles in high-performance grinding with cutting speeds of up to 100 m/s Utilization of a high-speed camera to determine the outlet nozzle velocities in a conventional deep grinding process Validation of the impact of the coolant outlet velocity on the volume flow through the contact area by means of a coolant collection box

Die Bearbeitung von PCBN-Wendeschneidplatten mit keramisch gebundenen Schleifscheiben führt zu erhöhtem Schleifscheibenverschleiß. Am IFW Hannover wurden daher metallisch gebundene Werkzeuge entwickelt, um durch ihre mechanischen Eigenschaften eine höhere Schleifgüte zu ermöglichen. Die höhere Festigkeit dieser Bindung erhöht jedoch den Abrichtaufwand. In diesem Beitrag werden Ansätze zum mechanischen Profilieren dieser Schleifscheiben vorgestellt.   The production of PCBN indexable inserts with commonly used vitrified grinding wheels is very wear-intensive. The IFW Hannover therefore developed metal-bonded grinding wheels to enable higher grinding ratios due to the high grain retention forces of metal bonds. However, the higher strength of this type of bond negatively affects the dressing process. This publication presents approaches for mechanical profiling of such grinding wheels.

Eine steigende Nachfrage an komplex geformten Bauteilen fordert neue, produktivere Fertigungsverfahren sowohl für die Luftfahrt wie auch für die Medizintechnik. Die Bahnplanung für diese Bauteile kann durch die gezielte Verwendung von Bearbeitungswinkeln verbessert werden. Bisher ist der Einfluss sich ändernder Winkel während der Bearbeitung auf die Oberflächenqualität des Bauteils jedoch unzureichend untersucht. Dieser Artikel zeigt vorteilhafte Winkelbereiche für zwei beispielhafte Maschinen und Werkzeuge auf.   An increasing demand for complex shaped parts requires new methods for increasing the productivity in machining of those parts. The path planning for free form grinding can be improved by fitting the surface curvature of the workpiece to the shape of engagement of the tool. So far, there has been little investigation concerning the effects of the yaw angle on the surface quality. This paper shows beneficial yaw angles for a set of process parameters on two different machines and tools.