Lubrication of Radial Loaded Tapered Roller Bearings Under High Rotational Speeds

Abstract

To improve the manufacturing accuracy in the machining process, the stiffness of the machine tool spindle must be increased. One approach is to replace the conventionally used spindle bearings by tapered roller bearings to achieve a higher stiffness and load carrying capacity. However, the speed capability of this bearing type is limited, though can be enhanced by sufficient lubrication, especially in the critically loaded rib-roller-contact. The objective of this paper is to validate the lubricant influence on the speed capability of radially loaded tapered roller bearings. In various speed step runs, the operating behavior of the bearings under oil-air and grease lubrication was evaluated based on the outer ring temperature and the vibration level in the test rig. With oil-air lubrication, a speed parameter up to 900,000 mm/min could be achieved, whereas with grease lubrication, a speed parameter of 540,000 mm/min could be reached. In comparison, the setup with spindle bearings can achieve the highest investigated speed parameter of 900,000 mm/min with both grease and oil-air lubrication. For grease lubricated ball bearings, significantly higher temperature fluctuations are present with variation of the radial load. In the case of oil-air lubrication, the steady-state temperature improved with increasing oil viscosity.

Stiffness increase in main spindles by using tapered roller bearings for aluminum cutting tests

“…During the tests, the spindles are cyclically loaded and unloaded with a maximum force of 3.8 kN for constant rotational speeds of 2000 rpm, 4000 rpm, and 6000 rpm. Since an additional lubrication of the TRB on the side of the rib-roller contact proved to be more beneficial, this was also implemented in the investigated TRB spindle [9]. The spindle was lubricated according to these findings with a lubrication quantity of 480 µl/h per nozzle, one on the loading side and one on the motor side (see also oil injection in Fig.…”

“…However, only low speed parameters up to 0.24 × 10 6 mm/min were investigated with the bearing and the comparison to a standard bearing showed no significant friction reduction. Current works demonstrated, that spindle-relevant speed parameters of 0.9 × 10 6 mm/min already can be achieved with standard TRBs with suitably high lubrication [9,10]. Therefore, the focus of this paper is to characterise the stiffness increase of TRBs compared to SBs in main spindles.…”

Erhöhte Prozessstabilität durch Kegelrollenlager/Increased process stability due to tapered roller bearings

“…Aktuelle Ergebnisse zeigen, dass bereits mit Standardkegelrollenlagern mit ausreichender Schmierstoffeinspritzung spindelrelevante Drehzahlkennwerte von knapp 1*10 6 mm/min erreicht werden können [8]. Deshalb wurde eine fremdgetriebene Hauptspindel in einer 4-Achs-Bearbeitungsmaschine mit einem elastisch vorgespannten KR entwickelt und in Schnittversuchen an einem Aluminiumblock getestet [9]. Die KR-Spindel zeigte signifikant reduzierte Verlagerungswerte in radialer Richtung während der Schnittversuche.…”