Energy efficient solutions for hydraulic units of machine tools

Abstract

Hydraulic units of machine tools are one of the main consumers of energy. Hydraulic functionalities of machine tools are e.g. the tool change, the work piece clamping, the palette change, the weight compensation of vertical axes or the supply of hydrostatic guidings. This paper describes possibilities to reduce the power consumption of hydraulic units. The power consumption of different hydraulic units is analysed and compared for an exemplary machining centre with regard to its different hydraulic functionalities. The paper observes three hydraulic units, from the perspective of power consumption, in detail. One unit represents state of the art technology and the other two units are prototypic hydraulic units whose power consumption has been optimised. The first prototype includes a booster. The second prototype combines a frequency controlled variable-displacement axial piston pump with different accumulators for different pressure levels. Besides power, pressure, flow rate and temperature are monitored for the different hydraulic units. In addition to that, further interdependencies of the hydraulic units and other ancillary components of the machining centre, e.g. heat transfer to the cooling system are analysed.