Analysis of New, Energy-Efficient Hydraulic Unit for Machine Tools

In machine tools, hydraulic units are one of the main consumers of energy. Hydraulically driven functionalities of machine tools include tool clamping, tool change, work piece clamping or palette change operating. For these functions, two pressure circuits (60 bar and 200 bar) are necessary. This paper introduces a novel, energy-efficient hydraulic unit that combines a variable displacement pump with a variable speed controlled drive and hydraulic booster. The result is a lower overall energy consumption and decreased operating temperatures of the hydraulic unit. Hydraulic fluids contain up to 85% mineral oil. This paper also introduces a mineral oil-free, water-based hydraulic fluid, which will be replacing a conventional mineral oil-based hydraulic fluid (ISO-VG 46) within the novel energy-efficient hydraulic unit. The effects on the unit's performance (operating temperature, pressure, flow rate, power consumption, efficiency) will be evaluated.