Application principle of an accumulator in hydraulic clamping system of machine tool

1--Motor; 2-- Hydraulic pump；3--Oil filter；4--Check valve；5--Overflow valve；6--Pressure relay；7--Pressure gauge；8--Accumulator；9--Directional valve；10--Hydraulic cylinder

The hydraulic clamping system is widely used in the machine tool industry. It has the advantages of large clamping force, convenient operation, and easy automation with electric appliances.  However, the general clamping system keeps the pump and the motor running for a long time to maintain a constant pressure of the system, which not only wastes valuable energy, increases system heating, but also greatly reduces the life of the hydraulic components.  As a hydraulic auxiliary component, accumulators are more and more widely used in machine tool hydraulic systems with the improvement of manufacturing technology. For this reason, in the hydraulic design of the machine tool, the use of the accumulator for the hydraulic clamping system has received good results. 

As shown in Fig. 1, when the clamping operation is required, the motor 1 is started, the hydraulic pump 2 starts to operate, a part of the pressure oil enters the clamping cylinder 10, and the other part enters the accumulator 8 for storage.  As the pressure increases, when the upper limit of the system use pressure is reached, the pressure relay 6 signals that the motor and the hydraulic pump are stopped by the electrical control, and the pressure of the system is maintained by the accumulator. As the system leaks, when the pressure drops to the lower limit of the pressure relay, the pressure relay sends a signal to start the motor and pump to replenish the oil pressure.  The time from the stop of the hydraulic pump to the restart is determined by the number of clamping cylinders in the system and the leakage of the system. According to experience, if the system leakage control is better, the interval can be 2~3 hours. This greatly reduces the running time of the motor and the pump, reduces the heat generation of the system, and increases the life of each component.