The need to match global production costs is one priority for diecasters; the requirement to control and reduce their environmental impact is another one, and the two are not always compatible. That is the premise for Colosio Srl as it introduces its new Green Line energy-efficient diecasting machine.
In traditional diecasting machines hydraulic pressure is generated by a pump, usually a double-stage vane pump coupled with a motor. The pump delivers a low-pressure/high flow-rate stage and a high-pressure/low flow-rate stage, and upon reaching approximately 40 bar, the low-pressure stage oil flow is discharged. Moreover, when the machine is turned on but not operating, both oil flows are generated, not used, and therefore directed to discharge. This consumes energy unnecessarily.
By contrast, the Green Line machine is equipped with a variable- speed synchronous motor, controlled by an inverter, and with an internal gear pump with fixed displacement.
The motor transmits torque to a single-stage pump (one that generates variable pressure and oil flows, as necessary.) Different pressure and oil flow values are obtained by varying the motor speed, with an integrated rotational encoder for regulation. A sensor monitors pressure in the circuit and sets the increase or reduction of speed, as required.
In the starting phase, the servomotor starts the internal gear pump, building up pressure in the circuit. Because the oil-flow rate is fixed, the motor is able to maintain line pressure at a preset value (140 bar) even with a lower speed. Once the actuator starts to operate, a reduction of the pressure is detected and the system controls increase the speed of the pump to reinstate the line pressure. A controlling inverter regulates the speed and the pressure as needed. In stand-by phase, the servomotor maintains a low rate (40-50 rpm) of speed, therefore limiting energy consumption. In the operating phase, the rotational speed increases and consequently the energy consumption rises. Therefore, according to Colosio, the new machine has energy available for optimal performance, but only when necessary.
The advantage of the internal gear pump, versus a vane pump, is in having a practically stable oil-flow rate when pressure varies. Energy consumption is discontinuous, and only when the working cycle requires it, according to the machine developer. The new system also makes it possible to reduce the noise level at average running rate; and it achieves a significant reduction in fluid thermal transfer, reducing the need for fluid cooling.