Designing a high-saving, low-impact future
The work cycle
The range of die-casting machines for flawless results.
In the traditional die-casting machine, pressure is generated by an asynchronous motor – vane pump unit with two stages: one stage low pressure-high flow and one stage high pressure-low flow.
Up to 40 bar, both stages go in-line: when this threshold is exceeded, the high flow/low pressure is diverted directly and regularly to discharge (=Drain). Pressure control is achieved by means of shut-off valves which discharge the hydraulic fluid once the set pressure has been reached. When the machine is switched on but at standstill, i.e. during workpiece cooling time and mould lubrication cycles, but also during tooling phases, both flows are generated, not utilised and sent to drain. As a result, the motor draws current from the line continuously throughout the entire moulding cycle.
The solution of applying an inverter to the motor power supply, which reduces its speed when no line pressure is needed, results in modest energy savings, in the region of 25% on average. However, without any positive effect on the general operation of the machine; the hydraulic circuit remains the standard one. The Green Line machine is equipped with a driver-controlled, variable-speed servomotor connected to an internal gear pump with constant displacement. The closed-loop controlled system produces the oil pressure only at the times and in the quantity actually needed and nothing is wasted. The control driver allows the speed and pressure to be adjusted according to the instantaneous requirements of the current production process, with very high energy savings.
At rest, the servomotor maintains a low rotational speed (40÷50 rpm) and consequently limited energy absorption.
The new machine is fast and prompt in exploiting the available resources only and exclusively when strictly necessary.
At the same time, the use of a gear pump increases performance and reduces noise.
The advantage of the gear pump, compared to the vane pump, is that it has an almost constant flow rate when pressure varies, and speed and pressure proportionality are no longer necessary: the simplification of the hydraulic circuit guarantees a reduction in performance losses and a reduction in maintenance requirements.
Advantages of the system:
- Energy savings of up to 80%
- Reduced heating of hydraulic fluid
- Increased opening and closing speed
- Simplified hydraulic circuit
- Reduced maintenance costs and time
- Low noise levels
- No electrical disturbances on the power supply line
- Closed-loop controlled machine movements