Reduce energy consumption during idle or dwell times.
One of the single largest energy consumption reduction factors of electrical power over fluid powered actuator systems is the dwell time savings.
The energy required from a fluid powered system is determined by the requirements of the power unit to deliver the required pressure and flow to its actuators, at any given moment, and when the whole system is in activation or in a state of readiness.
A hydraulic-powered control system consists of the actuators connected via hydraulic tubing, hoses, pumps and a fluid reservoir. Typically an electric motor is used to power a pump that operates at a constant speed. This pump is often a fixed volume positive displacement unit that requires the same amount of flow throughout all operating conditions. Any surplus flow not required at a given point would be recycled back to the reservoir. These systems are designed to avoid pressure drops and so continue to consume energy even when the duty cycle does not require any actuator movement or load-bearing.
Michael Socks states that in operations such as injection moulding, these dwell times can account for up to 40% to 50% of the entire cycle time.
In his paper regarding injection moulding machines, Socks identifies four main areas of efficiency gains possible for electrical actuation over hydraulic.
- Reduced energy consumption during idle operation
- Elimination of internal leakage losses within hydraulic components
- Elimination of frictional losses within hydraulic lines
- Reduced cooling requirements
All of these are worth further investigation for the majority of applications currently using hydraulics, but in Socks' testing, the dwell time alone yielded energy savings of 74% when switching to electrical actuation. And this is from 2005!
Read the full report here - The Promise of All-Electric Injection Molding Machines: A Promise Kept?
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