Page 14 - Industrial Technology March 2020 issue

DESIGN ENGINEERING

awakens

BALLSCREWS AND LEADSCREWS

A NEW GENERATION OF ELECTROMECHANICAL ACTUATORS IS OFFERING A VIABLE ALTERNATIVE TO
HYDRAULIC CYLINDERS IN A HOST OF DEMANDING APPLICATIONS. OLAF DE BAKKER, UK COUNTRY
MANAGER FOR EWELLIX DISCUSSES THE PROS AND CONS AND DISPELS SOME MYTH
or generations, when engineers safety and environmental benefits too. easier to program complex movements, or to transmission pipes and further losses within
wanted to produce large forces or Electromechanical systems also offer build machines that adapt quickly to the actuator. Overall, a hydraulic system is
move heavy loads their first choice significant performance advantages. They different process requirements. likely to deliver only around 44% of its input
Fwould be hydraulic actuation. can operate at a wider range of speed and Against this compelling list of power to the load. Electromechanical
Today, however, hydraulic systems have a power and offer a higher level of positional advantages, electromechanical devices have systems, by contrast, lose energy only due to
powerful rival in the linear motion world: the accuracy. Electromechanical systems go on one apparent flaw: cost. On a per-actuator the limits of motor efficiency and via friction
electromechanical actuator. These actuators working to precise tolerances, and because basis, the initial purchase price of electric in the gearbox and actuator components. An
replace hydraulic systems with a precision their moving parts are based on well- machines is certainly higher than their electromechanical actuator will typically
ball or roller screw, driven by a locally understood rolling element bearing hydraulic counterparts. Over the full lifecycle transfer 80% of its input power to the load.
mounted electric motor and gearbox. technology, it is possible to predict their of a machine, however, electromechanical Moreover, while hydraulic pumps must run
In many applications, electromechanical operating lifetimes under a given set of actuators offer sources of savings that far continually in most applications to ensure
systems provide a host of advantages over operating conditions. outweigh their higher initial cost. Those adequate response from the machine, the
their hydraulic counterparts. They are Furthermore, with no need for separate savings arise from six principal factors. power consumption of electromechanical
smaller and lighter, and since the motor control valves and associated hardware, 1. Energy efficiency: Hydraulic systems actuators is zero when they are not being
powering the actuator is connected directly, electromechanical actuators are easier to suffer multiple sources of energy loss from used. In many applications, an
electromechanical systems do away with integrate into a machine’s electronic control the initial conversion of electrical power into electromechanical actuator may only
bulky pumps, accumulators, oil tanks and system. Together with their fast response, motion to drive the hydraulic pump, losses consume its peak power for a tiny fraction of
pipework. The absence of pressurised oil has accuracy and repeatability, that makes it within the pump itself, fluid friction in the machine’s operating time. Overall, this