Feature Linear motion
Electromechanical benefits L
When specifying a solution for linear motion within a system, many engineers are realising that
electromechanical linear actuation can offer real benefits and resolve many issues. As such, it is becoming the technology of choice across a wide range of applications and industries, saysThomson Linear
inear motion is used to automate processes such as materials handling, the opening of doors, positioning dental chairs or med-
ical operating tables, or controlling position for packaging machines. In fact the technology is used throughout industries ranging from food and bev- erage, pharmaceutical, medical devices and electronics, to plastics, agriculture, construction and aerospace. There are three main methods in
use today: Pneumatic, hydraulic or electromechanical actuation (and linear motors where high dynamic performance and micron precision is required). While pneumatics and hydraulics have historically been the most common, environment, health, safety and increasing pressures to make machines more efficient, mean electromechanical actuation is becom- ing the technology of choice.
Selecting the right technology The choice of technology is driven by application demands. Pneumatic actuation converts energy from compressed air into movement, and is most commonly selected for lighter loads, with fixed and repetitive move- ment between two points. The end points of the stroke when using this technology are often defined by the mechanical limits of the actuator or hard stops on the linear motion path. A relatively low cost solution, this is a good choice for simple applications. If control over the motion profile is required, proportional regulators and valves can be used but this makes the
system complex. Fluctuations in air pressure can also lead to variations in the process performance. Due to the high force provided,
hydraulic actuators are a common choice for larger loads. Suitable for use in extremely harsh environments – including agricultural and construc- tion machinery, performing operations such as moving excavator booms, extending and retracting equipment or tilting loading platforms – hydraulic actuation generates and controls power using pressurised oil. This technology, however, means high maintenance and energy costs, as well as the envi- ronmental impact and health and safety issues related to leaking oil. Electromechanical actuation sys-
tems are driven by an electric motor and provide a relatively simple solu- tion. Although historically seen as a more expensive option, the latest advances make them a viable alterna- tive which offers a rapid return on investment, with benefits including lower maintenance, increased produc- tivity, more accurate position control, reduced energy costs, simpler opera- tion and easier installation. One-piece linear actuators, such
as Thomson’s Electrak series, are designed specifically for rugged and reliable operation in the toughest envi- ronmental conditions. These are also a clean and quiet solution.
Installation Hydraulic and pneumatic systems require fluid compression systems
to operate. Although both
Hydraulic Vs EM actuators diagram
types can hold pressure with- out additional energy being applied, they require the
compressor to be continually running even when the system is idle. Electromechanical devices, however, only use power when the system is operating and moving its load, which can lead to significant energy savings. Hydraulic and pneumatic solu-
tions also require additional systems to deliver the compressed air or fluid for their operation, and these sys- tems need to be connected to every installation. If unavailable or not easily connected to the location where the actuation system is to reside, this can add significant cost to the installation. Furthermore, run- ning the compressed fluid systems can be complex and costly and they can be prone to leakages. Operating independently of other
systems and requiring only electrical energy, electromechanical systems can be installed anywhere in a plant. They can be controlled wirelessly, have few components compared with a hydraulic system, are compact, easy to install, and are reliable. These are also easy to specify and design, with an engineer requiring only values for load measurement, duty cycle and stroke and retraction length to define the required system.
Electrak PPA-DC Performance Pak actuators are rugged, heavy-duty units for mobile applications such as replacing hydraulic lifts
Design Solutions JUNE 2013
Maintenance and productivity Hydraulic systems require regular maintenance to check oil pressure and clean filters. If used in systems which are continuously operating, these checks require machines to be stopped and the oil to be cooled. Electromechanical actuators (such
29
> 31
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52