FEATURE LINEAR MOTION
EXAMINING THE benefits of electric motion
With the wealth of linear motion solutions available today, it can be quite confounding to select a specific motion technology that meets performance requirements while satisfying budget and reliability issues, as well as total cost of ownership (TCO) considerations. Jon Howard, managing director of Heason Technology, looks into the benefits of electric actuator technology
W
hen selecting a linear motion solution, some engineers are drawn
to pneumatic cylinder solutions over electric motor driven alternatives – in the mid-range, for example, for position accuracy and precision, where simple and repetitive end-to-end motion is required. Pneumatic cylinders are characterised
by their simple operation with high force and high speeds. They have low unit cost and relatively simple set-up but, conversely, are inflexible when regular machine changeover is required. Furthermore, pneumatic solutions are generally less efficient than electric motors and the overhead costs of compressors and air-supply maintenance and so on can considerably push costs up. Where only end-to-end motion is
required, it is possible to over specify precision if choosing electric motor solutions - which usually means increased unit costs. There are, however, many good reasons why electric actuators can provide an improved and overall lower cost solution. One recent development in electric actuator technology is the PC series, developed by Thomson and available from Heason. The ball screw driven rod-type actuator not only features high precision linear positioning capability but also offers the highest power density of any actuator in its class. It is designed for continuous duty use with higher efficiency, higher overall performance, and reliability with less maintenance when compared to traditional pneumatic cylinders. Furthermore, Thomson has estimated that, in many applications, when replacing pneumatic cylinders with the PC-series users can gain per-axis energy savings which exceed and pay back the cost of the new actuator in only one year. A comparison (see image, right)
22 JUNE 2014 | DESIGN SOLUTIONS
between a typical pneumatic system and a PC-series equivalent illustrates reduced machine volume with fewer components, less cabling and interfacing, and a generally neater installation which is easier to maintain and work around. Furthermore, the benefits in the flexibility offered by an electrically controlled system with its inherent full positioning capability far outweigh the end-to-end capability of the pneumatic system. This means that even for end-to-end
use, product changeover or small positional adjustments to fine tune performance are easily carried out by changing end-point positions in the control program or through an HMI - rather than needing to physically adjust the end-stops and settings for the air-supplied system. In addition, overall
downtime is reduced to a fraction and maintenance is much less of a requirement. All these factors contribute to TCO.
ACTUATORS The PC-series actuators are available with square sectional sizes of 34, 45 and 55mm with stroke lengths up to 1200mm. A range of ball screw leads for each actuator frame size (typically 3, 4, 5, 10 and 20mm) allow speeds up to 1.6m/sec with thrust force to 6000N. The PC-series utilises Thomson’s
RediMount motor mechanical interfacing system which is compatible with more than 600 pre-engineered motor configurations. This permits a very flexible choice of motor types to be selected to match the application. Stepper motors can provide basic
A comparison between a typical pneumatic system and a PC-series equivalent illustrates reduced machine volume with fewer components, less cabling and interfacing, and a neater installation
low-cost open loop positioning or users can select brushed or brushless servomotors that offer varying degrees of performance with quiet and very smooth operation. A choice of direct and pulley offset mounting is also available. The mechanical interfaces and adapters for the PC-series conform to ISO 15552, making machine upgrade straightforward. The IP65 rated actuator has a smooth housing with a stainless steel extension tube and rod adapter which suits frequent wash-down requirements that are found in food packaging and high hygiene applications. Furthermore, its durable construction and high side load capability combine to withstand the rigours of harsh environments found in some industrial applications. Its attractive design, however, equally suits use on medical and laboratory equipment where the actuator may be ‘on show’. Applications that can benefit from
the PC-series could include form, fill and seal, food produce grading and carton/container converting. Processes used in all these areas include rapid end-to-end movements running at continuous production rates and usually need to cater for a range of different sized products. Electric motion provides the advantage
of rapid machine adjustment and also offers higher positional precision and much improved repeatability for more consistent product quality. Machines employing electric motion have much more predictable life between services for less maintenance cost, and are smaller – requiring less real estate which is often at a premium on the production floor.
Heason Technology T: 01403 792300
www.heason.com Enter 212
/ DESIGNSOLUTIONS
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