Market demand for pneumatic systems that offer superior positioning capabilities has greatly increased in recent years. In many applications, concern over fluid leaks and cost have led engineers to reevaluate their use of hydraulic and electric positioning systems. The remaining challenge, therefore, was to develop an accurate positioning alternative that eliminated these concerns.
The ability of pneumatic systems to repeatably position a load within a consistent and finite range of measurement has always been dependent on several variables. For example, cylinder orientation, bore size, stroke length, load mass, velocity, pressure, flow rate, valve size, and system response time affect the ability of pneumatic systems to respond accurately. One must also consider that in most applications, the cylinder never reaches steady state conditions. To address all of these factors, Hoerbiger-Origa developed the Servotec(TM) servopneumatic positioning system. This system integrates an Origa SystemPlus(TM) (OSP) rodless cylinder, two-way servo valves, a path measurement system, and control module. Resulting performance affords repeatability of 0.004 inch at displacement speeds up to 90 inches/sec. Stroke lengths up to 158 inches are available.
The control module is supplied by 220V ac at 50 Hz and is available as either a desktop or compact version. The latter can be easily mounted to a wall or rail (35 mm DIN). For user convenience, the controller utilizes either a PLC or PC connection.
Available for 25 and 32 mm bore sizes for Servotec applications, the OSP cylinder provides "double dovetail" channels on its exterior to permit the integration of other system components, or to directly interface with common structural framework.
The rodless cylinder's position is controlled by two-way servo valves (24V dc ±10%) which act upon position data furnished to the controller by the Sensoflex(TM) displacement measuring system. The SFA system is based on a conductive plastic potentiometer. In addition to low energy consumption, the system is insensitive to electrical or magnetic interference.
Together, the components continually monitor the exact position of the cylinder piston. Continual feedback of piston position provides a perpetual comparison of the actual or true value in the position control monitoring of preprogrammed values. Any deviation from preprogrammed values is quickly controlled by the servo valves. As a result of this electronic regulation, the cylinder piston is positioned in a manner that affords a high level of measurement tolerance. Further, in the event of a power failure, the software evaluates the actuator position following the restoration of power so that the operating cycle continues as if there had been no interruption. The resulting performance lends itself to a variety of applications.
The accuracy and repeatability of the Servotec system facilitates application in a variety of industries that would not have previously considered pneumatic positioning. Industries such as automotive equipment and handle tool manufacturing, where the environment, system cost, and positioning accuracy are tantamount, are successfully applying servopneumatics where previously only hydraulic or electric solutions were available.
Hoerbiger-Origa recognizes that increased accuracy, repeatability, and responsiveness to market demands are necessary to ensure the success of pneumatics in the future. Toward this end, we have developed a variety of positioning alternatives that incorporate hybrid designs of pneumatic and electric technologies that provide varying degrees of accuracy. It is in this manner that we believe we will be able to address the specific demands of those market segments that we serve.