In manufacturing, bottlenecks in the production process decrease efficiency and ultimately cost money. A large U.S. manufacturer of cast steel and aluminum automotive wheels was experiencing a bottleneck at the de-flashing operation. In this highly automated operation, robots pick up freshly cast wheels and load them into a machining center where the flashing from the casting process is removed. Once the machining process is completed, the robot removes the wheel and places it on the exit conveyer.
The pneumatically-operated doors on the machining center were causing a bottleneck because they opened and closed slowly, meaning the robot had to wait for the doors to open. The door speed could be increased by increasing the air pressure, but that resulted in them slamming, which caused damage to the doors.
To combat this, a closed-loop servo-pneumatic positioning system was selected consisting of a Balluff Micropulse PF linear position transducer and a servo-pneumatic proportional control system from Enfield Technologies. The Micropulse PF transducer provides precise pneumatic cylinder position to the Enfield controller, which in turn controls the air flow to the cylinder, allowing for rapid, yet smooth, door opening and closing.
This precise absolute linear position feedback was provided from an absolute analog output signal and does not require re-homing. And even in this high-cycle application, non-contact magnetostrictive technology ensures reliable wear-free operation. Unlike linear potentiometers, which can degrade over time, the non-contact technology in the PF transducer means performance is consistent for many repeated cycles.
With its low profile form factor and high degree of compatibility with many piston-mounted magnets, the Micropulse PF provides a highly flexible, low-cost solution. It is resistant to shock, vibration and electrical interference and is designed for stroke lengths from 1 to 300 in.
The closed-loop system allows for easy PLC adjustment of door speed as process requirements change. In addition, the precise position control allows the door open and close time to be reduced by 50%, which eliminates that wasted robot wait time. Finally, the entire system was implemented with only simple mechanical adaption—no large-scale retrofit was required.
Filed Under: Fluid Power World Magazine Articles, Pneumatic Tips