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Challenge:
A particle board manufacturer needed an inexpensive way to automatically adjust the height of a scrubbing deck, based on the thickness of the material passing underneath. The rotating wire brushes on the scrub deck were used to smooth the surface of the wood. The company received several quotes for expensive position following servo controls which were capable of much greater accuracy than they needed (0.025" inches). They also wanted the solution to take full advantage of the PLC being used to control the machine.
Height Control
| Requirements |
Load 1000 lbs, vertical |
| Speed |
0.3 inches/sec |
| Duty Cycle |
30% |
| Repeatability |
±0.025 inches |
| Control |
Analog position
command from PLC |
| Interface |
4-20 mA signal |
Solution:
| Control |
Servo |
| Actuator |
Electric cylinder |
Brush height control was easily realized using a servo control which accepts a 4-20 mA analog (position) output from the PLC. The PLC takes the height measurement from an ultrasonic sensor, and provides a corresponding position signal to the controller. In-position outputs sent back to the PLC when motion is complete.
Application Solutions
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