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8874

pid loop and press

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Has anyone tried a pid loop and press operation. What I have is a air over oil press cylinder. I have a lvdt monitoring the position of the head and a analog 0 to 10 volt proportional valve. 0v=0 psi and 10v=80 psi. My head starts at 0mm and approaches a distance of 41.5 mm. I am just starting the cycle with the valve output value 32767 max pressure. Every mm of travel I am roughly subtracting 750 from my output value, so the closer I get to the setpoint I ramp down slowing the cylinder to keep from overshooting. I was looking at the pid instruction but I have never set one these up in a plc. If anyone has tried this with this type of operation let me know. Edited by 8874

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No, I haven't. I do quite a few press applications with force-distance monitoring (steel into steel) and generally once the static friction is overcome, we want to maintain velocity (ie kinetic friction) till we hit an adjustable hard stop (when using hydraulics). Or in the case of servo presses with built-in LVDT and load cell we hit the programmed distance (or force) and immediately retract.

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Hi What are you pressing and what pressure due you need to press it? My experience is with High speed piercing and shearing and a PID loop in a PLC certainly would not be fast enough. More information about your application may be useful. Regards Alan Edwards www.wolfautomation.co.uk

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