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Selecting the Right Stop Type



When a die protection sensor detects a problem, sometimes it's necessary to emergency stop the press; sometimes a top stop is required; and other times the stop type might need to change depending on where in the stroke the sensor detects the problem.

You should set any sensor that detects a die-threatening event to emergency stop the press, as long as the sensor detects the problem before the critical angle.  A sensor that detects a non-die threatening event (such as end of coil) can be set to top stop the machine.

You should also set the stop type to top-stop for any sensor that detects a problem that occurs too late in the stroke to stop the machine before the critical angle.   In such cases, it's impossible to stop the press before making a bad hit, and the only thing worse than making a bad hit is making a bad hit and sticking the press on bottom.

But what about events that can occur both before and after the critical angle?   Here's an example:

A Green Constant sensor is set up to monitor misfeed with a ready signal that turns on at 0° and off at 150°.   The long ready signal gives the sensor the ability to detect when the material fails to feed properly, as well as when a strip that feeds initially pulls back during pilot release.   The critical angle for the die is 90°.  

Pie Chart
Timing diagram shows the benefit of SmartPAC's Smart Stop

If the material fails to feed, the problem is detected at top-dead-center (0°) with plenty of time to stop the press before making a bad hit.   In this case, an emergency stop is needed.   However, when the material pulls back, it happens much later in the downstroke - well after the critical angle.   For this fault, a top stop is required.   It would appear that for this sensor, there is no single ideal stop type.

Fortunately, the SmartPAC has a feature called "Smart Stop" that will automatically change the stop type from emergency stop to top stop if it detects a fault between the critical angle and bottom dead center.   To use Smart Stop, you specify the critical angle for each die, and the SmartPAC does the rest.






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