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Automating Manufacturing Systems - Process Control and ...

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plc sfc - 20.5<br />

press will then retract the ram until the top limit switch is contacted, <strong>and</strong> the ram will be<br />

stopped. A stop button can stop the press only when it is advancing. (Note: normal designs<br />

require that stops work all the time.) When the press is stopped a reset button must be<br />

pushed before the automatic button can be pushed again. After step 6 the press will wait<br />

until the part is not present before waiting for the next part. Without this logic the press<br />

would cycle continuously.<br />

7<br />

reset<br />

button<br />

automatic<br />

button<br />

1<br />

1<br />

6<br />

2 power on<br />

light on<br />

part not<br />

detected<br />

part detect<br />

2<br />

3 advance on<br />

part hold on<br />

4<br />

5<br />

stop<br />

button<br />

light off<br />

advance off<br />

power off<br />

3<br />

5<br />

bottom<br />

limit<br />

4 advance off<br />

retract on<br />

top<br />

limit<br />

6 retract off<br />

part hold off<br />

Figure 20.4<br />

SFC for <strong>Control</strong>ling a Stamping Press

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