Nematron Pointe Controller - Manual (Page 74)

Chapter 4: System Design and Installation Pointe Controller User Guide
72
Orderly System Shutdown
The first level of protection can be provided with the Pointe Controller program
by identifying machine problems. Analyze your application and identify any
shutdown sequences that must be performed. Typical problems are jammed or
missing parts, empty bins, etc. that do not pose a risk of personal injury or
equipment damage.
WARNING : The control program must not be the only form of protection for any
problems that may result in a risk of personal injury or equipment damage.
System Power Disconnect
By using electromechanical devices, such as master control relays and/or limit
switches, you can prevent accidental equipment startup. When installed properly,
these devices will prevent any machine operations from occurring.
For example, if the machine has a jammed part, the Pointe Controller program
can turn off the saw blade and retract the arbor. However, since the operator
must open the guard to remove the part, you must include a bypass switch to
disconnect all system power any time the guard is opened.
The operator must also have a quick method of manually disconnecting all system
power. This is accomplished with a mechanical device clearly labeled as an
Emergency Stop switch.
After an emergency shutdown or any other type of power interruption, there
may be requirements that must be met before the Pointe Controller program can
be restarted. For example, there may be specific register values that must be
established (or maintained from the state prior to the shutdown) before
operations can resume. In this case, you may want to use retentive memory
locations, or include constants in the control program to ensure a known starting
point.