Safety - Using Guards And Limits - Quin Q-drive Installation & User Manual

Issue 1.5 Q-Drive Installation Manual
6.

Safety - Using Guards and Limits

All machines should include comprehensive safety features. This is essential both for
normal safety considerations, and to comply with Health and Safety requirements. It
can also prevent any unwanted interference with the machine while it is running.
All moving machinery must be guarded so that it cannot be reached by anybody while
in motion. The guards should be fitted with guard switches or sensors, connected so as
to immediately cut power from the motors when any guard is opened. On some
machines, it may be useful to lock the guards closed by means of a solenoid to prevent
them from being opened while the machine is running. This allows the machine to
detect any attempt to open a guard and shut down the machine cleanly before unlocking
the guard and allowing it to open.
Motors which have constraints or limits on their range of motion should be fitted with
hard wired limit switches. These should cut power from the motors if any motor goes
outside its limits of travel. The machine must also have one or more locking emergency
stop push-button switches, accessible from several positions around the machine.
Anyone operating or working on the machine must be able to instantly stop the machine
at any time by hitting an emergency stop switch.
There are no limit switches available on the Q-Drive but if the machine requires the use
of limit switches then they may be implemented using the digital i/o functions available
on the control system. If the control system is used to provide a limit switch function
then this should be backed up with an mechanical switch which should cut the power
to the Q-Drive.
Guards, emergency stop and limit switches may be connected into the control system
motor control systems, by using the digital input lines. However, the programmable
input functions on the control system should only be used in addition to the
conventional hard wired guard and limit switches, not to replace them. The digital
inputs can be used to trigger a smooth shutdown sequence, or to generate a limit switch
error and shut down immediately. The control system can then remove power from the
motors and drives if required, under software control, by using a digital output line to
switch the motor supply contactors. In all installations the limit switches and guard
switches MUST remove all electrical power from the motors and drives,
independently of any action of the control system. If power is removed from the
control system, then again all power must be removed from the motors. This is easily
done by connecting the on board relay on each axis controller into the drive enable
function, or into the control circuit for the motor and drive main contactors.
Note that in most cases, it is not necessary to remove power from the control system,
only from all the high power equipment. If power to the control system and encoders
can be maintained even when the motors and drives are shut down, then the system does
not lose any position information. This can allow the machine to start up again much
more quickly than if the control system is powered off as well, since the machine does
not need to execute a complete initialisation before it can be restarted.
Copyright © 1996 Quin Systems Ltd. Page 29