Safety devices on CNC machining centers are designed to prevent the machine operator´s health from being damaged, e.g. by collisions with movable machine parts or by contact with tool during processing. It shall also be avoided that parts that might fly around after a tool breakage or the failure of workpiece clamping systems hit the operator.
This is achieved with the help of active and passive safety devices.
Active safety devices
Through immediately turning of the machine (emergency stop) a health impairment of the operator shall be prevented, as soon as he reaches a potentially dangerous area. Active safety devices are often used in areas where it is very difficult to work with passive devices. This particularly means the area where the machine is fed and unloaded. Usually, such devices are deactivated when the machine is in rest. Then, the operator can for example set up the machine, put on workpieces or enter the cordoned-off area behind the machine. In most cases, the monitored areas have to be left before a program can be started.
Versions of active safety devices:
Passive safety devices
They basically prevent access of the operator to potentially dangerous areas of the machine. Passive safety devices are used in areas, where the operator usually does not have to be present, therefore, primarily behind the machine. Mostly it is fences which are high enough to prevent from climbing them without gadgets. To allow access to these areas, nevertheless, usually active safety devices are combined. Often, this is an access door which is equipped with a safety switch. Passive safety devices are rarely seen in areas that the operator has to enter for feeding and unloading the machine. Today, fences which rise up when the program starts are rather uncommon. A more common concept is machines with a complete housing around them. These machines have movable tables, which are moved out of the housing for feeding and unloading and which are secured by automatically closing doors during processing.
Protection from flying parts, e.g. after tool breakage or failure of workpiece clamping systems, is reached with passive safety devices only. Optimal protection is reached by a closed cabin around the machine. However, since this does not allow efficient working for most of the machine concepts, often coverings of the aggregates support and lamella protections are used.
Safety devices for other machine types