Safety Considerations

(For discussion purposes only. Safety is Your responsibility!)

Firstly, it should be clear that the Company which installs and operates any type of Automatic Equipment is entirely responsible for the design and implementation of that equipment. It also falls to the National Health and Safety Executive to ensure that any new or existing equipment does not represent a hazard to the workforce. Safety personnel within the plant will normally carry out a risk assessment and develop a method statement prior to commencing installation work and operation of the equipment.

I have seen various standards in many countries ranging from a simple crash barrier to a fully interlocked enclosure. Standards worldwide are improving but considering the rudimentary beginnings in safety work there were surprisingly low injury rates and no fatalities whatsoever. Obviously robots were treated with a healthy respect.

Today's Industrial Robot is a very sophisticated machine. Constant pressure to increase speed and reduce cycle times has developed fantastic drive technology which can generate astonishing acceleration, high velocities and unexpected trajectories from 6 independent axes. In short, it is never safe to be in close proximity to an industrial robot of any kind when it is powered up and running in auto. It can select alternative sub-routines based on a variety of incoming signals and programmable priorities (you have no idea where it is going next).

The exception to this rule is when teaching locations. It is necessary to get in close and visually confirm that the position is perfect, before recording it. This cannot be avoided so the task must be carried out by fully trained personnel in conjunction with an authority based access system.

The robot should also have a teach restrict facility which, when selected using the gate interlock system, will enable a very slow speed selection for all taught movements. This is the only mode that should be available when operatives are in close proximity to the robot. The Teach Pendant should also have a teach lock facility to prevent manual de-selection of teach mode from the controller.

A typical installation comprising a various items of equipment may look something like this:

• Industrial Robot
• Machine Tool
• Inspection Station
• Input Conveyor
• Output Conveyor

The robot cell would be layed out to enable the robot to access input, output, machine tool and inspection station. The Cell would be enclosed by a 2M high safety fence. Normal construction would comprise fabricated weldmesh panels and a weldmesh access gate. Polycarbonate viewing panels may also be employed. The gate would be locked using a captive key system. When the gate is locked the key is removed and inserted into the system control cabinet, thereby enabling the cell to commence production. The keyswitch would be part of the system safety circuit. A key may also be used to initialise the Teach Restrict mode.

Additional safety products are often used to compliment the access barrier. Where large products have to enter or leave the robot cell, light guards may be used to cover the apertures. Pressure mats may also be used to prevent unauthorised access resulting in injury.