Light Curtains for Press Brake Safety
Light curtains can be highly effective if used properly. They allow multiple operators access to the press and prevent unauthorized personnel from injuring themselves. They also make it possible to use a foot switch instead of a two hand push button station.
Many light curtains have a floating beam option, individual or multiple infrared beams may be broken by the part being formed. Some light curtains allow up to eight inches of beams to be floated. Floating beams can be extremely dangerous if used improperly. Just consider a press with a three inch stroke and a light curtain that allows you to float up to eight inches of beams. We do NOT recommend floating beams!
Channel Select or Canceling:
Beam canceling is an option on some light curtains. Canceling beams allows you to blank out or ignore a given number of the beams. It is a very useful option if used properly and safely. For instance, if you have support arms mounted to the front of the press, canceling the beams that are obstructed by the support arms allows you to operate the press while still protecting the die opening. Misuse of this option is extremely dangerous and should be supervisor controlled. Blanking beans to allow the part being formed to be ignored by the light curtain should never be used. The gap in the light curtain array of beams would allow the operator to inadvertently penetrate the danger zone.
Programmable Channel Select:
Some light curtains can be programmed to selectively cancel a given number of beams during the forming operation. For instance, a box shape is being formed. On the first stroke the light curtains are programmed to ignore only one beam. A four inch high ninety degree bend is made. The part is rotated ninety degrees. Now the side of the part is obstructing four inches of the light curtain. For the remaining strokes the light curtains must be programmed to ignore four inches of the light curtain. Four inches of canceled beams is extremely dangerous.
OSHA and ANSI Requirements for Use of Light Curtains on Press Brakes
- The machine must be able to stop the movement of the ram anywhere in the stroke.
- The stopping time of the ram must be known.
- The stopping time of the ram must be monitored for deviation in stopping time on each stroke.
- The minimum distance the light curtains can be located to the pinch point must be known.
- The light curtains must be control reliable.
- The machine stop circuit with which the light curtains are interfaced, must be control reliable.
- The light curtains must be self checking for proper operation on each stroke.
- There should be no easy way to disable the safety system without special tools.
- If the safety system is disabled there should be a clear indication that it is disabled.
- The operator and setup person should be properly trained in the operation of the safety system.