Presence Sensing Device

Presence Sensing Devices (PSD) are one of the more common safety devices for press brake safety. It is difficult to protect the operator using a metal bending machine such as a press brake. Often the operator must hold the sheet metal work-piece in one place while another portion of the piece is being formed in the die. If a foreign object is detected, the laser, camera, or light curtain technology will immediately retract the die or stop the motion of the ram. PSDs protect the operator and other employees in the area.

One category of presence sensing devices is Photoelectric Sensors. Light Curtains fall into this category. Light curtains use many infrared light beams to form a perimeter around machinery. When two or more consecutively adjacent beams are interrupted, a kill-switch stops the machine until the boundary is reset. Light curtains must be placed in front of the work area. This makes it difficult for press brake operators to work on small parts. One cannot help but disrupt the beam. The operator might "mute" the light curtain in order to get the job done. Certain parts of the beam can be muted. For example, muting the front and rear of the beam allows the middle to offer continued protection for the operator. Additionally, it may be necessary to use auxiliary light beams if the operator will reach between the main light beams and the edge of certain machines.

Electronic Safety Devices use lasers or cameras to sense a foreign object in the vicinity of the press brake. They are less obtrusive than other safety options, which means operators are less opposed to using them.

After some contention by OSHA, an electronic safety device can fall under the PSD umbrella. One such device is the Laser Sentry press brake safety device, designed by Glen Koedding, CEO of Metal Tech Controls Corp, in 2003. The concept was challenged with OSHA by a competitor almost immediately. OSHA responded by issuing a letter of disapproval stating that the Laser Sentry did not meet the “safe distance” rule. The rule states that a presence sensing protective device must be a minimum of 6 inches away from the nearest pinch point. However, after further observation, Laser Sentry was deemed a Presence Sensing Device (PSD) in 2004, when used in conjunction with hydraulic press brakes. Laser Sentry features laser guides that ensure the safety of a press brake operator while employing the precision of lasers directly surrounding the die. OSHA's caveat to its approval of the device was that they be properly installed and inspected. Among other presence sensing devices available, this device can be used as a retrofit to aging machines.

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