Abstract:
Heavy machinery can cause great damage to the human who gets too close to the processing stage. For example: a finger can be cut off in a metal punch press; a hand can be cut off in an automated assembly line; holes can be drilled into the human body by industrial grade drill presses, milling machines and lathes. By modern safety laws, all heavy machines must have safeguards to prevent these types of accidents: cages or barriers to prevent the human’s entrance to the processing stage or automatic disconnects to shut down the machine when a human’s presence is sensed as being too close. But all too often these safeguards are sabotaged by the very workers they are meant to protect. Without safeguards, the worker can work faster, but the absence of safeguards eventually causes an accident. We study several cases and show that better engineering of safeguards is the only way to prevent these types of accidents. Engineering students who study these cases learn that not only is it necessary to know how to design a PLC or industrial control to safeguard the worker, but also they must design them in such a way as to thwart friendly sabotage. Improved design techniques include: better interlocks for shut-down controls and more rigid specifications for self-regulated safeguards.
