Mechanical Power Presses and Their Hazards

Although there are three major types of power presses -- mechanical, hydraulic, and pneumatic -- the machinery that accounts for a large number of workplace amputations are mechanical power presses.

In mechanical power presses, tools or dies are mounted on a slide, or ram, which operates in a controlled, reciprocating motion toward and away from the stationary bed or anvil containing the lower die. When the upper and lower dies press together on the workpiece, a re-formed piece is produced. Once the downstroke is completed, the re-formed workpiece is removed either automatically or manually, a new workpiece is fed into the die, and the process is repeated.

Amputations occurring from point of operation hazards are the most common types of injuries associated with mechanical power presses. Inadequate safeguarding allows the operators to inadvertently activate the power press's tripping mechanism while their fingers are in the die (point of operation). For example, amputations can occur when an operator instinctively reaches into the point of operation to adjust a misaligned part or release a jam. Amputations also occur when an operator's normal feeding rhythm is interrupted, resulting in inadvertent placement of the operator's hands in the point of operation. Such injuries typically happen while the operator is riding the foot pedal.