What type of device is essential for controlling the motion of a press during operations?

The essential device for controlling the motion of a press during operations is the overrun switch. This switch plays a critical role in ensuring that the press stops promptly and safely at the end of its stroke, thereby preventing unintended motion or continuation of the operation when it is not safe to do so. It acts as a safety measure by monitoring the position of the ram and can cut power to the press if it detects that the ram has traveled beyond its intended path or has not returned to a safe position.

In a machine like a press, which can pose serious hazards due to the high forces involved, implementing this type of control device is crucial for operator safety. It enables the immediate response needed in emergency situations and helps enforce safe operational protocols. By ensuring that the machine stops where it should, the overrun switch contributes to preventing accidents and injuries.

Other devices mentioned, while useful in various contexts, do not primarily serve this specific purpose of controlling motion during the operations of a press.