ABSTRACT
The term "die protection" describes a monitoring system that uses sensors to detect specific events related to material progression through the die. The sensors connect to a control that is wired to the stop circuit(s) of the press. The control receives signals from the sensors, interprets them, and decides if the operation is running normally. If there is a malfunction, the system stops the press. Die protection systems are designed to stop the press before any damage can be done to the die. All die protection systems have the following major components: sensors mounted in and around the die to monitor specific events, a controller to perform logic functions, provide decision-making capability, and interface with the press stop circuits, and a timing device to allow the control to perform logic functions based on the press crankshaft angle. (See Fig. 1.)
Examples of events that die protection systems can monitor include material buckle, end of stock, part ejection, misfeed, and slug ejection. Die protection systems monitor these events in three different ways depending on their frequency. Die protection events can be static, cyclic, or intermittent. A static event is something that should not occur when the press is running normally. Examples of static events include material buckle and end of stock. Cyclic events are functions that should happen every stroke. If a cyclic event fails to occur once per stroke, there is a problem. Part ejection and misfeed are examples of cyclic events.
