Shop floor communication is one of the more critical issues in factory automation. Cable connections between devices have, to date, been the primary vehicle for transferring data between devices. This often requires the development of customized interfaces, and the resulting networks have proven to be costly and inflexible. Shop floor communication has evolved from hard-wired connections to proprietary networks, to non-proprietary networks, with each step representing an improvement in terms of implementation time, cost, maintainability, and flexibility. There remains, however, one important drawback; in order for two devices to communicate, there must be some type of physical connection, whether it be twisted pair, coaxial cable, or fiber optic cable.
The next generation of shop floor communication will overcome the requirement for a physical connection between devices through the use of radio frequency (RF) signals. Although RF is a mature technology, new applications are continually being developed. RF is now being used to assist in the control of traffic, electric power, and water supplies in some municipalities. More recently, manufacturers have begun to apply RF to assist in data collection and inventory tracking.
This paper will describe an on-going, trial application of RF technology on the shop floor. Northern Illinois University's Advanced Manufacturing Laboratory recently acquired two MOSCAD remote terminal units (RTU's) which are being integrated with an existing CIM line. The CIM line is a test-bed facility that consists of several CNC machines, robots, and a MiniCartrac programmable conveyor system. Each MOSCAD RTU combines the capabilities of a programmable logic controller (PLC) with an RF communication system. The RTU's will provide the communication link between the CIM line and a metrology station that includes a coordinate measuring machine (CMM).