Hard-wired connections for controls and I/O devices take more time to design, install, modify, and troubleshoot compared to using a device network. Switching to a networked design saved Shuttleworth Inc., an international conveyor and product handling equipment manufacturer, up to 8% in building and assembly.

Based in Huntington, IN, Shuttleworth recently designed a conveyor system more than 50-m long for a Midwest book manufacturer. The conveyor—designed as a high-speed sorting system for conveying and sorting thousands of books—moves over 190 books per minute.

Initial conveyor system layout included a loading stage, a main lane, and 16 branch lanes. Main feeder lanes on the conveyor converge at a designated point, and books are moved onto one main line. Here, barcode readers process the books' barcode labels and sort them among 16 branch lanes. Throughout the conveying system, multiple safety devices, such as emergency stop buttons and safety modules, are mounted to protect workers from injury.

As the book manufacturer's conveying system continued to grow in length and complexity during design, so did the number of I/O devices. When the number of I/O nodes surpassed 40, Shuttleworth decided to reconsider its current I/O control system, which used discrete wires fed through conduit to connect I/O devices. This led to a high volume of wires leading from each device to the main control cabinet and a significant amount of labor to install and feed wires to and from the control cabinet.

To stay competitive on such large systems design, Shuttleworth needed to reduce its overall system price and the amount of labor. The network had to be user-friendly, enabling the book manufacturer to easily maintain the system after installation.

To achieve these goals, Greg Stroud, Shuttleworth's engineering controls manager, began looking for an I/O system with plug-and-play versatility that could be modified without re-wiring the entire system if a change was required. To further reduce labor time and cost, Stroud also began researching networks that directly integrated safety circuits. Actuator Sensor-interface (AS-i) networking and Safety at Work systems complement each other to provide what Stroud sought.

Sensor and controls manufacturer ifm efector (a member of the consortium of suppliers that represent AS-i and Safety at Work product lines) was contracted by Stroud to apply the digital industrial control networks.

AS-i's flexible topology (the network's plug-and-play wiring supports all topologies, including tree, ring, star, and trunk-and-drop lines) allows the conveyor's master I/O module to be located in the PLC rack and treated as a simple I/O card, requiring minimal setup. Node programming is accomplished with programming tools used by Shuttleworth assembly personnel.

An added bonus in the conveyor system design is that the networks used do not require a junction box and terminal blocks. Fewer terminal blocks means less chance for wires to become loose, creating a more robust system. The Safety at Work system can be wired as multiple independent networks—important for the book conveyor system, which required five separate safety networks that could be shut down in sections instead of shutting down the system.

For Shuttleworth, engineering time has dropped considerably. It estimates 6-8% savings on the building and assembly of a single conveying system using the AS-i and Safety at Work networking systems. With its conveying systems running between $10,000 and $1,000,000, it's deemed worthwhile return on investment. The company has shipped and installed conveyors using the AS-i and Safety at Work systems for customers located in Mexico and Canada.

Lizanne Dathe is with ifm efector.

For more information, go to www.ifmefector.com or www.shuttleworth.com.