The Process Environment
An overhead monorail system transports car body carriers around a loop that travels through the 100-meter- long paint-shop building.
At the paint-shop loading station at one end of the process line, car bodies are loaded onto these mobile carriers, lifted eight meters off the floor, and attached to an overhead monorail system. The carriers run above a process line with 14 sequential stations. At each station, the carriers stop to allow two on-board hoists to lower the car bodies into a chemical immersion bath. When the process is completed at one station, the hoists lift the car body and the carrier moves along the monorail to the next station in the chain, as soon as it's empty. After the last process station, the car bodies are unloaded from the carriers at the other side of the building, 120 meters from where they began.
The Problem – Obsolete Mobile Connectivity
Each mobile overhead carrier contains an on-board Rockwell Automation SLC5/04 controller to operate the on-board hoists. A single, stationary master controller located near the loading station, manages the carrier controllers. The master issues commands via Allen-Bradley Data Highway Plus (DH+) serial protocol through a conductor rail system that connects it to the carrier controllers.
The DH+ protocol is slower than newer industrial protocols and is difficult to transmit wirelessly. Ford recognized that to increase communication speed and bandwidth they would need to use a new protocol. And, the original network design did not require or include peer-to-peer communication between carrier controllers. Ford determined that adding peer-to-peer communication capability could also help increase production.
The sliding-contact conductor rail system that carried DH+ messages came with its own set of problems. The sliding-contact system required significant maintenance to operate at peak efficiency. But even at peak efficiency, when network bandwidth utilization approached maximum capacity, high transmission error rates plagued this hardware-based rubbing connector system. Low capacity and high error rates created another problem. Even though the paint-shop process line had 14 stations, the conductor rail system had enough bandwidth for data from only 13 carriers at a time, which was restricting paint-shop throughput.
The Goal – Increase Production Capacity with Minimal Modifications
Plant engineers wanted to retain the advantages of having mobile, on-board controllers for each carrier. They wanted to eliminate the communication bottleneck imposed by the older serial protocol. They wanted to eliminate the maintenance headaches and bandwidth limitations of the conductor rail network. They not only wanted to be able to use all 14 stations simultaneously, but also wanted to add from four to six new carriers to cope with increased production demands. So, they began rethinking their network strategy.
"We had to find a better communication technology," explains Mike Dean, from DACS.
The Solution – Marrying Old and New Technologies
Working closely with Dacs Inc. engineering service, and Routeca, their local distributor, Ford elected to migrate to the faster, more robust, EtherNet/IP communication network in order to increase their bandwidth capabilities. But, the SLC5/04 processors mounted in the mobile carrier cabinets had no Ethernet ports. Ford did not want to replace all the mobile SLC5/04s with SLC5/05 Ethernet-capable processors, so they installed a Rockwell Automation DH+ to EtherNet/IP gateway (1761-NET-ENI) in each controller cabinet. This enabled the stationary master processor to receive process data from the mobile processors via EtherNet/IP. The existing master SLC5/04 was replaced with a SLC5/05, giving the master controller sufficient Ethernet connectivity bandwidth to handle the large volume of data from the mobile controllers.
The sliding contact network system was not well-suited for Ethernet communication and too unreliable and costly to maintain. Eliminating the outdated sliding contact system and replacing it with a modern wireless system seemed like an obvious and necessary choice. The mobile carriers and the stationary master controller could then communicate using EtherNet/IP protocol through a high-speed, high-volume wireless network solution. But wireless networks can have their own set of limitations. Radio waves reflect off metal objects and bounce in all directions, creating a potential problem known as radio multipath interference.
"Some engineers were doubtful regarding the wireless choice," says Peter Davies, Senior Automation Engineer, European Paint Engineering, Ford Motor Company. "We are not in a soft and quiet office area. We are in heavy industry. And we have moving metal everywhere."
The paint shop has metal walls and a metal roof. The carriers are massive steel objects, as are the car bodies they carry. These constantly moving metal masses result in an ever-changing radio frequency environment, increasing opportunities for radio interference to interrupt or corrupt data flow. But RadioLinx industrial radios use highly effective filtering algorithms and allow emitted power adjustment. Both of these features help overcome multipath interference problems. Plus, ProSoft Technology's expert advice regarding proper antenna selection and placement was a major factor contributing to the application's overall success.
"We already had experience with ProSoft Technology and their RadioLinx solutions," adds Mike Dean. "Our head office in the UK talked to Routeco, and they came back with the proper options."
"We saved at least 2-3 days of engineering work while designing the network," remembers Mike Dean. "And of course, we saved on installation time, having less hardware to handle, manipulate, and install in the field. In fact, installation and validation of the network were very quick. When adopting a new technology, the learning curve typically runs through one or two projects. But, with RadioLinx and with support from ProSoft Technology, our learning process was very short."
The Results - DRAMATIC
Ford Motor Company experienced an increase in production capacity of more than 53 percent.
The RadioLinx wireless EtherNet/IP network solution provided all the speed and bandwidth Ford engineers needed to achieve their design goals. Wireless networking brought the transmission speed and reliability that were missing with the old conductor-rail, sliding-contact system. The wireless solution was easy to implement and much easier to maintain, requiring less downtime. And the number of carriers that could simultaneously be in use in the paint-shop loop increased from 13 with the old network to 20 with the new network.
DACS is the one-stop solution to problems encountered by customers operating automated processes. The company is fully self-sufficient in all aspects of design, engineering, and manufacturing. Their experienced work force can interpret requirements and, using state of the art technology, can turn these specifications into hardware and software realities at the right price. Each department is structured to bring relevant experience and expertise to every level of project involvement. DACS offers Total Control for companies operating automated processes; its expertise has been utilized by a large number of companies trading in a wide diversity of markets.
Routeco is an independent privately-owned company. The company was formed in 1978 and has successfully established itself as one of the UK`s leading distributors of industrial automation and control products. Over an impressive period of sustained and continuous growth, Routeco has secured a nationwide network of sales locations employing over 200 personnel. The company has expanded by focusing on providing customers with the very best choice of products from leading manufacturers from around the world, packaged together with a range of value-added services. Read more at: www.routeco.com.
About Rockwell Automation
Rockwell Automation®, Inc. (NYSE: ROK) is a leading global provider of industrial automation power, control, and information solutions that help manufacturers achieve a competitive advantage for their businesses. The company brings together leading global brands in industrial automation that includes Allen-Bradley® controls and services, and Rockwell Software factory management software. Headquartered in Milwaukee, Wis., the company employs about 20,000 people serving customers in more than 80 countries. Read more at: www.rockwellautomation.com
About ProSoft Technology
ProSoft Technology® designs industrial communication solutions that connect automation products seamlessly. ProSoft Technology is a highly-diversified, customer-intimate, global organization with a focus on quality and ease-of-use. ProSoft Technology products — including in-chassis communication modules for PLC/PAC controllers, standalone protocol gateways, and a wide range of robust, field-proven wireless solutions — are found in applications spanning the industrial marketplace. www.prosoft-technology.com