Reports conducted by the Association for Home Appliance Manufacturers indicate that major North American whiteware manufacturers contributed to more than 16 million domestic shipments of washing machines and refrigerators in 2002. But few of us realize the complexity of manufacturing the automated production systems for the appliance industry. While these giants of the industry compete to bring affordable luxury in the home, one of their suppliers competes by migration to communication networks that will demonstrate solid performance throughout the life cycle of automated production systems. Scott Technology Limited in New Zealand specializes in the design and manufacture of large-scale automated manufacturing systems for the major domestic appliance industries of the world. Customers include the names of the largest global whiteware manufacturers in the appliance industry.
One of Contemporary Controls distributors, Mantis Systems Ltd in New Zealand, supplied the Ethernet switches to Scott Technology to be used in the form line of a machine for a whiteware manufacturer. John Kilkelly, Senior Controls Engineer of Scott Technology says the form line decoils the sheet metal from a coil and takes the metal sheets and forms, bends, presses and welds the metal into a component for a whiteware product.
"I'll cite an example," says Kilkelly. "The line makes the outer wrap for the oven cavity. The customer supplies a front frame and back panel (workers piece options in this panel, i.e. for a light). Then the line assembles these parts by spot welding (17 sec cycle time)."
What fueled the type of communication network for Scott Technology's system was their customer requirement to not use traditional fieldbuses requiring software configuration. Scott Technology desired to use a bus system that would dominate the industry in the future. Their knowledge of Ethernet/IP supported such an opinion and this technology's capabilities-from reducing downtime to no hidden start-up costs-met all their expectations, especially ease of use in commissioning.
"My electricians' found it easy to terminate. We purchased all the correct tools to do the job properly and a fluke test instrument to test the cables when completed." Kilkelly notes that with Ethernet/IP there is improved flexibility. "We can add or remove devices on the system quickly and easily without using additional wiring."
Scott Technology chose Contemporary Controls Ethernet switches because of their confidence in Mantis Systems. Kilkelly says Mantis Systems has strong knowledge of Rockwell Automation products and an understanding of the workings of Scott Technology. This was Scott's first Ethernet/IP line so they were concerned about potential problems, but the company was confident that Mantis Systems would provide the support required to keep their system operating continuously without interruption. As a distributor for Contemporary Controls, Mantis Systems provides responsive phone support and technical advice on how best to configure an Industrial Ethernet/IP application using the company's CTRLink® products. Vendors of office-grade equipment seldom are knowledgeable of the unique requirements of the controls industry. As an example of Contemporary Controls commitment to educating the industry, Contemporary Controls founded the virtual Industrial Ethernet University (IEU).
Contemporary Controls switches are marketed under the CTRLink trade name- from repeating hubs to managed switching hubs to media converters-designed to be cost-effective and to improve network performance. Both eight-port and sixteen-port switches were employed in the process and their reliability became even more valuable as workers eyed the line for any jams or other problems that would cause product loss or inconsistent product quality during the production cycle.
Based on the application, the switches had to meet certain guidelines. "Fast installation, with no additional labor says Kilkelly. "We panel mounted the switches using the mounting brackets so it would be easy to replace a switch if it failed. However, not one switch has failed to function properly." The manager of Mantis Systems explains further.
Tony Baldock, Manager of Mantis Systems, says an earlier line produced by Scotts had 1 Ethernet switch from a competitor on the HMI PC which kept losing messages. There have been no problems with the multiple CTRLink switches on this line.
The industrial switches proved their ruggedness because they were able to withstand exposure to this environment, i.e. electronic interference. We were able to use shielded cable that provided noise immunity. We were able to reduce the number of switches used in this application compared to ones used from competitors. By using the EISC16-100T, we had more ports per switch. The temperature range had to be between 0° to +60°C, just like industrial controllers such as PLCs. Ethernet equipment must have equal or better temperature ratings as the equipment to which it is connected. Further, the switches had to offer a 24 Volt DC power supply because the control system I/O voltage is 24 Volt DC and a data rate of 100 Mbps because 100 Mbps is more efficient than 10 Mbps to get messages to and from the I/O."
The EIS8-100T switch provides eight 10/100 Mbps copper ports utilizing RJ-45 connectors. An MTBF of more than 40 years gives this switch an added networking advantage. The EISC16-100T offers 16 twisted-pair ports. This configurable switch provides capabilities beyond those found in standard Plug and Play switches. The EISC16-100T has advanced features such as Port VLAN, trunking, Quality of Service (QoS) and a programmable fault relay that can be connected to a supervisory system. "In this application, the VLAN feature has been utilized to minimize the effects of multi-cast messages on all ports," says Baldock. By definition, VLAN allows for the physical network to be configured as multiple virtual local area networks; thereby, limiting the broadcast/multicast domains and improving network performance.
The deployment of the Ethernet/IP communication network was the ideal solution for this form line. By linking all components together including an additional Welding Rockwell Automation SLC® Controller via Ethernet, Scott Technology was able to simplify much of the cabling plus to improve diagnostic capability.
The form line- 25 meters in length-is housed inside the building and all electronic components are mounted in control panels adjacent to the line. The 51 Ethernet devices are attached to CAT5 cabling, with various lengths from 5 to 30 meters. The line uses a ControlLogix processor Controller to manage positioning and control affecting the form of the end product and a Welding SLC® Controller to manage component welding control functions. The backbone of the line is the Allen-Bradley PLC chassis with individual slot modules for 1 processor, 4 EtherNet/IP modules and 1 motion control module.
Kilkelly says that the configuration is relatively simple. Each EtherNet/IP module connects to one EISC16-100T switch which connects to one EIS8-100T switch. There are 10 switches per each line on two lines. Seventeen I/O blocks connect to the EtherNet/IP module via one EISC16-100T switch and one EIS8-100T switch. The 10 VFDs (Variable Speed Drives) are attached via a EISC16-100T switch. The welder controller and seven electronic operator terminals are linked via a EISC16-100T switch and six laptop programming ports (positioned around the machine) are connected via a EIS8-100T switch. Shielded RJ-45 connectors on each end of the cables connect to the switches and the rest of the components. Industrial RJ-45bulkhead receptacles (female) are mounted on the operator panels for connection of a laptop to the control system for fault-finding, etc.
The PC is located at the end of the line as the finished product emerges. The PC has RSView from Rockwell Automation for data collection. Scott Technology can examine how well a component on the system is performing in order to repair possible problems before they cause any difficulty. For instance, Kilkelly says batch data is given, i.e. number produced and number scraped. Also, downtime monitoring is determined. This means shift start and end times-a fault code will be logged for any reason of machine stoppage.
The line is fully automated with safety-switched access doors along both sides. Operator panels are strategically located along both sides to permit monitoring and control as well as manual intervention, i.e. parts addition where required. Baldock says most automatic operations are able to be performed manually from the operator terminals. Machine diagnostics and fault conditions are provided by the operator terminals.
Baldock concludes that the integration of the control system equipment with Contemporary Controls' CTRLink switches has been fantastic. "With modern industrial manufacturing, the operator expects to have instant results on his display terminal," says Baldock. "The fast I/O update times of today's control systems mean there can be minimal delay from a change-of-state on the machine to providing the operator with that information. As this was the first application for Scott Technology with all I/O blocks, VSDs and Operator Panels on Ethernet/IP and each machine was to have 57 Ethernet nodes, we decided early-on to set-up a bench simulation at the Scott facility in Christchurch, New Zealand with a section of the control system hardware to see how the data throughput compared with our calculations. The test results confirmed our findings. Ethernet's strong support from the industry secured Scott Technology's decision to move ahead with the system."