Ethernet at the factory-floor level was a hotly debated topic in the late 1990s, but many companies sidestepped arguing in favor of doing. In the process, they are proving that Ethernet can yield financial rewards for manufacturing.
One example is a chemical plant where engineers use high-speed Ethernet with Foundation Fieldbus to provide all the functions required by the project without the cost of additional controllers. A discrete parts manufacturing plant needed to automate online testing and communicate real-time product data. Ethernet comes to the rescue, again. When a parts supplier to Jaguar required the speed and coordination of a, well, Jaguar, an Ethernet vision network helped assure quality and parts coordination with the assembly plant. Retrofitting old die cast machines proved to be a challenge met with Ethernet control networks hosted on programmable logic controllers (PLCs). And, when a heavy vehicle manufacturer wanted to build its “plant of the future,” wireless Ethernet I/O devices saved the day.
A 1940s vintage plant, Merisol’s Greens Bayou cresylic acid production facility, located near Houston, Texas, includes process units that upgrade and refine phenol, cresols and xylenols—products used in the manufacture of resins, solvents, antioxidants, functional fluids, cosmetics, disinfectants, agricultural chemicals and many other chemical intermediates.
Engineers and managers wanted to modernize Merisol’s process automation systems while improving plant-wide data access. Legacy Honeywell TDC 2000 and older Moore distributed control systems (DCSs) were slated for replacement with PLCs, with the goal of an integrated system providing full access to process information and displays from any plant location.
Henry Marks of Henry Marks Associates was hired to provide detailed engineering for the first two phases of the project, and to serve as project manager for the first phase. Marks was product manager for the TDC 2000 DCS at Honeywell when it was developed in the 1970s. He was also product manager for the next two generations of the product line. Marks says he became really interested in Foundation Fieldbus when the wraps came off the Foundation Fieldbus high-speed Ethernet (FF-HSE) protocol at the ISA Show in 1999. He knew that would be the perfect fit for this project.
Marks continues, “Merisol’s Brad Bonnet was the real pusher for the project. A former control engineer, he was now with the information technology operation and provided the needed communications infrastructure. He had already implemented plant-wide Ethernet systems, so I knew as soon as I saw FF-HSE that we could superimpose it on that network, providing a whole new dimension to the architecture.”
The existing TDC 2000 and Moore DCS didn’t talk to anything, according to Marks, so the engineers had already begun implementation of a GE Fanuc PLC in part of the plant. Their intention was to install a control network of FF-HSE so that they could install operator displays in various locations using Wonderware HMI, a human-machine interface system. Marks decided to build upon this architecture to implement an entirely different control scheme.
Rather than buy more PLCs, he decided to accomplish control with intelligent positioners on control valves in the field, leveraging the promised interoperability of built-in Foundation Fieldbus. He explains, “This interoperability is supposed to be the greatest thing, so we did just that—mingling products from Rosemount, Yamatake and several more. Because this was the first implementation of FF-HSE, we were the ones who identified the interoperability that wasn’t all that great and helped correct it. Even though that slowed us down, we still got the project done. FF-HSE plus OPC [Object Linking and Embedding for process control] can communicate with just about anything. One of the first things we did when it was all connected was to expand the Wonderware installation for redundant Microsoft SQL database so that reports were not only meaningful but were available to all who needed the information, while still maintaining the firewall.”
This project required close coordination between Marks and other engineers and Bonnet and the IT department. Was this a culture clash leading to acrimony and delays? Marks replies, “Bonnet had been in charge of control systems, then moved to IT. Plus it wasn’t a big plant so there were no empires involved. Now you have the support of the IT people since with FF-HSE, they don’t have to get on their knees to beg help from control. Although the Fieldbus Foundation started with an independent protocol, it decided to maintain standard high-speed Ethernet media. This simplified the architecture and built support in IT and management.”
Marks states that with the new devices and parameters available, engineers can provide asset management at a new level, allowing them to go from reactive to proactive to predictive maintenance. For example, engineers can determine total travel on a valve and the number of its reversals, so wear and tear can be predicted, allowing a reasoned judgment as to when replacement will be required. “The other thing with having smarts in field devices,” he states, “is that we can go back to single loop integrity with advanced control without having to buy another controller. New control loops can be just added to the network. Previously, a technician could go out to the field, look at the loop controller, and do the tuning. Then with DCSs, troubleshooting went to computer people. With this new concept, we can revert to the integrity of single-loop control with simpler maintenance.”
Ethernet not only provides a foundation for potential revolution in process industries, it has found a home in automated testing as well.
沙赫扎德萨瓦尔,蒙特利尔,魁北克,Canada-based Averna Technologies’ director of industrial and real-time solutions, describes how the system integrator implemented a distributed test automation system at a customer’s discrete manufacturing plant.
“We needed to implement an automated and distributed production control and quality testing system to manage a range of new products assembled and tested at different contract manufacturer sites,” Sarwar states. “We did this by integrating our Proligent production management and testing system, National Instruments’ TestStand and LabView and a Microsoft SQL server database. Test engineers developed test code and deployed it over the Ethernet network to each of the actual test stations hosted in a personal computer. All test results were sent back to a central database for report generation and analysis. We needed to create and maintain the test system, as well as do product routing.”
Part of the information is exchanged with the corporate enterprise resource planning (ERP) and manufacturing execution systems (MES), he notes. This involved interaction with the IT department. “We had to struggle a little with IT, but in the end we all learned to work together. The important thing for automation engineers to remember in this situation is to not underestimate the amount of work it takes to integrate things at the IT level. Not everything is straightforward, and applications like firewalls take a lot of effort,” Sarwar reports. “People are becoming aware of past problems of working with other departments and are preventatively preparing before undertaking projects.”
System architecture consists of a PC containing the applications, database and networking cards connected to remote sensors via RS-232 serial or general purpose instrumentation bus (GPIB). It also connects to the plant information network via Ethernet.
The new system centrally manages product flow, test criteria and results, version- and revision-specific test procedures, and several other operational details, all for a set of distributed product lines located at different and remote contract manufacturer sites. It maintains all test specifications, procedure sequences and results in a traceable fashion.
The Averna Proligent system also manages production logistics including inventory, allocation and calibration records of test instruments. Combined with its instrument command definition module, it provides an abstraction layer between the test cases and instruments that deliver interchangeability without modifying the testing code. Running in conjunction with NI’s TestStand, it updates test software and testing criteria in real-time, provides an operator interface with test progress-monitoring, aids in unit failure and repair reporting and keeps track of test history of units under test.
Vision Networking
来自纳蒂克的机器视觉系统,质量。的有限公司gnex see a bright future for Ethernet. The company’s In-Sight 1000C vision systems with Ethernet connectivity are being used in an integrated assembly line making headliners for the X400 Jaguar car at the Johnson Controls Automotive (JCA) Speke plant in Merseyside, United Kingdom. The system checks for the presence, position and orientation of components such as grab handles, labels and foam spacers. Electrical checks confirm that console lamps are working correctly and customer color choices are also confirmed correct before shipment. Headliners are built in sequence to just-in-time (JIT) production demands from the Jaguar assembly line, so time and quality are critical issues.
Headliners (interior linings for the roof) are assembled in response to a “broadcast” call from the Jaguar assembly plant, which manifests itself at the JCA factory as a sequence of bar code labels. The task is to assemble the headliners in the same sequence as the cars they belong to, ensuring that color schemes, fittings and various optional extras match exactly customers’ orders. The aim is for a finished headliner to be transported to the Jaguar line “Just in Time” and installed in the correct car as it arrives at the assembly point. A production rate of 40 headliners per hour is targeted, which means that each headliner takes approximately 90 seconds to complete.
This build-in-sequence strategy poses critical production challenges, says Nick Bradburn, JCA manufacturing engineer. “The starting point for us was the need to replace an old line that relied on mechanically-positioned optical sensors for checking the product, and which therefore required lots of maintenance.” JCA was seeking to improve delivery integrity and build quality, in keeping with its continuous improvement policy and goal to exceed customer expectations.
The first two tables of the new four-table assembly line concentrate on adding parts such as locator clips, visors, foam blocks and some electrical items. At each table, the bar code label is scanned first and the correct parts are delivered using a KANBAN system.
Tables three and four differ in having overhead gantries about three meters high above each table, on which four In-Sight vision sensors connected via Ethernet in a Vision Area Network (VAN) look down on the headliners. Here, scanning the bar code also tells the inspection system what test parameters to use and instructions are passed to a master camera in each VAN, which then passes on the data via Ethernet to the other three cameras.
The entire assembly/test process, including the workstations and tables, are under PLC control. Once triggered, the four cameras capture a full image of the headliner in less than five milliseconds, with each camera responsible for one quadrant.
As each set of images is captured for analysis, it is transmitted over the factory Ethernet network to a dedicated server, where it is stored for future use. “This means that we now have 100 percent traceability,” says Bradburn.
Ethernet provides the backbone for a new type of process control architecture, instant communications for test and production data in discrete manufacturing and control and information communication for vision inspection. The adaptation of commercial networking technology has also been successfully installed by original equipment manufacturers (OEMs).
Most manufacturers expect their die cast equipment to last 20 years or more. Yet the demands on automotive parts makers and many other industries to achieve greater precision and higher part counts put them in a quandary—how to significantly improve performance without scrapping millions of dollars in installed equipment.
Rimrock Corp., an OEM of automation equipment for die casting, solved that challenge with an Ethernet-based control system that uses a small PLC from Schneider Electric.
“Process consistency is critical for the die casting industry,” explains Dave Woods, Rimrock’s product development manager. “Everything has to stay the same from shot to shot—constant temperature, same amount of material, same cycle time. The greater the number of acceptable parts made, the lower your production costs. So the precision of the equipment’s control system is absolutely essential for improving quality and reducing costs.”
The new control platform is designed for dedicated equipment that handles the repetitive, one- or two-axis motion routines that make up roughly 80 percent of the world’s motion control applications. It uses the Modicon Momentum M1E controller from Schneider Electric, which has an embedded Web server, built-in Web pages for diagnostics, integral Ethernet port and the ability to handle information transmitted by major sensor bus networks.
伍兹承认,起初,他是不愿意corporate Ethernet into the new control system. “I was a fieldbus snob, but the more I learned, the more it made sense. Every plant has Ethernet now and people are rapidly moving toward it for factory-floor applications. If you’re going to design something new, you’d better do it on Ethernet. It’s good stuff, and it’s so simple.”
Cost savings
Woods points to the immediate cost savings that can be achieved with Ethernet. “Two control systems networked on Ethernet can share an HMI in a small enclosure, for example, and we can locate both of the control systems on a back wall. This gives the customer great flexibility in positioning the operator station. It’s also easy to debug the program from a laptop, which can become a temporary HMI if equipment gets damaged.
To provide a more robust management tool, Rimrock has also created an optional new operating system called Rosco (Rimrock Operation System Console) that builds on the benefits of Ethernet. “You can transfer jobs from machine to machine, store job specifications in the PLC, monitor settings, alarm looks, cycle counts and cycle times,” says Woods. “It provides a wealth of information that you can use for comparative analysis and troubleshooting, as well as instant disaster recovery if a PLC or HMI goes down.”
See sidebar to this article: Ethernet builds "plant of the future"
