The notion of modular manufacturing started to take shape in the early ’90s in the automobile industry when U.S. and European manufacturers began feeling economic pressures from the more flexible Japanese manufacturing plants built in the U.S. Several of these plants produce as many as five different automobile models on one line. Leading this build-to-order capability was the installation of machine modules designed for instant changeover based on customer requirements.
This continued push to flexibility has expanded to other industries, forcing machine builders to adopt new, more agile machine designs. This new focus on flexibility most often requires machines with multiple stations, where each station does a specific type of operation, but isn’t necessarily the same for every part or assembly being produced.
The User: the Ultimate Judge
Flexible, modular manufacturing can be found at John Deere Harvester Works, East Moline, Ill. With modular manufacturing, its row crop planter production can produce build versions on one assembly line. Parts manufactured to order by cells adjacent to the assembly line are moved to respective assembly areas when the planter requiring those parts moves into position. “The improvement in factory production volume, finished product inventory cost, and delivery time justified the cost of changing our production methods,” states Bill Fulkerson, technology and information analyst at Deere.
Modular Maximizes Configuration Choices
To stay in tune with this trend toward modular manufacturing, machine builders must develop control schemes with the same modularity and flexibility, while reducing installation and commissioning costs. Improvements from open standards and robustness of fieldbus networks have done much to meet the new modularity criteria.
As this continues, there’s a growing need for higher concentrations of signal capturing via machine-mounted I/O. Pre-terminated field connections mean remote I/O can be installed and debugged quicker because of fewer wiring errors. The resulting decrease in cost is substantial when compared with the cost of wiring to junction box terminal strips.
“The I/O used on machines really is dependent on the machine designer, but for the most part, small, block-style I/O is becoming increasingly popular when the number of points at a node isn’t extensive,” says Dave Cole, president Cole Controls, Grabill, Ind. As a system integrator for PLC and network-based machine control solutions, Cole works with a number of fieldbus systems, many of which are connected directly to remote I/O racks distributed around the machine envelope. Cole also sees a number of installations in which a fieldbus is used as the primary data link between distributed intelligent I/O slaves, but the slaves incorporate a secondary sub-network such as AS-i or HART to connect to various locally distributed I/O blocks.
“There’s a big push to link smart devices via fieldbus or Ethernet versus running discrete wires because of installation costs,” adds Cole, pointing to an application in which Profibus links a remote, 400-hp, Atlas Copco ZR315 screw compressor to a central data-collection terminal. This application, installed at the Pernod-Ricard Seagram-brand distillery in Lawrenceburg, Ind., uses a legacy Siemens 505 PLC as the central data-collection intelligence source to interrogate the compressor over Profibus. The compressor has its own intelligence and distributed I/O. The I/O network within the compressor unit is a proprietary sub-network that collects data on compressor oil temperature and pressure, water temperature and pressure, air temperature and pressure, as well as speed, and then records how long it operates at certain levels.
FIGURE 1: BURNER CONTROL AT THE SOURCE
Wired Ethernet connects distributed control boxes, while an RS-485 sub-network connects VFDs and burner controls to the main network of a walnut dehyrdrating machine. Wireless Ethernet distributes data to the remote PC to monitor trending and history for all operations.
Although simple in concept, this use of distributed I/O optimizes compressor usage, reducing power costs while maximizing usage. “We’ve used Profibus extensively over the years for controlling or monitoring scales, safety barriers and other equipment, but we often have to convert Profibus to another network that’s standard on machines or equipment we purchase,” says John Netzley, senior staff engineer at the Lawrenceburg plant. Atlas Copco compressors use DeviceNet as the standard fieldbus interface. To interface with the Profibus network, Atlas supplied a bridge to convert DeviceNet to Profibus at the compressor.
Cole’s observations are supported by Steven Redcay of Phoenix Contact. “Selecting an I/O system that’s open to multiple networks enables machine builders to standardize on an I/O structure with the flexibility to choose the best network for each individual application,” says Redcay in a recent white paper. “This can shorten design time for the machine builder, and reduce training and maintenance costs for the user. Block-style I/O offers lower installed costs and is optimized for highly distributed digital signals; whereas, modular I/O structures allow higher concentration of signals at one location, but have a higher installed cost.”
Another integrator, Applied Instrumentation (AI), Concord, Calif., takes the modular design approach to the food-processing industry. “For our customers, the total number of I/O points is fairly small, but they often are distributed over a large floor space,” says Don Osias, AI’s president. “Only a few critical I/O points are at each location, and cost is more important than size or density.” For these applications, Applied Instrumentation uses Opto 22 Optomux products. “The I/O mixes digital and analog I/O on the same rack, which is attractive to us as designers, but, for most of our customers, Optomux still wins when we price out the solutions,” claims Osias.
AI’s solutions, though focused primarily through one supplier, speak directly to the new connectivity approach taking place in machine automation today. The company upgrades many legacy machines to communicate over Ethernet for easier debugging, more seamless data transfer, and easier equipment monitoring.
The control of walnut dehydrating machines is an apt example. AI implements remote I/O racks with 16-G4 I/O modules and an Ethernet brain-board (See Figure 1 above). This minimal hardware configuration controls air doors, fans and burners distributed throughout these huge machines. Data also is collected and delivered to remote PCs.
“We provide reliable automation of processes that were previously operated manually,” says Osias. “The primary benefit is that a smaller, but more skilled staff can operate a large plant with better precision than before. The newest release of Ethernet-enabled Optomux brain-boards for this and similar applications provide better data logging, better remote support, and much faster troubleshooting.”
On the European Front
Modular machine concepts, not surprisingly, are a global trend. Rising energy and raw material costs force companies to pay closer attention to operating costs. Quint sdi GmbH, Hessebeck-Kailbach, Germany, provides energy and process management systems (EPMS) designed to reduce operating costs for offset printing presses by using distributed automation technology (See Figure 2 below).
FIGURE 2: COOL PRINTING
In conventional offset printing (left) there’s a clear savings potential if a large portion of the fountain solution can be treated and reused. Quint’s EPMS (right) cools the used water, filters it, and adds back the necessary amounts of additive and alcohol. The foundation for the system is distributed controls such as IP67-rated remote I/O modules and a centralized control platform.
Using variable-frequency-controlled drives for its pumps, Quint minimizes the energy needed from the main supply for cooling and preparing fountain solutions for the presses. Pumps and aggregates operate only for the time necessary to complete the printing. “We only remove excess energy from the process,” explains Dieter Jahn, software development engineer at Quint.
In conventional offset printing the fountain solution is mostly tap water. To improve its properties, it’s enhanced with additives—usually isopropyl alcohol, when an alcohol solution chamber is used. The proper solution ensures a stable ink-water emulsion, prevents corrosion and algae build-up, and improves the drying process.
There are clear savings if a large portion of the solution can be treated and reused. Quint’s EPMS cools the used water, filters it, and adds back the necessary amounts of additive and alcohol. “What makes our preparation unique are the levels of precision and consistency we achieve regarding the dosage and temperature of the solution,” Jahn points out. “We also stopped limiting our work to fountain solution cooling and preparation. Today we deal with all aspects of energy management.”
The foundation for the system is distributed controls such as IP67-rated remote I/O modules and a centralized control platform from Bernecker & Rainier Industrie Elecktronik GmbH (B&R), Egglesburg, Austria. With B&R’s remote I/O modules, Quint designers created a remote control architecture that simplified wiring and reduced the housing cabinets required.
“We work with water a lot,” notes Jahn. “Thanks to the IP67-protected I/O modules, we can construct the system without switching cabinets, despite the remote structure. When we expand, we don’t have to worry about terminals and such. We simply install the sensor cable.”
Machine Builder Benefits Big
As a designer and manufacturer of coil-handling and press-feeding automation systems for more than 50 years, Automatic Feed Co. (AFC), Napoleon, Ohio, produces turn-key systems for blanking press lines, which unwind metal coil for cutting body parts for the automotive industry. Each system typically includes 10 different machines that become a fully integrated line.
When AFC starts a project, it includes a detailed list of customer requirements, including all customer approved components for each machine. These components change from one customer’s machine to the next. To meet the exact customer specs, AFC engineers often found themselves reconfiguring the entire control system architecture to accommodate a component brand change.
Not surprisingly, the costs and startup time to re-engineer each new project can be excessive, so AFC sought to standardize its machine architecture.
AFC needed a control platform that would assemble and wire machines 50% faster and reduce start-up time by 70%, while meeting the specific performance demands of its customers. “We recognized the need for a standard approach to building our machines, but past market conditions didn’t support pure standardization for coil line systems,” says Kim Beck, president and CEO, AFC. “We were driven simultaneously by cost reductions, ease of use, flexibility and quality improvements, but we still lacked the comfort of a solid, standard machine configuration.”
To provide the necessary machine variability, the company developed Distributed Device Architecture (DDA), a new design approach that takes control devices out of traditional enclosures and distributes them throughout the machine (See Figure 3 below).
|FIGURE 3: MODULAR, MOVABLE|
|To provide the necessary machine variability, Automatic Feed Co. developed Distributed Device Architecture (DDA), a design approach that takes control devices out of traditional enclosures and distributes them throughout the machine.
With products from Rockwell Automation built for on-machine applications, AFC simplified its machine designs, had fewer wiring errors, and accelerated installation.
“Because the components are moving from enclosed cabinets to the point of application, it improves our customers’ mean-time-to-repair (MTTR), which reduces downtime and increases overall plant productivity,” Beck says. “Since each subsystem is based on a standard design, this allows the customer to specify components with minimal impact on our design process.”
Products ideally suited for on-machine applications enable a device-neutral architecture in which every aspect of the equipment is segmented into standard sub-systems, each with self-contained, modular mechanics, control devices and logic. One such component is Allen-Bradley ArmorStart motor starters. “This allows us to plug motor and brake cables into them, requiring less hardwiring time and reduction in control panels,” reports Doug Adams, senior engineer, AFC. With the new DDA approach, the company standardized the control architecture of its machines, reducing parts by a factor of three.
“Rockwell’s Logix control platform allows us to adjust to the components that a customer requests without redesigning the machine,” says Beck. “We can create a line based on our standard architecture much faster than we could before because we’re not reinventing the wheel each time a customer specifies a component.”
AFC compared a line built in 2003 without DDA to a 2005 line that included DDA, with the following results:
- 70% reduction in cables
- 87% fewer hardwired terminal points
- 16% fewer enclosures
- 93% reduction in network communication troubleshooting time prior to shipment
- Approximately $100,000 savings in wiring time
- 86% less network communication troubleshooting time after shipment
- 25% (about $50,000) reduction in electrical hardwire component costs
|About the Author|