Lean automation offers higher product quality; less wiring, programming time
Inside Machines: OPA Consulting Services weaves modular manufacturing, higher controls performance, into high-end fabric production. The Quantum Group achieves 10%-15% improvements in woven product quality with 50% less I/O wiring time and 30% less programming time.
The textiles industry has changed dramatically over the years, but specialty yarns and woven fabrics made of advanced materials continue to be a factor in U.S. manufacturing. OPA Consulting Services, a group of knowledgeable engineers based in Colfax, N.C., with more than 30 years of experience in industrial automation and control systems provides its clients with manufacturing technology to stay globally competitive in the textiles marketplace. Typical service technologies include new and retrofit plastic extrusion machines for the manufacturing of advanced fabrics and loom retrofits.
To best serve clients in the cost-sensitive U.S. textile industry, OPA Consulting Services conducts R&D on new automation and controls technology. The familiar mantra "do more with less" applies to all projects. This requires lean automation solutions that can multi-task, handling the work of previously separate hardware controls devices.
"It can be a challenge to specify the right automation controller for the job when the customer needs maximum performance in their manufacturing process while continuously reducing the capital investment costs," explained George Lipovan, president, OPA Consulting Services Inc. "Experts at OPA Consulting Services have developed a knack for striking this delicate balance."
Recently, The Quantum Group, maker of yarns and woven fabrics used for manufacturing products such as office chairs and automotive seating, required a new automation and controls platform to increase end product quality. OPA Consulting Services handles the control engineering work for manufacturing companies in the Quantum Group. The polyester fabric production line involves monofilament extrusion processes to manufacture woven materials designed for office chairs. Retrofit project goals for the production lines included the capability to flexibly move machines in and out of the manufacturing process while maintaining a high degree of equipment functionality and total plant safety.
The monofilament extrusion process for advanced woven materials requires advanced temperature control throughout the process, and the ability to tightly control the ramping up and down of draw stands, which requires coordinated motion. To start the process, plastic pellets are loaded into the line to be melted. The plastic is fed into a screw mechanism with different temperature zones that scale from lower to higher. Melted plastic goes into a spin head where it is then pushed through die tooling and shaped into thin strands. These plastic strands are then placed in a water bath to gently cool down. Coming out of the spin head, the material goes into a quench tank that can either cool or heat the material. Increasing or decreasing the water temperature must be done evenly to ensure product quality. Water in the quench tank must be agitated properly to circulate cooler or warmer water. Precise control prevents too many waves and ripples that can distort yarn before it has fully solidified.
After cooling, the plastic strands are fed into a roller and stretched. Then strands are moved to an oven that bakes the strands to add strength. Then the material is sent to a winding machine with up to 300 positions, depending on the materials being made, and the polyester yarn is fed into bobbins. This material is sold to manufacturers who use the yarn for fabrics or rope.
Traditional PLCs in back seat
Prior to the retrofit by OPA Consulting Services, the monofilament extrusion machine used by Quantum Group was about four years old, and used a traditional programmable logic controller (PLC) system with Profibus and Modbus RTU for communication inside back-to-back control panels. More aggressive production and quality goals suggested a controls retrofit was needed.
"All the electrical panels were in a central location, hardwired to the monofilament extrusion machines through hard conduit, making it impossible to rearrange the machinery to accommodate different production schemes. The mission to make the plant floor more flexible led to the use of PC- and EtherCAT-based controls," Lipovan recalled. "Through industrial Ethernet communication and connection technologies, the machines could be moved around easily and accommodate quick turn-around of fabric prototypes if requested by Quantum Group clients."
Flexible production, programmable safety
Today, all monofilament extrusion machine controls and temperature and pressure monitoring is handled with PC-based control using embedded PCs. EtherCAT Ethernet protocol is used for I/O, motion, safety, and other communications. The retrofit process took about seven months to complete from the design stage to plant-floor commissioning. To address requirements to add and remove numerous machine modules on the Quantum Group plant floor, OPA Consulting Services implemented EtherCAT junction devices.
The devices support hot-swap coupling and uncoupling of EtherCAT I/O sections during operation. This permits the flexible reconfiguration of machine modules on the plant floor, without requiring overly complex shut-down and start-up routines on the part of plant personnel. Using the Ethernet I/O junctions, "it's also easier to reconfigure the machine lines and change the order of machine modules as production processes are changed," Lipovan said. "This gives us all the flexibility we need to prototype materials and lets us play 'musical chairs' with the machines when changing product types," he said.
As the connectivity solution was settled, OPA Consulting Services moved aggressively into consolidating the controls platform and implementing a lean automation architecture. The retrofit monofilament extrusion machines are now equipped with embedded PCs using Intel Core i7 processors (2 cores) running next-generation PC-based control software and the Microsoft Windows 7 Embedded Operating System.
OPA Consulting Services implemented the "supervisory control system on the same embedded PC as the PLC program for simplicity's sake," Lipovan said. "This platform had to be powerful enough to handle coordinated motion between five machines, and efficiently process 20 PID loops while handling and adjusting hundreds of recipes."
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