All Wound Up

IRA Griffins Sizing Machine uses New Automation Technology

 

In the making of textiles, fiber material is turned into yarn that is then weaved into cloth. IRA Griffin Sons, Inc., Charlotte, North Carolina, makes sizing machines that combine fiber ends and apply a chemical to protect the fiber and yard from stress damage during the weaving process. The company recently reengineered their machines to reduce costs, increase reliability and simplify the control systems. Beckhoff automation products were selected for the job because of their complete offering and compliance to standards such as IEC1131-3 programming standard. The IRA Griffin sizing machine uses Beckhoff’s TwinCAT PC based control software and Profibus Fieldbus cards and a variety of digital and analog I/O signals. IRA Griffin chose Profibus because of its high speed and range of suppliers that offer Profibus Variable Frequency Drives (VFD’s). The sizing machines may have up to 25 coordinated VFD drives and can be the length of a hockey rink, approximately 50 meters.

 

 

According to Barry Shelton, Director of Electrical Engineering for IRA Griffin, after many years of outsourcing control systems, in 1988 the company began producing its own DOS PC-based systems. The DOS based system was very flexible and easily program but did not allow for highly regulated coordinated motion control with the array of Variable Frequency Drives used on the sizing machine.  The VFD’s are provided a speed command in rpm’s or a torque command in percent load via a network. The DOS based system did not provide a consistent timed update to the drives.

 

The next major change came in 1995 when IRA Griffin switched to a PLC based system which offered the ability for highly regulated consistent torque or speed updates to the drives. Usually these updates were provided during the normal PLC scan which ranged from 20ms to 50 ms. Additional interrupt could be used in the PLC program if faster updates such as 5ms was required. The PLC provided better regulated motion control but lacked the flexibility of the DOS based system and IRA Griffin still had a PC on the sizing machine. "Up to that point, we'd been using a separate computer to run the drive control system where we had coordinated drives," Shelton said. "Some machines have three to four drives, while others have 20 to 25 drives. They run in coordinated fashion — speed and torque regulated, with load cell feedback. When we tried to do that in the DOS software program rather than utilizing built-in functions in the drives, the result was a highly regulated scan time," he explained.

 

IRA Griffin used a PLC system until January 2003, when the company culminated a two-year reengineering program and started shipping machines with Beckhoff controls. The program was geared to achieve four objectives: (1) reduce component costs, (2) increase control reliability, (3) lessen the amount of time it took to train customers to troubleshoot, as well as (4) reduce overhead costs attributable to programming each machine.

 

Having prior PC experience, and realizing the PC on the machine was not being utilized to its fullest, Shelton came to the conclusion that it could do everything using one PC and reduce the number of controller and networks used.

 

"Early on, we determined the best way to accomplish our goals was to implement a PC-based control system. It integrates the controls, HMI and PC, plus the use of Profibus eliminates two of the three networks," Shelton said. "We had three separate networks: a proprietary I/O network, a drive control network and an Ethernet network from the controller to the HMI. So we had a rack full of expensive components, plus high priced network cards."

 

Shelton noted that almost all drive manufacturers have a Profibus option. "This dictated that we use a Profibus network, which meant we had to have I/Os and drives that talked Profibus," he noted. ".. We’ve removed the complexity both for us and the customer."  Further, he explained, “So now we've eliminated the PLC and special Ethernet cards that go in the PLC rack, and the special I/O cards that go in the I/O rack...”

 

After settling on requirements for the new control system, a search ensued for a supplier. Shelton's sights were set on finding a single source manufacturer whose emphasis was on PC-based control and supplied as much of the components and software as possible. "We didn't want to have to buy the software from one company, I/O for the PC from another company and so forth," Shelton stated. "The more that one manufacturer could supply, the most likely it would be integrated and easier to implement."

 

Shelton found software from several vendors was not completely IEC 61131 compliant. Finding a fully compliant IEC1131 supplier was important to IRA Griffin given their in depth programming knowledge and need for a flexible but yet powerful programming environment.  IEC1131 allows IRA Griffin to program with the preferred higher level structure text language but also provides the flexibility to show the same programming in Ladder Logic if required. However, the entire goal is to reduce the complexity of the system so the customer is not looking at programming code. Other companies offering a total package either had acquired the makers of the components or purchased the components. "I've seen problems when there's too many people and departments inside an organization involved. Things don't always work as seamless as you expect them to," Shelton said.

 

After finding Beckhoff and determining they offered exactly what IRA Griffin wanted, Shelton's next move was "determining the way Beckhoff does business and if the cost of components matched up with what they were looking for. The purchasing of components is directly handled with Beckhoff which resulted in IRA Griffin getting the best technology at the best price. IRA Griffin performed the entire code translation by themselves thanks in no small part to Beckhoff’s compliance to IEC1131 standard. IRA Griffin was very familiar with the IEC1131 structured text programming and it made for easier transition to the latest technology.

 

This application note was written and provided by Beckhoff Automation.  Beckhoff offers complete system solutions for all branches of automation. The Beckhoff product solutions of the Industrial PC, fieldbus components and the TwinCAT automation software together represent a complete, mutually compatible control system for open automation solutions.

 

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For more information on Beckhoff, please visit their web site at: www.beckhoff.com.