Magazine's 2007 Packaging Line of the Year: Swisher International, Inc.
In July of 2005 Swisher International committed to a major upgrade to their tobacco pouch packaging. The manual operation of boxing the pouches was completely automated. But this new process could not be supported without the reliable performance of the upstream combination scales.
The Eagle supplied model CV combination scales date back to 1988 and have been in continuous service since then. These are highly specialized combination scales that accurately weigh the sticky and stringy tobacco. The mechanical ruggedness and ease of maintenance of these machines prompted Swisher to contact Parsons-Eagle on the possibility of upgrading the controllers for the scales.
The Golden Eagle MicroScan scale controllers have provided over 25 years of reliable operation, and are still supported by Parsons-Eagle. However, the components for these controllers are becoming difficult to source, and Swisher wanted to extend the service life of the scales for many years to come. Additionally they wanted a modern graphical color touchscreen as the user interface to minimize operator training and simplify machine operation.
Some of the goals of the control upgrade included:
• Use existing scale weigh units (14 per machine)
• Minimal rewiring of the scales to simplify installation
• Use existing MicroScan enclosure with its Input/Output (I/O) modules and wiring
• Incorporate a graphical color touchscreen HMI
• Maximize the use of Commercial Off The Shelf (COTS) components
• Increase weighing efficiency and accuracy
In July 2006 Parsons-Eagle engineering started the controller retrofit project. The basis for the controller was the hardware and software from the current line of Parsons-Eagle combination scales. This step provided the following advantages:
• Controller based on an COTS industrial PC computer
• A COTS graphical color touchscreen HMI
• Proven state of the art combination scale software
• Experienced service organization thoroughly training on the controller
• Over 100 successful installations
Incorporating the existing controller as a retrofit to the CV combination scale still had many challenges. The model CV combination scale units incorporated analog voltage outputs, which used bulky, multiple-conductor cables. The new controller utilized an industrial grade network to communicate with the scale units, so each scale unit needed to be an “intelligent” weight processor. Parsons-Eagle designed the scale unit processors to feature:
• Same mounting arrangement as the existing circuit board, so mechanical modifications
to the scale units were not needed
• Standardized DeviceNet NEMA 6P/IP67 cabling/connectors between each scale unit
• Digital signal processing to optimize weighing speed and accuracy
• Automatic self-calibration to guarantee accuracy
• On-board diagnostics to ensure performance and simplify troubleshooting
• Modern surface mount components to ensure parts availability for years to come
The interface for the I/O modules and radial feeder vibrator modules also utilize intelligent processors connected to the same network as the scale units. These processors use the same mounting holes as the previous printed circuit boards and do not require any I/O rewiring.
By employing simple 2-wire network wiring, with a common 24 VDC power source to all the scale units and I/O modules, numerous multi-conductor cables and over one hundred connections were eliminated. The result was simplified wiring and increased reliability.
An additional challenge for the project was the unique configuration and features of Swisher’s CV combination scales. Without an identical weigher, thorough testing of the newly developed system was not possible at the Parsons-Eagle factory. After successful “bench-testing” the controller retrofit kits were shipped to Swisher. The final verification of the hardware and software had to be done on Swisher’s factory floor.
To minimize the conversion time, Parsons-Eagle had a senior service technician and the lead engineer of the electronics and software on-site for the first conversion, and Swisher had their lead electrician on the project. The first weigher conversion had its challenges, which were addressed promptly by the installation team. The first conversion was completed in 4 days and system testing was started. Problems were noted with the logic for the unique mechanical features of these scales and the control of product flow. Some of these issues took a couple of visits by the design engineer to resolve, such as special software enhancements to monitor and adjust for the unique product flow characteristics of chewing tobacco.
A major advantage Parson-Eagle provided on this project was immediate on-site assistance of a senior serviceman and the lead project engineer until the project was completed. All issues were resolved and productivity of the packaging line has greatly increased. During testing, Swisher operator and maintenance personnel provided very helpful suggestions on changes to the operator terminal screens. These were implemented on-site during the startup phase. As a result, the need for training was minimal for the new controls.
After the successful commissioning of the first weigher, the remaining weighers were converted without issues. Each conversion was substantially accomplished in one day, and the weigher was in production the next day.
Several months of operation have proven that the upgrade of the model CV combination scale controls have substantially increased productivity while greatly extending the service life of existing assets.
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