November 28, 2005 by Brian Eberle
In the late 1990s, California fires ripped through neighbourhood subdivisions, enveloping home after home. The fires spread quickly as embers fell down onto rooftops, burning buildings from the top down. For chemist Iain Muir, the devastating scene sparked a formula for the Enviroshake concept, a fire-resistant roofing material made from recycled goods.
Wellington Polymer Technology Inc. (WPTI), a Chatham, Ont.-based roofing product manufacturer, spent six years developing Enviroshake. The high-tech roofing replicates the look of an antique cedar shake, but with the added benefit of performance and durability associated with composite materials.
To move from concept to production, the company looked to system integrator Oxford & Ewing Engineering and Rockwell Automation to design and build a new production control system. In 2001, WPTI transitioned from its small-scale, prototype production line to an automated commercial operation, which enabled it to reduce labour costs and boost production throughput by 300 percent. In 2005, the company expanded to a second production line, boosting production another 100 percent.
The Enviroshake manufacturing process consists of three stages – compounding, processing and packaging. The shingle is made from raw, reclaimed materials, such as post-industrial plastics, ground rubber from tires, hemp, wood and flax fibres. These materials are mixed, melted and pressed into shingle forms. After trimming, the shingles are cooled, inspected and stacked for bundling.
After designing the initial concept and manufacturing process for Enviroshake, WPTI engineers found that simply replicating the initial pilot line on a larger scale would require more than 35 people per shift to operate the line. To ensure the economic viability of the product and meet its business objectives, the company needed to reduce its labour costs and, at the same time, achieve an output goal of 50 squares per day (one square equals 100 square feet of product).
“For us to be competitive, our big concern was to keep the labour portion down in terms of our operational expenses,” says Jim Nash, president of WPTI.
WPTI realized it needed to transition from its labour-intensive, manual formulation process to an automated production line that could be operated and maintained with minimal labour and maximum efficiency. To meet its production goals, WPTI needed control system technology that would provide ease of use for operators, simplify troubleshooting and reduce downtime. The company needed an automated manufacturing process that was flexible enough to meet its immediate and long-term needs, as well as its product throughput demands.
The engineers selected the Allen-Bradley ControlLogix controller to manage all control functions of the production line.
The original line, installed in 2001, consists of two separate systems – compounding and processing – each controlled by its own ControlLogix processor and connected to one another via Ethernet. Within the compounding system, a ControlLogix controller linked to four separate panels via ControlNet handles the control functions. From there, DeviceNet is used to provide a seamless connection to the various local devices, including 12 Allen-Bradley PowerFlex 70 drives used to control speed and positioning of a conveyor as it moves raw material into the mixing bin.
In the processing system, all of the I/O and system devices are connected to the ControlLogix controller via DeviceNet. Operators monitor and adjust the system using Allen-Bradley RAC6182 industrial computers with touch screens that run Rockwell Software RSView Machine Edition HMI software. The RAC6182 computers meet the high-speed, high-performance requirements of the production line, while providing a bright, high-resolution display and easy-to-read images, even in low-light environments. Operators also use an Allen-Bradley PanelView operator interface to monitor the production process and adjust system parameters.
An additional line was added in 2005 to meet the increasing demand. While the basic brains and nervous system of the solution remain the same, explains Nash, the equipment on both lines has been modified, resulting in more robust lines, which have helped to increase cycle time.
Production up, labour down
After installing the automated control system in 2001 and moving from a small-scale prototype production line to an automated commercial operation, WPTI increased production from 20 parts per man-hours to 180 parts per man-hours and reduced labour by 83 percent.
The system also enabled the company to consistently meet its targeted production output goal of 50 squares per day. After modifying the system and adding an additional line in 2005, the company increased its daily production to 270 parts per man-hours per line, resulting in 541 parts per man-hours between the two lines. The company’s new production output goal is 100 squares per day, which Nash says they continue to consistently meet since they’ve doubled their capacity with the second line.
In addition, the company has reduced its scrap rate from 20 percent pre-2001 to two percent today. And the system allows them to program, operate and monitor the production line from multiple locations.
The control system helps speed throughput and improve overall reliability. With RSView Machine Edition software, programmers have a complete visualization package to develop and test HMI screens. The graphical interface ties directly into the production system to help simplify operation and accelerate troubleshooting.
The integrated control platform allows WPTI to reuse the technology from one production line to the next, simplifying engineering tasks and improving operational efficiency. The solution also gives WPTI the flexibility to expand to five lines to meet increased market demands. The company plans to add a third line, as well as a packaging cell to the line, in the spring.
Brian Eberle is vice-president of marketing and sales for WPTI.