AGVs Control Traffic, Improve Operational Efficiency for Fiberglass Yarn Manufacturer

PPG Industries, Inc.’s Fiber Glass Division is achieving maximum efficiency at its manufacturing center by automating its facility with robotics and an AGV (automated guided vehicles) system and control software supplied by AGV Products, Inc. (Charlotte, N.C.).

“Our goal is to push the winding process -- once the ovens start melting the glass we must constantly pull the strands through the winders,” explains Bernd Brockmueller, manager, Automation and Machine Design for PPG Industries, Inc.’s, Fiber Glass Division. It is a daunting task considering the number ovens and yarn types all running continuously. Inventory, traffic control and operational status of its fiber glass yarn processing system is now fully automated with the implementation of robotic systems and AGVs. The AGV system interface with the robotic handling machines that load and unload processing equipment. Once the control system is given the order, it signals the AGVs to move product from step to step. “Our facility has attained maximum efficiency, operators simply set basic parameters and the control systems take over,” Brockmueller says. “Since integrating the automated systems in 1997, we continually set new production goals, efficiently running 24 hours a day, 7 days a week, 365 days a year.”

Customers Demand More

PPG’s fiber glass businesses continue to expand through innovation and leadership, making PPG Industries (Pittsburgh, Pa.) the second largest global manufacturer of continuous-strand fiber glass. PPG’s Reinforcements business (RP) unit is a world leader in manufacturing continuous strand fiberglass used in a range of plastics applications. Customers manufacture boats, tubs and showers, windmill blades, reinforced pipe, automobile and appliance components, and a variety of other plastic items.

PPG Fiber Glass’ Electronic and Specialty Materials business (ESM) is the world leader in manufacturing specialty fiberglass yarns. ESM products become the backbone of products such as electronic printed circuit boards, aircraft laminates, insect screens, cement boards and foil insulation. The ESM business is also supplies engineered yarns to reinforce fiber optic and other telecommunication cables, to manufacture high-temperature fabrics, reinforced tape products, medical casting materials and a range of industrial products.

PPG Fiber Glass continues to invest in quality, with examples that include Sigma Logic Methodology, Lean Enterprise, and Quality Action Teams (QAT) with the goal of adding customer value through innovation and continuous improvements.

The Chester, S.C. plant was inaugurated in 1996 and is dedicated to the production of fiberglass rovings (See "Making Fiberglass Yarn" at end of article.). The plant uses robotics and sophisticated automation in production of PPG glass products. Brockmueller adds, “The AGV system was a major addition to our processing operations and helps us meet our customer service goals.”

Keep the Winders Busy

“The task of the AGV system is to pull the product through the processing stages,” explains Brockmueller. “Once the ovens start melting glass, we must keep the products moving through the various processing stages. The high-speed winders are the critical point, so we make sure empty trucks are always available to pull the product spools through the system. We have eight AGVs that handle the job.”

For the most part, this system is an operator driven system; operators request the system to do something for them. The operator will request a "setup" from the stationary controller system. The stationary controller system is always in communication with the AGV's; monitoring their locations and directing them to complete specified work. There are also I/O driven portions to the system, in which the stationary system is monitoring load sensors and based on a positive feedback, will generate automatic orders to the AGV's to retrieve the load and deliver it to the warehouse.

Brockmueller explains, “We have specially designed transport trucks that each carry the fiberglass packages. The system controller will call the AGV to pick up the truck as soon as it is fully loaded. The AGV has outrigger forks that fit under the hand trucks and lift them slightly off the ground for transporting to the conditioning/drying area. The AGV ‘shakes hands’ with the robot telling the robot to call another AGV to bring an empty truck to the area for filling.”

The AGV carries the full truck from fiber forming to the drying oven where the truck will roll through the oven drying the yarn. Each yarn type has a specific drying time in the oven and it may take 14 hours for certain types. The AGV control system tracks the drying time for each truck in all ovens. As the truck exits the oven another AGV carries it to the cool down area. The yarn will stay in the cooling area until there are enough spools to fill a specific customer order, for instance, it may take as long as 24 hours to accumulate 3 pallet loads of a specific yarn.

Once the yarns needed for specific fiberglass “orders” are accumulated, they are palletized and ready for shipment to the customer. Again, AGVs carry the palletized packages weighing 2,000 lbs. from the processing lines to the packing area.

Brockmueller concludes, “Since implementing the AGV system we have reached production goals never realized before. Now, with a simple double-click of a mouse, at any point in time, the control system will tell us location and status of each product in production.”

AGV Details

The AGV’s used at PPG’s Chester facility are customized FLA fabricated from a standard AGV design. The AGV’s handle PPG’s standard fiberglass transport carts and move the carts throughout the entire manufacturing process. Each cart is inducted into the system by operator bar coding to identify product type. The AGV system’s off-board controller reads this information and automatically generates the transport orders for the next process step. Once the product reaches the Work in Process (WIP) area, the time is recorded in a Microsoft database by the off-board controller and will not allow that product to leave until its time has expired.

The FLA AGVs use inductive wire guidance throughout the facility and the system includes opportunity charging. The AGV, when not doing work, will travel to designated areas where there are two single pole charge plates mounted on the floor. The AGV will park over one of these charge plates so that the charge “shoes” on the AGV are correctly aligned for charging. The AGV will remain there until it is requested to do work.

The AGV’s have microprocessor-based control boards that monitor all AGV functions, including the monitoring of digital and analog inputs and outputs. Inputs are load handling, safety devices, steer and drive feedback, lift positioning feedback, in the form of limit switches and digital encoders, and analog signals from antennas strategically located on the AGV for guidance monitoring. The outputs consist of automatic operation of the steer and drive unit to facilitate forward and reverse travel based on the antenna.

Making Fiberglass Yarn

The manufacture of fiberglass yarn starts with the mixing of batch ingredients in precise proportions. This mixture, or batch, is then melted in a high-temperature furnace. In the molten state, the viscous glass flows through bushings containing hundreds of tiny orifices to form filaments that are attenuated, cooled and gathered together to form strands by high-speed precision winders.

A chemical treatment, usually referred to as “sizing” or “binder,” is applied to the filaments during the winding process. PPG fiberglass yarn products are coated with several binders that serve as a basic yarn “sizing”. Binders are designed to protect the yarn during subsequent processing and to provide optimum compatibility with the finishes or treatments needed for specific end uses.

After winding the yarn is conditioned, oven dried and then accumulated in a cool down area for twisting. Various drying times and types are used and they are dependent on final product. Yarn spools are loaded onto pallet stands and are allowed to cool. Only full pallets are delivered to the twisting process.

Basic fiberglass strands (each strand is composed of filaments) are then twisted to achieve a product which meets the processing requirements of the customer. After conditioning, fiberglass strands are placed on twist frames for transferring the strand to bobbins. The strands are processed into yarns of varying types as specified by customers. Yarns are identified by the amount of twist per unit of length (called “turns per inch” or “turns per meter”). The direction of the twist is designated with an “S” or “Z” for further identification.

When required, twisted yarn is the input to the warping operation for fabricating a beam of many parallel ends for use in customer weaving operations. Customer weaving needs, which determine the number of yarn bobbins that have to be used to feed a single beam, defines the number of ends, along with beam width and length.

Passing yarn through high-pressure air stream makes texturized yarn. A special binder may be applied to the texture product to set the texture for specific customer applications.



Sister Plant Benefits from AGVs

AGVs are also used at PPG's Lexington, N.C. facility to transport packaging kits from the packing area to the warehouse. The AGVs are specialized SLV (side loading vehicles) fabricated under a standard AGV design. The AGVs are incorporated to handle a multitude of different sized pallet loads and weights. The side loading mechanism allows the AGV to drive adjacent to the load positions and retrieve the pallet loads easily and quickly.

The unit load consists of different sized pallets and cartons that contain a variety of different sized textile holders, for example, bobbins. The pre-assembled pallet loads match the PPG and customer specifications for the final product requested. The AGV will retrieve "setup" pallets from a storage area and deliver to stations where the pallets are packed with product.

The AGV's are designed to transport these different unit loads from the packing area to the warehouse where they are deposited on a gravity conveyor and then processed for storage or shipment. During travel, the AGV must travel down a three-degree incline. The AGV’s control board consistently monitors the speed and keeps that speed to a desired level by regenerative breaking, ("plugging"), to safely traverse the length of the incline.

The SLV AGV's use inductive wire guidance throughout the facility and the system includes opportunity charging. The AGV, when not doing work, will travel to designated areas where there are two pole charge plates embedded in the floor. The AGV will park over one of these charge plates so that the charge "shoes" on the AGV are correctly lined up and initiate a charge sequence. The AGV will remain there until it is requested to do work.

The AGV's have microprocessor based control boards that monitor all AGV functions, including the monitoring of digital and analog inputs and outputs. Inputs are load handling, safety devices, steer and drive feedback, lift positioning feedback in the form of limit switches and digital encoders, and analog signals from antennas strategically located on the AGV for guidance monitoring. The outputs consist of automatic operation of the steer and drive unit to facilitate forward and reverse travel based on the antenna, steer and drive feedback. Also there is automatic operation of the lift mechanism that allows the AGV to raise and lower the forks to predetermined positions in order to retrieve loads. Once in these positions, the lift mechanism can traverse outside of the contour of the AGV in order to retrieve the loads in the pallet stations.

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