The latest generation of AGVs for carrying heavy loads throughout aluminum manufacturing facilities – with a significant reduction in vehicle weight – are minimizing maintenance and power requirements by up to 60 percent, delivering a new level of streamlined performance and cost efficiency for primary metals manufacturers.
The primary metal industry has long relied on Automated Guided Vehicles (AGVs)s to transport heavy-load aluminum coils, ingots, plates, wire, work rolls, turnstiles, and press brake dies and punches, into and out of storage, and throughout both hot and cold production processes. Interfacing with multiple auto-transfer devices, AGVs provide reliable heavy-load raw material and product handling, with less potential for product damage, compared to manual and overhead methods of transport. AGVs can perform tasks that are not possible with other transport systems – such as the uniform movement and positioning of huge loads of over 200,000 pounds, to within a fraction of an inch of their designated targets, without rush and noise, and with a high degree of safety for workers and the operational environment.
Despite obvious benefits, the heavy loads that AGVs transport impart huge forces upon these vehicles, resulting in significant maintenance and power requirements to keep AGV fleets functioning. Now, a generation of new lighter weight AGVs has become available, which are considerably lighter than conventional heavy-load AGVs. The new models incorporate design, navigation, sensor and power improvements that significantly streamline their operational performance, cost of maintenance and ROI, over and above prior AGVs used in the manufacturing of nonferrous metals.
AGVs built for transport of heavy loads of primary-metals or finished products – such as 60,000 pound aluminum coils and 120,000 pound ingots – have typically been designed so that the weight of the AGV is 40 to 60 percent of the expected load. This has now changed with the introduction of a new generation of lighter, more efficient AGVs, which are engineered to reduce wear and tear, and energy, and weigh considerably less than conventional AGVS.
“This weight reduction has been achieved through a complete redesign of how heavy-weight AGVs have been engineered since the early 1990s,” said Chuck Russell, Vice President at Transbotics Corporation, a manufacturer of heavy-load AGVs. “Factually, there has not been a significant major redesign in the basic structure of these vehicles over the past 20 years, until now.”
These new lighter weight AGVs not only match the payload requirements of contemporary heavier models, but match or exceed those vehicles’ structural stress thresholds.
“The implications of a 5 to 20 percent weight reduction are of enormous consequence to companies operating within the metals industry,” added Russell. “Maintenance, and wear and tear requirements, for the vehicles are commensurately diminished. Energy draw needed from batteries is reduced. And repairs required for plant floors, caused by the AGVs and their load weights, are significantly lessened.”
Electronic Independent-Wheel Steering
These new AGVs have also been engineered with electronic independent-wheel steering, which has considerable implications for AGV operability, vehicle maintenance and repair requirements, and damage to plant floors.
Many heavy-load AGVs are equipped with Ackermann steering links. But Ackermann steering geometry only approximates the required steering angles, allowing inaccuracies which result in wheel scrubbing, concrete and tire wear, considerable repair and maintenance requirements, and increased amp draw.
“These AGVs with electronic independent-wheel steering, do away with Ackermann steering geometry completely, and the issues it creates,” continued Russell. “Additionally, the vehicle can now perform tight maneuvering and smoother cornering with all-directional vehicle travel.
This enables shorter trips, reducing the fleet size.”
Since battery run time is directly proportional to vehicle and payload weight, reduction in vehicle weight on the new AGVs directly impacts the run time of its batteries. Therefore, any weight reduction exhibited by these new-generation AGVs translates into longer run time from the batteries before requiring recharge. New battery technology also contributes to further weight reduction, faster recharge times and overall better system performance.
The new AGV’s, with their weight reduction and electronic independent-wheel steering deliver a sizable reduction in maintenance and repairs. Realistically, as much as a 60 percent reduction in annual maintenance, per vehicle, can be achieved.
“Contributing to this is the accessibility of the AGV to perform maintenance or repairs,” explained Russell. “With conventional heavy-load AGVs, access to wheels, gears and other moving parts is, for the most part unexposed, requiring the vehicle to be hoisted or moved into a pit to be serviced. This is an inherent difficulty prevalent in many prior heavy-load AGVs.”
Because of the unique design of these new AGVs, however, wheels, gears and other moving parts are easily accessible without the need of hoisting or service pits. This means that much of the maintenance requirements, and even repair, can be performed on the plant floor, without major interruption to the use of the vehicle.
The latest new-generation AGV systems comprise one or more vehicles that move around predetermined routes to perform transport functions as directed by a stationary control system. They are equipped with navigation systems, based on laser and/or inertial guidance. Laser navigation systems are based on target triangulation to keep the vehicles on course. Inertial navigation systems use a gyroscope onboard the AGV to detect changes in vehicle direction and attitude.
“Both navigation methods can be seamlessly combined in a concept called multi-navigation, which switches back and forth from laser to inertial guidance without stopping the vehicle,” added Russell. “This allows the AGVs to move throughout a plant and outside, where one system alone may not have access to the physical surroundings or weather conditions necessary to support that system.”
Further, these new AGVs use the latest in safety laser technology, incorporating 15,000 lux systems, with a 10 times higher tolerance to light compared to most conventional heavy-load AGVs.
The smooth functioning of these new AGVs is dependent on their controls system, which has the task of coordinating the orders received from the plants’ process system or ERP, then directing the work for the AGVs. These AGVs utilize a Windows and SQL database architecture that is able to uniquely operate within a single platform.
The controls provide real-time management of the system’s operation, including management information, load prioritization, load status, productivity statistics and reports, and workload analysis. It allows associated functions to be automated – such as with receiving, raw materials storage, hot line processes, roll mill processes, cold mill processes, finished product storage and shipping.
Improved Production Efficiency
Heavy-load AGVs enable significant efficiencies to primary metals manufacturing. They improve production flow by bringing material to the operators, thereby cutting cycle times, and eliminating wait, walk and search time. They reduce work-in-progress inventory. They cut labor costs by eliminating simple jobs related to material movement, and permit reassignment of those workers to areas where they can add more value to the plant. They virtually eliminate product damage with gentle handling of loads. And they provide flexibility of process flow within the plant, as needs change. Now, with this latest-generation of heavy-load AGVs, aluminum manufacturing plants can further streamline their operations, and realize improved cost and production efficiencies.
(Jim McMahon is one of the most published writers on industrial and manufacturing issues. His features on the latest technological advances and industry dynamics have graced the covers and pages of more than 2,500 publications worldwide, and thousands more online sites. His firm, Zebra Communications (www.zebracom.net), is a leading provider of feature story campaigns for industrial and technology companies.)