Technology advances in automated high-bay warehouses are enabling a more integrated approach to streamlined material flow.
The latest ultra-efficient automated storage and retrieval system (AS/RS) cranes, and inter-connected automated conveyor systems that minimize touches and facilitate smoother AS/RS transfers, are delivering significant advantages for increasing system uptime in handling unit loads and delivering a more cost-efficient ROI for the high-bays’ overall operation.
As manufacturing and packaging processes increasingly become more automated, with resultant improved efficiency and output, warehouses must keep pace by implementing more streamlined and cost-effective systems. The most streamlined distribution facilities today are highly automated operations, with maximized high-bay, high-density storage utilizing automated storage and retrieval systems (AS/RS). These AS/RS, in conjunction with a warehouse control system (WCS) and warehouse management system (WMS), maintain precision product identification and rotation, provide rapid throughput with over 99.9 percent accuracy levels, and are considerably more energy efficient than less automated facilities.
More so than ever, high-bay distribution facilities need to implement systems that have the flexibility to adjust very quickly and accurately to market conditions, such as increases in SKU range and shortened lead times. Keeping throughput on the move is critical in any distribution operation. It is here where the latest technology in AS/RS cranes, and associated pallet-handling systems, can provide the biggest benefit to a company’s distribution efforts.
Flexibility and Energy Efficiency Define the Latest Generation AS/RS Cranes
ASRS cranes have advanced to an extremely high level of performance, and continue to improve, making them one of the most efficient material handling systems in highly-automated warehouses.
The latest generation of cranes incorporates a unique flexibility, allowing single-deep, double-deep, triple-deep and up to 14-deep pallet stacking utilizing telescopic forks and shuttle cars (moles), with the flexibility to handle one load at a time or multiple loads.
Such cranes can exceed 140 feet in height carrying payloads of 11,000 pounds, traveling at vertical speeds of 325 feet-per-minute (FPM) and achieving horizontal travel speeds of 787 FPM.
Most can operate in a wide sphere of temperatures, ranging from – 38° F to 140° F, equipped with wiring, electrical cables and photo-electronic sensors that are designed to withstand these extreme environments.
High-speed PLCs with integrated controls architecture monitor the movements of the cranes. Receiving directions from the distribution center’s warehouse management system (WMS) and warehouse control system (WCS) via Ethernet, the cranes utilize barcode scanning to direct their movement in the high-bay and the crane’s movement of pallets.
The most efficient stacker cranes that provide the lowest operating cost per hour are now fully A/C powered. This eliminates the costs associated with DC batteries, charging, and associated maintenance. Such cranes have also eliminated hydraulics, which greatly reduces maintenance costs.
Then there is the power-saving technology designed into some of these cranes – the process of capturing and reusing electricity. As the crane carriage lowers, the system allows the power to be captured from the lifting motor, which now becomes the generator. That captured power can be reused for the driving motor.
Aisle-changing functionality has pushed stacker crane operation to an even higher level of efficiency. Although aisle-changing capability in stacker cranes has been used in some form since the 1970s, the speed and efficiency with which these newer cranes can now execute aisle changes makes them a serious option for use in distribution facilities interested in reducing operational costs while improving throughput.
Most high-bay AS/RS cranes are only capable of travelling in a straight line, in one aisle. The limitation of such a dedicated-aisle crane is that one crane is required to service each storage aisle in a warehouse. With aisle-changing functionality, the number of stacker cranes can be matched to the warehouse throughput instead of to the number of aisles, therefore reducing capital investment.
Unlike earlier models of aisle-changing cranes which had limitations in their aisle-changing flexibility, the latest generation of stacker cranes demonstrate efficient aisle-changing capabilities. When the crane gets to the end of an aisle, it can smoothly rotate around the end of the aisle on a curved track, without leaving the track, making for an easy and fast transition between aisles. One version, designed by LTW Intralogistics, utilizes a specialized track to facilitate the smooth transition. It requires no transfer mechanisms, supervision equipment or time-consuming maintenance – problems that have plagued other aisle-changing cranes.
The ability to switch aisles increases redundancy, making all pallet positions within the aisles 100 percent accessible to all cranes. This is very important to maintaining a high level of delivery assurance.
Maximizing Performance of Lifting Drives in Stacker Cranes
Even with ideally configured lifting drives and regular maintenance, rope cables, which are conventionally used on AS/RS stacker cranes, have relatively short change-out intervals. Additionally, rack-and-pinion and direct-drive modalities, from an economic perspective, can be unsuitable options.
Over the past several years, considerable R&D has been focused on developing an optimized drive system for AS/RS stacker cranes. A research consortium consisting of the ContiTech division of the Continental Group, SynchroTech, which is engaged in the production of timing belt pulleys, and LTW Intralogistics, have partnered to develop a new belt technology for the lifting drive of stacker cranes.
The engineered design is a unique combination of pulley and timing belt. The belt’s precision-engineered tooth geometry enables high maximum kinematic values when lifting, while optimizing positioning time. No additional external distance measurements are necessary. The non-slip drive, in combination with the absolute consistency of the length of the belt, can reach new maximum acceleration/retardation values, as well as minimal settling times. This means much better performance with ideal bearing geometries.
Wear and tear, and maintenance, are minimized, and noise levels are greatly reduced because of the optimized tooth geometry. Life expectancy five-times higher than with conventional rope drives can be achieved. The new pulley timing belt drives can be used in stacker cranes at ambient temperature ranges or in deep freeze environments. The net result is less disruption during system operation, longer maintenance intervals, and shorter maintenance operations. With these advantages, belts can now be guaranteed for five years of performance, as is being offered by stacker crane manufacturers like LTW Intralogistics.
Integrated Conveyor Systems Facilitate AS/RS Efficiency
The latest generation of high-bay AS/RS incorporate integrated conveyor transport systems for the efficient movement of unit loads into and out of stacker cranes. Many systems can provide a more versatile alternative to continuous conveyor systems and electric monorail systems.
Transfer cars, for example, can position pallets precisely into stacker crane handover positions, or receive pallets as the stacker crane brings them out of the high bay. Guided by a floor-mounted rail, the autonomous transfer cars can move the pallets where needed, even transporting the unit loads into adjacent areas or buildings. They can be equipped with a multiplicity of load handling devices.
Similarly, vertical conveyor lifts equipped with the same timing belts as the cranes can be integrated to maneuver pallets from upper or lower levels into position for stacker crane induction, or movement after pallets are retrieved from storage via the cranes. Such systems allow for precise and rapid movement of unit loads within the high-bay perimeter, without the need for forklifts. Due to an advanced module-based design, these lifts are perfect for being installed into already existing systems/buildings.
Visualizing Complex Intralogistics Solutions for High-Bay Distribution Facility Planning
One of the most significant technological developments to influence high-bays is not highly-automated systems, but the advent of advanced software for distribution facility planning. Previously a complex and time-consuming process, recently-released software has opened up new and versatile possibilities for designing high-bay warehouses.
One software package was developed, just within the past few years, together with the Institute for Materials Handling, Material Flow and Logistics of the Technical University in Munich, Germany. With this tool, a multitude of alternative approaches can be immediately visualized. The software detects the ideal intersection of the parameter price, performance and storage capacity, and considers the optional use of racking structures and AS/RS stacker cranes, including aisle-changing models, for the ideal layout.
Supporting this is another recently introduced software capability which provides three-dimensional (3D) realistic animation modeling of planned systems for implementation.
Developed jointly by Tarakos GmbH, based in Magdeburg, Germany, and LTW Intralogistics, the software can demonstrate visually almost all systems throughout the high-bay warehouse in perfect interaction with each other. This includes the activities of people and manually-controlled movements of vehicles.
The spatial representation, and the movement through the installation, allow the viewer to clearly visualize the respective processes, identify potential problems, and better determine which processes and systems are most efficient. Additionally, the 3D modeling is a very useful tool for clear presentation to company executives and other participants in the planning process that may not be technically familiar with the systems being planned.
Equal Streamlined Throughput
Such technology advances in high-bay automated distribution facilities provide significant benefits to logistics executives. They facilitate the rapid throughput of materials at near 100 percent accuracy levels. They permit efficient inventory handling and product rotation on a first-in/first-out basis. They reduce warehouse labor, improve accuracy in inventory and order fulfillment. They lessen product and facility damage from fork lift usage.