Automated SystemsFor several decade

Automated Systems
For several decades the concept of automated handling has offered great potential and limited accomplishment. lnitial automated handling efforts focused on master carton order selection systems. Recently, emphasis has shifted to automated high-rise storage and retrieval systems.

a. Potential to Automate
The appeal of automation is that it substitutes capital equipment for labor. In addition to requiring less direct labor, an automated system operates faster and morc accurately than its mechanized counterpart. Its shortcomings are the high capital investment, development complexity, and inflexibility.

To date, most automated systems have been designed and constructed for specific applications. The six guidelines previously noted for selection of mechanized handling systems are not applicable to automated systems. For example, storage equipment in an automated system is an integral part of the handling capability and can represent as much as 50 percent of the total investment. The ratio of dead weight to payload has little relevance when handling is automated.

Although computers play an important part in all handling systems, they are essential in automated systems. The computer controls the automated selection equipment and interfaces with the WMS. A major disadvantage of automation is its dependency on computer and communication networks. To reduce such dependency, newer automated systems are being linked to the Internet and using standard browsers as the network for controlling warehouse operations. Automated warehouses require tight integration between the WMS and the material handling operating systems.

b. Order Selection Systems
Initially, automation was applied to master carton selection or order assembly in the warehouse. Because of high labor intensity in order selection, the basic objective was to integrate mechanized and automated handling into a total system that offered both high productivity and accuracy using minimal labor.

The general process begins with an automated selection device preloaded with product. The device itself consists of a series of flow racks stacked vertically. Merchandise is loaded from the rear and permitted to flow forward in the live rack on gravity conveyors until stopped by a rack door. Between or down the middle of the racks, power conveyors create a merchandise flow line, with several flow lines positioned above each other, one to service each level of rack doors.

Upon receipt of an order, the warehouse control system generates sequenced instructions to trip the rack doors and allow merchandise, as required, to flow forward onto the powered conveyors. The conveyors in turn transport merchandise to an order packing area for placement in shipment containers and transfer to the staging area. Product is often selected and loaded sequentially so it can be unloaded in the sequence desired by the customer.

When compared to modern automation, these initial attempts at automated package handling are highly inefficient. A great deal of labor is required to perform merchandise loading into the racks, and the automated selection equipment is expensive. Applications are limited to merchandise of extremely high value, with common or standardized master carton size, or situations where working conditions justify such investment. For example, these initial systems were widely tested for frozen food order selection.

Substantial advancements have been made in automated selection of case goods. The handling of fast-moving products in master cartons can be fully automated from the point of merchandise receipt to placement in over-the-road trailers. Such systems use an integrated network of power and gravity conveyors linking power motivated live storage. The entire process is computer controlled coupled with the order and warehouse management system. Upon arrival, merchandise is automatically routed to the live storage position and inventory records are updated. When orders are received, merchandise is precubed to package or vehicle size and scheduled for selection. At the appropriate time, all merchandise is selected in loading sequence and automatically transported by conveyor to the loading dock. In some situations, the first manual handling of the merchandise within the warehouse occurs when it is stacked into the outbound transport vehicle.

The solution of the inputloutput interface problem and the development of sophisticated control systems continues to have the potential to achieve highly effective and efficient package handling. The major problems associated with order selection system automation remain reliability and flexibility. While the information systems and the necessary power systems are generally reliable, failures in either will result in complete operational shutdowns, at one or multiple sites. Highly automated systems are generally not flexible due to required hardwarelcontrol system integration, so it is difficult to be responsive to changes in product or market requirements.

c. Automated StorageIRetrieval Systems
An automated unit-load handling system, or Automated Storage and Retrieval System (AS/RS), that uses high-rise storage is a popular form of automation. Figure 14-6 illustrates the concept of a high-rise ASIRS. ASIRSs are particularly appropriate for nonergonomic items such as heavy boxes or those products in freezer environments. The high-rise concept of handling is typically automated from receiving to shipping. The four primary ASRS components include storage racks, storage and retrieval equipment, inputloutput system, and control system.

The name high-rise derives from the physical appearance of the storage rack. The rack is structured steel vertical storage, which can be as high as 120 feet. The typical stacking height of palletized cartons in a mechanized handling system is 20 feet, so the potential of high-rise storage is clear.

The typical high-rise facility consists of rows of storage racks. The rows of racks are separated by aisles ranging from 120 to over 800 feet in length. Primary storage and retrieval activities occur within these aisles. A storage and retrieval crane travels up and down the aisle alternatively storing and selecting product. A variety of storage and retrieval equipment is available. Most machines require guidance at the top and bottom to provide the vertical stability necessary for high-speed horizontal movement and vertical hoisting. Horizontal speeds range from 300 to 400 feet per minute (fpm) with hoisting speeds of up to 100 fpm or more.

The initial function of the storage and retrieval equipment is to reach the desired storage location rapidly. A second function is to deposit or retract merchandise. For the most part, load deposit and retraction are achieved by shuttle tables, which can enter and exit from the rack at speeds up to 100 fpm. Since the shuttle table moves only a few feet, it must accelerate and stop rapidly.

The storage and retrieval machine is essentially a combined lift truck and pallet holder built into a movable crane. The machine moves up and down the aisle to insert or remove a unit load from a storage bin. When the ASRS operates with unit loads, the process is typically automated. However, the ASIRS often incorporates manual picking when the system selects cases or master cartons. In some installations, the storage and retrieval machine is positioned to service different aisles by transfer cars. Numerous transfer arrangements and layouts are available. Transfer units may be dedicated or nondedicated. The dedicated transfer car is always stationed at the end of the aisle in which the storage and retrieval equipment is working. The nondedicated transfer car works a number of aisles and retrieval machines on a scheduled basis to achieve maximum equipment utilization. The decision as to whether to include aisleto-aisle transfer in a high-rise storage system rests with the economics of throughput rate and number of aisles included in the overall system.