Introduction:

A warehouse has been generally perceived to be a place to store things, out of sight, and out of mind, certainly not an image of high tech or sophistication. In fact most plant modernization efforts have typically ignored or bypassed the warehouse completely. But, in today’s competitive manufacturing and business environment, the vital role of warehousing has to be properly understood. The warehouse is a critical link between a manufacturing plant and the external world and significantly affects the performance of the entire manufacturing and logistics system. The time to pay attention to the warehouse and to integrate it in the material supply chain Is long overdue, especially in India.

Automation in warehousing immediately conjures the image of a high-rise Automated Storage Retrieval System (AS/RS). Therefore, before proceeding with a general discussion on automation in warehousing, let us first understand what is an AS/ Rs. Typically. AS/RS involves the use of high-rise racks with a storage machine operating within the aisle, serving both sides of the aisle. Loads are stored in the racks and retrieved either automatically or in a semi-automated fashion. The loads could either be unit loads that are palletized, or, in some cases, involve drawers and totes that are used to store smaller parts. The heights of AS/RS systems can vary, depending on the application. The highest systems are 100 feet high. But these are few and far between.

The main advantages of a high-rise storage system are as follows:
• High density of storage by utilizing the cubic space available and with the help of narrow aisles.

• Tighter inventory control through computerization resulting in higher inventory accuracy.

• Reduced access in the aisles, improving the security of the material.

• Increased space utilization via random storage versus dedicated space allocated to different parts.

• Ability to tie the storage system to the manufacturing and the distribution systems via computer control, permitting a higher level of system performance.

• Better utilization of storage and retrieval equipment.

• Reduction in manpower. Components of an AS/RS:

1. Rack Structure: An Automated Storage Retrieval System consists of a rack structure. The racks can either accommodate palletized unit loads or totes/bins or drawers, depending on the size and characteristics of the part. Other types of racks are cantilever racks, flow racks, and any other specially designed storage structure. The rack openings are typically standardized, as the cost of non-standard, or customized, openings can be significantly higher than those for the standard openings. The pallets are typically slave pallets, i.e., they do not leave the warehouse to customers, including manufacturing. The reason for this is the rough use received by pallets in loading/unloading and in transportation. Damaged pallets with nails or slivers sticking out can cause serious problems in the operation of an AS/RS. Also, the rack structure can be either free standing, or the building can be rack supported.

2. Storage/Retrieval Machine: The storage retrieval (S/R) machine operates within a storage aisle. Its function is to store and retrieve loads. It is designed for applications requiring high lifts, fast speeds, control features and accurate positioning, not available in other types of material handling equipment. Typically, it consists of a structural frame of either a single or multiple mast construction. The lower portion of the frame has wheels which normally run on a single floor rail or two rails. The frame is guided by support from the storage structure at the top of the structural frame.

The structural frame of the S/R machine is used to guide the carriage for accurate locating of the load as it is raised and lowered. The carriage carries the mechanism to carry, store and retrieve the load. The storage and retrieval mechanism can either be a shuttle device or a pushpull arrangement with a pin to engage/disengage the load. The storage and retrieval mechanism also must be able to transfer loads to and from conveyors, shuttle cars and Pick and Deposit (P & D) stations..

The S/R machine is typically captive in a single aisle, with one S/R machine per aisle. There are cases, however, where the S/R machine can operate in more than one aisle. In this case, a transfer car is required at the end of the aisle to transfer the S/R machine from one aisle to another. The choice of one versus the other configuration depends on the cost and the throughput requirements. Typically, S/R machines service both sides of the aisle and can operate in very narrow aisle configurations, where the aisle is only marginally wider than the load. The S/R machines can have a person on board, or can be completely unmanned. The person-on-board systems permit less than a full unit load to be picked from a storage location.

3. P & D Stations (Transfer Stations): Pick and Deposit (P & D) station is a location at which a load is entering or leaving storage is supported in a manner suitable for handling by the S/R machine. These may be a simple as a fork truck setdown sation, a shuttle car, a conveyorized section or an Automatic Guided Vehicle System (AGVS). Normally, every AS/RS has at least one pick-up sation and one delivery station. P & D stations are usually located at the end of the storage aisles. Sometimes the P & D stations are integrated with an in-plant or warehouse transportation system.

Other Automation: 

In addition to conventional AS/RS, there have been a number of systems that do not employ the typical aisle-captive Storage/Retrieval machines. Some of these forms of automation will be briefly reviewed here.

1. Automatic Guided Vehicles (AGVs): One of the departures from the aisle-captive S/R machine is to use AGVs to not only transport the loads between manufacturing or shipping and storage, but also to and retrieve the loads from the storage locations as well. In this case, a wire path is typically used to bring the vehicles into the aisles and to locate it at the appropriate horizontal location. A lift/lower mechanism is then used to raise or lower the load to and from the rack. Sometimes, the AGV takes the fonn of an unmanned lift truck. The main limitation of the AGV system is the limited height to which loads can be raised.

2. Carousels: An alternative to moving a vehicle, with or without a person on board, to the loads, is to move the load to a P & D station. Both horizontal and vertical carousels achieve this end. Vertical carousels provide a better utilization of the cube, while horizontal carousels permit parts picking In a conventional method as well. Carousels can be interfaced with robotic arms to automate the parts storage and retrieval process.

The Past: 

In the U.S. automated warehousing in the 1960’s and 1970’s meant AS/RS. One of the driving forces for this phenomenon was the doubling of the value of business inventories between 1962 to 1972. The value of the business inventories tripled between 1972 and 1982. The explosion in inventory in the 1960’s and 1970’s led to considerable growth in warehouse capacity and the need for significantly increased control of inventory. AS/RS was the solution of choice.

The early euphoria of AS/RS in the 1960s and 1970s gave way to a rather flat decade in the 1980’s. This was due to a much slower growth in manufacturing Inventories, which grew by only about 25% between 1972 and 1982. The competition from the Japanese and the need to control manufacturing costs, forced the U.S. manufacturers to find ways of reducing inventories. Suddenly, the darling of warehouse professionals became something that people did not want to talk about. A number of projects were. in fact, abandoned mid stream. There were several AS/RS systems that were lying empty and had to be dismantled in the 1980’s.

AS/RS became a bad word during the 1980’s when growth in business and industry came, not from a growth in inventories, but from an increase in Inventory turns. The focus was on reduction of inventories, small batch production and just-in-time delivery. While no one can argue with the objectives of just-in-time and reduced inventories, the tactics adopted by business to adopt efficient manufacturing practices were too extreme and lacked sufficient thinking on the part of management when it came to warehousing.

Companies began to Indiscriminately cut any and all funding for warehouses, as Inventory was “evil”. What a number of these companies did not realize is that although a number of the early applications of AS/RS were not justified, but several were doing an excellent Job. The one area in which AS/RS was, and still is, a very viable option, is distribution. Also, another development had taken place in automated warehousing systems in manufacturing. A number of smaller, decentralized mini S/R systems made their appearance in manufacturing in the 1980’s. Interestingly, the trend in distribution, was quite the opposite. The trend has been towards greater centralization, and larger, more automated, warehouses. Companies began to realize that, instead of higher inventories in several smaller distribution centers spread throughout the country, it was more efficient to centralize inventories and to ship to various outlets, from fewer distribution centers. Faster, and reliable transportation systems made this possible.

Automation in Control: 

The other major area of growth that began during the 1980s was real time warehouse control systems (RTWCS). The computer revolution began to permit massive, centralized computer systems to be broken up and decentralized. Decentralized computing set the stage for control automation in the warehouse.

Control automation blends material handling automation, automatic data collection, and human resources to achieve Computer Integrated Warehousing (CIW). Warehouse staff are linked to the computer via Radio Frequency Data Terminals (RFDT). RFDTs are typically equipped with hand held laser scanners. These systems are referred to as Real Time Warehouse Control Systems (RTWCS). Records are automatically and immediately updated when material is received, put-away, picked, and shipped.
An RTWCS monitors request to put-away, move and pick material. The requests are loaded into a work queue, which prioritizes them, identifies available resources and then dispatches the best available resource. Warehouse staff and material handling automation components receive direction from the RTWCS.

In many ways, the RTWCS becomes the director of all warehouse activities. For example, if there are no pending work requests, the RTWCS may dispatch a person in the warehouse to perform cycle counting. The result is that resource utilization is increased on all fronts – labour, space, equipment and inventory.
As more accurate and timely information is provided, warehouse management is improved. A warehouse manager can obtain the current status of any order, storage location, inventory level, equipment activity, or labour utilization demand. Material tracking is so precise that it is possible to determine for a designated part vein how many are presently picked and still traveling with an order picker. Inventory accuracies of greater than 99% are achievable.

Future Trend: 

The future, in the U.S. appears to be a continuation of the 1980’s. In fact, the trend is toward greater centralization of distribution warehouses as layers of distribution will be eliminated and the pull for the goods will be directly from the central warehouse to the consumer of the finished goods. This trend will require centralized warehouses to perform more small picks, i.e., more single case and individual part picks. In fact, the second greatest area of growth in warehouses automation over the next decade will be in order picking. The automated order picking systems of the future will not be labour Intensive but will have greater responsiveness, will be more flexible and will be more modular than systems today. In support of this higher throughput order picking environment, conveyor systems will play an even more significant role in warehousing than in the past.

The greatest area of growth will be in Real Time Warehouse Control Systems (RTWCS). The reduced costs of warehouse control systems will place these systems well within reach of warehouses who in the past could not afford warehouse automation. The reduced costs and increased performance of warehouse control systems will result in automated warehouse control systems with traditional material handling equipment being a superior alternative to AS/RS.

Lesson for Indian Companies: 

The lesson to Indian companies should be that automation has, and will, continue to be a significant part of warehousing. Companies, worldwide, have achieved significant operational efficiencies by adopting the right technologies. The economic liberalization In India has heralded a phase of unprecedented growth and possibilities in manufacturing. The one area that can no longer be ignored by Indian companies is warehousing, when modernization plans are drawn up.

The proper way to approach automation in warehousing is not by asking, “Is automation right for me”? Rather the questions should be “What is the correct level of automation”? “How is it justified”?, and “How will automation be phased in”? The introduction of automation in warehousing should be a foregone conclusion. The approach and technology best suited for an individual company will depend on their requirements. This will require an appropriate level of planning for warehouse automation.

The correct approach to plan for warehouse automation is to develop a Warehouse Strategic Master Plan (WSMP). The WSMP provides the future direction for the warehouse over a five or ten-year period. It addresses the facilities, staffing, equipment, inventory, and throughout required to meet the corporate business plan. The role of warehouse automation is a significant portion of a WSMP. The automation plan should be regarded as one component of a broader view and not a separate end unto itself.

Developing a WSMP is a methodical, five-step process:

1. Conduct Operational Assessment: The first step is to understand the present status of warehouse operations. Data should be collected on the following:

Customer Service Layout Control Systems Equipment Methods Inventory Accuracy Equipment Utilization Space Utilization Building Facilities Labour Productivity Housekeeping and Safety Warehouse strengths and weaknesses should be identified.

2. Define Future Requirements: Once the present operation has been analyzed, future warehouse requirements should be determined. This can be accomplished by examining a business forecast. A five-year projection is needed to answer the following questions:

• How will order volumes change?
• Will inventory levels change?
• Will inventory turn rates change?
• What new types of material will be present?

3. Develop Alternatives: Once present warehouse weaknesses and future requirements are known, various approaches to warehouse automation can now be considered and budget investment and operation costs can be developed. Potential savings in space and labour should be determined.

4. Evaluate Alternatives: For each alternative, an economic analysis should be performed. In addition, a qualitative analysis should be performed to consider issues, such as safety and ergonomics, that cannot be expressed in economic terms. The method of warehouse automation that is best suited to the particular operation and that is most justifiable can then be selected.

5. Document the WSMP: A written description of the WSMP. including alternative analysis, should be developed. The document should cover facility layouts, specify staffing levels, and detail equipment and system descriptions. Once written, it can be presented to senior management to obtain funding and support.

Using the WSMP approach provides a systematic method of properly confronting warehouse automation. The process provides clear direction as to the degree and type of automation to implement for any specific application. As the pace of warehousing quickens and customers demand better service, those who take a systems approach to warehousing and warehousing automation will be the ones best prepared to meet the challenges of the future.