The types of storage equipment utilized within the warehouse for pick operations will vary substantially depending on the type of and size of product, the throughput envisaged and available capital.
Floor/Bulk Storage
In situations where capital is at premium and goods are of low value with very few SKUs, the use of floor area for storage and picking is totally acceptable. The disadvantages however are the low utilization of the cubic capacity of the building and the inability to replace picked pallets without compromising the FIFO rule.
Standard and narrow aisle packet
Standard and narrow aisle adjustable pallet racking is used for providing ground-floor pick locations and reserve storage for full carton picks. The racking can also be used with high-level order picking trucks if there are insufficient ground-floor picking locations.
Very narrow aisle pallet racking
This racking is utilized for the storage of reserve pallets. The use of automatic cranes in this area precludes the picking of individual cartons. Full-pallet, single-SKU picks are however undertaken.
Carton flow racking
Carton live storage operates by means of gravity-fed rollers on adjustable shelving. Cartons are loaded at the upper end of sloping lanes, and move down under the force of gravity when a carton is removed from the picking face. The rollers can be adjusted to take different sizes of cartons and can also be fitted with a braking system to protect the more fragile items. LIFO can be used over FIFO here.
Shelving
Shelving is used to store less than pallet quantities of product. The items can be stored in their original cartons or in totes or bins. There are many different types of shelving, most of which are adjustable with different widths and heights. Bin or tote storage makes it possible to present a large variety of small components on a very compact face. These bins or containers are of different sizes, colors and shapes, and most have semi-open fronts.
Static shelving is reasonably inexpensive. The hidden cost is the cost of labor: the amount of time operators spend picking and restocking. By using gravity-flow shelving, pickers are a lot more productive.
Gravity-flow shelving costs less by labor cost savings, reduces travel time locating and replenishing products, uses floor more efficiently. Fewer aisles are required and more products can be stored in the same amount of floor space.
Horizontal carousels
Horizontal carousels work on a similar principle to a merry-go-round. The carousel can be made up of shelves, bins or garment holders. These rotate and are controlled by an operator who uses a computer keypad to type in the location, product code or order number, depending on how the software has been set up. If an order number is keyed in, the carousel will stop at the operator station in pick sequence.
An operator may look after more than one carousel in order to limit the amount of down time waiting for each carousel to rotate. Goods-to-operator systems are designed to keep the operator working as much as possible and reduce the amount of travel time. Horizontal carousels vary mainly in length depending on the nature of the product to be stored. They can also range in height from 2 to 8 metres, necessitating the use of a platform to access the product.
Horizontal carousels are ideal for storing and picking individual items, medium to large cartons and products including hanging garments. They are especially effective in low-headroom areas. Horizontal carousels are expensive and are limited by the amount of time they take to rotate. Cubic space utilization can also be an issue, as can safety if the carousel is not enclosed.
Vertical carousels and lifts
Vertical carousels have shelves that rotate in either direction similar to a Ferris or big wheel at a fun fair, bringing a requested item to the operator at a suitable working height. They allow you to use the maximum height available within the building, providing the best use of space within a very small footprint. They are ideal for small- to medium-size parts and takes up a much smaller footprint than a horizontal carousel. The shelving can be adjusted to handle different sizes and weights. They provide added security.
However, their effectiveness is tempered by the speed of movement. Here the trade-off is between the height of the system and therefore its greater storage capacity and the length of time it takes the shelves to rotate. Some carousels will operate with a lift system as opposed to rotating shelves. These can handle heavier items. The software provided with vertical carousels can manage the stock within the carousel, pick in sequence, work with pick-to-light systems and provide accurate reporting. The system can also work with scanners to confirm the correct item is picked every time.
A-frames
These machines are similar to vending machines but on a much bigger scale. They are ideal for high-volume items of uniform size and weight. This sorting and picking equipment operates most efficiently in an environment where these two characteristics are present. Typical products include CDs, DVDs, cosmetics and pharmaceuticals. The products are placed in magazines on a frame resembling a letter A and are automatically dispensed into a tote or directly onto the conveyor as it passes through the tunnel created by the frame. Orders are transported via conveyor to another picking area if incomplete or to the packing area. While the machine is operating, manual replenishment activities can be performed with no impact on the dispensing operations.
A-frame systems are capable of filling orders quickly: up to 750,000 units per day, depending on capacity and the replenishment capability. They can be highly accurate, with operations recording over 99.95 per cent. However, this system does require manual replenishment and inaccuracies can occur when filling the channels.
