BROKEN CASE PICKING SYSTEMS

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World-Class Warehousing and Material Handling

Items are extracted from the carousel by order pickers who occupy fixed positions in front of the carousel(s). Order pickers also may be responsible for controlling the rotation of the carousel. Manual control is achieved via a keypad that tells the carousel which bin location to rotate forward and a foot pedal that releases the carousel to rotate. Carousels are normally com puter controlled, in which case the sequence of pick locations is stored in a computer and brought forward automatically. The assignment of order pickers to carousels is flexible. If an order picker is assigned to one carousel unit, he or she must wait for the carousel to rotate to the correct location between picks. If an order picker is assigned to two or more carousels, he or she may pick from one carousel while the other is rotating to the next pick location. Remember, the objective of STP systems is to keep the picker picking. (Humans are excellent extractors of items; the flexibility of our limbs and muscles provides us with this capability. We are not efficient searchers, walkers, or waiters, however.) Horizontal carousels vary in length from 15 to 100 feet and in height from 6 to 25 feet. The length and height of a unit are dictated by the pick rate requirements and building restrictions. The longer the carousel, the more time is required, on average, to rotate the carousel to the desired loca tion. Also, the taller the carousel, the more time is required to access items. Heights over 6 feet require the use of ladders, lift platforms, or robotic arms on vertical masts to access items. One drawback of horizontal carousels is that the throughput capacity is limited by the rotation speed of the motor drive. Another drawback is the high initial investment per carousel unit. Consequently, items with high cube movement should not be housed in carousels because the carousel may not be able to rotate fast enough to permit sufficient access to those items and because those items would occupy a large and expensive envelope of space in the carousel. Rotary-Rack Carousels Rotary-rack carousels are like one-level carousels stacked on top of each other. They are often used for tote buffer staging (Figure 7.47).

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