A long section of metered belt conveyor runs though the center of the "fast pick" area with flow rack along both sides of the belt. Pick to light terminals are installed on the facings of all flow rack slots and each picker has a "pick zone" of about 12-16 feet and about 80 pick slots. The products in the whole pick area are the highest moving current catalog cosmetics items. Multiple slots are duplicated along the line for the highest moving items so that the high movers can be used to balance pick density among the various picker zones.
Cartons are released on to the conveyor, one at a time, using a feed belt to space the cartons at predetermined distances based on the number of picks for the carton. Widely spaced cartons indicate more picks and narrow spaced cartons indicate fewer picks. This helps level the pick density on the line. When a carton travels into a new pick zone, picks will light up for the pickers on either side of the belt. If a picker is working on a previous carton, the new picks will not be displayed until the previous order is completed. If the carton starts to leave the pick area without completion of all picks, the belt will stop (for the whole pick line) and alarm and blinking light will sound to call attention to the zone causing the stoppage. If a picker is obviously getting behind, his mate from the previous or following zone can help him catch up by sharing a few picks from the current order.
Paced picking results in considerable pressure to perform at high
levels to prevent being singled out for causing the belt to stop. It is
much like an assembly line in this respect. It is successful enough that
Mary Kay has used it at all five of its distribution locations.
Allen Bradley sells large numbers of specialized switches and industrial components for their industrial controller product lines. These small components are often bought as replacements for damaged or worn out parts and the total order is frequently quite small. For their new "technology demonstration center" they needed a way to pick these components out of high volume flow rack without being overwhelmed with hundreds of barely filled totes on their conveyor system.
In "cluster picking", standard plastic toes are fitted with removable, adjustable egg crate dividers to spilt a tote into up to 8 smaller compartments. The tote is identified to the system by its permanent "license plate" barcode ID. Depending on the number of compartments in the specific tote, each internal location is given a logical (not printed) letter ID from "A" to as many as "H" depending on the crate configuration. The "letter" compartment locations are determined by counting in alphabetic order clockwise from the top left corner following around the crate pattern.
When a crated tote diverts into a pick zone, its license plate ID number is displayed in the pick zone controller and all the picks for the current tote are displayed on the individual pick-to-light terminals. Each terminal indicates both the quantity to be picked and the crate location where it is to be placed. A pick of 6 pcs into the "C" compartment would be displayed as "C 6". When all picks for all compartments in the current zone are complete, the tote is returned to the conveyer belt and it proceeds to be diverted at the next zone where additional picks for any compartment are required. This system has proved very beneficial for picking large numbers of small orders from both flow rack and carousel based pick-to-light systems without overwhelming the conveyor system
In both of these installations the companies had a range of pick zones (12-30 in number) each of which was joined to the others by a long conveyor loop. Orders were started on the conveyor (in totes with a "license plate" bar code, some of which also contained the cardboard shipping carton) and then diverted at the first pick zone that required a pick for the tote. When the tote diverted into the zone it would join a small queue of totes waiting for its turn at picking. When the tote currently being picked was completed, the next tote’s license plate number would be displayed on the zone’s "tote ID" display and all of the picks for the new tote would be displayed at their pick slots.
It was typical of these installations that 100 to 600 pick slots would be under pick-to-light control in a zone. The number of pick slots in a zone was based on the movement of the items. If the zone had "high movers", then here would only be about 100 slots and they would all be in 10-12 foot deep flow rack. If the zone had "slow movers", then there would be many hundreds of slots extending on a network of aisles away from the divert point. The slow movers might be in 5-foot deep flow rack or in regular bin shelving with 20 or more items per bin unit.
In both cases, the companies used extra employees to shift from zone to zone if a back up of totes should occur. In the German operation, these workers were called "springers" as they would leap to where they were most needed. In some cases, two pickers could be assigned to a large zone, one making the distant picks and the other picking near the tote location. Also totes could be removed from the conveyor and pushed on a small cart around the pick area to collect multiple item picks. When the last lit terminal was extinguished, the tote was returned to the main conveyor loop to go to the next pick zone or to packing and shipping.
Factors that are unusual in these two applications and worthy of special interest are:
"Springers" can move between zones as needed