BROKEN CASE PICKING SYSTEMS

C H A P T E R S E V E N

RIGHTSTORE PIECES: PIECE PICKING PRINCIPLES, SYSTEMS, AND BEST PRACTICES 7.1 Picker-to-Stock Systems 7.2 Stock-to-Picker Systems 7.3 Automated Item Dispensing Machines 7.4 Broken-Case Picking Systems Comparison and Selection

Our RightHouse taxonomy of broken-case picking systems begins by dividing the systems into picker-to-stock (PTS) systems, stock-to-picker (STP) systems, and automated item picking (Figure 7.1). In PTS systems, the order picker walks or rides to the picking location. In STP systems, the stock is mechanically transported (via carousel, automated storage and retrieval system, or AGVS) to a stationary order picker. In automated item picking, items are automatically dispensed into shipping cartons or tote pans. This chapter describes the pros, cons, applications, and associated costs of each of these major system types. As in earlier chapters, we will move through the system descriptions in order of increasing cost, complex ity, and degree of automation. The chapter concludes with a description of the techniques for choosing from among the many equipment options for small-item picking systems.

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Figure 7.1 RightHouse taxonomy of broken-case picking systems

Broken Case Picking Systems

Automated Dispensing Systems

Picker to Stock Systems

Stock to Picker Systems

Automated Storage & Retrieval Systems

Picker to Stock Retrieval Systems

Automated Guided Shelving Systems

Picker to Stock Storage Systems

Carousels

Horizontal Carousels

Bin Shelving

Picking Carts

Storage Drawers

Vertical Carousels

Stock Pickers

Carton Flow Rack

Pickers Man Aboard ASRS

Robotic Item Pickers

7.1 Picker-to-Stock Systems

In PTS systems, the order picker walks or rides to the picking location. The two subsystems that must be selected are (1) the storage system that houses the stock and (2) the item-retrieval system. PTS Storage Systems The three PTS storage systems are bin shelving, modular storage drawers, and gravity-flow racks. Bin Shelving Systems Bin shelving systems (Figures 7.2 and 7.3) are the oldest and still most popular (in terms of dollar sales volume and number of systems in use) equipment alternative for small-parts order picking. Bin shelving systems are inexpensive, easily reconfigured, and requireminimal maintenance.

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Figure 7.2 Typical bin shelving system

Figure 7.3 Bin shelving system with corrugated inserts for small-parts picking (Caterpillar,Atlanta, GA)

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Unfortunately, the lowest initial-cost alternative may not be the most cost-effective alternative or the alternative that meets the prioritized needs of a warehouse. With bin shelving systems, savings in initial cost and main tenance may be offset by inflated floor space, excessive labor requirements, and/or inadequate item protection. Space is frequently underutilized in bin shelving systems because the full inside dimensions of a shelving unit are rarely usable. Also, the height of bin shelving units may be limited by the order picker’s reaching height. As a result, the available building cube alsomay be underutilized (Figures 7.4 through 7.6). There are two consequences of the low storage space utilization. First, a large amount of floorspace is required to store the products. The more expensive it is to own and operate the space, the more expensive low space utilization becomes. Second, the greater the floorspace, the greater the area which must be traveled by the order pickers, and thus, the greater the labor requirement and costs. Two additional drawbacks of bin shelving are supervisory problems and item security/protection problems. Supervisory problems arise because it is difficult to supervise people through a maze of bin shelving units spread

Figure 7.4 Bin shelving with pick density storage and pick-to-light for video game picking in a large toy retailer’s distribution center (Happinet, Tokyo, Japan)

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Figure 7.5 Bin shelving with plastic inserts on a small-service-parts picking mezzanine (Honda,Atlanta, GA)

Figure 7.6 Bin shelving layout

out over a large area. Item security/protection problems arise because bin shelving is open; that is, all the items are exposed to and accessible from the picking aisles for any operator and/or visitor. To improve building cube and/or footprint utilization, bin shelving may be mezzanined or mobilized (Figures 7.7 and 7.8).

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Figure 7.7 Bin shelving mezzanine at Xerox’s Chicago service parts distribution center

Figure 7.8 Mobile bin shelving system at LAM Research’s San Francisco service center

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Modular Storage Drawers/Cabinets Modular storage drawers/cabinets (Figures 7.9 through 7.13) are called modular because each storage cabinet houses modular storage drawers that are subdivided into modular storage compartments. Drawer heights range from 3 to 24 inches, and each drawer may hold up to 400 pounds of material. The primary advantage of storage drawers/cabinets over bin shelving is the large number of stock-keeping units (SKUs) that can be stored and presented to the order picker in a small footprint. A single drawer can hold from 1 to 100 SKUs (depending on the size, shape, and inventory levels of the items), and a typical storage cabinet can store the equivalent of two to four shelving units of material. The excellent storage density accrues from the ability to create item housing configurations within a drawer/cabinet that very closely match the cubic storage requirements of each SKU. Also, because the drawers are pulled out into the aisle for picking, space does not have to be provided above each SKU to allow room for the order picker’s hand and forearm. This reach space must be provided in bin shelving stor age; otherwise, items deep in the unit could not be accessed. By housing more material in less floor space, the overall space require ment for storage drawers is substantially less than that required for bin Figure 7.9 Storage drawers in an automotive plant storage crib with a person-aboard ASRS

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Figure 7.10 Modular storage drawer configuration for military parts deployment (US Army, Savannah, GA)

Figure 7.11 Typical storage drawer configuration (Lista)

shelving. When the value of space is at a true premium, such as on a manu facturing floor, in an assembly area, or in an airport, or when facing the possibility of building additions, the reduction in space requirements alone can be enough to justify the use of storage drawers and cabinets. Additional benefits achieved by the use of storage drawers include improved picking accuracy and protection for the items fromthe environment.

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Figure 7.12 Typical storage drawer installation for maintenance parts

Figure 7.13 Storage drawers for mining maintenance parts (RioTinto, Salt Lake City, UT)

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Picking accuracy is improved over that in shelving units because the order picker’s sight lines to the items are improved, and the quantity of light fall ing on the items to be extracted is increased. With bin shelving, the physical extraction of items may occur anywhere from floor level to 7 feet off the ground, with the order picker having to reach into the shelving unit itself to achieve the pick. With storage drawers, the drawer is pulled out into the pick ing aisle for item extraction. The order picker looks down onto the contents of the drawer, which are illuminated by the light source for the picking aisle. (The fact that the order picker must look down on the drawer necessitates that storage cabinets be less than 5 feet tall.) Excellent item security and protection are achieved because the drawers can be closed and locked when not in use. Storage cabinets equipped with drawers range in price from $1,000 to $3,000 per unit. Price is primarily a function of the number of drawers and the amount of sheet metal in the cabinet. Because the cost per cubic foot of storage is so high, storage drawers are justifiable only for items with very little on-hand cubic inventory (typically less than 0.5 cubic feet) and for operating scenarios in which the cost of space and the need for item security and protection are very high (Figures 7.6 through 7.13). As was the case with bin shelving, storage drawer systems may be mez zanined or mobilized (Figure 7.14).

Figure 7.14 Storage drawer cabinets in a mezzanine system

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Carton Flow Rack Gravity-flow racks (Figures 7.15 through 7.18) are typically used for SKUs with a high broken-case cube movement stored in fairly uniformly sized and shaped cartons. Cartons are placed at the back of the rack from the replenishment aisle and advance/roll toward the pick face as cartons are depleted from the front. The back-to-front movement ensures first in, first out (FIFO) turnover of the material. In essence, a section of flow rack is a bin shelving unit turned perpen dicular to the picking aisle with rollers placed on the shelves. The deeper the sections, the greater is the portion of warehouse space that will be devoted to storage as opposed to aisle space. Further gains in space and labor efficiency can be achieved by making use of the cubic space over the flow rack for full-pallet storage of reserve quantities of the items located below. As is the case with bin shelving, flow racks have very low maintenance requirements and are available in a wide variety of standard section and lane sizes from a number of suppliers. The fact that just one carton of each line item is located on the pick face means that a large number of SKUs are presented to pickers along the pick line. Hence, walking and therefore labor requirements can be reduced with

Figure 7.15 Gravity-flow-rack picking operation

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Figure 7.16 Carton flow-rack picking line at NTT’sTokyo logistics center

Figure 7.17 Flow-rack shoe picking at Nike’s European Union distribution center outside Amsterdam

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Figure 7.18 Carton flow-rack pick-to-light (Happinet,Tokyo, Japan)

an efficient layout (Figures 7.19 through 7.22). (To make sure that the space behind the front carton is properly utilized, only SKUs with two or more cartons on hand should be assigned to positions in gravity-flow racks.)

Figure 7.19 Carton flow rack in a U-shaped picking module with pick-to-light and put-to-light (Avon,Atlanta, GA)

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Figure 7.20 Carton flow rack simulation Avon

Figure 7.21 Carton flow-rack bays (L.L. Bean, Portland, ME)

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Figure 7.22 Mezzanine picking operation atVerizon Logistics East Coast distribution center

Picker-to-Stock Retrieval Methods PTS retrieval methods include cart picking, tote picking, person-aboard systems, and robotic item picking. The pros, cons, and applications of each are described next. Cart Picking A wide variety of picking-cart types (Figures 7.23 through 7.34) are available to facilitate accumulating, sorting, documenting, and/or packing orders as an order picker makes a picking tour. Conventional carts provide dividers for order sorting, a place to hold paperwork and marking instruments, and a stepladder for picking at levels slightly above reaching height. Batch picking carts are designed to allow an order picker to pick multiple orders on a picking tour, thus dramatically improving productivity as opposed to strict single-order picking for small orders. More sophisticated carts automatically transport an order picker to a pick location, use light

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Figure 7.23 Batching picking cart with one tote per dealer order (Honda, Troy, NY)

Figure 7.24 Batch picking cart for health and beauty aids (Avon,Atlanta, GA)

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Figure 7.25 Batch picking cart for service parts equipped with onboard computing and packaging (Caterpillar,Atlanta, GA)

Figure 7.26 Pick face pick pack cart for service parts and hardware (U.S. Defense Logistics Agency, Philadelphia)

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Figure 7.27 Monorail picking cart in a large book distribution center (Bertelsman, Gutersloh, Germany)

Figure 7.28 Batching picking cart equipped with onboard scales, onboard labeling, and onboard computing. (Shinwa, Osaka, Japan)

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Figure 7.29 Pick-to-light batch picking cart (Shiseido,Tokyo)

Figure 7.30 Batch wave picking carts (L.L. Bean, Portland, ME)

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Figure 7.31 Batch picking cart (L.L. Bean, Portland, ME)

displays to direct the order picker to sort the contents of a pick into the correct order positions, and permit mobile online communication via radiofrequency (RF) links and/or wireless local area network (LAN) links.

Figure 7.32 Batch wave picking cart dumping contents into tilt-tray sorter

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Figure 7.33 Light picking cart (Shisheido,Tokyo)

Figure 7.34 Automated guided vehicle (AGV) picking cart (Creform)

Tote (or Carton) Picking In tote picking systems (Figure 7.35), conveyors are used to transport tote pans (or shipping cartons) through successive picking zones to allow order completion. The tote pans are used to establish order integrity, for merchandise accumulation and containment, and/or for shipping. Order pickers may walk one or more totes through a single picking zone, partially completing several orders at a time, or an order picker may walk one or more totes through all picking zones, thus completing one or

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Figure 7.35 Tote picking system

more orders on each pass through the picking zones. Tote picking rates range from 150 to 300 lines per person-hour. The improvement over cart picking must be sufficient to justify the additional investment in conveying and sorting systems. Person-up Systems In the systems described thus far, the operator remains at floor level. To improve the utilization of building cube and floor space, order pickers can ride up on an order-picker truck or a person-aboard ASRS machine to locations as high as 40 to 50 feet (Figures 7.36 through 7.39). The operation of order-picker trucks was explained in Chapter 6. The operation of a person-aboard ASRSs is described next. A person-aboard ASRS (Figure 7.40), as the name implies, is an automated storage and retrieval system in which the picker rides aboard a storage/retrieval machine to the pick locations. The storage locations may be provided by stacked-bin shelving units, stacked storage cabinets, and/or pallet racks. The storage/retrieval machine may be aisle captive or free roaming. Typically, the order picker leaves from the front of the system at floor level and visits enough storage locations to fill one or multiple orders

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Figure 7.36 Stock picker truck

Figure 7.37 Stock picker truck

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Figure 7.38 An order picker headed for a batching picking run of slow-moving items in high-bay storage at L.L. Bean’s Portland, Maine, distribution center

Figure 7.39 High-bay picking area for slow-moving items at L.L. Bean’s Portland, Maine, distribution center

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Figure 7.40 Person-aboard ASRS picking operation

depending on order size. The order picker can sort on board if enough containers are provided on the storage/retrieval machine. A person-aboard ASRS offers significant floor space savings over the systems described so far. The floor space savings are available because the storage system heights are no longer limited by the reach height of the order picker. Shelves or storage cabinets can be stacked as high as floor loading, weight capacity, throughput requirements, and/or ceiling heights permit. The key to achieving good picking productivity is intelligent slotting and pick tour sequencing. If there are 10 or fewer picks per aisle traversal, then the objective is to keep most of the picks at or near floor level. If there are more than 10 picks per aisle traversal, the operator most likely should be sequenced to make a sweep of the upper and lower levels of the aisle. In this case, bands of fast-moving items should be located in the upper and lower levels. The operator should traverse along the lower band on the way out from the input-output point and along the upper band on the way back to the input-output point.

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Person-aboard ASRSs are far and away the most expensive PTS equipment alternative. Hence there must be enough storage density and/or productivity improvement over cart and tote picking to justify the invest ment. Also, because vertical travel is slower than horizontal travel, typical picking rates in person-aboard operations range between 40 and 250 lines per person-hour. The range is large because there are a large number of oper ating schemes for person-aboard systems. Person-aboard systems typically are appropriate for slow-moving items where space is fairly expensive. Robotic Item Picking Robotic picking vehicles (Figures 7.41 and 7.42) travel automatically through a sequence of picking locations, receiving power and communication from rails in the floor and ceiling. The vehicles are equipped with a small carousel to permit order sorting, accumulation, and containment. The carousel travels up and down a mast on the robot as it traverses the picking aisle(s). The robot can automatically extract a storage drawer from a storage location onto the picking vehicle. The robot’s arm is guided by an onboard vision system to direct item picking from a specific storage compartment in a storage drawer. Only in rare instances are robotic item picking systems justifiable.

Figure 7.41 Robotic item picking

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Figure 7.42 Robotic item picking for single bottles of consumer products

7.2 Stock-to-Picker Systems

The three major types of STP systems are carousels, miniload ASRSs, and automated guided shelving systems. Each system type is described in the following subsections. The major advantage of STP systems over PTS sys tems is elimination of the travel time for the order picker. When wage rates are high, the labor savings can be sufficient to justify the investment in the mechanical and control systems required in STP systems. If a STP system is not designed properly, an order picker may remain idle waiting on the system to present the next picking transaction. In such cases, productivity actually can be worse than that found in PTS systems. Another advantage of STP systems is supervision. In STP systems, the picking takes place at the end of an aisle. Hence all the operators should be visible to a supervisor in one quick glance down a picking line. Carousels Carousels, as the name implies, are mechanical devices that house and rotate items for order picking. Horizontal and vertical carousels are popular for order picking applications.

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Horizontal Carousels A horizontal carousel (Figures 7.43 through 7.46) is a linked series of rotating bins of adjustable shelves driven on the top or the bottom by a drive-motor unit. Rotation is about an axis perpendicular to the floor at a rate of about 80 to 200 feet per minute.

Figure 7.43 Horizontal carousel system at Ford’s parts distribution center

Figure 7.44 Pick-by-light, put-to-light horizontal carousel picking (Swagelok, Cleveland, OH)

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Figure 7.45 Horizontal carousel system with automated outfeed and loop front end (Witt)

Figure 7.46 Horizontal carousel storage and retrieval system with robotic extractor for tote staging (Swagelok, Cleveland, OH)

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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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Figure 7.47 Rotary rack carousel (Murata,Tokyo, Japan)

Vertical Carousels A vertical carousel (Figures 7.48 through 7.50) is a horizontal carousel turned on its end and enclosed in sheet metal. As with horizontal carousels, an order picker operates one or multiple carousels. The carousels are indexed either automatically via computer control or manually by the order picker working a keypad on the carousel’s work surface.

Figure 7.48 Vertical carousel installation

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Figure 7.49 Vertical carousel picking at a large dental supply distribution center (Kent Dental, Philadelphia)

Vertical carousels range in height from 8 to 35 feet. Heights (as lengths were for horizontal carousels) are dictated by throughput requirements and building restrictions. The taller the system, the longer it will take, on average, to rotate the desired bin location to the pick station.

Figure 7.50 Vertical carousel (NASA, Cape Canaveral, FL)

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Order-pick times for vertical carousels are theoretically less than those for horizontal carousels. The decrease results from the fact that items are always presented at an order picker’s waist level. This eliminates the stoop ing and reaching that go on with horizontal carousels, further reducing search time, and promotes more accurate picking. (Some of the gains in item extract time are negated by the slower rotation speed of the vertical carousel. Recall that the direction of rotation is against gravity.) Additional benefits provided by vertical carousels include excellent item protection and security. In vertical carousels, only one shelf of items is exposed at a time, and the entire contents of the carousel can be locked up. Vertical carousels are much more expensive than horizontal carousels with cost increasing with the number of shelves, weight capacity, and special features. The additional cost of vertical over horizontal carousels is a result of the sheet-metal enclosure and the extra power required to rotate against the force of gravity. Miniload Automated Storage and Retrieval Systems In miniload ASRSs (Figures 7.51 through 7.57), an automated storage/ retrieval machine travels horizontally and vertically simultaneously in a storage aisle, transporting storage containers to and from an order picking station located at one end of the system. The order picking station typically has two pick positions. As the order picker is picking from the container in the left pick position, the storage/retrieval machine is taking the container from the right pick position back to its location in the rack and returning with the next container. The result is that an order picker alternately picks from the left and right pick positions. The sequence of containers to be processed can be determined manually (the order picker keying in the desired line-item numbers or rack locations on a keypad) or automatically by computer control. Miniload systems vary in height from 8 to 70 feet and in length from 40 to 300 feet. As is the case with carousels, the height and length of the system are dictated by the throughput requirements and building restrictions. The longer and taller

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Figure 7.51 Miniload ASRS (MackTrucks, Baltimore, MD)

the system, the longer is the time required to access the containers. How ever, the longer and taller the system, the fewer are the aisles and storage/ retrieval machines that will have to be purchased. At between $150,000 and $300,000 per aisle, determination of the correct system length, height, and number of aisles to meet the pick-rate, storage, and economic return requirements for the warehouse is critical (Figures 7.52 through 7.57).

Figure 7.52 Miniload ASRS front-end picking with a loop conveyor (Daifuku)

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Figure 7.53 Even miniload systems can be configured with mobile aisles, as is the case in this installation

Figure 7.54 Inside a miniload ASRS (NASA, Cape Canaveral, FL)

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Figure 7.55 Multi-shuttle miniload ASRS

The transaction-rate capacity of a miniload system is governed by the ability of the storage/retrieval system to continuously present the order picker with unprocessed storage containers. This ability, coupled with

Figure 7.56 Miniload ASRS for mining maintenance parts (RioTinto, Salt Lake City, UT)

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Figure 7.57 Goods to person (Opex)

the human factors benefits of presenting the containers to the picker at waist height in a well-lit area, can yield pick rates ranging between 40 and 200 picks per person-hour. Miniload floor space requirements are small because of the ability to store material up to 50 feet high, the ability to size and shape the storage containers and the subdivisions of those containers to very closely match the storage-volume requirements of each SKU, and an aisle width that need only accommodate the width of a storage container. Because this is the most sophisticated of the system alternatives described thus far, it should come as no surprise that the miniload system carries the highest price tag of any of the order picking system alternatives. Another result of its sophistication is the significant engineering and design time that accompanies each system. Most systems require between 6 and 18 months for design, delivery, and installation. Finally, greater sophistication leads to greater maintenance requirements. It is only through a disciplined maintenance program that miniload suppliers are able to advertise uptime percentages of between 97 and 99.5 percent.

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Figure 7.58 Automated guided shelving systems operating at an Amazon distribution center

Automated Guided Shelving Systems Automated guided shelving systems are small automated guided vehicles that transport bin shelving units to stationary order pickers (Figure 7.58).

7.3 Automated Item Dispensing Machines

Automated item dispensing systems (Figure 7.59 and 7.60) act much like vending machines for small items of uniform size and shape. Each item is allocated a vertical dispenser ranging from 2 to 6 inches wide and from 3 to 5 feet tall. (The width of each dispenser is easily adjusted to accommodate variable product sizes.) The dispensing mechanism acts to kick the unit of product at the bottom of the dispenser out onto a conveyor running between two rows of dispensers configured as an A-frame over a belt conveyor. A tiny vacuum conveyor or small finger on a chain conveyor is used to dispense the items. Virtual order windows begin at one end of the conveyor and pass by each dispenser. If an item is required in the order window, it is dispensed onto the conveyor. Merchandise is accumulated at the end of the belt con veyor into a tote pan or carton. A single dispenser can dispense at a rate of

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Figure 7.59 Item dispensing machine for English boots

Figure 7.60 Missing figure caption.

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up to 6 units per second. Automatic item pickers are popular in industries with high throughput for small items of uniform size and shape, such as cosmetics, wholesale drugs, compact discs, videos, publications, and poly bagged garments. Replenishment is performed manually from the back of the system. The manual replenishment operation significantly cuts into the potential savings in picking labor requirements. Nonetheless, typical picking rates are in the range of 1,500 to 2,000 picks per person-hour. Typical picking accuracy is 99.97 . As is the case with all the systems selections and justifications described so far, a picking-mode economic analysis should be conducted to assign each item to its most economically attractive storage mode. This analysis should consider the activity and inventory profile of each item and the storage and handling characteristics of each storage mode. The economic analysis should recommend the appropriate storage mode for each item based on matching each item’s requirements to a storage mode’s capabilities. Our RightStore Storage Mode Optimization automates this selection process. The optimization calculates the picking, restocking, space, equipment, and error costs for each item in each potential storage mode and assigns each SKU to its optimal storage mode and allocation of space (Table 7.1 and Figures 7.60 through 7.62). 7.4 Broken-Case Picking Systems Comparison and Selection

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500

600

200–

300–

300 20–100

100–

Picking Rates (lines/person hour)

500– 2000 N/A N/A N/A N/A

Method Ergono mics General Cart Tote ASRS Wave Bin shelving $5–10 $5–40 1.0–1.2 Low Low High Low 15–500 20–100 80–250 15–80 Carton flow rack $5–10 $15–30 0.7–0.9 Low Low High Low 20–600 2–125 Space Require ments Protection guration Flexibility

medium Medium Medium 50–250 N/A N/A N/A N/A Vertical carousels $50–100 $75–125 5.0–7.0 Medium Very high Low High 35–200 N/A N/A N/A N/A Miniload ASRS $75–125 $100–150 4.0–5.0 Very high Very high Low High 30–150 N/A N/A N/A N/A Automated dispensing $500–2000 per dispenser — — Very high Medium Low Medium

Storage drawers $30–50 $35–60 1.8–2.5 Low High High Medium 10–150 15–80 60–150 10–50 N/A Horizontal carousels $25–50 $50–100 0.8–1.3 Medium Low to

Reconfi

Security and

Item

Main

tenance

Inventory Housed per

Foot of Floor

Feet of

Square

Net

Available Cubit Foot

System Cost:

Initial

Cost per

Purchased Cubic Foot

System Cost:

Initial

Gross

Cost per

263 Table 7.1 Summary Characteristics of Alternative Broken-Case Picking Systems

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264 Figure 7.61 RightStore broken case picking storage mode optimization

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Figure 7.62 RightStore preference regions

265

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