Chapter 8Small Item Picking Systems

《 《 Main KnowledgeMain Knowledge 》》

1. bin shelving systems

2. modular Storage Drawers/Cabinets

3. mezzanine

4. horizontal carousels

5. vertical carousels

6. automated item picking

Small Item Picking Systems

The major types of broken case picking systems are

picker-to-stock （ PTS ） system 拣选员移动式拣选系统

automated item picking 自动拣选系统

stock-to-picker （ STP ） system 存货移动式拣选系统

Small Item Picking Systems

In picker-to-stock systems, the order picker walks or rides to the picking location.

In stock-to-picker systems, the stock is mechanically transported to a stationary order picker.

In automated item picking, items are automatically dispensed into shipping cartons or tote pans.

the item retrieval system 取货系统

the storage system that houses the stock 货物存放系统

The two subsystems thatThe two subsystems thatmust be selected aremust be selected are

1. Picker-to-Stock Systems 拣选员移动式拣选系统

bin shelving 箱式货架

modular storage drawers 标准储存抽屉

gravity flow rack 重力式货架 / 自流式货架

The three most popular The three most popular picker-to-stock storage picker-to-stock storage systems aresystems are

1. Picker-to-Stock Systems 拣选员移动式拣选系统

Bin (or metal) shelving systems are the oldest and still the most popular equipment alternative for small parts order picking.

1.1.1 Bin Shelving Systems

1.1.1 Bin Shelving Systems

Advantages

Inexpensiverequire very little if any maintenance

Inflated labor requirementSupervisory problemsItem security/protection problems

Disadvantages

Disadvantages

Reasons are◇ the full inside dimensions of a shelving unit are rarely usable.◇ The height of bin shelving units may be limited by the reaching height of a human being.consequences are ◇ First, low space utilization means that a large amount of floor space is required to store the products.◇ Second, the greater the floor space, the greater the area that must be traveled by the order pickers, and thus the greater the labor requirement and costs.

Space is frequently underutilized in bin shelving systems.

1.1.1 Bin Shelving Systems

1.1.2 Modular storage drawers / cabinets

Advantages1. the large number of items that can 1. the large number of items that can be stored and presented to the be stored and presented to the order order picker in a small area. picker in a small area.2. excellent storage density2. excellent storage density3. because the drawers are pulled out 3. because the drawers are pulled out into the aisle for picking, space does into the aisle for picking, space does

not have to be provided above each not have to be provided above each SKU to provide room for the order SKU to provide room for the order picker’s hand and forearm. picker’s hand and forearm.4. improved picking accuracy4. improved picking accuracy5. protection for the items from the 5. protection for the items from the environment. environment. Suitable for:

When the value of space is at a true premiumWhen the value of space is at a true premiumWhen facing the possibility of building When facing the possibility of building additionsadditionsCost of space and the need for item security Cost of space and the need for item security and protection are very highand protection are very high

Gravity flow rack is typically used for :SKUs with high broken case cube movements

that are stored in fairly uniform sized and shaped cartons.

1.1.3 Gravity Flow Rack

1.1.3 Gravity Flow Rack

good space utilization.

very low maintenance requirements

Walking and therefore labor requirements can be reduced with an efficient layout.

Advantages

The back-to-front movement insures first-in-first-out （ FIFO ） turnover of the material.

The advantages of using a mezzanine is that nearly twice as much material can be stored in the original square footage. The major design issues for a mezzanine are the selection of the proper grade of mezzanine for the loading that will be experienced, the design of the material handling system to service the upper levels of the mezzanine, and the utilization of the available clear height.

11Mezzanines

1.1.4 Space Saving Systems

The key to maintaining high-order picking productivity when a mezzanine is in use is to slot the products so that most of the picking activity takes place at the floor level.The SKUs with the highest picking density should be assigned to the floor level and the SKUs with the lowest picking density should be assigned to the upper level.

11Mezzanines

1.1.4 Space Saving Systems

22Mobile Storage

Systems

1.1.4 Space Saving Systems

1.1.4 Space Saving Systems

22Mobile Storage

Systems

DisadvantageDisadvantage

the increased time required to access the items.

used forused for

very slow-moving items and when space is very scarce and/or expensive.

space savings

AdvantageAdvantage

1.2 Picker-to-stock retrieval methods 拣选员移动式取货方法

Cart Picking 手推车拣选

Tote （ or Carton ） Picking 拣货箱拣选

Man-up Systems 载人系统

Robotic Item Picking 机器人拣选

11Cart Picking

手推车拣选

Batch picking carts are designed to enable an order picker to pick multiple orders on a picking tour, thus dramatically improving productivity as opposed to strict single-order picking for small order.

Cart picking rates range from 70 to 120 lines per person- hour.

1.2 Picker-to-stock retrieval methods

22Tote (or Carton) P

icking拣货箱拣选

Tote picking rates range from 150 to 300 lines per person hour.

Conveyors are used

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 more orders on each pass through the picking zones.

1.2 Picker-to-stock retrieval methods

33Man-up Systems

载人系统

Order picker truck;man-aboard AS/RS 载人自动存取系统

A man-aboard AS/RS offers significant floor space savings over the systems described so far.

Advantage

Man-aboard automated storage and retrieval systems are far and away the most expensive picker-to-stock equipment alternative.

Disadvantage

1.2 Picker-to-stock retrieval methods

33Man-up Systems

载人系统

44Robotic Item Pick

ing机器人拣选

1.2 Picker-to-stock retrieval methods

Typical picking rates in man-aboard operations range between 40 and 250 lines per person-hour.

Man-aboard systems are typically appropriate for slow-moving items where space is fairly expensive.

2. STOCK-TO-PICKER SYSTEMS

Carousels 旋转式存储传送系统

Manila Automated Storage and Retrieval Systems

轻负载自动存取系统

The two most popular stock-The two most popular stock-to-picker storage systems to-picker storage systems are are

The major The major advantageadvantage of of stock-to-picker systems over stock-to-picker systems over picker-to-stock systemspicker-to-stock systems

The elimination of the travel time for the order picker

supervision

2. STOCK-TO-PICKER SYSTEMS

2.1 Carousels

Horizontal carousels

vary in length from 15

feet to 100 feet, and in height from 6 feet to

25 feet. The length and height of the units are dictated by the pick rate requirements and building restrictions.

Horizontal carousels水平旋转式存储传送系统11

2.1 Carousels

Horizontal carousels水平旋转式存储传送系统11

The throughput capacity is limited by the rotation speed of the motor drive.The initial investment of $40,000 to $70,000 per carousel unit.

Drawback

Items with a high cube movement should not be housed in carousels.

Suitable for

2.1 Carousels

22 Vertical Carousels 垂直旋转式存储传送系统

Vertical carousels range in height from 8 feet to 35 feet. Heights are dictated by throughput requirements and building restrictions.

2.1 Carousels

The cost of a typical vertical carousel is around $100,000> Horizontal carousels

22 Vertical Carousels 垂直旋转式存储传送系统Advantages

1. Order pick times for vertical carousels are theoretically less than those for horizontal carousels 2. promotes more accurate picking

3. excellent item protection and security.

Miniloads vary inheight from 8 to 50feet, and in length from 40 to 200 feet. As in the case with carousels, the heightand length of the system are dictated by the throughput requirements.

2.2 Miniload Automated Storage and Retrieval Systems

2

1

2

1

2.2 Miniload Automated Storage and Retrieval Systems

As the most sophisticated of the system al

ternatives described thus far, is should com

e as no surprise that the miniload carries th

e highest price tag of any of the order picki

ng system alternatives. Another result of its

sophistication is the significant engineering

and design time that accompanies each sys

tem.Greater sophistication leads to greater

maintenance requirements.

3. Automated Item Dispensing Machines

Typical picking rates are in the range Typical picking rates are in the range of 1,500 to 2,000 picks per person-of 1,500 to 2,000 picks per person-hour.hour.Typical picking accuracy is 99.97 percent.Typical picking accuracy is 99.97 percent.

4. Broken case picking systems comparison and selection

Summary Characteristics of Alternative Broken Case Picking SystemsSystem

AttributeUnit of Measure

Bin Shelving

Gravity Flow Racks

Storage Drawers

Horizontal Carousel

VerticalCarousel

Miniload AS/RS

Automatic Dispersing

Gross system cost

Initial cost/ purchased Ft3

$5-15 $3-5 $25-30 $20-35 $40-70 $30-40 $300-600 per dispenset

Net system cost

Initial cost/ available Ft3

#10-30 $9-15 %31-38 $40-70 $65-100 $38-50

Floorspace requirements

Ft3 of inventory houses per Ft2 of floorspace

1-1.2 0.7-0.85 1.8-2.5 0.8-1.25 5.0-6.0 4.0-5.0

Human factors

Ease of retrieval

Average Average Good Average Excellent

Excellent

Good

Maintenance requirements

Low Low Low Medium Medium High High

Item security

Average Average Excellent

Good Excellent

Excellent

Average

Flexibility Ease to reconfigure

High High High Medium Low Low Low

Pick rate Order lines per person-hour

C:25-125T:100-350M:25-250W:300-500

C:25-125T:100-350M:25-250W:300-500

C:25-125T:100-350M:25-250W:300-500

50-250 50-300 25-125 500-1000

T=Tote picking C=Cart picking M=Man-aboard ASRS W=Wave picking