Outline small item storage and retrieval system picking operations case study

Small Item Storage and Retrieval Systems

Picker-to-Stock Systems: Storage bin shelving modular storage gravity flow rack space saving system

Bin Shelving oldest method advantages simple low initial cost variable bin content over time

Bin Shelving disadvantages under utilization of space inside bins limited vertical space of columns of bins ill positioned picking height more space expensive difficult for personnel supervision security problem

Modular Storage Drawer/Cabinets a cabinet holds drawers with modular storage compartments especially suitable for sets of components (put in compartments of the same drawer) save space more human factors in storage and retrieval

Gravity Flow Rack SKUs fairly similar in shapes and size inclined rack, high at end loaded at back and unloaded in front back-end goods pulled to front by gravitational force FIFO usually for fast moving goods

Space Saving Systems mezzanines mobile storage unit high floor height use mezzanines for secondary storage mobile storage unit

Picker-to-Stock Systems: Retrieval cart picking tote picking man-up system robotic item picking

Cart Picking equipped with different peripherals paperwork station marking equipment ladder bar-code accessories: scanner, reader, data terminal automatic location directions light guiding system RF links compartments for sorting batch orders

Tote Picking picked items to totes totes on conveyors for pickers to carry or push them around compartments on totes for multiple orders

Man-up Systems man aboard an AS/RS system for picking full usage of height (e.g., 40 ft) in storage generally pick multiple orders important for slotting of storage area and sequencing of picks

Robotic Item Picking

Stock-to-Picker Systems carousel horizontal vertical miniload

Horizontal Carousel limited height a picker on multiple carousel

Vertical Carousel shorter pick time than horizontal carousel better picking position better item protection

Miniload Automated Storage and Retrieval System low floor space requirement manual or automatic storage and retrieval direction greater maintenance requirements

Automated Item Dispensing Machines automated vending machine with conveyor or pneumatic system to send selected items to the collection point

Summary Characteristics of Alternative Broken Case Picking Systems Auto. Disp. Miniload AS/RS Vertical Carousel Horiz. Carousel Storage Drawers Flow Racks Bin Shelving Gross Cost Net Cost Floor Space Reqt. Human Factors Mainten-ance Item Security Flexibility Pick Rate

Summary Characteristics of Alternative Broken Case Picking Systems Bin Shelving Flow Racks Storage Drawers Horiz. Carousel Vertical Carousel Miniload AS/RS Auto. Disp. Gross Cost Net Cost Floor Space Reqt. Human Factors Mainten-ance Item Security Flexibility Pick Rate

Chapter 8 Picking Operations

volume and weight of items in lines Picking Operations expensive: order picking (50%); shipping (15%); receiving (15%); storage (20%) nature of items setting constraints on batching or zoning of orders items Qty lines of items volume and weight of items in lines

Typical Distribution of an Order Picker’s Working Time 55% 20% 15% 10% Traveling Searching Extracting Other

Schemes of Picking Orders documentation, reaching, searching, extracting, counting, restocking do not change (much) with schemes of picking orders sequencing orders; un-grouping, grouping and regrouping lines traveling distance and sorting effort change with schemes of picking orders What is the best mode to pick in a given situation?

Schemes of Picking Picking Schemes Freeform Picking Zone Picking Single Order Picking Progressive Assembly Batch Picking Downstream Sortation Manual Sortation Split Single Order Picking Automated Sortation Complete Single Order Picking

Single-Order Picking good for long traveling distance for a few items order integrity “large” orders or emergency orders long traveling distance for a few items high distance traveled per line

Batch Picking picking multiple orders in a trip to reduce distance traveled per line need to sort item several compartments (in a pick cart) to differentiate lines of different orders group items and quantities during picking and sort later

Zone Picking a dedicated, non-overlapping zone to each picker pros reduced travel distance familiarization of locations and products minimal congestion clear accountability minimal socialization cons extra effort in order assembly workload imbalance

Methods to Assemble Orders zone 1 zone 2 zone 3 progressive order assemble downstream sortation zone 1 zone 2 zone 3 sort-ing

Improvement of Picking Operations issue pack optimization pick from storage pick task simplification order batching slotting optimization pick sequencing

Issue Pack Optimization reduce counting, inventory checking, and packaging effort encourage customers to order in full pallets, or full cases create half-pallet or quarter-pallet units and encourage customers to order in such units

Pick from Storage streamline picking by having primary picking area (other than secondary back-end storage) smaller in size better equipment 10 to 20 times quicker Is it possible to achieve the same throughput by picking directly from storage?

Pick from Storage possible if highly sophisticated logistics information system random storage, intelligent slotting, activity balancing, dynamic wave planning high degree of mechanization disciplined workforce

Pick Task Simplification work element Method Requirements traveling bring pick location to picker; batch picking; zone picking stock to picker systems; classifying and sorting orders documenting automate information flow computer-aided order picking: automatic identification, light, RFID, headset reaching items at waist level vertical carousels, person-abroad AS/RS; miniload AS/RS searching stock to picker; direct picker to location; highlight location stock to picker systems; person-abroad AS/RS; pick-to-light systems extracting automated dispensing automatic item pickers, robotic order pickers counting weight counting; standard size scale on picking restocking automated restocking real time WMS socializing dedicated pick zone idling/waiting dynamic zone sizing; advanced job on hand real time WMS

Trade off for Traveling reduce traveling by batch picking, zone picking, and wave picking batch picking (i.e., grouping orders in picking) zone picking (i.e., ungrouping lines (items) of orders in picking and regrouping lines into orders) wave picking (i.e., all zones picking the same set of orders at the same time and regrouping items into orders)

Case Study Dallari, F. , G. Marchet, and M Case Study Dallari, F., G. Marchet, and M. Melacini (2009) Design of Order Picking System, International Journal of Advanced Manufacturing Technology, 42, 1-12

Design of an Order Picking System order characteristics Design of an Order Picking System order picking system: equipment, layout, human resources, etc. strategic level considerations

Factors to Consider order characteristics aggregate effect individual orders: frequency, number of lines, quantity requested, shape and weight of items, etc. aggregate effect average number of orders per day, total number of SKU

Grouping of Items case study different ways, e.g., by size, frequency, nature, etc. case study by size average # of lines  15 lines possibly sub-division in group

Observations from Empirical Studies

Empirical Study picking methods observed from 68 warehouses in Italy from trade journals, interviews of MHE suppliers, and interviews of warehouse management small- to medium-sized companies, of revenue greater than 10 Euro 5 picking methods refinements, e.g., batch vs single order picking, setting of primary picking area

Empirical Study: 5 Picking Methods

Five Picking Methods Adopted by 68 Warehouses in Italy

Results from Statistical Analysis SKUs  1,000: picker-to-parts SKUs > 1,000 & small # of lines per day: parts-to-picker large # of SKUs: hard to use picker-to-parts large # of order lines: hard to use parts-to-picker large # of order lines per day and large number of items: pick-and-sort and pick-to-box

Further Segmentation by Size small orders (i.e., order volume  0.5 m3) and large orders (i.e., order volume > 0.5 m3) pick-to-box: only for small orders picker-to-parts: for both small and large orders regardless of effect of # of order lines picked per day and the # of items managed when applied to large orders parts-to-picker: both small and large orders

Further Segmentation by Size: Small Orders

Further Segmentation by Size: Large Orders

For the Specific Case Study

Characteristics of Groups on average an order  15 lines

Results a pick-to-box system picker-to-parts systems group 1 items (9,000 items; 7,450 order lines/day) picker-to-parts systems group 2 items (1,500 items; 2,500 order lines/day) group 3 items (300 items; 50 order lines/day)

Equipment and OPS for Group 1 Items different storage methods and identification technologies storage methods gravity flow racks for high throughput items (500 items; more than 1 m3 per week) shelves for the rest primary plus secondary storage for some shelved items identification technologies pick-to-light for 10% of items accounting for 70% of order lines radio frequency terminals for the rest a 4,000 m2 picking area, operated by 12 pickers

Equipment and OPS for Groups 2 & 3 Items homogeneous items with each outflow  1 m3 per week a pallet storage location for each item matching the unit loads received in the warehouse picker-to-parts, first level as the forward area and upper levels as the reserve area group 2 items: batch picking policy group 3 items: single-order picking policy a 6,000 m2 picking area, employing 5 pickers

Results

Results