MTTN L11 Order-picking MTTN25 Warehousing and Materials Handling. Warehousing and Materials Handling 1. Content. Learning objectives

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1 L11 Order-picking MTTN25 Warehousing and Materials Handling Warehousing and Materials Handling Tools & Techniques Optimization models Pick-paths Inclusion of SKU in FPA Lane depth & slotting L11 Layout Location of receiving & shipping Aisle configuration, Stack height Forward Pick Area Activity Profiling Measurement & Statistical analysis of Warehouse activity / Data Mining Benchmarking Performance measurement L15 Processes Receiving L11 Put-away Storage Pick Pack, Ship Joakim Kembro Engineering Logistics Lund University Resources Equipment Racks & Shelves Handling & Transportation Automation Mobile picking L13 Labor Management Scheduling FT vs. Temps Safety regulations Union rules ISIT/WMS Support the operation with space allocation, route planning, consolidated picking and statistics 3 Learning objectives Learn what order picking methods that are available Understand some basic picking ergonomics Understand advantages and disadvantages of different order picking methods Understand the benefits of pick-path optimization and how it is done Content Order-picking Ergonomics and street-smart Picking methods Pick-path optimization 4 5 Warehousing and Materials Handling 1

2 Today s focus: Order-picking Operating cost distribution in a typical warehouse (CapEx vs. OpEx) Order-picking intensive warehouses: Amazon.com Adlibris.com CDON.com ICA (fruit & vegetables) Elektroskandia (e.g. Cylinda) Receiving; 15% Put away/ Storage; 20% Shipping; 15% Order picking; 50% Receiving Put-away Storage Pick Pack, Ship 6 Source: Frazelle, (2002) World-Class Warehousing and Material Handling, Figure 8-1, p A customer order is picked and packed in order to later ship it We have three different types of picking in a warehouse Receiving Customer order Customer: Store AB Item Quantity Screw 3 Cord 5 m Plug 50 Pick order No: A Pick Item Quantity Aisle Position Shelf 1 Screw B 2 Cord 5 m 14 7 A 3 Plug A Pallets Pallet reserve Pallets Crossdock Pallets Carton pick Cartons Cartons Each pick Eaches Sorting Unitizing Shipping 8 9 Warehousing and Materials Handling 2

3 Order-picking activities and time? Order-picking activities and time Activity % Order-picking time Traveling 55% Searching 15% Extracting 10% Paperwork and other activities 20% Pick with cart Picking small items Warehousing and Materials Handling 3

4 Picking to belt with pick to light Pick to pallet Picking from the 2nd level Content Order-picking Ergonomics and street-smart Picking methods Pick-path optimization Warehousing and Materials Handling 4

5 Ergonomics: Placing the most frequently requested items on the best height Ergonomics: Pick from pallet 1. Elevated floor 2. Pick from side The Golden Zone Warehouse street-smart Warehouse street-smart Warehousing and Materials Handling 5

6 Warehouse street-smart Content Order-picking Ergonomics and street-smart Picking methods Pick-path optimization Picking methods Description of methods Picker to parts Employing humans Order picking methods retrieval Parts to picker Employing machines Automated picking Picking robots Basic order picking: Operations with a small number of orders and high number of picks per order Batch picking / Multi-order picking: Operations with a large number of orders and low picks per order Zone picking: Operations with high total numbers of SKUs, high total numbers of orders, and low to moderate picks per order Wave picking: Operations with high total number of SKUs and moderate/high picks per order Warehousing and Materials Handling 6

7 Full orders / Zone picking Basic order picking Full order picking Order picking method Zon B Zone picking (Partial order picking) Buffer Zon A Product stored in fixed locations on shelves or pallet rack One order at a time following a route up and down each aisle Design of the picking flow should be such that the order picker ends up fairly close to the original starting point Picking document should have the picks sorted in the same sequence as the picking flow Work well in operations with a small total number of orders and a high number of picks per order Operations with low picks per order will find the travel time excessive in this type of picking Operations with large numbers of orders will experience congestion from many pickers working in the same areas Batch picking / Multi-order picking Picking all the items for one order Multiple orders are grouped into small batches Order picker will pick all orders within the batch in one pass using a consolidated pick list Usually the picker will use a multi-tiered picking cart maintaining a separate carton on the cart for each order. Batch sizes usually run from 4 to 12 orders per batch depending on the average picks per order in that specific operation. Batch picking systems may use extensive logic programmed to consolidate orders with the same items Batch picking can greatly reduce travel time by allowing the picker to make additional picks while in the same area 28 One order at a time Single order picking + Fast to pick one order Easy to keep track Less room for errors - Low efficiency (A lot of transport) Full order picking Batch picking Several orders at a time + High efficiency (Less transport) - More room for errors Need to keep track of progress 29 Warehousing and Materials Handling 7

8 Partial order picking (zone picking) Different forms of zone picking + No congestion Only one picker per zone Picker learn zone - Faster routing Knowledge about details Work with balancing zones Progressive assembly An order passes through zones in a specified order Downstream sortation Each zone work independent with its specific items on each order: It s fast to get an order through Requires expensive sorting after the picking No risk for starvation between zones Wave picking Zones are synchronized so that pickers work in a wave: It s fast to get an order through Can reduce the need for sortation Zones have to wait for each other Unbalances always occur between pickers Buffers between zones are needed No traceability for finding errors A B C A B C A B C Sortation Sortation Zone picking in detail Wave picking in detail Picking area is broken up into pick zones (assembly lines) Order pickers are assigned a specific zone, and only pick items within that zone Orders are moved from one zone to the next as the picking from the previous zone is completed Conveyor systems are used to move orders from zone to zone Important to balance the number of picks per zone to maintain a consistent flow Separate zones provide for specialization of picking techniques (automated handling in one and manual handling in the next) Rather than orders moving from one zone to the next for picking, all zones are picked at the same time Items are later sorted and consolidated into individual orders/shipments Wave picking is the quickest method (shortest cycle time) for picking multi-item orders Wave picking may be used to isolate orders by specific carriers, routes, or zones Warehousing and Materials Handling 8

9 Content Order-picking Ergonomics and street-smart Picking methods Pick-path optimization Travel time to retrieve an order is a direct expense Largest component of labor in a typical distribution center Travel time is waste (no value added) Affects customer service (faster retrieval, better service) Order picking for only 2 4 SKUs and a few locations: Sequence locations to be visited to minimize travel Solved for each trip an order picker must make into the warehouse Unlike the fast-pick area, where the general path of travel is common and known in advance Pick-path optimization becomes very important The problem of pick-path optimization Traveling salesperson problem (TSP) Visiting a given set of locations as quickly as possible: Traveling Salesman Problem TSP is difficult in several senses: There is no known fast solution technique that works in general Randomly-generated instances, even small ones, can be surprisingly time-consuming to solve Optimum, or even good solutions can be complex and hard to describe NP-hard problem Solving by complete enumeration A classic operations research problem Applies to pick-path optimization Usually last-mile to customer Extended version referred to as the Vehicle Routing Problem (VRP) Warehousing and Materials Handling 9

10 Denoting the TSP Example: Pick-path optimization G = (N,A) Distance matrix Network N, set of nodes A, set of arcs Each arc (i,j) in A is associated with: c ij, traveling cost per unit flow (symmetric) x ij, 1 if arc is traversed, otherwise 0 c ij Beehive Example: Short-haul transportation planning Shortest path between the different locations Distance matrix Network Groups of 2 2 minutes Prepare to give an answer c ij Warehousing and Materials Handling 10

11 Order-retrieval in a warehouse presents a special case of the TSP Short travel paths that are realizable by an order picker without a detailed warehouse map Travel is constrained by aisles and this special structure makes it possible to find optimal solutions quickly by computer Most WMSs do not support pick-path optimization: Geometric layout of the warehouse (including distances between all pairs of storage locations) Time-consuming to gather Problem of communicating the path to the picker WMS tells the picker only the sequence of locations, not the actual path to follow Find an efficient global path to visit all the storage locations of a warehouse Sort pick lines on a customer order by storage location so that they appear in the same sequence as the efficient global path Global path is efficient => The sub-path induced on each customer order is likely to be efficient Path outlines Pick-path optimization A good global path should: Induce short sub-paths on the customer orders, Help the picker visualize the next location and how to travel there most directly Three commonly found path outlines: Along a single aisle Through static shelving is the so-called serpentine pick path The branch-and-pick, which sequences only the aisles and not the locations within an aisle Store popular SKUs close to the path outline, so that they can be reached with little or no detour Store SKUs according to affinity Restrict the picker to revisit a previously-visited aisle Each order-picker can be imagined to follow this rule: Pick all the required items from the current aisle and travel forward to the next aisle Two ways of traveling to the next aisle: Travel all the way through the current aisle Enter the aisle only as far as necessary to pick all required items therein and then return to the same end of the aisle Warehousing and Materials Handling 11

12 Learning objectives Learn what order picking methods that are available Understand some basic picking ergonomics Understand advantages and disadvantages of different order picking methods Understand the benefits of pick-path optimization and how it is done Thank you for today! Box 118, SE LUND, Sweden Visiting address Ole Römers väg 1, Lund Phone Fax Joakim Kembro PhD Candidate Department of Industrial Management and Logistics Warehousing and Materials Handling 12