Introduction to production systems

Chapter 9 : Storage and Warehouse SystemsAbdulrahim ShamaylehIndustrial Engineering Department11. Warehouse Layout Model3. Automated Storage & Retrieval System2. Storage Equipment2Requirement of efficient and effective handling of materials within various department : keeping storage space accessible Selecting proper placement of every inventory itemImplementing appropriate storage policiesKeeping adequate control of storage policies

3A comprehensive storage system includes:Building housing the storage facilityStorage mediumDock areasProcessing ratesLocation of inventory (supplies, intermediate material and final products)Material handling systemWorkers in charge of storage operations4Receiving and shippingReceiving an shipping operations are affected by the equipment selected and the movement patternObject of a total-system storage and warehousing system design:Choice of means of transportation, Scheduling of transportation activities, andThe integration of storage and material handling operationsInbound operations include: receiving and put awayOutbound operations include: processing, picking, checking, packing, and shipping5Receiving and put awayReceiving operations: include all those performed from the time the order is placed until the products are received at the inbound dockPut away operations starts with the confirmation of location, order quantity, and product batch identification codemain objective is to determine the most effective storage location for the incoming products

6Operations of the put away process:Ensure entire product receipts are validated before products are prepared for their distributionAllow some put away to occur prior to receiving every item on purchase orderPlace products directly in their final locations when received

7Processing customer ordersIt starts when the order is receivedTypical activities : verifying availability of items, Generating pick lists to consolidate the order,Scheduling order picking and shipping operations,Document the entire processGrouping and releasing order activities can be accomplished by a warehouse management system WMS. Coordinate warehouse activities8Order pickingPicking means retrievingProcess of selecting and retrieving specified items from a warehouse in specified quantities to satisfy customer orderLevels of picking an order:Pallet pickingLayout pickingCase pickingSplit-case pickingBroken-case pickingStock keeping Unit (SKU): unique numeric identifier for systematic tracking

9Diagramming the Flow - Functional Flow NetworkFull PalletsCases Mixed PalletsReceivingFlow RackShippingPallet RackPalletizeAccum&SortPlace oriented FunctionMovement oriented FunctionJim AppleArt of material handling10Order pickingThere are four procedure for picking orders which are defined in terms of three parameters: Pickers per order, Number of orders processed, Picking periods per shift

11Procedure for picking ordersDiscrete picking: one worker picks one order of one type of products at any particular timepromotes faster service, and allows accountability for the condition and completeness of an orderDisadvantage : long travel timesZone picking: picking area is divided into several sections; one for each type of product, and one picker is assigned to each sectionGroup picking: one picker is in charge of retrieving items of one type of a product at a time for a group of ordersWave picking: one picker is assigned to each order, considering the requirement of one type of a product at a time. Shift is divided into several picking periods12Combined picking procedures: ExamplesCombine the zone and group pickings procedures. Multiple pickers, multiple types of products picked at a time, one picking period per shiftCombine zone and wave picking procedures. Multiple pickers, single type of product picked at a time, multiple picking periods per shiftCombine zone, group, and wave picking procedures. Multiple pickers, multiple type of product picked at a time, multiple picking periods per shift13Packing and shippingOperations from time an order is placed until the product are finally shippedPacking is an activity that supports the shipping process. It is labor intensive processShipping is part of Customer Service QualityIncreased customer satisfactionReduced delivery times and errorsIncreased sales order throughputThese goals can be advanced by Streamlining the order configuration processProviding management visibility to the orders in processAvoiding configurations errors and shipment delays

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15Cross dockingLogistics of directly moving finished product from the manufacturing plant to the customer with minimum material handling effortsBenefits:Reduction of the need for handling and storing inventoryIncreased emphasis on satisfying demand in a timely mannerStreamlining of the supply chainReduction of operating costsIncreased throughputReduction of product damage and product obsolescence16Placing the Warehouse in the Supply Chain

SupplyCustomerDISTRIBUTORCONVENTIONALStorage

DistributionDIRECT SHIPCROSS-DOCKconsolidateconsolidate

Jim Apple- The art of material handling17Dedicated and Random StorageStorage warehousing can be implemented in 3 ways:Rent in public warehouse on basis of storage volume for a specified period of timeFor long term storage need- lease a warehouseOperate a private warehouse as separate divisionStorage capacity of a warehouse: amount of storage space required to accommodate the materials to be stored in order to meet a desired service level18Dedicated StorageEach product unit load is assigned to a fixed location based on throughput and storage space requiredProducts responsible for more of the travel activity between warehouse and the docks should be assigned to location closer to docks19Dedicated StorageA set of storage locations assigned to a specific product

Decision variablexjk = 1 or 0 for assigning or not assigning product j to location k

Measure of effectivenessMinimize total expected distance traveled20Notationq = number of storage locationsn = number of productsm = number of input/output points (docks)Sj = number of storage locations required by product jTj = number of trips in/out of storage for product jpi = percentage of travel in/out of storage to/from point idik = distance or time required to travel from point i to location k

21Mathematical model

22fk = pi dik

Min

(

fk xjk ) =

( f1 xj1 + f2 xj2 + + fq xjq )

23Solution Procedure

24ExampleWarehouses dimensions: 40 x 40 ftStorage Location: 10 x 10 ftOne receiving dock at the northeast corner of the layoutOne shipping dock at the midpoint of the west sideTwo products A and BProduct A: 100 pallets per week (TA=100)Product B: 80 pallets per week (TB=80)Product A requires 10 storage bays (SA=10)Product B requires 4 storage bays (SB=4)

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27Random StorageIncoming items are equally likely to be stored among all available storage spacesIncoming items are stored in the available location that is closest to the input/output point (dock)Advantage: better utilization of the available storage space

28Problem 9.1Suppose that a 40-ft by 40-ft warehouse is used to store two products P and Q under a dedicated storage policy. The floor of the warehouse can be represented as a grid with 10-ft by 10-ft cells, each cell corresponding to one space storage unit. In this grid, the left-bottom corner represents the location of a dock. Pallets of products are moved between a dock and the warehouse, along rectilinear distances. The first product accounts for about 30% of the total travel activity and the second one for the remaining 70%. The first product requires typically 6 storage space units and second product requires 9 units per day. Find the policy that minimizes total travel distance.29Problem 9.2

A warehouse is 200' long and 100' wide with three docks located as shown in the following figure, where the distance between rows of storage locations is negligible. Two products A and B are to be stored. Product A enters the warehouse at dock1 at a rate of 600 pallet loads per month, and is shipped from docks 2 and 3 at rates of 120 and 480 pallet loads per month, respectively. Product B enters the warehouse at dock 1 at a rate of 1000 pallet loads per month and is shipped from docks 2 and 3 at rates of 200 and 800 pallet loads per month respectively. Storage spaces of 8000 and 12000 square feet are required for A and B, respectively. The warehouse is arranged into bays of 20' by 20 and only one type of product can be stored in a given bay. Assume rectilinear travel.30Problem 9.3Consider a rectangular warehouse layout with 10 x 10 ft storage bays. The layout consists of four rows and four columns of bays. There is one dock located at the top-left corner of the layout. Two classes of products A and B are to be stored using dedicated storage. Class A items represent 20% of the input/output activity and have a requirement of 8 storage bays. Class B items represent 80% of the input/output activity and have a requirement of 8 storage bays. Design an optimal layout. Include all work needed to support your answer.31Problem 9.4

Suppose the storage area for a warehouse is as shown below. Two input/output points serve the storage area, with the overall activity being about 50% for each dock. All movement is in full-pallet quantities. The storage area is subdivided into 10x10 ft storage bays. Three classes of products (A, B, C) are to be stored. Class A items represent 20% of the input/output activity and have a dedicated-storage requirement of 3 storage bays; class B items generate 65% of the trip activity and have a dedicated-storage requirement of 6 storage bays; class C items generate 15% of the input/output activity and have a requirement of 5 bays. Indicate the optimal warehouse layout, showing all supporting calculations.32Problem 9.5Consider a rectangular warehouse of dimension 3 by 3 bays. Each storage bay is of size 20 x 20 ft. There are two products A and B and one dock located at the middle of the left-hand side of the warehouse. Product A requires 4 storage locations and product B requires 3 storage locations. Product A represents 20% of the input/output activity and Product B represents 80% of this activity. (a) Find the optimum dedicated-storage layout; (b) find the expected distance traveled for dedicated storage; (c) if randomized storage is used, such that each bay is equally likely to be used for storage, find the expected distance traveled; (d) compute an upper bound for randomized storage that will yield an expected distance traveled equal to or less than that for dedicated storage.33Models for Determining Storage CapacityService Level ApproachBased on the desired service levelCost-Based ApproachTotal storage cost of the facility34Service Level ApproachAmount of storage space is minimized subject to the constraint that a specified probability of space shortage, (0<