PALLET STORAGE AND RETRIEVAL SYSTEM

Transcription

1 PALLET STORAGE AND RETRIEVAL SYSTEM The materal n ths chapter wll focus on pallet load storage and retreval operatons n warehouse. Ths handlng unt s very often present n warehousng processes BUT, WHEN WE ARE TALKING ABOUT PALLET WHAT DOES IT MEAN? Usually, t s somethng lke that A lot of dfferent models are developed and materals used Dfferent materals, szes, shapes, and somethng new Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester 006 1

2 Dfferent palletzng systems are developed Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester 006

3 The materal n ths chapter wll focus on pallet load storage and retreval operatons n warehouse. Ths handlng unt s very often present n warehousng processes PALLET STORAGE SYSTEMS The most popular pallet storage systems are Block stackng Stackng frames Sngle-deep selectve pallet rack Double-deep pallet rack Drve-n rack Drve-thru Pallet-flow rack Push-back rack Moble racks Also, t could be found deep-lne racks as well as some specal constructons Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester 006 3

4 Block stackng Typcally loads stacked on top of each other and stored on the floor n storage lanes, to 10 loads deep. Stacks may range a heght dependng a lot of factors (safe lmts, weght, pallet condtons ) Typcal queston s concerned on lne depth Frst queston of the lane Let w, d are standard pallet wdth and depth Lane s x pallets deep g gap between adjacent lnes a asle wdth, then footprnt of the lane (dedcated for a sngle SKU) s (g+w)(dx+a/) We have to store N pallets where n dfferent tems to be stored In floor storage SKU s stored wth z x pallets per lane and occupes [q / (z x)] lnes. Assumng that average about half of each SKU s present n the warehouse, there are lnes occuped. To elmnate (mnmze) roundng max. error, we assume that lne occuped for tem could be expresses as [q / ( z x)] + 1/ N n q 1 Multplyng by the footprnt of a lane gves average floor area S occuped by whole populaton of SKUs: n q 1 a ( ) (g w) (d x ) z x 1 Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester 006 4

5 Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester 006 5, z q x a n d follows : 0, ) x z 4 q a d ( w) (g dx ds ) 4 a x z 4 q a x d z q ( w) (g S ) a x (d w) (g ) 1 x z q ( S n 1 n 1 n 1 n 1 Example: Asle a = 4m, Pallet (w d) =1, 0,8 m n = 3 n 1 * z q n d a L (x) SKU q z A 50 3 B 40 4 C 36 (pallets) * 6 6,06 6,68 0,91 ) ( 3 0,8 4 L Of course, n practce, d has to be corrected (typcally addng at least 0,1 m) The result then follows settng the dervate of average floor space S to zero and solvng for optmal lne depth x:

6 Ths system support FILO dscplne, when nventory turns n large ncrements Concernng lmtatons, generated wth loads removed from a storage lane, a space loss phenomenon referred to as honeycombng occurs. That s the reason that lne depth must be carefully determned. The nvestment n a block system s low, near nfnte flexblty for floor space confguraton Pallet stackng frames Stackng frames are commonly used when loads are not stackable and other rackng alternatves are not justfable. They are useful to ncrease storage densty as normally open floor-space. A sngle stackng frame costs $100 - $300 Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester 006 6

7 Sngle deep (selectve) pallet rack They are smple metal constructon provdng mmedate (pck-face) access to each unt (wthout honeycombng) 100% FIFO enabled. Stackng heght s not lmted by stackablty, (t could be up to 40 m), dependng on materal handlng system nvolved. Typcal prce of rack poston s $40 - $50. Major dsadvantage s amount of space devoted to asles. Most storage systems beneft from the use of at least some selectve pallet rack for SKUs whose storage requrements s less then 3 to 5 pallet loads. Pallet Rack Accessores for Maxmum Versatlty Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester 006 7

8 Asle wdth s very mportant. There are many techncal solutons n fork-lft technques Here s one comparson > m 3,5 m,5 m Vehcle Type Space Utlzaton Productvty Cost Flexblty Standard Wde Asle Forklft Baselne Narrow Asle Reach +0% to +5% Narrow Asle Double Deep Reach -0% to +60% VNA Turret +40% to +50% VNA Swng Mast or Bend +35% to +45% $ $ $ $ $ $ $ $ $ $ $ $ $ Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester 006 8

9 Double deep pallet rack The advantage of two deep pallet rack s that fewer asles are needed (50% asle savngs acheved versus sngle deep selectve rack. But, here s utlzaton les due to honeycombng. Ths type of rack s used when the storage requrement for SKU s >5 pallets, when product s receved and pcked frequently n multples of pallets. Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester 006 9

10 Drve n rack Drve n racks extend the reducton of asle space begun wth double deep pallet rack by provdng storage lanes to 10 load deep and 3 5 loads hgh; constructon enables a lft truck to drve nto the rack several pallet postons and store/retreve a pallet. Dsadvantages are a reducton of lft truck travel speed and honeycombng losses; LIFO Drve n rack s best used for slow to medum velocty SKUs wth 0 or more pallets Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester

11 Drve thru rack Drve thru rack are smlarly drve n rack that s accessble from both sdes of the rack. It s for stagng loads n a flow thru fashon where a pallet s loaded at one end and retreved at the other end. FIFO s also acheved. Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester

12 Pallet flow rack In pallet flow rack loads are conveyed (FIFO) on dfferent types of conveyors, form one end of storage lane to the other. As a load s pcked, the next load (f any) advances to pck face. The man purpose of pallet flow rack s to provde hgh throughput pallet storage and retreval and good space utlzaton. Prce s the major dsadvantage: $00 - $300 per storage poston. Push back rack Ths type provdes LIFO to 5 pallets deep lne. Durng storng, force of putaway vehcle pushes the other loads n the lane back to create room for the addtonal load. As a load s removed from the front of a storage lane, the weght of remanng automatcally advances remanng loads to the rack face. Push back racks are approprate for medum to fast movng SKUs. Cost s n the range of $150 per pallet poston. Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester 006 1

13 Moble rack Essentally, they are sngle-deep pallet racks on wheels and tracks permttng entre row of racks to move away from adjacent rack rows. As result, les then 10% OF floor space s devoted to asles and the storage densty s the hghest. But productvty of pallet retreval s lowest. So, they are acceptable where space s expensve, wth slow movng SCUs. The costs are typcally n range of $50 per pallet poston. Pallet storage system selecton Fgure s desgned to assst n storage system confguraton. The example s taken from partcular case and cannot be generalzed because the preference regons vary wdely as a functon of the cost and avalablty of labor and space. Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester

14 PALLET STORAGE/RETRIEVAL SYSTEM The most popular pallet S/R systems are based on: Walke trucks Counterbalance lft truck Straddle trucks Straddle reach trucks Sdeloader trucks Hybrd trucks Automated storage and retreval (AS/RS) systems Walke trucks Walke trucks enables a pallet to be transported on a shorter dstances, and some types enables a pallet to be lfted and stacked. They are typcally approprate where short dstances, low vertcal storage heght and low cost solutons and low throughput are desred. Some are motorzed and desgned for hgher stackng (walke stackers) Pallet truck Pallet jack Motorzed hand truck Walke low lft Motorzed hand/rder Walke low lft rder Motorzed walke stacker Walke stacker manually powered Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester

15 Counterbalanced lft trucks They can be gas, ol or battery powered. Besdes forks, other attachments may be used. Lftng heght s typcally below 7 7,5 m and capacty up to 50 t. They are used ordnary for selectve pallet racks, push back but they are used as well for putaway/retreve operatons as for truck load/unload operatons. Flexblty, coupled wth relatve low cost make them for benchmark for all pallet retreval vehcles. The major drawback s wde turnng radus and wde asles (wth 1 t capacty around 3,5 m). Straddle trucks Ths truck provdes load and vehcle stablty usng outrggers to straddle the pallet load, nstead a counterbalanced weght, resultng wth asle wth,5 3 m. It s necessary to support the floor level load on rack beams. Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester

16 Straddle reach trucks They are Developed from conventonal straddle trucks by shortenng the outrggers and provdng reach capablty wth two type of mechansms (fork and mast reach). So they do not need to be drven under the floor load level to enable storage poston. Also, double deep reach truck s avalable. Sdeloadng trucks A sdeloadng truck loads and unloads rack from one sde, thus elmnatng the need to turn n the asle to access storage postons. Ether mast moves on a set of tracks transversely or the fork project from a fxed mast on a pantograph. The major drawback s the need to enter the correct end of the asle to access a partcular locaton, thus addng routng complexty. Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester

17 Turret trucks Turret trucks (swngmast or swngreach models) do not requre the vehcle to make a turn wthn the asle to store or retreve pallet. Load s lfted by forks that swng on the mast, a mast that swngs from the vehcle, or a shuttle fork mechansm. AS/RS Automated storage/retreval system AS/RS conssts on ntegrated that mplement storage/warehousng elements (storage medum, transport mechansm and controls) wth varous levels of automaton for fast and accurate random storage of products, wth hgh productvty. Ths s based on smultaneously vertcal and horzontal travel of S/R machne. Racks are hgh up 30m or more, S/R machne operates n narrow asle. It s connected wth recevng/shppng ponts by varous technques. Some of possble confguraton alternatves are: Double deep storage wth sngle load wdth asle Double deep storage wth double load wdth asle Deep lane storage wth sngle load wdth asle Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester

18 Storage racks comparson Type of Rack Storage Pattern All Loads Accessble FIFO Retreval Prncpal Advantage Prncpal Dsadvantage Standard sngle deep yes yes - cube utl. Narrow Asle sngle deep yes yes cube utl. truck cost Deep Reach > 1 deep no no cube utl. truck cost Drve In > 1 deep no no cube utl. honeycomb loss potental Drve Thru > 1 deep no yes cube utl. honeycomb loss potental Flow Thru > 1 deep no yes cube utl. rack cost Push Back > 1 deep no no cube utl. rack cost Sldng Racks sngle deep yes yes cube utl. rack cost + T S/R tme Pallet retreval system comparson (typcal data) Counter - balance Straddle Straddle Reach Sde loader Turret AS/RS Vehcle cost $30,000 $35,000 $40,000 $75,000 $95,000 $00,000 Lft heght Capacty m 7 6, Asle wdth m 3,5,5-3 -,5 1,5-1,5-1.5 Weght capacty t 3,5,5 3 3 Lft speed m/mn Travel Speed /mn Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester

19 Storage/retreval machnes use a transport shuttle to place unt loads n storage lanes that are one to seven postons deep Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester

20 ALTERNATIVE BULDING CONSTRUCTIONS FOR PALLET RACK WHs Momčlo Mljuš LM506 Warehouse management and modelng Izmr Unversty of economcs - Logstcs department Fall semester 006 0