Improving Product Location and Order Picking Activities in a Distribution Center

Transcription

1 Improving roduct Location and Order icking Activities in a Distribution Center Jacques Renaud Angel Ruiz Université Laval Centre Interuniversitaire de Recherche sur les Réseaux d Entreprise, la Logistique et le Transport - resentation Outline Introduction Warehouse design and operations Conveyor belt layout Order picking procedure Actual product location strategy New product location strategies Computational results Further results using a Traveling salesman model

2 Introduction Both distribution centers (DC) and warehousing operations are key elements in supply chain efficiency. DC efficiency and throughput are the result of technological and design choices. Although modern supply chain management strategies focus on reducing inventory, product diversification and customization require handling additional stock keeping units (SKU s). For modern DC, the flowthrough is a competitive element.

3 Introduction Warehousing decisions Storage strategies : Assign SKUs to storage location Dedicated storage A A A A A A A A A A D D D D A A C C C C C C B B B B E E Random storage Classed-based storage

4 Introduction Warehousing decisions Order picking strategies : How the SKUs are grouped into picking lists and subsequently retrieved from their storage locations by one or many pickers. Discrete picking Zone picking Batch picking Wave picking

5 Introduction Warehousing decisions Routing strategies : Determine the sequence in which the SKUs on a given picking list are collected, the objective being to minimize the distance covered by the pickers. Objective of this study Optimize both product location and order picking activities (including the routing) of a high throughput DC.

6 Literature Review Order icking The general discrete order picking problem is a traveling salesman problem (Np-Hard). Many researchers studied special warehouse configurations which lead to polynomial solvable cases : Ratliff & Rosenthal (1983) Goetschalckx & Rafliff (1988) De Koster & van der oort (1998) Vaughan, Roodbergen & De Koster (2001) No work related to conveyor like the one studied here.

7 roduct location Considerably less attention Literature Review roduct location is highly dependent on warehouse configuration and order picking strategy and technology. Most of the work deals with specific cases. Heskett (1963), cube-per-order index, Jarvis & McDowell (1983), minimize average order picking time Vickson & Fujimoto (1996), optimal location in a bi-directional carousel Jewkes, Lee & Vickson (2004), product location along a picking line No work related to conveyor like the one studied here.

8 In this study Warehouse design and operations External retailers may order any quantity of any product. roducts for these customers are assigned to storage locations (slots) in a mezzanine shelving system on both sides of a conveyor belt, according to a dedicated storage policy. For a given order, a single picker walks along the shelves, gathers the required quantities of the products from the various locations along the route (broken case picking), and puts them on the conveyor belt which automatically moves them to the right truck in the shipping area.

9 Warehouse design and operations Detailed objective : Improving the storage and order-picking operations by : (1) optimizing the allocation of products to storage locations, and (2) reviewing the picking (routing) strategy.

10 Conveyor belt layout 2 AL 4 AL 5 AL 3 AL 4 AL 5 AL F E D C B A ESCALIER F301 F302 C302 B302 F303 D303 C303 B303 A303 ESCALIER F304 D304 C304 B304 A304 F305 E305 D305 C305 B305 A305 F306 E306 D306 C306 B306 A306 F307 E307 D307 C307 B307 A307 F308 E308 D308 C308 B308 A308 F309 panneaux E309 D309 panneaux C309 B309 panneaux A309 F310 E310 D310 C310 B310 A310 F311 panneaux E311 D311 panneaux C311 B311 panneaux A311 F312 E312 D312 C312 B312 A312 F313 E313 D313 C313 B313 A313 F314 E314 D314 C314 B314 A314 F315 E315 D315 C315 B315 A315 F316 E316 D316 C316 B316 A316 F317 E317 D317 C317 B317 A317 F318 E318 D318 C318 B318 A318 F319 panneaux E319 D319 C319 B319 panneaux panneaux A319 F320 E320 D320 panneaux panneaux C320 B320 A320 F321 E321 D321 C321 B321 A321 F322 panneaux E322 D322 C322 B322 A322 F323 m ASSAGE ASSAGE ASSAGE A323 F324 E324 D324 C324 B324 A324 F325 E325 D325 C325 B325 A325 F326 E326 D326 C326 B326 A326 F327 E327 D327 C327 B327 panneaux A327 F328 E328 D328 C328 B328 A328 F329 E329 D329 C329 B329 A329 F330 E330 D330 C330 B330 A330 F331 panneaux E331 D331 panneaux C331 B331 A331 F332 E332 D332 C332 B332 A332 F333 panneaux E333 D333 panneaux C333 B333 A333 F334 E334 D334 C334 B334 panneaux A334 F335 E335 D335 C335 B335 panneaux A335 F336 E336 D336 C336 B336 A336 F337 E337 D337 C337 B337 A337 D338 C338 B338 A338 D339 panneaux C339 B339 A339 D340 C340 B340 A340 D341 C341 B341 A341 D342 panneaux C342 B342 panneaux A342 Doors for crossing the belt D343 C343 B343 panneaux A343 D344 C344 B344 A344 D345 C345 B345 A345 D346 C346 B346 A346 D347 C347 B347 A347 D348 panneaux C348 B348 A348 D349 C349 B349 A349 D350 anneaux anneaux A350 D351 D352 D353 D354 D355 D356 D357 D358 D359 roducts to the trucks in the shipping area icking lists printer Empty wooden board The conveyor belt A total of 240 storage locations Heavy products section

11 roduct categories Conveyor belt layout Regular product (80%) : can be ordered by any retailer. Vending product (20%) : Are shipped only to New Brunswick. They are restricted to section F. 2 AL 4 AL 5 AL 3 AL 4 AL 5 AL F E D C B A ESCALIER F301 F302 C302 B302 F303 D303 C303 B303 A303 ESCALIER F304 D304 C304 B304 A304 F305 E305 D305 C305 B305 A305 F306 E306 D306 C306 B306 A306 F307 E307 D307 C307 B307 A307 F308 E308 D308 C308 B308 A308 F309 panneaux E309 D309 panneaux C309 B309 panneaux A309 F310 E310 D310 C310 B310 A310 F311 panneaux E311 D311 panneaux C311 B311 panneaux A311 F312 E312 D312 C312 B312 A312 F313 E313 D313 C313 B313 A313 F314 E314 D314 C314 B314 A314 F315 E315 D315 C315 B315 A315 F316 E316 D316 C316 B316 A316 F317 E317 D317 C317 B317 A317 F318 E318 D318 C318 B318 A318 F319 panneaux E319 D319 C319 B319 panneaux panneaux A319 F320 E320 D320 panneaux panneaux C320 B320 A320 F321 E321 D321 C321 B321 A321 F322 panneaux E322 D322 C322 B322 A322 F323 m ASSAGE ASSAGE ASSAGE A323 F324 E324 D324 C324 B324 A324 F325 E325 D325 C325 B325 A325 F326 E326 D326 C326 B326 A326 F327 E327 D327 C327 B327 panneaux A327 F328 E328 D328 C328 B328 A328 F329 E329 D329 C329 B329 A329 F330 E330 D330 C330 B330 A330 F331 panneaux E331 D331 panneaux C331 B331 A331 F332 E332 D332 C332 B332 A332 F333 panneaux E333 D333 panneaux C333 B333 A333 F334 E334 D334 C334 B334 panneaux A334 F335 E335 D335 C335 B335 panneaux A335 F336 E336 D336 C336 B336 A336 F337 E337 D337 C337 B337 A337 D338 C338 B338 A338 D339 panneaux C339 B339 A339 D340 C340 B340 A340 D341 C341 B341 A341 D342 panneaux C342 B342 panneaux A342 D343 C343 B343 panneaux A343 D344 C344 B344 A344 D345 C345 B345 A345 D346 C346 B346 A346 D347 C347 B347 A347 D348 panneaux C348 B348 A348 D349 C349 B349 A349 D350 A350 anneaux anneaux D351 D352 D353 D354 D355 D356 D357 D358 D359

12 Conveyor belt layout Conveyor modeling We modelled the belt as an undirected connected graph, in which each storage location corresponds to a node and in which an edge (undirected arc) exists between each pair of adjacent nodes. C321 B321 C322 B322 B333 A333 Footbridge B334 - B D A334 C324 B324 B335 A335 - B C325 B325 C321 B321 B333 B333 5 C B322 B334 6 B C B324 B335 B C325 B325

13 Order icking rocedure A picker starts the tour at location A303, where a computer prints the picking list. S/he visit sections B, C, F, E, D and A in that order before returning to location A303. In this strategy, the picker uses a predetermined route (but he can skip useless part of the belt). 2 AL 4 AL 5 AL 3 AL 4 AL 5 AL F E D C B A ESCALIER F301 F302 C302 B302 F303 D303 C303 B303 A303 ESCALIER F304 D304 C304 B304 A304 F305 E305 D305 C305 B305 A305 F306 E306 D306 C306 B306 A306 F307 E307 D307 C307 B307 A307 F308 E308 D308 C308 B308 A308 F309 panneaux E309 D309 panneaux C309 B309 panneaux A309 F310 E310 D310 C310 B310 A310 F311 panneaux E311 D311 panneaux C311 B311 panneaux A311 F312 E312 D312 C312 B312 A312 F313 E313 D313 C313 B313 A313 F314 E314 D314 C314 B314 A314 F315 E315 D315 C315 B315 A315 F316 E316 D316 C316 B316 A316 F317 E317 D317 C317 B317 A317 F318 E318 D318 C318 B318 A318 F319 panneaux E319 D319 C319 B319 panneaux panneaux A319 F320 E320 D320 panneaux panneaux C320 B320 A320 F321 E321 D321 C321 B321 A321 F322 panneaux E322 D322 C322 B322 A322 F323 m ASSAGE ASSAGE ASSAGE A323 F324 E324 D324 C324 B324 A324 F325 E325 D325 C325 B325 A325 F326 E326 D326 C326 B326 A326 F327 E327 D327 C327 B327 panneaux A327 F328 E328 D328 C328 B328 A328 F329 E329 D329 C329 B329 A329 F330 E330 D330 C330 B330 A330 F331 panneaux E331 D331 panneaux C331 B331 A331 F332 E332 D332 C332 B332 A332 F333 panneaux E333 D333 panneaux C333 B333 A333 F334 E334 D334 C334 B334 panneaux A334 F335 E335 D335 C335 B335 panneaux A335 F336 E336 D336 C336 B336 A336 F337 E337 D337 C337 B337 A337 D338 C338 B338 A338 D339 panneaux C339 B339 A339 D340 C340 B340 A340 D341 C341 B341 A341 D342 panneaux C342 B342 panneaux A342 D343 C343 B343 panneaux A343 D344 C344 B344 A344 D345 C345 B345 A345 D346 C346 B346 A346 D347 C347 B347 A347 D348 panneaux C348 B348 A348 D349 C349 B349 A349 D350 A350 anneaux anneaux D351 D352 D353 D354 D355 D356 D357 D358 D359

14 Order icking rocedure A 5 products example. The storage locations are sorted automatically on the picking list following the sequence BCFEDA. F E D C B A F301 Starting F302 C302 B302 D point F303 D303 D C303 B303 A303 F304 D304 C304 B304 A304 F305 E305 D305 C305 B305 A305 F306 E306 D306- C306 B306 A306 F307 E307 D307 C307 B307 A307 F308 E308 D308 C308 B308 A308 F309-B E309 D309 C309-B B309-B A309 F310 E310 D310 C310 B310 A310 F311 E311-B D311-B C311 B311 A311-B F312 E312 D312 C312 B312 A312 F313 E313 D313 C313 B313 A313 F314 E314 D314 C314 B314- A314 F315 E315 D315 C315 B315 A315 F316 E316 D316 C316- B316 A316 F317 E317 D317 C317 B317 A317 F318 E318 D318 C318 B318 D A318 F319-B E319 D319 C319 B319-B A319-B F320 E320 D320-B C320-B B320 A320 F321 E321 D321 C321 B321 A321 F322 D E322-B D322 C322 B322 A322 F323 Footbridge Footbridge A323 F324 E324 D324 D C324 B324 A324 F325 E325 D325 C325 B325 A325 F326 E326 D326 C326 DISC B326 A326 F327 E327 D327 C327 B327 A327-B F328 E328 D328 C328 B328 A328 F329 E329 D329 C329 B329 A329 F330 E330 D330 C330 B330 A330 F331-B E331 D331 C331-B B331 A331 F332 E332 D332 C332 B332 A332 F333 E333-B D333-B C333 B333 A333- F334 E334 D334 C334 B334-B D A334 F335 E335 D335 C335 B335 A335-B F336 E336 D336 C336 B336 A336 F337 E337 D337 C337 B337 A337 D338 C338 B338 A338 D339-B C339 B339 A339 D340 C340 DISC B340 A340 D341 C341 B341 A341 D342 C342-B B342-B A342 D343 C343 B343 A343-B D344 C344 B344 A344 D345- C345 B345 A345 D346 C346 B346 A346 D347 C347 B347 A347 D348-B C348 B348 A348 D349 D C349 B349 A349 D350 A350 D Congrès conjoint SCRO/Journées D351-B D352 D353 D354de D355 l Optimisation D356 D357 D358 D359-B 2006, Montréal

15 Actual roduct Location Strategy At present, products are assigned to locations based solely on the experience and knowledge of the logistics manager. The rule-of-thumb used by the logistics manager is that products with the highest sales forecast are placed as near as possible to the starting point, filling sections A and B first followed by C, D and E (the allocation is revised 4 times a year).

16 Actual roduct Location Strategy 2 AL 4 AL 5 AL 3 AL 4 AL 5 AL F E D C B A ESCALIER F301 F302 C302 B302 F303 D303 C303 B303 A303 ESCALIER F304 D304 C304 B304 A304 F305 E305 D305 C305 B305 A305 F306 E306 D306 C306 B306 A306 F307 E307 D307 C307 B307 A307 F308 E308 D308 C308 B308 A308 F309 E309 D309 C309 B309 A309 F310 E310 D310 C310 B310 A310 F311 E311 D311 C311 B311 A311 F312 E312 D312 C312 B312 A312 F313 E313 D313 C313 B313 A313 F314 E314 D314 C314 B314 A314 F315 E315 D315 C315 B315 A315 F316 E316 D316 C316 B316 A316 F317 E317 D317 C317 B317 A317 F318 E318 D318 C318 B318 A318 F319 E319 D319 C319 B319 A319 F320 E320 D320 C320 B320 A320 F321 E321 D321 C321 B321 A321 F322 E322 D322 C322 B322 A322 F323 ASSAGE ASSAGE A323 F324 E324 D324 C324 B324 A324 F325 E325 D325 C325 B325 A325 F326 E326 D326 C326 B326 A326 F327 E327 D327 C327 B327 A327 F328 E328 D328 C328 B328 A328 F329 E329 D329 C329 B329 A329 F330 E330 D330 C330 B330 A330 F331 E331 D331 C331 B331 A331 F332 E332 D332 C332 B332 A332 F333 E333 D333 C333 B333 A333 F334 E334 D334 C334 B334 A334 F335 E335 D335 C335 B335 A335 F336 E336 D336 C336 B336 A336 F337 E337 D337 C337 B337 A337 D338 C338 B338 A338 D339 C339 B339 A339 D340 C340 B340 A340 D341 C341 B341 A341 D342 C342 B342 A342 D343 C343 B343 A343 D344 C344 B344 A344 D345 C345 B345 A345 D346 C346 B346 A346 D347 C347 B347 A347 D348 C348 B348 A348 D349 C349 B349 A349 D350 A350 roducts having the highest sales forecasts D351 D352 D353 D354 D355 D356 D357 D358 D359

17 New roduct Location Strategies To obtain a product allocation, two decisions are needed: -in whichorderproduct should be considered, -in whichorderstorage locations should be assigned. Solution rocedure To determine the location allocation, the first non-assigned product in the list was selected and assigned to the first available position in the location list. This procedure was repeated until all the products have been assigned. We used 2 product sorting rules and 3 locations sorting rules.

18 New roduct Location Strategies 1) roduct sorting rule : Quantity Sorts the products in decreasing order accordingly to their forecast demand 2) roduct sorting rule : Frequency Sorts the products in decreasing order of their ordering frequency (the number of times that a product is ordered by customers, independent of the requested quantity) If vending products are taken into consideration, they are automatically allocated to section F.

19 New roduct Location Strategies 1) Location sorting rule : Shortest distance Sort the locations according to their distance from the starting point. 2) Location sorting rule : ABCDEF The second rule, ABCDEF, first sorts the locations by section, following the order A-B-C-D-E-F; then sort the locations within a section according to their distance from the starting point, with those closest to the starting point coming first. 3) Location sorting rule : BCFEDA As the second rule but sections are sorted in the order BCFEDA which is the order followed by the picker. 2 AL 4 AL 5 AL 3 AL 4 AL 5 AL F E D C B A ESCALIER F301 F302 C302 B302 F303 D303 C303 B303 A303 ESCALIER F304 D304 C304 B304 A304 F305 E305 D305 C305 B305 A305 F306 E306 D306 C306 B306 A306 F307 E307 D307 C307 B307 A307 F308 E308 D308 C308 B308 A308 F309 E309 D309 C309 B309 A309 F310 E310 D310 C310 B310 A310 F311 E311 D311 C311 B311 A311 F312 E312 D312 C312 B312 A312 F313 E313 D313 C313 B313 A313 F314 E314 D314 C314 B314 A314 F315 E315 D315 C315 B315 A315 F316 E316 D316 C316 B316 A316 F317 E317 D317 C317 B317 A317 F318 E318 D318 C318 B318 A318 F319 E319 D319 C319 B319 A319 F320 E320 D320 C320 B320 A320 F321 E321 D321 C321 B321 A321 F322 E322 D322 C322 B322 A322 F323 ASSAGE ASSAGE A323 F324 E324 D324 C324 B324 A324 F325 E325 D325 C325 B325 A325 F326 E326 D326 C326 B326 A326 F327 E327 D327 C327 B327 A327 F328 E328 D328 C328 B328 A328 F329 E329 D329 C329 B329 A329 F330 E330 D330 C330 B330 A330 F331 E331 D331 C331 B331 A331 F332 E332 D332 C332 B332 A332 F333 E333 D333 C333 B333 A333 F334 E334 D334 C334 B334 A334 F335 E335 D335 C335 B335 A335 F336 E336 D336 C336 B336 A336 F337 E337 D337 C337 B337 A337 D338 C338 B338 A338 D339 C339 B339 A339 D340 C340 B340 A340 D341 C341 B341 A341 D342 C342 B342 A342 D343 C343 B343 A343 D344 C344 B344 A344 D345 C345 B345 A345 D346 C346 B346 A346 D347 C347 B347 A347 D348 C348 B348 A348 D349 C349 B349 A349 D350 D351 D352 D353 D354 D355 D356 D357 D358 D359 A350

20 New roduct Location Strategies Improvement procedure Given an initial solution and a number of picking lists, the heuristic evaluates, for each possible pair of products, the decrease in the distance walked if their storage locations were exchanged. After all the possible exchanges have been evaluated, the one that offers the most improvement is selected and implemented. This procedure continues until no improvement can be obtained.

21 Computational Results Test Data Real data provided by our industrial partner. Orders from 372 customers between March 21st and May 15th forecast sets of 20 orders each Used in the place of the manager s sales forecast to assign products to specific locations. 4 test sets of 20 orders each Used to evaluate the company s product allocation and the product allocations produced by our algorithms.

22 Computational Results Total picking distances obtained with the Quantity product sorting rule Data set Without any product category With vending/regular products handled separately Shortest ABCDEF BCFEDA Shortest ABCDEF BCFEDA Current location Global % These results demonstrates that vending products should be assigned to section F

23 Computational Results Total picking distances obtained with the Frequency product sorting rule Data set Without any product category With vending/regular products handled separately Shortest ABCDEF BCFEDA Shortest ABCDEF BCFEDA Current location Global % These results demonstrates that vending products should be assigned to section F

24 Computational Results Data set Total picking distances after the improvement procedure [Quantity; * ; Vending] [Frequency; * ; Vending] Shortest ABCDEF BCFEDA Shortest ABCDEF BCFEDA Company s improved location Global % %% % ercentage of reduction of the picking distances produced by the improvement procedure %% Reduction of the picking distances compared to the current company s location

25 Further Results using the TS Actually, the order picker follows a predetermined route through all the sections (skipping useless sections). Clearly this problem is a symmetrical traveling salesman problem which we solved by using the classical 3-Opt (Lin 1965).

26 Further Results using the TS D C B A D C B A D D D D redetermined route 908 feet D Footbridge D D Footbridge D TS route 798 feet D D A saving of 110 feet on this small example D D D D

27 Further Results using the TS Data set Improvement obtained by scheduling order-picking operations by solving a traveling salesman problem [Quantity; * ; Vending] [Frequency; * ; Vending] Shortest ABCDEF BCFEDA Shortest ABCDEF BCFEDA Company s improved location Global % %% % ercentage of reduction in term of distance obtained by solving a TS %% Total reduction of the picking distances compared with the current company s location

28 Conclusion Improvements of up to 11.25% can be achieved if product location is done using a shortest distance rule Using a post-optimization procedure, reduction up to 19% can be achieved Using a TS to schedule order pickers provide an additional 5 to 13% distance reduction Overall, these procedures reduce the total picking distance from 21 to 28% which significantly increase warehouse productivity