Next Generation Factory Layouts: Research Challenges and Recent Progress Author(s): Saif Benjaafar, Sunderesh S. Heragu, Shahrukh A. Irani Source: Interfaces, Vol. 32, No. 6 (Nov. - Dec., 2002), pp. 58-76 Published by: INFORMS Stable URL: http://www.jstor.org/stable/20141207 . Accessed: 29/07/2011 09:03 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at . http://www.jstor.org/action/showPublisher?publisherCode=informs. . 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INFORMS is collaborating with JSTOR to digitize, preserve and extend access to Interfaces. http://www.jstor.org Next Research Layouts: Factory and Recent Progress Generation Challenges Sunderesh Saif Benjaafar Department Engineering, Irani ofMinnesota, University and Engineering Systems, Rensselaer Polytechnic Institute, Troy, New York 12180 Columbus, Ohio 43210 of Industrial and Systems Engineering, Ohio State University, irani.4@osu.edu herags@rpi.edu saif@ie.umn.edu of Decision Department ofMechanical Engineering, Department 55455 Minnesota Minneapolis, in Industrial Graduate Program Shahrukh A. S. Heragu Sciences This paper was refereed. the needs do not meet that existing trends in industry suggest layout configurations a need for a new generation of is and that there of multiproduct factory layouts enterprises most of the academic literature and easy to reconfigure. Although that are flexible, modular, assumes on layout design that is based on a deterministic requirements production paradigm focuses are known of research far in advance or change very little over time, a growing body Recent on designing carried being environments. and uncertain layouts for dynamic on Next out by the newly formed Consortium universities involves multiple which consortium, (NGFL). The alternative veloping ible and reconfigurable (Facilities-equipment is an emerging There out configurations layouts, new factories. planning: consensus do not meet performance that existing lay the needs of multi and there is a need for a new gen product enterprises eration of factory layouts that are more flexible, mod to reconfigure (Askin et al. 1997, ular, and easy and Huang 2000, Irani Sheikhzadeh and 2000, Benjaafar Kochhar Research creased and Heragu 1999, National 1999, Montreuil in Council 1998, Yang and Peters 1998). With and reconfigurability, modularity, flexibility, their each could avoid layouts redesigning time their production changed. Creating requirements new layouts can be expensive and disruptive, especially shut down. Because factories that when factories must new or introduce in volatile environments operate regularly cannot afford frequent disruptions, products factories the inefficien often prefer to live with plant managers suffer than cies of existing layouts rather through costly In our obsolete. become which may quickly redesigns, work with over 20 companies Interfaces, Vol. 32, No. 6, November-December in the last five years, we ? 2002 2002, pp. 58-76 and new methods metrics, layout. Manufacturing: An example is the research Generation Factory Layouts is de and several companies, performance-productivity, for designing flex strategy.) frustration with existing in that offer companies particularly layout choices, many products with variable demand and short life cy value cles. These companies layouts that retain their have encountered mounting or can easily be are layouts that permit Equally important reconfigured. and a greater de lower lead shorter inventories, times, gree of product customization. usefulness over many product mixes as product, process, and layouts, such meet not these needs. They are typ do layouts, a for specific product mix and produc ically designed to continue for a suffi that are assumed tion volume Conventional cellular ciently long period criterion evaluation three to five years). The (usually, in most used layout design proce material-handling dures?long-term capture the priorities of the flexible to efficiency?fails (for example, factory than scale, responsiveness is more scope important more is than cost, and reconfigurability is important more than efficiency). Consequently, layout important INFORMS 1526-551X 0092-2102/02/3206/0058$05.00 ISSN electronic BENJAAFAR, HERAGU, AND IRANI Factory Layouts (a) Functionallayout Figure 1: In a functional layout, resources layout, are partitioned (b)Cellularlayout resources of the same each into cells, as product volumes, mix, or deteriorates performance (Afentakis et al. 1990, Braglia et al. routings fluctuate Lahmar and Benjaafar 2002, Norman and forthcoming, et al. 1992). A static measure of to material-handling capture the im efficiency also fails on of pact layout configuration aspects of operational Smith 2001, Palekar such performance, as accumulation, work-in-process and through queue times at processing departments, rates. put Consequently, layouts that improve material cause often in the elsewhere inefficiencies handling form of long lead times or large in-process inventories (Benjaafar 2002). When product is high or production vol variety are small, a functional layout, with all resources of the same type in one location, to is often thought a the 1). However, provide greatest flexibility (Figure umes functional is notorious layout and inefficiency lead to long tories, Jacobs and for its material-handling can which complexity, scheduling lead times, large work-in-process inven and inefficient material handling (Flynn and and Chames 1986, Shafer 1988, Montreuil 1999, resources and Greene 1993). While grouping Sarper based on function simplicity provides in allocating some economies workloads, Interfaces Vol. 32, No. 6, November-December 2002 of scale it makes 59 in the same type are placed to a family of products. location, while in a cellular dedicated the to manufacturing inefficiencies layout susceptible when in product mix or routings. there are changes Such changes often require a costly redesign of the or the plant layout system material-handling (Yang and Peters 1998, Lahmar and Benjaafar 2002). to a functional An alternative layout is a cellular con in which the is into cells figuration, factory partitioned to a family of products with (Figure 1), each dedicated similar processing 1994). Al requirements (Heragu can cellular factories work flow and though simplify handling, they are generally designed a specific set of to produce demand products whose levels are assumed to be stable and product life cycles are In cells to dedicated fact, sufficiently long. usually reduce material families with single product cell flows. Cellular factories little allowance for inter are inefficient when de or new products for existing products fluctuates are introduced often (Benjaafar 1995, Askin et al. 1997, mand Irani et al. 1993, Suresh and Meredith 1994, Wemmerl?v and Hyer 1989, Wemmerl?v and Johnson 2000, Heragu et al. 2000). Some authors have proposed alterna structures tive cellular to overcome these problems, such with as cells (Irani overlapping machine sharing (Benjaafar et al. 1995, 1993), Suresh cells and BENJAAFAR, HERAGU, AND IRANI Factory 1999, Ven 1994), and fractal cells (Montreuil an improvement, these et al. 1997). Although cellular their bounded remain alternatives by Meredith katadri structure. for functional or whether Layout design procedures, cellular layouts, have been largely based on a deter as product ministic Such design parameters paradigm. and product mix, product demands, routings are as to be known with (Meiler and Gau certainty and Smith Norman 2001, Benjaafar 2000, Kochhar 1996b, and Heragu 1999). The design criterion is often a static sumed measure of material-handling total score, cency (a total adja efficiency or cost, material-handling a combi does not capture the need for of both), which and reconfigurability (Benjaafar 2000, 2002; flexibility and Heragu Kochhar 1999; Braglia et al. forthcoming). nation In fact, the relationship and layout flexibility and analyt understood are lacking. The struc between is poorly layout performance for its evaluation ical models their flexibility and Webster (Bullington and Sethi Sethi 1980, 1990, Tompkins 1987, Gupta 1986, and Tyberghein Webster 1980). Current design criteria do not capture the effect of layout on such performance tural properties are also not well of layouts understood that affect as congestion, cycle time, and throughput rate. They also ignore the impact of such operational as setup, batching, and loading and un parameters measures loading at work sure only average performance under effectiveness guarantee we Clearly, tion criteria, need they mea important, and in so doing cannot centers. More a new and new class design scenarios. all operating of layouts, models new and evalua solution procedures. Literature Review as an academic Facility layout has been formally studied area of research since the early 1950s. Balakrishnan and Heragu papers namic and Gau (1996a), and Kusiak and (1987) survey their vast literature. We focus on to the design of layouts in dy that are pertinent (1998), Meiler Cheng environments. the design of lay authors have addressed mix vol and demand in settings where product it to these In vary from period settings, period. the to reconfigure the layout when be possible Several outs ume may Layouts there may be changes are sufficiently large, although costs. infor demand associated Assuming re-layout for each period is available at the initial design mation stage, the objective riod such that both costs is to identify a layout for each pe and re-layout the material handling are minimized over the planning horizon. This the facility-layout dynamic problem the Hicks and Cowan (1976) incorporated problem. a in costs of relocating analyzing single departments was first to develop Rosenblatt (1986) period problem. is often a formal model called and an optimal solution for procedure for multiple His periods. optimal layouts determining cost as well as the model considers material-handling cost of relocating departments from one period to the next. Since then, a number of researchers, including Batta (1992, 1998), and Balakrishnan (1987), Urban on Rosenblatt's solution procedure. improved as and Venkatramanan such (1994), Others, Conway and Enscore Kochhar and Heragu (1999), Lacksonen (1997), (1993), Urban (1993), and Kaku and Mazzola et al. heuristics. Balakrishnan (1992), proposed (1993), et al. (1990), and Kouvelis and Kiran of the basic dynamic layout lem. Montreuil and Venkatadri (1991) assumed by the designer goal for the last period is provided a model that uses this goal layout as developed intermediate and put layouts for the provides Afentakis studied (1991) variations A mediate limitation of prob that a and an in inter this ap planning periods. are of departments proach is that the relative positions their with fixed over all the planning only periods, to vary. Balakrishnan sizes and shapes being allowed a comprehensive review of and Cheng (1998) provide on the papers facility-layout dynamic problem. in product mix and where In environments changes are frequent or where demand volumes re-layout costs a are high, a plant manager may prefer layout that is demand robust under multiple scenarios, production and most for example, likely. pessimistic, optimistic, not be the for any of the optimal layout may Although it is robust in the sense that it is suitable scenarios, the and Lee (1987) introduced under each. Rosenblatt in analyzing single period elaborated by Rosenblatt work and Lee of Rosenblatt The (1992). Kropp on that of Shore builds and Kropp Rosenblatt concept of robustness outs. It was further Tompkins of layouts lay and and and the design (1980), who were first to consider et al. (1992) Kouvelis under uncertainty. Interfaces 60 Vol. 32, No. 6, November-December 2002 BENJAAFAR, HERAGU, AND IRANI Factory present heuristic outs for multiple strategies for developing periods. Palekar robust lay et al. (1992) planning in determining uncertainties plant explicitly a stochastic layout dynamic layout. They formulate are known: the following (1)mate assuming problem for several periods, and rial flows between departments consider (2) the probability to another. They of transitioning solve the model from one flow matrix using dynamic pro for large and heuristics for small gramming problems ones. Kochhar and Heragu (1999) describe an algorithm for single- and multiple-period-dynamic-layout prob costs. layout changeover for devel (1998) present a method on the are based Flexible layouts. layouts lems that considers and Peters Yang oping flexible notion that layouts neither remain static for multiple In planning periods nor change during every period. stead, a layout may remain static for a block of periods, at the end much the production layout is necessary. of which that a new has changed The so de layout to must when and decide how change the lay signer out. Assuming and their probability the flow matrices are known of occurrence the de periods, of for which the block periods static. He or she then solves the for multiple signer first determines a layout is to remain for each block of periods and combines layout problem a layout plan for multiple the results to produce pe that and LaForge (1992) also assume of oc future production scenarios and their probability currence are known and propose for another method riods. Montreuil layouts. Like Montreuil multiple-period developing a limitation of this and Venkatadri's (1991) approach, are of departments is that the relative positions method and only their sizes and shapes fixed for all periods can vary. To address the limitations that come from fixed de that proposed stra and be departments duplicated the plant. Duplication throughout tegically distributed mean ca not necessarily additional would acquiring pacity but could be achieved simply by disaggregating partment functional locations, several authors should which may consist of several existing departments, et al. into smaller ones. Montreuil identical machines, or a holo (1991) suggested distributed, maximally are in functional which departments layout graphic, into individual which machines, fully disaggregated are then as far from each other as possible placed Interfaces Vol. 32, No. 6, November-December 2002 61 to Layouts maximize showed coverage. that, while are desirable, (2000) Benjaafar and Sheikhzadeh some disaggregation and distri full disaggregation and distribu bution tion are rarely justified. In fact, the benefits of disag diminish with most of the and distribution gregation of each benefits achieved with only a few duplicates also showed department. Benjaafar and Sheikhzadeh about that, even in the absence of reliable information the simple fact of hav the plant can signifi ing duplicates placed throughout robustness. Drolet (1989) improve layout cantly can to form used be showed how distributed layouts to particular virtual cells temporarily dedicated job or and Benjaafar ders. Lahmar (2002) extend Benjaafar and routings, volumes product and Sheikhzadeh's to problems with (2000) approach costs. Askin and consider relocation multiple periods to compare the holographic and (1999) used simulation et fractal layouts proposed Montreuil respectively by et al. (1997). al. (1991) and Venkatadri of have the shortcoming Several of these approaches data for future periods. production associate a probability of occurrence that with each production scenario implicitly assume resources and remain the production quantity) (type known assuming Even authors who In fixed. today's take place environment, drastic production equip changes frequently. Manufacturing ment is regularly and new decommissioned ment know Plant often managers deployed. in product mix and demand before a new production cycle changes slightly reasonable equip about volumes starts. only It seems and facility designers not for plant mangers to look beyond the next period and instead develop layouts that can be reconfigured quickly and without cost to suit the upcoming much period's production and Kochhar (1994) discussed requirements. Heragu in materials and this idea and argued that advances as such processes, lighter composite manufacturing with excellent vibration materials proper absorption ties and tools chines lighter machine ma to companies reconfigure Kochhar and Heragu frequently. laser cutting, allow that will easily (1999) present ated dynamic and point a genetic towards algorithm to solve the associ layout problem. Layout Classification In view of the above proaches to design discussion, of factory we can classify ap for dynamic layouts BENJAAFAR, HERAGU, AND IRANI Factory into two categories: (1) layouts that are or scenarios, for multiple production periods to and (2) layouts that are flexible or modular enough to meet with minimal effort be reconfigured changed Layouts (1997), who argued that the con of average travel distances is indeed as mea of operational performance, environments includes Fu and Kaku robust ventional measure assumes The first approach requirements. is the production data for multiple periods so at the initial design that available itself the stage can identify a layout that is robust (and designer over causes minimal materials handling inefficiency can de all) over the multiple periods; or the designer production that either a layout with inherent features (for example, du of key resources at strategic locations within plication ensure material the plant) that will reasonable velop handling efficiency through riods. The first assumption the various suffers pe production from the fact that be available at the outset, which in a dynamic environment. fea Designing tures that allow future flexibility is more promising. the research in this area remains limited. However, The second approach assumes that layouts would be production is unlikely reconfigured to minimize reasonable data must after each period and should be designed reconfiguration material-flow efficiency to evaluate layouts. Most models those that deal with dy and the cost of revising for future periods can choose among the layout, facility designers four A of useful is (Table 1). types layouts dynamic layout in the production when uncertainties data are low and cost of re-layout A robust is modest. in production able when uncertainty are costs high. A distributed re-layout able when on measures of expected sum of weighted et al. (1992), have used a robust not on mean performance, but on to guarantee for each performance a layout's ability or under each scenario. Others period criterion and variance combined mean layout is desir cost are both and uncertainty re-layout a high, while layout is more appropri reconfigurable ate when costs are low but uncertainty is re-layout have used light new important transform it.We trends are emerging the in industry that or even problem layout design focus on five of these the interaction new between and technologies, Contract in Industry Trends Emerging trends business to high practices, layout design. Manufacturing are outside industries, suppliers increasingly most of the manufacturing and assembly for doing manufacturers (OEMs) (Gibson original equipment 1999). Along with just-in-time deliveries, 2000, McHale outsourcing has led to firms reconfiguring their final Uncertaintyof FutureProductionRequirements Cost of re-layout Low High a Low Dynamic layout Robust layout High to minimize and in performance, for example, Norman considered A authors have few (2001). opera as an evaluation criterion. This performance fluctuation tional layout is prefer data is low, but In many efficiency?a incurred by the material-handling sys and Gau candidate (Meiler layouts evaluating and Lee such as Rosenblatt Some authors, (1987) and Kouvelis ness criterion based, Smith those degree ume data eliminate As with alternate literature, including environments, rely material-handling travel distances 1996b). from effort. average material-handling a practical point of view, upon the depending in the production mix and vol of uncertainty From could layouts is and 2000). (Heragu Zijm environ Methods for designing layouts for dynamic ments could also be classified based on the design cri tem?in different that minimize Several still limited in the be very high. guaranteeing in each period. To so that re-layout costs are always minimal. flexible layouts, research on reconfigurable namic can sometimes criterion cost while need knowl carry out this balancing, designers would all of for future edge production periods. An alterna tive is to design reconfigurable features into the layout teria used a good predictor in process. Ben sured, for example, by expected work that this is not always the case. jaafar (2002) showed as a Layouts designed using operational performance Reconfigurablelayout Distributed layout Table 1: The choice of a layout type depends on the uncertaintywith respect to future production requirements and the cost of re-layout. Interfaces 62 Vol. 32, No. 6, November-December 2002 BENJAAFAR, HERAGU, AND IRANI Factory facilities to accommodate closer coupling be assembly tween suppliers and OEMs. For example, many auto mobile manufacturers to deliver com allow suppliers to points ponents directly lines. They have designed of use on their assembly loading docks and multiple their inventory drop-off points throughout The new Cadillac plant in Lansing, Michigan, multiple factories. to maximize for example, is T-shaped to the factory floor. Some automobile supplier access manufacturers, such as Volkswagen to (VW), are allowing suppliers some or out assem all of the and carry manufacturing Brazil bly on site. The new VW truck plant in Resende, is a showcase for this modular To sup plant concept. are using spine layouts port modular plants, designers a main ar the product moving along to the Linked the spine plant. through are mini-assembly lines owned by the suppliers, each to the moving its own module attaching product. The Layouts trucks and conveyors. Facility planners had to choose efficient not only layouts that make material handling in each individual the complex. plant but throughout The picture that emerges from the above cases is of The layouts with fixed cores and variable peripheries. a for is to then challenge facility planners develop lay out and a material-handling system to permit high ef and reconfigurability ficiency at the core and flexibility at the periphery. The design metrics should certainly on the area of the depending plant, but the a should also design support variety of layout same we within the The modular types facility. layouts in con discuss later address of part the challenges be different tools structing such hybrid (Figure 2), with tery, or spine, hybrid layout has features of a flow autonomous cells. The configuration to add and main remove suppliers line and multiple, allows the plant without changing accommodates It also the the layout. gracefully and contraction of Trotter, growth supplier operations. of exercise has used Inc., a manufacturer treadmills, in similar its plant ideas 1995). (Assembly Magazine Other have chosen to col?cate in companies suppliers a single large complex. The GM Gravatai plant in Brazil, for example, houses a final assembly plant and 16 sup Lear, plier plants, including plants owned by Delphi, and Goodyear, which to GM's line workers are within through deliver modules preassembled 17 plants The 2000). (Wheatley are connected distance and walking a shared material-handling system of forklift Delayed layouts. Product Differentiation product variety and the need for mass cus has led many to delay product companies differentiation and Lee 1997, Lee and Tang (Feitzinger the point 1997, Gupta and Benjaafar 2002), postponing Increased tomization in the manufacturing are as process when products individual features. do this, for ex signed Companies a common to all ample, by building platform products and differentiating it by assigning to it certain product features and components specific only after actual de mand known. create becomes facilities They hybrid of flow-line-like where consisting components they common build the com and platforms job shop-like the products. If final ponents where they customize are easily into families, the job-shop grouped could be replaced by cells, each dedicated to one of the product families (Figure 3). Taken to the can eliminate differentiation the extreme, delayed products structure For example, problem of designing layouts altogether. if customization takes place at the point of sale or in as is distribution the case for warehouses, increasingly computers (Lee and Tang line. single high-volume, has Hewlett-Packard production low-variety such a strategy by implemented carrying out the localization steps for its computers and printers in its overseas distribution centers (for ex its distribution warehouses install ample, country /77 Supplier's production line Figure 2: Ina spine layout, productsmove along a main artery through the plant. Linked to the spine are mini-assembly lines owned by inde pendent supplierswho attach additionalmodules as needed. Interfaces Vol. 32, No. 6, November-December a 1997), the factory becomes 2002 63 specific power The blurring manufacturing supplies and power of the lines between raises interesting cords). warehousing questions. How and does BENJAAFAR, HERAGU, AND IRANI Factory storage facilities affect their de light assembly change to sign? How should the layout of warehouses both the needs of efficient storage and accommodate from pure warehouses transforming to facilities that also do efficient Meiler and Klote and assembly? that introducing value-adding In indus affects warehouse design. manufacturing (2000) showed operations tries where indeed steps are carried out in side the factory, there is clearly a need for design tools that support hybrid layouts that may have the features the differentiation of product, cellular, and functional layouts all under we one roof. The modular later could discuss layouts be a step in that direction. Layouts describes executive lots moving production duction points as "small the production process to any of the standardized pro on the parallel production lines, passing to break bot it is necessary line to wherever Sun tlenecks and keep products Microsystems rolling/7 uses a similar concept for its line of desktop worksta from one facility has three identical cell has two mirror image sides, turned on or off, giving Sun up to six tions Sun's (Feare 1997). lines or cells. Each can be which lines. As production parallel long as flow and patterns parallel routings do not change significantly, product and linear production lines, similar to those at EFTC or Sun, would and reduce cycle flexibility provide time. Multichannel Other Manufacturing on quick-response manufac emphasis and minimum inventory has led finished-goods turing to invest in addi and suppliers many manufacturers The increased bility uted have companies transforming by achieved multichannel flexi into distrib functional layouts large functional tional depart layouts, disaggregating into two or more distributed subdepartments in the plant. Duplicating departments throughout pagers an efficient of finding path of for each Other job. examples through distributed layouts include the fractal layout configu et al. (1997) inwhich rations introduced by Venkatadri capacity, often by running parallel production a in Newark, lines. For example, Solectron, California, a with 24 has pro plant large contract manufacturer, from lines capable of assembling duction everything to laser printers 1998). By having du shared across prod a seamless flow of ma (Engardio lines production flexible plicate ucts, companies hope terial. Depending to ensure on downstream congestion, can move in and out of neighboring produc creating multiple paths, or channels, mini and congestion. EFTC, a manufac mizing queueing also uses turer of electronic goods and components, An EFTC multichannel 1999). (McHale manufacturing products tion lines, JZq_r~]_T~l_ Product A Undifferentiated ^HHH] production Product Px HDHZHIhProduct p2 Q-CH>Product* platformPH stage Product PA ro-o-o LQ?Q?Q_ < Product customization Product P5 the products based on actual demand undifferentiated the plant makes it customizes In the second stage, (make-to-order creases the likelihood the system a plant into several is partitioned can be allocated which workloads cells identical to De dynamically. face such systems challenges signers as determining how many duplicate paths to have and on the plant the resource duplicates how to organize of multichannel floor. Scalable Machines effort In the last few years, there has been a concerted to that in the metal cutting industry develop machines are highly flexible and scalable and that can perform functions and be adjusted for various capacities. many can of the machines and efficiency functionality in additional modules by plugging easily be upgraded or acquiring The multinational software. additional The on Intelligent Manufacturing (http: Systems is leading such an effort, supported //www.ims.org) a of Japanese, US, and European ma by conglomerate Initiative stage Figure3: A plantwith delayed differentiationhas a hybrid layoutconsist In the first stage, ing of two stages. a fashion. in make-to-stock products ments production). chine Science (Ikegaya 2000). The National on Reconfi Center Research Engineering tool makers Foundation at the University gurable Machines of Michigan (http: Interfaces 64 Vol. 32, No. 6, November-December 2002 BENJAAFAR, HERAGU, AND IRANI Factory is carrying out a parallel ef //erc.engin.umich.edu/) on machines that can be quickly fort, focusing building in product mix or volumes, for for changes adjusted can be machines by adding example, quickly upgraded or controllers (Koren et spindles, axes, tool magazines, al. 1999). If successful, such efforts could lead to facili ties that use one machine for most processing with lit a ma movement. and Because tle material handling for different mixes and chine can be rapidly configured in would volumes, requirements production changes have little effect on layout. A commercial that already has some of product is the TRIFLEX machining these capabilities center, marketed by Turmatic multaneous units with Systems. The center allows si using up to seven machining machining additional the possibility of retrofitting un loading and can into similar or be integrated loading systems and unit different machine systems. A single machining can be fitted to a long base slide, enabling the sides of ones. It can accommodate automatic a workpiece in one station and the to be machined front face in another. Therefore, five-sided machining even with only two machining units fitted. could transform scalable machines layout de movement If material became minimal, factory sign. and would their be design greatly simplified layouts is possible, Such in factory design less important. Emphasis would then likely shift from the detailed design of each to the higher level integration processing department would of be these departments with assembly chining and packaging). (for example, or assembly integrating ma with inspection Layouts that can be moved with a pallet jack from any side. is small enough to fit through most doors, its rigid frame does not require releveling after are available for electrical move. Quick disconnects machine and heavy is a compact and mobile mill westernindustries.com), It used for small-lot, ing machine job-shop machining. can be located close to the primary machining or turn a family of parts that requires producing or on other ma operations secondary preliminary of the machine is a base casting chines. The foundation ing centers Interfaces 32, No. 6, November-December 2002 65 are stationary (that is,workpieces is incurred by the machines). Hence, fac have to be laid out to facilitate the flow of around tories would machines of parts. Telecom's instead In Northern for manufacturing neric, in Calgary, facility business modular, ge can cells work from one be moved Canada equipment, telephone conveyor-mounted ily and quickly eas to another location cells can 1996). These independent (Assembly Magazine be unplugged line and moved from the main assembly to accommodate With different products. frequent in the the facility uses design, changes product to change tooling and and assembly production cells work conveyor-mounted to suit layout the new requirements. tools require storage and retrieval. to allow is being developed technology For ex and retrieval of large equipment. Portable machine Fortunately, easy storage ample, Robotic Parking (www.roboticparking.com/ a modular automated tech.html) markets parking sys tem (MAPS) that integrates with control computer lifts, pallets, large equipment facilities Complete carriers parking garages, inmanufacturing to park modular can be constructed as 60 by 60 feet, up or underground. to 20 stories, "picked in a MAPS-like from the shelves" and facturing facility. The shift to lighter machines vances creasingly on lots warehouse floor. Depending manufacturing and demand, machine tools would mix re ware and above to the main product and for designed Although originally is finding applications the technology and warehousing. Portable machines could be maintained cent and in multilevel as small are marketing and dynamically por equipment de that are easily table machines areas as in different of the factory production ployed TRAK The QuikCell QCM-1, requirements change. from Southwestern Industries available (www.south Vol. tools for repairing turbines, paper machinery, The portable machines go to the equipment. on the workpieces?instead of and mount workplace the other way and movement houses. manufacturers each sup an a air and draw bar, sprayer, power ply, Tools (www.cpmt.com) hose. Climax Portable Machine that have the capabilities of stationary makes machines trieve Several and a coolant mechanical Portable Machines The machine in materials. inserted adja on is also driven by ad are in For example, composites choice for many components. the primary be in the manu BENJAAFAR, HERAGU, AND IRANI Factory can now composites replace cast iron parts are aluminum parts. These phenolics replacing can also be engineered to have excellent light materials as such heat resis mechanical hardness, properties, Aluminum and tensile tance, vances and vibration strength, in nonabrasive Ad absorption. such processes, manufacturing are aid as laser cutting and electron-beam hardening, of lightweight machining ing the development equip ment. is also permanent magnetic Industry developing chucks that facilitate quick mounting and dismounting of tools, carry their own energy sources, and do not in ma With these developments obstruct machining. we are moving to terials and processing technology, that wards processing technologies light employ weight parts. which easily with can process lightweight in and Kochhar (1994) foresee facilities Heragu on is mounted wheels equipment lightweight in tracks embedded the floor moved shop along universal for support services, such plug points tools machine and as and coolant, gas, water, compressed dispersed itmay be With the such throughout plant. technology, feasible to change layouts several times per year. With costs cut, the criterion in designing layouts re-layout then shifts from long-term material-handling Firms would responsiveness. effi Layouts Distributed Distributed Layouts layouts disaggregate into subdepartments partments out the plant floor located strategically to hedge de large functional distributed through 4). Duplicate departments the factory allow the throughout (Figure in job-flow against future fluctuations In turn, disaggregated and volumes. and dis material-travel dis reduce subdepartments facility patterns tributed tances for many production flow sequences. Planners can easily find efficient flows for a wide range of prod uct mixes and volumes. Such layouts are especially ap too to when demand fluctuates pealing frequently the plant cost effective. reconfiguring a fixed settings, layout that performs well scenarios is desirable. demand make In these for many a distributed layout, a firm faces several create it should and How subdepartments, it have of each type? How much should In designing challenges. how many it assign to each subdepartment? should capacity it place the subdepartments? How Where should should it allocate workload similar among subdepart ments? How will department and dis disaggregation maximize affect operational (for example, performance in and work times, process, material-handling should the firm manage mate times)? How queueing rial flow, now that there is greater routing flexibility? mand How to short-term ciency cus on operational outs periodically by reconfiguring performance to relieve short-term congestion fo lay and for current products and de throughput we levels. The agile layout design methodology vision. describe later is in part motivated this by Next Generation We NSF are carrying Consortium turing plore multiple companies. alternative it coordinate should out research under on Next Generation the newly formed universities and several manufac is to ex The goal of the consortium and alternative layout configurations metrics for designing performance to layout design Three approaches tinct needs of the flexible factory. flexible factories. address three dis The first two ap present novel layout configurations, namely proaches In the third and modular distributed ap layouts. a design we use operational as performance proach, criterion to generate what we term agile layouts. the competing for ma needs terial handling of similar formance measure should What per subdepartments? the firm use when designing it measure Should expected distributed Factory Layouts Factory Layouts is supported (NGFL). The Consortium by a major Science Foundation (NSF) and grant from the National involves tribution layouts? scenar cost over possible demand material-handling a or measure it should seek of that robustness ios, guar antees a minimum level of performance for all scenar ios? More to layouts though bility, of scale must sensitive how important, the adopted performance are the final measure? Al increase flexi duplicating departments might it could also increase and diminish economies be (for example, operators and auxiliary resources The firm must trade off the duplicated). benefits and du of disaggregation in other areas. increases material-handling against cost Benjaafar and Sheikhzadeh plication Benjaafar Benjaafar (2002) and explored Sheikhzadeh (2000) and Lahmar and some of these questions. considered situations in Interfaces 66 Vol. 32, No. 6, November-December 2002 BENJAAFAR, HERAGU, AND IRANI Factory Layouts (a) Partiallydistributedlayout (b)Maximallydistributedlayout Figure4: Ina distributed layout,not all equipment of the same type (representedby a particularshape in the figure) is placed inadjoining locations. Instead,equipmentof the same type is either grouped inmultiple clusters (partialdistribution)or placed individuallythroughoutthe plant (maximaldistribution). is characterized for products by finite discrete distributions, represented by a finite number of demand-realization scenarios and probabilities of allocation of flow among subdepartments of optimal the same type. Thus, we have a combined layout and flow-allocation and Sheikhzadeh problem. Benjaafar occurrence allocation for this layout-flow (2000) describe a model as as an well effective decomposition solu problem, tion procedure. Lahmar and Benjaafar (2002) extend which demand for each may be independent scenarios consisting scenario. Demand or correlated. Both for products cases result in com of different product-demand each with its own probability of occurrence. binations, The distributions data or may be based on historical on forecasts. When the demand distributions are dif one can assign equal likelihood to characterize, one to all possible demand scenarios. Alternatively, can aggregate into a smaller subset that the scenarios ficult the range of possible demand scenarios. represents From the distribution of demand the scenarios, unit and the transfer loads, product routings, product we determine amount for each possible demand scenario the for each product that will flow be of material tween each pair of departments. from-to flow matrix tiproduct This results in a mul for each demand sce is to select a layout that minimizes cost over the entire set of material-handling nario. The objective expected scenarios. For each scenario, we need to determine Interfaces Vol. 32, No. 6, November-December 2002 67 the to settings with procedure can the be multiple periods, layout reconfigured at a cost at the beginning of each period. (2000) and Lahmar and Benjaafar and Sheikhzadeh's the model and the solution where with distributed (2002) experiments Benjaafar's lay and outs, using both randomly generated examples data collected from industry, showed firms could ben efit from disaggregating and distributing functional in most 40 (over departments percent improvement the cases). Distributed greatest advan layouts provide is variable, particularly for layouts tage when demand or with many large departments types. If department can be a the distribution of flow patterns categorized at the design priori, including flow information stage can improve layouts. However, material-handling costs can be reduced even without flow information BENJAAFAR, HERAGU, AND IRANI Factory (for example, by distributing subdepartments of distributed the quality Furthermore, domly). to inaccuracies in the demand outs is insensitive ran lay dis important, firms can obtain most of the with few rep from duplicating departments to fully disaggregate functional rarely having tribution. More benefits licates, layout that distributes department replicates can also help a firm to han the plant floor throughout short runs or products with dle products with life cycles. It can do so, for example, by quickly short form of adjoining subde cells, consisting ing temporary or job a to line dedicated particular product partments, once the prod order (Figure 5). This cell is disbanded out or once the customer order is com is phased are then free to par The individual replicates pleted. such in new cells. Drolet (1989) discussed ticipate virtual cells. Lahmar and Benjaafar (2002) found that uct can be useful in handling configurations contraction For ex and gracefully. growth production over several periods, mature when products ample, its facility repeatedly the firm can avoid redesigning distributed to accommodate product growth machines a distrib by using to the periphery of can then grow almost layout and adding the layout as needed. The facility in a concentric fashion, keeping layout uted oboio QOOE ^O^o this efficient material and maintaining handling. With can modify in incre firm the small capacity approach, or removing ments takes since introducing capacity core at with the the remaining factory place periphery intact. Modular departments. A Layouts space compact Modular tions. are hybrid layouts for systems with as flows that cannot be described flow line, or cellular. Several of the emerg in industry are leading to such configura layouts material complex functional, ing trends For modular the automobile industry builds example, cores with around flow-line-like factories forms. lines in various supplier production also use lay that delay product differentiation and cellular fea that combine product, process, connected Firms outs first to introduce Irani and Huang (2000) were of basic modules. the concept of layout as a network at least in the short term, a known They assumed, mix and fairly stable demand. As the mix and product tures. demand others some modules change, such modular added. With turers can scale their research their activities on modular layouts, In up or down quickly. Irani and Huang layouts, provide a metastructure for designing multi in general? Would facilities cor resources into modules manufacturing and arranging grouping to specific traditional responding tal flow Virtual cells and manufac to answer the following fundamental sought a Could questions. layout other than the three tradi flows of multi tional layouts better fit the material a combination of the manufacturers? product Perhaps a network of Could three traditional layout layouts? product O o are eliminated (2000) modules ^o Layouts distances layouts minimize to or costs? a modular Irani and Huang (2000) designed layout a The for Motorola company wanted facility (Figure 6). to assess the feasibility of changing the layout in one of their semiconductor fabs from functional to cellular. seven bays (or process layout comprises im film deposition, diffusion, etching, departments): and backend. Mo metrology, plant, photolithography, The functional Figure5: A distributed layoutcan be used to quickly form temporary(vir tual) cells, consisting of adjoining subdepartments,dedicated to a partic ular product line or job order. The cell is disbanded once the product is phased out or once the customer order is completed. four product torola provided routings representative found that a of the fab's product flows. The authors it would not be viable because cellular layout would How and processes. equipment require duplicating the of ever, a visual string-matching routings analysis Interfaces 68 Vol. 32, No. 6, November-December 2002 BENJAAFAR, HERAGU, AND IRANI Factory Layouts Functional Layout Module Function Process with ETCH Flowline Process 1) -O -J?2.08 Module with Function ETCH 2.10 \ \?*/2.09 j?*( Module Flowline with PHOTO Process Function / 3.08 r> 6-04 v y- ) j Functional Layout Module with FILM Function Process (z V (" ) -O Cell Module Functional Flowline Module with DIFF Process Layout Module with Flowline Module with Process Function BACKEND with ETCH, ETCH, IMPLANT and PHOTO FILM and PHOTO Process Process Functions Functions Funtion Figure 6: The original functional layoutof theMotorola semiconductor fabwas decomposed intoa networkof layout modules. Each layout module consists of several dissimilar machines connected by a particular flow pattern. revealed that different pairs of routings had substrings of operations identical or had many opera that were common. tions in Based on this observation, they de Procedure Design for Modular Layouts the three (Figure 6) that combines consec In this all of layouts. layout, pairs are in all the product utive operations per routings or in adjacent mod formed in the same layout module that material flow in (2000) showed can into a be any multiproduct facility decomposed network of layout modules, each module representing a A is the of module of machines group part facility. a is a group of machines ules, where layout module whose flow pattern is characteristic of a traditional lay out. The authors have since studied samples of product from published data from industry routings obtained connected signed a traditional and new found substrings layout that product of operations routings often have common into that could be aggregated Interfaces 32, No. understood 6, November-December 2002 69 a well a material-flow network with by its flow pattern and method for designing and cell the flow-line (Figure 7). For example, have a part family focus. The flow-line mod are identical, whereas the ule aggregates routings that layout modules cell module chine modules. Vol. Irani and Huang aggregates routings In contrast, sequences. that have the similar ma functional layout BENJAAFAR, HERAGU, AND IRANI Factory Layouts ?. AMIJr~ M1 M4 A M3 -H M2 M5 -?fwn?{W? ~MT1?{M~0 (a) FlowlineModule (b) Branched Flowline Module (d)Machining Center Module (c)CellModule M2 M4 ?*~ M1 M3 M M5 (f) Patterned FlowModule (e) Functional Layout Module Figure 7: Six types of layoutmodules based on flow patterns observed in traditional layoutconfigurationsand various graph structures. is a group of machines that do not process the material products with similar routings. However, in its from-to chart could correspond to flow pattern an an assembly as or in acyclic digraph, disassembly module line or, in the worst case, a completely extracted. digraph. In the ideal pletely would connected be com each product would solution, on a flow line, but that dedicated processed in equipment. A entail significant investment practical approach would of consecutive operations be to maximize the number in a family of routings that are performed in the same module. To find such a Irani and Huang the (2000) employed structure, in and clustering used method of string matching ge netics, molecular of this approach in a product strings and residual substrings routing. A common substring consists of consecutive operations that two or more in com have sequences operation mon. Residual substrings are the of opera substrings are tions that remain after all the common substrings and biology. At the core chemistry, are the concepts of common sub For in operation example, and Sb(1^2^5-6-7-8), sequences the com Sa(l-?2-+3-+4^7^8) mon are l->2 and 7->8. The residual sub substrings are 3->4 and 5->6 in and Sa Sb, re sequences strings Given the of for products spectively. routings sample in the facility, Irani and Huang (2000) all the common between substrings pairs of routings. Next, the frequency with they compute which each common substring occurs in the routings. manufactured first extract then aggregate similar substrings and for module each cluster of layout substrings. They create Finally, Interfaces 70 Vol. 32, No. 6, November-December 2002 a BENJAAFAR, HERAGU, AND IRANI Factory they eliminate machine modules utilization or that do not meet constraints on machine for criteria alloca tion and duplication modules. The among multiple a result from is this using typical approach facility lay out that is a network of dissimilar modules. In the ex cess batch 2000), the layout consists ample (Irani and Huang cell module flow modules (M2), two patterned (Ml, a a and flowline functional module module M4), (M3), (M2) (Figure 8). outs could formance that permit frequent reconfiguration, lay to maximize be designed per operational rather than to minimize material-handling tween measures operational performance and cellular manufacturing systems. Procedure capturing layout configuration is difficult. Meiler performance over viewed times. The material-handling server in moving material arrival ments. ample, automated be relationship and operational system forklift transporters (1996a) re and found figuration, 150 papers on factory layout one paper on the subject. Recently only Benjaafar an analytical model introduced (2002) capable of cap Layouts trucks, material human devices con by the layout In and product demands. travel-time distribution, product routings, the transporter for both empty and full trips made transport devices. the model, he showed Using tion does indeed have a direct in often performance, unpredictable by the that layout configura impact on operational For ways. exam can cause empty travel to in turn, can increase congestion and in lo delays. Thus, placing departments neighboring even no material flows between cations, though directly them, may reduce empty travel enough to reduce over ple, minimizing increase, which, 1 operates (for ex and operators, distances material of discrete The vehicles). guided travel are determined system among depart that the material assumes determining he accounts between turing the relationship layout configuration and operational He embedded the model performance. Module (2002) consists Benjaafar handling the and Gau of functional for Agile as a central as cycle time, (WIP) accu work-in-process and throughput become impor especially mulation, tant. Unfortunately, et al. (2000) expanded Benjaafar's Heragu to include set-up time, transfer, and pro a method size and developed that can esti To capture the effect of layout on operational perfor mance metrics, such as cycle time, WIP, and through the manufacturing (2002) modeled put rate, Benjaafar a as central-server network and each facility queueing as a multiserver queue with processing department and inter of product-processing general distribution cost. As production-planning shrink, factories periods to short shift their focus from long-run cost efficiency term responsiveness and agility. Such performance measures the design cri of operational mate Design Layouts In facilities in a layout-design in which procedure can one measures terion be of several performance. (2002) model of a Agile Layouts all use full travel of the material-handling system. travel to and from departments empty those visited ments close flows between most together, them, For example, is highest for these depart Placing there may be no direct although could significantly reduce empty frequently. travel. Likewise, with high inter placing departments flows far apart may be beneficial (Figure 9). a in showed (2002) that, Benjaafar general, design material Figure 8: The original layoutof the facility has been decomposed intoa networkof different layoutmodules with minimum intermodular material flows. Interfaces Vol. 32, No. 6, November-December 2002 71 on average is a poor In fact, a layout indicator of operational performance. that is optimal with respect to full travel could be op infeasible infinite (that is, it could produce erationally criterion based travel distances BENJAAFAR, HERAGU, AND IRANI Factory two layouts that are op Similarly, to full travel could have vastly dif Because conventional approaches WIP accumulation). timal with respect ferent WIP values. tend to optimize Layouts the average traveled by the not account for the do system, they material-handling in these distances. variance Distance how variance, a how much determines ever, partly congestion layout exhibits. More important, itwas shown that congestion increase overall that -^3 distance -8+ is not necessarily in the average distance monotonie traveled by the material-handling system. A layout that reduces average distances but increases variance could -2+ -6 congestion. Similarly, even if it increases 4+ 1fr ^9 (a) Layout = /,: uempty 0.679, ?/M = (b) Layout = /2: ?ye/77^ 0.542, ufull 0.311, WIP = 99.00 0.409, W/P = 19.41 a layout average reduces variance, In practice, travel distances, could reduce congestion. on the material travel-time often depends variance is auto system when handling material-handling to mated. Therefore, need pay special atten designers tion tomaterial that minimize handling configurations not only (Figure mean but also variance of travel distances 10). the importance of these indirect effects, Realizing are many companies designing layouts that minimize dimensional and reduce empty travel. asymmetries For example, Volvo designed its Kalmar plant in Swe den as a collection material of hexagon-shaped modules where in concentric lines within each module flows et al. 1996). Lucent is experimenting with (Tompkins are in which lo shared processors layouts centrally in functional and are equidistant departments from multiple dedicated cells within the plant. Varia a tions of the spine layout, with departments along common in indus corridor, have been implemented tries ranging to auto from electronic manufacturing cated motive assembly (Tompkins et al. 1996, Smith et al. that minimize dimen 2000). sional configurations and reduce asymmetries found in nonmanufacturing Layout empty travel Several tributed sume challenges remain. In designing of the current models layouts, designers of department that the number 0-^1-^2-^3-*2-^3->4-^5->6^7-*8-^9-*8->9->10->11. tion, as measured by average WIP, Conges in layout /, than in layout is far worse /2, even though layout/, minimizes full travel (Benjaafar2002). In layout /2, departments 2, 3, 8, and 9, which are more frequently visited than other departments,are placed inadjoining locations.Despite the fact that there are no direct flows between the departmentpairs (2, 3) and (8,9), the overall effect is a reduction in empty travel time, which is sufficient to reduce of the material-handling the utilization and leads to an overall reduction inWIP. Emptytravel time is reduced since there are frequent empty trips between (2, 3) and (8, 9) as both pairs of departments are popular (z/emp/yand ufull refer to the empty destinations. and full utilization of thematerial handling system.) are known. of each duplicate In practice, before de facility designers must make these decisions a layout. Current models not account for do veloping the capacity the cost of disaggregating and distributing depart nor do of scale as they capture the economies sociated with consolidated operating departments. ments dis as a consolidated typical of single a com in department job shop (for example, operators, areas, puter control systems, loading and unloading and and waste-disposal The Challenges research Figure 9: A single product goes through the following sequence of de partments are also For example, applications. both the spine and star layouts are common configu rations for airports. Spine and T-shaped layouts are ter also popular designs for freight and cross-docking minals (Gue 1999). Research = duplicates infrastructure facilities) must be duplicated in a Interfaces 72 Vol. 32, No. 6, November-December 2002 BENJAAFAR, O O O O ^ D AND HERAGU, Factory O IRANI Layouts same order were not one would synchronized. need to capture To address this problem, setup minimiza con tion in the objective function or place additional to prevent order splitting. straints on flow allocation For modular issues need layouts, several important to be substrings, substrings duplication (1) After one would need similarity and a threshold value lar substrings. This is related tX X Loop all common identifying to aggregate several of the into a single module to minimize machine costs based on a measure of substring dis addressed: simi for aggregating to the problem of in the fi the optimal number of modules determining nal layout. One idea is to develop measures of connec of the directed graph we obtain tivity and transitivity a set of common from aggregating (2)We substrings. need to establish criteria for feasibility allocating ma layout to several chines avail subject to machine for minimum machine utilization. modules ability and criteria An iterative loop should be incorporated in the design to absorb any module because criteria. of these rejected treats each residual substring (3) The current approach as a sequence on machines of operations performed It seems logical to clus located in process departments. ter these substrings and aggregate their machines on cell modules based user-defined thresholds (4) We Star layout has a smaller variance configuration itself has a smaller variance than the linear 10: The star-layout Figure loop layout, which than the layout. distributed all department layout duplicates. and distribu Thus, while department disaggregation tion may yield material-handling benefits, a firm must trade off these benefits against the advantages of op erating model consolidated facilities. We that combines an integrated and ca duplication need department with and flow allo pacity assignment layout design we as In our initial flow-allocation cation. model, in sumed full flexibility workload among assigning same of the In this duplicates department. practice, could mean different routing and dispatching policies could system. These models splitting 32, No. Furthermore, performance. to evaluate and compare model Such configurations where dedicated 2002 73 policies on layout could use the queueing the performance of clas that reduce distance variance identifying configurations can be valuable. without average distance affecting orders 6, November-December the sical layout configurations under varying conditions. new are more ef We might that identify configurations in WIP fective small levels. In particular, achieving smaller Interfaces Vol. of then be of different we departments the hub-and-spoke of several equidistant for a single product among and longer and batches, duplicates, more frequent setups. Order splitting could also delay because orders of the batches shipping completed several for must the perfor compare string clustering. mance of this new layout with those of flowline, cel same and functional for the lular, layouts facility. For agile layouts, we need models that account for material-handling used to study the effects across into include the star layout, might are from each other, or equidistant in which each hub consists layout, and is served by a departments In many differen applications, transporter. or differ WIP at different departments between tiating ent stages of the production is WIP tends useful. process BENJAAFAR, HERAGU, AND IRANI Factory Layouts uation to appreciate in value as it progresses through the pro duction process. We should favor layouts that reduce the most which expensive departments WIP of the material-handling decide simultaneously first, layout design with the design system. For example, we could between capacity capital the trade-offs tems. lighting in prod postponement and (3) the shift tomore flexible and The first trend could change the na ture of layout design from strategic to operational (re more more could become and focused layout frequent on supporting operational performance), requiring and constrained Batta, with industries ample, with innovative or custom-made For these firms, designing products). layouts that are robust and able to sustain a wide range of products remain critical. would dynamic 57(2) 280-286. R. 1987. The in part upon work supported by the National 9908437. Any Science Foundation under Grant no. DMII opinions, or recommendations in this ma and conclusions findings, expressed and do not necessarily reflect the views terial are those of the authors This material is based of the National Science Foundation. Design, Science -. strategies duction Res. Askin, R. G. 28(2) 1999. An Internat. -, M. M. Salomon. for flexible layouts. N. H. Lundgren, manufacturing 311-323. empirical J. Production F. Ciarallo. evaluation Res. 37(5) 1990. Dynamic Internat. systems. of holonic and layout J. Pro fractal 961-978. 1997. A material flow based eval Sei. layout. Management A algorithms: 1992. state Solutions of the for the Eur. J. Oper. problem. Res. Sei. 33(8) layout. Management in cellular manufacturing sys sharing H. R. Parasei, D. H. Liles, eds. Planning, of Cellular Manufacturing Systems. Elsevier and Analysis B. V., Amsterdam, The Netherlands. L. McGinnis, factory layouts. R. Graves, eds. Progress inMaterial Research. Material Handling NC. Institute, Charlotte, -. 2002. Design of plant Sei. 48(5) 679-704. with layouts B. Peters, Handling effects. Manage queueing ment M. -, Sheikhzadeh. Trans. 2000. of flexible Design plant layouts. HE 309-322. 32(4) L. Zavanella. Braglia, M., S. Zanoni, environments: and Strategies Res. Forthcoming. Production 2002. Layout quantitative in dynamic Internat. ]. design indices. S. F., D. B. Webster. 1987. Evaluating the flexibility of Bullington, facilities costs. Proc. In estimated IXth layouts using relayout ternat. Conf. Production Res. Birmingham, U.K., 2230-2236. D. G., M. A. Venkataramanan. Conway, the dynamic layout problem. facility 955-960. Drolet, virtual J. R. 1989. Scheduling School of dissertation, 1994. Genetic Comput. search Oper. cellular manufacturing Industrial IN. West University, Lafayette, P. 1998. the up Souping supply Engardio, Engineering, chain. Bus. Week Res. and 21(8) systems. Purdue (August) 24-31,110-112. Feare, T. 1997. Less automation means more Modern Materials Microsystems. Handling customization E., H. Lee. 1997. Mass Feitzinger, productivity (November at Hewlett The P., R. A. Millen, 2002 2, June 2000. Flexible References Afentakis, layout of plant dynamics Ph.D. Acknowledgments of plant facility S. 1995. Machine Benjaafar, tems. A. K. Kamrani, follow differentiation, ample, products delayed a flow-line-like the above mostly path). However, not to trends would most all industries. likely apply For many forms, neither full process reconfigurability nor product will be possible standardization (for ex cut workstations Retrieved 1065. the increased tools and new design metrics. In layout-design contrast, the second and third trends could lead to sim (for ex pler layouts and a reduced need for re-layout J. 1993. The dynamics C. H. Cheng. 1998. Dynamic layout art survey. Omega 26(4) 507-521. F. R. Jacobs, M. A. Venkataramanan. -, uct differentiation, scalable machines. new issue. 654-655. 39(5) three main trends industry, high move more the toward and (1) again: lighter (2) the increased modularization equipment, portable of products 1995. Flexible on flexible conveyor sys telephones rely Retrieved June 2, 2002 (www.assembly issue. May Balakrishnan, are worth From Braun 71-90. MI, mag.com). -, and WIP. Research. Handling J. R. Wil (www.assemblymag.com). custom 1996. Norstart -. on and in Material Progress Ann Arbor, (online edition). Assembly Magazine in process. work September of transporters (number ity) and department cost both WIP-holding minimizing costs. We could then examine investment eds. Brumfield, capacity material-handling or transporter carrying capac with the objective of placement, R. alternatives for agile manufacturing. layout R. E. Ward, M. L. F. McGinnis, D. J.Medeiros, helm, for example, those in that carry out the last production located. Another important avenue steps are centrally of research is to integrate of Graves, Flynn, of postponement. Harvard Bus. Rev. 75(1) power B. B., F. R. Jacobs. 1986. A simulation comparison technology Production Fu, M. C, with Res. traditional 24(5) job shop manufacturing. 1171-1192. at Sun 1) 22-25. Packard: 116-121. of group Internat. J. 1997. Minimizing and ma work-in-process in the facilities HE Trans. 29(1) layout problem. B. K. Kaku. terial handling 29-36. Interfaces 74 Vol. 32, No. 6, November-December 2002 BENJAAFAR, HERAGU, AND IRANI Factory P. 2000. Gibson, asset The Bus. Magazine Electronic paradox. Layouts 26(4) Lacksonen, 120-126 K. Gue, (www.eb-mag.com). 1999. The effect of trailer on the scheduling layout Sei. 33(4) 419-428. Transportation 2002. Make-to-order, D., S. Benjaafar. make-to-stock, of freight common A differentiation: product and analysis. Working MN. neapolis, paper, R. M. 1986. Flexibility Gupta, Material Flow 3(4) 243-250. in for modeling Min of Minnesota, A layouts: simulation Volume. New ASME, for designing Zijm. 2000. A framework able facilities. Technical DSES report, Department, Institute, Troy, NY. Polytechnic J. C. W. -,-, network to approach Technical Rensselaer report, DSES Department, Troy, NY. P. E., T. E. Cowan. 1976. CRAFT-M for layout Hicks, Indust. Engrg. 8(5) 30-35. A. -, queuing turing (www.ims.org). Irani, S. A., H. Huang. 2000. Custom facilities using multi-product botics Automation 16 259-267. T. M. Cavalier, P. H. Cohen. sharing Kaku, B. K., namic value 2000. The design Koren, Institute, Y., Brusel. CIRP Kouvelis, 1999. Reconfigurable 48 527-539. P., A. models 52(3) -, T. Moriwaki, S. Kiran. for automated 1991. G. G. Ulsoy, Pristchow, systems. manufacturing H. V. Ann. Single manufacturing A. 1991. Holographic Report No. 91-76, E. Smith. in block tainty Industrial and multiple systems. period layout Eur. J. Oper. Res. layout 2001. environ layout of manufacturing uncer production Considering of paper, Department Working of University Pittsburgh, Pittsburgh, design. Engineering, S., R. Batta, U. Palekar, in plant certainties R. M. Bosch, layout un 1992. Modeling Eur. J. Oper. Res. 63(2) 347 S. Elhence. problems. 359. J. 1986. The M. Rosenblatt, Sei. 32(1) dynamics of plant layout. Management 76-86. D. H. Kropp. 1992. The single period stochastic plant layout HE Trans. 24(2) 169-176. problem. H. L. Lee. 1987. A robustness to facilities approach design. Internat. ]. Production Res. 25(4) 479^86. -, -, 1993. Comparison of equivalent pure cellular Sarper, H., T. J.Greene. and functional environments In simulation. production using ternat. J. Comput. Integrated 6(4) 221-236. Manufacturing Interfaces 2002 75 in 1990. Flexibility A manufacturing: Flexible J. Systems 2(4) 289-328. Manufacturing versus 1993. Cellular functional J.M. Chames. Internat. Shafer, S. M., a under G. J. Gutierrez. 1992. Algorithms for ro and for single period layout planning period multiple Eur. ]. Oper. Res. 63(2) 287-303. systems. manufacturing 1987. The facility Eur. ]. Kusiak, A., S. S. Heragu. layout problem. Res. 229-251. 29(3) Oper. lay PA. of shop operating Tompkins. 200-205. 1980. variety conditions. Decision survey. layout Sei. 24(3) 665-681. A. A. Kurawarwala, 6, November-December B. A., Norman, 300-314. 32, No. robust Sethi, A. K., S. P. Sethi. bust Vol. Systems for job shop organization Res. 37(3) 501-521. layout ]. Production P. Lefran?ois. added F. Jovane, Internat. and of Management, systems. Faculty Laval University, Canada. Montreal, Qu?bec, National Research Council. 1998. Visionary Manufacturing Challenges DC. Press, Washington, for 2020. National Academy cells: manufacturing flows for the machine paper, Virginia operations. Working Poly VA. Blacksburg, 1999. Facility in a changing Kochhar, J. S., S. S. Heragu. layout design environment. Internat. J. Production Res. 37(11) 2429-2446. technic /. Manufacturing perspectives. B. 1999. Fractal Technical center Recent problem: 694. arrangement. of a distribution layout functions and layout objective Facility Res. 34(10) 2727-2742. J. Production Internat. -,-, layout design Internat. ]. Production Res. 31(4) 791-810. problem. 1997. A tabu-search heuristic for the dy J. B. Mazzola. INFORMS J. Comput. 9(4) 374-384. plant layout problem. J. F., R. D. Meiler. with intercell facility a scenario A. LaForge. 1992. Dynamic tree layout design given of probable futures. Eur. J. Oper. Res. 63(2) 271-286. 1991. Strategic U. Venkatadri. of dynamic interpolative design Sei. 37(6) 682 systems layout. Management manufacturing of facility for layouts design IEEE modules. Trans. Ro layout 1993. Virtual and Exploiting Klote, -, layouts. In Polytechnic 2000. Highly and reconfigurable manufac productive Technical Manufac systems. report, project Intelligent Initiative. Retrieved 2001 Systems September turing -, outs. ments. stitute, Ikegaya, 1996b. -,-. reconfigur Rensselaer G. Meng. 2000. An open cellular and jobshop evaluating and emerging 15(5) 351-366. 9 York, van Ommeren, 1996a. The trends Montreuil, H. M. W. -, M., (www.eb-mag.com). R., K. Y. Gau. Meiler, issues in adaptive manu handling The Materials Division Engineering Handling systems. facturing 75th Anniversary Commemorative 13. assignment algo Internat. J. Production McHale, 1994. Material J. S. Kochhar. problem. differentiation. Sei. 43(1) 40-53. layed product Management T. 1999. Special top 100 contract manufactur report?The ers. Electronic Bus. Magazine Retrieved June 2, 2002 (August). approach. S. S. 1994. Group and cellular manufacturing. Heragu, technology IEEE Trans. Systems, Man, Cybernetics 24(2) 203-215. -. 1997. Facilities Design. PWS Publishing, Boston, MA. -, layout outs. delay framework University 1993. Quadratic 2002. Design S. Benjaafar. of dynamic distributed lay of Mechanical paper, Department Working Engineering, of Minnesota, MN. University Minneapolis, 1997. Modeling the costs and benefits of de Lee, H. L., C. S. Tang. Lahmar, or for the dynamic 31(3) 503-517. Res. terminals. Gupta, E. E. Enscore. T.A., rithms Shore, R. H., Trans. Smith, G., Ed. J. A. 12(2) J.Wheatley, (October J. Green. 23) 72-82. Flexible facilities 2000. Car power. design. ARE Bus. Week-Inter,nat. BENJAAFAR, HERAGU, AND IRANI Factory Layouts 1994. Coping with the loss of pooling J.Meredith. syn Sei. 40(4) ergy in cellular manufacturing systems. Management 466-483. Suresh, Tompkins, shock J.A. 1980. Modularity in facilities design. Y. A. Bozer, E. H. Frazelle, J. A. White, 2nd Trevino. 1996. Facilities Planning, York. -, Urban, T. L. 1992. lower -. -. with and flexibility: Dealing Indust. Engrg. 22(9) 78-81. Computational bound procedures lem. Eur. J. Oper. Res. 57(2) 271-279. 1993. A heuristic for the dynamic 25(4) 57-63. 1998. Solution lem. Ann. for the fractal and facility future shop layouts. for the dynamic procedures Oper. Res. 76 323-342. problem. of D. -, prob prob 2000. Empirical findings Res. 38(3) J. Production Internat. J. 2000. super factory?or Super of job flexibility 21-29. in the U.S. Res. 27(9) on manufacturing 481-507. headache. cell Bus. Week (July) 31, 66. HE Trans. layout layout organization. B. Tyberghein. 1980. Measuring Internat. J. Production Res. 18(1) J. Johnson. design. Yang, facility 1997. A design methodology HE Trans. 29(10) 911-924. 1989. Cellular manufacturing U., L. N. Hyer. users. A of Internat. J. Production survey industry: 1511-1530. Wheatley, layout B. Montreuil. Wemmerl?v, efficiency layout D. B., M. Webster, J.M. A. Tanchoco, J. ed. John Wiley, New performance for the dynamic U., R. Rardin, Venkatadri, N., T., B. A. namic Res. and 108(1) Peters. 1998. Flexible uncertain machine production layout environments. design Eur. for dy J. Oper. 49-64. Interfaces 76 Vol. 32, No. 6, November-December 2002