Application of Lean Methodologies in the Maintenance of

Aircraft Engines

A Case Study at OGMA

Tomas Fonseca Ruivos Fernandestomas.fernandes@tecnico.ulisboa.pt

Instituto Superior Tecnico, Universidade de Lisboa, Portugal

November 2018

Abstract

In the context of an increasingly competitive global market with sudden and unexpected transforma-tions, some enterprises see their volume of business and market share decrease as new players emerge.Resulting in an increased scarcity of finantial resources, the companies are compelled to increase theiroperational efficiency, in order to mitigate the costs and maitain and increase their profit margins. It isin this segment that the Lean methodology appears with the objective of eliminating wastes, increas-ing standardization, increasing the company’s services flexibility according to the client demand andimplement a culture of continuous improvement.

The present paper intends to employ Lean methodologies and Lean tools to diagnose and proposesolutions regarding the improvement of operational efficiency of the portuguese aeronautic enterpriseOGMA in the extent of Maintenance, Repair and Overhaul of aircraft engines.

Regarding the company, the volume of business of OGMA regarding the engines maintenance isjeopardized by the shorter Turn Around Time delivered by its direct competitors. For this reason, it isintended to reduce the current total time of maintenance, hence achieving the highest possible clientsatisfaction through quality and on time delivery compliance and thus increasing competitiveness inthe global market.

Keywords: Lean Methodology, Maintenance Repair Overhaul, Operational Efficiency, AircraftEngines

1. IntroductionThe aeronautic Maintenance, Repair and Overhaul(MRO) industry is often characterized by an envi-ronment of low product cadency and high diversityof required maintenance processes. This may sug-gest a certain incompatibility with the Lean ideol-ogy which defends processual standardization andachieved opperational efficiency backed by a ex-tremely high product cadency. However, as in-spected by Lane [1], Lean ideology can be exploitedto be correctly implemented in these environmentsand excel at improving the operational efficiency ofa high diversity and low volume plant. Any com-pany inserted in this context has to be able to ac-comodate high client fluctuations, and be flexibleenough to achieve high efficiency both in momentsof high and low work load. In this segment, theplants have to be planned to accomodate over ca-pacity, with a high multidisciplinarity of its workers.

OGMA is set to endure full overhaul of aircrafts

being divided in three different segments, includ-ing maintenance of aerodynamic structures consti-tuted mainly by the phuselage and wings, fabrica-tion of aeronautic structures components and en-gines maintenance. The present paper is insertedin OGMA’s engine MRO segment and is fueled bythe necessity of the enterprise to increase its volumeof engines capacity preconditioned by the marketforecast demand. With a recent reduction of busi-ness volume in the past years, the current enterprisesituation results in a scarcity of finantial resources.For this reason, OGMA’s vision is to increase thevolume of engines overhauled annually to increaseits revenues, however the increase in the capacityhas to be endured without major investments dueto the lack of the enterprise liquidity.

In the context of achieving high gains with lowinvestment, it is employed Lean methodologies andtools to reduce wastes which do not aggregate valueto the MRO processes and increase the opperational

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efficiency of the plant. The increased efficiency isachieved with the reduction of the time each main-tenance process takes in the plant by tackling thewaiting times and distances traveled by both thetechnicians and the engine parts inside the shopto achieve a reduction on the Turn Around Time(TAT). To analyse and diagnose the processes withinherent potential improvement, it is employed theLean tools of Visual Management, Value StreamMapping (VSM), Yamazumi chart, Ishikawa dia-gram and Spaghetti diagram.

The aims of the present work arise from theframework described previously and are set to de-velop and define standard procedures and solutions,which ensure that the company is able to accomo-date the increase in volume of engines due to themarket precondition. The following items describethe aims:

� Diagnose the current line of maintenance in or-der to analyze the activities with potential im-provement;

� Propose a viable approach to the improvementof the MRO line in terms of opperational effi-ciency, utilizing Lean methodologies;

� Reduce the TAT of the engine maitenance inorder to accomodate an increased volume ofengines.

With these aims accomplished, it is expected thatthe company reaches a state where both the in-creased client demand and its fluctuations aresmoothly accommodated with a parallel increase inefficiency both in high and low work load periods.

2. Literature ReviewLean manufacturing is an approach of ongoing im-provement within the management of an organiza-tion which contributes with tools for the efficientyexecution of a project. Its primary objective is toadd client value by reducing the waste in terms oftime, human effort and expenses.

It derives from the Toyota Production System(TPS), which is an organizational and technical sys-tem developped by the car manufacturer companyToyota with the main objectives to reduce threetypes of wastes: Muda, being the activities thatdo not add value to the client; Mura, which is theunevenness in the activities of a project or the lackof standardization; Muri, addressing the overbur-dening of the machinery and operators [2].

2.1. Lean ConceptsLean manufacturing can be defined by the con-cept of Kaizen, which translates from the japaneseinto change for the better. As the expression in-dicates, it refers to an ongoing process of trans-formation to achieve ultimate efficiency and min-imal waste. Moreover, Lean manufacturing canbe achieved through the implementation of several

groundwork concepts such as process standardiza-tion, and Heijunka which can be translated into lev-eling and consists in a production system controlledby the client demand [3].

Regarding the pillars of a typical lean organiza-tion it appears the concept of Kanban, which canbe translated from the japanese into visible card.This term refers to an operational system where amaterial is produced or moves along a line of pro-duction only when it is required ususally by meansof a visible card containing the material informa-tion. Together with the Heijunka mindset, Kanbanenables a production system where the produts aremade just in time (JIT), avoiding excessive inven-tory [4].

The Lean methodology can be characterized byfive principles according to [5]:

1. Value: Identifying what the stakeholders per-ceive as the value of the project.

2. Value Chain: All the necessary activities in aline of production/maintenance

3. Create flow: Ensuring the product moves in theline of production/maintenance through everyvalue action with the correct cadency, avoidingbottlenecks.

4. Establish Pull: Reffering to a production sys-tem where the finished goods are ready to bedelivered when the costumer requires them.

5. Seek perfection: A mindset of no bounderies re-garding the processes of ongoing improvement.

2.2. Lean ToolsSome of the Lean tools employed in the presentwork are the following:� Visual Management: The arrangement of in-

formation in an explicit and easy to consultmanner, hence enabling the effective identifi-cation of anomalies.

� Visual Stream Mapping: A process mapping ofthe value added activities containing the flowof material and information between stations.Contains both the value-added times and thenon-value-added times enabling the sistematicidentification of wastes and determination ofwhat can be improved [6]. Together with thedisplayed total times of added and non-added-value activities, it is computed the Takt Time,which is the time period at which two consec-utive products should leave the line of mainte-nance, according to the client demand.

Takt Time =Production time/Day

Products ordered/Day(1)

� Swim Lane diagram: An extension of VSMused to easily acknowledge the counter-flowsand process repetition in a line of production.

� Yamazumi Chart: Provides information in astacked manner regarding the temporal con-

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tribution of value-added actions, necessarynon-value-added actions and unnecessary non-value-added actions.

� Spaghetti Diagram: A diagram which maps themotion flow of materials and/or operators andinterlinkage between process activities.

3. Case Study FrameworkOGMA is a Rolls Royce authorized maintenancecenter and currently comprises the maintenance ofthe military T56 and AE family of 2100 and 3007engines. With the necessity to expand its busi-ness, the company has won a contract resulting inthe accomodation of a new AE family model, theAE1107, which will increase the volume of enginesmaintained annually, hence the line of maintenancehas to be restructured.

The general procedure that constitutes the engineMRO of the company is visible in figure 1.

The workforce responsible for the engine recep-tion captures the engine general physical condition.As the engine enters the line of maintenance, it isdisassembled and each part is cleaned in order tobe submitted to several performance testings whichwill conclude if a specific part is serviceable or needsrepair. The preliminar set of tests is the Non-Destructive Testing (NDT), which is characterizedby a series of inspectinons which do not affect thecurrent state of the parts. The metrology is a di-mensional evaluation, crucial for the great major-ity of the engines components, however speciallyimportant for the non-static parts like the com-pressor and the turbine. As the parts reach theevaluation stage, they are inspected by a special-ized workforce which segment the parts in eitherserviceable or not serviceble, in which case it ei-ther can be repaired or has to be replaced. In theFOC phase (Fim de Orcamento de Custo which isportuguese for Cost Estime, CE) it is established aline of communication with the client in which it ispresented the detailed information of the requiredMRO operation with its inherent price, accordingto engine condition agreed by the evaluators. Therepair stage is characterized by several stations oflathe, milling machines and rectifiers and is consti-tuted by a high diversity of inherent procedures foreach of the around 1000 different parts in an engine

and their repair requisites.As all the parts become serviceable, the engine

can be assembled in two stages: first each moduleis assembled (with the comprised modules being thePower Gear Box of a turbprop, Torquemeter, Ex-haust components, Accessory box, Turbine, Com-bustion Chamber, Compressor and Diffuser) andsecond the modules are coupled in the final assem-blage. Followed by a functional testing the enginecan be expidited to the client after the confirmedpayment. In a holistic approach, the entire MROcan be divided in two main stages: the preliminaryphase, from the reception untill the evaluation andthe repair phase, from after the evaluation untill theexpedition.

Since examining over 1000 parts and their routesin the plant would result in an over extensive andunnecessary work, first it is acknowledge the un-niverse of parts of the AE2100 (since it constitutesthe main volume of business) which need to be re-viewed in order to correctly plan the entire MROline with the increased volume. In this segment, itis chosen 4 sample parts according to the followingcriteria: (i) the amount of resources employed interms of time, labour and machinery in that part;(ii) the worst case scenario repair route; (iii) con-siderable frequency at which those parts need repairand endure that repair route. The agreement be-tween the 3 criteria factors results in the followingcomponents: Main Drive Gear (MDG) which is agear inside the module of Power Gear Box; RearTurbine Bearing Support (RTBS), being the sup-port for the rear end of the engine shaft; the Com-pressor Rotor, which is the main component of therotating part of the compressor; Compressor Air In-let Housing (CAIH), the air inlet carter supportingthe front end of the engine shaft.

As a final note, these four parts have typical pathsinside the repair phase and can be used as sampleswhich characterize the entire operation of all thecomponents. These 4 routes are characterized withstations interlinkage transversal to all parts, hencethe entire line is examined. For that reason it isexpected that the operational efficiency is enhancedacross the entire processes of all the parts.

Figure 1: Generic MRO procedure in OGMA

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4. Diagnostic and Analysis of ResultsThe planning of the line of maintenance accordingto the workload expected starts with the inspec-tion of the engine forecast for the following 10 years(2019-2028). With the acquisition of the AE1107model, the forecast results in a gradual annual in-crease on the volume of engines from 106 (2018) to amaximum of 174 (achieved in 2026), corrrespondingto an increase of 64%.

With this data it is possible to compute the TaktTime which will serve as a refference to the maxi-mum time each part should stay in a maintenancestation. Using expression 1, the Takt Time showsthat every 49.7 hours an engine should be expeditedaccording to the client demand.

4.1. Current VSMWith the Takt Time as a refference, it is plannedthe VSM of the entire current MRO process of fig-ure 2 with CT being the cycle time, LT the Leadtime and WF the Workforce. The Kitting activ-ity regards a space where the serviceable parts areredirected and accumulated before the assembly be-gins. For that reason it has the same cycle timeas the repair. The bottom timeline provides thetemporal aspect of the entire MRO. The values ontop concern the Work In Progress (WIP) or iddlingtimes before each station, the bottom values regardthe CT of the activities. Concerning the 240 hoursWIP before reception and the 336 hours of FOC,these times are mostly ruled by the client, henceare external factor which can not be improved. Forthis reason the FOC is not tackled with the presentwork. After the preliminary phase, the engine as awhole can no longer be considered, since the partsdiverge in the most varied directions in the shop

during repair. For this reason, this activity is an-alyzed deeper in detail in section 4.3 with anotherVSM diagram in the form of a swim lane. Duringthe repair step, there are several processes of clean-ing, NDT and metrology which are not inherent tothe preliminary phase. The hours of these processesare not included as CT for the inherent centers ofthis VSM, being accounted inside the CT of the re-pair stage. Nonetheless, their CT also constitutesto the WIP of each of the stations of cleaning, NDTand metrology during the preliminary stage.

4.2. Inspected IssuesWith the process flow established, it is endured anextensive analysis of each station to acknowledgewhat can be improved, resulting in the followingaspects:� Reception: The internal waiting time is aver-

age 12 hours.� Disassembly: The current line is not suf-

ficient to accomodate the increased volume;There is no specific workforce focused on thisstation.

� Cleaning: Lack of station capacity to processthe parts during the preliminary circuit due tothe flooding of the parts during repair, whilethere is a cleaning cabine obsolete.

� NDT: The parts during repair flood the sta-tion, while there is an NDT cabine obsolete.

� Metrology: The parts during repair flood thestation, while there is a measuring robotic armunused.

� Evaluation: Each evaluator operates in oneengine, resulting in high CT ttimes.

� Modular Assembly: Missing hardware dur-ing assembly and lack of station capacity with

5 32 23 22 31 85 336 557 48 14 14 81st Shift:2 1st Shift:3 1st Shift:2 1st Shift:2 1st Shift:2 1st Shift:1 1st Shift:1 1st Shift:- 1st Shift:3 1st Shift:3 1st Shift:4 1st Shift:22nd Shift:2 2nd Shift:2 2nd Shift:2 2nd Shift:2 2nd Shift:1 2nd Shift:1 2nd Shift:0 2nd Shift:- 2nd Shift:3 2nd Shift:3 2nd Shift:3 2nd Shift:0

1 2 2 2 2 2 1 2 2 2 2 2

5571st Shift:-2nd Shift:-

-

LT 1798 Hrs75 D

CT 1175 Hrs49 D

LT 2264 Hrs94 D

CT 1641 Hrs68 D

60 95 47 0 0

8120 14 14336 91422 31 115

12 34 2812T5612 32 23

240 51 44

CLIENT CLIENTPLANNING

RECEPTION DISASSEMBLY CLEANING NDT METROLOGY EVALUATION FOCCT: (h) CT: (h) CT: (h) CT: (h) CT: (h)

REPAIR MOD. ASSEMB FINAL ASSEMB BENCH TEST EXPEDITIONCT: (h)

WF WF WF WF WF WF WF WF WF

CT: (h) CT: (h) CT: (h) CT: (h) CT: (h) CT: (h)

Shifts:

KITTING

WF WF WF

AE 2100 series

Shifts: Shifts: Shifts: Shifts:Shifts: Shifts: Shifts: Shifts: Shifts: Shifts: Shifts:

PROVISIONING PARTS SUPPLIER

C/T: (h)

WF

Shifts:

23

120 12

5 32 22 31 85 336 557 48 14 14 8

34 28240 51 44 60 95 47 0

2.21/week

FORECAST106 Annually8.83 Monthly

FORECAST181 Annually

15.08 Monthly

Daily

Weekly

Weekly

DailyDailyDaily

Daily

Daily

Daily

DailyDaily

Daily

Daily

Daily

COMMERCIAL WeeklyDaily

Weekly

3.77/week

WIP WIP WIP WIP WIP WIP WIP WIP WIP WIP WIP WIP

Figure 2: VSM before changes

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Figure 3: Yamazumi diagram with LT per station

the increase in volume.� Final assembly: Within the Takt Time limit.� Bench Testing: Within the Takt Time limit.� Expedition: Within the Takt Time limit.Figure 3 displays the LT for each activitiy with

the Takt Time line and the resume of the inspectedissues. It is segmented each activity in work hours(WH) in green and in idling times in red. The ob-jective is to reduce the quantities in red, which iswhere the majority of wastes are located. The ma-jor bottleneck is located in the preliminary phase,particularly in the station of metrology. Nonethe-less, the expected lead time of the evaluation is suf-ficient to become a bottleneck. Still in this segment,the aim of the present work is to accomodate the in-crease volume of engines, hence tackling the bottle-neck and the potential one is not sufficient. For thisreason, the entire set of activities which fall abovethe Takt Time line have to be time mitigated. Ob-serving the green bars, they all fall below the Taktline, besides the evaluation. For this reason, theevaluation system has to be rethinked, since elimi-nating wastes is not sufficient by itself.

4.3. Current Process Flow During RepairFor the propose of the present paper, it is displayedthe analysis of the most critical part, the MDG,since the issues inspected in this part are tranversalto not only the other 3 critical parts, but also for theentire set of over 1000 components. The swim lanediagram is displayed in figure 4. As a side note, thestations which are introduced in the swim lane dia-gram are: TE for Electrolytic Treatment, Balancingfor the adjustment of rotating parts, Locksmithing,Welding, TT as for Thermal Treatments, Plasmasurface coatings and Painting.

The main contrains regarding the repair concernthe processes order which can not be swapped dueto mandatory precedent activities and the fact thatthe WH are already carefully adjusted according tothe inherent work, hence can not be reduced. Forthis reason the margin for reduction the repair LTlies in the mitigation of the WIP times.

The WIP before cleaning, NDT and metrologyassumes high values since the stations are also req-uisited during the preliminary phase. Furthermore,the 4 major counterflows aref found when the partshead to the cleaning or NDT station (in 0�1, 2�5,

Figure 4: Current Swim Lane diagram for the MDG

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Figure 5: Current Spaghetti diagram of the plant

8�10 and 14�18). This type of counter-flow isparticularly alarming since these stations are asso-ciated with considerable WIP and long distancestraveled by the parts. This is due to the fact thatthese centers are far from the repair area since theyare not located in the shop floor. Moreover, and notonly in the case of the MDG, whenever a part movesto the metrology, it endures a considerable counter-flow (e.g. 20�21 and 22�23), also associated withconsiderable distances and idling.

4.4. Current Spaghetti DiagramAlongside the diagnostic regarding the reduction ofthe waiting waste, it is also endured a Spaghettianalysis to acknowledge how the waste of avoid-able motion can be mitigated, through layout al-terations. In figure 5 it is observable that the high-est density of flow lines regarding the four engineparts is located in two areas: (i) around the metrol-ogy and (ii) connecting the locksmithing/weldingto the cleaning/NDT stations. Particularly for themetrology, the high density flux to the left of thestation regards mostly the paths during the repairphase, while to the right concerns the feeding ofthe preliminary phase. Furthermore, the high fluxconnected to the cleaning and NDT station is co-herent with the counter-flows analyzed in the pre-vious section 4.3, and is also inspected for the other3 parts as seen in figure 5. The repair machin-ery (lathes, milling machines and rectifiers) andthe locksmithing/welding are alienated by closedwalls and constrained accesses, inducing complex

and lengthened paths, hence empowering lack ofcontinuous process flow and high waiting times.

The rearrangement of the evaluation center canbe analyzed with the zoomed in spaghetti diagramof figure 6. There are two types of wastes inspected

Figure 6: Current Evaluation Spaghetti diagram

in the evaluation: (i) waiting, due to the lack of or-ganization of the reception area, resulting in theoperator spending a considerable amount of timeto find parts of its inherent engine; (ii) avoidablemotion, since the measuring devices needed to per-form the evaluation are shared with the disassemblyline, hence are not at reach. It should be taken intoconsideration that the diagram does not display allthe movements during the evaluation stage, becauseshowing all the trajectories would result in a highlyentropic diagram. For this reason it is only drawn

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a step of evaluating one part by each of the fourevaluators.

5. Proposed SolutionsWith the diagnostic endured, the proposed solu-tions are the following:

1. Creation of separate centers of NDT, Cleaningand Metrology to feed the repair stage. Theseprocesses during repair are simpler comparedwith the preliminary phase, hence can be en-dured utilizing the obsolete machinery;

2. Reorganization of the repair area;3. Inclusion of multiple lines of assembly and dis-

assembly;4. Reorganization of the evaluation area.

5.1. Future VSMWith the improvements proposed, the VSM is un-changed in terms of process interlinkage. The im-provements are noticeable in the reduction of theidling times, and for that reason the TAT is re-duced from 75 to 51 days. Figure 7 displays theimpact of the proposed solutions in the reductionof the WIP. The reduction in the disassembly andassembly lines is accounted for the additional lines.Regarding the highly requisited centers of cleaning,NDT and metrology, their WIP is reduced since therepair parts are now redirected to the second cen-ters. To quantify these WIP mitigations, it is in-spected that the number of engines simultaneouslyin the repair phase of the future plant setup is 5.It is then inspected the average time the total setof parts during repair of an engine is spent on thecleaning, NDT and metrology as WH. This tempo-ral parameter multiplied by the number of enginesin the repair can be discounted in the preliminaryphase WIP.

Regarding the evaluation, it is proposed to im-plement a system where all evaluators work on thesame engine, in order to distribute the CT throughall the evaluators. Furthermore, the layout reorga-nization explained further in the present paper alsocontributes with a reduction on the WIP.

As a final note, it is now visible that the new bot-tleneck is located in the NDT area, with the totalLT lieing above the Takt line. Nevertheless, it isendured a process analysis parallel to the presentproject which intends to tackle situations of docu-mental setbacks, hence it is expected that at a finalstage the stations LT all lie below the Takt line.

5.2. Future Process Flow During RepairFigure 8 shows the impact of the second centersin the repair phase. Furthermore, in the follow-ing section 5.3 it is visible that the new centers ofcleaning, NDT and metrology are located near therepair area, and for that reason the counter-flowsare eliminated, resulitng in drastically reduced WIPand distances traveled by the parts.

As the centers are closer to the repair machinery,the counter-flows in the diagram shift down, mean-ing that the process is increasingly smoother withcontinuous process interlinkage. The reduction ofthe total LT segmented by WH and WIP is repre-sented in figure 9.

5.3. Future Spaghetti DiagramFigure 10 displays the future spaghetti diagram,representing the layout with the proposed solutionsand the flow of the 4 critical parts in the shop.

The additional lines of disassembly and assemblyare represented. By bringing the modular assem-bly closer to the kitting, the wastes of unnecessarymotion endured by the technicians are mitigated inthe event of missing hardware during assembly.

The high flow density around the centers of clean-ing and NDT is now reduced, since these centers areset to feed the preliminary phase alone.

Since it is not possible to change the sequence ofthe activities, the reduction in the distance traveledis endured by clustering the high flow density insidethe smallest possible area. In this segment, therepair zone is constituted by an open-area centerwhere the entire repair machinery is aggregatedtogether with the locksmithing and welding withthe second centers of cleaning, NDT and metrology

Figure 7: Yamazumi diagram regarding the impact of the solutions

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Figure 8: Future Swim Lane diagram for the MDG

Figure 9: LT, WH and WIP reduction for the MDG

Figure 10: Spaghetti Diagram of the future state

in the middle to feed each station. For thisreason, the new layout results in a spaghettidiagram where the only place with high densityflow lines is in the repair area where the entirecounter-flows were inspected.

Regarding the evaluation area, figure 11 displaysthe layout proposed with the resulting necessary

movements of the evaluators. The planningof the evaluation area starts with the inspectionthat the area needs to accomodate 4 AE engines atthe same time, according to the lead times of thepreliminary activities.

The reception area is now organized and seg-mented by engine. Moreover, for the reception of

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Figure 11: Future layout of the evaluation

each engine it is made two differrent lines, for thecritical and non-critical parts, with the objective toenhance the visual management of the stations.

Furthermore, the red lines of figure 6 are now ex-tinguished with the employment of additional mea-suring devices inherent to each workbench. It isalso observable that the area can accomodate upto 10 evaluators wihtout additional implementationcosts, in case the market demand increases or thecurrent worforce is not able to adress the workload.

As a final note, the improvements result in thereduction of the waiting waste concerning the timethe operators take to find parts in the reception anda reduction in the avoidable motion waste with theallocation of easy to access measuring devices to allevaluators.

5.4. Finantial Gains AnalysisIn terms of time spent per process and distancestraveled inside the plant by the components, itis clear that the improvements are advantageous.However, the implemantation of the improvementscomes with a cost structure which is segmented inthree major distinct areas related to the three newcenters of cleaning, NDT and metrology.

Concerning the cleaning station, the initial in-vestment is residual, since there is a functionalcleaning machine in storage which is currently notbeing used. The inherent costs of this implemen-tation include the formation of the workforce to belegally able to operate the machine and its periodicmaintenance. Even though some cleaning processesmay take around 1 hour, the actual labour is onlyendured in the first minutes of the activity to setthe machine. For this reason, the addition of anoperator exclusive to the second cleaning center isnot necessary, since the current repair workforce canperform this task in parallel.

Regarding the NDT center, there is also a func-tional cabine not being used, hence the initial in-

vestment is residual. In this segment, the costs aredue to the maintenance, calibration of the devices,technical formation and employment of a new tech-nician exclusive to this operation. In this case theNDT associated labour is extensive thus the addi-tional operator is required full-time.

Concerning the metrology area, it is proposed toemploy a robotic measuring arm system which thecompany has already acquired in previous years.The cost structure of this segment is constitutedby the maintenance, calibration, formation and anadditional operator responsible for the metrologyexclusively at ful-time.

Table 5.4 summarizes the related costs of imple-mentation, where the initial investments concernthe technical formation and the monthly cost con-cerns maintenance and calibration. The salary val-ues are not displayed.

Table 1: Costs of implementation (Euros)

Ini. Invest. Monthly Cost

Cleaning 2500 0

NDT 3000 242.20

Metrology 2800 0

TOTAL 8300 242.20

Besides these second centers, the multiple linesof assembly and disassembly also come with addi-tional costs with the main contribution being theadditional workforce needed for the operations andan additional cost of necessary tooling. The addi-tional line of disassembly is planned to require 5technicians and the assembly line is expected to re-quire 6 technicians.

Nonetheless, the increase in volume of engines isdone gradually, hence the allocation of workforce isset to follow the revenues curve in order to maxi-mize the resources employment. This factor is im-portant so that the plant is always using the re-sources in the most efficient way throughout theyears, while keeping its costs to a minimum. Table5.4 displays the allocation of the employees accord-ing to the increased volume. It should be noted thatthe increased number of engines is in relation to thepresent year.

In figure 12 the green curve represents the ex-pected increased annual revenues regarding theforecast engine volume and the red curve displaysthe percentage of the additional costs in function ofthe shift in revenues.

Due to the enterprise politics, it is not explicitthe cost of an employee, however the sum of all thecosts including salaries, initial investment, technicalformation and equipment maintenance and calibra-tion, is displayed as a percentage of the total shift in

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Figure 12: Revenues and costs curve according to the annual forecast

Table 2: Allocation of technicians according to en-gine forecast

Eng. Vol. Assemb. Tech. Disassemb. Tech.

2019 28 2 2

2021 42 4 4

2023 53 6 5

2025 55 6 5

2027 56 6 5

revenues. The costs of implementation and work-force are observed to be considerably lower com-pared with the increased gains in revenues. Withthe complete population of the stations and theplant working at full capacity (expected in the yearof 2027), the increase in revenues equals 61 millioneuros with an increased cost in the order of magni-tude of 0.1%.

With this being said, the achieved plant setup en-ables an increased capacity of engine volume witha residual inherent cost. Moreover, the plant flexi-bility is reflected in the control of the costs accord-ing to the market demand without jeopardizing thequality of the operation.

6. ConclusionsThe present paper employs Lean tools to first diag-nose the issues of the enterprise when an increasedclient demand is forecast and used of the same Leantools to plan the future state of the plant. Withthe Takt Time settled, it is concluded that the im-provements enable the possibility for the companyto fulfill the orders of the increased demand.

Furthermore, the improvements were carefullyplanned to ensure the plant runs smoothly duringboth higher or lower work volumes. This is due tothe fact that besides the increased capacity enabledby additional centers with additional machinery, theproposed solutions increase the multifunctionalityof the workers. For this reason, even though thefuture state is planned and has not yet been ex-

perimented, the company can be confident that theimprovements hereby proposed provide a consider-ably better preparation regarding the client demandfluctuation at an almost residual cost.

To summarize, the following points regard the fi-nal achievements:� Layout proposal for a functional future plant

state;� Reduction on the TAT from 75 to 51 days to

assure the client demand;� Aggregated value to the company with high

gains in terms of revenues with low investmentcosts.

With this being said, the application of the Leanmethodology tooling has enabled the MRO to ef-fectively reorganize its maintenance line to complywith the market demand precondition.

References[1] Greg Lane. Made-to-Order Lean: Excelling in a

High-Mix, Low-Volume Environment. 2007.

[2] Hiroshi Katayama. Legend and Future Hori-zon of Lean Concept and Technology. ProcediaManufacturing, 2017.

[3] Paulina Rewers, Adam Hamrol, Krzysztof Zy-wicki, Mariusz Bozek, and Wojciech Kulus. Pro-duction Leveling as an Effective Method for Pro-duction Flow Control - Experience of Polish En-terprises. Procedia Engineering, 2017.

[4] Nor Azian Abdul Rahman, Sariwati MohdSharif, and Mashitah Mohamed Esa. Lean Man-ufacturing Case Study with Kanban System Im-plementation. Procedia Economics and Finance,2013.

[5] Daniel T. Jones James P. Womack. Lean Think-ing : Banish Waste and Create Wealth in YourCorporation. 1996.

[6] John Shook Mike Rother. Learning to See:Value Stream Mapping to Add Value and Elim-inate MUDA. 1998.

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