paper original

ORIGINAL ARTICLE

Applying lean manufacturing system to improvingproductivity of airconditioning coil manufacturing

Biman Das & Uday Venkatadri & Pankajkumar Pandey

Received: 18 March 2013 /Accepted: 4 October 2013 /Published online: 24 November 2013# Springer-Verlag London 2013

Abstract The main objective of this investigation was toimplement lean manufacturing system (LMS) to improveproductivity of airconditioning coil manufacturing at BlueStar Limited. LMS was successfully employed to improvecoil manufacturing productivity or output by 77 % or from121 coils to 214 coils per shift. The LMS tools; such as valuestream mapping, single minute exchange of die, and Kaizenwere employed to reduce the setup time of coil expandermachine from 60 to 20 min, an improvement of 67 %. Theincrease in percentage value addition (%VA) of the coil shopwas from 5 to 12 %, an improvement of 140 %. Theimprovement, especially in coil expander machine wasachieved through Kaizen (continuous improvement) targetingdesign and work method changes. The specific innovativedesign changes or improvements made in the expandermachine to reduce the setup time included the application of:(1) gear rack and gear pinion mechanism, (2) spring and camand lever mechanism, and (3) one touch mechanism in thevarious components of the machine. Many method Kaizenswere also proposed to simplify the setup procedure byeliminating waste (muda) from the setup of expander. Otherbenefits were obtained through reduction of work-in-processinventory, which in turn reduced the shop floor congestionand coil damage due to extra coil handling and improvedworkplace safety.

Keywords Leanmanufacturingsystem(LMS) .Singleminuteexchangeofdies (SMED) .Valueadditionpercentage (%VA) .

Work-in-process (WIP) inventory . Kaizen design and workmethod changes

1 Introduction

Lean manufacturing system (LMS) is a philosophy or conceptthat aims to improve productivity and reduce waste. Leanmanufacturing endeavors to use less of everything: lessinvestment in equipment and tools, less manufacturing space,less workers, and less engineering time in product and processdesign [13]. The reduction of waste can be in inventory orresources such as manpower, equipment, or floor space.Examples of waste reduction include the reduction of processdefects, less scrap, and low inventory [10]. Vinodh et al. [20]maintain that sustainable benefits can be obtained fromreduction of work-in-process, elimination of potential wastefrom damaged products and lesser floor space utilization. Theobjective of lean manufacturing is to reduce waste in terms ofwaiting time, setup time and work-in-process (WIP) inventory[9]. Waste specially in the context of the manufacturingenvironment or company means redundant application ofresources that does not contribute value to the product, forwhich the customer is unwilling to pay. Some of themanufacturing wastes are overproduction, WIP inventory,finished parts inventory, inappropriate processing,transportation, defects, and scrap [11].

The implementation of lean manufacturing philosophy orconcept in the various manufacturing sectors has beendocumented in the literature in recent years. The analysis ofcase studies dealing with the application of leanmanufacturingcan be found in steel production [1], aerospace manufacturing[2], electronic manufacturing [3], automotive production[7, 19], and aircraft manufacturing [21]. Patnayak et al. [16]combined lean manufacturing with cellular layout to improvethe efficiency of ammunition components manufacturing. Thepresent investigation was conducted at Blue Star Limited,Dadra Plant, India, engaged in manufacturing airconditioningcoils and in particular condenser and evaporator coils for

B. Das (*) :U. Venkatadri : P. PandeyDepartment of Industrial Engineering, Dalhousie University, Halifax,NS, Canadae-mail: [email protected]

Int J Adv Manuf Technol (2014) 71:307–323DOI 10.1007/s00170-013-5407-x

airconditioning systems. The main objectives of thisinvestigation were to (1) present an overview of LMS; (2)state the relevant information about the manufacturing plant,product, and processes; and (3) implement a leanmanufacturing system to improve productivity ofairconditioning coil manufacturing at Blue Star Limited.

2 Lean manufacturing system: an overview

The Toyota production system (TPS) [15] was introduced tothe west as lean manufacturing by Womack and Jones [23].Lean thinking is a management philosophy that focuses onreduction of what is seen as waste in an organization. A LMShelps to reduce waste in the manufacturing process and permitsthe company to focus on customer value [22]. Dombrowaskiet al. [6] maintain that LMS provides a holistic strategy toeliminate waste in processes, achieve high product and processquality, and reduce lead time. They also emphasize that LMS isa company-specific compilation of rules, standards, methods,and tools, and provides an appropriate underlying philosophyand culture for the comprehensive and sustainable design formanufacturing products.

TPS is often described by mean of a house (Fig. 1) [8]. Onepillar of the house represents just in time (JIT). JIT as one ofthe key principles of lean manufacturing suggest that, insteadof conventional approach of pushing value forward, customershould be allowed to “pull” the value as and when needed.This approach helps in avoiding waste of over production.The other pillar, Jidoka, is about ensuring that quality productis made and any opportunity to produce defects is eliminated.Poka yoke or fool proofing is one of the most popular termused in lean manufacturing, which means to design a systemwhich has a capability of preventing a defect and if a defectoccurs, detecting the defect itself. Six-sigma has also gainedground as an approach to optimize process performance. At

the base of the TPS house is Heijunka, or leveling, whichmeans to carry out production in such a way that allows betterutilization of resources. The stable and standard work isabsolutely essential for any organization wanting to practicelean manufacturing. Unless the work practice is standardized,it is not possible to improve the process continuously andsustain improvement. Another part of a TPS house foundationis Kaizen, which means continuous improvement. Kaizen as astructured part of an organization provides a frame work forpeople to get involved in the endeavor of continuousimprovement. The involvement of people is achieved bymotivating them to propose ideas for improvement, andsystematically implementing and sustaining those ideas.Under such a system, everybody can suggest an idea forimprovement and all the good ideas are rewarded byrecognizing their involvement in an appropriate form. Leanmanufacturing as a philosophy has focused on five basicprinciples as follows:

1. Understanding customer value: Customer is at the centerstage of any exercise done in the organization. Thecustomer is willing to pay only for the value of the productand the one that helps in making the necessary change inthe form of product which is considered as value-added(VA) activity.

2. Value stream analysis: Having understood the value forthe customers, the next step is to analyze the businessprocesses to determine which ones actually add value.

3. Flow: The focus should be on continuous flow of thematerial in small quantity rather than moving material inlarge batches. This approach helps in reducing work-in-process inventory.

4. Pull: The production on any process should be triggered bydemand of the process that follows it. No material shouldbe processed unless it is needed by a downstream process.

5. Perfection: The elimination of nonvalue added (NVA)activity is a process of continuous improvement andrequires structured framework like Kaizen to be practicedwithout end.

2.1 Lean manufacturing tools

Lean manufacturing offers many tools, which can help inproducing the value to a customer in a leaner way. Some ofthe most widely used tools are value stream mapping (VSM),5 S, total productive maintenance (TPM), single minuteexchange of dies (SMED), JIT, and Kaizen.

2.1.1 Value stream mapping

Value stream mapping widely known as VSM is one of themost powerful tools of lean manufacturing. VSM mainlyFig. 1 Toyota production system (TPS)

308 Int J Adv Manuf Technol (2014) 71:307–323

targets the stream of the value and, in the process, seeks toidentify the areas of improvement. VSM focuses on value inthe context of what the customer is willing to pay or whatmakes the product gain customer satisfaction [17]. Theprimary goal of VSM is to estimate the lead-time associatedwith a certain product flow throughout a system [18]. Thewhole exercise of VSM can be divided into four key steps: (1)identify the product family, (2) create a current state valuestream map, (3) create a future state value stream map, and (4)create an action plan.

VSM is always regarded as the starting point of systemimprovement practices, as it helps in identifying the areaswhere the improvement efforts should be concentrated. Themain advantage of VSM is that it gives an opportunity toexamine the chain of process and focus only on the valueadded activity. The main index of VSM is percentage valueaddition (%VA) of the system.

2.1.2 5 S

5 S is one of the most useful tools of lean manufacturing,widely used to keep the working area neat, clean, and safe.The name 5 S derives from the first letter in the five Japanesewords: Seiri, Seiton, Seison, Seiketsu, and Shitsuke. TheJapanese words’ meanings in English are sort, straighten,shine, standardize, and sustain. Normally, 5 S is implementedin step-by-step manner. In the sort phase, all the items lying atthe work center are segregated as necessary and unnecessaryitems. Thus, all this unnecessary items are removed in asorting phase. Then, in straighten phase, all the necessaryitems are arranged, and their location is defined. In a shinephase, the every corner of the workplace is neatly cleaned, andthe sources of contamination like dust, oil are identified. Atthe end of the shine phase, the house keeping part of 5 S isconsidered to be complete. In the standardize phase, theprocedure is defined to sustain the improvement. In the sustainphase, the comprehensive program is developed to trainpeople for good work practice and motivate them to stick tothe working rules.

2.1.3 Total productive maintenance

TPM is a management approach to maintenance that focuseson involving all employees in an organization in equipmentimprovement. It consists of a range of methods, which areknown from maintenance management experience to beeffective in improving reliability, quality, and production.

2.1.4 Single minute exchange of dies

SMED is one of the most desirable lean manufacturing toolsused to reduce the setup time of a machine. The SMED

basically focuses on reducing setup time by converting allinternal activities into external activities and simplifyinginternal and external activities [12]. Internal activities arethose activities that need the stoppage of machine, where asexternal activities are those that do not need the stoppage of amachine and can be done while the machine is being used forproduction. SMED technique also suggests the use of onetouch mechanism like one touch screw and one touch holderto reduce the setup time further. The SMED project should beimplemented in four phases. In the first phase, the whole setupprocedure should be analyzed. One of the popular ways is todivide the whole setup procedure into small elements.Videotaping of setup operation can be done to study theprocess in detail. In the second phase, the distinction is madebetween external and internal activities. In the third phase,effort is made to convert as many internal activities as possibleto external activities. The internal activities are simplified bymaking design change or work methods change. To achievethe simplification in the design or method, the brain stormingsession is conducted with operators who get involved inregular setup activities. In the fourth phase, the new methodof setup is defined and documented.

2.1.5 Just in time

JIT focuses on the flow of material in the production systemand inventory level. The aim is to keep the level of inventoryto a minimum. This is achieved by allowing each operation topull the material from the precedential operation rather thanpushing material in the production system. Kanban, a signalmethod, is used to indicate the need of replenishment orproduction.

2.1.6 Kaizen

Kaizen is one of the most popular terms used in the field oflean manufacturing. Kaizen means continuous improvement.The environment is created at the workplace that motivatespeople involved in the day-to-day work to contribute to makethe method of work more efficient or better by continuouslyimproving it.

3 Manufacturing plant, product, and processes

3.1 Manufacturing plant

Blue Star Dadra Plant is equipped with latest manufacturingtechnologies and quality standards. The plant employment in2010 was 425 that included 75 management staff and 350operators. The Dadra plant’s functional departments includeManufacturing Engineering, Production, Production Planning

Int J Adv Manuf Technol (2014) 71:307–323 309

and Control, Quality Control, Maintenance, Reliability,Dispatch, Human Recourses, and Finance. It also has afurbished research and development department with facilitiesfor performance testing simulators for all kinds of products.The plant is recognized for its initiatives in the field ofmanufacturing practices and people’s involvement in day-to-day continuous improvement activities. All the manufacturingfacilities at the plant are ISO 9001:2008 certified and poweredthrough integrated Enterprise Resource Planning software.Most of the components go through stringent test on reliabilityand performance at test labs.

3.2 Product

Blue Star offers a wide range of contemporary windows andsplit airconditioners, among others. The company alsomanufactures and markets a comprehensive range ofcommercial refrigeration products and services that cater tothe industrial, commercial, and hospitality sectors. In thesegment of airconditioning systems, Blue Star has acomprehensive range of products such as chillers with screwand hermetic scroll compressors, a wide range of air handlingand fan coil units, ducted package, and ducted splitairconditioners including the heat pump versions. Thecompany also offers unitary products such as window andsplit airconditioners, deep freezers, cold rooms, water coolers,and specialized airconditioners for precision controlapplications.

3.3 Process

The manufacturing process of Dadra plant can be divided intofour categories: coil shop, fabrication shop, paint shop, andassembly lines. The focus of this investigation is coil shop.The other shops are briefly described below.

3.3.1 Coil shop

Coil shop is one of the most important divisions of Dadraplant. Coil plays a very important role in airconditioningsystem. The whole performance of airconditioning systemdepends on heat transfer rate of condenser and evaporatorcoils. The heat transfer rate depends on the manufacturingquality of the coil. Consequently, it is essential to producegood quality coils. The plant is equipped with the mostadvanced technology to produce condenser and evaporatorcoils. The important machines in the coil shop are fin pressmachine, tube bending machine, expander machine, auto-brazing machine, coil bending machine, water deep testingsetup, and drying oven. The flow diagram of coil shop isshown in Fig. 2.

At the fin press, the aluminum sheet is cut according to thewidth of the coil. This piece of punched coil is called “fin.”The fins are stacked according to the height of the coil. Thereare two types of coil used, white coil and coated blue coil. Thecomplicated operation of fin punching is done using veryprecise tool set, mounted in fin press die. Some of the keyparts of die are punch, side cutter, row cutter, split cutter,enhance cutter, feed fingers, slitter, and final cutter. The dieis of progressive type and the operation can be divided into tenstations: retard station, form station, draw station, piercestation, enhance station, re-flare station, edge trim station,row cutting station, feeding station, and final cutting station.

At the hair pin bender machine, the copper tubes are bentand cut into size according to the height of the coil. Main toolsof hair pin bender are cutter, mandrel rod, guide tube well-meant, front plate, upper locking pin, lower locking, shaftcollar, drive belts, and bullets for hair pin bender.

At the lacing table, the punched fins and copper tubes areassembled by inserting tubes into fins. Then, the assembly istaken to expander machine. At the expander machine, the coilassembly is mounted vertically on the machine, and theexpansion bullet is passed through inner grooved copper tubes.After expansion, the fins get firmly locked with copper tubes.The coils then pass through the auto-brazing machine to closethe open ends of the coils. The coils are then taken to coilbending machine, when bending is needed in the coil. Theheader and capillaries are then brazedwith the coil at themanualbrazing station. Finally, the coil is tested for brazing joint atwater deep testing stage and subsequently dried in the oven.

3.3.2 Fabrication shop

The sheet metal components are produced in fabrication shop.The cold rolled close annealed galvanized coil is used as a rawmaterial. The key processes that are to be carried out in thefabrication shop are coil slitting, punching, embossing,bending, spot welding, and gas welding. After finishingoperations in fabrication, parts are sent to powder coating shop.

3.3.3 Paint shop

The basic function of paint shop is to paint components forpreventing rusting and providing a long working life. Thepowder coating paint shop is equipped with hi-tech automaticNordson made powder-coating booth, the pretreatmentsection, and automatic overhead conveyor and curing oven.The part is loaded on hangers, mounted on overheadconveyor, and passed through pretreatment section. Afterpassing through the pretreatment process, the panels enter intothe water drying oven. The component is then cooled throughnatural cooling. From there it enters the powder coating booth


where the panel is coated with powder. Then, the componententers into powder coating oven, where the dry powder isbaked. The panel then enters into the powder curing oven,where hot air is blown over the panel. There dry powder getsmelted, creating a layer of film of paint. The process creates ahard coating on the panel, and subsequently, the panel isunloaded from the conveyor.

3.3.4 Assembly shop

The plant has a total of seven assembly lines to cater to widerange of products. All the assembly lines are equipped withautomatic conveyor system, and pneumatic tools are used forcarrying out the assembly operation. All the lines have inbuilttesting facilities for the final performance testing of theproduct. The final product is assembled sequentially onconveyors, with built-in quality checks during assemblyoperations. Pneumatic tools permit torque-controlled rigidity,and specially coated corrosion-resistant hardware providesfirm locking. Brazing of system tubing and the refrigerantcircuit is done on line under controlled conditions.

4 Implementation of lean manufacturing system

Implementation of LMS is a strategic move and requires thecommitment from all levels of the organization. It requirescommitment from the top management and also theinvolvement of the middle management and operators. Tocarry out LMS as an activity, a team is formed which includesLMS co-coordinator and cross-functional team. The leanmembers are comprised of manufacturing engineeringmanager, production manager, manufacturing engineer,production engineer, quality engineer, maintenance and safetyengineer, research and development engineer, shop supervisor,and senior operators. Necessary orientation and training areprovided to the members of LMS before embarking on LMSimplementation. Implementation of LMS usually starts withmapping current process performance level using VSM. Tocarry out VSM, the first step is to identify the representativeproducts for which the VSM will be performed. Usually, high

moving models that are linked with most of the availableprocesses in the system are chosen as representative products.The data related to selected products, such as process time,work-in-process inventory level, setup time, machineutilization fraction, and number of operators involved in themachine/ facility, are collected for each product. Then thepercentage value addition (%VA) is calculated by summingup total process time at each stage of the operation divided bythe total time needed for the product to pass through theprocesses that includes value added and non value added times[Σ(VA+NVA)]. The detail of calculation is shown in Fig. 5.The scope of possible improvement is then identified andstructured or unstructured brain storming sessions areconducted to generate ideas for improving percentage valueaddition (%VA). After idea generation sessions, each idea isassessed for its viability, cost, and effectiveness. Then,depending on the nature of improvement suggested, varioustools of lean manufacturing like SMED, kaizen, just in time,line balancing, and fool proofing are applied to solve the rootcause of inefficiency. Tools like process failure mode andeffect analysis (PFMEA) can be used for risk assessment andpreventive action plan. Control plan is used to sustain thenewly defined process. It should be recognized that apart fromLMS tools, it is necessary to apply the principles and conceptsof engineering analysis, such as work design and workmethods engineering. Work design employs operationsanalysis to study all productive and non-productive elementsof the operation to increase productivity per unit of time and tominimize unit cost [14]. The steps that should be followed inthe implementation of LMS are systematically stated below.

4.1 Implantation approach to LMS

4.1.1 Value stream mapping—current state

Tomap the process, it is necessary to collect the various relevantdata regarding eachworkstation likemachine utilization, numberof operators involved, number of setups per shift, number ofmachines, and setup time. Table 1 contains some of theimportant information data, which will be used to analyze thecurrent state of the coil shop. It is worth noticing that despite very

Fig. 2 Flow process ofthe coil shop


low setup time, the machine utilization of auto-brazing machineis only about 27 % due to its very high production rate,whereas the same is 31 % for expander due to very high setuptime.

To map the process and calculate the VA and NVA times, itis necessary to calculate WIP inventory level at each stage ofthe operation. For the Dadra plant, the product mix is large andthe batch size varies with the size of the customer order.Consequently, some assumptions are made to simplify thecalculations of WIP, as follows:

1. Average time for manufacturing fin at fin press is takenas 2 min.

2. WIP between fin press and expander=(setup time ofexpander−setup time of fin press)/2. It should be notedthat WIP between fin press and expander cannot exceedthe batch size.

3. WIP between expander and auto-brazing=WIP betweenfin press and expander.

4. WIP after auto-brazing=WIP between expander and auto-brazing (due to high production rate of auto-brazing).

Figure 3 shows the WIP location at the different stages ofthe process. It is evident that the WIP between fin press andexpander is high due to the difference in setup time. TheWIP between expander and auto-brazing is high due todifferent number of facilities, setup times, and productionrates. WIP after auto-brazing is high due to high productionrate of auto-brazing machine. Figure 4 shows the layout of thecoil shop.

To carry out the process mapping of the coil shop, somehigh moving models are selected and the process times arecollected for each operation involved in the coil shop. Table 2provides relevant data for the selected coil codes. Table 3shows the cycle time [((setup time/batch size)+processtime)×(2/number of facilities)] for each operation. FromTable 3, it is concluded that in most of the cases, expander isthe bottleneck in the coil shop.

4.1.2 Value stream mapping analysis and suggestions

Figure 5 shows the VSM diagram for the model CODX-18013-00. VSM analysis reveals that the percentage valueaddition (%VA) is 4.95 %. It is observed that the high setuptime of expander is making expansion operation a bottleneckand causing a high WIP inventory and preventing one pieceflow across the shop floor. This high setup time causes thematerial to be pushed by each workstation to sequentialworkstation, which is not ideal in terms of leanmanufacturing.The high WIP level causes material handling problem, coildamage, and other quality problems. To reduce the WIP levelbetween fin press and expander, it is imperative to reduce thesetup time of expander, so that instead of pushing the batchmaterial to the expander, it will allow the expander to pull thematerial from the fin press. Also to reduce the WIP betweenthe expander and the auto-brazing, the production rate of theauto-brazing machine should be reduced. Necessaryadjustment should be made in speed and number of operatorsto attain a balance between output of two expanders andoutput of auto-brazing machine. Furthermore, once the setup

Table 1 Coil shop machinedata (current state) Machine

nameNumber ofmachines

Number of operators/machine

Setup (min) permachine setup

Average setupsper shift

Utilization %per machine

Fin press 2 1 10.00 5 0.70

Hair pin bender 2 1 10.00 5 1.00

Expander 2 2 60.00 5 0.31

Auto-brazing 1 6 5.00 10 0.27

Coil bending 1 2 3.00 0-10 0.36

Water testing 2 1 0.00 4 1.00

Fig. 3 Work-in-process (WIP)inventory location in coil

shop. identifies

location of high WIP


time of expander is reduced and output balancing is achievedbetween the expander and the auto-brazing machine,necessary adjustment should be made in the capacity of leantesting operation by addition of testing stations. Finally, thelayout of coil shop should be modified to facilitate storage oftested coils, once the entire process is balanced. There is noneed of storage facility for storing semifinished coils.Necessary changes should be made in the material handlingand storage system. VSM suggestion can be implemented intwo phases. In the first phase, setup of expander machine canbe reduced by SMED techniques. In the second phase, thecycle time balancing can be done among expander, auto-brazing, and leak testing machines. The layout can bemodified to create more space and storage racks can bemovedat the end of a shop to store coils for assembly.

4.1.3 SMED project for expander machine

From the findings of VSM, it is crucial to reduce the setuptime of the expander to minimize the WIP and stream line theprocess. Consequently, it is vital to understand the machineconfiguration and setup procedure. Figure 6 shows themachine with operators and key components of the machine.

The current setup time of expander is about 60 min. Thetarget is to reduce the setup time to minimum possible levelusing SMED techniques. To achieve this goal, the

videographic study of setup of expander is carried out tounderstand the setup procedure and identify the areas ofimprovement. The whole process of setup is then divided intosmall elements so as to assess whether the element is externalor internal. External elements are those that can be performedwhile the machine is working, whereas for carrying outinternal elements, machine needs to be stopped. In case theelement is internal, the possibility of converting that elementinto external element is investigated. Each element isexamined to identify the scope of improving the element timeby improving design and work method that involve human,machine, and material. Key steps in setup of expander areholding block setup, back plate setup, row change setup,receiver circuit setup, door plate setup, and side stopper setup.The steps are stated below:

Step 1 Holding block setup: For adjusting the height, theholding block is loosened up and hooked up with theram of the expander. The ram of expander is thenadjusted by using control panel. The rough referenceis taken by the scale attached at the one side of themachine. One operator controls the panel and makesthe necessary adjustment according to the directiongiven by the other operator. Once the height of

Fig. 4 Coil shop layout (current state). Note: Racks are used for WIP storage

Table 2 Process time (min) for each machine/facility (current state)

Coil code Finning Expander Auto-brazing Leak testing

CODX-18D013-00 1.69 1.30 0.29 3.27

CODX-D260-00 0.87 0.80 0.21 3.19

CODX-12D025-00 2.11 1.30 0.20 3.31

COCD-16D177-00 2.27 1.30 0.45 3.15

Table 3 Cycle time (min) for each machine/facility (current state)


CODX-18D013-00 2.09 3.70 0.97 2.18

CODX-D260-00 1.27 3.20 0.82 2.13

CODX-12D025-00 2.51 3.70 0.79 2.21

COCD-16D177-00 2.67 3.70 1.30 2.10

Set up time 10.00 60.00 5.00 0.00

No. of Facilities 2.00 2.00 1.00 3.00

Batch Size 25.00 25.00 25.00 25.00


expander is setup, the holding blocks are tightenedfirmly by using pneumatic torque wrench.

Step 2 Back plate setup: The back plate is a part of theexpander that supports the coils from behind duringthe expansion process. The plates are made up ofaluminum with steel structure supporting it. Theweight of each plate is around 50 lbs. The platesare lifted manually by two operators and mountedon vertical frame of the expander. The plates are thenadjusted for its horizontal inclination. The processinvolves trial and error. Awrong alignment can causequality problems. There is also a significant risk ofsafety hazard due to heavy weight of plates.

Step 3 Row setup: row setup is needed whenever setup isdone for a coil which has different coil thickness(number of layers) with respect to the previous coil.

The aluminum frame is positioned vertically to set therow and disconnected and pushed forward orbackward depending on the row of the coil for whichthe changeover (setup) is done. There is a safetyhazard or risk due to the possibility of the heavyaluminum frame getting toppled and causing an injury.

Step 4 Receiver circuit setup: in this step, the receivers are fitin the receiver plate by hammering the receivers inreceiver plate holes. There is a push fit joint betweenthe receiver and the receiver plate.

Step 5 Door plate setup: door plates are mounted on the doorframe. The number of door plates to be mounteddepends on the height of a coil. Door plates are madeup of aluminum with mild steel structure providingthe necessary rigidity to the entire structure. Eachplate weighs around 50 lbs. The plates arepreassembled with L-shape door plate supports. Thewhole assembly is lifted manually and mounted onthe door frame. The surfaces of all door plates arethen aligned by making fine adjustment in jointsbetween the door plate and the door plate support.

Step 6 Side stopper setup: In this step, the side stoppers aremounted in the groove of the door plate. The heightof the side stoppers depend on the width of the coil.For multiple rows of the coil, additional heightattachment is mounted on the side stopper.

Before attempting to improve the process, it is vital tounderstand the process in detail first. Figure 7 shows thecurrent expander machine with key components. Workmethods engineering study of the setup procedure is done byvideo analysis of the whole procedure. Table 4 is the detailedelement-wise analysis of the setup of expander. The wholesetup is divided into 18 different elements (10–180). Eachelement is defined as external or internal element (in thepresent instance all the elements are internal).

Model :Batch :

Supplier PPC

Pt 1.69 Pt 1.09 Pt 3.02 Pt 1.30 Pt 0.29 Pt 0.00 Pt 0.79 Pt 3.27MP 1.00 MP 1.00 MP 4.00 MP 2.00 MP 6.00 MP 2.00 MP 1.00 MP 2.00ST 10.00 ST 10.00 ST 5.00 ST 60.00 ST 10.00 ST 3.00 ST 0.00 ST 0.00WIP 1.00 WIP 1.00 WIP 25.00 WIP 25.00 WIP 25.00 WIP 1.00 WIP 1.00 WIP 1.00Shift 1.00 Shift 1.00 Shift 2.00 Shift 2.00 Shift 1.00 Shift 1.00 Shift 1.00 Shift 2.00

NVA 0.00 11.69 11.09 80.4192..5

017.14 3.00 0.79 3.27

VA 0.00

CODX-18D013-00 (current state)25.00

VA=∑Pt NVA=∑((Pt*WIP)+ST) Percentage value addition (%VA) = (∑VA/(∑VA+∑NVA))*100

∑NVA=219.89

∑VA=11.44

% VA=4.95

1.69 1.09 3.02

Manual brazing

Water testing

Fin press HPB

1.30 0.29 0.00

Lacing ExpanderAuto

brazingCoil

bending

Customer

0.79 3.27

I I I II I I I I

Fig. 5 Value streammap (VSM)—current state (CODX-18013-00). PPC Production planning and control, Pt process time (min),MP manpower (no.),ST setup time (min), WIP work-in-process inventory (no.), shift (no.)

Fig. 6 Expander machine image (with key components). 1 Back plate,2 holding block, 3 receiver plate, 4 door plate, 5 door plate support, 6side support


To generate ideas for improvement, the Gemba (hands-on-Kaizen) is conducted. The participants were shop floorengineers and experienced operators. Following suggestionsare made after brain storming sessions at the workplace. It isexpected that the design changewill eliminate all the nonvalue-added contents, and thus, element time will be reducedaccordingly. The suggestions are made to simplify the designof the key component like receiver plate, aluminum frameholding mechanism, holding block, back plate, door platesupport, door plates, etc. Five design Kaizens (Figs. 8, 9, 10,11, and 12) were proposed to change the design of key setupelements or components. Figure 8 (Kaizen 1) shows the designchange (before and after) of the row change mechanism.Earlier the aluminum frame of the machine had to be adjustedmanually for different number of coil row. The operation wasvery risky due to safety hazard and took a long time to perform,as the aluminum frame had to be dismantled and moved

manually, depending on the number of rows of the coil. Inthe proposed Kaizen 1, the aluminum frame is fixed with anupper plate, which works as a gear rack and is connectedwith apinion gear. Furthermore, the upper plate is locked with lowerplate with grooved joint, enabling plates to slide over eachother by gear rack and gear pinion and also keeping them incontact thus avoiding the risk of toppling of aluminum frame.Figure 9 (Kaizen 2) shows the design change of the back platemounting mechanism. Earlier, the back plates were adjustedvertically by lifting the heavy back plate (50 lbs) manually andaligning the plate surface visually, which consumedconsiderable amount of time and was prone to visual error. Inthe proposed Kaizen 2, the round spacer of the back plateholder is changed to a rectangular spacer for easy and accuratevertical referencing from the scale. In addition, the scales aremounted on both side of machine. In the proposed method, theback plate bolts are tightened at the same level first, and then

Fig. 7 Expander machine frontand top view (current state).1 Holding block, 2 back plate,3 back plate washer, 4 receiverplate, 5 receiver, 6 aluminumframe, 7 door plate, 8 scale,9 side stopper, 10 doorplate support


back plates are mounted directly over them. This newoperation eliminates the need of visual adjustment.

Figure 10 (Kaizen 3) shows the design change of door platemounting mechanism. Earlier, door plates were fixed in thegroove of door plate support frame. Due to the open groove,the plated setting was disturbed during production requiring itto be readjusted during setup. In the proposed Kaizen 3, thecontinuous groove is replaced by a fixed hole joint and thusfixing the door plates firmly in the position. Figure 11 (Kaizen4) shows the design change of receiver plate. Earlier, thereceiver plate had a push fit feature for fitting receivers in it.It took a long time to fix the receiver since each receiver washammered in a push fit joint. Hammering was causing wearand tear of the plate requiring insertion of packing to fit receivertightly with plates. In the proposedKaizen 4, new receiver platewas designed with enough clearance between receiver pin andreceiver plate hole to fit the receiver easily and then locking thereceivers using spring, cam, and lever mechanism. Newreceivers are designed with a grooved pin, which gets locked

with the central movable plate of cam liver receiver plate.Figure 12 (Kaizen 5) shows the design change of side supportmounting mechanism. Earlier, the door plate had a continuousslot to fit the side stopper according to the width of the coil. Theoperation was taking more time as trial and error was involvedin the process. In the proposed Kaizen 5, the continuous slotwas replaced with numbered round slots, with center pitchdistance of 2.54 cm. The side stopper can be directly fitted tothe slot according to the width of the coil; consequently, noadjustment is needed. All these design Kaizens are expected toreduce the element setup time considerably (by 75 %).

The improvements in other Kaizen targeting changes inwork method are as follows:

& Provide scale at both side of the expander to avoid visualadjustment error.

& Keep the expander accessories on a movable trolley,which can be easily brought near when the setup is goingon to save travelling time.

Table 4 SMED of expander (current state)

Operationnumber

Operation External/internal

Total time(min)

Cumulativetime (min)

Remark(s)

10 Loose the stopper Internal 0.52 0.52 Tool is brought from anothermachine. No coordination

20 Take the ram down and touch to holding block Internal 0.18 0.70 NA

30 Lock the holding block hook with ram Internal 0.30 1.00 Hammering had to be done. Fitmentcould be made one touch

40 Loosen the holding block Internal 0.57 1.57 Single tool is used by both of theoperator

50 Take the ram up with holding block Internal 0.12 1.68 NA

60 Adjust the height Internal 0.37 2.05 Manually done

70 Fasten the holding block Internal 1.20 3.25 Single tool is used by both of theoperator

80 Verification of holding block fitment by takingblank stroke

Internal 1.32 4.57 Need to understand the requirementof this move

90 Change the row as per coil rows Internal 9.81 14.38 Whole adjustment is done manuallyusing a spanner

100 Adjust and fit the back plates Internal 11.23 25.61 Whole adjustment is done manuallyusing a spanner

110 Adjust door plate Internal 10.50 36.11 Whole adjustment is done manuallyusing a spanner

120 Receiver fitment in plate as per circuit Internal 9.46 45.57 Whole adjustment is done manuallyusing a spanner

130 Make coarse setting of side stopper Internal 3.65 49.22 Whole adjustment is done manuallyusing a spanner

140 Load the coil and fine adjustment of side stopper(still kept a bit loose)

Internal 1.90 51.12 Whole adjustment is done manuallyusing a spanner

150 Lift the coil and check the alignment, adjust the sidestoppers, and adjust the height

Internal 2.50 53.62 Visually done

160 Tighten the height stopper Internal 1.40 55.02 Manually done

170 Bring the tube sheet from the rack Internal 0.50 55.52 Delay

180 Take the coil down and fit the tube sheet, tighten theside stopper

Internal 2.45 57.97 Manually done


& Provide separate tool sets for operators involved in setupto avoid waiting and delay.

& Use pneumatic tools in place of manual tools.& Provide individual sets of side stopper for one to four rows

of coils to avoid side stopper height setup (one touch).

4.2 VSM—future state

Table 5 shows the proposed method of setup. Figure 13 is theprojected view of expander machine after implementation ofthe Kaizens.

Before: The aluminum frame of the machine had to be adjusted manually for different row of coil. The risky operation due to safety hazard and requires long time to perform.

After: The aluminum frame is fixed with a upper plate which work as a gear rack and is connected with the pinion gear. Also the upper plate is locked with lower plate with grooved joint, enabling plates to slide over each other by gear rack and gear pinion and also keeping them in contact, thus avoiding the risk of toppling of aluminum frame.

Fig. 8 Design change of rowchange mechanism(Kaizen 1)

Before: Back plate is adjusted vertically by aligning the plate surface visually, which consumes considerable amount of time and prone to visual error due to circular washer and lack of reference point.

After: The round spacer of back plate holder to be changed to rectangular spacer for easy and accurate vertical referencing from the scale. After tightening back holders, plate should be mounted directly. No need to perform a visual adjustment.

Circular WasherSquare Washer

Fig. 9 Design change of backplate (Kaizen 2)


After performing data analysis and reducing the setup timeof the expander, which was an incentive for making furtherimprovements sequentially, the future state of the coil shop isdetermined. Once the setup time is reduced, the line balancingshould be done between expander and auto-brazing bydecreasing the speed of auto-brazing machine. Afterincreasing the output of expander, sequential facility additionshould be made for leak testing to balance the entire valuechain.

As shown in Fig. 14, the layout of the coil shop is modified.The distance between auto-brazing and expander machine isreduced since space is not needed to store WIP between themachines. In addition, the storage racks are placed at the endof the coil shop to store finished coils Number of coil testing

facilities is increased to balance the throughput time at eachstage of the coil shop. These changes will help in reducingcongestion and coil damage and enhance safety.

Table 6 and Fig. 15 show the projected cycle time of theexpander machine for the selected models. In most of thecases, either the fin press or the expander is becoming anoperation with the longest cycle time. Considering the currentutilization of fin press (70 %), this can be considered as anideal situation. The process is more balanced, and thus, overallthroughput time will be optimized. Figure 16 shows the futurestate of VSM. The percentage value addition is 11.52 %. Oneof the key changes is transformation of the push system intopull system. This will lead to minimum WIP inventory andhigher percentage value addition.

Before: Door plate holder with free end joint which leads to variation and requires resetting during the setup and production.

After: Door plate holder’s free end joint should be fixed to eliminate possibility of variation during production and resetting during setup and production.

Fig. 10 Design change of doorplate support (Kaizen 3)

Before: The receiver plate with push fit feature for fitting receivers in it. Took a long time, wear and tear of plate caused insertion of packing to fit receiver tightly with plates. Receiver had to be fit in the receiver by hammering it in receiver plate holes. (Push fit).

After: New cam receiver plate with enough clearance between receiver pin and receiver plate hole to fit the receiver easily and then locking the receivers by using cam and lever. New receivers with grooved pin which gets locked with the central movable plate of cam liver receiver plate.

Fig. 11 Design change ofreceiver plate and receivers(Kaizen 4)


Table 7 shows the productivity improvement gained throughthe implementation of LMS for the coil code CODX-18D013-00. Significant improvement in percentage value addition canbe gained by implementing lean manufacturing in coil shop.The percentage value addition is expected to rise up to 12 %from the current level of 5 %. The increase in coil output orproductivity was 77%, based on the completed coils per shift. Italso incorporates the one piece flow in coil shop that will reducetheWIP at every stage of the operation. Reductions inWIP willsequentially reduce the coil handling and the resultant damage

of coil. Spacious workplace will help in increasing safety at theworkplace and thus enhance the operator’s morale. As the setuptime is reduced for expander and auto-brazing machines, andthe capacity is increased for coil testing, the overall throughputtime will be reduced significantly.

Since the entire coil shop will be balanced and streamlined,there is no need to run some of the machine in a second shiftunless the overall demand requires a second shift. This willhelp in attaining better control over the production process ofcoil manufacturing.

Before: Continuous slot to fit the side stopper according to width of coil. Involved trial and error and take more time.

After: Round slots to be made at the pitch of 2.54 mm and side stopper should be directly fitted to the slot according to the width of the coil. No adjustment needed.

Fig. 12 Design change of doorplate for easy fitting of sidestopper (Kaizen 5)

Table 5 SMED of expander (future state)

Number Operation Earlier time(min)

Suggestions Expectednew time(min)

Cumulativetime (min)

10 Loose the stopper 0.52 Provide separate tool set for each operator 0.27 0.27

20 Take the ram down and touch to holding block 0.18 NA 0.18 0.45

30 Lock the holding block hook with ram 0.30 Provide separate tool set for each operator 0.17 0.62

40 Loosen the holding block 0.57 Provide separate tool set for each operator 0.28 0.90

50 Take the ram up with holding block 0.12 NA 0.12 1.02

60 Adjust the height 0.37 0.37 1.38

70 Fasten the holding block 1.20 Provide separate tool set for each operator 0.60 1.98

80 Verify holding block fitment by taking blankstroke

1.32 Verify the need of operation 1.32 3.30

90 Change the row as per coil rows 9.81 Design change (Kaizen 1) 2.45 5.75

100 Adjust and fit the back plates 11.23 Design change (Kaizen 2) 2.81 8.56

110 Door plate adjustment 10.50 Design change (Kaizen 3) 2.63 11.19

120 Receiver fitment in plate as per circuit 9.46 Design change (Kaizen 4) 2.37 13.55

130 Side stopper coarse setting 3.65 Design change (Kaizen 5), pneumatic gunto be used to firmly tighten the sidestopper

0.00 13.55

140 Load the coil and fine adjustment of sidestopper (once kept a little bit loose)

1.90 1.20 14.75

150 Lift the coil and check the alignment, adjustthe side stoppers and adjust the height asneeded

2.50 2.50 17.25

160 Tighten the height stopper 1.40 Provide separate tool set for each operator 1.40 18.65

170 Bring the tube sheet from the rack 0.50 Tube sheet to be kept ready and near toworkplace

0.50 19.15

180 Take the coil down and fit the tube sheet, andtighten the side stopper

2.45 Can be avoided 0.00 19.15


5 Discussion

LMS was successfully applied to improve productivity ofairconditioning coil manufacturing. The coil output per shift(of 8 h, 450 min work time, 30 min personal time) improvedfrom 121 coils to 214 coils or productivity improvement of

76%. This was possible through the application of LMS tools.SMED was used for the reduction of setup time of expander.Another LMS tool, Kaizen, was used to make design andwork methods change of the machine components and workelements involved in setup of the expander to reduce the setuptime in multiple stages (continuous improvement) from 60 to

Fig. 13 Expander machine frontand top view (future state).1 Holding block, 2 back plate,3 back plate washer, 4 receiverplate, 5 receiver, 6 aluminumframe, 7 door plate, 8 scale,9 side stopper, 10 doorplate support

Fig. 14 Coil shop layout(future state)


20 min, an improvement of 67 %. LMS tool, VSM was usedto analyze coil manufacturing processes. VSM (current state)revealed that the value addition percentage (%VA) of the coilshop was around 5 %. It also revealed that the setup time ofexpander was the main reason for less value additionpercentage in coil shop and hence emphasized setup timereduction of expander. Furthermore, it indicated that aftersetup time reduction of the expander, it would be necessaryto balance other processes to achieve optimum throughput.VSM (future state) projected the value addition percentage tobe around 12 % after implementation of all the improvementprojects, an increment of 140 % from the current level.Furthermore, reduction of setup time of expander will alsoreduce WIP inventory. This in turn will eliminate the need forstoring WIP among machines and thus save floor space orimprove plant layout. The changes will help to reducecongestion and coil damage and enhance safety at theworkplace.

The reduction in setup time of the expander was achievedthough Kaizens targeting machine component and workmethod involved in the setup of the expander. The designchanges or improvements in setup time of expander included(1) setting up row for the coil with respect to previous coil, (2)mounting and vertical alignment of the back plates, (3)mounting and adjustment of the door plates on the door frame,

(4) fitting the receivers in the receiver plates, and (5) mountingand adjusting side stoppers as per width of coil. Severalinnovative design changes were made that included using gearrack and gear pinion mechanism for row change, usingrectangular spacer and scale on the both side of the machinefor easy alignment of back plates, fixing the location of thedoor plate in door frame to eliminate the possibility ofvariation and need for readjustment, designing receiver platewith spring, and cam and lever mechanism of locking systemfor easy insertion of receivers in plate and one touch lockingand converting continuous groove in door plates to fixed holesfor accurate mounting of side stopper. Additionally, Kaizenwork methods improvement included the provision of: (1)numerical scale on both sides of the expander machine toavoid visual judgment error, (2) movable trolley to facilitateaccessories transportation, and (3) individual (operator) set ofpneumatic tools and side stoppers to avoid waiting and delay.

The success of the LMS application can be attributed inparticular to: (1) top management support for LMSphilosophy and a commitment for continuous improvementthrough providing continuous employment [5], job assurance,and resources; (2) formation of LMS teamwith members fromfunctional departments and appointing lean coordinator andlean associate coordinate for future continuity of the LMSprogram; (3) provision of necessary orientation and training[4]; and (4) collection of relevant and accurate functional(operational) data for the selected products.

It should be recognized that LMS as a philosophy orconcept provides the required environment to reduce waste.However, the design and work methods improvement canonly be achieved through systematic engineering analysis thatincludes work design and work method engineering. Formaking meaningful improvements, often new approach andinnovations are required. To obtain the full cooperation ofwork force for the continuous improvement, the topmanagement must follow the policy of continuousemployment and adapt progressive approach towardsbusiness to provide job security to the workforce.

Table 6 Cycle time (min) of expander machine (future state)


CODX-18D013-00 2.09 2.10 0.97 1.64

CODX-D260-00 1.27 1.60 0.82 1.60

CODX-12D025-00 2.51 2.10 0.79 1.66

COCD-16D177-00 2.67 2.10 1.30 1.58

Set up time 10.00 20.00 5.00 0.00

Batch size 25.00 25.00 25.00 25.00

Number of facilities 2.00 2.00 1.00 4.00

0.00

0.50

1.00

1.50

2.00

2.50

3.00

1 2 3 4

CODX-18D013-00

CODX-D260-00

CODX-12D025-00

COCD-16D177-00

Fig. 15 Cycle time (minutes)graph for high movingmodels (future state)


5.1 Summary of major or deeper changes that causedproductivity improvement in coil manufacturing

The productivity improvement in coil manufacturing resultedmainly from the reduction of setup time of the expanderthrough the application of LMS tools, which included VSM,SMED, and Kaizen (continuous improvement). Additionalbenefits were obtained through the reduction ofWIP inventoryand improved pant layout resulting in reduced shop floorcongestion and coil damages and improved workplace safety.

The major changes of the shop that contributed to theimprovements can be attributed to top management supportfor LMS philosophy, formation of LMS team, and provisionof necessary orientation and training in LMS.

6 Conclusions

In summary, the conclusions reached from this investigationare the following:

1. LMS was successfully applied to improve productivity ofairconditioning coil manufacturing.

2. The coil output per shift (of 8 h, 450 min work time,30 min personal time) improved from 121 to 214 coils orproductivity improvement of 76 %.

3. LMS tools such as SMED and Kaizen (continuousimprovement) were employed to reduce setup time ofthe expander machine from 60 to 20min, an improvementof 67 %.

4. VSM, an LMS tool, revealed that the value additionpercentage (%VA) of the coil shop was around 5 %.VSM (future state) projected the value additionpercentage to be around 12 % after the implementationof all the improvement projects, the increment of 140 %from the current level, which resulted from the setup timereduction of expander machine.

5. Several innovative Kaizens (continuous improvement)design change or improvements were proposed to reducethe setup time of the expander. The Kaizen designincluded rack (gear) and pinion (gear) mechanism forrow change, using rectangular spacer and scale on bothsides of the machine for the easy alignment of back plates,fixing the location of the door plate in door frame toeliminate the possibility of variation and need forreadjustment, designing receiver plate with spring, andcam and lever mechanism of locking system for easyinsertion of receivers in plate and one touch locking andconverting continuous groove in door plates to fixed holesfor accurate mounting of side stopper.

6. Additional benefits were accrued through a reduction ofWIP inventory and floor space utilization resulting inimproved plant layout. This in turn would reducecongestion and coil damage and enhance safety at theworkplace.

7. Several Kaizen target changes in work methods wereproposed that included providing scale at both sides ofexpander, keeping expander accessories on a movable

Model :Batch :

Supplier PPC

Pt 1.69 Pt 1.09 Pt 3.02 Pt 1.30 Pt 0.29 Pt 0.00 Pt 0.79 Pt 3.27MP 1.00 MP 1.00 MP 4.00 MP 2.00 MP 6.00 MP 2.00 MP 1.00 MP 2.00ST 10.00 ST 10.00 ST 5.00 ST 20.00 ST 10.00 ST 3.00 ST 0.00 ST 0.00WIP 1.00 WIP 1.00 WIP 5.00 WIP 5.00 WIP 5.00 WIP 1.00 WIP 1.00 WIP 1.00Shift 1.00 Shift 1.00 Shift 2.00 Shift 2.00 Shift 1.00 Shift 1.00 Shift 1.00 Shift 2.00

NVA 0.00 11.69 11.09 20.08 26.50 11.43 3.00 0.79 3.27

VA 0.00

CODX-18D013-00 (future state)25.00

VA=∑Pt NVA=∑((Pt*WIP)+ST) Percentage value addition (%VA) = (∑VA/(∑VA+∑NVA))*100

∑NVA=87.85

∑VA=11.44

% VA=11.52

1.69 1.09 3.02

Manual brazing

Water testing

Fin press HPB

1.30 0.29 0.00

Lacing ExpanderAuto

brazingCoil

bending

Customer

0.79 3.27

I I I II I I I I

Fig. 16 Value streammap (VSM)—future state (CODX-18013-00). PPC Production planning and control, Pt process time (min),MP Manpower (no.),ST setup time (min), WIP work-in-process inventory (no.), shift (no.)

Table 7 Productivity improvement obtained through the implementationof LMS

Parameter Currentstate

Futurestate

Improvement(%)

Setup time (min) 60.00 20.00 66.67

Batch size 25.00 25.00 Na

Process time/coil (min) 1.30 1.30 Na

Cycle time per coil (min) 3.70 2.10 43.24

Coil output per shift (450 min) 121.62 214.29 76.19


trolley, providing separate tool sets for operators andusing pneumatic tools instead of manual tools.

7 Future study

To extend the application of LMS at Blue Star Limited withparticular reference to airconditioning coil manufacturing,future study is in order:

1. Further analysis of process time can surface newpossibilities of improvement.

2. Operator training in skill development would improveefficiency and thus reduce operator setup and processingtime for the expander and other machines/processes usedin airconditioning coil manufacturing.

3. The leanmanufacturing concepts can be extended to othermanufacturing or production areas of the plant such asfabrication shop and paint shop. The results can also beshared with other plants. The capacity balancing can bedone after optimizing the percentage value addition ineach shop.

8 Concluding remarks

The lessons learned from this investigation can be appliedsuccessfully in similar companies. Before embarking onapplying LMS for manufacturing productivity improvement,top management support for LMS philosophy is absolutelyessential.

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