J Intell Manuf (2006) 17:715–724DOI 10.1007/s10845-006-0040-2

Achieving e-Manufacturing: multihead control and webtechnology for the implementation of a manufacturingexecution system

Arturo Molina · Armando Ramírez Santaella

Received: February 2005 / Accepted: January 2006© Springer Science+Business Media, LLC 2006

Abstract Intelligent Manufacturing Systems requiresadvanced and efficient manufacturing technologies,management and procedures in order to achieve valuecreation in global markets. E-Manufacturing is the setof information technologies that allows companies toachieve on demand manufacturing through the inte-gration of e-business applications. Cornerstone of thisconcept are Demand Flow Technology, ManufacturingExecution Systems (MES) and Digital OperationalMethod Sheets (OMS) which are vital to control shopfloor operations where there is a need to balance manualand automated operations. Specially, Mexican compa-nies face large diversity of products and multiple produc-tion lines, with high turnaround rotation of the workers.A low cost solution that integrates Demand Flow Tech-nology, MES with Digital OMS is described, the systemhas been developed using LINUX servers, Multi-headcontrol technology (multiple monitors to a single server)and a WEB based environment. This technological solu-tion offers an affordable, stable, and high performancesolution to transform the production into a more bal-anced system with shorter and faster cycles allowing acompany to achieve e-Manufacturing.

Keywords e-Manufacturing · Demand FlowTechnology · Manufacturing Execution Systems ·A. Molina (B)Engineering and Architecture Division, Tecnológico deCampus Monterrey, Av. Eugenio Garza Sada 2501,64849, Monterrey, Mexicoe-mail: armolina@itesm.mx

A. R. SantaellaSMES, Plaza Sta Maria 5616, Col Jardines del Paseo,Monterrey, Mexicoe-mail: aramirez@solutionmes.com

Web Technologies · System Integration · FlowManufacturing · Operational method sheets

Introduction

E-manufacturing is concerned with the use of thee-business applications in manufacturing industries. Itincludes all aspects of manufacturing—sales, marketing,customer service, new product development, manufac-turing and procurement, supplier relationships, logistics,and strategy development. The use of e-Manufacturingmake it possible for a company to achieve knowledge-based value creation and Manufacturing on demand.In manufacturing, the efficient and effective manage-ment, manipulation, and use of information are essentialto economic vitality and growth. A competitive battleis being played out against a backdrop of companiesseeking to leverage the Web for uses other than simplyposting information. It is being used to integrate the nec-essary data, information and knowledge to create valueto all the actors in a supply chain: customers, suppli-ers and the company itself. The integration of informa-tion at different levels of the factory through the use ofweb-based technology is essential to offer new informa-tion services to customers and suppliers to achieve onDemand Manufacturing (e-Manufacturing).

Shop floors are nowadays outfitted with web-basedtechnologies that come with pre-loaded links to websitesapproved by their company’s management: suppliers,customers, vendors, leading portals and informationsources. The development of web based applicationsis not a one-off project, but a journey that involvesdealing with strategies, business processes, organization,people and technologies. Success will come to those

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firms adopting an integrated approach driven by busi-ness needs and opportunities.

The concept of Manufacturing Execution System(MES) has acquired a huge importance in today’s mod-ern manufacturing, especially in industries where rapidresponse to customer demands is the driver of the pro-duction system. The implementation of MES in Make toOrder (MTO) industrial environments has beencommon, especially in Electronics and Semiconductorscompanies.

The characteristics of MTO environments, such as theneed for product customization, the necessity to applyfast changes to production lines based on orders to con-form last-minute customer’s changes make MES sys-tems a requirement for MTO operations (Choi & Kim,2002).

MES is a relatively new concept, introduced in the1990’s. According to MESA (acronym for Manufac-turing Enterprise Solutions Association; 1997), Manu-facturing Execution Systems deliver information thatenables the optimization of production activities fromorder launch to finished goods. Using current and accu-rate data, MES guides, initiates, responds to, and reportson plant activities as they occur. MES is a software-basedapplication that grew up in the realm of planners to helpschedule optimum production runs, manage inventory,handle regulatory databases and information, and othermanufacturing planning chores. MES has the followingtwo characteristics (Choi & Kim, 2000):

• It provides real time information about what is hap-pening in the shop floor, for managers (under a stra-tegic approach), and for direct operation workers(under a purely operative approach).

• It is an information bridge between Planning Sys-tems used in Strategic Production Management(such as ERP—Enterprise Resource Planning) andManufacturing Floor Control SCADA (SupervisoryControl and Data Acquisition). It links the Man-ufacturing Information System’s layers (StrategicPlanning and Direct Execution) through the ade-quate on—line managing and control of updatedinformation related with the basic enterpriseresources: people, inventory and equipment.

The enormous importance acquired by MES resides,in a significant percentage, on its functionalities (imply-ing people, inventory and equipment) and their inter-action with the compounding elements of the industrialplant environment. Authors and organizations, such asMcClellan (2000) and MESA have given full anddetailed descriptions of these functionalities, indepen-dently of the industrial application branch of MES.

Authors like Kaufmann (1997) and Schenker and Cilia(2001) have emphasized some special functionalities andtechnologies that are aligned specifically to Semiconduc-tor Industry and general Small and Medium Enterprises(SMEs) use. Fukuda (1999) and Cheng, Wu, and Chang(2001) have developed important MES-next-generationarchitecture models. MESA has proposed hierarchiesdistinctions for MES functionalities. This hierarchy isdivided in two stacks: Core Functions and Support Func-tions. Core Functions include Planning System Inter-face, Data Collection, Exception Management, WorkOrders, Work Stations, Inventory/Materials and Mate-rial Movement. On the other hand, MES Support Func-tions are listed as Genealogy, Maintenance, Time andAttendance, Statistical Process Control, Quality Assur-ance, Process Data and Documentation Management.

Some important trends have been forecasted for MESimmediate, mid- and long term future (MESA Interna-tional, 2000). In the opinion of the authors the mostimportant are (Gaxiola, Ramirez, Jimenez, & Molina,2003):

• MES will become the engine behind inter and intramanufacturing enterprise collaboration as it is theenabling link for high velocity supply chain perfor-mance.

• Due to Food and Drug Administration (FDA) reg-ulations for current Good Manufacturing Practices(cGMP) and electronic signatures (21 CFR Part 11)MES will become standard in Med-Service and Bio-tech industries.

• MES will raise the average acceptable plant effi-ciency benchmark from 60% to 70% to over 90%within 3 years.

This paper describes the implementation of a MESbased on multihead control and web technology to havedigital Operational Method Sheets for controlling shopfloor operations in order to achieve the concept ofe-Manufacturing.

The company context and problem

The company was conceived on April 1998 to be themost advance manufacture site for building lighting fix-tures and HID Ballast to supply American market. Thefirst production run was on September of 1999 with avery aggressive ramp-up. The products to be manufac-tured in the facility are shown in Fig. 1.

The plant was designed using Demand Flow Tech-nology (DFT), to achieve flexibility in terms of volume-changes, product range and production cycles. The

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Owl

SBW

Productos que ya se fabricaban en Mexicopara GE

201SA337 SKU’s

Solaris142 SKU’s

M2503434

Power Bracket743 SKU’s

M4001615 SKU’s

3434 SKU’s

Productos

Fig. 1 Product Mix to be manufacture at the Mexican Facility(SKU—Stock Keeping Unit Stock Keeping Unit. A common termfor a unique numeric identifier, used most commonly in onlinebusiness to refer to a specific product in inventory or in catalogue)

company already had implemented with success DFTenvironment in other facilities, and the use of this pro-duction method was encouraged. The production plantcharacteristics were:

• 8 production lines.• 18 operations in average per production line.• Average of 2000 different SKU (Stock Keeping

Unit) per production line.• Change in models every 10 min per production line.• Takt-time of 30–45 seconds.

The conditions of the operation of the plant requiredto implement Operational Methods Sheets (OMS) totackle the flexibility challenge, due to the number ofproduction lines, number of operations on each line,size of Bill of Materials (BOM) and the complexity ofthe product structure. The OMS required to be designedaccordingly to the workers skills due to its limited train-ing and multiple assembly skills.

The factory started with OMS printed on paper. How-ever the use of printed OMS became a problem due tothe fact that the number of SKU finish products was verylarge and product models changed daily. Productivitywas not accomplished because product model changerate was 1 every 10 min, even though the setup in the

production line, was fast, the problem was to deliverOMS to the workers.

The management of OMS on paper was ineffective.There was too many OMS around the production linesand updating the BOM and operators instructionsbecame unmanageable. A change in an order in the pro-duction lines required 30 min to set up the OMS becausethe production leader required performing the follow-ing activities:

1. Order the OMS in sequential order.2. Find the OMS in the engineering files.3. Review the OMS with the materials and production

department to ensure that it was possible to producea particular product.

4. Deliver OMS to all the working stations.5. Collect previous OMS and ensure that there were no

missing OMS.

It was obvious that an Information Technology solu-tion was needed. But there was a restriction of cost,because the company startup was already with low cashflow. Therefore an internal IT development project wasconceived in order to implement the concept of DemandFlow Technology based on Information technology sup-ported by a Web based MES and Digital OMS.

Designing a demand flow technology basedon information technology

The DFT (Demand Flow Technology) methodology wasused to design and implement the shop floor control sys-tem. In order to better use the concept of DFT it wasnecessary to analyze the following aspects of the man-ufacturing system: Mix Production, Material Flow andFacility Layout, and Information flows in the Shop Floorfor decision making

Mix production—classification of products

An analysis of the products was undertaken to betterunderstand mix production problem. The products wereclassified in three types:— MTS (Make to Stock), ATO(Assemble to Order) and BTO (Build to Order)—basedon the sales cycle: MTS (27 weeks), ATO (15 weeks) andBTO (10 weeks). Therefore it was decided that productsclassified as MTS will have a production cycle of 4 daysfrom order received to delivery, ATO from 4 to 7 days,and BTO of 21 days. All the products were FOB (Freeon Board) at the plant and it was decided not to produceunless there was a production order from the customer.The idea was to avoid the production of products for

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Fig. 2 Description ofproduct mix and components:MTS (Stock), ATO (Ass toOrder), BTO (Custom)

…And Meet Customer Delivery Need!…And Meet Customer Delivery Need!

Custom

Stock

ATO Stock

ATO Custom

2300 Part Numbers Part Volume

… IdentifyFlow Parts...

… IdentifyFlow Parts...

Custom

Custom

Stock

ATO

ATO

6300 Catalog Numbers Unit Volume

Stock … React FastOn A SubsetOf SKU’s...

… React FastOn A SubsetOf SKU’s...

Stock Assm To Order Custom

OTS 4 Days OTS <21 DaysSupplier Lead Time

OTS 4-7 Days

Classify SKU’sBy OTS Need...

Classify SKU’sBy OTS Need...

stock. There was also a classification of raw material inorder to decide which products parts will be on the racksof the production lines. For MTS products the decisionwas always to maintain raw material up to a maximumof 2 days. Therefore for ATO products there was alwaysone component that will not be available in the produc-tion line, but it has stock in the principal warehouse.However for BTO products there was always be onecomponent that the plant does not have in inventoryand has to be purchased on demand. Figure 2 summa-rizes the information regarding the mix product of theplant.

Material flow and the facility layout

The material flow is very important in the implementa-tion of DFT; it is a change in the culture of how materialis managed. One of the biggest problems was the ware-house, which was open, no walls, no doors, and all thesignals to supply raw material were the empty Kanban,or the Kanban cards. The material department had todevelop certain systems in order to follow the meth-odology as specified in the DFT method. The facilitylayout was redesigned in order to have a new materialflow based on the product characterization and the newshop control system being implemented based on Kan-ban philosophy. The Fig. 3 describes the design of theplant and the flow of material.

Information flow for shop floor control

The complexity of the Shop Floor operations requiredto have access to different types of information: inven-tory levels, operational methods sheets (OMS), statusof working orders, manufacturing plans, and schedul-ing. An ERP man-pro system was already generatingthe working orders for the shop floor and materialsand components purchases. However the productionlines were not able to respond to the manufacturingplans imposed by the ERP programme. The reason wasa lack of synchronization between the products beingproduced, stocks consumption in the production linesand working orders being manufactured. Therefore anIT (Information Technology) solution was designed inorder to build up a system that could implement anintegrated solution which included ERP, MES and ShopFloor control using Digital OMS.

Technological solution to implement e-Manufacturingsolution based on ERP, MES and digital OMS

The production system was designed and developed bythe IT department working together with an engineer-ing team to design the MES system and to developthe customization and plug-ins to the ERP system. TheMES development included all the basic functionalitydefined by MESA (1997). The biggest challenge was the

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Fig. 3 Plant Layout andFlow of Material

OVStores

Shipping

BallastArea

Receiving

EcoatPaint

Reflector FormAnd Finish

OV MaterialKanBans

Assembly Lines

ReflectorKanBans

DieCast Hsg.KanBans

BallastKanBans

Lams, Wire, Bobbins, Insulation Reflector BlanksDie Cast Housings

All OtherComponentParts

Simple … Visual … Pull Through … Flexible …Fast … Applied DFT Concepts!

Simple … Visual … Pull Through … Flexible …Fast … Applied DFT Concepts!

development of the Manufacturing Information Modeland Digital OMS system. Both concepts were designedand implemented by a group integrated with 2 manufac-turing engineers, 2 software engineers and different ITsuppliers trying to find the best solution. The objectiveswere to have an:

• OMS with high resolution (computer monitors).• Linked to the Bill of Materials and have online

changes and updates.• Easy to read, and to follow.• Synchronized with the flow of material and produc-

tion.• Easy to manage and maintain.• Low cost solution.• User friendly interface.

A manufacturing information model to supporte-Manufacturing applications

Nowadays, manufacturing enterprises in general haveadopted five or four functional levels to realize theirfunction. A de-facto standard has already emerged, bythe petition of various standardization bodies such asISO and NIST (National Institute of Standards andTechnology), together with various European projectswithin ESPRIT, and ending with the ANSI/ISA 95—ISO/IEC 62264 standards. This de-facto standard has 4levels (Level 4—Business Planning & Logistics, Level3—Manufacturing Operations & Control, Level 2,1,0—Batch, Continuous and Discrete Control). The MES sys-tem developed in this project uses a four level modelalign to the ISA 95 standard: Facility (Factory), Shop(Area), Cell, and Work station/Equipment (Molina &Bell, 1999). These levels of abstraction provide

manufacturing information objects for all functionalhierarchical activities within a manufacturing enterprise.A key element of the MES solution is the applicationnamed Manufacturing Information Model. A Manufac-turing information model is defined as an informationmodel that identifies, represents and captures the data,information and knowledge describing the manufactur-ing resources, processes and strategies of a particularenterprise. This enables the provision of the necessarymanufacturing information for the support of manufac-turing decision-making in the e-Manufacturing solutionproposed (Molina & Bell, 2002). The ManufacturingModel must represent the manufacturing capability andcapacity of a facility. In order to facilitate this task amanufacturing information modelling methodology hasbeen created in the form of an object-oriented multi-dimensional representation using semantic nets (Fig. 4).This multi-dimensional representation contains all theelements that are necessary to adequately describe man-ufacturing facilities. The Manufacturing InformationModel is composed of (Molina, Ellis, Young, & Bell,1995):

1. The modelling dimensions: data, function and behav-iour. Different aspects of the manufacturingresources, processes and strategies and their rele-vant characteristics have to be described in order tosupport strategic and operational decisions. Theseaspects are called in this methodology modellingdimensions and allow the representation of: data(class, composition and attributes), function(functional capabilities), and behaviour (status andperformance).

2. The manufacturing information entities: resources,processes and strategies. The manufacturing resour-

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Fig. 4 ManufacturingInformation Model todescribe Work Station forassembly operations

Shop

Cell

FactoryData

Behaviour

ResourcesProcessesStrategies

Station

Function

OperacionalStrategy

AssemblyCenter Tool Kit

process Tools

Available

perfor-measures

perf uses

uses

holds

has

XZ

Setup TimeAssembly Cycle

Scrap %

state

Active

status

Rules

OperationalStrategy

con-trols

has

Use only ToolsNo. 50

Resources, Process andStrategies Capacities

ces and processes describe generic capability infor-mation. Similar types of manufacturing resourcesand processes can be used by different companies.In fact, two companies can have the same type oftechnology, i.e., manufacturing resources and pro-cesses. Nevertheless, the manufacturing facility ofeach of these companies could perform in a differentway because of the company’s decisions on how toorganise and use those resources and processes. Thisaspect must be captured in order to truly representthe manufacturing capability of a company. The man-ufacturing strategies represent this company specificinformation which allows a company to specify howthe resources and processes are organised and usedin order to support the company’s manufacturingfunction.

3. The organization of these manufacturing informa-tion entities into a multi-level structure: Factory,Shop, Cell and Station. This hierarchical organisa-tion will enable the Manufacturing Model to pro-vide the adequate manufacturing information to thedifferent application environments i.e., Design forManufacture, Manufacturing Information Genera-tion, and Production Planning and Control. At thefactory level information defines what the company’smanufacturing strategy is, and at the three lower lev-els, i.e., Shop, Cell and Station, operational informa-tion describes how the manufacturing strategy hasbeen realized. The Factory level is aimed to representthe strategic information required for the formula-tion of the manufacturing strategy. The remainderthree levels represent the operational information

of the manufacturing facility to support product’slife cycle activities (e.g., design and manufacture).

Digital operational methods sheets (OMS)

The Digital OMS were the most difficult to designbecause a suitable technological solution was difficultto find. The major issues to tackle were costs, flexibilityand connectivity to the existing ERP. In order to finda suitable low cost solution, the team started to searchtools with open source solutions, and the final resolu-tion was to use LINUX as a server driving or handlingthe monitors. The team also was satisfied with the deci-sion because LINUX code was available for any changethat the development needed. So the first configurationstarted when the team decided to have OMS in a webbrowser, having the flexibility of interconnections, thepossibility of use XML, and the potential of use any cli-ent, cheap and thin client. Based on that assumption,the team designed a solution described in Fig. 5.

This first design was implemented with the mostimportant flavors of Linux, but still the solution wasunstable. After 5 months of research, the designchanged. The previous design was unstable cause it wasvery heavy solution or needed a big LINUX server tomanage all the Netscape sessions, so the team decidedto have 1 Linux server with 5 video cards running 5Netscape’s session with in that every Linux Server, asdescribed in Fig. 6.

The Digital OMS includes the incorporation of theinstructions for the assembly process, Bill of Materi-als, examples of assemblies, and Total Quality Control

J Intell Manuf (2006) 17:715–724 721

LINUX SERVER

Running Netscapesesion per monitor

Web Server

LINUX CLIENT

Boot and load LINUX Kernelwith NIC.

Start Xclient.

Execute Netscape sesionfrom server

Use Multihead Technology toconnect more than 1 monitor to a single CPU (Linux base)

Fig. 5 First design of the system implementation

Web Server

LINUX Servers

XFree86 running locally.

Execute Netscape sesion per Display

ERP sends individual commands to loadspecific URL (specific OMS)

Fig. 6 Second design of the system implementation – one linuxserver with mutlhead technology controlling 5 monitors

information (see Fig. 7). All this information is format-ted in one web page so it can be read by the operatorwith one look to the digital screen.

Digital dashboard for planning and controlling

An important feature of the MES is the implementationof a Digital Dashboard for Planning and Controlling toallow the shop floor supervisor to keep a tight super-vision on the operations happening in the productionlines.

The dashboard shows continuously the workingorders, productivity, breakdowns, takt-time, and cus-tomer request date. This information allows the supervi-sor to make decisions regarding planning and schedulingof customer orders (Fig. 8).

Results and benefits

Solution costs

The final e-Manufacturing configuration was tested andproved. Red Hat was the Linux that the team decidedas the most stable and reliability. The cost of the solu-tion was very reasonable, considering that the hardwarewas very low cost. One of the reasons to use Linux isthat it works very well even when it is installed in lowprofile computers, a PC with 2 Mbytes of RAM can loadthe Linux Kernel. So the servers of the final configura-tion were the lowest new computers on the market. Atthat point Celeron 400 Mhz were the lowest speed, and32 Mbytes of RAM, and HDD at least of 2 Gigabytes.The total investment including hardware, software and

Fig. 7 Example of a digitalOperational Method Sheet(OMS) using themanufacturing informationmodel

Bill of Materials

AssemblyInstructions

Information regarding Assembly operation

Indicator of Type of Instruction

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Fig. 8 Digital dashboard forplanning and controlling

Fig. 9 e-Manufacturingusing multihead technologyand web based MES ERP

Database

WEB server

Man-PRO

User

LOCAL NETTCP/IP

OMS Database

LYNUX Server PHP Protocol

Apache

Monitor

Monitor

Monitor

Monitor

Monitor

development was $ 62,200 USD. The total final solutionis presented in Fig. 9, where the web based MES systemwith the multi-head technology is running in a Linuxserver for each 5 monitors. The total system required10 monitors therefore 2 Lynux servers were used. TheMES is connected to the ERP Man-Pro system whichmanages the ERP and OMS databases using RemoteProcedure Calls.

Benefits

The real benefit of the solution was the digitization ofthe process, making a real system linked to the plantschedule, connecting all the department that have pro-duction as a client, speeding the model change, to almostseamless, and savings in paper, and time avoiding unnec-essary managements. Quality got better, all the companywas synchronized.

All these benefits helped to achieve the next resultswithin the first year:

• Productivity 100 K/60 K= +67%.• Increase Throughput to clients.• Inventory Accuracy 40% → 95%.• Backlog Past Due 88 K Units → 5 K Units.• Receive Customer Centricity Award from GE.• Reduction of the SPAN metric 68 → 36.• Reduction Suppliers Lead-time.• Reduction Scrap 8% → 2%.

All the departments were working as a synchronizedclock, because the schedule was the kernel of the solu-tion. The schedule was updated from the supervisors onthe assembly line, and the ERP system was in charge ofupdating the Digital OMS for every single monitor. Themanagement of the BOM was a user friendly system,and was managed by part time students, whom weretraining to operate the system in 10 min.

This concept was implemented in the ballast area, togive instructions to the operator of bobbin machines.This implementation was done in 2 weeks, and the ben-efits were outstanding. After 2 years of operation, the

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Fig. 10 Example of the production line with Digital OMS

average production was 1,400 Ballast per day. Afterimplementing the monitors for the bobbin machines,the average production increased to 800 ballast per day.

Experiencies and lessons learned

The following is a recollection of key success factors ofthe project:

• The champion and leader of the project should beProduction Engineering and not the department ofInformation Systems.

• The implementation of best manufacturing practicessuch as DFT (Demand Flow Technology), Kanbanand OMS (Operational Methods Sheets) facilitatesthe implementation of a successful MES.

• The layout of the production lines must redesignergonomically to accommodate the monitors foreasy visualization and security of the operator.

• The operation of the MES using Digital OMS andWeb technology requires continuous maintenanceof the monitors and CPUs, therefore to keep a stockfor replacement ensures 24/7 operations.

• The production plan and control must be followedaccordingly to the MES system, it is important tocontinuously synchronize materials inventory (phys-ically vs. logical) and supply/consumption to ensuretakt-times in production lines.

Conclusions

A low cost e-Manufacturing solution for balancedautomation systems (man/machine) has been presentedbased on multihead control and web technology. Web

based technology using open source allows to implementsoftware solutions that are reconfigurable, modular andextensible. The concept of using Linux as a web moni-tors server is a solution very stable and with unlimitedapplication on the shop floor, providing information inHTML format (Text, Graphic, Audio, Video) transmit-ting to the operators information about their work theyhave on performance, or quality related information,new, access to the intranet and performance indicators.The purpose of having Digital OMS on line and syn-chronized with the plant schedule, with a very effectivesolution was accomplished. Digital OMS have a greatcapability and flexibility of dispatching information tothe shop.

It is very important the control on the shop floor,in order to have all the process synchronized, that isimplementations need a lot of discipline, workers needto follow procedures, punching info in the system, tohave al this working.

The concept is very transferable, and right now it isimplemented in another production plants with a diver-sity of processes, like the production line of glass man-ufacturers and automotive Harnesses. In all these cases,digitized information is being distributed to the work-ers in the shop floor to make sure the process is carriedout accordingly with the production plan and qualityconditions.

Acknowledgements The research reported in this paper is partof a Research Chair in Mechatronics of ITESM. The authors wishto acknowledge the support of this grant in the preparation of themanuscript.

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