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DesignprocessimprovementthroughtheDMAICSigmaapproach:awoodconsumptioncasestudyARTICLEinINTERNATIONALJOURNALOFPRODUCTIVITYANDQUALITYMANAGEMENTJANUARY2011DOI:10.1504/IJPQM.2011.038687

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Int. J. Productivity and Quality Management, Vol. 7, No. 2, 2011 229

Copyright 2011 Inderscience Enterprises Ltd.

Design process improvement through the DMAIC Sigma approach: a wood consumption case study

Tarek Sadraoui* Dynamic Economic Unit and Environmental Research, Higher Institute of Industrial Management of Sfax, University of Economics and Management Sfax, Sfax, Tunisia E-mail: [email protected] E-mail: [email protected] E-mail: [email protected] *Corresponding author

Ahmed Ghorbel Higher Institute of Industrial Management of Sfax, University of Economics and Management Sfax, Laboratory BESTMOD, Higher Institute of Management, University of Tunis, 41, Freedom Street, Bardo 2000, Tunis, Tunisia Fax: +216 74 891 192 E-mail: [email protected]

Abstract: Six Sigma is a well-known concept which means the perfection. A process of production to three sigma makes 3.4 defaults/million unit, whereas six sigma means for us the perfection. We used it now to mean type of specialised training, aiming at the attack of very high objectives for processes improvement. Six Sigma is a method of continuous improvement and elimination of non-quality, passing by cycle DMAIC: to define, measure, analyse, innovate and control carried out by a team of project. In this paper, we propose a new practice of Six Sigma for reduction of the number of conformities and minimisation of the number of customers Complaints for KITAMEUBLE industry.

Keywords: Six Sigma; DMAIC; define, measure, analyse, improve/implement and control; control charts; Pareto; wood consumption; KITAMEUBLE.

Reference to this paper should be made as follows: Sadraoui, T. and Ghorbel, A. (2011) Design process improvement through the DMAIC Sigma approach: a wood consumption case study, Int. J. Productivity and Quality Management, Vol. 7, No. 2, pp.229262.

Biographical notes: Tarek Sadraoui has PhD in Quantitative Methods. He is a Member and Researcher at the Unit of Dynamic Economics and Environmental Research. The research activities deal with studying international R&D transmission mechanism and relation between R&D cooperation and growth, dynamic panel data model and testing unit root, cointegration and causality in

230 T. Sadraoui and A. Ghorbel

many issues using WinRats, Eviews TSP and STATA Software. He is an Associate Professor at the High Institute of Industrial Management of Sfax in Tunisia. He is teaching Econometric Analysis, Statistics and Statistical Process Control.

Ahmed Ghorbel has PhD in Quantitative Methods. He is a Member and Researcher at the Business, Economic Statistics Modeling Laboratory. The research activities deal with studying international transmission mechanism between financial markets, forecasting and modelling of volatility and correlation for financial risk management. Using S-Plus and other Software Eviews, STATA, SPSS, he is developing Copula Models. He is an Associate Professor at the High Institute of Industrial Management of Sfax in Tunisia. He is teaching Econometric Analysis, Statistics and Statistical Process Control.

1 Introduction

This study proposes to define, measure, analyse, innovate and control (DMAIC). Six Sigma methodology (Breyfogle, 1999) is used to improve the design process in the KITAMEUBLE industry (Linderman et al., 2003). We are interested in this project of end of study in the approach six sigma which allows a global solution of the improvement of the quality of the product by the use of the product by the use of the whole of the tools of quality. But also by a management by project and which will conclude this review from the methods and tools of quality.

The objective of our study is to help the persons in charge for the service of quality management to reduce the cost of non-conformity and the number of complaint with the installation of a step six sigma.

According to Klefsjo et al. (2001), Six Sigma is a broadly accepted methodology that focuses on improving an organisations operational performance, business practices and systems by identifying and preventing defects in manufacturing and service-related processes.

According to Wright and Basu (2008), Six Sigma is a holistic approach to achieving near perfection, expressed in terms of no more than 3.4 errors per million opportunities. This near perfection appears to many to be overkill, or to some an impossible ideal. Nonetheless, Six Sigma has been adopted by many leading companies. The benefits are well-documented for manufacturing industries, and increasingly in service industries. For Azzabi et al. (2009), Six Sigma has been characterised as the latest management fad to repackage old quality management principles, practices and tools/techniques. At first glance, Six Sigma looks strikingly similar to prior quality management approaches. However, leading organisations with a track record in quality have adopted Six Sigma and claimed that it has transformed their organisation.

A careful study on Six Sigma indicates that its success in organisations depends on the intensive and rapid exchange of knowledge among the stakeholders to reduce the defects and also effective usage of efficient statistical process control and scientific tools. Moreover, if the organisation is too large, it is very difficult to facilitate the meeting of Six Sigma members to exchange and pool knowledge. Conversely, if the organisation is small, adequate expertise may be lacking to practice the Six Sigma technique (Kaushik et al., 2008). Furthermore, in the modern work environment, people are finding less time

Design process improvement through the DMAIC Sigma approach 231

to meet, discuss and function as a team. It is proposed here that these deficiencies can be overcome by integrating Six Sigma with it. This is because it is very efficient in exchanging data, information and knowledge within and outside the boundaries of the organisation (Andersen, 2001; Hedelin and Allwood, 2002) and also because it can facilitate teamwork (Dewhurst et al., 1999).

This paper is organised into four sections to tackle these objectives. In Section 2, a literature review of Six Sigma, quality sustainability and the possible link is provided. In Section 3, a background description of the case study organisation with a provision for the methodology is presented. Section 4 draws conclusions on the design DMAIC model.

2 Review of Six Sigma

Six Sigma is a philosophy of quality turned towards the customer satisfaction. First of all, one includes/understands well that a greater customers satisfaction will at the same time allow all to preserve our customers and to conquer the new ones. This increase in the losses of market will be concretised by an improvement of profitability. Six Sigma can reduce variability which is the enemy of quality (Sahoo et al., 2008). When an engineer has just manufactured a product which gives whole satisfaction, its dream would be of being able to identical so that each product preserves same qualities (Chourides et al., 2003; Coronado and Antony, 2002). However, there will be always a small respect entre the products considered identical, and these are the small respect which lead to non-quality (Sadraoui et al., 2010) (for more details see Figure 1).

Figure 1 Customer satisfaction


The Six Sigma concept has enjoyed success throughout the business world over the last 20 years, contributing significantly to renowned corporations improving their net income (Manikandan et al., 2008). For a number of years now, this successful concept has been supplemented by the tools of lean management, an approach that has accelerated process speed, reduced inventories and decreased lead times. As practiced by the authors of this book, the Six Sigma and lean approach combines the tried and tested tools of both worlds, which are linked together systematically in the proven DMAIC process model (John et al., 2010).

Historically, Six Sigma is a direct descendant of Deming and Jurans systems for quality improvement. As in biological evolution, Six Sigma represents the survival of the fittest in terms of the methods and approaches (see Natarajan and Morse, 2009). It relies on a highly developed management system for its deployment. The improvements are carried out through carefully managed improvement projects. The project selection is typically based on a translation of the company strategy into operational goals (Antony, 2004). The project teams are deployed to solve problems of strategic importance. Six Sigma provides an organisational structure of project leaders and project owners (Hamza, 2008).

The success of the Six Sigma concept in business has motivated many European companies, such as Volvo, Nokia and Siemens to adopt and implement it (Pfeifer et al., 2004). Six Sigma is a disciplined process which helps companies to focus on developing and delivering nearly defect-free products and services (Sleeper, 2009). It is an organised and systematic business performance improvement strategy that relies on statistical and scientific methods to reduce waste and the number of defects within the Six Sigma level (Antony, 2002; Banuelas and Antony, 2003; Linderman et al., 2003). A Six Sigma level is the benchmark factor for the ability of the process to fulfil the requirement. Table 1 illustrates how sigma levels would equate to defect rates and organisational performances, which are often measured in terms of defect per million opportunities (DPMO) (Park, 2002). DPMO is the number of defective opportunities that do not meet the specification limits out of one million opportunities. Table 1 Sigma level

Sigma level

Process mean fixed Process mean with 1.5 shift

Non-defect rate (%) DPMO Non-defect rate (%) DPMO

1 86.26894 317.311 30.2328 697.672 2 95.44998 45.500 69.1230 308.770 3 99.73002 2.700 93.3189 66.811 4 99.99366 63.4 99.3790 6.210 5 99.9999943 0.57 99.97674 233 6 99.9999998 0.002 99.99966 3.4


The application of Six Sigma has the ability to reduce the variation of the characteristics of the product or service from the target by using either continuous improvement or a design/redesign approach (Yang et al., 2008). The first approach follows the phases: define, measure, analyse, improve and control. This approach is known as DMAIC methodology. The second approach progresses through the phases: define measure, analyses, design and verify. This is known as the DMADV methodology (Banuelas and Antony, 2003). DMAIC is used for improving an existing process, whereas DMADV is employed for the design of products (Banuelas and Antony, 2003; Snee, 2004). For designing the framework of the WSS model, the DMAIC methodology is chosen. The conventional DMAIC concept is explained in a few words below.

Define phase

Through this phase, Six Sigma project is drafted and the process to be improved is identified. After identifying the process by using suitable techniques, the process is documented. One such technique that is often used is the flow-charting technique. Finally, the customers requirements are identified, analysed and prioritised. This phase can be presented as below.

Measure phase

During this phase, data are collected to evaluate the level performance of the process and provide information for the subsequent phases. The Six Sigma team decides the characteristics to be measured, the person doing the measurement, the measuring instruments, target performance and sampling frequency. Finally, the process capability is calculated. This measure phase can be resumed as below.

Analyse phase

In this phase, Six Sigma team analyses the data collected to find the key variables which cause process variation, and discovers the causes for defects. Alternative ways of improving the process are also evaluated during this phase. The various tools used in this phase are root cause analysis, cause and effect diagram, Pareto charts, failure mode and effects analysis and design of experiments. We can represent this phase by diagram below.


Improve phase

Here, the Six Sigma team modifies the process to stay within the maximum permissible range of the performance of the key variables. The process performance has to be monitored and measured. If it is satisfactory, it can be institutionalised. Solutions for process improvement are obtained through process simplification, parallel processing and bottleneck elimination. To improve is a very important phase which can be presented as it is indicated in diagram.

Control phase

This phase has the purpose to sustain the improvements established through the previous phases. By using control charts, the critical variables related to the performance are controlled in order to keep an eye on the process performance after improvement. It can be represented as below.

The benefits of Six Sigma in business organisations are: defect reduction, cycle time reduction, manufacturing cost reduction, market share growth, productivity improvement, product/service development, customer retention and culture change (McAdam and Evans, 2004; Syed, 2008). These benefits can be achieved through the successful implementation of Six Sigma. The successful implementation depends upon the training given to individuals of the organisation in the fundamental concepts and tools involved in the application of Six Sigma. The levels of training given to individuals in organisations during the execution of Six Sigma projects are categorised into green belt, black belt and master black belt (Ingle and Roe, 2001).

2.1 What is Six Sigma?

Mathematically, Six Sigma represents six standard deviations (plus or minus) from the arithmetic mean. As a measurement of quality Six Sigma means the setting of a performance level that equates to no more than 3.4 defects per one million opportunities. Six Sigma is an approach that takes a whole system approach to improvement of quality and customer service so as to benefit the bottom line. The Six Sigma concept matured during the mid-1980s and grew out of various quality initiatives at Motorola. Like most quality initiatives, Six Sigma requires a total culture throughout an organisation whereby everyone at all levels has a passion for continuous improvement with the ultimate aim of achieving virtual perfection. To know if Six Sigma has been achieved needs a common language throughout the organisation (at all levels and within each function) and common uniform measurement techniques of quality. The overall Six Sigma philosophy has a goal of total customer satisfaction.


The approach 6 Sigma is a methodology initiated quality there is a score of year at the great groups which wished to appreciably improve quality of their products and tend to excellence by putting the customer at the centre of their concerns. Six Sigma is a methodology of improvement quality based on processes which makes it possible to follow measure and increase the company performance. While being based on the statistical tools to measure the performance of the processes trades, Six Sigma makes it possible to eliminate the wasting, to reduce the cycle times and to reach results which tend towards the perfection. The improvement of the processes, made possible by Six Sigma, results in a better customer satisfaction, a stronger implication of the teams and increased profits. And since Six Sigma is not a step like the others, it does not count six, but seven advantages on other methodologies of improvement of the performance. Methodology Six Sigma is used more and more because of the success which it made possible to characterise not only on the level of the improvement of customer quality, but also while making it possible to reduce the costs in a significant way; thanks to these improvements, Six Sigma is applicable to all types of activities.

Six Sigma is a method of management, of particularly effective progress. Exit of a strongly connoted step quality is relatively simple in the field of the principle. To satisfy the customers, it is necessary to deliver products of quality. The innovation lies rather in the fact that it brings a new philosophy of management to the level of the company. It is clear that the tools which Six Sigma brings are not new at all. Six Sigma makes it possible to set up a durable approach to cure it. This philosophy aims at setting up a culture of directed company customer, and who bases himself on concrete facts and data for the decision-making.

A company whose performance is measured to Six Sigma (the reference of the market) generates only 3, 4 defects per million opportunities (almost perfection), Whereas a company with 3 sigma, i.e. the current standard, must support the cost of 66,800 defects per million of opportunities:

implication and engagement of the persons in charge alignment of projects with the strategic objectives defects identified by customer the objective is to repeat the defects and the variation rigorous respect of the method stages method structured for the profits decision-making based on data.

2.2 Benefit and advantages of Six Sigma

Six Sigma is a methodology which helps to:

increase the performance of the company by the improvement of the quality of its processes

prepare your collaborators with advantage of efficiency by eliminating the defects get tools to reduce the costs


provides methods tested to measure precisely and increases the return on investment allows undervaluing the financial risks Six Sigma is an indicator of performance which describes the aptitude of a produced

process or service or waiting customer

indicate your performance to customer specifications the measure of defects as an indicator which facilitates the comparison of performance between product,

service and process

to imply all the personnel in real activities with the strategic objectives develop the statistical analysis of the data improve comprehension, the control and the performance of the key processes.

2.3 Why Six Sigma?

All the processes, whatever is their degree of accuracy, are always unable to exactly produce the same product. There will always be a small variation between the products considered identical and these are the variabilities which lead to non-quality. Whatever the studied machine and the characteristic observed, one always notes dispersion in the distribution of the characteristic. These variations come from the whole of the process of production. The analysis of these processes makes it possible to dissociate five element source of this dispersion; one generally indicates them by the 5M.

Then the goal of Six Sigma is to improve quickly, continuously and significantly the processes by eliminating these variabilities. This methodology is used to improve the processes, the products and the services to reduce the costs of all kinds and to improve quality. The objective is simple: to satisfy the customer by having processes without defect with advanced tools of progress and to reduce variability.

Moreover, Six Sigma is a change of positive and major culture with real financial results. To have a process, Six Sigma means that the difference between the limit of low specification and the limit of high specification of the customer can contain six times the standard deviation (or Sigma) of the production curve of the process. Thus the variations of a characteristic generally follow a bell-shaped curve: law of Gauss or normal law (central limit theorem). If the average of the production is centred on the target, it is thus natural to find values lain between 3 standard deviations, if values leave these limits, one has a strong probability that the process is not centred any more on the target. It is then necessary to identify the causes of variability in order to centre the process. All the processes have variability, which have very few causes, (20% causes = 80% of the effects). If one knows these causes one should be able to control them, then, the designs must give robust processes to the remaining variations that is true for the processes, the products, the transfers and the services.


3 A KITAMEUBLE Six Sigma case study

3.1 The background of the company

Since its creation in 1986, company KITAMEUBLE does not dare of this developed to become leader in the market of manufacture of the pieces of furniture. It developed to offer a broad range of services in the transformation of wood, and thus to become a reference in Tunisia. For this, since the year 2007, the company started a programme of levelling to adhere to the management system of quality the management system of quality (SMQ), which results certification from the SMQ during the year 2008 by the standard ISO 9001 version 2000.

During the year 2009, KITAMEUBLE carried out system programmes for the endorsement of forest certification schemes or programmes of reconnaissance of forest certifications (PEFC). This system has be created by owner foresters of six European countries (Germany, Austria, Ireland, France, Norway and Sweden), the purpose of which is to guarantee that the certified forests are managed durably, i.e. according to managements suitability to satisfy the economic, ecological and social needs for our companies, for present and for the future.

PEFC leads to a certification of the products containing wood of these forests whose origin is attested by logo PEFC. Within this framework, the direction begins:

to promote the products coming from the forests, respecting the principles of durable management

to ensure the staff training implied in the control line to make apply the present procedure to ensure conformity the requirements of PEFC to accept controls on site or documentary envisaged within the framework of this

certification

to carry out reviews of the system. KITAMEUBLE includes four manufacturing units and one storage unit. A description of the phases of manufacture can be indicated in Figure 2.

The SMQ of KITAMEUBLE aims as follows:

to fix the rules of the company operation in order to ensure its development as well as to possibly integrate a constant research of quality improvement of products and services

to increase and improve satisfaction as of the customers by the attack of the laid down objectives quality

to make a continuous improvement of quality by skew of the training of its personnel to illustrate with the customers the setting of a SMQ conforms to the standard ISO

9001 version 2000 in their proposer, the handbook quality of KITAMEUBLE.

3.2 The working model and project planning

This section proposes a structured model applying the philosophy of the DMAIC Six Sigma approach in the engineering design to improve quality, reduce cost and meet


schedule. According to Nilakantasrinivasan and Nair (2005), the DMAIC Six Sigma approach is an effective problem-solving methodology that has evolved overtime as the first cousin of total quality management (TQM) plan-do-check-act cycle. The true value of the DMAIC Six Sigma approach can be realised only when it is used to identify the root causes for problems and derive the solutions to overcome the root causes, see Figure 3 for the project planning of our study. Engineering design standards can be defined as a reference of measurement to be used in comparing the effectiveness of work against what is considered to be the preferred method of operation. The model maps the life cycle for the design package development against the DMAIC Six Sigma quality cycle and then aligns those cycles against the project management life cycle as: initiate, plan, execute, control and closeout.

Figure 2 Manufacture phases of KITAMEUBLE (see online version for colours)


Figure 3 The project planning (see online version for colours)

The proposed model may provide the engineers with the opportunity to get involved in the define phase of the project and carry out a full alignment with the business strategy. The improved process allows a cross-functional focus on the customer requirements from the start of the Six Sigma life cycle to meet or exceed the customer expectations with every engineering deliverable (for more details see Sadraoui et al., 2010).

3.2.1 Define This is the first step in the DMAIC cycle and it maps to the requirements and initiation. In this stage, the organisation should define its improvement activity goals to improve the design process. Improving the customers satisfaction should be the organisations strategic objective at the top level. At the operational (engineering) level, the goal might be to improve the design process and reduce the delivery delays, while at the human resources level, it is to reduce the turnover rate. Moreover, at the project level, the organisations goal should include reducing the design errors and increasing the productivity level.

If a project is accepted by the management and launched by the engineering department, the executive buy in must be strong. A project manager will be selected as the project leader and a Six Sigma quality team with an engineering background shall be assigned to the project. The project team may consist of individuals who exhibit an understanding of the scope and enjoy the relevant expertise to take the project to its successful completion. Once the team is identified, the roles and responsibilities matrix shall be started. An initial agreement shall be reached on the project parameters, surveys shall be conducted and information shall be correlated against the customer requirements and the internal processes that affect the customer.

1 Does the process clearly map to the business strategic goals/customer requirements?

2 Is this the best project to work on at this time, and is it supported by the business leaders?


3 Was a rough estimate used to determine the potential benefits?

4 Was a problem statement, which focuses on symptoms and not solutions, completed?

5 Was a gap analysis of what the customer of the design process needs vs. What the process is delivering completed?

6 Was a goal statement with measurable targets completed?

7 Was a supplier-input-process-output-customer (SIPOC) diagram (ISixSigma, 2006), which includes the primary customer and key requirements of the processes, created?

8 Was a drill down from a high-level process map to the focus area for the process completed?

In Figure 4, we indicate a clear comparison between 2007 and 2008 of evaluation of cost of non-conformity and in Figure 5, an evaluation of complaint between 2005 and 2008.

In this stage, one will begin with the presentation company KITAMEUBLE and the step of our project of which the goal is the optimisation and reduction of wood cost and the number of customer complaints. For this reason, one will practically follow the step of this stage.

Figure 4 Evaluation of cost of non-conformity between 2007 and 2008 (see online version for colours)

Figure 5 Evaluation of complaint between 2005 and 2008 (see online version for colours)


Corporate name: KITAMEUBLE is a completely exporting company which manufactures massive pieces of furniture, parts of pieces of furniture and elements out of wood. It is a limited company with the capital 5,800.000 DT (400.000 euro) and of average size to locate at Gabes km 5, 3052-Sfax-Tunisia.

The volume of the order is divided into two weeks; see Table 1 for manufacturing lead times for each workshop.

The person in charge gives to P1 the panels to be manufactured for each week and the panels to be delivered for each workshop (ZN and P2).

The person in charge gives to P2 the parts to be manufactured for each week. The person in charge gives to U4 the references to be manufactured per week. The manufacturing lead time for each workshop is indicated in Table 2. Week X: week of availability for the customer. 3.2.1.1 Wood consumption in Tunisia In such a configuration, the activity of furnishing in Tunisia is dominated by the abstract sector. In such a configuration, the activity of the furnishing in Tunisia is dominated by the informal sector. We estimate the number of small workshops of cabinetmaking joinery at 6000 units, while there are only 83 companies employing 20 persons and more. The area administrative center occupies about 16000 employees and creates 400 500 new jobs per year. The companies are largely concentrated in Tunis, 30%; Sahel, 24% and Sfax, 17%.

The majority of the companies produce small series to answer a generally seasonal request. Some are specialised in lounges and seats, the pieces of furniture of kitchens and bathrooms and the pieces of furniture of offices. Tunisian exports account for only approximately 23% of the value of production. They are concentrated in France (60%) and Libya (27%). The imports hardly represent because the local market of pieces of furniture is still protected by customs duties and specifications.

Company of the sector: the sector of wood, cork and furnishing gathers 190 companies, having manpower equal to or higher than 10, of which 29 are completely exporting (see Table 3).

Added value production: the production of the sector out of wooden, cork and furnishing was of the order 1,035 million dinars on average during the years 20032007, passing from 929 million dinars in 2003 to 1,320 million dinars in 2007. The added value reached 302 million dinars in 2007, that is to say 37% of the production (Figure 6).

Exports: it largely increased over the period 20032007 crossing (spending) so from 47 million dinars in 2003 to 63 million dinars in 2007 (see Figures 7 and 8).

Imports: the needs for the raw material sector are ensured at a rate of 90% per imports. The imports passed from 168 million dinars in 2003 to 283 millions of dinars in 2007 (Figure 9). Table 2 Manufacturing lead times for each workshop for KITAMAUBLE

Drying + flow Panelling Px delivery Flow Production Production Drying

Assembly + completion

Week X-7 Week X-6 Week X-5 Week X-4 Week X-3 Week X-2 Week X-1 Week X


Table 3 Repair of the companies employing ten people and more by activity and area

Activities TE ATE Total

Timber sawn, planed, impregnated 6 6 Joinery of btiments/charpente 3 30 33 Platings and panels derived from wood 10 10 Packing out of wood and pallets 4 5 9 Articles out of wood 3 6 9 Objects out of cork, basket making and esparto manufacture 4 4 8 Furnishing out of wooden and derived 15 17 132

Note: TE: completely exporting; ATE: others that completely export. Source: Arrange Promotion of Industry June 2008.

Figure 6 Evaluation of the production in the sector of industries of wood, cork and furnishing (20032007)

Note: Figures at current prices. Source: Ministry for the Development and the International Cooperation.

Figure 7 Evaluation of exports in the sector of industries of wood, cork and furnishing (20032007)

Source: National institute of the Statistics.


Figure 8 Repair of the principal products exported in 2007

Source: National institute of the Statistics.

Figure 9 Evaluation of the imports in the sector of industries of wood, cork and furnishing (20032007)

Source: National Institute of the Statistics.

Preliminary definition of the problem: our methodology of research particularly consists in detecting the causes which lead to non-conformities within company KITAMEUBLE. All one adopting the various stages of the installation from a step Six Sigma aiming at reducing the cost as well as the minimisation of a number of customers complaint. Indeed, we try to establish Six Sigma methodology in KITAMEUBLE, in Tables 4 and 5 we briefly indicate our methodology.

At the beginning of 2007, KITAMEUBLE fixed the objectives like the reduction of cost and the number of complaint. In 2008, KITAMEUBLE reached a level of 14,537, 360 for the cost/year but it is very high. In 2008, KITAMEUBLE reached a level of 61 for the number of complaint per annum but it is very high. The integration of the method for Six Sigma in 2009 has objective to have a cost of non-conformity lower or equal to 500 DT/month (11,000,000) and for the number of complaint lower or equal to 4 complaints/month (48).


Table 4 Objectives for KITAMEUBLE for the year 2009

Objective Indicators Formulate calculation Frequency of calculates Target

Document sources

To minimise the number of complaints

Complaint numbers

Complaint numbers sent by the customer per month

Monthly 4 Complaints

To minimise the cost of non-conformity

Non-conformity cost

[(Time consumed Cost labour) + (Matter consumed Price per m3)]

Monthly 500 DT Cards of non-conformity

Table 5 Cost of non-conformity of the products

Year Cost of non-conformity (in dinar)

2007 13,798,751 2008 14,537,360

For useful data, we particularly used many indicators in:

wood consumption in 2008: 52,954,791 m3 total cost of wood consumption in 2008: 2,330,010,000 DT total cost of non-conformity in 2008: 14,537,360 DT complaint in 2008 numbers: 61 customer complaint. In the first step, we try to develop both Snake diagram process (Figure 10) and DMAIC cycle (Figure 11).

Figure 10 Diagram snake of process


Figure 11 DMAIC cycle

3.3.2 Measure

In this phase, one will begin the measurement of our process with followed production cycle of the product of which the goal, theoretically, is to identify the produced parts that are characterised by a quantity of very high non-conformity.For this reason, one will follow the process in the three large workshops of KITAMEUBLE to calculate the parts non-conformity with the quantity and the number of the workmen, and consequently the numbers of complaints (see Figure 12). To apply this phase, one used tools of quality like the histogram, Pareto, the curves and the charts of controls, for statistics of wood consumption (see Table 6).

Workshops of KITAMEUBLE F0 = Cutting up F1 = Others F2 = Drawers F3 = Manufacture F4 = Carry

Workshop with ZN

To envisage the machines necessary so that one can do the work of sharpening. To make an inventory for all the sandpapering and cutting tools, to give each one has

a code and publishes a state on axes with the part conforms (PC) of the storekeeper, and has on the PC of Kita service.

To envisage a rack or can put the tools to arrange and with identification. Publish (Edit) a state for the tools which (who) sound always rise on machine one

identify code of the machine.


An agent of sharpening takes care of all the tools and he owes bet them loan has to use has all moment all moment.

Tools of the workshop for the use must be with a token (F0, F1, F2, F3, F4) between the setter and the heads of section and the token will be at the middle has the place (square) of the tool to ask.

The exit (release) of the tools of north zone green the south zone has to be with a good of exit, and this last must be seized in the PC under the responsibility of the storekeeper.

In the case of need for the plates or spare parts, etc. the agent of sharpening sends the request by e-mail or fax to Kita service.

Figure 12 Workshops of KITAMEUBKE

Table 6 Consumption of wood for P1 and P2 in m3

Month Consumption P1 and P2 January 2008 557.4889 February 2008 567.3404 March 2008 500.8848 April 2008 487.0187 May 2008 544.1772 June 2008 478.9232 July 2008 304.4751 August 2008 192.5828 September 2008 429.5796 October 2008 462.3984 November 2008 332.8181 December 2008 437.7919 Total 5295.4791


Workshops with the ZS: at the southern zone, there are three workshops of production and a deposit of storage, and each one has these tools.

Then

transfer of the workshop of sharpening to the new room to a dimension of P2 with the necessary machine to do the work of sharpening

to make an inventory for all the sandpapering and cutting tools which it is with the workshop, to give each one has a code and masters (teachers) in the good store to tidy up and to identify and to publish a state on axes on the PC

to make an inventory for all the sandpapering and cutting tools which it is A P2, to give each one has a code and the Masters in the store of the unit under the responsibility of the storekeeper to tidy up and to identify, and publish a state axes on the PC of the storekeeper

to make an inventory for all the sandpapering and cutting tools which it is A U4, to give each one has a code and the Masters in the store of the unit under the responsibility of the storekeeper to arrange well and well identify, and publish a state on axes on the PC of the storekeeper

to make an inventory for all the sandpapering and cutting tools which it is A P1, to give to each one a code and the Masters in the store of the unit under the responsibility of the storekeeper to arrange well and well identify, and publish a state axes on the PC of the storekeeper

edit a state for the tools which (who) sound always rise on machine one identify codes it machine (each unit all only)

only one agent of sharpening deals with all the work of sharpening for the three units and makes the delivery at the same time

in the morning the agent of the sharpening prepares the tools of P1 which its expensive, and to meet to him the need for P2 and U4, to 11 hr it leaves in P1 for the delivery their tools and seeks the tools to damage

after midday, the agent of sharpening prepares the tools of P1, and to meet at the same time the needs for U4 and P2, with 16 hr it makes delivered tools of P1

all the movements of tools, between or taken out, has to be with a check, and the check must be seized.

3.3.2.1 The non-conformity product control process Objectives and applicability: this procedure has the aim of describing and to define the rules of control of detection and treatment of non-conformities. It applies in the following cases:

non-conformity of the quality of the products bought with the reception non-conformity of the products in the course of production non-conformity of the products to final control non-conformity of the products finished before export non-conformity of the products finished at the customer.


The person in charge of the management for quality takes care of the application and the respect of this procedure. The non-conformity product process control is explained in Figure 13.

3.3.2.2 Points of production identification the gathering of data is based on the following chronological stages of the production, whose objective is to identify the problems appearing in this stage of production and consequently analyse and cure. Table 7 indicates different points of production and the plan of the data acquisition is indicated in Table 8.

In our case, one will use the diagram of Pareto for good to ensure themselves about the problem and to identify the source of wasting on the level of the number of non-conformity. One will be interested in the P2 unit for the months January 2008, February 2008 and March 2008 (see Table 9 and Figure 14 for more details).

Figure 13 The non-conformity product process control


Table 7 Points of production

Xi Points of production

X1 Various 1 X2 Behind X3 Turn X4 Moulding and cornice X5 Cutting up X6 Various 2 X7 Drawers X8 Manufacture X9 Carry X10 Assembly X11 Completion X12 Recovery X13 Control

Table 8 Plan of the data acquisition

What? Where? How? Who? When?

X1 P2 Normalises Not to specify Each day X2 P2 Normalises Not to specify Each day X3 P2 Normalises Not to specify Each day X4 P2 Normalises Not to specify Each day X5 ZN Normalises Not to specify Each day X6 ZN Normalises Not to specify Each day X7 ZN Normalises Not to specify Each day X8 ZN Normalises Not to specify Each day X9 ZN Normalises Not to specify Each day X10 U4 Measuring instrument Not to specify Each day X11 U4 Measuring instrument Not to specify Each day X12 U4 Measuring instrument Not to specify Each day X13 U4 Measuring instrument Not to specify Each day

Table 9 Parts produced for P2

Sections January 2008 February 2008 March 2008

X1 10,358 15,905 8,256 X2 1,540 260 540 X3 1,180 70 290 X4 2,523 535 980


Figure 14 Diagram of Pareto for the P2 unit

The chart custom shows us clearly of the 20 and 80, where 80% of wood consumption are carried out by X1 (various 1).

Since 2008, KITAMEUBLE decided to reduce the cost of non-conformity. The improvements made it possible to reduce the ratio up to the value of 1,500 DT/month.

The current project aims to go further in this step and to carry out an additional profit of 1,000 DT/month.

3.3.3 Analysis

After the stage of data gathering and the identification of the points of production to be followed, one finds that the stage of analysis of the data is followed. And for this last stage, one will analyse the collected data (data of the month January, February and March 2008).

This phase consists of analysing characteristics and their relations to determine the origin of the variations of which the goal is to identify their influences on the variability and the comprehension of the process (Table 10). To apply this phase, one identified the major potential causes by brainstorming and diagram of cause and effect (Ishikawa), and consequently one collects the data to check the major causes (Figure 15).

Brainstorming: to apply the brainstorming method, one has to use the method by turn which east characterises by an idea that advances by turn until everyone passes.And at the end of the meeting, there it is noted that these differential problems that can bring the causes of the problems for the parts of non-conformities:

the difficulty of having a PC of the first blow the not availability of labour the not availability of the tools of assembly and measurement (screw, turns screw) the not availability of a stock of the squares in the store competence of the workmen


manual work difficult task miss concentration drink to suffer by the sun drink drying badly transport of the parts by the truck numbers insufficient controllers space insufficient workshop poor yield.

3.3.4 Improve The aim of a standardised review and verification process is to eliminate defects while sharing the best practices among the designers. As more experience is gained, the amount of time required for thorough review and verification is reduced. Table 10 Numbers produced parts and non-conformity for P2 (January 2008)

No. Date Reference Designation Produced quantity NBR and PNC

1 3 January 20300620100 Behind 30 19

2 7 January 20300653000 Behind 50 28

3 8 January 20200000200 Cornice library 1,800 mm

114 91

4 15 January 20300160700 Behind 60 14

5 16 January 20200000200 Cornice library 1,800 mm

20 10

6 17 January 31790172202 Baseboard (1 m 96 cm)

188 101

7 21 January 31700000100 Plinth for library 1,800 mm

19 12

8 23 January 20200K24001 Cornice (1) 25 10

9 23 January 20200K24003 Cornice (3) 25 16

10 25 January 20400527301 Moulding face 60 13

11 29 January 20400525303 Right moulding 60 24

12 31 January 20300160700 Behind 32 26


Figure 15 The causeeffect diagram

As part of an integration plan, an engineering design development team might set up the scope document and receive a sign off from all stakeholders. SIPOC is one of the tools that can be used during the measure stage. Standardised review and verification processes may provide better familiarity for designers with the design they are developing, solid guidelines for the new team members to refer for quality standards, an enhanced feeling of ownership of the design, an overall improvement in review and verification skills, less time used on misguided review and verification and improved customer satisfaction.

3.3.4.1 Solutions identification by the use of AMDEC In order to identify the most probable causes, we will use the systematic process AMDEC which makes it possible to identify the potential modes of failure and to treat them. We will generally note each criterion on a scale (from 1 to 3) by creating a grid adapted to the company and the studied system. But in our case, we will remove the frequency criterion by what our problem is continuous (Tables 1113).

After the analysis of the data, we find that there are causes which are more critical than others, and then criticality found after the actions taken of the improvement lower than criticality is found front. It is thus concluded that the correction carried out is effective. This procedure defines the steps to be followed to engage the corrective actions, and prevention started following non-conformities, customers complaints, of


accidents/incidents and data analysis. It applies to all the processes of the system of management of quality of KITAMEUBLE.

non-conformity: any variation compared to standards, practical, measures, regulations and performances of the systems of management

corrective action: action undertaken to eliminate the causes from a non-conformity, a defect and any other existing undesirable event in order to prevent that they do not reproduce

preventive action: action undertaken to eliminate the causes from a non-conformity, a defect and any other potential undesirable event in order to prevent that they do not occur

to check the characteristics of the products (dimensions, colours, etc.) according to the table of the samples, plans

to check the conformity of the matter compared to the ordering and the list of packing (importation)

to check the mark of wood (choice) to check the quantity to check the sections (compared to the list of packing) to check moisture (by survey). 3.3.4.2 Panels choice There are three types of panels (Figures 1618):

AA: panels completely visible with B: panels fairly visible. Table 11 Gravity

Gravity

Note G Effects

1 Cost of non-conformity is


Table 13 Analyse modes of failures of their effects and their criticalities C

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The chart shows us a reduction of cost of non-conformity on a level equalising at 312,300 DT. And it is observed that the reductions in this objective are more significant for the months April 2009 and May 2009 because of panels choice (Figure 19 and Table 14).

The chart shows us a reduction of a complaint number on a level equalising at 3. And it is observed that the reductions in this objective are more significant for the month of January 2009 and March 2009 because of the use of the cleats out of wooden and the nodes (Figure 20).

Figure 16 Panel AA

Figure 17 Panel AB

Figure 18 Panel BB

Figure 19 Histogram of cost of non-conformity (20082009)

Table 14 Cost of non-conformity (20082009)

Month Cost of non-conformity

January 2008 237,510 February 2008 267,540 March 2008 1,848,850 April 2008 671,823


Table 14 Cost of non-conformity (20082009) (continued)

Month Cost of non-conformity

May 2008 2,511,450 June 2008 382,200 July 2008 312,475 August 2008 575,894 September 2008 2,612,227 October 2008 325,576 November 2008 482,510 December 2008 4,309,305 January 2009 352,574 February 2009 485,428 March 2009 742,367 April 2009 192,786 May 2009 212,300

Figure 20 Histogram of complaint number (20082009)

For choice AA (see online version for colours)


For choice BB (see online version for colours)

Defects refused in AA, AB and BB (see online version for colours)

Cost histogram of non-conformity for 2008 in the first five months of 2009

Histogram of complaints number for 2008 in first five months of 2009

Month Complaint numbers

January 2008 3 February 2008 3 March 2008 8 April 2008 11 May 2008 4 June 2008 7 July 2008 5


Histogram of complaints number for 2008 in first five months of 2009 (continued)

Month Complaint numbers August 2008 0 September 2008 2 October 2008 7 November 2008 6 December 2008 5 January 2009 1 February 2009 6 March 2009 0 April 2009 4 May 2009 3

Count 15: complaint numbers (20082009).

3.3.5 Control This is the fifth step in the DMAIC cycle and it maps to contract review and closeout. The previous four stages shall conclude to the new system that must lead to the intended improvements. The organisation should set control measures for this new system through modified design and development procedures, the necessary training to secure the skills required to implement new policies and by allocating budgets to deploy the necessary resources (see for more details De Koning and De Mast, 2006). The design team shall ensure that the improvements, once implemented, hold value and will not revert to the error-riddled baseline. The team shall maintain a log to allow an effective review for the customers and the design team and should seek feedback from the stakeholders. If the feedback is negative, corrections should be taken immediately (De Mast, 2006).

The design team may benefit the following due to these control measures: an increase in reliability and accuracy, a reduction in customer complaints, cycle time reduction and a reduction in rework. Graphical charts showing the planned vs. the actual project cost, the expended man hours and the physical work progress can be used as tools during the control stage. DMAIC is closed by the test phase which has a role to supervise the control one of our process by using the control charts and to check success of the results of the improvement carried out (Dewhurst et al., 2003; Goh and Xie, 2004).

After the use of the improvements in the project the number of complaint has to decrease to reach a minimal level of zero complaints for the month of March 2009. At the cost of non-conformity has to decrease to reach a minimal level of 192,786 DT which has large influences on the cost of project which results the increase from the profits.

Use of the control charts: after improvements, we should make a control for our process, where we observe that after the improvements of a good result.

The layout of the control chart curve P (P2) for the month of January and February 2009 (Figures 21 and 22), obtained from software Minitab 14, shows that all points inside are limited of control, therefore the process seems to be controlled statistically, it does not have their assignable causes which affect the process. We can use the limited final ones for the study of a process in real time.


The layout of the control chart curve P (ZN) for the month of February and March 2009 (Figures 23 and 24), obtained from software Minitab 14, shows that all points inside are limited of control, therefore the process seems to be controlled statistically, it does not have their assignable causes which affect the process. We can use the limited final ones for the study of a process in real time.

Figure 21 Control chart P for P2 (January 2009)

Figure 22 Control chart P for P2 (February 2009)

Figure 23 Control chart P for ZN (February 2009)


Figure 24 Control chart P for ZN (March 2009)

4 Conclusion and discussion

Six Sigma is a method of management, particularly in effective progress. They exit a strongly connoted step quality in the beginning, it is relatively simple in theory. Six Sigma is founded on an eternal rule which is in any case checked, since the night of times since the man trades. To satisfy the customers, it is necessary to deliver products of quality.

Theoretically, all the processes of services and businesses could be at this level, but the majority of the companies function today to three sigma, and thus lose 1015% of their total income because of these errors and wastage. It is clear that the tools which Six Sigma brings are not new at all. The innovation lies rather in the fact that it brings a new philosophy of management to the level of the company. This philosophy aims at setting up a culture of directed company customer, and who bases himself on concrete facts and data for the decision-making. Today, according to the experiments among many customers, these two elements are not always applied in spite of the statements of good intentions. Six Sigma makes it possible to set up a durable approach to cure it. Moreover, Six Sigma is based on an infrastructure of agents of change which work in all the departments of the company, not only in one quality department. These individuals are called Green Belt (part-time people), Black Belt (full-time people) and Master Black Belt (managers raftered in strategy for improvement of the processes).

The main objective to improve the process is simply the reduction of dispersion. This takes place by the application of projects known as of improvement Six Sigma which, in their turn follow the series of stages DMAIC of Six Sigma To define (which is the defect, to identify the projects according to the key characteristic), measurer (to determine which is measurement associated with the defect observed, to define an action plan which helps to identify the sources and the potential causes of the defects, analyser (to determine which are the potential causes of the problem which affect the key characteristics, Amliorer (to improve the process or the product, to eliminate or control the sources of variation which affect the key characteristic and to control (to control its stability and capability).


These indices enable us to obtain good interpretation and to make the adequate decisions in the companies and specifically within the wood company KITAMEUBLE, of which the goal to improve the process by reducing the numbers of the parts non-conformities and to minimise the numbers of complaint customers. This improvement is effective since the same quality for more details see for example studies of Kwak and Anbari (2006) of wood was kept and to achieve the goal. To apply this step and to check the results obtained, we used the tools of quality, such as Pareto, the histogram, the curves and the control charts using the software as Minitab 14 and AMDEC.

Acknowledgements

The authors wish to acknowledge their appreciation towards the reviewers and the editor for their valuable comments and suggestions which have enhanced the quality of this paper.

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