Design for Six Sigma (DMADV) Methodology for Power Inverter Development

Hussein Salem Ketan Prof Karrar Mahdi Husain EngineeringCollege Baghdad University\Iraq

Abstract

This research highlights the importance and the role of Quality Function Deployment (QFD) in determining the critical customer requirements in developing the Power Inverter pure sine wave (1 KVA) product produced by the Electrical Industries Company (EIC). Define Measure Analyze Design Verify (DMADV) methodology, which is one of the Design for Six Sigma (DFSS) methodologies was applied taking the first two phases as a part I, in phase one (Define) applying Affinity Diagram (KJ Analysis) and Kano Model tools to consist a powerful information base through brainstorming. In phase two (Measure) Voice of Customer (VOC) captured by Questionnaire form and applying Quality Function Deployment (QFD) tool in determining the Relative Importance (RI) for the Technical Requirements (TR) so that to choose the first three having the highest (RI) number which consider the Critical Customer Requirements (CCR) these are for power inverter product (Type of MOSFET “Metal-Oxide Semiconductor Field-Effect Transistor”, Transformer design, cooling system). Key words: DFSS, power inverter, Affinity diagram (KJ Analysis), Kano Model, QFD (House of Quality HOQ).

1-Introduction willing to pay higher prices [16]. Six In today’s competitive environment, Sigma provides specific methods to re- the companies that succeed will be create the process so that defects and those which develop products that errors never arise in the first place [7]. satisfy customer needs better than the The central idea of Six Sigma products of their competitors. management is that if you can measure Therefore, it is necessary that the defects in a process, you can companies fully research such needs, systematically figure out ways to and generate ideas and solutions that eliminate them, to approach a quality can best satisfy them [5]. Every level of zero defects [2]. Statistically, product is sold in market for a price. Six Sigma refers to a progression in For god products the customers are which the series between the mean of a

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34 method of excellence measurement and by the Electrical Industries Company the adjacent specification edge is at (EIC) least six times the standard deviation of the process [14.] As defined by Creveling, Design for 2- Design for Six Sigma (DFSS) Six Sigma (DFSS) is a proactive DFSS is a disciplined and rigorous approach to building the Six Sigma approach to service, process, and performance into the upfront design of product design through ensuring that a new product, service or process. It is new designs meet customer a systematic methodology for requirements prior to launch [4]. designing new Six Sigma quality Adopting DFSS approach considered a products to exceed customer powerful source to the company expectations through the use of increasing its profits where proven engineering tools and training in the practically that increasing Quality product development life cycle [10 .] lowering cost through reducing waste A continuous improvement of the and high competition by achieving existing processes (DMAIC) and new customer requirements and with the developments (DMADV) represent highest sales ratios inventories reduces. linchpins of the Six Sigma Figure (1) explains how DFSS can methodology. Classic six sigma lower production cost through dealing DMAIC (Define, Measure, Analyze, with defects in the design stage. Improve, Control) – the improving process consists of five diffused and interacted stages resulting in stepped improvements of existing processes. Similarly the process designing new processes and products consists of five stages (Define, Measure, Analyze, Design, and Verify). The DMADV process as a DFSS methodology is principally used in situations where improving of the existing processes is no longer adequate owing to feasibility and cost-effectiveness [8]. In this work Figure (1): Cost analysis when applying the Quality Function Deployment (QFD) is implemented with some DFSS [9]. DFSS important tools to determine the 3- Power Inverter critical customer requirements in Power inverter is a device that developing the Power Inverter pure converts electrical power from DC sine wave (1 KVA) product produced form to AC form using electronic

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35 circuits typically; it is possible to procedure that provide a rich set of convert battery voltage into tools to achieve project goals. conventional household AC voltage allowing you to use electronic devices when an AC power is not available. There are basically three kinds of Inverter out of which, the first set of inverters made, which are now obsolete, produced a Square Wave signal at the output [3]. The Modified Square Wave also known as the Modified Sine Wave Inverter produces square waves with some dead spots between positive and negative half-cycles at the output. The cleanest Utility supply like Power source is provided by Pure Sine Wave inverters. The present Inverter market is going through a shift from traditional Modified Sine Wave Inverter to Pure Sine Wave inverters because of the Figure 3:various DFSS methodologies [10] benefits that these inverters offer these .5 DMADV methodology and types explained in figure (2)[3]. Implementation The application of DMADV is used when a client or customer requires product improvement,adjustment,or the creation of an entirely new product or service. The application of these methods is aimed at creating a high- quality product keeping in mind Figure (2): types of inverter outputs [3]. customer requirements at every stage of the production[15] Figure (4) below

show the flow chart of DMADV 4- DFSS methodologies methodology used in this research to DFSS has a various methodologies develop the power inverter pure sine used to design or redesign products, wave(1 KVA)produced by(EIC)to processes or services as shown in make it more competitive in the figure (3) below: inverters market through achieving The first one DMADV is a common lower cost with high customer methodology which is beneficial to satisfaction by using some important improve products through its precise development tools which are varies

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36 from phase to another but they are a complement each other in the same time

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Product Identification

KJ Analysis Identify CR Kano Model

Define Phase

Customer Interviews, applying Capturing VOC Questionnaire and benchmarking

Measure Phase QFD Converting CR to CCR

Analyze Phase FMEA Transforming CCR to CTQ

Detailed design for the old Detailed Design and new product part Design Phase

Is the product NO Prototyping meeting customer Redesign satisfaction? Verify Phase Yes Production Launch Figure (4): DMADV methodology flow chart

1.1 Define phase Implementation of the quality distinguish and exact define the improvement model begins with the variables that will be deal with [11]. Define phase. In the beginning of 1.1.1. Affinity diagrams (KJ work on the project of quality Analysis): improvement, the responsibilities have been identified, as well as the It is a structured method to discuss, approach to the problem and the steps analyze and have a coherent vision of in solving the problem. It is a complex and hard to define imperative to immediately begin to problem. The problem under study define the scope of the project and to must be well defined and reported,

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38 and this is written on the top left of alternative or supper header “relation the board [1]. between two or more groups” cards The main steps: can be prepared also. Idea generation: list of ideas resulting from brainstorming must Finalize the Affinity diagram: written on a sticker paper that placed putting the problem statement on the on a white board or wall randomly. top and the header, alternative header Grouping the ideas: here grouping and supper header cards above every similar ideas together in groups with a group then connecting lines between quiet and accurate work. the header and all the ideas in a hierarchical way which gives well Create Affinity cards: also called analysis for the problem. Figure (5) header cards it is a fundamental idea shows the Affinity diagram for the placed on the top of every group, here power inverter development.

Developing power inverter customer satisfaction and market competiveness

Reducing Producing Improving size, weight products with product and cost with multi - powers efficiency and

performance

Transformer design Metallic body PCB design Reducing loss in Cooling system Number of current and drop design MOSFET voltage

Figure (5): Affinity Diagram (KJ Analysis).

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 Acceptable size and weight with respect to the cost  Digital meters  Multi – powers  Services after sale  Stability of

 Auto shut down at low battery voltage  Auto shut down at overload  Alarm (buzzer)  Auto shut down in the case of frequent operation of power switch  Auto conversion from mains electricity supply to the inverter  Overheat protection  Auto control the charging current according to the battery capacity Figure (6): The Kano Model for Power Inverter Development

1.1.2. Kano Model: Basic characteristics (Must –be): it is the not spoken needs that already The Kano model was developed in must be available in the product at 1984 by Noriaki Kano [5]. It aims to least to achieve. connect the requirements fulfilled by Performance needs: it is the spoken products or services with customer needs by the customer that affect satisfaction and identifies three types customer satisfaction, as the level of of requirements that influence the product performance within this ultimate customer satisfaction [13]. area is high it will be accepted by the These types represented on the form customer. shown in figure (6) for power inverter Excitement characteristics development which describe all the (Delighting the customer): it is also specifications needed to develop the not spoken needs but in the positive product: side can be called Wow the customer the product within this area have a

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40 very customer satisfaction and market TGW (Things Gone Wrong) competition. TGR (Things Gone Right)

1.2. Measure phase 4- Product quality and general performance. In this phase data is gathered and 5- Low cost. analyzed that describes with precision 6- Product life. and accuracy [12]. The measure phase 7- Easy to maintain and starts with getting the voice of the availability of spare parts. customer (VOC) after the The questionnaires took with (30) brainstorming stages in the previous forms in four types as in figure (7) tools (KJ analysis & Kano model) one for the customer importance level which provide a clear view to the in general and the second, third and customer needs that must take in the fourth for the availability of these questionnaire as listed: needs in the EIC product, Chinese 1- Small Size. product and Indian product 2- Light Weight. respectively which is called 3- Various powers (1 KVA, 2 benchmarking process the results can KVA). be seen in the next tables (1, 2, 3 and 4).

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Very Unimport Low Import Very Customer Needs unimport ant important ant important ant 2 3 4 5 1

Small Size

Light Weight

Various powers (1 KVA, 2 KVA)

Product quality and general performance

Low cost

Product life

Easy to maintain and availability of spare parts

Figure (7): Questionnaire form

Table (1): Questionnaire form 1: customer needs to be available in the product in general

Importance No. Customer need level 1 Small Size 3.6 2 Light Weight 3.4 3 Various powers (1 KVA, 2 KVA) 3.8 4 Product quality and general performance 4.9 5 Low cost 4 6 Product life 4.7 7 Easy to maintain and availability of spare parts 5

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Table (2): Questionnaire form 2: availability of the same specifications in our product produced by EIC

availability No. Customer need level 1 Small Size 1.8 2 Light Weight 1.2 3 Various powers (1 KVA, 2 KVA) 1 4 Product quality and general performance 4.4 5 Low cost 2.1 6 Product life 5 7 Easy to maintain and availability of spare parts 5

Table (3): Questionnaire form 3: availability of the same specifications in a Chinese product

availability No. Customer need level 1 Small Size 4.4 2 Light Weight 4.9 3 Various powers (1 KVA, 2 KVA) 5 4 Product quality and general performance 3.1 5 Low cost 4.3 6 Product life 1.9 7 Easy to maintain and availability of spare parts 2

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Table (4): Questionnaire form 4: availability of the same specifications in an Indian product

availability No. Customer need level 1 Small Size 1.6 2 Light Weight 2 3 Various powers (1 KVA, 2 KVA) 5 4 Product quality and general performance 4.4 5 Low cost 3 6 Product life 4.2 7 Easy to maintain and availability of spare parts 3.7 1- Identify the “Whats” which are 1.2.1. Quality Function Deployment the customer requirements based on the Affinity diagram and (QFD) Kano model placed on the left Quality function deployment has side of the HOQ and customer been used to translate customer needs priority stated by 1 to 5 rating and wants into technical requirements mentioned in the Questionnaire. in order to increase customer 2- Establish product technical satisfaction (Akao, 1990). Quality characteristics which should be function deployment utilizes the measureable and meaningful they house of quality, which is a matrix are: providing a conceptual map for the  Transformer size design process, as a construct for  Number of power transistors understanding customer requirements (MOSFET) (CRs) and establishing priorities of  Metallic body technical requirements (TRs) to  PCB size satisfy them [6]. The aim of the QFD  Cooling system or HOQ is to determine the critical  Type of MOSFET customer requirements (CCR) among  Protection system list of the technical requirement  Warranty analyzed and the next stages of the  component connection project will focus on these (CCR), the  Microprocessor programming main steps for building the HOQ are: system

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 PCB design and negative) called tradeoffs or  Transformer design correlation.  Availability of meters 6- Importance ratings calculations 3- Find the relationship between the using weighting factors for the customer requirement and symbols like (1-3-5, 1-3-9, 1-2-4) technical characteristics using then multiplying it with customer known symbols in order to importance ratings. determine the relationship levels 7- The final stage of the QFD is the (strong, medium and weak) analyzing of the entire matrix scoring (5, 3 and 1) respectively. and finding the final product 4- Technical evaluation takes place plans. by comparing with prior products or competitive products using In this research the data analyzed product benchmarking placed on through Microsoft EXCEL QFD the right side of the HOQ. template and taking the first three 5- Build the HOQ roof, which important technical requirements consists of positive and negative which will considered in the next interactions between customer stages of the project. These CCR requirements and technical listed in the table as following in table requirements also using symbols (5): for (strong, medium, positive,

Table (5): most important technical requirements

Relative No. Technical requirements importance weighting 1 Type of MOSFET 11.4 2 Transformer Design 11.3 3 Cooling system 11.2

QFD calculations and analyzing the The importance weighting for each matrix to find the most three technical requirement can be important characteristics among the calculated from the equation below technical requirements. [17]:

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(4 ∗ 5) + (4.7 ∗ 0) + m (5 ∗ 1) = 79 yi = ∑(pij)(xi)

i=1 The Relative Importance Weighting (RIW) which is normalized Where: importance scores can be calculated yi = technical requirement (y1, y2, as follows taking first technical y3, ………, yn) requirement (y1) as example: pij = the relationship score between customer requirements and technical 13 requirements. RIW푦1 = 푦1/ ∑1 푦 = Xi = importance level for the 0.0957 ∗ 100 = 9.57 customer requirements. So the importance weighting for the first technical requirements ( y1 ) The figure (8) shows all the which is (transformer size) can be calculations for the HOQ of the power calculated as follows as examples: inverter product development.

푦1 = ∑(3.6 ∗ 5) + (3.4 ∗ 5) + (3.8 ∗ 5) + (4.9 ∗ 0) +

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Figure (8): The House of Quality

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6- Conclusion Wiley and Sons, Ltd., UK, 2012, 1. The QFD considered very p.26. effective tool in determining the 2- Brue, Greg, “Design for Six CCR in the cases of the company Sigma”, the McGraw-Hill being not capable of achieving all companies, Inc., USA, 2003,p.4. customer requirements and there 3- Dixit, Sanjay,Tripathi, is a need to focus on the most Ambreesh and Chola ,Vikas, important characteristics. “800 Pure Sine Wave Inverter 2. In developing the Power Inverter Reference Design”, Texas, (1 KVA) produced by EIC the Instruments, 2013, p.3. HOQ applied after investigating 4- El-Haik, Basem, and Mekki, the product features by KJ Khalid S., “Medical Device analysis and Kano model tools Design for Six Sigma a Road through brainstorming which Map for Safety and gives the QFD process a Effectiveness”, John Wiley & powerful information base that sons, Inc., Hoboken, New make the analysis results Jersey, 2008, p.16. achieving high customer 5- Fain, Nusa, Kline, Mihanel satisfaction. and Dohovnik, Jozel, 3. QFD results where three CCRs “Integrating R&D and (Type of MOSFET, Transformer Marketing in New Product Design and Cooling system) with Development”, Journal of their relative importance (11.4, Mechanical Engineering, 57 11.3 and 11.2) respectively. (2011) 7-8, pp. 549-609. 4. These CCRs will have an 6- Gonza´lez, Marvin E., essential role in the next stages Quesada, Gioconda and Bahill, coming in paper part II to A. Terry, “Improving Product determine (CTQ) by applying Design Using Quality Function (FMEA) in (Analyze phase) to Deployment: The School focus on particular part from the Furniture Case in Developing product to develop in (Design Countries”, Marcel Dekker, Inc., phase) and produce the product in QUALITY ENGINEERING (Verify phase) to meet customer Vol. 16, No. 1, pp. 47–58, 2003. needs. 7- Harry, Mikel, & Schroeder, Richard, “Six Sigma”, Doubleday a division of random 8- References house, Inc., New York, 2000, p.vii. 1- Barone, Stefano, “Statistical 8- HOŘÍNKOVÁ, Barbora, and Managerial Techniques for PLURA, Jiří, “Possibilities of Six Sigma Methodology”, John Product Quality Planning

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Improvement Using Selected Model Analysis of Customer Tools of Design for Six Sigma”, Needs and Satisfaction at the Brno, Czech Republic, EU, Shanghai Disneyland”, Proc. of 2015, p.3. the 5th International Congress of 9- Narayanan, H., and Khoh, S. International Association of B., “Deploying Design for Six Societies of Design Research Sigma™ in New Product (IASDR), Tokyo, pp.26-30, Development”, IEEE, 2008, pp. August 2013. 1110-1115. 14- Sankhla, Vijayendra Singh 10- Patil, Vipin S., Andhale, Sunil and Tege, Saurabh, R., and Paul, Izhak D., “A “Methodology, Implementation Review of DFSS: Methodology, and Future Research on Six Implementation and Future Sigma Approach”, Journal of Research”, International Journal Scientific and Engineering of Innovations in Engineering Research, 2015, 2(1): 47-51. and Technology (IJIET),Vol.2 15- Selvi, K and Majumdar, Rana, Issue 1 February 2013, pp. 369- “Six Sigma- Overview of 375. DMAIC and DMADV”, 11- Pavletic, Dusko and Sokovic, International Journal of Mirko, “Quality Improvement Innovative Science and Modern Model at the Manufacturing Engineering (IJISME), ISSN: Process Preparation Level”, 2319-6386, Volume-2, Issue-5, International Journal for Quality pp. 16-19, April 2014. research, Vol.3, No. 4, pp. 309- 16- Yang, Kai, and El-Haik, 315, 2009. Basem S., “Design for Six 12- Pendokhare, Devendra G., Sigma a Road Map for Product Quazi, Taqui and Kulkarni, Development”, McGraw – Hill Prasad S., “Redesign and companies, Inc., USA, (2009), Manufacturing by Using p.59. DMADV Method”, International 17- Yang, Kai, “Voice of The Journal of Research in Customer Capture and Engineering and Technology, Analysis”, McGraw-Hill Volume: 04 Issue: 02 | Feb-2015 companies, Inc., USA, (2008), pp.144-149. p.242. 13- Qiting, Pan, Uno, Nobuhiro and Kubota, Yoshiaki, “Kano

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لتطويرالعاكسة الكهربائية (DMADV) التصميم لستة سجما منهجية

حسين سالم كيطان أستاذ كرار مهدي حسين قسم الهندسة الميكانيكية كلية الهندسة – جامعة بغداد /العراق

الخالصة

هذا البحث يسلط الضوء على اهمية ودور )QFD( في ايجاد متطلبات الزبون الحرجة في تطوير العاكسة الكهربائية ذات الموجة الجيبية النقية )KVA1( المنتجة بواسطة الشركة العامة للصناعات االلكترونية. سوف تطبق منهجية )DMADV( والتي تمثل واحدة من منهجيات التصميم لستة سجما ))DFSS وتم تطبيقها باخذ اول مرحلتين في الجزء االول، في المرحلة االولى )التعريف( يتم تطبيق االدوات مخطط االسبقية ونموذج كانو لتكوين قاعدة معلومات قوية من خالل العصف الذهني. في المرحلة الثانية )القياس( يتم استحصال صوت الزبون )VOC( بواسطة نموذج استبيان وتطبيق أداة نشر وظيفة الجودة )QFD( اليجاد االهمية النسبية للمتطلبات التقنية ويتم اختيار اول ثالثة منها والتي تعتبر المتطلبات الحرجة بالنسبة للزبون )CCR( وهي بالنسبة للعاكسة الكهربائية )نوع الترانزستور، تصميم المحولة، نظام التبريد(.. الكلمات المفتاحية : التقييم لsigm-6 , محول الطاقة , تحليل kj , نموذج Kano , وظيفة نشر النوعية . QFD

حسين سالم كيطان مجلة اتحاد الجامعات العربية للدراسات والبحوث الهندسية العدد 2 مجلد 23 عام 2016 كرار مهدي حسين