On the use of Quality Function Deployment (QFD) for the identification ...

On the use of Quality Function Deployment (QFD) for the identification of risks associated to warranty programs Francesco Costantino, Margherita De Minicis, Vicente González-Prida, Adolfo Crespo a

Department of Mechanical and Aerospace Engineering, University of Rome “La Sapienza” b Department of Industrial Management, School of Engineering, University of Seville

Abstract: Stating the increasing interest in warranty management issues, due to growing customer expectations both on product and service, the paper deals with the identification of risks associated to warranty programs. The use of Quality Function Deployment (QFD) methodology is suggested as it allows to deeply analyze customer needs. By prioritizing warranty activities according to a customer perspective, the QFD analysis identifies the most risky aspects which, once identified, need to be deeply analyzed by qualitative and/or quantitative risk analysis. Applicability of the method is tested through a case study on an agricultural and gardening equipment. Keywords: QFD, Warranty management, risk management.

1. INTRODUCTION Nowadays, the performance of a product and its functional characteristics are no longer the only aspects to consider. Competitive products must perform satisfactorily even over their useful life so the role of after-sale services becomes crucial. In particular, the warranty period is certainly a delicate moment of product’s life as, during this period, producers must afford costs that sensibly impact on their business performances. But the development of an efficient warranty program passes through a systematic process of identifying, analyzing, and responding to risks likely appearing during a program of warranty assistance. The first step of this risk management process consists in the identification of all those risks which can be associated to the development of a warranty program. This step is often one of the most critical as numerous aspects must be considered to carry out that analysis, such as customer’s requirements and technical factors. Despite this, there is a lack of dedicated tools to support this kind of analysis. The best warranty assistance is that one that is not necessary to be applied. However, it is obviously not what happens in real situations. Therefore, based on the above mentioned considerations, this paper proposes the application of Quality Function Deployment (QFD) methodology for the identification of risks associated to warranty programs. 2. WARRANTY AND WARRANTY RISK MANAGEMENT 2.1. Warranty and the Customer Relationship Management Warranty management deals with decision making at strategic and operational levels. This requires taking into account the interactions between engineering, marketing and post-sale support elements of the manufacturing firms [1]. Therefore, Warranty management needs to be treated today not as a cost centre but as an asset that can create a higher value of the business performance. An effective warranty management requires the integration of leading practices finding critical points and risky aspects in the decision process. These critical points will depend on the already existing service management of the organization and its warranty management capabilities, helping to improve business performance by maximizing cost reduction and value creation. For example the reduction of claims processing time and costs, as well as number of claims processing personnel may certainly result in lower warranty costs and higher levels of customer retention. As a consequence of today’s technologies, higher levels of knowledge, experience and training will be required in the warranty technicians. It is clear that one of the most important parts inside the management of a warranty program is the relationship with the client. The CRM (Customer Relationship Management) is used not only to define a strategy of business centered in the client, but also to include a group of applications useful to deal with data related to clients, complaints and, in general, the commercial activity of a company. The CRM is used often as a module for the customers’ management inside ERP software. Originally, the CRM was more focused to marketing and commercial aspects. Nevertheless, a CRM module can be adapted for the warranty management, which should allow the company: to identify

CUSTOMER

products and services that clients require to be attended; to optimize assistance times and information channels; to identify clients' groups in order to develop warranty strategies; to be aware about the current after sales necessities of the clients; to increase sales of the company together with the client's satisfaction; among others. COMMUNICATION CHANNELS

INVOLVED DEPARTMENTS

Web and Email

Aftersales

On Field Technicians

Management Board

Call Center

WARRANTY INFORMATION

Quality

Partners and Subcontractors

Engineering

E-Warranty System

Manufacturing

FRONT OFFICE

BACK OFFICE

Figure 1. CRM for the proposed framework The customer relationship management (just as part of an ERP or as a complementary system), includes operational areas and tasks that deal directly with the client (“front office”), and other ones more analytical where different parts of the company are closely involved (“back office”) representing the business intelligence, as it is shown in Figure 1. The main part of any CRM strategy will be the Data Base, which can provide very interesting information about complaints, repetitive failures, hidden defects [2], quantitative and qualitative analysis, statistical results [3], etc. Then this module represents the starting point of a risk identification process, as explained in the following paragraph. 2.2. Risk management from a warranty perspective On the one hand, by a producer’s point of view, warranty is a necessary process to which an additional cost, to be summed for research and development, production, distribution and marketing. The amount of warranty costs can vary according to the category of product-service but the range of variation is between 2% and 15% of all sales. On the other hand, the main consequence of a poor after-sale service is customer dissatisfaction, which in many cases may have an even more negative effect to organization business. Warranty management is then a key process for organizations aiming to improve business performance. At the same time, by involving numerous different actors, such as marketing and production, it is certainly an important source of risks with respect to customer satisfaction. In recent years, ever more attention has been paid to the systematic process of identifying, analyzing, and responding to risk likely appearing during a program of warranty assistance, which is called warranty risk management. The importance of this process resides at first in the knowledge of risks. Unknown risks in fact cannot be managed, then it is impossible to minimize their probability and negative consequences to warranty objectives. On the contrary, known risks are those that have been identified and analyzed so it is possible for execute managers to plan mitigation action aimed at reducing their negative effects. For example, considering the after-sale service, the application of general contingency based on past experience with similar programs can be considered a commonly used mitigation solution. Those known risks that are threats to the warranty program may be accepted if they are balanced with the reward that may be gained by taking the risk. Likewise, risks that are opportunities may be pursued to benefit the program’s objectives. Considering a warranty program, many disciplines are involved in the development of warranty assistance such as maintenance, outsourcing strategies, quality and cost estimation [4]. The complexity in the number of issues to be treated and differences characterizing these aspects make it difficult to immediately outline risks associated to the management of a warranty program. While contributions dealing with specific subjects like risk and spare parts estimation [5] or risk and maintenance decisions [6] are well established both in literature and in practical application, a structured approach to the definition of warranty management risks as a whole is still missing. The warranty risk management process is composed of different stages (ISO 31000:2009): (i) Establishing the context; (ii) Risk assessment (risk identification, risk analysis, risk evaluation); (iii) Risk treatment; (iv) Monitoring and review. The first step is establishing the context, that is define the external and internal parameters to be taken into account when managing risk and set the scope and risk criteria for the remaining process (Table 1). Once risk management process’s boundaries are set, risk identification is needed to

determine which risks can affect the warranty program and to document the characteristics of each one. The following step of the process is risk analysis, which usually can be divided in qualitative and quantitative. The main objective of this analysis is assessing the impact of the identified risks in the warranty assistance in order to prioritize them according to their potential effect on the program objectives, determining the importance of addressing specific risks and guiding risk response. This analysis requires that the probability and consequences of the risks are evaluated using established qualitative or quantitative methods and tools. Risk evaluation involves comparing the level of risk found during previous steps of the analysis with risk criteria established when the context was considered. Then, the need for treatment can be considered and different proposals can be evaluated during the last step of risk management process. Table 1. Inputs/Output Summary. Risk management in a warranty program Warranty risks management Risk Management Project Planning

Risk Identification

Qualitative Risk Analysis

Quantitative Risk Analysis

Risk Response Planning

Risk Monitoring and Control

Warranty risks management Input Warranty program chart. Company’s risk management policies. Defined roles and responsibilities. Risk tolerances in the warranty program. Work breakdown structure for assistances. Plan for the risk management project Scope and objective of the warranty program Risk categories: -Technical or quality risks -Warranty management risks -Organizational / External risks -Historical information Plan for the risk management project List of identified risks Status of the warranty program and assumptions Product type / Data precision Plan for the risk management project List of identified and prioritized risks Historical information Expert technicians judgment Plan for the risk management project Risks ranking for the whole warranty program List of prioritized risks Probabilistic analysis of the warranty program List of potential responses Common risk causes in warranty assistances Trends in the results of the analysis Plan for the risk management project Response plan for warranty risks Program data and records Additional risk identification and analysis Scope changes

Output

Plan for the risk management project

List of identified risks Risks symptoms or warning signs Insufficient detail in the inputs of other steps Risks ranking for the whole warranty program List of prioritized risks Trends in the results of the qualitative analysis Prioritized list of quantified risks Probabilistic analysis of the warranty program Trends in the quantitative analysis results Response plan for warranty risks Residual risks Secondary risks Contractual agreements Contingency reserves Alternative strategies Revision to the warranty risk plan Work plans (for emerging risks) Corrective actions Changes request on the warranty program Update to the risk response plan Risk database for the warranty assistances

As shown in Figure 1, this process is continuous: monitoring and review, which consist in keeping track of the identified risks, monitoring residual risks and identifying new risks, ensuring the execution of risk response and mitigation plans and evaluating their effectiveness, is a fundamental part of the process. 3. CONTRACTUAL ASPECTS ON WARRANTY Once analyzed the risk management from a warranty perspective, it is time to briefly discuss about those legal aspects which link manufacturer and user (or seller and buyer), the possibility to contract warranty extensions and how they can be expressed by a legal document which encompasses the conditions for such extended assistances. In the literature, we observe that warranty is sometimes called as a “service contract”. However, there are some differences between both concepts [1]. Mainly, a service contract is purchased

separately, while warranty is part of the product purchase and integrated to the sale. Therefore, a warranty extension should be considered as a “service contract”, whose scope can be the same as the one for warranty or, on the contrary, it can include and/or exclude some different topics. In any case, this possibility should be taken into account in a very early stage of the product life cycle, during the pre-launch stage. Afterwards, during the warranty time (and normally close to the end of this period) the warranty extension will be agreed between buyer and seller and finally committed into effect, if both parts are interested to prolong or to contract this service. In legal terms, warranty and warranty extensions are concepts expressed through a contract between the parties for specific assurances, and applied to customers during a determined period of time (W+L, where W and L are the warranty and the extended warranty period, respectively). Such warranty can be given for purchased products or for services with a specific workmanlike quality. In the case of warranty extensions applied to a product, this contract can give different conditions of the technical service to be provided by the manufacturer, which are described in the fundamental terms of the contract.

SOME POLICIES

WARRANTY EXTENSION POLICY 1 Specified Parts Excluded

1. Rectification of specific com ponents at no cost over the extended w arranty period. 2. Rem aining item s to be borne by the buyer.

POLICY 2 Limit on Individual Costs

1. Claim s under w arranty are rectified. 2. If cost < a lim it, buyer pays nothing. 3. If cost > lim it, buyer pays the excess cost.

POLICY 3 Limit on Total Costs

Obligation ceases w hen com es first: 1. Total repair cost > a specified lim it or 2. End of the extended w arranty period.

Figure 2. Some possibilities for the Warranty Extension (Adapted from DNP Murthy et Al., 2006) These agreement clauses give consequently a legal obligation to the manufacturer in front of the buyer. Usually, there is an inherent understanding by the buyer about the warranty concept itself, which is independent of any written expression. In any case, the sold items and the products (or services) whose warranty has been extended must reasonably conform (or keep conforming) to an ordinary user's expectations, and the seller must be sure that the item is fit for that particular purpose. Those countries which have ratified the United Nations Convention on Contracts for the International Sale of Goods (CISG) find the obligation that, excepting when the parties have agreed otherwise, a seller must provide goods fit for their ordinary purpose [7]. Some possible policies on service contract extensions can be extracted from references [1,8]. Extended warranties are usually offered by major retailers and their organization, marketing, accountability and administration can be manage in different ways, involving different modules or departments inside the manufacturing company, as well as the retailers, and/or third parties [1,4]. In any case, Figure 2 tries to illustrate some possible policies to take into account at the moment of offering a contract for warranty extensions. 4. QUALITY FUNCTION DEPLOYMENT FOR THE IDENTIFICATION OF WARRANTY RISKS 4.1 Brief summary of QFD Quality function deployment (QFD) is a customer driven quality improvement method that aims to meet customer needs in a better way and enhance organizational capabilities [9]. More in details, QFD is designed to translate customer needs and expectations into engineering parameters, establishing a relationship between product developers and all stakeholders involved with the product’s life cycle. This method uses a combination of matrices, called “House of Quality” (HoQ), as a tool to investigate and evaluate the relationships between customers' needs and product design parameters explicitly. The HoQ is composed by two main matrices: the relationships matrix and the correlation matrix. The first tool allows engineers to carry out a semi-qualitative assessment of inter-relationships among WHATs (i.e. what customers desire/need), HOWs (i.e. how to satisfy customer needs/desires), and HOW-MUCHs (i.e. the metrics and

values of the customers' needs and requirements). The latter matrix is aimed at assessing the mutual influence that each WHAT can have on the other ones. A further evaluation can be carried out both by estimating the relative importance of each one of these parameters (i.e. HOWs, WHATs and HOWMUCHs), as well as by performing a benchmarking analysis taking into account customers’ and engineering perspectives. In Figure 3 the general framework of the method is represented. Starting from this framework, the QFD has been developed in different ways, according to the sector/context of application, so that it has been used not only in numerous industrial engineering fields but also in services [10].

Figure 3. General scheme of the House of Quality 4.2 QFD and Warranty Risk Considering that warranty management is a process through which customer satisfaction can be monitored (gathering information about claims and after-sale services) and, at the same time, positively or negatively influenced, it is clear the considerable importance that the identification of risks associated to its development. Main objective of the analysis is then the identification of critical aspects of a warranty program by customer’s perspective, with the aim to suggest areas in which risk analysis and evaluation is needed in order to plan appropriate treatment. On these considerations, the application of QFD, which, as already discussed, is focused on customer needs, seems preferable to the use of traditional tools, such as brainstorming, SWOT analysis, checklist and cause-effect diagrams. In fact, the application of QFD methodology guarantees a customer oriented approach to risk management. In particular, by translating customer needs and expectations into warranty management objectives and evaluating the warranty program compliance to these targets, risks are identified. As already discussed, warranty management is a process which concerns the whole life cycle of a product. Then, its deployment necessarily involves different functions inside the organization: design and development, production, logistics and marketing. According to the well-known five forces Porter’s model, warranty deployment can be considered as an entrance barrier for new potential competitors in the same product market. At the same time, some of warranty management principles, such as facilitate assembling/disassembling or use standard components, must be taken into account during the processes characteristics of mentioned functions, that is design, production, distribution and sale of products. In the definition of WHATs and HOWs in the HoQ these aspects were taken into account. The application of QFD to warranty risk management was carried out in two different stages. During the first one, the definition of customer needs and service design/management requirements was done considering the most general case, that is the warranty program of a generic product/service. Then, considering a specific case study, it was possible to prioritize organization’s response to customer needs and deeply analyze the most risky process related to warranty management. By doing so, a list of specific HOWs was pointed out in order to both identify risks associated to specific processes and suggest treatment for their reduction. In Figure 4 the framework of proposed method is shown, outlining inputs and output of each

phase of the risk identification process, which are discussed in the following paragraphs. Steps in dotted rectangles (risk analysis, risk evaluation and risk treatment) are subsequent to the application of proposed method, but are included in the pattern as some outputs of the identification process can be successfully used as inputs for these stages. Competitive benchmarking was not considered in the analysis due to difficulties in finding information about the characteristics of warranty management process in other organizations. Also the definition of the correlation matrix requires a deep knowledge of processes and procedure characteristic of an organization, so it has not been considered in the analysis.

Figure 4. Proposed method 4.3 General case To identify customer needs, warranty program was analyzed considering the whole life cycle of a product, from design until the end of warranty period. In particular, connection between organization’s functions (design, production, maintenance, logistics, marketing, etc.) and warranty management were outlined and declined into corresponding customer needs. The definition of “WHATs” was based also on after-sales data and customer satisfaction surveys coming from different industries. Factors were divided into three categories concerning warranty intervention, characteristics of the product and the contract. The result of this first step of the analysis is a list of customer needs which can be applied to almost all warranty management processes, with the intent to be a general pattern (see Figure 5 in the case study). According to the aim of the analysis, the service design/management requirements part in this case is filled with all those macroprocesses which directly, or indirectly, affect customer satisfaction during warranty period. At a general level, in fact, it is not possible to define those specific requirements that characterize each different situation. At the same time, it would be almost impossible, and perhaps even useless, to consider all those activities related to warranty assistance. Macro-processes were divided into the following classes (see Figure 5 in the case study): •

Design and development: at this stage it is possible to select the design alternative which improves warranty management performance by facilitating warranty repairs, reducing the risk of repairing errors and the time needed to perform the job.

• • • •

Production: during production activities the number of defective products can be reduced applying quality control strategies and training production personnel. Warranty repair: processes concerning preparation and execution of repairs during warranty period are crucial to perform a warranty service in the shortest time and with the highest level of quality. Logistics: most of delays in warranty assistance can be attributed to logistic issues, such as the selection of available suppliers and the allocation of spare-parts and service centers. Contract management: there are different customer needs concerning the warranty contract to which the organization must respond considering both mandatory requirements and competitors’ position.

Once customer needs and organization response, in terms of macro-process, are outlined, it is possible to create a relationship matrix. The definition of connections between WHATs and HOWs and their strength can be done only considering a specific case study, in which the characteristics of the product and its warranty program are outlined, making it possible to prioritize HOWs according to WHATs. The resulting relationship matrix, filled according to the features of the case study, is illustrated in the following section. 4.4 Case study The second step of QFD application was carried out examining the case of agricultural and gardening equipment. In this field, a large number of products are purchased and used by non-professional users so environmental factors may sensibly affect product’s reliability: only an efficient warranty management prevents from customer dissatisfaction in case of failures during warranty period. Information used to carry out the case study was provided by a manufacturer. In particular, the analysis is focused on a small farm tractor. The relationship matrix was filled considering the existence and strength of connections between customer needs and organization’s macro-processes. For example, considering speed and quality of a warranty service these needs are indirectly related to the design of the product, which can favor its maintenance or not, and directly dependent to technicians ability, and then to the training process and product’s logistics. Components standardization, easiness of assembling/disassembling, components traceability and proper training programs are requisites which must be taken into account when dealing with warranty management risks. The same criteria was used to define all the other relationships. Relative weights were defined according to manufacturer experience and information provided by customer satisfaction and after-sale service, and were attributed on a scale of five points. The strength of connection is evaluated according to the standard QFD practice, which supports the values 1, 3, and 9 to indicate a weak, medium and strong relationship respectively (Table 2). According to the analysis, the Design & Development category resulted the most critical, followed by the Warranty Repair one. Considering the complexity of a farm tractor and its high number of different components, the inclusion of warranty principles during the design phase seems particularly important to improve warranty management performance. For this reason, the study was focused on the definition of risks associated to the Design & Development category. During design activities technical characteristics of a product are defined; decisions taken at this stage sensibly influence product reliability and easiness of repair. In order to reduce both risks of failures during warranty period and delays in warranty repairs, it is essential to identify specific HOWs to respond to customer needs like “fast intervention and service” (immediacy factor) and “maintainability of product” [11]. A detailed analysis allowed to understand how an organization, operating in this field, could respond to customer needs, outlining specific HOWs to be considered for this category (Table 3). With regard to assembling/disassembling design, there exists numerous strategy to improve product performance in this field. In particular, considering gardening equipment, the use of the well-known Design for Assembly method [12] seems particularly appropriate. The criticality analysis can be carried out using FMEA (Failure Modes Effects and Criticality Analysis) and FTA (Fault Tree Analysis) with the aim to prevent failures during warranty period by adopting alternative design solutions or mitigate their negative effect to the customer by planning an efficient warranty program. As far as testing is concerned, besides commonly used test for this type of product (unbalancing, blades integrity, etc.), by a warranty perspective important analysis can be: broad band vibration analysis, shock pulse monitoring, proximity analysis, real time analysis, ultrasonic and fiber loop thermometry. Traceability can be obtained by adopting specific coding systems and RFID (Radio Frequency IDentification) for components and assemblies to improve spare parts management, thus facilitating warranty repairs and logistics. With the same objective, standardization is increased by the use of a Variety Reduction Program [13]. Even if risk analysis and evaluation were not carried out, the identification of risk sources, risky processes and specific HOWs allowed to suggest design improvements to mitigate warranty management risks. In particular a FMEA (Table 4) of the system revealed that the most

critical components of the product are located in the cutting system (e.g. belt, blades and clutch). Then, during the warranty program, these components are likely to fail. In order to reduce time spent for disassembling/assembling during warranty assistance, complying with customer needs, the use of Design for assembly is suggested. This method is based on the evaluation of the Design for Assembly (DFA) index, which is determined comparing the time spent for assembling an analyzed product with the one needed to assemble the ideal product, characterized by the minimum time. Table 2. QFD for the identification of warranty risks

3 3

3

1

5 2 3 2

9

9

9

3

1 3

9 9 9

WEIGHTS 9 9 3 9 3 3

9 9 3

1

1

1

9

3

3

9

3

9 9

1 3

9 9

3

3

3

3

1

3

9

3

9 3

9 3

3 9

9

3

9

3

9

9 3

3

3

Customers’ groups identification

3

Warranty extensions possibilities

Outsourcing management

Service center/Warehouse allocation

Spare parts allocation

Selection of suppliers

Outsourcing management

Call-center service management

Diagnostics (software)

Tools and instruments management

Data collecting/analyzing

Definition of standard job

Training (warranty personnel)

Training (production personnel)

Measurement management

End products quality control

Process quality control

Standardization of components

Traceability of components

1 1

Market analysis

9 3

CONTRACT MANAG.

Compliance management

5 4 3 2

Testing and prototyping

Criticality analysis of components

Assembling/Disassembling design CUSTOMER NEEDS

Intervention Fast intervention and service Quality of intervention Short distance to service center Service center availability Product Maintainability of product User guide clearness Possibility of online diagnostic and trouble shooting Availability of spare parts Contract Compliance to laws Warranty contract intelligibility Long warranty period High number of components covered by warranty

Materials quality control

REQUIREMENTS (MACRO-PROCESSES) PRODUCTION WARRANTY REPAIR LOGISTICS

DESIGN & DEVELOPMENT

3

9

9

3

3

2 9 9 3 3 9 9 9 3 3 3 4 9 9 3 3 9 3 1 9 9 3 3 1 3 3 3 1 9 3 1 Importance 138 146 117 62 186 35 35 101 45 15 114 72 62 17 120 21 51 69 45 66 57 40 69 45 30 649 231 457 237 184

Table 3. Identification of specific HOWs CUSTOMER NEEDS

HOWs

Fast intervention and service Quality of intervention Maintainability of product

Assembling/Disassembling design

RISKY EVENTS Long time to repair/deliver

RISKS Damage to firm reputation

Defective repair

High warranty repair costs

Saturation of service centers

SPECIFIC HOWs

Design for Assembling strategies

Online diagnostic Service center availability Availability of spare parts

High number of claims

Design/modification costs

Quality of intervention

Product recall

Damage to firm reputation

Maintainability of product Long warranty period

Criticality analysis of components

FMECA and FTA

Compliance to laws High number of components covered Maintainability of product

Nonconformance

Costs for dispute resolution

Compliance to laws

High number of claims

High warranty repair costs

Long warranty period

Testing and prototyping

Product recall

High number of components covered Quality of intervention Availability of spare parts

Traceability of components

Online diagnostic

Missing spare parts

High warranty logistics costs

Defective repair

High warranty repair costs

RFID

Long time to repair/deliver

Availability of spare parts Quality of intervention Maintainability of product

Design/modification costs Damage to firm reputation

Broad band vibration analysis Ultrasonic Proximity analysis Real time analysis

Standardization of components

Long time to repair/deliver

High warranty logistics costs

Defective repair High number of spare parts

Damage to firm reputation High warranty repair costs

Variety Reduction Program

All values are calculated using specific tables provided by the method. In Table 5 the DFA index for the farm tractor taken into consideration is shown. The reduction of the number of components, obtained by the

integration of different parts (blade and its flange support) and the elimination of screws by changing support design, has a positive effect with an increase of DFA index till 0,56. In conclusion, by a warranty management point of view, the adoption of these design modifications could reduce repairing times and the number of spare parts which must be managed, making the warranty program more efficient and reducing risks associated to customer dissatisfaction. Table 4. Excerpt of FMEA Failure Mode

Description

O

S

D

RPN

No cutting

Belt wear

4

8

5

160

Clutch failure

3

8

7

168

Blades breakdown

2

8

10

160

Pulley mulfunctioning

1

9

10

90

Motor failure

1

9

3

27

Pump failure

1

8

2

16

5

6

4

120

4

6

2

48

3

5

10

150

Intermittent cutting Lose belt Insufficient lubricating Insufficient cutting Regulation mechanism failure

HT= Handling Time

Insertion code

IT=Insertion Time

TA=[RPx(HT+IT)]

1 2 1 4 4 6 2 2 2 6 2

30 35 30 0 11 11 30 10 10 11 30

1,95 2,73 1,95 1,13 1,8 1,8 1,95 1,5 1,5 1,8 1,95

0 2 1 2 39 39 22 2 12 39 22

1,5 2,5 2,5 2,5 8 8 6,5 2,5 5 8 6,5

3,45 10,46 4,45 14,52 39,2 58,8 16,9 8 13 58,8 16,9 244,48

Nmin= Minimum number of comp. (1 necessary, 0 eliminable)

Handling code

1 2 3 4 5 6 7 8 9 10 11 TOT.

RP=N° of components

ID number

Table 5. Application of Design for assembly method

1 1 0 1 1 1 0 1 1 1 1

Cutting system Cutting plate Blade Grass collector Wheel Wheel clamp Screw (blades) Flange support Shaft Bearing Screw (shaft) Shaft support DFA Index ((3xNmin)/TA)

0,36

5. CONCLUSION Many manufacturing companies spend great amounts of money just due to their product and service warranties. However, most of the cases this reason does not receive more attention. Today, effective warranty management processes are not yet on the main decisions of most executives. In practice, companies

often pay attention to their warranty management processes only when high levels of liability are involved with a claim or recall. As a consequence, they are missing opportunities for significant cost savings, as well as for increasing the business value through better-quality products and higher levels of customer satisfaction. By the use of specific tools for warranty risks identification, such as proposed one, organizations may reach this goal. A better knowledge of warranty risks gives the opportunity to reduce the gap between service offered and customer expectations. Despite the application of proposed method to different products and its extension to risk analysis and evaluation, further research on this field can be for instance the perception of warranty risks in other markets, mainly emerging countries, and the interaction between such markets with the developed countries, since the first ones usually are manufacturers and the second ones usually are users or consumers. Acknowledgements The authors would like to thank the work of the reviewers for their contribution to the quality of this paper. Part of this research is funded by the Spanish Ministry of Science and Innovation, Project EMAINSYS (DPI2011-22806) “Sistemas Inteligentes de Mantenimiento. Procesos emergentes de E-maintenance parala Sostenibilidad de los Sistemas de Producción, besides FEDER funds. References [1] [2] [3] [4]

[5]

[6] [7] [8] [9] [10] [11]

[12] [13]

Murthy DNP Blischke W. R..Warranty management and product manufacture. Springer-Verlag London Limited, 2006. Hongzhou Wang. Warranty Cost Models Considering Imperfect Repair and Preventive Maintenance. Bell Labs Technical Journal 11(3), 147–159, 2006. Lawless J.F. Statistical analysis of product warranty data, International Statistical Review, 66, 41-60. 1998. González V., Gómez J.F., López M., Crespo A., Moreu de León P. Warranty cost models State-of-Art: A practical review to the framework of warranty cost management. Safety and Reliability for Managing Risk. London, UK. Taylor & Francis. (ESREL 2009, Prague), 2051-2059, 2009. Ghodrati B., Akersten P.-A., Kumar U. Spare parts estimation and risk assessment conducted at Choghart Iron Ore Mine: A case study. Journal of Quality in Maintenance Engineering. Volume: 13, Issue: 4, 353 – 363, 2007. Backlund F., Hannu J. Can we make maintenance decisions on risk analysis results?. Journal of Quality in Maintenance Engineering,. Volume: 8, Issue: 1, 77 – 91, 2002. United Nations Convention, Contracts for the International Sale of Goods (Chapter II, Obligation of the seller), 1980. Padmanabhan, V., Usage heterogeneity and extended warranties, Journal of Economics and Management Strategy 4, 33–53, 1995. Akao, Y. Quality Function Deployment, Productivity Press, Cambridge, Massachusetts, 1990. Chan L.-K., Wu M.-L. A systematic approach to quality function deployment with afull illustrative example, Omega 33, 119 – 139, 2005. Moreu P., González-Prida V., Barberá L., Crespo A.. A practical method for the maintainability assessment in industrial devices using indicators and specific attributes. Reliability Engineering and System Safety, doi: 10.1016/j.ress. 2011.12.018, 2012. Boothroyd G., Dewhurst P., Knight W.A., Product design for manufacture and assembly, III edizione, CRC Press, USA, 2010. Kōdate A., Suzue T., Variety Reduction Program, ISEDI, Torino 1992.