ENV model to define Primary Function. 

Contexts in source publication

Context 1

... for the integration of quality tools is presented. QFD and FMEA are both effective tools utilized in the course of product development, however there are potential limitations if they are used separately. As they possess the characteristic of sharing the bottom database in an integrated quality management system, their integration may solve this issue. Based on an elaborate analysis of advantages and disadvantages of QFD and FMEA, [9] proposes an integration model which four kinds of FMEA are incorporated into the four phase model of QFD. There exist also several cross fertilization examples of FMEA and others technique outside reliability and quality context. In [10] a new approach is proposed to enhance FMEA capabilities through its integration with Kano model. In the designers’ point of view, not from the customers’ side. Th is evolves the current approaches for determination of severity and “risk priority number” (RPN) through classifying severities according to customers’ perceptions . Some efforts have been done also to merge more than two methods as shown in [11] where FMEA, QFD and TRIZ are the ingredients of a product development process. TRIZ is the most comprehensive systematic innovation and creativity methodology ever developed. Its main goal is to solve unconventional problems and to forecast technologies and future products, but it also provides a method to face reliability issues. By means of the Subversion Analysis concept TRIZ can help in those situations where an unexpected problem has occurred, and where we don’t know the source or cause of the pro blem. Subversion Analysis [12] also implemented as Anticipatory Failure Determination AFD [13] has several parallels with established methods like FMEA, HAZOP, or fault-tree analysis. The main difference is that it forces users to take a much more proactive approach to finding causes of problems. As a consequence, systems designed with this approach are less vulnerable to unpredicted failures. The logic of Subversion Analysis relies on finding all the ways to destroy the system we are designing. After this task we can much more easily design the system so that those modes of failure are eliminated or, at least, taken into account when implementing corrective actions. Subversion Analysis is about inventing failures. In this sense it has simply capsized the inventive problem solving: if we can invent a failure then we can use other TRIZ tools to eliminate it. Subversion Analysis is typically carried out as a systematic process. The key steps in the process involve the two inversions of the problem; firstly to allow us to ‘invent the failure’ (how would I design a system that failed in the way my system actually has), and then to re-transform the invented failure into a means of preventing the failure in the future. Main steps of a generic Subversion Analysis process are: 1) Problem definition; 2) Formulation of inverted problem; 3) Define function; 4) Identify failure modes; 5) Describe effect; 6) Determine cause; 7) Identify failure hypothesis; 8) Search for solution. In the followings Subversion analysis basic logic will be used and inversion of the problem will be performed, by the way the paradigm will not follow classical TRIZ way of performing failure determination. This paragraph shows the new paradigm developed to manage the risk of product failure or malfunctioning. The underlying philosophy corresponds to the Design FMEA logic of defining failure modes evaluating criticalities and risks. By the way some new steps are introduced to bring benefits to the whole process. The procedure starts with a general understanding of system functionality. This is not trivial and avoids bad understanding and misleading formulation of the real design intent. The procedure maintains the bottom up logic of FMEA and system is analysed starting from its components and their negative effects. Basic modelling tools are introduced to improve system understanding and to gather a better list of potential malfunctioning without involving several experts. The evaluation is performed in order to ease as much as possible the following step of problem solving with the goal of reduce or eliminate product weakness. In the followings each step is shortly described and then the whole procedure will be applied to a case study to show a real application. The use of Energy Material Signal (EMS) [14] and Element Name Value (ENV) [15] models to the whole technical system helps defining its overall primary function that otherwise could be misunderstood. EMS model suggest assessing the variation in the flux of energy, material and signal/information in order to determine what the system really stands for. EMS provides a clear description of any kind of technical system without the need of going into details. ENV model describes the system by means of its capability to change the Value of one or more Features of the Element, turning it from Object to the desired Product (Figure 1). After defining the Primary Function the technical system is divided into elements being either components of the technical system, elements of the super system or fields, according to a standard multiscreen resource analysis. Initially, the element list is built taking into account every single element not to miss the chance of finding all failure modes. In the following steps some elements will not be considered any more in order to speed up the analysis. Once elements are defined for each of them a list of effect is created by experts of the product development process. Since our final goal is building a set of failure modes, negative effects must be considered as well (Figure 2). Once elements (including fields) and related effects are completely defined it is required to assess product risk according to FMEA criteria. This means that all potential failure modes must be identified. ENV model is used again but now focusing on each single element describing the effects in terms of features and values of each feature. At first, to describe the design intent, nominal (design) values are considered, afterwards values are decrease and increased to extreme values and emerging conditions are analysed as potential failure modes (Table 1). In this step, according to FMEA tables [16] the severity of damage produced by each failure mode, the probability of its occurrence and the ease of detection must be considered and assessed on a 0-10 scale. Starting from the most critical elements (i.e. those associated with the most critical effects) the failure modes are evaluated and Risk Priority Number (RPN) is calculated. In this step the substance-field model of each critical situation is built, according to subversion analysis logic, in order to create the ‘machine’ to make the product fail. Standard solutions, mostly of class 1, must be us ed to complete the harmful machine and resource analysis play a key role to bring an abstract solution back to reality level. Finally, when all critical situations have been drawn and boosted up by means of subversion analysis, the functions created to destroy the technical system are considered as negative (see Figure 3). Thus a reliability issue has been switched into a problem solving task that can be run by means of classical TRIZ problem solving tools, e.g. standard solutions. The procedure described so far has been tested on several case studies on household appliances. Students of the last year of course of both mechanical and managerial engineering with basic knowledge on TRIZ fundamentals were asked to perform a risk management analysis task using the new procedure. The results obtained were examined to fix some problems in the procedure and refine it. In the following the application on a domestic hairdryer (Figure 4) of the new FMEA-TRIZ procedure is described to provide an example of a real application. According to the EMS formulation (Figure 5) the hairdryer has the goal to transform still cold air into a rapid and hot air flow. According to the ENV model and with a wider perspective the tool of the system is the hot air flow, the Element is the hair, features are humidity and shape, which can assume respectively values wet and dry, and unshaped and combed (Table 2). Thus the functions performed by the hairdryer are to dry hair and to shape it. In this step elements of the system are defined and listed. Mental inertia would bring the analyst to consider only material resources or the bill of material of the system. Resource checklist and multiscreen approach can be used to be sure not to forget elements that may play a key role in a failure mode. For instance, the design operating temperature or the average operating time are information resources; the way electrical energy enters the system and is transformed by different components into mechanical and thermal is an energy resource. Table 3 shows a partial list of elements taken into consideration for the analysis. After element list is complete and validated for each element all negative effects are listed. A fragment of the result obtained is reported in Table 4. In this step failure modes are determined starting from negative effects of the elements listed before. Moving values of features from an extreme value to the opposite one is quite easy to define a set of potential malfunctioning even without being product experts. Students split into small groups were able to perform such a critical task providing almost the same results. A small part of the spreadsheet is shown in Table 5. According to normal FMEA procedure Severity, Occurrence and Detectability are evaluated and 0 to 10 marks are assigned to each failure mode by means of referring tables [16]. The Risk Priority Number and Criticality is then calculated, as shown in Table 5. Engine results to be one of the most critical components since several failures with high RPN have been identified. Thus, we started the analysis from it and in the ...

Context 2

... provides a clear description of any kind of technical system without the need of going into details. ENV model describes the system by means of its capability to change the Value of one or more Features of the Element, turning it from Object to the desired Product (Figure 1). ...