Responsible Management, Inc.
The number of practitioners who go beyond re-mapping customer information into engineering information by using the House of Quality matrix is slowly increasing. However, few try function analysis, reliability deployment or use the negative feedback of the gemba. This paper presents the integration of failure modes and function analysis to identify breakthrough development concepts. Reduction in the failure modes and increases in reliability are natural consequences. AHP ranks the design concepts using the priorities from the House of Quality. The driving forces are the ideal final result taken from TRIZ as defined by the function tree and failures as deployed from the House of Quality.
A1 Matrix, Failure Deployment, Function Analysis, Function Tree, Function Deployment, House of Quality, Ideality, Innovation, Problem Formulation, QFD, Quality Function Deployment, Reliability, Systematic Innovation, Theory of Inventive Problem Solving, TIPS, TRIZ, Useful Function, Voice of Customer Table.
The owners of a new startup company, Green Lite, used the following material to design an environmentally friendly back packer's flashlight. The owners we excited about integrating QFD, TRIZ and Taguchi into their design process.
Comprehensive QFD has not become a household word yet. Richard Zultner's10 introduction to Blitz QFD has sensitized the
QFD community that there is more to QFD than the re-mapping of the voice of the customer into performance measures. In an attempt to keep the effort upwardly compatible he uses the critical few performance measures (the columns in the House of Quality), functions, failures, etc., as driven by the most important customer demanded qualities.
A recent conversation with a manager of the Product Development Roundtable, which is a division of The Management Roundtable, helped me to clarify the central message from their past participants. The message was that QFD takes too long and cost too much. Design cycle time is getting shorter and shorter and corporate resources are being reduced. Therefore, they cannot apply QFD.
The following paper is not one-minute QFD. There are organizations both small and large which include a thorough QFD analysis as part of their design process.
At last year's symposium the synergy between QFD, TRIZ and Taguchi was presented in The QFD, TRIZ and Taguchi Connection: Customer-Driven Robust Innovation.
In 1992, Glen Mazur and I developed the first comprehensive QFD case for a flashlight. It is relevant to revisit that case as a way to share the effort of the startup company and it's use of QFD and associated tools. The details of the calculations are not presented because they are a distraction from the main theme of this particular presentation.
House of Quality
The input for the House of Quality are gathered by defining the customer segments, going to the Gemba, and using AHP with the affinity diagram. After talking with two other small organizations, the owners of our flashlight company identified an unexpected customer segment that had been missing, large corporations protecting their own interests. This identification was prompted by observation of what happened in the two other industries. In one instance, a company was preparing to offer packaged water in a plastic alternative. This company had identified chemicals, believed to be triggers for cell growth, that leach from plastic tubing used to carry water. The connection between the leaching chemicals and uncontrolled cell growth originated from cancer research work that had been seriously compromised solely through the use of water that had passed through off-the-shelf plastic tubing. This water company was put out of business by industrial sabotage. In the second example, organic farmers are concerned about the trend in federal legislation toward expensive organic farm registration. The definition for "organic" includes crops that have been irradiated, fertilized with sewer sludge, and employ gene splicing. Corporate America, with its eye on the rapidly growing organic produce market, is driving the discussions in Washington. In an effort to create a proactive response to existing corporations that may dominate an industry, Green Lite has added the concerns of their larger competitors as a customer segment that must be considered.
Figure 1 shows the main points of the House of Quality. A subset of the demanded qualities (DQ) and the performance measures (PM) are shown. Not shown are the target values, technical and customer bench-marking, as well as the other rows and columns which are in the House of Quality. Also not shown are the corporate requirements, which includes:
- 100% recyclable design
- Environmentally friendly manufacturing process.
Everybody gets this far, but often does not have a clear idea as to how to fill in the relationship cells. We asked the following question for each intersection of row and column, "If I tell you the score for the performance measure (column, Volume), how good a prediction will it be of the customers satisfaction of the demanded quality (row, Easy to carry)?" The answer was weak (a triangle). The question must always be directed from the column to the row.
Green Lite would like to understand the functions (F) of the product before developing concepts. Since the performance measures can be viewed as measures of performing functions, they are convenient sources for identifying functions. Lumens at 10 meters and the Effort to adjust are the two most important performance measures (PM). These priorities are actually a smoke screen for the real numbers. Focusing on these priorities perpetuates a mistake commonly made by doing the calculations and not remembering the purpose of doing the analysis.
The priority should be the integration of the calculation shown plus information contained in technical benchmarking, the gap between current performance and future goals, corporate strategy and core competencies. This last constraint represents a common source of resistance to breakthrough thinking. For organizations which use composite weights for the rows, these issues are not as critical.
Figure 2 shows the resulting matrix of performance measures mapped into functions. The question asked to fill in the intersection of rows and columns was: "If we provide the function (column, Aim light) how much of an impact will it have upon the performance measure (row, Effort to adjust)?" We believed that the effect would be medium and entered an open circle.
Shillito and DeMarle3 present Dysfunction Analysis as a means to design. It explains the evolution of a design from the initial component and all of its associated problems. Design modifications correct all the difficulties but cause secondary problems. The process continues until a working design is found. It is an intriguing process.
The more classical approach using the FAST system starts with the customer's desired function, which is mapped into the designing organization's functions. These functions include the primary, secondary and design concept functions. The function tree is constructed by repeated answers to the questions: "What you want to accomplish?" followed by "How you will accomplish it?" used to construct a function tree. The last branches are components or subsystems. The function tree shown is figure 3 used some of the functions from figure 2. Obviously, a complete function tree should include all functions mapped from all the performance measures plus functions not of concern to the user. The shaded function blocks track the primary function and the dotted lines are for the rest of the tree.
One of the premises of TRIZ is the concept of the Ideal Design. The Ideal Design provides all the required functions without the physical existence of any system. To accomplish this, the design typically takes advantage of free resources, such as gravity, or effects such a shape memory. The measure of Ideality is the ratio of the benefits to the costs and harms.
The benefits are generic for useful functions and any other desired event or outcome. The costs should include the direct costs and the costs to society that Dr. Genichi Taguchi often talks about. The harms should include failure modes, harmful functions and any other undesired event or outcome.
The denominator offers additional directions for failure modes analysis. Instead of mapping the functions into failure modes, this broader perspective was used to map the functions into all the non-value-added issues in the denominator of the Ideality equation.
Failure Modes Plus
This approach is shown in figure 4.The question asked to fill in the intersection of rows and columns was, "If this failure or event occurs (column, Distortion), how much of an impact will it have on the performance of the function (row, Focuses light)?" In this case, it was medium (an open circle). Not all the columns have entries. The reasons are the reduction in the set of DQs and the lack of corporate requirements for a very GREEN product design.
Clearly, distortion and the light bulb braking are major concerns. These could be the inputs to design and process FMEAs. These failures could be the result of poor design or process problems. Instead, the functions and the failures were used to structure the linked network for the problem formulation process.
A third approach to working with functions is to describe the existing system with all of its benefits (useful functions) and harms (harmful functions). The Problem Formulation process developed by Boris Zlotin and Alla Zusman identifies directions in which to drive the design process by the creation of an exhaustive set of problem statements. In this application, weights associated with the functions and harms have been added to aid with the ranking of the problem statements and associated solution concepts. This requires using AHP to weight failures and harmful effect caused by inputs other than the demanded qualities.
For the flashlight, the primary useful function (PUF) is to illuminate things. Starting with the PUF, we ask the questions, "Are there any harmful consequences (HF)?" and "Is another useful function required?" Radiate light is required to Illuminate things.
The generic questions for each useful function (UF) are:
For every "yes", at least one new node is created. Questions for harmful functions are:
A simplified linked network for the flashlight is shown above, in figure 5. The resulting 29 problem statements are given at the end of the text. Circular nodes represent the useful functions and rectangular nodes represent the harmful functions.
Each cell in figure 5 represents at least two problem statements. The problem statement syntax is the result generated by computer analysis. The closer the cell is to the PUF, the more significant the change in the design. Looking at problem statement 1, we have:
1. Find an alternative way to provide ((1) Illuminates things), which doesn't require ((2) Radiate light). The numbers within the
parentheses are the cell numbers. This statement leads to several radical design changes, such as:
Consider variation on heat sensing binoculars
Instead of light from the user, excite the object to make it glow.
It is important to view the problem statements very flexibly because their purpose is to stimulate directions for brainstorming. Statement 8 is a good example:
8. Find an alternative way to provide ((3) Convert Energy), which provides or enhances ((2) Radiate light), but doesn't cause ((11) Contacts corrode), and doesn't require ((4) Stored energy).
Convert energy could be from physical effort, such a palm hand-pump that turns a small flywheel connected to a small electric generator. There are at least two added benefits with this design. The person using the flashlight gets warm in the winter and the source of energy will not be compromised by cold weather.
This type of a design change eliminates corrosion failure, thereby improving reliability. However it introduces two secondary problems: (1) hand is busy, and (2) the flashlight is not self-supporting. These secondary problems may be more difficult to solve than the primary problem.
Other possibilities are the Energy Storage emits the light, as in some emergency kits.
Number 28 offers an inexpensive design change.
28. Find a way to eliminate, reduce or prevent ((12) Loss of night vision), under the condition of ((2) Radiate light).
Analogic thinking links this problem with shipboard vision. Instead of white lights, red lights are used below deck during the evening so as not to reduce night vision. A simple slide of red Mylar will work.
The predominant failure is highlighted in problem statements 8, 11, 26 and 27. Looking at physical effects may be the best source of ideas. One convenient source of effects, Invention Machine's software, offers this possibility:
"Corrosion Rate Is Retarded
After short-term irradiation of metal by alpha particles, most particles remain in the thin surface layer causing a change in its properties, in particular, corrosion resistance of the metal increases. For instance, the surface of a metal plate treated with alpha particles retains its original structure and luster after being exposed to the action of concentrated hydrochloric or sulfuric acid. This effect is explained by the restructuring of the surface layer and the removal of aqueous vapor." Copyright © 1997 Invention Machine
This effect offers a practical approach to the reduction of failure and increase in reliability.
This same process is continued until all the design considerations have been resolved.
The ideal flashlight design illuminates things without existing. Looking at effects again, but this time in Ideation International's software, we find that, "Ordinary light bulbs emit 80 percent of their energy as invisible infrared radiation. To increase lighting efficiency, investigators at MIT coated a light bulb with a thin layer of silver, sandwiched between two layers of titanium dioxide. This coating is transparent to visible radiation, but it reflects infrared heat rays. The curvature of the bulb is adjusted so the reflected heat is focused on the bulbs filament. Less electricity is then needed to produce the same amount of visible light." Copyright © 1996,1997 Ideation International, Inc.
In another approach to creating the ideal flashlight, focusing could use an effect rather than a mechanical effort. Focal length in optical systems is usually mechanically adjusted by moving lenses and other system elements. This is a time-consuming process. "More rapid adjustment can be made in a system that uses Kerr-effect optical elements. The refraction index of such elements can be adjusted by changing the intensity of an applied electric field. For example, a cylindrical Kerr-effect element is placed inside a capacitor, the position of the focal point (for parallel rays passing through the cylinder) can be moved by changing the voltage across the capacitor." Copyright © 1996,1997 Ideation International, Inc.
These concepts all lead in the direction of a more ideal design. The concepts are ranked using AHP with criteria from QFD and corporate issues. Personally, I like the pump idea, because it also provides exercise for my arm.
Once again, the power of integrating tools from other disciplines for comprehensive QFD has been demonstrated.
A flow was presented starting with the demanded qualities of the customer for a flashlight. The demanded qualities and their associated importance rankings were translated (re-mapped) into performance measures. Performance measures lead to functions and failures.
The problem formulation process associated with TRIZ (Terninko, Zusman and Zlotin) was used to integrate the failures and functions to create problem statements.
The problem statements lead to concepts with were ranked using AHP based upon the performances measures and importance in the output of the House of Quality and the reliability issues defined by the failure modes.
Conclusions and Recommendations
Comprehensive QFD is worth the effort. Having an audit trail from the customer to design decisions helps both current and future design teams.
Applying QFD as the input to systematic innovation (TRIZ) should be useful to organizations interested in becoming world class competitors.
Additionally, the QFD Institute and some universities should use the patterns of evolution from TRIZ to identify and implement future QFD process. Perhaps, this is where we will take up this topic next year!
Exhaustive set of problem statements
Terninko, John, QFD Assumes You Have an Imagination, The Transactions of The Third Symposium on Quality Function Deployment, June 24-25 1991, Novi, MI: ASI and GOAL/QPC
Dr. John Terninko
John has taught QFD and Taguchi philosophy to corporations in North America, Central America and Europe for 14 years. He is a recipient of the 1985 Taguchi Award for promotion and application. He has integrated his diverse experience base (electrical engineering, operations research, organizational development, teaching, and management consultation) to develop an approach to the problem solving required for QFD and utilizing the synergy with Taguchi's philosophy. In 1995 he began integrating TRIZ into QFD.
John is a principal with Responsible Management Inc., cofounder and director of the QFD Institute, cofounder and director of the QFD Network