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Tuesday, May 31, 2011

A Brief Summary of QFD

7.6 Summary
Quality Function Deployment (QFD) is a systematic process for translating customer requirements into appropriate company requirements at each stage from research and product development to engineering and manufacturing to market/sales and distribution. QFD is a complement to the System Engineering process. The principles of system engineering using QFD span the entire life cycle of a product.  QFD is not a quality tool to audit functional organizations, but is a structured planning tool to guide and direct the product development process.
·         Is a systematic means of ensuring that the demands of the customer and the market place are accurately translated into products and/or services.  
·         Provides both a planning tool and a process methodology in a structured approach.  
·         Identifies the most important product characteristics.    
·         Provides a comprehensive tracking tool and communication medium when applied to all stages of product development.   
·         Applies a cross functional team approach combining information and expertise from marketing, sales, design engineering and manufacturing.
The QFD process leads the participants through a detailed thought process, pictorially documenting their work. The graphic and integrated thinking that results leads to the preservation of technical knowledge; minimizing the knowledge loss from retirements or other organizational changes. This use of QFD helps transfer knowledge to new employees, starting them higher on the learning curve. The use of QFD charts results in a large amount of knowledge captured and accumulated in one place. The charts provide an audit trail of the decisions made by the project team. Once a QFD project has been completed, the resulting charts may be used as a starting point for future versions, (a “re-engineering starting point”) for similar products.
Again, QFD is a method; it is not a panacea, it must be done correctly and it takes up front time and resources to get the best possible results.

Wednesday, May 18, 2011

Other Specialty Matrices Used in QFD

7.5 Other Specialty Matrices
As previously stated, there are several approaches to QFD; each of these approaches makes use of matrices to organize and relate pieces of data to each other. There are typically four basic QFD matrices for Product Development.  The basic structure of these matrices relates WHAT’s to HOW’s for each of the four product development stages.  Since one of the objectives for System Engineering is to understand and determine relationships at all stages, there are other WHAT vs. HOW relationships that are important. Two “Specialty Matrices” that are important in front end system development are: 1) Preplanning Matrix and 2) Functional Architecture of the system (the WHAT’s) versus the structure of the Product Design, (the HOW’s)

7.5.1 Pre-Planning Matrix (PPM) - A Pre-Planning Matrix (PPM) is sometimes used in the product planning phase prior to launching Product Development.  The PPM provides an assessment of current company capabilities versus the expected competition. The assessment is taken from where you believe the Customer rates your capabilities and your competition.  The assessment identifies current strengths and weakness and shows where investment is needed to create a better competitive position prior to entering into the pursuit and/or development of a product.  It also provides a method of identifying potential teaming, strategic partnerships and/or alliances to strengthen product development and improve competitive position. The PPM provides a means for prioritizing investments that might be needed to become competitive and increase the probability of win or sale.
The PPM also identifies potential Sales Points.  A Sale Point is where current capabilities or the combined capabilities of a team provide a leading competitive position.  The Sales Point is used to communicate with customer(s) and to emphasize why a team or product is superior to its competitors.
The PPM consists of the following sections; 1) Voice of Customer (VOC) requirements, 2) An order of importance of VOC, 3) Competitive Assessment, 4) Identification of probable Sales Points, 5) Improvement Factor of VOC, 6) A new weighted VOC,
Figure 7-18 illustrates a partial sample of a PPM.  In reviewing the matrix Section A in Figure 7-18 lists each VOC requirements followed by a column that rates importance level of VOC on a scale of 1 to 5, with 1 rating being least important and a 5 rating being most important.  Section B in Figure 7-18 provides an assessment of the competition and your current capability through the eyes of your customer for your company and each competitor, followed by an identification of probable Sales Points.

Figure 7-18 The initial PPM is constructed to show current competitive position and identify Sales Points.

The PPM as constructed so far shows that our present competitive assessment indicates that Company B has a better competitive position.  The PPM also indicates that Our Company presently has two Sales Points to emphasize; that our product is Easier to Use and Easier to Hold versus competitor Company A and Company B.
Since the PPM from Figure 7-18 indicates that Company B has a better expected competitive position than Our Company for the defined VOC and Importance Rating, something must be done by Our Company to better the competitive position.  Figure 7-19 illustrates a further expansion of the PPM to include additional sections.  Section C includes Our Company Plan to increase capability in the “eyes of the Customer”.  The column marked Our Target Position the improvements needed to increase the probability of convincing the Customer that Our Company has a better capability and therefore provides a more favorable chance of winning the Customer’s approval.  However to achieve that Target Position Our Company needs to improve in two areas of the Customer’s view of our capabilities; 1) Waterproof and 2) Light Weight.  Light Weight has an Importance Rating of 5 and it requires an improvement of 9:1 from our current position, Our Company gives this a top priority action, (Priority #1).  The final column provides for a summary of Our Company’s Strategy to go forward to capture the customer’s approval.  Accomplishing this development and partnering effort should provide Our Company with a strong competitive position over Company B, (i.e. a Relative Importance Rating of 162 versus Company B’s 101 rating).

Figure 7-19 Adding Section C to the PPM provides a prioritized strategy to improved competitive position.

The PPM as presented assumes that Company A and Company B do nothing to improve their competitive position, but in reality that is not likely to be the case.  A further extension of the PPM is to forecast where Our Company thinks Company A and Company B might make improvements.  For example if Company A and Company B were to establish a Strategic Alliance and combine their capabilities then the best of each company capability would result in a Relative Importance Rating of 125, which is still lower than our anticipated improved rating of 162.  This assumes that Our Company is able to implement the identified strategy and investments and convenience the Customer of its improved capabilities.
There are other methods for the development of the PPM instead of the non-linear ratings used in Figure 7-19.  For example instead of the non-linear symbols a numerical rating of 1 to 5 can be used to assess Our Company and Company A and B’s capability.  However the overall benefit of the PPM is the process of walking through the questions and assessment needed to establish a company’s competitive position and provide priority and direction for further investment in development and/or teaming with another company.
It must be noted that other than identifying and emphasizing current Sales Points, nothing is attributed to the Relative Importance Rating for having these Sales Points over the competition.  Some PPM methods assign a value of 1.5 for each Sales Point and multiply the VOC item by 1.5.  If that had been done in this example the first Relative Importance Rating for Our Company would be 114.5 versus Company A’s 77 and Company B’s 101.  This approach would influence whether Our Company might alter its strategy on investment or teaming.  The decision would depend on Our Company’s ability to convince the Customer that these Sales Points provide increased value.  It is easy to error based on self-evaluation and could lead Our Company into a false sense of competitive position.

7.5.2 Function vs. Product Design - One of the basic building blocks of QFD is the identification of the functions that a product or service must provide.  Every product or service has a basic all-encompassing purpose.  The primary or basic function is identified as the prime reason for the product’s or service’s existence. Functional Analysis/Allocation (FA/A) is an early step in the system engineering process, that defines a baseline of functions and sub functions and an allocation of decomposed performance requirements. The FA/A task is to create a functional architecture that provides the foundation for defining the system physical architecture through the allocation of function and sub function to hardware-software and/or operations (i.e. personnel).
It should be clearly understood that the term “functional architecture” only describes the hierarchy of decomposed functions and their allocations of performance requirements to functions within the system. It does not describe either the hardware architecture or the software architecture of the system. It describes “what” the system will do, not how it will do it. Therefore once the functional architecture of the system is defined and a conceptual baseline approach is generated the correlation of functional architecture to physical (hardware & software) architecture needs to be generated to determine:
·         Where the function and sub functions are going to be performed in the physical design of the system and
·         If all of the functions and sub functions are being performed
·         The interfaces and what must cross each interface to perform the intended functions.
Figure 7-20 illustrates an example of a QFD matrix that correlates Functional Architecture with one potential Physical Architecture of the system. This QFD matrix provides a graphical picture of the coupling of Functional Architecture (What is to be accomplished) and Physical Architecture (How and where function is accomplished) along with were interfaces are required. Customers would likely define the primary function or all-encompassing purpose of a camera as “Take a Picture”. The systems engineer decomposes this primary function into the needed functions of Capture an image of a scene, Store the image, Display the image and Readout the image. The example illustrated in Figure 7-20 relates the needed function Capture an Image of a scene and the relationship of this function and its sub functions to a potential hardware concept.
In principle functions and sub functions can be defined totally independent of the technologies used in implementing the functions. However, often a decision is made on one or more of the technologies to be used as the result of market analysis or constructing a PPM.  To complete this decision may require Technology Trade Studies to select the best technology approach. Let’s assume a choice between a photographic process using a light sensitive material and a digital technique using a charge coupled sensor where the image is electronically captured and stored on a focal plane of electronic detectors.  Assume the decision after making a trade study of the advantages and disadvantages of both technologies is to capture the image electronically using an electronic device known as Charge Coupled Device (CCD).  The sub functions that are associated with an electronic method of image capture include:
·         Convert image light to electrical signal
·         Focus light
·         Control light intensity (to match CCD detector sensitivity)
·         Condition light
·         Block unwanted light
·         Position light
·         Support & protect components
A simplified baseline concept is to implement an electronic sensing material called a Charge Coupled Device (CCD).  The subsystem components that make up the hardware tree for a camera using an electronic sensing approach are:
·         CCD focal plane and electronic signal processing
·         Entrance focus lens that places the image at the CCD focal plane
·         Mechanical housing that proved structural rigidity and blocks outside light from CCD focal plane
·         Entrance aperture baffled to block stray light
Ideally a function is performed in only one module or subsystem.  This simplifies the interfaces, however this may be impossible to achieve.  In reality functions are likely to be accomplished over more than one subsystem and therefore over one or more interfaces.  Figure 7-20 provides a summary of a Functional to Physical QFD Matrix for this example and illustrates the following information:
·         All but two sub functions are achieved in an individual subsystem
·         Two sub functions, Control Light and Block unwanted light are accomplished in more than one subsystem.  Therefore any performance requirements associated with controlling light and blocking unwanted light are allocated over more than one subsystem
·         The subsystem Entrance focus lens & housing must support more than one function.  In this case it supports five different sub functions. 

When more than one sub function is accomplished in the same physical subsystem there can be potential interaction or interdependence of sub functions.  Also as the number of sub functions increases in any one subsystem complexity also increases. In this example an analysis should be performed to determine if functional performance of the sub functions interacts or is influenced by the other functions in the subsystem.  Tradeoff of performance may be necessary to balance out overall performance. These considerations are not readily apparent without construction of the Functional to Physical QFD Matrix.

Figure 7-20 An example functional to physical matrix for the Capture Image function of a digital camera.
It has been documented in Product Development activities that the Functional Architecture for a product or service varies little from one product version to another.  The Functional Architecture is not an invariant, but will change only slightly from one product version to the next.  The application of different technologies and design changes will cause the hardware/software tree to be different from one product version to the next.  The Functional Architecture can be considered as a “re-engineering point” from one product release to the next.  Therefore the Functional Architecture can be considered as a pattern of functions to be either reused or to be a starting point for new product/service development.

Tuesday, May 10, 2011

Constructing the Basic House of Quality

7.4 Basic Matrix Structure
The QFD process is represented by a series of interconnecting matrices that establish the WHAT, the HOW's and the interrelationship of all parameters involved in the product development process. The QFD method is simply a disciplined way of deploying the voice of the customer (VOC) through each stage of the product cycle. The objective is to keep all efforts focused on the VOC requirements, to optimize cost and to minimize cycle time while being driven by the VOC.
The QT's are used in each product phase to communicate the knowledge developed to the next stage. In each stage translations take place to systematically bring the VOC to actions taken by functional organizations that result in a product/service that satisfies the customer. The purpose of the QT charts is to focus on answering three questions; WHAT, HOW and HOW MUCH. For each product stage and for each action taken in that stage these three questions must be addressed.
The “House of Quality”, sometimes referred to as the “Enhanced House of Quality” consists of multiple “rooms”.  Four of the “rooms” are lists that capture the, “What’s, How’s, Why’s and How Much’s” of the project.  Four additional “rooms” are formed by determining the correlation and relationships between these lists.  Figure 7-4 illustrates the basic structure and location of these “rooms”.  The following sections provide detail in forming the lists and relationships between these “rooms” that make up the “House of Quality”.  All four phases of the hierarchical matrices follow this basic structure and form.

Figure 7-4 The rooms and relationships of the house of quality.
7.4.1 Voice of the Customer (The “What’s”) - QFD starts with a list of objectives, or the WHATs that we want to accomplish. In the context of developing a new product this is a list of customer requirements and is often called the Voice of the Customer (VOC).  The items contained in this list are usually very general, vague and difficult to implement directly; they require further detailed definition. These vague needs are sometimes called “verbatims”, (e.g. easy to use, lasts long time, light weight, low power, easy to modify).
Figure 7-5  The “what’s” defined by the VOC are often general statements.
One such item might be “easy to test”, which has a wide variety of meanings to different people. This is a highly desirable product feature, but is not directly actionable.
7.4.2 Transformation of Action - Once the list of WHAT’s is developed, each requires further definition. The list is refined into the next level of detail by listing one or more HOW's for each WHAT, (i.e. How are we going to satisfy the WHAT’s) as shown in Figure 7-6. This process can be further refined and expanded into a more detailed list of HOW’s.
Figure 7-6 The list of WHAT’s are transformed into a list of HOW’s
The objective of this refinement is to identify each actionable requirement - one that a clear action taken will satisfy a WHAT.
7.4.3 Handling Complex Relationships - The problem that is encountered is depicted in Figure 7-7. Many of the HOWs identified affect more than one WHAT. The approach to charting the `WHATs and `HOWs sequentially would become a maze of lines due to interrelationship that exist between the parameters

Figure 7-7 Many HOW’s affect more than one WHAT

7.4.4 Structuring the Relationships in a Matrix - The complexity of the sequential process is solved by creating a matrix with the HOW list across the top (horizontally) and the WHAT list vertical down the side of the matrix.  This determines the RELATIONSHIPS of the WHAT’s and HOW’s in a matrix where each intersect.  This is called a Correlation Matrix. Figure 7-8 illustrates by the use of a “X” where the What’s and How’s are interrelated.

Figure 7-8 A correlation matrix determines the relationships between the WHAT’s and HOW’s

7.4.5 Kinds of Relationships - The RELATIONSHIPS are the third key element of any QFD matrix and are depicted by placing symbols at the intersections of the WHATs and HOWs that are related. It is possible to depict the strength of the relationships by using different symbols. Commonly used symbols are shown in Figure 7-9.

Figure 7-9 Symbols used to show the strength of relationships.
This method allows very complex relationships to be depicted graphically and is easily interpreted as shown in Figure 7-10.

Figure 7-10 Strength symbols are placed in the matrix relating each WHAT to its respective HOW’s.
Throughout the QFD process there are repeatedly opportunities to cross check thinking, thus leading to better and more complete designs.  This technique of evolving plans into actions is useful for new product development as well as applications in business planning and systems design.
7.4.6 Target Values (How Much) - The fourth key element of any QFD chart is the HOW MUCH section. These are the measurements for the HOWs. These target values should represent what is necessary to satisfy the customer and may not be current performance levels.  Easy to test, when translated into detailed requirements may be measured in terms of the number of test points, requirement for component spacing, component edge clearance, etc. The component clearance would be a HOW and the HOW MUCH would be 0.020 inches minimum.  HOW MUCH's are needed for two reasons:
1.      To provide an objective means of assuring that requirements have been met.
2.      To provide targets for further detailed development
 Figure 7-11 The HOW MUCH’s are added in rows at the bottom of the matrix.

The HOW MUCH's, added to the matrix as shown in Figure 7-11, provide specific objectives that guide the subsequent design and afford a means of objectively assessing progress, minimizing ``opinion-eering ''.  The HOW MUCH's should be measurable as much as possible, because measurable items provide more opportunity for analysis and optimization than do non-measurable items.  This aspect provides another cross check on thinking. If most of the HOW MUCH's are not measurable then the definition of the HOW's are not detailed enough.  The HOW relationships that relate to the WHAT's become one means to check and measure to see if the WHAT requirements are being met. Viewed another way; meeting the target values will satisfy the HOW requirement.  If all of the HOW requirements are satisfied that are related to a VOC item by the relationship matrix then the VOC item is met. Therefore the focus can be now on meeting the target values and not be directly concerned with the VOC, it is taken care of by fulfillment of the HOW MUCH's.  These four key elements (WHAT, HOW, RELATIONSHIPS, HOW MUCH) form the foundation of QFD, and can be found on any QFD chart.

7.4.7 Correlation Matrix - The CORRELATION MATRIX is a triangular table often attached to the HOWs, establishing the correlation between each HOW item. The purpose of this roof-like structure is to identify areas where trade-off decisions, conflicts and research and development may be required. As in the RELATIONSHIP MATRIX, symbols are used to describe the strength of the relationships. The CORRELATION MATRIX also describes the type of relationship. The symbols commonly used are shown in Figure 7-12.

Figure 7-12 Symbols used to indicate correlation between pairs of HOW’s.

The correlation matrix identifies which of the HOWs support one another and which are in conflict.  Positive correlations are those in which one HOW supports another HOW. These are important because some resource efficiencies are gained by not duplicating efforts to attain same result. If an action adversely affects one HOW, it will have a degrading effect on the other. Negative correlations are those in which one HOW adversely affects the achievement of another how. These conflicts are extremely important; they represent conditions in which trade-offs are suggested. If there are no negative correlations there is probably an error. A well optimized product is almost always the result of some level of trade-off, which is expressed by a negative correlation.
Generally every HOW MUCH item has a desired direction. For example, POWER of 100 watts; generally driving it lower is better. A good test  for determining if a relationship is positive or negative is to ask the  question: "If power is driven towards its desired direction, are the other HOW's driven toward or away from their desired target values? If the HOW is driven towards its desired target value when power goes towards its desired target value then it is a POSITIVE RELATIONSHIP. If it is driven away from its desired target value then it is a NEGATIVE RELATIONSHIP."
Be cautious not to jump to a trade-off too quickly. The goal is to accomplish all of the HOW’s in order to satisfy customer requirements. The response to a negative correlation should be to seek a way to make the trade-off go away. This may require some degree of innovation or a research and development effort that may lead to a significant competitive advantage.

Figure 7-13 The correlation matrix is constructed on top of the HOW’s.
Frequently, negative correlations indicate conditions in which design and physics are in conflict. When this occurs physics always wins. Such trade-offs must be resolved. Trade-offs that are not identified and resolved often lead to unfulfilled requirements even though everyone has done their best. Some of the trade-offs may require high level decisions because they cross engineering group, department, divisional or company lines. Early resolution of these trade-offs is essential to shorten program timing and avoid nonproductive internal iterations while seeking a nonexistent solution.
Text Box:  Trade-off resolution is accomplished by adjusting the values of HOW MUCH's. These decisions are based on all the information normally available: business and engineering judgment as well as various analysis techniques. If trade-offs are to be made, they should be made in favor of the customer and not what is easiest for the company to perform.
7.4.8 Competitive Assessment - The COMPETITIVE ASSESSMENT is a pair of graphs that depict item for item how competitive products compare with current company products. This is done for the WHAT’s as well as the HOW’s. The COMPETITIVE ASSESSMENT of the WHAT’s is often called a Customer Competitive Assessment, and should utilize customer oriented information. It is extremely important to understand the customer's perception of a product relative to its competition.
The COMPETITIVE ASSESSMENT of the HOW’s is often called a Technical Competitive Assessment, and should utilize the best engineering talent to analyze competitive products. The COMPETITIVE ASSESSMENT can be useful in establishing the value of the objectives (HOW MUCH's) to be achieved.  This is done by selecting values which are competitive for each of the most important issues. The COMPETITIVE ASSESSMENT provides yet another way to cross check thinking and uncover gaps in engineering judgment. If the HOW’s are properly evolved from the WHAT’s, the COMPETITIVE ASSESSMENTs should be reasonably consistent.
WHAT and HOW items that are strongly related should also exhibit a relationship in the COMPETITIVE ASSESSMENT.  For example, if we believe superior dampening will result in an improved ride, the COMPETITIVE ASSESSMENT would be expected to show that products with superior dampening also have superior ride; as illustrated in Figure 7-14.
If this does not occur, it calls attention to the possibility that something significant may have been overlooked. If not acted upon, we may achieve superior performance to our “in house" tests and standards, but fail to achieve expected results in the hand of our customers.
The IMPORTANCE RATING is useful for prioritizing efforts and making trade-off decisions. Numerical tables or graphs will depict the relative importance of each WHAT or HOW to the desired end result. The WHAT IMPORTANCE RATING is established based on customer assessment. It is expressed as a relative scale (typically 1-5) with the higher numbers indicating greater importance to the customer. The importance ratings are listed in a column between the WHAT’s and the matrix. It is important that these values truly represent the customer, rather than internal company beliefs. Since we can only act from the HOW’s, importance ratings for these HOW’s are needed.

Figure 7-14 Competitive assessment of the WHAT’s are put in a box on the right side of the matrix.

7.4.9 Importance Ratings - Weights are assigned to the RELATIONSHIP symbols, e.g. the 9-3-1 weighting shown in Figure 7-15 achieves a good variance between important and less important items. Other weighting system may be used.  For each column (or HOW), the WHAT importance value is multiplied by the symbol weight, producing a value for each RELATIONSHIP. Summing these values vertically defines the HOW importance value. In Figure 7-16 the HOW importance rating for the first column is calculated in the following manner.  The double circle symbol weight (9) is multiplied by the WHAT importance value (5), forming a RELATIONSHIP value of 45. The next double circle symbol weight (9) is multiplied by the WHAT importance value (2), forming a RELATIONSHIP value of 18. These two values (45 + 18) form the HOW importance value of 63. This process is repeated for each column as shown in Figure 7-16.
 Figure 7-15 Importance ratings are obtained by assigning weights to the symbols in the relationship matrix

Figure 7-16 Importance ratings are calculated for each HOW as the sum of the weighted importance of each WHAT.
The IMPORTANCE RATING for the HOW’s provides a relative importance of each HOW in achieving the collective WHAT’s. We see that for the HOW’s listed; “Maximum Power” with a Target Value of 200 watts has the “HIGHEST” Relative Importance. Greater emphasis should be placed on the HOW with the 83 rating than the other HOW’s. It is important that we are not blindly driven by these numbers. The numbers are intended to help us, not constrain us. Look upon the numbers as further opportunities to cross check thinking. Question the relative values of the numbers in light of judgment. Is it reasonable that the HOW valued at 83 is the most important? Is it reasonable that the HOW’s with similar ratings are nearly equal in importance?

7.4.10 The Basic Matrix Structure - The previous section can now be integrated together into one chart. Figure 7-17 illustrates the Basic Matrix Structure. All of the matrices used in the product development stages could have these basic sections. Note the correlation matrix when added to the relationship matrix takes on the shape of a house with a roof. It is from this construction that the QFD matrices are termed the ̏houses of Quality''.

Figure 7-17 The basic form of the House of Quality relates the VOC and competitive assessment information to design requirements.

Tuesday, May 3, 2011

A Basic Approach to QFD

7.2 The QFD Approach
There are several approaches to QFD; each of these approaches makes use of matrices to organize and relate pieces of data to each other.  Many times these matrices are combined to form a basic QFD tool called a “House of Quality”.
The basic approach used here is conceptually similar to the practice followed by most American manufacturing companies. In QFD we typically follow the flow as defined in Figure 7-2.  We start with customer requirements, which may be loosely stated qualitative items such as: looks good, easy to use, works well, feels good, safe, comfortable, lasts long, luxurious or specifically defined requirements. These are important to the customer, but do not represent a product definition. In order to implement a product system engineers need to convert these vague customer requirements into actionable internal company requirements, which we call design requirements. These are generally global product characteristics such that if properly executed the product will satisfy the customer requirements.

 Figure 7-2 The typical flow of applying QFD has five steps
Products are not usually developed at this glo­bal level, but rather at the system, sub-system or part level. The global design require­ments must then be translated into specific product design, company infrastructure and capital investment requirements. Every product has several critical characteristics that determine how good a product fulfills its intended functions. The QFD process allows one to track these critical characteristics throughout the development process. Next determine the required manufacturing operations. This stage is often con­strained by previous capital in­vestment. Development organizations usually do not want to build a new factory or install a new line of equipment to produce a new product ver­sion and this often constrains product design and production methods.
Within the defined operating constraints determine which manufacturing operations are most critical to creating the desired critical product and part characteristics, as well as the process parameters of those operations which are most influential. Think of these process parameters as the knobs or dials of the manufacturing operation that are controllable. The manufacturing operations are then deployed into production requirements, which are the entire set of procedures and practices that enable the production system to build products that ultimately satisfy customer requirements.
These operating procedures determine how the factory operates the manufacturing processes to consistently produce the required critical product/part characteristics. They include a number of ̏soft" issues such as inspection and Statistical Process Control (SPC) plans, preventive maintenance programs, operator instructions and training, as well as identifying the need for mistake proofing devices for preventing inadvertent operator errors
The hierarchical approach described above is not unlike the approach taken for years with varying degrees of success. The problem is that some of the translations are not made properly. There are several key reasons for these improper translations that are the result of the structure of large organizations and the complexity of the product development process.
7.3 Hierarchical Matrices and QFD Phases
There are several approaches to the implementation of QFD.  The QFD method presented here follows the approach taught by the American Supplier Institute (ASI) based upon the “House of Quality” structure. The basic matrix structure consists of various types of matrix and table sections (or “rooms”) linked together to form what has been termed the “House of Quality”.  The ASI approach implements a four phase approach with matrices representing the important characteristics for each phase.  Figure 7-3 illustrates the four phases and how the key characteristics of each phase are deployed to the next phase of development.

Figure 7-3 The four phases of QFD consist of four linked matrices called Quality Tables.

The four phase approach results in a hierarchical series of matrices where each individual matrix is called a quality table and are numbered, e.g. QT-1 thru QT-4.  In the four phase approach a team determines the relationships between customer requirements and product design requirements.  The product design requirements are then deployed to the QT-2 matrix. In QT-2, the team determines the relationships between design requirements and product design.  The product design is then deployed to the QT-3 matrix to determine the relationships between product design and process design. The process design is then deployed to QT-4 matrix to determine the relationship between process design and manufacturing operations.

The four phase hierarchical series of matrices when completed links the customer requirements all the way to the manufacturing operations.   Thus as the manufacturing operations meet their deployed requirements then indirectly the customer requirements are being satisfied.  Therefore the resulting product or system is Customer Driven.