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In 2009, the International Organization for Standardization proposed a standard for Quality Function Deployment (QFD), and global experts were assembled to write this nine-part ISO 16355:

These can be obtained from the American Society for Quality or directly from ISO at www.iso.org/committee/585031/x/catalogue/

Like many modern quality systems, QFD emerged from Japanese manufacturing, the first published article was from Bridgestone Tire in 1966. The purpose of QFD was to improve the quality of new products still under development, as a complement to traditional quality systems that improved the quality of products already in production. The idea was that upstream quality assurance could be a faster, more cost effective, and greater customer satisfying approach than downstream quality control.

This presented methodological challenges because traditional quality improvement in the 1960s was reactive to production problems and so focused on internal operations from which quantitative data could be obtained, could be continuously improved, and costs could be lowered. New product development, however, required that developers be proactive in trying to first understand fuzzy, qualitative customer problems and design it right the first time so that revenues could be enhanced. This shift required a new qualitative tool set now known as the seven management and planning tools to work in conjunction with the quantitative tools.

Automotive manufacturers and suppliers in the U.S. and Europe began studying these methods and tools in the 1980s and developed unique approaches which have been detailed throughout the ISO 16355 standard with over 100 case studies and tools cited from multiple industries and countries. Industry sectors such as aerospace, chemical, energy, food, healthcare, service, telecommunications, and information adopted QFD by developing different approaches to address their idiosyncrasies. ISO 16355 includes the original comprehensive QFD model developed in Japan, three U.S. models known as the 4-phase model, matrix of matrices, and Blitz QFD®, and the German QFD model.

Various “voices” are cascaded in the standard including:

1. voice of the business (what strategy will this new product support);
2. voice of the project (how is this project’s success measured and which customers are most critical);
3. voice of the customer (what are customers saying and doing);
4. voice of the engineer (what must the product of service be and do);
5. voice of operations (what is critical to creating the new product or service);
6. voice of commercialization (how do we deliver the solution);
7. voice of after-sales service (what support is critical to customer satisfaction);
8. voice of the environment (what constraints does society put on our solution).

Comprehensive QFD covers iii – v for all customer needs, 4-phase QFD includes just 4 pieces of iv-v for all customer needs, matrix of matrices covers iii-v for all customer needs with application-specific subsets, and the German QFD model includes pieces of iii-iv with a focus on manufacturing, cost, and reliability for all customer needs. Blitz QFD covers all phases i-viii but only for the highest priority customer needs, which makes it suitable for product development teams facing constraints in budget, schedule, and resources.

Readers familiar with QFD and its most well-known tool, House of Quality, will notice the ISO 16355 upgrades to the methodology.

1. “Customer need” is clearly defined as a single-issue, positive statement of benefit of a customer problem solved, a customer opportunity grasped, or customer image (look good or feel good) enhanced, independent of the product, technology, and solution. Customer needs are derived from voice of the customer using a cause-to-effect analysis.
2. Precision in QFD math. Quality professionals have long decried the abacus math in Japanese models brought to the U.S. in the 1980s. These ordinal scale ratings and rankings did not support the addition, multiplication, and division operations in QFD charts because they did not have equality of intervals. Certainly no one would agree that the Olympic gold medal winner is three times faster than the bronze medal winner simply because they are ranked #1 and #3 respectively! To solve this, ISO 16355 details how to integrate the analytic hierarchy process (AHP) into QFD to obtain ratio scale values that more precisely support the math operations.
3. The House of Quality and other time- and resource-intensive matrices are now optional and more efficient effect-to-cause diagrams are recommended for most projects.

Cause-and-effect analysis in QFD

Problem solving uses cause-and-effect or fishbone diagrams to isolate the root cause of a failure from the negative effect that occurs. Kaoru Ishikawa introduced an analytic approach to breaking down the types of causal factors for manufacturing defects with the original 4Ms of manpower, machine, material, method and a sequence of examining them beginning with the operator, then the equipment, then the components or raw materials, and finally with the manufacturing process itself. Yoji Akao, when formulating QFD, reversed the sequence for new product development with a design approach where the goal was to find the root causes of customer satisfaction (positive effect) starting first with optimizing the functional requirements of product design, then its systems, sub-systems, components, and raw materials, then the equipment, and finally properly training the staff to produce it. The design approach evoked two diagrams: the cause-to-effect diagram and the effect-to-cause diagram. In QFD, we now call these “wishbone” diagrams (positive effect is customer wish or need) and draw them with the effects oriented on the left and the causal factors on the right to emulate a House of Quality matrix.

Cause-to-effect diagram

The cause-to-effect diagram is used to translate the voice of the customer into true, product-independent customer needs. Steve Jobs, co-founder of Apple Computer, said, “It sounds logical to ask customers what they want and then give it to them. But they rarely wind up getting what they want that way.” Yoji Akao wrote that, “If a means of implementation or measure has been specified, the demands underlying why such a means or measure must be captured.” This means that the voice of the customer is considered an unprocessed input from which true customer needs must be extracted. In other words, customers are more likely to specify the performance or features they require without explanation of why they want them. The customer then sub-consciously translates their “why” or benefit and verbalizes a solution requirement. This creates three concerns. First, the customer’s translation may be incomplete or wrong because they are not as expert in the solution as the provider, which is why they are seeking an outside provider. Second, the provider can meet or exceed the verbalized requirements yet still fail to satisfy the unspoken needs of the customer. Finally, this limits the opportunity for the provider to innovate faster, better, cheaper or more profitable solutions. Merely meeting verbalized solution requirements reduces competitive advantage which adds risk to both the customer and the provider. The cause-to-effect diagram often shows multiple effects from each verbalized causal factor.

Here is an example for a café. A customer enters and says to the barista, “I need a hot cup of coffee.” Since the barista is the provider, QFD classifies the verbalized statement not as a true need (even though they used the word “need”) but rather a fuzzy list of product requirements or specifications of hot, cup, and coffee. For the requirement “hot,” the wishbone or cause-to-effect diagram shown in Figure 1 is constructed by asking the customer why they want something “hot.” Their response might be “I am cold and want to feel warm,” “I am stressed and want to feel relaxed,” “I'm upset and want to feel distracted,” and “I want something to do while waiting for a friend.” These effects are the benefits they seek, and so QFD calls these true customer needs. As defined above, these are statements of their problem, opportunity, or look good/feel good situation.

Addressing the three concerns, coffee may agitate rather than relax them, 212°F coffee may be too hot to drink so they cannot warm up, and there may be more innovative technologies to deliver warmth besides temperature such as alcohol (Irish coffee), spice (chili pepper, curry), a squeezable cup that provides exercise, or something else. Additional diagrams could be made for “cup” and “coffee.” These wishbone diagrams are consolidated in a customer voice table as detailed in ISO 16355-4.

Customers are then asked to prioritize their needs. The AHP method is recommended due to its ratio scale number precision. Blitz QFD® deploys the highest prioritized needs into a solution using an effect-to-cause wishbone diagram to indicate the most critical-to-quality characteristics (CTQ) in performance, function, implementing technology, systems and sub-systems, components, raw materials, equipment and facilities, operations, training, and after-sales support. Comprehensive QFD does this for all customer needs which improves future reuse of the charts.