The American Society for Quality lists QFD as the first subheading of its Six Sigma Black Belt Certification Body of Knowledge. Yet, most books and seminars on Design for Six Sigma (DFSS) and Design for Lean Sigma (DFLS) equate QFD to only the House of Quality (HOQ) matrix, focusing merely on the transfer function of QFD with little attention paid to the steps that have the greatest impact on understanding the Voice of the Customer (VOC).
This weak link could inadvertently skew your DFSS/DFLS outcome. In the spirit of Six Sigma and Lean Sigma, let us bring your knowledge up to date so that your downstream DFSS/DFLS activities are based on sound VOC analysis and that you draw the most power from both DFSS/DFLS and QFD.
General Electric and Motorola began in the late 1990s organizing quality tools into an improvement process that would assure both customer satisfaction and competitiveness. Quality was defined by the number of defects or failures in the product, service, or process being analyzed as measured by sigma, a statistical expression indicating how much variation there is in a product or process. Six Sigma translates roughly into 3.4 defects per million parts, transactions, lines of software code, etc.
When we can better control the variation of a process so that the natural process limits are within the specification limits, the results will be within acceptable tolerance no matter what degree of controlled variation occurs. Thus, Six Sigma (more recently called Lean Sigma) is an attempt to apply quality principles and statistical measurement not just to manufacturing processes, but to all corporate endeavors.
DFSS/DFLS can be seen as a subset of Six Sigma focusing on preventing problems, instead of just fixing them. DFSS/DFLS goes further upstream to recognize that decisions made during the design phase profoundly affect the quality and cost of all subsequent activities.
In a traditional black box product build, designers only needed to listen to their customers. For example, a car manufacturer may dictate the required performance, dimensions, and power requirements of an engine component to its supplier through engineering specifications. Using traditional quality methods such as SPC and TQM, and more recently Six Sigma and Lean Sigma, the supplier would then produce the part to the customer's specifications, keeping the variance within the accepted levels. DFSS and DFLS have raised the bar and contributed greatly to overall quality improvement across industries.
Yet, customers can still be dissatisfied even if the design meets the specifications. This phenomenon was explained in a past issue of this newsletter that discussed "expected quality" and "exciting quality." (New Kano Model Workshop deals with this issue directly.) Furthermore, today's designers are often expected to come up with their own analysis of customers and design specifications.
In reality, however, many design teams have no tools to go beyond what the customer asks for, even though many studies have shown that this is only the starting point. QFD not only has y = f(x) transfer function of cause and effect commonly as its House of Quality matrix, but also has a variety of tools to analyze and translate the Voice of the Customer (VOC). Uniquely capable of handling both quantitative and qualitative data, QFD it is most powerful in identifying and analyzing both spoken and unspoken customer requirements and expectations — the area where it is fuzziest in the front end of product design and the greatest impact can be planted for downstream outcomes.
In essence, while DFSS is strong in the establishment of transfer functions to deploy design parameters downstream and in establishing cost-benefit analyses and capability studies early in the design phases, QFD is strongest in further upstream analysis of unspoken true customer needs, Voice of Customer analysis and market identification and prioritizing these needs. Additionally, Modern QFD offers tools for systematically linking these true customer needs with your business goal priorities.
By linking DFSS/DFLS correctly with QFD, not just the House of Quality, you will have the best of both worlds that ensures more powerful DFLS/DFSS outcome. This method is now covered in the QFD Green Belt® and QFD Black Belt® Courses. It is possible to have the Expertly Linking DFSS and QFD Seminar as an in-house training; please Send Inquiry.
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