Quality Tools

THEME: Why do this?  An abbreviated view of how to do it

A recent article in Bloomberg/Business Week (Dec 10-16, 2012) interview by Josh Tyrangiel of Apple’s CEO Tim Cook noted a key point in business practice/philosophy: “There are always things unknowable – if we are finding zero issues, our performance bar is in the wrong place”

WHY THINK THIS WAY?  You need to improve – it must be a way of business performance in all areas

  • People, knowkedge, & technology/information
    There is a need to understand your business performance attitude (Change it or Perish)

HOW?  (An abbreviated view)

  • Understand Value Analysis
  • Identify your Competitive Advantage
    (Quality, Availability, Flexibility, Cost)
  • Tool to employ (System Audit)
  • Practice
    Need a champion/advocate
    Establish measurements
    Use a standard (ISO – 19011)

How do you compare?  For more information or questions refer to mikeg@opsalacarte.com


Robust Design & Reliability

      I delivered a webinar recently  to  describe   the  differences and similarities between robust design (RD)  activities and reliability engineering (RE)  activities in hardware product development .  A survey we took from   several hundred attendees indicated a diversity of opinions. About half the participants indicated they did not differentiate at all between the two methodologies.  Approximately 20 % indicated they did differentiate between the two methodologies, and about 30% indicated that they did not know.

I was quite surprised at the result, especially since participants came  from  working quality engineers, reliability engineers, engineering directors, system engineers, etc.  Somewhere along the way,  the  differences and similarities between the two seem to have become muddled.  Below I have    collected just twelve of the many ways in which the activities are different:


RD 1  Focus on design  transfer functions, and  ideal function development

RE 1  Focus on design dysfunction, failure modes, failure times, mechanisms of failure


RD 2   Engineering focus, empirical  models, generic models , statistics.

RE 2    Mechanistic understanding, physical models,  science oriented  approach.


RD3  Optimization of input-output functions with verification testing requirement

RE3  Characterization of natural phenomena with root cause analysis and  countermeasure decisions


RD4  Orthogonal array testing, design of experiments planning

RE4   Life tests , accelerated life tests, highly accelerated tests, accelerated degradation tests, survival  methods


RD5   Multitude of control, noise, and signal factor  combinations for reducing sensitivity to noise and amplifying sensitivity to signal

RE5   Single factor testing,  some multifactor testing ,   fixed design with  noise factors,  acceleration factors


RD6   Actively change design parameters to improve insensitivity to noise factors, and sensitivity to signal factors

RE6   Design-Build-Test-Fix cycles for reliability growth


RD7   Failure inspection only with verification testing of improved functions

RE7   Design out failure mechanisms, reduce variation in product strength. Reduce the effect of usage/environment


RD8  Synergy with axiomatic design methodology including ideal design, and simpler design

RE8   Simplify design complexity for reliability improvement.  Reuse reliable hardware .

RD9   Hierarchy of quantitative design   limits including functional limits, spec limits, control limits, adjustment limits

RE9   Identify & Increase design margins, HALT & HASS testing to flesh out design weaknesses.   Temperature & vibration stressors predominate


RD10   Measurement system and response selection paramount

RE10   Time-to-failure quantitative measurements supported by analytic   methods


RD11  Ideal function development for energy relate measures

RE11  Fitting distributions to stochastic failure time data.  Time compression by stress application



RD12  Compound noise factors largest stress.  Reduce variability to noise factors by interaction between noise and control factors, signal and noise factor.

RE12  HALT & HASS highly accelerated  testing to reveal design vulnerabilities and expand margins.  Root cause exploration and mitigation


There are many other differences of course, but this list should start the conversation .  I  would invite bloggers to submit their own opinions  and  lists of differences (and similarities) .

Louis LaVallee

Sr. Reliability Consultant

Ops a la Carte



The other day I was thinking about my Reliability Blog and it led to my thinking about CURVES, especially those most common in Reliability Engineering. We regularly use the Gaussian function and the Weibull Chart, but as far as my experience goes, the Bathtub Curve has been the most popular way to visually summarize the lifetime expectations of just about everything. Then, looking at the curve I could not avoid noting that it uses words most common in personal daily life: Infant Mortality, Useful Life and End of Life, and that stimulated thought on life at the beginning, middle and end.

Then Rob Reiner’s 1989 Movie, “When Harry met Sally” popped into my head, not only as a way of getting your attention, but because anyone who saw the movie can undoubtedly recall “that” scene where Sally (Meg Ryan) challenges Harry (Billy Crystal) that women can deceive men by faking an orgasm and so saying Sally “fakes” a very public (and very persuasive) orgasm to convince Harry. After Ms. Ryan is through with her demonstration, a nearby customer, (Estelle Reiner, Rob Reiner’s mother), when asked by a waiter what she wanted, replies, “I’ll have what she’s having” (33rd on the list led by “Frankly my dear, I don’t give a damn”). Now, how does this relate to the Bathtub Curve? Well, if Harry and Sally link up and Harry impregnates Sally, do we then have the beginning of a Bathtub Curve? Probably not. Bathtub Curves are by definition the lifetime of a population of products (or people, et al) using a graphical representation. What do you think?

Rather than take up a lot more of your time on this issue I would like to refer you to some very well written material on Bathtub Curves and then have you comment on how you see Bathtub Curves and what purpose they have played for you in the past, the present and how you see the future.

My first source was Wikipedia: http://en.wikipedia.org/wiki/Bathtub_Curve

My second and I believe the best written and probably the most informative source is a 2-part paper written by Dennis Wilkins while he was at Hewlett-Packard (reportedly now a consultant with ReliaSoft):