HOW TO ELIMINATE COST OF QUALITY BY
DESIGN
Copyright © 2005 by Dr. David M. Anderson, P.E., CMC
Eliminating the Cost of Quality begins with designing in quality to avoid costly
defects, errors, rework, scrap, procurement of replacement materials,
factory/machine capacity degradation, re-qualifications/re-certifications costs, and
overhead demands to sort out quality problems which rob resources from
implementing the overall cost reduction strategy.
STRATEGY TO DESIGN IN QUALITY
Methodologies to proactively assure high quality and reliability by design are taught
in Dr. Anderson= s in-house DFM training seminars and are published in the book,
Design for Manufacturability & Concurrent Engineering, Copyright 8 2004 by Dr.
David M. Anderson. Here are excerpts:
$ Quality design guidelines; 29 guidelines are presented in Chapter 10, A
Design for Quality,@ in the book Design for Manufacturability & Concurrent
Engineering.
$ Understand past quality problems. Thoroughly understand the root causes
of quality problems on current and past products to prevent new product
development from repeating past mistakes. This includes part selection,
design aspects, processing, supplier selection, and so forth. It may be useful
to have Manufacturing, Quality, and Field Service people make presentations
to newly formed product development teams showing, hopefully with some
real life examples, some of the past problems that can avoided in new
designs.
$ Quality function deployment (QFD) to define products to capture the voice
of the customer. This ensures that the first design will satisfy the A voice of
the customer@ without the cost and risk of changing the design. QFD is one
of the techniques in the collection of tools known as A Design for Six Sigma.@
$ Use Multi-functional teamwork. Break down the walls between
departments with multi-functional design teams (Deming's 9th point) to
ensure that all quality issues are raised and resolved early and that quality is
indeed treated as a primary design goal.

$ Thorough up-front work (a key element of Concurrent Engineering) so
product development teams can optimize quality starting with the
concept/architecture phase and avoid later quality and ramp problems.
$ Simplify the design for the fewest parts, interfaces, and process steps.
Elegantly simple designs and uncomplicated processing result in inherently
high quality products.
$ Minimize the exponential cumulative effect of part quality and quantity
by specifying high-quality parts and simplifying the design with fewer parts.1
The formulas state that the quality of the product (the first-pass accept rate)
will be (assuming perfect processing) equal to the quality level of the parts
to the exponent of the number of parts! So, for instance a product with 500
parts with each part being 99.9 percent good, a third of the products will
fail just from the parts.
$ Select the highest quality processing. Automated processing produces
better and more consistent quality than manual labor.
$ Raise and resolve issues early by: learning from past quality problems;
early research, experiments, and models; generate plan-B contingency plans;
and proactively devising and implementing plans to resolve all issues early.
$ Optimize tolerances for a robust design using Taguchi MethodsTM. to ensure
the high quality by design. This is a systematic way to optimize tolerances to
achieve high quality at low cost.2 It does this by using Design of Experiments
to analyze the effect of all tolerances on functionality, quality, and
manufacturability to analyze tolerance A stacks@ and A worse case@
situations. The procedure can identify critical dimensions that need tight
tolerances and precision parts, which can then be toleranced methodically.
The unique strength of this approach is that it can minimize cost while
assuring high quality by identifying low demand dimensions that can have
looser tolerances and cheaper parts.
Such a design would be considered robust so that it could be manufactured
predictably with consistently high quality and perform adequately in all
anticipated usage environments. It would also ensure that margins are
adequate for current and future components from current and future
suppliers.
Without a methodical way to determine tolerances, the alternatives would
be: (1) make all tolerances tight A just to be sure,@ which is expensive.
Tolerances that appear to be overly tight may have credibility problems and
invite interpretation or (2) inadvertently (or deliberately) make tolerances
too loose, leading to manufacturability and quality problems. Performance,
quality, and manufacturability problems may be inconsistent and thus hard to
troubleshoot and rectify. Robust design is one of the techniques in the
collection of tools known as A Design for Six Sigma.@

$ Poka-Yoke principles applied to product design to prevent mistakes by
design in addition to traditional manufacturing techniques to prevent
incorrect assembly or fabrication
$ Proactively minimizing all types of risk, not just functionality. For critical
applications, use Failure Modes Effects Analysis (FMEA), which is one of the
techniques in the collection of tools known as A Design for Six Sigma.@
$ A Big picture@ metrics and compensation to avoid compromising quality
with cheap parts to save A cost@ or throwing a sub-optimal design over the
wall A on time.@ In many organizations, individuals do what they are
rewarded to do. If they are rewarded for releasing a design A on time,@ they
will, effectively, throw it over the wall on time, ready of not! If they are
rewarded for achieving A cost targets@ without total cost measurements,
they will do so by buying the cheapest parts available, probably without
concern for part quality. So reward systems must be structured to include
quality metrics
$ Reusing proven designs, parts, modules, and process to minimize risk and
assure quality, especially on critical aspects of the design.
$ Document thoroughly and completely. In the rush to develop products,
many designers fail to document every aspect of the design thoroughly.
Drawings, manufacturing instructions, and bills-of-material sent to the
manufacturing or vendors need to convey the design unambiguously for
manufacture, tooling, and inspection. Imprecise drawings invite
misunderstandings and interpretation, which add cost, waste time, and may
compromise quality. Centralize the most current data with good product data
management.
$ Thoroughly design the product right the first time. Use Design for
Manufacturability techniques presented herein to ensure that the product is
design right the first time. If quality is not assured by the initial design, then
expensive change orders will have to be carried out, wasting valuable
engineering resources and possibly inducing further quality problems in the
process. Be sure to be able to comfortably satisfy design goals and constraints
without having to compromising the product just to get products out the
door.
Designing for quality is what gets quality from 5 sigma to 6 sigma.3
ENDNOTES/REFERENCES

1. David M. Anderson, Design for Manufacturability & Concurrent Engineering,
(2004, CIM Press; 1-805-924-0200); Chapter 10, “Design for Quality,” Section
10.3, “Cumulative Effects on Product Quality.”
2. Quality by Design; Taguchi Methods and US Industry, by Lance A. Ealey, ASI
Press, Dearborn, MI; 1988.
3. Subir Chowdhury, “Design for Six Sigma,” (2002, Dearborn Trade
Publishing).
For more information call or e-mail:
Dr. David M. Anderson, P.E., CMC
www.HalfCostProducts.com
phone: 1-805-924-0100
fax: 1-805-924-0200
e-mail: andersondm@aol.com
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