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Rockwell Collins Inc. develops communication and aviation electronics
solutions for commercial and government customers. To
mitigate inherent variation in supplier manufacturing processes
and ensure customer satisfaction, a team applied Design for Six
Sigma to a new product design. The DMADV (Define, Measure,
Analyze, Design, Verify) project team focused on a key product
characteristic – a discrete input circuit – and dramatically
improved the manufacturability and reliability of the product. The
project achieved 6-sigma quality in two out of the three circuit
responses. Moreover, the circuit is a fundamental function that
will be used in many upcoming products, extending the positive
impact of the design.
Define
Traditional electrical design methods use a single or
small set of nominal values to prove design specification
adherence. Such methods do not consider the real world of
variation inherent in all supplier manufacturing processes
that produce electrical components. Often, improvement
in manufacturing capability can be realized if the effects of
this variation on a given product can be quantified and
mitigated at the design stage…
Measure
The primary objectives of the Measure phase were to
model the circuit in the appropriate electrical simulator,
develop and execute virtual DOEs using the simulator to
determine the output responses, and derive mathematical
equation(s) that describe the circuit’s output responses as
a function of the controlling inputs…
Analyze
The circuit uses the popular LM317 linear voltage regulator
integrated circuit (reference designators U25 and
U27) to provide the two main input voltage supplies,
15V_Dig and 5.65V_Ref. The behavior of this regulator is
given analytically as equations in the manufacturer’s published
datasheet (the output voltage adjustment pin current
term was included in the analysis but is not shown
since its effect was negligible). Those equations were substituted
into the regression polynomials and the resulting
equations used as…
Design
Looking at the LM317 datasheet revealed that the
onboard reference voltage source is specified with a tolerance
of plus or minus 1.6 percent over the operating temperature range of the device. This uncertainty is inherent in the component and cannot be mitigated. Thus, to
reduce the output variation of both supplies, we had to try
tighter tolerances for the programming resistors…
Verify
Finally, we reran the full Monte Carlo model with the
changes brought about by this project to determine the
effect on capability of the performance metrics. In all three
cases, capability was significantly improved, with 6-sigma
quality achieved in two out of the three circuit responses…
AUTHOR
Terry Peres has spent his engineering career in the electronic
manufacturing industry and is currently completing Black
Belt certification requirements. He is employed as a manufacturing
engineer for Rockwell Collins.
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