The dimensional quality of the car body is built on quality management of form,
fitment, and functional requirements. Each of these attributes reflects the
final product quality and, therefore, needs to be ascertained quantitatively.
Design intent and functionality conformance with specifications are paramount to
performance, and thus quality. It is accomplished through optimal Geometric
Dimensioning and Tolerancing of parts (GD&T), datum/Primary Locating Points
(PLP) strategy, tricks/levers, and assembly design. Challenges stem from the
complexity involved in the datum layout strategy and its optimization for
desired deviations. Incorrect datum schemes in design prompt underconstrained
fixtures, redundant datum, the sensitivity of datum layout, etc. and induce
defects in later stages. The end effect is smoothing out the variation issues
leading to compromise in quality.
Hence, robust datum schemes and checks become imperative for high-quality
standards, and keep components within tolerance. The article presented here
provides a design aid for quality assurance of datum and assembly dimensional
quality targets at the early stages of design. The methodology will be supported
through the design and development of a knowledge-based tool containing the
creation and validation of datum design parameters for manufacture and assembly
for the first-time-right design itself. Based on the analysis, minimizing errors
in the datum scheme in the design process such as underconstrained fixture,
redundant datum, and inefficient datum layout and defects are contained
effectively without affecting development cycle time, cost, and quality.
