Variation management by functional tolerance allocation and manufacturing process selection

Abstract

The imperfections of the manufacturing process lead to functional characteristics degradation, and therefore product quality. To ensure a certain level of product quality, the synthesis of tolerance (tolerance design) aims to determine the acceptable limits of the characteristics of parts, assemblies... The allocation or synthesis of functional tolerances is an important step in the design process which takes place generally during the detailed design and greatly impacts the design of the manufacturing process, manufacturing and product control. That is why it is important, when functional tolerances are quantified, to take into account their impacts on the manufacturing cost and product quality. These two concepts (manufacturing cost and product quality) are usually considered as conflicting goals. The proposed approach aims to allocate the functional tolerances that provide the best ratio between functional performances and manufacturing cost. It is based on the "Key Characteristics" approach, developed by Boeing coupled with an activities approach. This optimization is carried out by a genetic algorithm. The process selection is performed by a constraint satisfaction algorithm. Finally, the impacts of process choices are assessed with the Monte Carlo simulation which calculates the behavior and quality of the resulting product.

Concurrent tolerance allocation and scheduling for complex assemblies

“…The mathematical function and its constants of tolerance cost models are well known before the allocation. Two metaheuristic methods used extensively in the literature are simulated annealing [12] and genetic algorithms (GAs) [1,[13][14][15][16][17][18][19][20][21][22]].…”

Tolerancing: Managing uncertainty from conceptual design to final product

“…However, this also directly affects the function of the product due to the acceptable change in the allowed variation. Tolerancing itself is linked to a number of design decisions such as cost, manufacturing process selection, and required design specification [110]. It is present significantly in the downstream product design process and has a critical effect on the product development and manufacturing, eventually effecting products' success.…”

Survey of recent advances on the interface between production system design and quality

“…Robles and Roy (2004) incorporate the manufacturing cost to attain a given tolerance in addition to manufacturing capacity constraints, measurement errors, and process capabilities. Etienne et al (2008) allocate tolerance to provide the best ratio between functional performance and manufacturing cost following Boeing's "Key Characteristics" approach. Sivakumar et al (2011) consider both the manufacturing cost and quality loss for each candidate manufacturing process in a multi-objective optimization that distributes tolerances among components.…”