Productivity and quality modeling for multistage battery manufacturing

Picture source: http://media.jrn.com/
INDUSTRIAL ENGINEER – VOLUME 47, NUMBER 11

Battery assembly manufacturing requires multiple inspections, such as dimension and joint inspections (after stacking and welding operations) and electric and leaking tests. Defective batteries are repaired before returning to the main line for downstream operations.

In such systems, even minor defects may cause severe problems as the errors accumulate.  Since all defects need to be repaired, such quality propagation and degradation may lead to productivity variation. Moreover, the repairing process affects downstream quality behaviors.

As productivity and quality are critical issues in manufacturing, studying the integrated productivity and quality system is significant. An analytical model of such integrated systems in battery manufacturing was introduce in “Modeling, Analysis and Improvement of Integrated Productivity and Quality System in Battery Manufacturing” .

Analytical methods based on an overlapping decomposition approach have been developed to estimate the line production rate of conforming batteries. Quality propagation is characterized through a model that analyzes the interactions between quality behaviors in each inspection and their potential impact on the quality of finished products.  The convergence of the method is proven analytically and the accuracy of the estimation is justified numerically.

In addition, bottleneck analysis methods based on the probabilities of blockage, starvation and quality statistics are introduced to identify the machine or stage impeding productivity and quality in the strongest manner. Indicators are proposed to identify the downtime and quality bottlenecks.

These methods provide a quantitative tool for modeling, analysis and improvement of productivity and quality in battery manufacturing systems, and they can be applied in other manufacturing systems with integrated productivity and quality models.