Adapting Lean Six Sigma for small-scale production : a case study on cellulose foam optimization

Abstract

Amidst urgent global efforts to replace microplastic-generating petroleum foams, this study assesses the viability of Lean Six Sigma (LSS) methodology to optimise small-scale cellulose foam production for sustainable footwear insoles. As a collaborative effort to bridge the lab-to-market gap, a tailored DMAIC framework is created to address critical quality issues persistent in lab-scale manufacturing for this thesis work. The baseline analysis of existing processes revealed a 44.5% production yield, incapability of maintaining thickness consistency (Cp = 0.22) and a high amount of defects and imperfections. An approach combining statistical inferences from limited data, along with careful implementation of less-resourceintense and rapid tools like workspace reorganisation, mold redesign, and batch optimization was designed. This approach was successful in achieving a 90% yield, 10% reduction in cycle time and 70% reduction in thickness variation. While final process capability (Cp=0.70) still fell short of industrial standards, user testing showed significant improvements in product comfort and fit.

This thesis showcases the suitability of LSS tools to be used for small-scale environments to effectively mitigate the gap between lab-scale innovation and commercial viability for sustainable materials, though there are still challenges for conversion to full industrial scalability. The findings also provide a practical framework for small-scale biomaterial optimization while showcasing the need for integrated process-material solutions.