Title: Six Sigma DOE approach: a case study of rotational moulding process

Authors: Sachin D. Waigaonkar, B.J.C. Babu, Amit Rajput

Addresses: Mechanical Engineering Group, BITS Pilani, K.K. Birla Goa Campus, Zuarinagar, Goa-403726, India. ' Mechanical Engineering Group, BITS Pilani, K.K. Birla Goa Campus, Zuarinagar, Goa-403726, India. ' Mechanical Engineering Group, BITS Pilani, K.K. Birla Goa Campus, Zuarinagar, Goa-403726, India

Abstract: This paper reports application of Six Sigma technique for rotational moulding of thermoplastics. The investigations were done on a typical linear low density polyethylene (LLDPE) material. Impact strength (IS) of the product was selected as one of the quality measures. Experimental runs and analysis based on design of experiments (DOE) revealed non-linear effects of process variables on IS. It was demonstrated that a target IS of 80J ± 2.95 J could be obtained by optimal fixing of process variables. As a part of Six Sigma strategy, Shainin variable search technique (SVST) is being widely accepted in industrial community to isolate |vital few from trivial many| process variables. The application of SVST in present case revealed its heavy dependence on engineering judgment and ranking of process variables. This can eliminate significant process variables from the list of critical variables. The conventional DOE methods in such cases can give dependable results.

Keywords: Box-Behenken designs; define measure analyse improve control; DMAIC; impact strength; rotational moulding; Shainin variable search; SVST; six sigma; statistical optimisation; design of experiments; DOE; linear low density polyethylene; LLDPE; process variables.

DOI: 10.1504/IJSSCA.2011.040675

International Journal of Six Sigma and Competitive Advantage, 2011 Vol.6 No.4, pp.256 - 277

Published online: 15 Jun 2011 *

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