Application of advanced statistical control for edge bead reduction in laminating process
Fan, Francis Huangjia
Date of Issue2010
School of Mechanical and Aerospace Engineering
Singapore-MIT Alliance Programme
Edge beading is a side effect occurring in the extrusion coating process due to the phenomenon of neck-in. It causes the high edge defect in the finished carton roll after the laminated sheets are wrapped around the core roller; the affected carton sheets do not satisfy the requirement for surface flatness when fed into the beverage filling machines. To address this problem, statistical process control (SPC) was employed and three types of advanced control charts were applied to form a comprehensive tool set: Shewhart control chart, EWMA control chart and Hotelling T2 control chart. The selection of design parameters for these control charts was discussed respectively from the perspective of statistical and economic criteria. Experiments were conducted to check the effectiveness of SPC when engineering process control (EPC) is present. It was found that the application of SPC was very successful. Shewhart control chart was capable of detecting large process shift quickly and EWMA control chart was capable of capturing small process shift; Hotelling T2 control chart served as useful joint control procedure of multiple variables. In addition, three assignable causes were identified and they were faulty die bolt power, die-lip build-up and incorrect settings of plug and blade. Furthermore, SPC had proven to be effective in the environment of EPC. As a result, edge beading was successfully reduced in the laminating process.