Developing Control Measures to Reduce Variation in Weight of Packed Cement Bags

ISSN： 0898-2112

Source： Quality Engineering, Vol.17, Iss.4, 2005-10, pp. : 609-614

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Abstract

The performance of the packing process at a cement plant was found to be unsatisfactory because of the high variability of the weight of the cement bags, resulting in violation of the specification. Violation of upper specification will lead to loss of profit, whereas bags below lower specification will lead to customer dissatisfaction. This article demonstrates the use of a variety of quality improvement tools to help resolve these issues. The first step in the study was to confirm the extent of nonconformance as perceived by the management. Next, planned data were analyzed using analysis of variance techniques based on a mixed-effect, cross-nested model, to identify the possible sources of variation such as nozzles, shifts, and days of operation. The process capability was then estimated using Clements' method . Finally, the stochastic nature and economic factors ( manufacturing cost, selling price, and cost of repacking ) of production were taken into account to derive the optimum economic setting of the packing process. Implementations of the findings brought down the percentage off-specification by an amount of 39% along with a considerable reduction in variability. In the long run, this would lead to consistent production of a larger number of cement bags, along with better assurance to the customer. The additional sales value is expected to be about $249,000 annually.