Search results for " process control"
showing 6 items of 26 documents
An Effective Double Sampling Scheme for the c Control Chart
2015
In the present paper is developed a statistical process control inspection procedure based on a new simple-to-implement and effective double sampling scheme for the c control chart, aimed at the minimization of the number of inspected observation units and warranting fixed levels for the type I and II error risks. In particular, the formulations of the false alarm risk α, the power P of the chart, and the expected number of inspected observation units for the developed inspection procedure are given, whereas a macro of Microsoft Excel is adopted to solve the tackled problem. In order to illustrate the application of the developed approach and to investigate on the influence of several opera…
Comparing the Economic Effectiveness of Various Adaptive Schemes for the c Chart
2014
In an attempt to improve the effectiveness of statistical process control (SPC) procedures, a variety of adaptive schemes has been developed in the last decades. However, considering control charts for attributes, relatively few works about adaptive schemes have been proposed, and most of them were proposed only recently. The common characteristic of those schemes is that one or more chart parameters are allowed to adaptively vary during the SPC operations according to the sampling information history, typically the current point plotted on the chart. In this way, the adaptive schemes are smarter than the related static ones, but they are also more complicated in terms of implementation. Th…
Economic design approach for a SPC inspection procedure implementing the adaptive c chart
2014
The present paper proposes a design approach for a statistical process control (SPC) procedure implementing a c control chart for non-conformities, with the aim to minimize the hourly total quality-related costs. The latter take into account the costs arising from the non-conforming products while the process is in-control and out-of-control, for false alarms, for assignable cause locations and system repairs, for sampling and inspection activities and for the system downtime. The proposed economic optimization approach is constrained by the expected hourly false alarms frequency, as well as the available labor resource level. A mixed integer non-linear constrained mathematical model is dev…
Controlling the atmosphere in the malaxation machine headspace in order to improve the quality of Sicilian extra virgin olive oils
2012
During the mechanical extraction process of Virgin Olive Oil (VOO) some important physical phenomena and enzymatic transformations occur influencing the final product quality. The control of process parameters is crucial to ensure the quality of VOO, therefore process monitoring and control is a fundamental requirement in the modern VOO processing industry. The present work proposes a research performed in order to develop a system for the oxygen continuous monitoring inside the malaxation machine to enhance the Sicilian extra virgin olive oil typicality and to establish a correlation with the quality of the final product. The results showed that the use of oxygen during malaxation, allowed…
Pareto frontier in economic-statistical design of a dynamic c chart
2015
The present paper proposes an economic-statistical multi-objective design procedure for a dynamic c control chart. In detail, a mixed integer non-linear constrained mathematical model is formulated to solve the treated problem, whereas the Pareto frontier is described by the ε-constraint method. To show the employment of the proposed procedure a numerical case is solved and the related considerations are given.
A Multi-Objective Design Approach for the c Chart Considering Taguchi Loss Function
2014
The present paper proposes a multi-objective design approach for the c chart, considering in the optimization process of the chart parameters both the statistical and the economic objectives. In particular, the minimization of the hourly total quality related costs is the considered objective to carry out the economic goal, whereas the statistical objective is reached by the minimization the out-of-control average run length of the chart. A mixed integer non-linear constrained mathematical model is formulated to solve the treated multi-objective optimization problem, whereas the Pareto optimal frontier is described by the «-constraint method. In order to show the employment of the proposed …