New Trends in Production and Operations Management

Operations Management includes the management of all company activities that support the input–output cycle [...

Reliability, Availability, and Maintainability (RAM) Study of an Ice Cream Industry

The purpose of this paper is to provide findings for a thorough review of reliability, availability, and maintainability (RAM) analysis utilizing failure data from an ice cream industry. The case study shows how RAM analysis is very helpful in assessing maintenance intervals and in planning and organizing an effective maintenance strategy. RAM study was computed based on historical data gathered over a twelve-month period. Pareto analysis, descriptive statistics, trend, and serial correlation test of the data were conducted. The parameters for failure and repair data were computed for each machine and the complete ice cream manufacturing system. The RAM analysis assesses the current operations management and improves the quality, productivity, and performance of the line. It was found that: (a) preventive maintenance intervals for each machine and completed system for different reliability periods were calculated. (b) Two machines with the lowest reliabilities are the packaging machine and then on the freezer tunnel. The significance of these machines is vital and their maintenance must be thorough to avoid losses pertaining to quality and productivity, and (c) the worst maintainabilities occur at the exogenous machine, and on the ice cream machine, together with the complete production system. Moreover, as the RAM indices have been calculated to quantify and increase machines’ performance, production managers and engineers can easily evaluate the next moves and decisions made with respect to the function of the system

Quantitative analysis of the reliability, quality, and performance of automated production systems

A traditional, wide-spread form of organizing large-scale, narrow-scope industrial production is the automated production line. In an automated production line, all materials visit the same workstations in series, thus simplifying material handling. All the workstations are integrated in a unified system with a common automated transfer mechanism and a common control system and are synchronized so that they can begin their work simultaneously. Since automated production lines are capital intensive, it is particularly important to ensure their uninterrupted operation. A stoppage in a production line, due to a failure, causes a drop in production performance as well as possible quality problems on the products. The objective of this dissertation is to develop quantitative models for the reliability analysis and production evaluation of automated production lines, particularly concerning the quality and output rate of the manufactured products. Initially, we present a statistical analysis of failure data of a real automated production line, covering a period of four years. The analysis includes the computation of the most important descriptive statistics of the failure data, the identification of the most important failures, the computation of the parameters of the theoretical distributions that best fit the failure data, and the investigation of the existence of autocorrelations and cross correlations in the failure data. Based on the analysis of the reliability data, we then study the problem of determining the frequency of quality control inspections in a production line. We develop a simple model of a quality inspector who must set the frequency of his visits to the workstations of the production lines under his responsibility, so as to minimize the total production time of undetected, defective products produced at the lines. Finally, we develop a model of a failure-prone, bufferless, paced, automatic transfer line, with continuous processing throughout the length of each workstation. When a workstation fails, it stops operating and so do all the other workstations upstream of it. The quality of the material trapped in the stopped workstations deteriorates with time. If this material remains still in the same place for a long enough time, its quality becomes unacceptable and must be scrapped. We develop analytical expressions for important system performance measures for two variants of the model, under the assumption that the workstation uptimes and downtimes follow "memoryless" distributions. We then use these expressions to study the effect of system parameters on system performance. To evaluate the memoryless assumption, we compare the performance of the original model with that of a modified model, in which the workstation downtimes do not follow memoryless distributions. The performance of the modified model is obtained via simulation.Μια παραδοσιακή, ευρέως διαδεδομένη μορφή οργάνωσης της βιομηχανικής παραγωγής μεγάλης κλίμακας και μικρού εύρους είναι η αυτοματοποιημένη γραμμή παραγωγής. Σε μια αυτοματοποιημένη γραμμή παραγωγής, όλα τα υλικά επισκέπτονται τους ίδιους σταθμούς εργασίας εν σειρά, απλουστεύοντας έτσι την διακίνηση υλικών Όλοι οι σταθμοί εργασίας είναι ολοκληρωμένοι σε ένα ενιαίο σύστημα με έναν κοινό, αυτοματοποιημένο μηχανισμό μετακίνησης και ένα κοινό σύστημα ελέγχου και είναι συγχρονισμένοι έτσι ώστε να μπορούν να ξεκινούν τις εργασίες τους ταυτόχρονα. Επειδή οι αυτοματοποιημένες γραμμές παραγωγής είναι συστήματα έντασης κεφαλαίου, είναι ιδιαίτερα σημαντική η εξασφάλιση της απρόσκοπτης λειτουργίας τους. Μία στάση σε μια γραμμή παραγωγής λόγω βλάβης, πέρα από την μείωση της απόδοσης παραγωγής, μπορεί να επιφέρει και ποιοτικά προβλήματα στα παραγόμενα προϊόντα. Αντικείμενο αυτής της διατριβής είναι η ανάπτυξη ποσοτικών προτύπων για την ανάλυση αξιοπιστίας και την εκτίμηση απόδοσης αυτοματοποιημένων γραμμών παραγωγής, κυρίως όσον αφορά την ποιότητα και τον ρυθμό των παραγομένων προϊόντων. Αρχικά, παρουσιάζουμε μια στατιστική ανάλυση δεδομένων αξιοπιστίας μιας πραγματικής αυτοματοποιημένης γραμμής παραγωγής, που καλύπτει μια περίοδο τεσσάρων ετών. Η ανάλυση περιλαμβάνει τον υπολογισμό των σημαντικότερων περιγραφικών στατιστικών στοιχείων βλαβών, τον προσδιορισμό των σημαντικότερων βλαβών, τον υπολογισμό των παραμέτρων κατανομής και την διερεύνηση για την ύπαρξη αυτοσυσχέτισης και συσχέτισης στα στοιχεία βλαβών. Βασιζόμενοι στην ανάλυση των δεδομένων αξιοπιστίας, στην συνέχεια μελετάμε το πρόβλημα του καθορισμού της συχνότητας επιθεωρήσεων ποιοτικού ελέγχου σε μια γραμμή παραγωγής. Αναπτύσσουμε ένα απλό μαθηματικό πρότυπο ενός επιθεωρητή ποιότητας που πρέπει να καθορίσει την συχνότητα των επισκέψεων του στους σταθμούς εργασίας των γραμμών παραγωγής που βρίσκονται υπό την ευθύνη του, με σκοπό να ελαχιστοποιηθεί ο συνολικός χρόνος παραγωγής των μη-ανιχνευθέντων, ελαττωματικών προϊόντων που παράγονται στις γραμμές. Τέλος, αναπτύσσουμε ένα μαθηματικό πρότυπο μιας υποκείμενης σε βλάβες αυτόματης γραμμή παραγωγής, χωρίς ενδιάμεσους χώρους αποθήκευσης, με συγχρονισμένη, βηματική κίνηση και συνεχή ροή της επεξεργασίας κατά μήκος κάθε σταθμού εργασίας. Όταν ένας σταθμός εργασίας πάθει βλάβη, σταματά, με αποτέλεσμα όλοι οι σταθμοί εργασίας που βρίσκονται στα ανάντη από αυτόν να σταματούν επίσης. Η ποιότητα των προϊόντων που είναι παγιδευμένα στους σταματημένους σταθμούς εργασίας επιδεινώνεται με τον χρόνο. Εάν τα προϊόντα αυτά παραμείνουν ακινητοποιημένα στην ίδια θέση περισσότερο από ένα κρίσιμο χρονικό όριο τότε η ποιότητα τους γίνεται μη αποδεκτή και πρέπει να απορριφθούν. Αναπτύσσουμε αναλυτικές εκφράσεις για σημαντικά μέτρα απόδοσης του συστήματος για δύο διαφορετικές εκδοχές του προτύπου, υπό την παραδοχή ότι οι χρόνοι βλάβης και επισκευής των σταθμών ακολουθούν κατανομές «χωρίς μνήμη». Στην συνέχεια, χρησιμοποιούμε αυτές τις εκφράσεις για να μελετήσουμε την επίδραση των παραμέτρων του συστήματος στην απόδοση του. Για να αξιολογήσουμε την παραδοχή της έλλειψης μνήμης, συγκρίνουμε την απόδοση του αρχικού προτύπου με αυτήν ενός τροποποιημένου προτύπου, στο οποίο οι χρόνοι επισκευής δεν ακολουθούν κατανομές χωρίς μνήμη. Η απόδοση του τροποποιημένου προτύπου εκτιμάται μέσω προσομοίωσης

Advances in Food Processing (Food Preservation, Food Safety, Quality and Manufacturing Processes)

The aim of this special issue was to bring about advances in the area of food manufacturing, including packaging, addressing issues of food safety, quality, fraud and how these processes (new and old) could affect the organoleptic characteristics of foods, with the aim of promoting consumer satisfaction [...

Performance Evaluation of an Automatic Transfer Line with WIP Scrapping During Long Failures

We develop a model of a failure-prone, bufferless, paced, automatic transfer line in which material flows through a number of workstations in series, receiving continuous processing along each workstation. When a workstation fails, it stops operating, and so do all the other workstations upstream of it. The quality of the material trapped in the stopped workstations deteriorates with time. If this material remains immobilized beyond a certain critical time, its quality becomes unacceptable and it must be scrapped. We develop analytical expressions for important system performance measures for two cases. In the first case, the in-process material has no memory of the quality deterioration that it experienced during previous stoppages, whereas in the second case it has. In both cases, we assume that the workstation uptimes and downtimes follow memoryless distributions. We use the analytical expressions to numerically study the effect of system parameters on system performance. To evaluate the memoryless assumption, we compare the performance of the original model to that of a modified model in which the workstation downtimes do not follow memoryless distributions. The performance of the modified model is obtained via simulation.transfer line, material scrapping, performance evaluation

Preliminary Study and Observation of “Kalamata PDO” Extra Virgin Olive Oil, in the Messinia Region, Southwest of Peloponnese (Greece)

While there has been considerable research related to Koroneiki cultivar in different areas in Greece, no systematic work has been carried out on olive oil analysis from one of the most important olive-growing regions in Greece, located southwest of Peloponnese, Messinia. This work is the first systematic attempt to study the profile of Messinian olive oils and evaluate to what extent they comply with the recent EU regulations in order to be classified as “Kalamata Protected Designation of Origin (PDO)”-certified products. Quality indices were measured and detailed analyses of sterols, triterpenic dialcohols, fatty acid composition and wax content were conducted in a total of 71 samples. Messinian olive oils revealed a high-quality profile but, at the same time, results demonstrated major fluctuations from the established EU regulatory limits on their chemical parameters. Results showed low concentrations of total sterols, with 66.7% of the examined samples below the regulated set limits for Kalamata PDO status; high concentrations of campesterol, with a total of 21.7%, exceeding the legal maximum of 4.0%; and a slight tendency of high total erythrodiol content. Fatty acid composition and wax content were within the normal range expected for the extra virgin olive oil (EVOO) category. However, the narrower established PDO limits in specific fatty acids showed some fluctuations in a few cases

Irradiation applications in vegetables and fruits: A review

There is an increasing trend both in advanced countries and many developing countries to centrally process fresh fruits and vegetables, properly packaged, for distribution and marketing. Irradiation technology proved to be effective in reducing post-harvest losses, and controlling the stored product insects and the microorganisms. Gamma irradiation was employed to restrain potato sprouting and kill pests in grain. Irradiation proved to be extremely beneficial in terms of prolonging the fruit and vegetable shelf life by 3–5 times. In order not to expose fruits and vegetables to high irradiation doses another approach is to use the “hurdle technology,” that is to apply more than one technology toward better quality and longer shelf life. This review summarizes a) all the obtained results in this field (either irradiation on its own or in conjunction with other technologies) on fruits and vegetables in 11 figures and eight (8) very comprehensive tables, and b) provides an insight in the various methods (EPR, TL, Comet assay among others) for detection of irradiated foods