The aim of the paper is to draw the attention to the problem of wastes which often hase its base in ignorance or lack of awareness of the coexistence „Hidden Factiories” in the production process. The author briefly describe what is and how to identify the the phenomenon of „Hidden Factories” as well as what are the consequences behind this problem.
Requirements for quality and the full traceability of products supplied in some industries, such as eg. the food industry, the pharmaceutical industry as well as automotive industry, result that the implementation of production flow control systems (FCS) becomes a very important element in the functioning of enterprises. Production flow control systems are used generally for recording production data at different stages of industrial processes (in this respect, they fulfill the function of traceability systems), but also provide blocking of incorrectly processed identifiable components during the earlier stages of the production. The information provided by traceability can be the basis for the functioning of integrated information systems. Production flow control systems ensure the recording of important information from the point of view of customer that allows the capture of defective products, analysis of the causes of these defects, and defense against potential complaint or even a significant reduction in the number of complaints. Applied are dedicated or universal solutions, adaptable to a variety of configuration lines / production cells. Dedicated solutions (for a specific production line) are basically always developed from scratch, taking into account the specificity of the product flow. Then the structure of the data in the PLC has to be adjusted, as well as the structure of the database and the database queries. Dedicated systems have the advantage that their action is fast, whereas the drawback is a longer start-up time and modification / expansion of functionality. On the other hand, universal solutions allow to configure the number of workstations and their type (controlled by a PLC or PC), their network addresses, as well as the types of products allowed there without changing the software. The advantage of universal solutions is that additional production workstations can be added very fast to the system, while the disadvantage may be longer lasting query the database and exchange information with the PLC. The concept of an universal system must be well thought and considered have to be different configuration cases of the material flow. Poorly thought-out concept takes revenge on the creator by the necessity of profound changes in the structure of the data and the application code. The purpose of this article is to present the advantages and disadvantages of dedicated and universal TCS / FCS systems.
To meet the requirements, the products generally should be produced by a process that is stable and repetitive. It is however impossible to produce a certain type of product, in the same company and under the same conditions in such way to produce the get perfect parameters of this product, due to the occurrence of assignable causes. To analyze the stability of the production process (in order to detect assignable causes and statistical process control) used to Shewhart control charts, which are based on the assumption that the distribution of the quality characteristic (so called process distribution) is normal distributed or approximately normal distributed. However, the review of the literature has shown that in practice, the assumption of normality of many quality characteristics this condition doesn't hold, which in turn affects the improper assessment of the process stability. The most common distributions of measurement data, (beyond the normal) is skewed. For skewed population Type I Risk probabilities grow larger as the skewness increases. In this case four approach are plausible: increase the sample size up to a thousand, ignore skewness and use the classic Shewhart control charts, assume that the population distribution of the population is known and take a charts in accordance with the distribution or assume that the distribution of the population is not known and the use of heuristic methods. However, the use of one of the first three methods may prove to be uneconomical (e.g. due to the need to incur additional costs) and even result in incorrect assessment of the stability of the process. „Golden middle” in this situation can be heuristic methods, i.e. method of analysis percentiles distribution, variance weighted method or the method of correction of asymmetry, that were briefly described in this paper. The analysis of heuristic methods allowed for the choice of the least complicated due to the applicability in manufacturing companies. Additionally the studies carried out by the Cahn and Cui, showed that the Type I Risk probabilities of CS method is closer to the standard value of 0.27% than the other presented methods and, therefore, the effectiveness of this approach is much better, so in case study the author used CS method. The main aim of the paper is determine the control limits for the X and R charts based on the skewness correction (SC) method, including the risks associated with incorrect choice of method for determining the control limits. For this purpose, measurement data from a company producing automotive seat frames was analyze. All calculations were made in Statistica and Excel environment.
The paper describe the importance of Gross Error eliminating in process stability assessment. The analysis carried out at the manufacturing enterprise indicated that Gross Error might be cause of false signals in Control Chart. Additionally, the author, proposed using Johnson curves transformation to applying in statistical tools (including Control Chart, which are used in Six Sigma methodology) when the measurement data aren’t normally distributed.
Artykuł zawiera opis metody identyfikowania „ukrytych fabryk" w oparciu o wskaźniki wydajności (klasycznych i stosowanych w metodzie Six Sigma). Ocena wydajności procesu dokonywana jest na podstawie liczby wad, co w praktyce umożliwia wykrycie funkcjonowania w przedsiębiorstwie produkcyjnym „ukrytych fabryk", które są procesami, działaniami oraz systemami naprawczymi błędów powstających na poszczególnych etapach produkcji. Rozbudowany wstęp teoretyczny wzbogacono o studium przypadku, w którym przedstawiono metodę identyfikacji zjawiska „ukrytych fabryk" na przykładzie procesu produkcji odlewu w Odlewni Żeliwa S.A. w Zawierciu.
EN
The paper contains a description of the method of identifying the "hidden factory" based on performance indicators (classic and used in the Six Sigma). Performance process appraisal is carried out based on the number of defects, which in practice allows detection of "hidden factories" existing in the enterprise. „Hidden factories" arę processes, operations and systems enabling repair of errors that arise at various stages of production. Extensive theoretical introduction was enriched with a case study, which presents a method to identify the occurrence of "hidden factories" on the example of the manufacturing process of casting in Odlewnia Żeliwa S.A. in Zawiercie.
This paper contains the modern quality management strategy so called Six Sigma, which the main attention is focused on the needs and requirements of customers. The author described the main essence of the concept of Six Sigma - customer orientation and process management.
Artykuł zawiera opis praktycznego zastosowania kart kontrolnych pojedynczej obserwacji oraz ruchomych rozstępów (IX-MR), które mają na celu dostrzeżenie zmienności pojawiających się na różnych etapach procesu, a w konsekwencji dając możliwość szybkiej reakcji. Analizę stabilności procesu dokonano na podstawie pomiarów zebranych po zakończeniu trzech istotnych etapów produkcji stelażu siedziska samochodowego, a także w oparciu o wartość siły przesuwu, która jest podstawą do oceny jakości oraz bezpieczeństwa produktu finalnego. Autorzy, w artykule, zwrócili także uwagę na konieczność wyznaczenia wskaźników zdolności jakościowej (c_p,c_pk) oraz rozstrzygnięcia normalności badanych pomiarów przed przystąpieniem do wdrażania kart IX-MR.
EN
The paper contains a description of the practical application of individuals and moving range chart (IX-MR), which are aimed at enabling the user to monitor a process for shifts in the process and, consequently giving the opportunity to quickly reaction. The analysis of stability of the process was made based on measurements collected after the three main stages of automobile seat frame manufacturing, and based on the value of the actuating force, which is is very important in evaluating the quality and safety of the final product. The authors, in the article, also highlighted the need to designate the capability indicies (c_p,c_pk) and examination normality of measurements prior to implementation of card IX-MR.
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