ECONOMETRIC PATTERNS AND METHODS USED FOR ANALYSIS OF TECHNOLOGICAL INNOVATIONS IN WORKSHOPS AND PRODUCTION DEPARTMENTS EQUIPPED WITH FLEXIBLE MANUFACTURING SYSTEMS
Dima I. C., Man M., Nowicka-
Pursuant to the analysis of the assessment method of the structures of the production process, in the construction of machines, we find that, due to the requirements of diversification of assortments and features of products, criteria of the quality level and work productivity, the reduction of fabrication costs, the structure of the production process develops continuously. Starting from workshops specialized on technological procedures, the structure developed onto production lines in a sole object flow, then onto production lines in a multi-
To this purpose, flexible fabrication cells develop. The latter form develops continuously, but especially after the accomplishment of machine-
Keywords: Analysis, workshops, econometric patterns, flexible manufacturing system
For the production of unique pieces, processing is extended on machine-
Considering a flexible fabrication system, we see that it allows the processing of pieces which are different in terms of shape and dimensions, in a determined range. This possibility creates conditions for the accomplishment of variable products, under high saving conditions.
Savings are made because the degree of usage of production means increases, the fabrication time is shortened, the route and duration of transports are reduced, intermediate storage expenses decrease, the area required for production is reduced, the processing process may be systematised, proper conditions for continuous work are created and direct expenses are reduced.
Within the structures of organisation of production means, one of the forms which develop quickly is that of the “cellular” structure, a system presenting the widest conditions for flexible manufacturing.
At the same time, systems in flow start to develop, provided with computer-
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The replacement of machines is based on certain mathematical methods for explaining such replacement, but these methods do not consider tangible factors.
The issues related to the machine’s replacement, considering the degree of knowledge thereof may be: determinist issues, probabilistic ~ stochastic issues.
Determinist issues are those when the time and implications of the replacement action may be certainly determined (known). For instance, the situation of a machine whose operating costs increase in direct proportion to the duration of use. In order to reduce this cost, the machine must be replaced, so that the operating cost shall tend to increase, as shown in figure 17.Probabilistic situations are those when the time and implications of the replacement action cannot be exactly determined. Let us consider that the machine has two states: proper operating state (F) and non-
The decisions to replace machines in case the fall of machines follows a probabilistic law are those decisions where the risk is given by the impossibility to exactly determine the moment when such machine falls or the transition moment from state F to state N. Another source of risk is given by the impossibility to determine the state of the equipment when no inspection or other maintenance activity occurs. We consider that there are only two states of the equipment F and N, which are always known.We have to determine the times when the action of replacement of machines should occur.This is called machine replacement policy. In this case, we are interested in the optimal replacement policy, i.e. the one maximising or minimising certain economic criteria, such as:profit, total cost, non-
Let us consider thatthe activity of replacement of the equipment results in the further production, at the same quality level, of the same products and services previously produced by the replaced machine. Hence, fall distributions and related costs are the same for all models (except for the model which considers the technological improvement of the machine).
Preventive replacement for fixed assets implies two conditions:
the total replacement cost shall be higher after the fall itself at the moment when the preventive replacement is made;
the fall rate of the equipment increases instead of remaining constant. In order to prove this, let us consider than an equipment has a constant fall rate and follows a negative exponential law. In this case, the replacement of the machine before the fall itself does not affect the chance that the equipment may fall at the following moment. In the case of negative exponential distribution, preventive replacement represents a loss of money and other resources.
Therefore, preventive replacement is only justified when the rate of replacement grows. In case the machine is damaged, the specialist in the department should increase the preventive replacement activity. This may be a mistake, as the preventive replacement of machines (or machine components) is not always justified.
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METODY ORAZ MODELE EKONOMETRYCZNE WYKORZYSTYWANE DO ANALIZY INNOWACJI TECHNOLOGICZNYCH W WYTWÓRNIACH I DZIAŁACH PRODUKCYJNYCH WYPOSAŻONYCH W ELASTYCZNE SYSTEMY PRODUKCYJNE
Na podstawie analizy metod oceny struktury procesu produkcyjnego, w konstrukcji maszyn, okazuje się, że ze względu na wymogi dywersyfikacji asortymentu i cechy produktów, kryteria poziomu jakości i wydajności pracy, obniżenie kosztów produkcji, struktura procesu produkcji rozwija się w sposób ciągły. Począwszy od wytwórni wyspecjalizowanych w procedurach technologicznych, z rozwiniętą strukturą na liniach produkcyjnych w przepływie pojedynczego obiektu do linii produkcyjnych z przepływem wielu obiektów, a obecnie do elastycznych form produkcji. W tym celu rozwijają się komórki elastycznego wytwarzania. Ostatnia forma rozwija się w sposób ciągły, zwłaszcza po wykonaniu obrabiarek z poleceniem numerycznym. W ten sposób przechodzimy od struktury produkcji w automatycznych sztywnych liniach przepływu, wydajnych dla masowej i szerokiej zakresowo produkcji, do struktur elastycznych, szczególnie skutecznych w produkcji niskiego i średniego zasięgu.