Title: Work of adhesion as criterion for determination of optimum surface tension in adhesives
Author: Andrija Bogner
The article presents a new method for determination of the optimum surface tension in adhesives (glues and wood varnishes). The criterion employed is maximum work of adhesion. In view of the fact that work of adhesion depends, among other things, on the free surface energy of wood and the surface tension of the adhesive, and that the free surface energy changes in relation to roughness, this experiment was carried out on three groups of specimens of beech wood with radial surface. One group of specimens thus had a sanded surface, the second group consisted of planed pieces, while those in the third group had a surface worked out with a steel hand scraper. Work of adhesion can be good criterium for determination of optimum surface tension because it take into consideration adhesiv, adherent and their interaction. The roughness of wood sutface was measured and expressed as the average arithmetic deviation of the surface roughness profile Ra. The wetting angle Θ was also meusured for nine liquids with different levels of surface tension. On the basis of the wetting angle and surface tension the critical surface energy of wood (γc) was calculated, as well as the work of adhesion (Wa), the optimum surface tension of the liquid wetting the wood surface in question (γL,G,opt) and the maximum work of adhesion (Wa,max).
Title: Research on interactions between tehnology and production organization in wood processing
Author: Mladen Figurić
The paper presents the results of research into interactions between the technologv and production organization in wood processing. The research has been carried out in fifteen-year intervals since 1960. The introduction presents summarized results of Lawrence, Litterer, Woodword and others, and the need for research analysis. Since there has been no such research in woodprocessing so far, the main issue is the interaction between technology and a production organization in wood processing. Research methods consisted in work time structure assessment in time intervals of fifteen years on the basis of the results obtained by Ettinger (1963, 72,65% operation time) and Figurić (1978, 1993. 57,63% and 51,51% resp.), on the same sample fundamental conclusions have been made. A research into the significance of the results from three different (time) periods has led to the conclusion that firstly, there is a strong correlation between the installed technology and production organisation (r = 0,92); secondly, Ettinger did his research in mechanical-manual production, while Figurić’s research was carried out in a highly mechanized manufacture. There has been no significance in the results referring to periods I, II and I, III, whereas between II and III significance has been assessed. Further on, the obtained results were compared to Gašparović’s predictions (75%-80%) for expressing time in flexible tehnological systems, according to which electopolation of the obtained work time curve of the investigated time period was made. Thus were established the basic parameters of the relation between the designed technology, the production management model and production organization in wood processing.
Title: Scheduling and rescheduling rules in wood industry production systems
Author: Denis Jelačić
This paper contributes to the research on planning, managing, and scheduling of production by using new methods of determining priorities in issuing production orders; it is an attempt to apply those methods to new concepts of production and operations management implemented in woodworking firm. The aim of the research was to establish the manner in which the differences between individual methods are manifested and their relevance for the particular production in the observed furniture factory; which of the methods is the most acceptable in production scheduling and rescheduling resp.; what are the possibilities to reduce production costs, and how could the observed methods be adapted and applied to new concepts of production and operations management. In line with the research aims, relevant factors for the selection of scheduling und rescheduling methods in wood-technological industry were established. All the relevant factors were then analysed by means of different result processing methods and by establishing their impact
upon the total production cycle duration. The obtained results provided the basis upon which the quality and applicability of the individual method were established as well as the factors influencing their choice. The SOT (KVO) method achievod the best results. This method gives priority to orders that have the shortest production cycle duration in the first or the first two processing phases. Among the rescheduling methods, the best results were established with the DS/PT (DRVP) method which gives the priority to orders with the smallest ratio between the delivery time reduced by the remaining expected time on the one hand and remaining work on the other. Further analysis resulted in an assumption that the observed methods may be applied in the planning process in wood-technological firms. With certain restrictions, they may be implemented in new concepts of production and operations management. The main achievement of these methods is rationalization of the production management process.
Title: Anwendung von Harnstoff-Formaldehyd-Leimen fur die Flachenverleimung in der Produktion von Mobel und Schichtholzwerkstoffplatten
Author: Manfred Dunky, Stjepan Petrović
Die Holzverleimung mit Harnstoff-Formldehyd-Leimen ergibt Produkte hoher Qualitat, wemi die dafur wichtigen Parametern und Bedingungen eingehalten werden. Nahmlich eine Reihe von Faktoren beeinfluβen die Adhasion und somit die Adhasion und somit die Qualitat des Fertigproduktes. In dem Artikel wurden daher die Empfehlungen fur die richtige Anwendung geben. Diese Empfehlungen, die aufgrund jahrelangen praktischen Erfahrungen der Autoren im Bereich der Holzverleimung entstanden worden sind, sollte man als Beilage zur Verbesserung der Anwendung von UF- Leimen bei der Flachenverleimung in der Mobel-und Schichtholzplattenproduktion annehmen.
Title: Computer Networking in Production Control Systems
Author: Bojana Dalbelo Bašić
The paper presents certain advantages of computer networking and some options in networking. There are different classifications for networks, depending criteria chosen (geographical spreading, purpose, construction etc.). Two local network types are important for production control systems: industrial and office networks. The paper also explains the concept of layered network structure which is the basis for standardisation procedures and therefore also for the establishment of communication systems adjusted to the needs and possibilities of the user. The ISO/OSI model is described. The basic methods of computer connection to local networks and the physical means for these connections are presented. The possibility of an independent selection of the local computer network operating system is discussed and illustrated with an example.