Usporedba vrijednosti vlastitih frekvencija lista kružne pile određenih različitim metodama

In most cases high cutting speed is used when cutting wood by circular saw. This results in oscillating of circular saw blade, which may lead to destroying the tool, machine or hurting the operator. The aim of this paper is to show that it is possible to apply any of the methods used in the research as an equivalent method for obtaining the values of natural frequencies of circular saw blade. The article deals with three methods for obtaining the values of natural frequencies. The first method is modal analysis, the second method is the determination of values measured experimentally and the last method calculates the values by Bessel functions. A circular saw blade was used with the diameter of 350 mm and 36 teeth on the blade.Tijekom rezanja drva kružnim pilama vrlo se često primijenjuje velika brzina rezanja, što uzrokuje oscilacije lista kružne pila te katkad može rezultirati uništavanjem alata odnosno stroja ili dovesti do ozljede radnika. Cilj je ovoga rada prikazati mogućnosti primjene različitih metoda za određivanje vrijednosti vlastitih frekvencija lista kružne pile. U članku se prikazuje primjena triju metoda za određivanje vrijednosti vlastitih frekvencija lista kružne pile. Prva je metoda modalna analiza, druga je metoda eksperimentalno određivanje vlastitih frekvencija uz pomoć mjernog uređaja, a treća je metoda izračunavanje vrijednosti frekvencija s pomoću Besselovih funkcija. U eksperimentu je upotrijebljen list kružne pila promjera 350 mm s 36 zubi

The Skalnaté Pleso Observatory Is 75 Years Old

summary:V článku si pripomíname vznik a vývoj astronomického observatória na Skalnatom plese. Najznámejšia slovenská hvezdáreň vznikla v pohnutých časoch druhej svetovej vojny. Preslávila sa atlasmi oblohy svojho zakladateľa a prvého riaditeľa dr. Antonína Bečvářa, ako aj sériou objavov komét. Podrobnejšie je popísaných prvých 10 rokov hvezdárne i jej prechod v roku 1953 pod hlavičkou Astronomického ústavu do Slovenskej akadémie vied. Článok sa venuje nainštalovaným prístrojom i pozorovacím programom. Po popise dôležitých míľnikov v histórii hvezdárne je zdokumentované zmodernizovanie v poslednom období súvisiace so získaním stredne veľkého ďalekohľadu s priemerom zrkadla 1,3 metra a kvalitných postfokusových zariadení. Článok je napísaný podľa archívnych záznamov, zápiskov a spomienok pracovníkov

The Skalnaté Pleso Observatory Is 75 Years Old

summary:V článku si pripomíname vznik a vývoj astronomického observatória na Skalnatom plese. Najznámejšia slovenská hvezdáreň vznikla v pohnutých časoch druhej svetovej vojny. Preslávila sa atlasmi oblohy svojho zakladateľa a prvého riaditeľa dr. Antonína Bečvářa, ako aj sériou objavov komét. Podrobnejšie je popísaných prvých 10 rokov hvezdárne i jej prechod v roku 1953 pod hlavičkou Astronomického ústavu do Slovenskej akadémie vied. Článok sa venuje nainštalovaným prístrojom i pozorovacím programom. Po popise dôležitých míľnikov v histórii hvezdárne je zdokumentované zmodernizovanie v poslednom období súvisiace so získaním stredne veľkého ďalekohľadu s priemerom zrkadla 1,3 metra a kvalitných postfokusových zariadení. Článok je napísaný podľa archívnych záznamov, zápiskov a spomienok pracovníkov

The Shapes of Teeth of Circular Saw Blade and Their Influence on its Critical Rotational Speed

The main problems during cutting with circular saw blade are inaccurate cut, low quality of surface, high level of noise. These adverse effects are related to oscillation of circular saw blade. This oscillation cause adverse effects not only on workpiece but also on tool. In some case the circular saw blade reaches the value of critical rotational speed which leads to its instability and cause the oscillation of blade which may leads to destruction of tool. So the reduction of the amplitude of oscillation is essential for removing the adverse effects. This paper deals about influence of shapes of teeth as a type of modification that has positive effect oncritical rotational speed of circular saw blade. The parameters of studied models of circular saw blade were 42 number of teeth and the height of teeth with slice from sintered carbide was 14 mm. The variable parameter was the ratio between surface of teeth and surface of teeth gap. In this study was used computer software Creo Parametric 1.0 for obtaining natural frequencies of studied models. This software uses in analysis finite element method (FEM). There were done some steps to idealize the models. For calculating static and dynamics natural frequencies of modelswere used modal analysis. The critical rotational speed was calculated from obtained results by Creo Parametric 1.0 and compared on 5 models of tool

Influence of Circular Saw Blade Design on Reducing Energy Consumption of a Circular Saw in the Cutting Process

Optimal cutting conditions, which lead to a high quality of the machined surface and low energy consumption, are crucial for wood processing. This paper describes the effect of feed speed, cutting speed and mean chip thickness on energy consumption and saw blade surface temperature during the spruce (Picea excelsa) cutting process. In the experiment, the energy consumption and the surface temperature of the saw blades were measured to find the optimal cutting conditions for the energy-efficient cutting process. The surface temperature of the circular saw blade was monitored online using a non-contact infrared sensor connected directly to a PC via a USB connector. The results show that the cutting power and the surface temperature of the circular saw blade increased with increasing feed speed. The lowest values of cutting power were shown by the saw blade CSB3. Compared to the classic CSB1 circular saw blade, the values were lower by 8%. The surface temperature of the circular saw blade is highest at the outer edge (area of the heel of the teeth), and decreases towards the center of the circular saw blade. For an identical mean chip thickness, energy-efficient cutting was achieved at a feed speed of 21 m/min. There must be a trade-off between machine productivity and energy consumption. Monitoring the cutting process of circular saws using intelligent sensors is the way to adaptive control systems that ensure higher quality of the machined surface and cost-effective machining