Faculty of Forestry and Wood Technology, University of Zagreb
Abstract
The aim of this paper is a comparison of particle size distribution of sawdust in longitudinal sawing of wood by the universal circular saw when using two saw blades with different types of teeth.
Experiments were carried out by use of a universal circular saw, at the cutting speed of v = 50 m·s-1 and feed speed of vf= 16 m·min-1. A universal saw blade with triangular asymmetric spring setting teeth K1 was used as a tool, as well as a saw blade with tipped swaged teeth K2. Specimens were used of spruce, beech and meranti wood with moisture content from 8 to 10%, species otherwise typical of the production of Euro windows. Granulometric analysis of produced sawdust was carried out by a sieve machine Fritch, with the set of sieves whose mesh gauge were as follows 1.0, 0.5, 0.355, 0.1, 0.05 and the bottom. Each specimen was meshed for 15 minutes and three specimens were meshed for each variant. The results show that larger chips were produced with the use of the saw blade K2 – the proportion of 1mm mesh, where the difference in using these two types of blades was up to 25% - meranti. From the viewpoint of airborne particles, it should be emphasised that with all three species of wood, the production of particles smaller than 100 micrometers (0.05 and bottom mesh) was twice lower when sawing was carried out with the saw blade K2 than with the saw blade K1. Even though the share of fine fraction was not considerable in the obtained samples, it can be stated that these amounts are also hazardous for the work environment and therefore attention should be drawn to the results of these experimental measurements, as it is possible to affect the proportion of fine fraction smaller than 100 micrometers by an adequate choice of tool.Cilj je provedenih istraživanja usporedba raspodjele veličina čestica usitnjenog materijala nastaloga longitudinalnim propiljivanjem drva kružnom pilom s dva lista različitog tipa zubi. Istraživanje je provedeno na univerzalnoj kružnoj pili pri brzini rezanja v = 50 m·s-1 i posmičnoj brzini vf = 16 m·min-1. Korišteni su listovi pile s asimetričnim trobridnim razvraćenim zubima K1 i sa stlačenim zubima K2. Odabrani su uzorci relativne vlažnosti od 8 do 10% od smrekovine, bukovine i merantija, drvnog materijala tipičnog za proizvodnju europrozora. Granulometrijska analiza uzoraka provedena je na tresilici proizvođača Fritch i sitima veličina (stranice kvadratnih otvora) 1,0; 0,5: 0,355; 0,1; 0,05 sa dnom. Svaki uzorak prosijavan je 15 minuta, uz tri ponavljanja. Rezultati pokazuju da pri piljenju listom pile K2 nastaju krupnije čestice te da je nastalo 25% više čestica merantija krupnijih od 1 mm nego pri piljenju listom pile K1. Za sve tri ispitivane vrste drva značajno je da nastane dvostruko manje čestica sitnijih od 100 mikrometara, tzv. lebdećih čestica (sito 0,05 s dnom) piljenjem pilom K2 negoli pilom K1. Iako dobiveni uzorci nisu sadržavali znatniji udio sitnih lebdećih čestica, zbog njihovoga štetnog utjecaja na zdravlje radnika, nužno je skrenuti pozornost na to da se odgovarajućim izborom alata može smanjiti udio drvnih čestica sitnijih od 100 mikrometara
