In the classical approaches, used in Central Europe in practice, cutting forces and cutting power in sawing processes of timber are commonly computed by means of the specific cutting resistancek_c. It needs to be highlighted that accessible sources in handbooks and the scientific literature do not provide any data about wood provenance, nor about cutting conditions, in which cutting resistance has been empirically determined. In the analyses of sawing processes, the use of a model with elements of fracture mechanics involved is an alternative way. In this work, predictions of the newly developed model (FRAC_MOD) for the circular sawing machine are presented. Thanks to this modern approach, it was possible to reveal the usefulness of the FRAC_MOD, using experimental results data on fracture toughness and shear yield stresses of both Polish pine (Pinus sylvestrisL.) and Czech beech wood (Fagus sylvaticaL.). The achieved results were compared to the forecasted values obtained with classical models (CLAS_PL and CLAS_CZ), which are commonly applied in Central European sawmills. The carried out analyses allowed us to discover undesired effects in the form of underestimation of cutting power when applying the CLAS_PL and CLAS_CZ models. For that reason, the FRAC_MOD cutting model could be suggested for the prediction of energetic effects in cases of dynamical analyses and even unsteady cases.

This paper deals with the problems of wood dust production during the sawing of two-side-laminated particleboards. It points out the dangerous impact of wood dust particles on people´s health and other unfavourable influences in the working environment. The aim of the paper was to introduce the research of dustiness, to determine the content of fine particles in sawdust and analyse the influence of feed rate on the granularity of sawdust created in the process of sawing two-side-laminated particleboards using modern circular saw. Sawing parameters were chosen for the optimal cutting speed of the circular-saw blade Pilana TFZL, vc = 84.3 m·s-1 and for three feed rates of a workpiece with the cut vf = 10, 15, 20 m·min-1. The collected sawdust particles were subjected to the particle-size analysis under exactly defined conditions by sieving and the basic granulometric analysis was made. Sieve analysis gives only a general particle-size distribution without any information considering the mass concentration of fine fraction of dust. Therefore, laser particle sizer Analysette 22 Microtec Plus was used to specify details concerning the size of dust particles smaller than 63 μm, which were collected in the bottom collector.U radu se analiziraju problemi nastajanja drvne prašine tijekom piljenje ploča iverica obostrano obloženih laminatom. Upozorava se na štetan utjecaj čestica drvne prašine na zdravlje ljudi i na druge nepovoljne utjecaje u radnoj okolini. Cilj rada bio je predstaviti istraživanja o onečišćenju radnog prostora drvnom prašinom, odrediti sadržaj sitnih čestica u piljevini te analizirati utjecaj posmične brzine na granulometrijski sastav piljevine nastale tijekom piljenja ploča iverica obostrano obloženih laminatom na suvremenoj kružnoj pili. Parametri piljenja izabrani su za optimalnu brzinu rezanja lista kružne pile Pilana TFL, vc = 84,3 m·s-1, i za tri posmične brzine obratka vf = 10, 15 i 20 m·min-1. Analizirane su veličine čestica piljevine pri točno određenim uvjetima prosijavanja te je određen granulometrijski sastav piljevine. Analiza piljevine prosijavanjem daje samo opću raspodjelu veličina čestica, bez informacije o masenoj koncentraciji frakcija fine drvne prašine. Stoga je za detaljnije određivanje veličina čestica drvne prašine manjih od 63 μm koje su prikupljene u kolektoru na dnu sita primjenjen laserski uređaj Analysette 22 Microtec Plus

The measurement of cutting forces permits building of physic-mechanical cutting models for a better understanding of the phenomena observed during cutting. It also permits the design and optimization of processes, machines, tools, and wood preparation. Optimization of cutting conditions of wood-based materials can decrease the cutting forces, which directly relates to the energy consumption and surface quality. The sawdust analysis may serve for analysis of cutting kinematics and occupational health risk. The aim of the study was to estimate the correlation between the feed rate and both feed force and sawdust particle size produced during particleboard circular sawing. A saw machine type K700 was used in experiments. There were three feed rates of 12, 18, and 24 m/min executed by a horizontal pneumatic actuator fixed to the sliding side table of the saw machine. Based on the results of the experiments, a positive correlation was observed between the feed rate in a circular sawing process and feed forces and an unexpected particle size distribution depending on the feed rate.