# Fine Dust Creation during Hardwood Machine Sanding
## 3 Results and Discussion  
The particle-size distribution of dust created during sanding is presented in Figure 2. The content of particles sized <2.5 \(\upmu\)m and <10 \(\upmu\)m was determined using the fraction 0-63 \(\upmu\)m. Beech dust had the highest content of this fraction (56.6%). Different authors have observed a similarly high content of particles smaller than 63 \(\upmu\)m in beech wood dust when P80 paper was used, ranging from 50% for a hand orbital sander [42] to approximately 90% for a hand belt sander [35]. A comparative study [5] of the performance of various  
Figure 1: Scheme of the prototype sanding machine used in this work. sanders showed that when hand belt sanding was used, these particles accounted for 70% of total particles, 82% for a hand disc sander, and 56% for a narrow belt sander, respectively. This was due to the highly different operating characteristics of individual sanders, which significantly determined the particle size of the created dust. The machining parameters used in this work were different compared to hand sanders, i.e., a higher sanding speed and lower sanding pressure were applied, respectively. The mean particle diameters of the examined hardwood species and the content of the smallest wood dust fractions, i.e., <2.5 \(\upmu\)m and <10 \(\upmu\)m, are presented in Table 2.  
The extreme values of the average mean diameters of dust particles were 76.5 \(\upmu\)m and 144.7 \(\upmu\)m for beech and walnut, respectively. No statistical differences (\(p\) = 0.05) in the parameters were found for ash, oak, and hornbeam (Figure 3). The large differences between particle mean diameters result from the limitations of sieve analysis. A low number of particle size ranges is taken into account in the calculation of the results of this method (four ranges in this study). This method assumes that larger size ranges are used for coarser particles. Each subsequent sieve has an aperture twice larger than the previous one. This causes the rate of the coarsest particles to strongly influence the average particle size, and the values of the standard deviation are also high. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Wood Species**} & **Particle Arithmetic Mean** & \multicolumn{2}{c}{**Mass Content of Particles (\%)**} \\ \cline{2-4}  & **Diameter (\(\upmu\)m)** & **\textless{10} \(\upmu\)m** & **\textless{2.5} \(\upmu\)m** \\ \hline Black alder & 119.5 \({}^{\text{c}}\)\(\pm\) 4.65 & 5.8 \({}^{\text{b}}\)\(\pm\) 0.63 & 1.0 \({}^{\text{abc}}\)\(\pm\) 0.24 \\ European ash & 94.7 \({}^{\text{b}}\)\(\pm\) 3.45 & 7.5 \({}^{\text{bc}}\)\(\pm\) 2.03 & 1.6 \({}^{\text{bc}}\)\(\pm\) 1.49 \\ Common walnut & 144.7 \({}^{\text{d}}\)\(\pm\) 0.40 & 2.8 \({}^{\text{a}}\)\(\pm\) 0.46 & 0.4 \({}^{\text{a}}\)\(\pm\) 0.06 \\ Pedunculate oak & 100.1 \({}^{\text{b}}\)\(\pm\) 4.89 & 8.9 \({}^{\text{c}}\)\(\pm\) 0.43 & 0.4 \({}^{\text{ab}}\)\(\pm\) 0.23 \\ European beech & 76.5 \({}^{\text{a}}\)\(\pm\) 5.60 & 7.5 \({}^{\text{bc}}\)\(\pm\) 2.11 & 1.9 \({}^{\text{c}}\)\(\pm\) 0.66 \\ Hornbeam & 102.7 \({}^{\text{b}}\)\(\pm\) 0.09 & 7.3 \({}^{\text{bc}}\)\(\pm\) 0.26 & 1.3 \({}^{\text{abc}}\)\(\pm\) 0.32 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Particle mean diameter and content of the finest dust fraction of the investigated hardwood species (identical superscripts a, b, c, denote no significant difference for \(p\) < 0.05). Figure 2: Particle-size distributions of investigated hardwood wood dust by sieving method (\(n\) = 3, error bars represent the standard deviation). It seems that the equivalent sieve diameter of the particles does not strictly depend on the wood density. The average diameter of the walnut dust particles was statistically higher than that of alder, which has the lowest density in this study. It was also statistically significantly higher than the average diameter of the hornbeam dust particles, which had the highest density. [PERSON] et al.