# Efficiency of Machine Sanding of Wood
## 2 Materials and Methods  
Wood from six hardwood species (beech, oak, ash, hornbeam, alder, walnut) and three softwood species (pine, spruce, larch) was tested. The wood material for making test samples was dried in an industrial dryer to a moisture content of 12% and stored in a freezer to preserve its physical properties. Then, the wood specimens with dimensions of 120 \(\times\) 55 \(\times\) 20 (length \(\times\) width \(\times\) height in millimeters) were obtained from it. Each specimen was measured with a caliper with an accuracy of \(\pm\)0.2 mm and weighed using a WPS 510/C/2 balance (Radway, Radom, Poland) with an accuracy of \(\pm\)0.01 g. These measurements were used to calculate the density of the wood and to determine its initial mass. The calculated volumetric mass densities of the wood materials tested and the numbers of samples in the sample sets for each wood species tested are given in Table 1.  
Before sanding, the samples were glued with PVAc glue to raw chipboard spacers with dimensions of 120 \(\times\) 55 \(\times\) 16 (length \(\times\) width \(\times\) height in millimeters) (the purpose of this procedure was to enable complete sanding of the tested wood). The wood samples were positioned so that they were sanded along the wood fibers. The form of the test samples is shown in Figure 1.  
The samples shown in Figure 1 were conditioned for another 3 months to equalize their moisture content in the whole volume. Abrasive belts type EKA 2000 F 2000 \(\times\) 75 (length \(\times\) width in millimeters) (manufactured by Ekamant, Poznaf, Poland) with three different grit sizes (P60, P120, P180) were used for sanding; their specifications are given in Table 2.  
A small industrial belt sander, Maktek S (Cormak, Siedlce, Poland), with a horizontal abrasive belt arrangement (Figure 2) was used. The gravitational clamping assembly allowed a constant pressure to be exerted by the abrasive belt on the samples (\(p\) = 3828 Pa). The speed of the sanding belt was constant and was: \(v_{\rm s}\) = 14.5 m/s. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Type of Wood** & **Density** & \multicolumn{3}{c}{**Number of Samples in Set**} \\ \cline{2-5}  & **kg/m\({}^{-3}\)** & **Sandpaper P60** & **Sandpaper P120** & **Sandpaper P180** \\ \hline Beech (_Fagus sylvatica_ L.) & 686.6 & 5 & 5 & 5 \\ Oak (_Quercus robur L_) & 686.4 & 5 & 5 & 5 \\ Ash (_Frazimus excelior L._) & 621.3 & 4 & 4 & 4 \\ Hornbeam (_Carpinus betlulus_ L.) & 753.6 & 3 & 3 & 3 \\ Alder (_Almus glutinosa_ ([PERSON].) & 446.3 & 3 & 3 & 3 \\ Walnut (_Iuglans nigra L._) & 641.0 & 3 & 4 & 3 \\ Pine (_Pinus sylvestris L._) & 545.7 & 3 & 4 & 5 \\ Spruce (_Pica abies_ ([PERSON].) & 453.2 & 3 & 3 & 3 \\ Larch (_Larix decelita_ [PERSON].) & 420.1 & 3 & 4 & 4 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characteristics of wood specimens used in sandability tests. Figure 1: Form of research samples. A separate sanding belt was used for each wood species. Each sample was sanded along the wood fibers in 30 s intervals and after each interval, the sample was weighed using a WPS 510/C/2 laboratory scale (Radwag, Radom, Poland). These steps were repeated many times until the entire wood sample was sanded off from the chipboard spacer. In this way, the following time series were obtained for each tested wood species: time-varying sanding efficiency (1), time-varying wood loss (2), and time to sand each sample, which allowed the calculation of the average sanding time for each series of samples (3). The sanding efficiency for the intervals was calculated:  
\[s_{e}=\frac{(m_{1}-m_{2})}{A}/t_{c}\ \bigg{(}\frac{\text{g/cm}^{2}}{\text{min.}} \bigg{)} \tag{1}\]  
where: \(s_{e}\)--sanding efficiency, \(m_{1}\)--wood sample mass at the beginning of each sanding interval (g), \(m_{2}\)--wood sample mass at the end of each sanding interval (g), \(A\)--sample sanded area (cm\({}^{2}\)), and \(t_{c}\)--sanding cycle time (min.).