No abstract

Coating of steel is a frequently applied approach to increase the resistance of moving machine parts towards abrasion, surface oxidation, and corrosion. Here, we show that plating circular saw blades with certain metals can help to reduce the electrical charging of wood dust during cutting, which has significant implications for occupational safety, healthcare, and lifetime of filter systems. With the example of beech wood planks, machine net energy consumption EV (J cm−3) and cumulated field strength E→V (kV m−4) as caused by electrically charged particles were compared for cutting of 10- and 20-mm deep grooves (800 mm length) using saw blades of different toothing (24, 60 teeth) and surface coating (Cu, Ag, and Cr). To ensure uniform feed per tooth (fz = 0.063 mm), saw blades were operated at different rotation speeds (4000 vs. 1600 rpm). The results demonstrate that the extent of electrostatic sawdust charging can be manipulated to a certain extent by the type of saw blade plating. Coating with chromium turned out to be most effective in shifting the electrostatic charge of the wood particles towards neutralization. Lowering of rotation speed using circular saw blades of higher toothing was an additional measure significantly reducing electrostatic charging of wood dust. Hence, cutting with a chrome-coated blade with 60 teeth can be specifically recommended as the reduction of electrical saw dust charging is not associated with higher machine power consumption.

Mechanical friction causes electrical surface charges on wooden surfaces. In this research, triboelectric activation of solid wood surfaces was investigated by using a wood brushing machine. The extent of activation and the potential influence of machine parameters, or the influence of various wood species are questions so far unanswered. The electrical surface field strengths were continuously detected by means of an electric field meter. Machine settings, such as feed rate and brush pressure, have been varied to better understand the effects on the resulting surface charges. Data showed that nylon and tynex brushes lead to strong positive electric surface field strengths while natural fibers lead to less positive surface field strengths. In contrast, steel wire brushes showed negative electrical field strengths for oak wood, slightly positive field strengths for beech wood and stronger positive field strengths for softwoods. Overall, the tendency that a higher brush pressure led to higher recorded electrical surface field strengths while a faster feed rate reduced the field strengths was observed. As these findings were influenced by wood species and brushing materials, a better understanding of specific triboelectric interactions is essential for future applications. Tailoring surface charges can be an asset for new technical applications, such as chemistry-free primer treatments prior to wood coating.