Surface quality measurement by contact and laser methods on thermally modified spruce wood after plain milling

The accuracy and reliability of a measuring device is crucial to determine the quality of wood surface. This paper compares the surface quality of thermally modified spruce wood measured by two different methods. Spruce wood specimens were thermally modified at different temperatures (160, 180, and 210 °C) and then milled with a single-spindle milling machine operated at different combinations of processing parameters (cutting speed, rake angle, and feed rate). Surface quality (surface roughness and surface waviness) of the specimens were measured by laser as well as contact method. Higher values of surface roughness and waviness were obtained by the laser method compared with the contact method. Average surface roughness was 31% higher, while average waviness was 35% higher in laser method as compared with the contact method. Based on the surface quality obtained by laser method and energy consumption during milling, the optimum combination of parameters for milling of thermally modified spruce wood was ascertained. The best surface quality with lower energy consumption during machining was obtained in spruce wood thermally modified at 210 °C and processed at a cutting speed of 20 m/s, rake angel of 20°, and a feed rate of 4 m/min.