Evaluation of wood surface roughness by confocal microscopy

The main aim of this study is to define the usability of the confocal scanning optical microscope (CSOM) to evaluate the wood surface roughness. Therefore, systematic investigation was carried out to define the influences of CSOM on the acquisition of 2D surface roughness parameters. Mahr Perthometer was applied to get reference data to estimate the applicability of the CSOM. Because wood roughness parameters measured with stylus and optical methods are not always comparable a calibration method was conducted on a metal calibration etalon. After the calibration process, the roughness profiles taken with the optical and stylus units were much closer to each other and only the optical Rpk parameter was definitely higher due to artificial peaks generated by the optical system. In order to eliminate this measuring failure, the morphological filter option of the optical apparatus may be activated. The surface roughness parameters were measured on planed Scotch pine samples. The planed surface plains were produced with 0.2 mm parallel offset to investigate the structural influence of the single cutting plains. The obtained results show that the average values for Ra, Rq, Rz, Rk, and Rvk are close to each other for both measuring systems, only the optically measured Rpk values must be corrected. The standard deviations, however, are systematically slightly higher for optical system. This may be explained by the higher resolution of the optical system giving more fine profile details. The earlier developed and introduced dimensionless quantities, such as Abbott ratio, are also fully comparable for both systems provided that the optically measured Rpk values are also correct.

The effect of the position of 2D roughness measurement on the roughness parameters by natural wood material

There are notable differences between the 2-D standardized surface roughness parameters depending on the position of the profil of the surface roughness eavluation of natural wood.Therefore it is fundamental to determine which parameters are the least dependent on the position of the measured profil. The dependence of the standardized roughness parameters on the different measuring positions varies. We observed the smallest average dependence at the arithmetic average roughness (Pa) parameter of the P-premary profile, and at the Mr1 (threshold as the minimal Asperities’ height distribution AHD )and Mr2 (threshold as the maximal AHD) parameters and “reduced” height peak amplitude (Ppk) was more dependent. The greatest deviation occurs in the mean roughness depth (Pz), maximum height of the profile (Pt), and the maximum roughness depth (Pmax) values. These three parameters whoed the highest differences in function of the measuring positiions.

A calibration method of the laser triangular measuring system to evaluate wood surface roughness

Due to the fact that wood roughness measurement results measured with stylus and optical methods are not always comparable a new calibration method was proposed. In order to compare the surface roughness parameters of the stylus tactile 2D roughness parameters and the optical 3D roughness parameters a systematic experiment has been carried out on fourteen wood species. The essence of this calibration method is the use of metal calibration etalons for Rz = 20 μm and Rz = 30 μm and the filter option of the optical measuring apparatus. After the calibration process, the roughness profiles taken with the optical and stylus units were much closer each to other decreasing the difference in the measurement results of the two systems. Our study prove that the laser triangular method is less usable for the planed wood surfaces.