Investigating Surface Quality of African Mahogany (Khaya Ivorensis) From Ghana using Stylus and Deflectometry Techniques

Abstract

Studies and information are limited on quantitative evaluation of machined surfaces of tropical
African hardwood species such as mahogany (Khaya ivorensis). In this study, surface quality of mahogany from plantations and natural forests that were harvested near Pra-Anum Forest Reserve, Ghana was evaluated using the stylus profilometer and Optimap deflectometry techniques. The evaluation was made at three different height levels: bottom, middle, and top portions of harvested trees. The average roughness, mean roughness depth, maximum surface roughness, core roughness depth, reduced peak height, reduced valley depth, total height of roughness, and maximum depth of roughness motif were estimated on tangential surfaces of the samples after sanding using sandpaper of grit size P150, P180, and P 280. Texture values were also measured at different wavelengths using an optimap device. Based on the results of statistical analysis, the selected roughness parameters varied significantly at different portions of wood samples at 95% confidence level in both plantation and natural samples except reduced peak height parameter. Results also revealed that mean roughness parameters at the bottom and middle portions of the trees had relatively lower values in plantation samples than in natural samples. This implies smoother surfaces for the plantation samples. At the top portion, however, plantation samples had relatively higher values for most roughness parameters than did natural samples. Texture values at different wavelengths showed statistically significant variation along the stem for both natural and plantation samples at 95% confidence level. Although some limitations exist in using Gaussian amplitude filters to eliminate deep sinks in the profile, the data gave a good indication of surface quality and comparison of surfaces of mahogany samples.