Evaluation of surface roughness of Thai medium density fiberboard (MDF) Salim Hiziroglu à , Pantadee Kosonkorn Department of Forestry, Oklahoma State University, Stillwater, Oklahoma 74078-6013, USA Abstract Wood composites contain irregularities on their surface due to the sanding process which play an important role when they are used as substrate for thin overlays. The objective of this study is to evaluate surface characteristics of commercially manufactured medium density fiberboard (MDF) panels in Thailand. A skid type profilometer with diamond stylus of 5 mm tip radius and 901 tip angle was employed for the experiment. Roughness average (R a ), average maximum height of the profile (R z ), and maximum roughness depth (R max ) were used to evaluate quantitatively surface characteristics of the specimens. Roughness measurements were taken from both sides of the sanded specimens along and across the sandmarks over 15.2 mm tracing span. Panel type-C had the smoothest surface with average values of 2.39, 21.03, and 26.93 mm for R a , R z , and R max , respectively. It was found that no statistically (po0:1) significant difference existed between the values of all three parameters taken in both sandmark directions of all types of panels. Also none of the panels considered in this study had superior surface quality over the other. In further studies, surface roughness of MDF samples exposed to various relative humidity levels could give a better understanding of their roughness behavior for different overlaying applications. r 2005 Elsevier Ltd. All rights reserved. Keywords: Surface roughness; Wood composites; Medium density fiberboard 1. Introduction Low-quality rubberwood (Hevea brasiliensis) and eucalyptus (Eucalyptus camaldulensis) are commonly used as fiber resources to manufacture medium density fiberboard (MDF) in Thailand. Low cost and ideal anatomical properties such as short fiber length of rubberwood make it a main raw material for fiberboard manufacture [1]. MDF has smoother surface than that of any other wood composite panels such as particle- board. Therefore, it is widely used as substrate for thin overlays such as resin-impregnated papers, rice papers, other decorative overlays and direct finish to the surface for different uses including doorskin. The height, width, and shape of the irregularities on a surface establish surface quality of a product. The surface roughness of the panel plays an important role since any surface irregularities may show through thin overlays reducing the final quality of the panel. The degree of surface roughness is a function of both raw material character- istics and manufacturing parameters. There are several methods to quantify surface roughness of wood composites such as pneumatic, acoustic emission, light scattering, laser, and stylus [2–6,19,20]. The stylus method which is widely used to evaluate metal and plastic surfaces gains most attention since it determines the surface quality in terms of well established numerical parameters [7–10]. It is accurate, practical, and repea- table and quantitative roughness parameters can also be precisely calculated by this method. Variables such as the stylus tip radius, the surface force produced by the stylus, and cut-off length of the profile have important ARTICLE IN PRESS à Corresponding author. Tel.: +1 405 744 5445; fax: +1 405 744 3530. E-mail address: hizirog@okstate.edu (S. Hiziroglu).