Material removal mechanism during MDF and Korean pine sanding processes

ObjectiveAs for wood materials, sanding technology is an important fine machining method. Investigating material removal behavior in wood material sanding process is of great significance for improving sanding efficiency and surface quality.

MethodIn this research, a single grit grinding platform was designed, and a traverse scratching method was used. The scratched surface morphology of medium density fiberboard (MDF) and Korean pine (Pinus koraiensis) was scanned and measured by SEM and 3D profiler to analyze the effects of maximum cutting depth and groove area on pile up ratio. Moreover, the variation of grinding forces and overall friction coefficient was analyzed to study material deformation. λ was defined as the angle between scratching direction and wood grain direction.

ResultIn comparison with metal grinding, the pile up area was much smaller when scratching MDF and Korean pine. When λ = 90°, the wood substance was cut bilaterally by cutting edges and some deformed material remained on Korean pine workpiece surface like stubble, and some interaction area was crushed by grit. The pile up ratio of Korean pine (λ = 0°) was concentrated at 0 to 0.05 while that of MDF was highly scattered. Both the normal force F_n and the tangential force F_t oscillated highly during scratching Korean pine (λ = 90°). While in the process of scratching MDF and Korean pine (λ = 0°), both F_n and F_t demonstrated nearly a Gaussian normal shape. With the increasing penetration of grit into workpiece, both F_n and F_t increased, and the maximum force value occurred at about the maximum cutting depth. For MDF, F_n was larger than F_t, while for Korean pine, F_t was a little larger than F_n. During the process of scratching MDF and Korean pine (λ = 0°), the overall friction coefficient was slightly higher when grit reached the deepest point and started to exit workpiece.

ConclusionDuring the grinding process of Korean pine, the inside pores (like axial tracheid and anatomic cavities) and wood grain direction exert great influence on material deformation and flow and surface quality. Compared with Korean pine, more plastic pile up occurres on bilateral sides of scratched groove when scratching MDF. And the variation of cutting depth and groove area on pile up ratio is highly scattered. As the grit penetrates into workpiece, the overall friction increases.