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Luo, B., Li, L., Xu, M., Liu, H., and Xing, F. (2014). "Analysis of static friction coefficient between workpiece and rubber belt in sanding wood-based panel," BioRes. 9(4), 7372-7381.

Abstract

This study analyzes the critical static friction coefficient (μ0) and the static friction coefficient (μ) between work-piece and rubber belt during sanding medium density fiberboard (MDF) and particle board (PB). The purpose is to provide theoretical support for improving design techniques of sanding machine and choosing appropriate rubber belts for sanding. The results indicate that μ0 is a constant that can be calculated by maximum sanding force (sFMax) and maximum normal force (nFMax). Besides, there is an exponential relationship between intensity of pressure (P) and μ when work-piece is relatively static on a rubber belt. Among all sanding parameters, git size (G) has the greatest influence on μ. In single-factor experiment, we found that the smaller the nFMax is, the greater the μ is (for same rubber belts), but the variation rates of μ and nFMax are coincident. Six types of rubber belts are adopted, and the average μ of No. 1 and No. 4 are greater than others, but average μ of all the belts are lower than μ0, so when use such six types of rubber belts, a hold-down device or vacuum chuck should be equipped on the sanding machine. Patterns of rubber belts have some impact on μ, and appropriate patterns on the surface of rubber belts contribute to higher μ.


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Analysis of Static Friction Coefficient Between Work-piece and Rubber Belt in Sanding Wood-Based Panel

Bin Luo, Li Li,* Meijun Xu, Hongguang Liu, and Fangru Xing

This study analyzes the critical static friction coefficient (μ0) and the static friction coefficient (μ) between work-piece and rubber belt during sanding medium density fiberboard (MDF) and particle board (PB). The purpose is to provide theoretical support for improving design techniques of sanding machine and choosing appropriate rubber belts for sanding. The results indicate that μ0 is a constant that can be calculated by maximum sanding force (sFMax) and maximum normal force (nFMax). Besides, there is an exponential relationship between intensity of pressure (P) and μ when work-piece is relatively static on a rubber belt. Among all sanding parameters, git size (G) has the greatest influence on μ. In single-factor experiment, we found that the smaller the nFMax is, the greater the μ is (for same rubber belts), but the variation rates of μ and nFMax are coincident. Six types of rubber belts are adopted, and the average μ of No. 1 and No. 4 are greater than others, but average μ of all the belts are lower than μ0, so when use such six types of rubber belts, a hold-down device or vacuum chuck should be equipped on the sanding machine. Patterns of rubber belts have some impact on μ, and appropriate patterns on the surface of rubber belts contribute to higher μ.

Keywords: Critical static friction coefficient; Grit size; Medium density fiberboard; Normal force; Particle board; Static friction coefficient; Sanding force

Contact information: College of Materials Science and Technology, Beijing Forestry University, No.35 Tsinghua East Rd, Haidian District, Beijing, 100083, P. R. China;

* Corresponding author: bjfu_lili@126.com

INTRODUCTION

The feed orientation is opposite to the sanding orientation in a sanding process. In the process of feeding, the sanding force (sF) is the resistance, and the friction (f) between rubber belt and work-piece is the tractive force. The f should be greater than the sF; otherwise, the work-piece will be kicked back. The normal force (nF) on the work-piece should be great enough for the normal feed. Meanwhile, the value of sF also increases with increasing nF. The method to keep the work-piece relatively stationary on track is increasing the static friction coefficient (μ) between the rubber belt and work-piece (Li and Meng 2000).

The value of f between the rubber belt and wood based panel (viscous-elastic material) depends on two parts: adhesion and hysteresis (results of the elasticity of both materials). Usually, adhesion is the primary part when a rubber belt slides on the material with smooth surface. But for the material with rough surface, the distortional units of rubber belt would fill into the gaps of the surface, and then the proportion of hysteresis increases (Jun 2008).

In the previous studies, Guan et al. (1983) found that the friction coefficient between steel and some Swedish wood species was higher on rougher steel surfaces. For an isotropic steel, a rougher surface resulted in lower f under low-speed condition, but under high-speed condition, the situation is the reverse (Masuko et al. 2005). The friction coefficient for helical gears increased with the improved surface roughness (Han et al. 2013). This study focused on analyzing the critical static friction coefficient (μ0) and μ between work-piece and rubber belt during sanding medium density fiberboard (MDF) and particle board (PB). The purposes of this study are to provide theoretical support for improving design technics of sanding machine and choosing appropriate rubber belts for sanding.

EXPERIMENTAL

Materials

MDF and PB used in the work had an average density and surface hardness of 0.74 g/cm3 and 0.99 g/cm3, and 51.7 HD and 64.1 HD, respectively. The sizes of work-pieces were 150 x 100 mm (superficial area=0.0015 m2) and 63 x 63 mm (superficial area=0.003969 m2). Abrasive belts were made by Tianjin Deerfos Co., LTD (base material: twill, grit: white fused alumina, electro coated abrasive and adhesive: phenol formaldehyde resin). Figure 1 shows the characteristics of six rubber belts (HDSY Co., LTD, Shanghai, China), and the surface hardness of them was 19.2 HD.