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An Investigation on the Surface Roughness of Helix Ball-End Milling
|關鍵字:||Helix Ball-End Milling;螺旋刃球形銑刀;Surface Roughness;表面粗糙度||出版社:||機械工程學系||摘要:||
Free surface has been widely employed in industrial products in recent years. Therefore, the ball-end milling technique for machining free surface is becoming more important. As surface roughness is a crucial index of free surface, this thesis focuses on the analysis of surface roughness by ball-end milling. Theoretical analysis of surface roughness based on the motion of cutting edges is first investigated. Experiments to verify the theoretical model are also designed and conducted. The differential geometry is employed to model the cutting edges of the helix ball-end cutter. The trajectory of the cutting edge is then derived from the rotation and translation of the ball-end mill. Based on the trajectory, we derived the theoretical model of surface roughness. To verify the theoretical model, three materials with different hardness Al-6061 aluminum alloy, NAK-80 molding steel and SKD-11 alloy steel are machined by ball-end cutters with different cutting parameters through a high-speed horizontal machining center and a vertical machining center. Experimental results showed that errors between the theoretical model and experimental data in Ra are less than 85%, while those in Rmax are between 25% and 318%. Although it implies that the derived model needs further improvement, this result is much better compared with the errors 422% to 2000% in literature. In addition, experimental results also showed that the surface roughness of ball-end milling by helix cutting edge behaves better than that by straight cutting edge. Furthermore, as the hardness of the material increases, the experimental result fits better to the theoretical model.
|Appears in Collections:||機械工程學系所|
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