Analysis of Friction and Burr Formation in Slot Milling

Burr formation is one of the most common and undesirable phenomenon occurring in machining operations that reduces assembly and machined part quality, and it should be avoided or at least reduced. To remove burrs, a non-value added secondary operation known as deburring is required for post-processing and edge finishing operations. Among conventional machining operations, milling burr formation is a very complex mechanism. Therefore, research and close attention are still needed in order to minimize and control milling burr formation. This could be achieved by effective burr prevention through adequate understanding of the basic mechanisms of burr formation and an accurate proposal of optimum cutting parameters. In recent reported works in literature, exit up milling side burr was characterized as the longest and thickest milling burr which is formed by loss of material during exit burr formation. Since burr thickness is a critical parameter for better selection of the deburring time and method, a good knowledge on the effects of cutting parameters, friction and tool geometry and coating on this burr is important for better selection of deburring methods. Although friction angle has a direct proportion to negative shear angle, radial and tangential cutting forces, but very limited information is still available on correlative studies between burr size and friction angle in milling operation. This paper presents the effects of cutting parameters on friction angle and the correlation between friction angle and exit up milling side burr thickness during slot milling of aluminum alloys. To that end, a computational algorithm that was recently proposed by authors is used to calculate the friction angle λ for each material when using specific levels of cutting speed, feed per tooth and undeformed chip thickness. Experimental results show that lower friction angle is resulted when using larger chip load. Consequently, larger friction angle is obtained when exit up milling side burr thickness decreases and exit bottom burr thickness increases.