Research On Burr Formation And Control Technology In Micro-milling

Micro-parts have increasing demands in the industrial field because of high precision, small size and higher performance and reliability. As an important research area of micro-mechanical manufacturing technology, micro-cutting technology has become a major part of micro machining because of its high processing efficiency, a wide range of materials and strong3-D processing ability. However, burrs are easily generated due to size effect, which will affect parts fitting, decrease component dimensional precision and surface quality, even result in security risks. The aim of this thesis is to investigate burr formation mechanism in micro-cutting and to propose a novel method in burrs prevention.In the process of micro-machining, geometric parameters of tool, cutting parameters and mode, geometry and material property of workpiece and so on, have important influence on the micro-burrs formation. Two-dimensional finite element model of micro-cutting is developed to dynamically simulate the micro-burr formation process and to reveal the influence of cutting edge radius, rake angle, clearance angle and cutting depth on the micro-burrs by DEFORM-2D, which can provide the theoretical foundation for the subsequent research of burrs prevention technology.The experimental study focuses on micro-milling process and pure aluninium, AISI1045steel, titanium alloy are selected as workpiece materials. Circular arc grooves are machined to get different burr shapes with different materials. Furthermore, the influence of depth-of-cut, spindle speed and feed rate on heights of burrs are investigated of pure aluminum.The negative shear area is dominant in the process of burr formation, especially near the edge of he workpiece. In order to eliminate the influence of burrs on the workpiece, a novel method is presented to prevent burrs generation actively, which uses low melting point alloy as the auxiliary support to extend the edge of workpiece. In order to eliminate the influence of negative shear area of the workpiece,the entrance side, the upper surface and exit side which are easy to produce burrs are coated with the pollution-free low melting point alloy which makes the workpiece form a thin layer of closed body. Therefore, burrs will be generated in the low low melting point alloy in place of workpiece after machining. After the support material is removed, burr free component is thus achieved without damaging the shape of the workpiece. The experimental results of micro-milling of microstructure grooves show that most burrs can be controlled processed parts surface is not polluted by low melting point alloy.This thesis is supported by New Century Excellent Talents Project of Ministry of Education (NCET-11-0310) and Natural Science Fund Project of Zhejiang Province "Mechanism of Burr Formation and Control Technology in Micro-Milling based on Boundary Effect".