Effect of Conventional and Trochoidal Milling Paths on Burr Formation During Micromilling of Grade 4 Commercially Pure Titanium

Burrs produced by end micromilling are difficult to remove because they lie along the edge of the slot and are attached to the machined component. Furthermore, they represent one of the main challenges in micromilling due to the difficulty of characterizing and controlling them. In order to minimize the formation of top burrs during micromilling, machining parameters and strategies must be selected appropriately. This work investigates the influence of the ratio of the feed per tooth to the tool edge radius ( f z /ρ), axial depth of cut and micromilling path (conventional and trochoidal) on the forces and size (width and height) of top burrs generated when dry micromilling grade 4 commercially pure titanium. The tests were performed with TiAlN coated carbide micro end mills attached to a pneumatic turbine with a rotational speed of 40,000 rpm connected to the main spindle of the machining center. A piezoelectric dynamometer was employed to record the components of the micromilling force. The width and height of the top burrs were characterized by scanning electron microscopy and by contact profilometry, respectively. The f z /ρ ratio and the axial depth of cut were the determining parameters for reducing the dimensions of the top burrs. Higher feed per tooth values and lower axial depths of cut produced narrower and lower top burrs. The top burrs were wider and higher when down micromilling in comparison with up micromilling. Regarding the machining path, the conventional machining path presented higher specific cutting energy compared with the trochoidal path.