With the trend towards miniaturization, micromachining becomes more and more important in fabricating micro parts. Investigations have shown that unpredictable tool life and premature tool failure present a serious concern in micromachining. To further develop the process, a systematic study of various types of tool geometry has been carried out. The tool failure modes and the ways in which tool life can be improved were also studied. Experimental results show that the tool tip rigidity of the semi circle-based (D-type) end-mills is much higher than that of the two-flute (commercial type) end-mills, and the machining quality with the D-type tools is better than that of the triangle-based (-type) end-mills. The tool breakage of end-milling operations simulated using real tool geometry is in good agreement with experimental data. Both the experimental study and FEM analysis have shown that the D-type end-mills are more suitable for micromachining.

We report on the experimental investigation of nanosecond laser-induced Zn target damages versus the lens to sample distance (LTSD). The varieties of typical surface profiles associated with the evolutions of laser ignited plasma expansion were described in detail. According to the observed results, an established transient state of modified structure within an early phase of single-pulse laser ablation should play a critical role in the steps of final damage and plasma expanding. Due to the transient state, re-enhance absorption of laser energy will occur immediately in this case. On the other hand, it is deduced that the rise curves of transient absorption coefficient should obey an exponential growth, as the LTSD increasing from 103 mm to focal length ∼ 111 mm.