Nanosecond Laser Drilling Of Thin Aluminum Sheets

Laser drilling is one of the indispensable and wide-used methods of laser processing. In recent years, the rising requirements on quality of micro-hole machining lead to the problem that traditional methods of micro-hole machining are unable to meet the requirement of depth-diameter ratio. On the contrary, laser processing can meet the demands of many special processing exactly. Because of many advantages which the multipulse paser drilling owns,such as high efficiency, low cost, enormous economic benefits.Therefore, it has become a very popular method in small hole machining. there are many studies about how to drill micro holes on many materials. But there is rare experiments about how to machine a group of micro holes on a thin aluminum sheet which thickness is 120μm, owing to such difficulties that the thin aluminum sheet must be in shape during the processing, and the holes consistent, and taper not too large, and there isn’t too much melts around the orifice. But it can be a good sound-absorbing materials, which can meet the demands to reduce noise level. The pulse width is a crucial factor in precision micro studies.This paper first analyzed the advantages and disadvantages of the femtosecond, micromicrosecond and nanosecond laser processing, choosing the laser processing which is the most suitable for the subject to research. Then, the paper analyzed the nanosecond laser and mechanism of metallic materials, it studied the damage threshold which the laser has made to aluminum at all pulse widths, and the damage threshold at different pulses numbers. Based on those studies, the change laws of it can be found: The narrower the pulse width, the lower the damage threshold. When the pulse width is 520 ns, the single pulse damage threshold of aluminum is 18.8J / cm2; and when the pulse width is 10 ns, the damage threshold is 4.58 J / cm2. By studying the effects which different pulse widths have on drilling, the conclusion can be obtained that narrow pulse width nanosecond laser makes can drill such holes that have the narrow taper, good roundness, small melts at the orifice of the hole and the pore walls, less splash particles around the orifice of the hole.During the studies of the micro-hole drilling of the array, the article first studied the effect which the different parameters of laser devices have on hole drilling, drawing the rules how different parameters affect the hole drilling. Then, by selecting the optimal parameters, a new processing technology of the array is designed. It not only can solve the problem effectively that the aluminium sheet may be deformed in the middle of dense micro-hole machining, but also can machine such holes that have consistency, small taper, good roundness, and almost no melts around the orifice, improving the quality of themicro holes. By doing acoustic detection of aluminum, the theoretical value of absorption coefficient is 0.85, the experiment value is 0.79, the perforated plate can preferably decrease noise.