当扫描间距一定时,选区激光烧结(SLS)成型的激光能量密度和激光功率(P)与扫描速度(V)的比值(P/V)成正比。为了研究激光能量密度对烧结试件致密度和显微结构的影响,分别对不同P/V比值及相同P/V比值但不同P值和V值条件下激光烧结试件的致密度进行了研究,并利用扫描电镜(SEM)分析研究了烧结试件的表面形貌和显微结构的变化。研究发现,在P/V值达到1 W/37.7 mm·s-1以前时,烧结试件的体积密度随着P/V值的增加而提高,试件表面越来越光滑,气孔数量及尺寸减小；随着P/V值进一步地提高,由于聚苯乙烯的降解,产生了大量的烟气,体积密度基本上没有提高,反而有可能会出现下降的趋势,气孔未见明显减少；在P/V值等于1 W/32 mm·s-1时,随着P和V值的同时增加,烧结试件的体积密度有下降的趋势,内部气孔增多,气孔尺寸变大。综合考虑激光器使用寿命及加工效率等因素,较佳的成型工艺参数选择为激光烧结功率28 W,扫描速度1120 mm/s,铺粉厚度0.1 mm,扫描间距0.2 mm,预热温度95 ℃。

Based on the character of the selective laser sintering (SLS) processing, when the scan space is a constant, the laser energy density varies directly as the ratio of laser power to scan speed, i.e. the value of P/V. In order to study the effect of the laser energy density on the densities and microstructures of laser sintered specimens, effects of different values of P/V and a fixed value of P/V with different P and V on the densification behavior and the morphology of the laser sintered specimens were studied by means of scanning electron microscopy (SEM), respectively. It was found that the density of the sintered specimens increased with the value of P/V increasing until the value of P/V had been reached 1 W/37.7 mm·s-1, and the pore and the average size of the pore decreased. When the value of P/V was further increased, smoke was observed, which suggested degradation of polystyrene (PS) particles, and the density did not increase and the pore did not decrease. However, when the value of P/V was fixed at 1 W/32 mm·s-1 with the simultaneous increase of P and V, the density of laser sintered specimens declined apparently. Furthermore, more and more pores appeared with the increase of the average size of pores. Based on protecting the laser irradiation and improving the machining efficiency, the optimal processing parameters were adopted, the laser power is 28 W, the scan speed is 1120 mm/s, the thickness of the powder is 0.1 mm, the laser scan space is 0.2 mm, and the starting temperature of the powder bed is 95 ℃.