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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℃。
The laser energy density and laser power (P) and scanning speed (V) ratio (P / V) are proportional to SLS shaping at constant scan pitch. In order to study the effect of laser energy density on the density and microstructure of sintered samples, the density of laser sintered samples with different P / V ratio and the same P / V ratio but different P values and V values were studied The surface morphology and microstructure of the sintered samples were analyzed by scanning electron microscopy (SEM). The results showed that the bulk density of sintered samples increased with the increase of P / V value before the P / V value reached 1 W / 37.7 mm.s-1, the surface of the samples became more and more smooth, the number and size of pores With the further increase of P / V, due to the degradation of polystyrene, a large amount of flue gas was produced, the bulk density did not increase basically, but the tendency of descent was likely to appear and the porosity did not decrease obviously. With P / V value equal to 1 W / 32 mm.s-1, with the increase of P and V, the bulk density of sintered samples decreased, the internal porosity increased and the pore size became larger. Considering the service life of the laser and the processing efficiency, the optimum sintering process parameters are laser sintering power 28 W, scanning speed 1120 mm / s, thickness 0.1 mm, scanning distance 0.2 mm and preheating temperature 95 ℃.