Development of an automated laser control system for improving temperature uniformity and controlling component strength in selective laser sintering

Abstract

It has been shown that quality of components built using selective laser sintering (SLS) are strongly affected by the thermal history of the building process. Temperature variations of a few degrees across the powder surface can alter the mechanical properties of components and render them unsuitable for their intended purpose. Therefore, to improve the quality of SLS components and ease their adoption into the marketplace, temperature fluctuation issues must be addressed. Some success has been demonstrated in the past at reducing temperature non-uniformity by improving the heater system that pre-heats the polymer powder prior to sintering with the laser. This paper will cover a complimentary approach of actively controlling laser fluence on the powder surface based on infrared temperature measurements. By controlling the amount of energy input by the laser, a high level of control over the final part temperature can be achieved and uniformity can be improved. This paper will cover development of the feed-forward control system and will present results showing that for constant cross-section specimens, a 45% improvement in ultimate flexural strength standard deviation was achieved.