Scan mode is an important parameter for selective laser sintering (SLS) processing. The improved mode will optimize scan path and improve the precision, strength and fabrication efficiency of a SLS part. A compound scan mode, which combines subarea scan mode and contour scan mode, is proposed. The principle of its hatch (path-planning) algorithm and implementation are presented. To testify the effectiveness of this compound mode compared to that of subarea scan mode, it has been utilized for researches at a SLS machine developed at Huangzhong University of Science and Technique (HUST). The results from the researches indicate that the degree of precision of a SLS part with the compound scan mode is higher than that with subarea one. There is little difference in the tensile strength, flexural strength, shock strength and fabrication efficiency of a SLS part under the compound scan pattern and the subarea scan mode. Therefore, implementation of the compound scan mode is of importance to improve the precision of a SLS part.

Polycarbonate (PC) powder, a common and low-cost amorphous polymer, can be moulded easily by the process of selective laser sintering (SLS). However, the sintered parts cannot be used as functional parts because of their poor mechanical properties. In this article, epoxy resin was applied to improve the mechanical properties of PC SLS parts. Specimens for testing dimensional accuracy, tensibility, flexibility, and impact strength were made by SLS with 75–100mm PC powder. Some of the specimens were posttreated with two types of epoxy resins. Dimensional accuracy and mechanical properties of the specimens were measured. Microstructures of tensile fracture were observed by scanning electron microscopy. The result shows that the mechanical properties of the specimens are reinforced greatly after the epoxy resin has been infiltrated. Extent of the reinforcement depends on curing agents of epoxy resins. For example, with curing agent W, it is increased to 13.82, 8.00, and 3.69 times, respectively, in tensile, flexural, and impact strength and with curing agent Y, it is increased to 19.87, 7.43, and 1.55 times, respectively, in the same properties. The reinforcement in mechanical properties of PC SLS parts can be improved a step further by means of optimizing the epoxy resin system. Therefore, the PC SLS parts reinforced by epoxy resin can be used as functional parts, if the requirement on mechanical properties is not very high.

The properties of alloy parts can be adjusted conveniently if alloy element powders are used for manufacturing alloy parts by indirect selective laser sintering, but no research has been reported on this so far. In this paper several composite powders have been obtained by blending pure Fe, Cu and graphite powders, which have been used to produce green parts by indirect selective laser sintering. Cu infiltrated Fe–Cu–C alloy was manufactured after green parts had been degreased, high temperature sintered and infiltrated. Contents of composite powders, post-processing of green parts, microstructures and mechanical property of alloys were investigated. The results indicate that: Cu and C can diffuse into c-Fe when green parts are being sintered at high temperature; the microstructures of alloy are composed of a large quantity of eutectoid structures mixtures of Fe–C and Fe–Cu at room temperature besides a coarse structure; the eutectoid structure varies regionally owing to the inhomogeneous concentration of Cu and C; the yield strength of Fe–Cu–C sample alloys is. >300MPa and the elongation is, <3%.

The effect of the properties of the polymer materials, such as molecular weight, molten viscosity, crystallization rate and the particle size of the powder, on the quality of selective laser sintering (SLS) parts is researched. The results indicate that the molecular weight affects the quality of the SLS parts through the melting viscosity. SLS parts of higher density can be fabricated with polymer materials of lower melting viscosity. Crystallinity largely affects the precision of the SLS part-shrinkage is more serious with increasing crystallinity. SLS parts sintered with polymer powder materials whose melting peak and crystalline peak differ greatly, have high dimensional precision. The particle size of the powder affects not only the precision but also the density of the SLS part. The appropriate particle size is about 75-100m.