Research On The Performance In Selective Laser Melting Of Metallic Part

Selective Laser Melting is one of the most potential Rapid Prototyping and Manufacturing technologies. By using a high-energy laser to melt metal powder directly, it can manufacture metal parts which are formed in nearly full density and have high-performance. This technology can manufacture complex structures which are impossible for traditional methods to make or need to assemble multi-components, so it has a Broad application prospect in the fields such as aerospace manufacturing, personalized biomanufacturing and complex mold inserts manufacturing. But influenced by many factors, the precise control of shape and control of the forming part are most difficult. This paper focuses on the surface quality, dimensional accuracy and mechanical properties of SLM forming part; the manufacture of complex molds has also been researched. The main content of research in the paper is as following:(1) Surface quality of the SLMed parts. Through a series of experiments, dimensional characteristic of single melting Road is analyzed with shape factor F evaluating the melting road. Meanwhile the paper also exposes how SLM process parameters and scanning strategies influence the surface roughness of single-channel and single-layer. The results show that with the improvement of the scanning speed, surface roughness of the road is reduced, which is first down then up when laser power increases. Single scan in the same direction has the worst surface quality, while with twice the spacing scan first, then the normal scan, surface roughness is the least. This paper also illustrates how the factors such as manufacturing angle, laser power density and processing thickness influence the surface roughness on the parts’side face. The results show that when manufacturing angle is less than60°, the surface roughness tends to decrease significantly with the increase of the angle; while, when the angle is more than60°, it decreases a little, but not obvious, with the increase of the angle.(2) Dimensional accuracy of SLMed parts. A research in the property of manufacture precision parts has been done. In order to analyze processing errors, a series of0.1-0.45mm thickness parts have been made. The research shows that when the laser beam spot size close to0.1mm, relative error increases with the decreasing of its wall thickness. The relative error of the part which just has a thickness of0.1mm is close to99%. The relative error is just0.1%when the thickness rises to0.4mm. The paper researches how the parameters influence the forming precision on the XY plane and the Z-axis, and error of the parts in different positions of the working plane. Measured in terms of the three-dimensional size and compared with the model, metal parts have a shrinkage in Z-axis direction with a relative error of less than1%. Laser melt powders will form a dense metal layer, due to low density of the powder, thickness of the layer decreases dramatically after the melting. With accumulation of the error, accuracy of the Z axis will be affected to some degree. The higher the density of the power and the lower the thickness of power, the smaller this impact will be.(3) Density of SLMed parts. This paper analyzes how the SLMed process parameters influence the density through Taguchi analysis method. The results show that, among the three factors which influence SLMed forming density, forming speed has the greatest impact, accounting for43.98%; laser power is next, for34.61%; the impacts of scan spacing is very small, just about19.81%. So the forming speed is much more important than scanning spacing, which should be optimized in the first place. The paper researches the change of the density in different areas, indicating that density is different in different area, the center position of the plane being with a higher density.(4) Mechanical properties of SLMed parts. This paper researches the variation of the extension properties of different parts by manufacturing the parts of the different tilt angles. The results show that lap joints of melting road, also called boundary of welding pool is the obvious weak performance area, which is the important factor to reduce the elongation of the SLM Part; the space topology of the boundary brings out a significant anisotropy of the parts’tensile properties. By using heat treatment to eliminate the boundary pool, the extended performance will be improved and anisotropy will be reduced. This paper analyzes how powder particle size distribution influences the formability. The results show that an average smaller particle size of26.36μm powder has a better performance and the higher bulk density of the powder (0.56) has a high density about99.1%. (5)Preliminary application of manufacturing mold by SLM. This paper researches how the SLM technology apply to the manufacture of complex parts by manufacturing custom cooling channels for molds. The test proves that both cooling rate and cooling uniformity are better than traditional ones.All in all, this paper has focused on the research of the surface roughness, dimensional accuracy and mechanical properties of SLM forming part, and provided guidance for manufacturing practical SLM parts. It also explores the mold application and throws some light on the market of SLM manufacturing parts.