Quantitative characterization and influence of parameters on surface topography in metal micro-droplet deposition manufacture

Metal micro-droplet deposition manufacture has potential applications and attracts increasing attention in wide areas. By quantitatively describing and predicting the surface topography, the influence of parameters on surface quality could be studied effectively. In present work, a new approach aimed to the characterization of part surface topography was proposed and the evaluation indexes such as arithmetic average height (Ra) and stratification angle (θ) were used to characterize the surface topography. Based on the surface geometrical profile, two prediction models were developed to calculate the evaluation indexes of part surface. Then experiments for fabricating thin wall parts were conducted and the evaluation indexes were measured experimentally. By comparing the experimental values with the predicted results, the mechanism of process parameters affecting surface topography was investigated. The results indicated that the top surface was mainly affected by scan step (Wd) which also could be represented by overlap ratio (μ). While overlap ratio was larger than 25.7%, excessive overlap resulting in poor surface topography occurred and the prediction model was invalid. In another hand, the side surface was mainly affected by offset distance (Wo) which also could be represented by offset ratio (τ). If offset ratio was too large, the ending side would collapse resulting in poor side surface topography and the prediction model would fail to calculate the side surface roughness. The experiment results indicated that collapse would occur while offset ratio was larger than 54.5%. In the last, the surface roughness of a cubic object was measured and the results demonstrated that the method proposed in present work was useful for evaluating surface quality of 3D object.