Effect of Thermal Deformation on Part Errors in Metal Powder Based Additive Manufacturing Processes

Abstract

In metal additive manufacturing (AM) processes, parts are manufactured in layers by sintering or melting metat or metal altoy powder under the effect of a powerful taser or an electron beam. As the laser/electron beam scans the powder bed, it melts the powder in successive tracks which overlap each other. This overlap, called the hatch overlap, results in a continuous cycle of rapid melting and resolidiflcation of the metat. The metting of the metal from powder to liquid and subsequent sotidification causes anisotropic shrinkage in the layers. The thermat strains caused by the thermat gradients existing between the different layers and between the layers and the substrate leads to considerabte thermat stresses in the part. As a resutt, stress gradients devetop in the different directions of the part which lead to distortion and warpage in AM parts. The deformations due to shrinkage and thermal stresses have a signiflcant effect on the dimensional inaccuracies of the final part. A three-dimensional thermomechanicat finite etement (EE) modet has been devetoped in this paper which calculates the thermat deformation in AM parts based on slice thickness, part orientation, scanning speed, and materiat properties. The EE modet has been vatidated and benchmarked with resutts atready avaitabte in titerature. The thermat deformation modet is then superimposed with a geometric virtuat manufacturing model of' the AM process to catcutate the form and runout errors in AM parts. Einalty, the errors in the criticat features of the AM parts calculated using the combined thermat deformation and geometric modet are corretated with part orientation and stice thickness.

An overview of Direct Laser Deposition for additive manufacturing; Part I: Transport phenomena, modeling and diagnostics

“…Significant temperature gradients in the part can result in thermal deformation and the inheritance of residual stress [178]. This is due to thermal strains being developed between M a n u s c r i p t successive layers due to anisotropic shrinkage in deposition layers.…”

“…This is due to thermal strains being developed between M a n u s c r i p t successive layers due to anisotropic shrinkage in deposition layers. This further leads to stress gradients resulting in part warping and distortion [178]. Patel and Patel numerically demonstrated that the height-wise thermal stress is dominant and that the starting point for each new deposition layer has a strong effect on the intensity and distribution of thermal stress [179].…”

Statistical Predictive Modeling and Compensation of Geometric Deviations of Three-Dimensional Printed Products

“…Therefore, we adopt an alternative model studies in Ref. [8] gi(0,ro(9)) = )Vo + JVo«>s(20) (7) A Bayesian procedure was implemented to draw inferences on all parameters P0,P l ,a,b, and a. We calculated the posterior dis tribution of the parameters by Markov Chain Monte Carlo (MCMC) and summarized the marginal posteriors by taking the mean, median, standard deviation, and 2.5% and 97.5% quantiles of the posterior draws in Table 4.…”

“…Despite these promising features, dimensional accuracy control remains a major bottleneck for the application of 3D printing in direct manufacturing [6][7][8][9]. Shape deviations of AM built prod ucts can be attributed to multiple variation sources.…”

Modeling, Analysis, and Simulation of Paste Freezing in Freeze-Form Extrusion Fabrication of Thin-Wall Parts

“…In some of the recent additive manufacturing research, the effects of interpass idle time [4], heat transfer rate [5], and slice thickness [6] on thermal stresses and part distortions were investigated. However, due to water's high latent heat, the small difference between solidus and ambient temperatures, and the variety of paste materials in the FEF process, the consequence of selected improper process parameters is amplified.…”